Evaluation of dosimetric effect caused by slowing with multi-leaf collimator (MLC) leaves for volumetric modulated arc therapy (VMAT)

PubMed Central

Wang, Iris Z.; Kumaraswamy, Lalith K.; Podgorsak, Matthew B.

2016-01-01

Background This study is to report 1) the sensitivity of intensity modulated radiation therapy (IMRT) QA method for clinical volumetric modulated arc therapy (VMAT) plans with multi-leaf collimator (MLC) leaf errors that will not trigger MLC interlock during beam delivery; 2) the effect of non-beam-hold MLC leaf errors on the quality of VMAT plan dose delivery. Materials and methods. Eleven VMAT plans were selected and modified using an in-house developed software. For each control point of a VMAT arc, MLC leaves with the highest speed (1.87-1.95 cm/s) were set to move at the maximal allowable speed (2.3 cm/s), which resulted in a leaf position difference of less than 2 mm. The modified plans were considered as ‘standard’ plans, and the original plans were treated as the ‘slowing MLC’ plans for simulating ‘standard’ plans with leaves moving at relatively lower speed. The measurement of each ‘slowing MLC’ plan using MapCHECK®2 was compared with calculated planar dose of the ‘standard’ plan with respect to absolute dose Van Dyk distance-to-agreement (DTA) comparisons using 3%/3 mm and 2%/2 mm criteria. Results All ‘slowing MLC’ plans passed the 90% pass rate threshold using 3%/3 mm criteria while one brain and three anal VMAT cases were below 90% with 2%/2 mm criteria. For ten out of eleven cases, DVH comparisons between ‘standard’ and ‘slowing MLC’ plans demonstrated minimal dosimetric changes in targets and organs-at-risk. Conclusions For highly modulated VMAT plans, pass rate threshold (90%) using 3%/3mm criteria is not sensitive in detecting MLC leaf errors that will not trigger the MLC leaf interlock. However, the consequential effects of non-beam hold MLC errors on target and OAR doses are negligible, which supports the reliability of current patient-specific IMRT quality assurance (QA) method for VMAT plans. PMID:27069458

The influence of plan modulation on the interplay effect in VMAT liver SBRT treatments.

PubMed

Hubley, Emily; Pierce, Greg

2017-08-01

Volumetric modulated arc therapy (VMAT) uses multileaf collimator (MLC) leaves, gantry speed, and dose rate to modulate beam fluence, producing the highly conformal doses required for liver radiotherapy. When targets that move with respiration are treated with a dynamic fluence, there exists the possibility for interplay between the target and leaf motions. This study employs a novel motion simulation technique to determine if VMAT liver SBRT plans with an increase in MLC leaf modulation are more susceptible to dosimetric differences in the GTV due to interplay effects. For ten liver SBRT patients, two VMAT plans with different amounts of MLC leaf modulation were created. Motion was simulated using a random starting point in the respiratory cycle for each fraction. To isolate the interplay effect, motion was also simulated using four specific starting points in the respiratory cycle. The dosimetric differences caused by different starting points were examined by subtracting resultant dose distributions from each other. When motion was simulated using random starting points for each fraction, or with specific starting points, there were significantly more dose differences in the GTV (maximum 100cGy) for more highly modulated plans, but the overall plan quality was not adversely affected. Plans with more MLC leaf modulation are more susceptible to interplay effects, but dose differences in the GTV are clinically negligible in magnitude. Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

SU-E-T-534: Dosimetric Effect of Multileaf Collimator Leaf Width On Volumetric Modulated Arc Stereotactic Radiotherapy for Spine Tumors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amoush, A; Djemil, T; Subedi, L

2014-06-01

Purpose: To study the dosimetric impact of MLC leaf width in patients treated with Volumetric Modulated Arc Therapy (VMAT) for spine Stereotactic Body radiation Therapy (SBRT). Methods: Twelve spine SBRT patients were retrospectively selected for this study. The patients were treated with IMRT following the RTOG-0631 of spine metastasis. The prescription dose was 16 Gy in one fraction to 90% of the target volume (V16 > 90%). The maximum spinal cord dose of 14 Gy and 10% of the cord receiving < 10 Gy (V10) were set as dose constraints. For purpose of this study, three dual arc VMAT plansmore » were created for each patient using three different MLC leaf widths: 2.5 mm, 4mm, and 5mm. The compliance to RTOG 0631, conformal index (CI), dose gradient index (DGI), and number of monitor units (MUs) were compared. Results: The average V16 of the target was 91.91±1.36%, 93.73±2.38%, and 92.25±2.49% for 2.5 mm, 4 mm, and 5 mm leaf widths, respectively (p=0.39). Accordingly, the average CI was 1.36±0.39, 1.36±0.34, and 1.41±0.3 (0.96), respectively. The average DGI was 0.24 ± 0.05, 0.22 ± 0.05, and 0.23 ± 0.04, respectively (p=0.86). The average spinal cord maximum dose was 12.10 ± 0.88 Gy, 12.52 ± 1.15 Gy, and 12.05 ± 1.12 (p=0.75) and V10 was 2.69 ± 1.71 cc, 5.43 ± 2.16 cc, and 3.71 ± 2.34 cc (p=0.15) for 2.5 mm, 4 mm, and 5 mm leaf widths, respectively. According, the average number of MUs was 4255 ± 431 MU, 5049 ± 1036 MU, and 4231 ± 580 MU respectively (p=0.17). Conclusion: The use of 2.5 mm, 4 mm, and 5 mm MLCs achieved similar VMAT plan quality as recommended by RTOG-0631. The dosimetric parameters were also comparable for the three MLCs.« less

The dosimetric impact of inversely optimized arc radiotherapy plan modulation for real-time dynamic MLC tracking delivery.

PubMed

Falk, Marianne; Larsson, Tobias; Keall, Paul; Chul Cho, Byung; Aznar, Marianne; Korreman, Stine; Poulsen, Per; Munck Af Rosenschold, Per

2012-03-01

Real-time dynamic multileaf collimator (MLC) tracking for management of intrafraction tumor motion can be challenging for highly modulated beams, as the leaves need to travel far to adjust for target motion perpendicular to the leaf travel direction. The plan modulation can be reduced by using a leaf position constraint (LPC) that reduces the difference in the position of adjacent MLC leaves in the plan. The purpose of this study was to investigate the impact of the LPC on the quality of inversely optimized arc radiotherapy plans and the effect of the MLC motion pattern on the dosimetric accuracy of MLC tracking delivery. Specifically, the possibility of predicting the accuracy of MLC tracking delivery based on the plan modulation was investigated. Inversely optimized arc radiotherapy plans were created on CT-data of three lung cancer patients. For each case, five plans with a single 358° arc were generated with LPC priorities of 0 (no LPC), 0.25, 0.5, 0.75, and 1 (highest possible LPC), respectively. All the plans had a prescribed dose of 2 Gy × 30, used 6 MV, a maximum dose rate of 600 MU/min and a collimator angle of 45° or 315°. To quantify the plan modulation, an average adjacent leaf distance (ALD) was calculated by averaging the mean adjacent leaf distance for each control point. The linear relationship between the plan quality [i.e., the calculated dose distributions and the number of monitor units (MU)] and the LPC was investigated, and the linear regression coefficient as well as a two tailed confidence level of 95% was used in the evaluation. The effect of the plan modulation on the performance of MLC tracking was tested by delivering the plans to a cylindrical diode array phantom moving with sinusoidal motion in the superior-inferior direction with a peak-to-peak displacement of 2 cm and a cycle time of 6 s. The delivery was adjusted to the target motion using MLC tracking, guided in real-time by an infrared optical system. The dosimetric results were evaluated using gamma index evaluation with static target measurements as reference. The plan quality parameters did not depend significantly on the LPC (p ≥ 0.066), whereas the ALD depended significantly on the LPC (p < 0.001). The gamma index failure rate depended significantly on the ALD, weighted to the percentage of the beam delivered in each control point of the plan (ALD(w)) when MLC tracking was used (p < 0.001), but not for delivery without MLC tracking (p ≥ 0.342). The gamma index failure rate with the criteria of 2% and 2 mm was decreased from > 33.9% without MLC tracking to <31.4% (LPC 0) and <2.2% (LPC 1) with MLC tracking. The results indicate that the dosimetric robustness of MLC tracking delivery of an inversely optimized arc radiotherapy plan can be improved by incorporating leaf position constraints in the objective function without otherwise affecting the plan quality. The dosimetric robustness may be estimated prior to delivery by evaluating the ALD(w) of the plan.

SU-F-T-481: Physics Evaluation of a Newly Released InCise™ Multileaf Collimator for CyberKnife M6™ System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, L; Chin, E; Lo, A

2016-06-15

Purpose: This work reports the results of the physics evaluation of a newly released InCise™2 Multileaf Collimator (MLC) installed in our institution. Methods: Beam property data was measured with unshielded diode and EBT2 films. The measurements included MLC leaf transmission, beam profiles, output factors and tissue-phantom ratios. MLC performance was evaluated for one month after commissioning. Weekly Garden Fence tests were performed for leaf / bank positioning in standard (A/P) and clinically relevant non-standard positions, before and after MLC driving exercises of 10+ minutes. Daily Picket Fence test and AQA test, End-to-End tests and dosimetric quality assurance were performed tomore » evaluate the overall system performance. Results: All measurements including beam energy, flatness and symmetry, were within manufacture specifications. Leaf transmission was 0.4% <0.5% specification. The values of output factors ranged from 0.825 (7.6 mm × 7.5 mm) to 1.026 (115.0 mm × 100.1 mm). Average beam penumbra at 10 cm depth ranged from 2.7mm/2.7mm(7.6 mm × 7.5 mm) to 6.0 mm/6.2mm(84.6 mm × 84.7 mm). Slight penumbra difference (<10% from average penumbra for fields >20 mm) was observed in the direction perpendicular to leaf motion due to the tilting of the leaf housing. Mean leaf position offsets was −0.08±0.07mm and −0.13 ± 0.08 for X1 and X2 leaf banks in 13 Garden Fence tests. No significant difference on average leaf positioning offsets was observed between different leaf orientations and before/after MLC driving exercises. Six End-to-End tests showed 0.43±0.23mm overall targeting accuracy. Picket-Fence and AQA showed stable performance of MLC during the test period. Dosimetric point dose measurements for test cases agreed with calculation within 3%. All film measurements on relative dose had Gamma (2%, 2mm) passing rate of >95%. Conclusion: The Incise™2 MLC for CyberKnife M6™ was proven to be accurate and reliable, and it is currently in clinical use. Stanford was one of the physics evaluation sites for the newly released InCise 2 MLC for Accuray Inc.« less

Dosimetric effect of multileaf collimator leaf width on volumetric modulated arc stereotactic radiotherapy for spine tumors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amoush, Ahmad, E-mail: aamoush@augusta.edu; Cleveland Clinic, 9500 Euclid Ave., Cleveland, OH 44195; Long, Huang

This work aimed to study the dosimetric effect of multileaf collimator (MLC) leaf widths in treatment plans for patients receiving volumetric modulated arc therapy (VMAT) for spine stereotactic body radiation therapy (SBRT). Thirteen patients treated with spine SBRT were retrospectively selected for this study. The patients were treated following the protocol of the Radiation Therapy Oncology Group 0631 (RTOG 0631) for spine metastasis. The prescription dose was 16 Gy in 1 fraction to 90% of the target volume (V16 > 90%). The maximum spinal cord dose of 14 Gy and 10% of the spinal cord receiving < 10 Gy (V10) were the acceptable tolerance doses. For themore » purpose of this study, 2 dual-arc VMAT plans were created for each patient using 3 different MLC leaf widths: 2.5 mm, 4 mm, and 5 mm. The compliance with the RTOG 0631 protocol, conformity index (CI), dose gradient index (DGI), and number of monitor units (MUs) were compared. The average V16Gy of the targets was 91.8 ± 1.2%, 92.2 ± 2.1%, and 91.7 ± 2.3% for 2.5-mm, 4-mm, and 5-mm leaf widths, respectively (p = 0.78). Accordingly, the average CI was 1.45 ± 0.4, 1.47 ± 0.29, and 1.47 ± 0.31 (p = 0.98), respectively. The average DGI was 0.22 ± 0.04, 0.20 ± 0.06, and 0.22 ± 0.05, respectively (p = 0.77). The average maximum dose to the spinal cord was 12.45 ± 1.0 Gy, 12.80 ± 1.0 Gy, and 12.48 ± 1.1 (p = 0.62) and V10% of the spinal cord was 3.6 ± 2.1%, 5.6 ± 2.8%, and 5.5 ± 3.0% (p = 0.11) for 2.5-mm, 4-mm, and 5-mm leaf widths, respectively. Accordingly, the average number of MUs was 4341 ± 500 MU, 5019 ± 834 MU, and 4606 ± 691 MU, respectively (p = 0.053). The use of 2.5-mm, 4-mm, and 5-mm MLCs achieved similar VMAT plan quality as recommended by the RTOG 0631. The dosimetric parameters were also comparable for the 3 MLCs. In general, any of these leaf widths can be used for spine SBRT using VMAT.« less

SU-E-P-32: Adapting An MMLC to a Conventional Linac to Perform Stereotactic Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Emam, I; Hosini, M

2015-06-15

Purpose: Micro-MLCs minimizes beam scalloping effects caused by conventional-MLCs and facilitates conformal dynamic treatment delivery. But their effect on dosimetric parameters require careful investigations. Physical and dosimetric parameters and Linac mechanical stability with mMLC (net weight 30 Kg) attached to the gantry are to be investigated. Moreover, output study along with recommended jaws offsets are studied. Adaptation of an mMLC to our 16-years old conventional Linac is investigated in this work Methods: BrainLab mMLC (m3) mounted in a detachable chassis to the Philips SL-15 Linac (30kg). Gantry and collimator spoke shots measurements are made using a calibrated film in amore » solid phantom and compared with pin-point measurements. Leaf penumbra, transmission, leakage between the leaves, percentage depth dose (PDD) are measured using IBA pin-point ion chamber at 6 and 10 MV. For output measurements (using brass build-up cap), jaws are modified continuously regarding to m3-fields while output factor are compared with fixed jaws situation, while the mMLC leaf configuration is modified for different m3-fields Results: Mean transmission through leaves is 1.9±0.1% and mean leakage between leaves is 2.8±0.15%. Between opposing leaves abutting along the central beam-axis mean transmission is 15±3%, but it is reduced to 4.5±0.6% by moving the abutment position 4.5cm off-axis. The penumbra was sharper for m3 -fields than jaws-fields (maximum difference is 1.51±0.2%). m3-fields PDD show ∼3% variation from those of jaws-fields. m3-fields output factors show large variations (<4%) from Jaws defined fields. Output for m3-rectangular fields show slight variation in case of leaf-end&leaf-side as well as X-jaw&Y-jaw exchange. Circular m3-fields output factors shows close agreement with their corresponding square jaws-defined fields using 2mm Jaws offsets, If jaws are retracted to m3 limits, differences become <5%. Conclusion: BrainLab m3 is successfully adapted to our 16 old Philips-SL-15 Linac. Dosimetric properties should be taken into account for treatment planning considerations.« less

Direct aperture optimization: a turnkey solution for step-and-shoot IMRT.

PubMed

Shepard, D M; Earl, M A; Li, X A; Naqvi, S; Yu, C

2002-06-01

IMRT treatment plans for step-and-shoot delivery have traditionally been produced through the optimization of intensity distributions (or maps) for each beam angle. The optimization step is followed by the application of a leaf-sequencing algorithm that translates each intensity map into a set of deliverable aperture shapes. In this article, we introduce an automated planning system in which we bypass the traditional intensity optimization, and instead directly optimize the shapes and the weights of the apertures. We call this approach "direct aperture optimization." This technique allows the user to specify the maximum number of apertures per beam direction, and hence provides significant control over the complexity of the treatment delivery. This is possible because the machine dependent delivery constraints imposed by the MLC are enforced within the aperture optimization algorithm rather than in a separate leaf-sequencing step. The leaf settings and the aperture intensities are optimized simultaneously using a simulated annealing algorithm. We have tested direct aperture optimization on a variety of patient cases using the EGS4/BEAM Monte Carlo package for our dose calculation engine. The results demonstrate that direct aperture optimization can produce highly conformal step-and-shoot treatment plans using only three to five apertures per beam direction. As compared with traditional optimization strategies, our studies demonstrate that direct aperture optimization can result in a significant reduction in both the number of beam segments and the number of monitor units. Direct aperture optimization therefore produces highly efficient treatment deliveries that maintain the full dosimetric benefits of IMRT.

Investigation of pulsed IMRT and VMAT for re-irradiation treatments: dosimetric and delivery feasibilities

NASA Astrophysics Data System (ADS)

Lin, Mu-Han; Price, Robert A., Jr.; Li, Jinsheng; Kang, Shengwei; Li, Jie; Ma, C.-M.

2013-11-01

Many tumor cells demonstrate hyperradiosensitivity at doses below ˜50 cGy. Together with the increased normal tissue repair under low dose rate, the pulsed low dose rate radiotherapy (PLDR), which separates a daily fractional dose of 200 cGy into 10 pulses with 3 min interval between pulses (˜20 cGy/pulse and effective dose rate 6.7 cGy min-1), potentially reduces late normal tissue toxicity while still providing significant tumor control for re-irradiation treatments. This work investigates the dosimetric and technical feasibilities of intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT)-based PLDR treatments using Varian Linacs. Twenty one cases (12 real re-irradiation cases) including treatment sites of pancreas, prostate, pelvis, lung, head-and-neck, and breast were recruited for this study. The lowest machine operation dose rate (100 MU min-1) was employed in the plan delivery. Ten-field step-and-shoot IMRT and dual-arc VMAT plans were generated using the Eclipse TPS with routine planning strategies. The dual-arc plans were delivered five times to achieve a 200 cGy daily dose (˜20 cGy arc-1). The resulting plan quality was evaluated according to the heterogeneity and conformity indexes (HI and CI) of the planning target volume (PTV). The dosimetric feasibility of retaining the hyperradiosensitivity for PLDR was assessed based on the minimum and maximum dose in the target volume from each pulse. The delivery accuracy of VMAT and IMRT at the 100 MU min-1 machine operation dose rate was verified using a 2D diode array and ion chamber measurements. The delivery reproducibility was further investigated by analyzing the Dynalog files of repeated deliveries. A comparable plan quality was achieved by the IMRT (CI 1.10-1.38 HI 1.04-1.10) and the VMAT (CI 1.08-1.26 HI 1.05-1.10) techniques. The minimum/maximum PTV dose per pulse is 7.9 ± 5.1 cGy/33.7 ± 6.9 cGy for the IMRT and 12.3 ± 4.1 cGy/29.2 ± 4.7 cGy for the VMAT. Six out of the 186 IMRT pulses (fields) were found to exceed 50 cGy maximum PTV dose per pulse while the maximum PTV dose per pulse was within 40 cGy for all the VMAT pulses (arcs). However, for VMAT plans, the dosimetric quality of the entire treatment plan was less superior for the breast cases and large irregular targets. The gamma passing rates for both techniques at the 100 MU min-1 dose rate were at least 94.1% (3%/3 mm) and the point dose measurements agreed with the planned values to within 2.2%. The average root mean square error of the leaf position was 0.93 ± 0.83 mm for IMRT and 0.53 ± 0.48 mm for VMAT based on the Dynalog file analysis. The RMS error of the leaf position was nearly identical for the repeated deliveries of the same plans. In general, both techniques are feasible for PLDR treatments. VMAT was more advantageous for PLDR with more uniform target dose per pulse, especially for centrally located tumors. However, for large, irregular and/or peripheral tumors, IMRT could produce more favorable PLDR plans. By taking the biological benefit of PLDR delivery and the dosimetric benefit of IMRT and VMAT, the proposed methods have a great potential for those previously-irradiated recurrent patients.

SU-E-T-306: Dosimetric Comparison of Leaf with Or Without Interdigitation in Multiple Brain Metastasis VMAT Treatment Planning

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

Purpose: To evaluate the effects of leaf with or without interdigitation in multiple brain metastasis volumetric modulated arc therapy (VMAT) plans. Methods: Twenty patients with 2 to 6 brain metastases of our hospital were retrospectively studied to be planned with dual arc VMAT using Monaco 3.3 TPS on the Elekta Synergy linear accelerator. The prescription dose of PTV was 60Gy/30 fractions. Two plans with or without leaf interdigitation were designed. The homogeneity index (HI), conformity index (CI), dose volume histograms (DVHs), monitor unit (MU), treatment time (T), the segments, the dose coverage of the target, were all evaluated. Results: Themore » plans with leaf interdigitation could achieve better CI (p<0.05) than without leaf interdigitation, while no significant difference were found in HI (p> 0.05) and the dose coverage of the target (p> 0.05).The MU,T, and the segments of the plan with leaf interdigitation were more than the plan without leaf interdigitation (p<0.05). There was no significant difference found in radiation dose of spinal cord, lenses and parotids, while the maximum dose of brain stem of leaf without interdigitation was higher than leaf with interdigitation (p< 0.05). It was worth noting that the areas of low dose regions with leaf interdigitation plan were much less than the without leaf interdigitation plan in the doublication planes (p< 0.05). Conclusion: This study shows that leaf with interdigitation has some advantages than leaf without interdigitation in multiple brain metastasis VMAT plans although the clinical relevance remains to be proven.« less

SU-F-T-313: Clinical Results of a New Customer Acceptance Test for Elekta VMAT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rusk, B; Fontenot, J

Purpose: To report the results of a customer acceptance test (CAT) for VMAT treatments for two matched Elekta linear accelerators. Methods: The CAT tests were performed on two clinically matched Elekta linear accelerators equipped with a 160-leaf MLC. Functional tests included performance checks of the control system during dynamic movements of the diaphragms, MLC, and gantry. Dosimetric tests included MLC picket fence tests at static and variable dose rates and a diaphragm alignment test, all performed using the on-board EPID. Additionally, beam symmetry during arc delivery was measured at the four cardinal angles for high and low dose rate modesmore » using a 2D detector array. Results of the dosimetric tests were analyzed using the VMAT CAT analysis tool. Results: Linear accelerator 1 (LN1) met all stated CAT tolerances. Linear accelerator 2 (LN2) passed the geometric, beam symmetry, and MLC position error tests but failed the relative dose average test for the diaphragm abutment and all three picket fence fields. Though peak doses in the abutment regions were consistent, the average dose was below the stated tolerance corresponding to a leaf junction that was too narrow. Despite this, no significant differences in patient specific VMAT quality assurance measured were observed between the accelerators and both passed monthly MLC quality assurance performed with the Hancock test. Conclusion: Results from the CAT showed LN2 with relative dose averages in the abutment regions of the diaphragm and MLC tests outside the tolerances resulting from differences in leaf gap distances. Tolerances of the dose average tests from the CAT may be small enough to detect MLC errors which do not significantly affect patient QA or the routine MLC tests.« less

SU-E-T-430: Modeling MLC Leaf End in 2D for Sliding Window IMRT and Arc Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liang, X; Zhu, T

2014-06-01

Purpose: To develop a 2D geometric model for MLC accounting for leaf end dose leakage for dynamic IMRT and Rapidarc therapy. Methods: Leaf-end dose leakage is one of the problems for MLC dose calculation and modeling. Dosimetric leaf gap used to model the MLC and to count for leakage in dose calculation, but may not be accurate for smaller leaf gaps. We propose another geometric modeling method to compensate for the MLC round-shape leaf ends dose leakage, and improve the accuracy of dose calculation and dose verification. A triangular function is used to geometrically model the MLC leaf end leakagemore » in the leaf motion direction, and a step function is used in the perpendicular direction. Dose measurements with different leaf gap, different window width, and different window height were conducted, and the results were used to fit the analytical model to get the model parameters. Results: Analytical models have been obtained for stop-and-shoot and dynamic modes for MLC motion. Parameters a=0.4, lw'=5.0 mm for 6X and a=0.54, lw'=4.1 mm for 15x were obtained from the fitting process. The proposed MLC leaf end model improves the dose profile at the two ends of the sliding window opening. This improvement is especially significant for smaller sliding window openings, which are commonly used for highly modulated IMRT plans and arc therapy plans. Conclusion: This work models the MLC round leaf end shape and movement pattern for IMRT dose calculation. The theory, as well as the results in this work provides a useful tool for photon beam IMRT dose calculation and verification.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chengqiang, L; Yin, Y; Chen, L

Purpose: To investigate the impact of MLC position errors on simultaneous integrated boost intensity-modulated radiotherapy (SIB-IMRT) for patients with nasopharyngeal carcinoma. Methods: To compare the dosimetric differences between the simulated plans and the clinical plans, ten patients with locally advanced NPC treated with SIB-IMRT were enrolled in this study. All plans were calculated with an inverse planning system (Pinnacle3, Philips Medical System{sub )}. Random errors −2mm to 2mm{sub )},shift errors{sub (} 2mm,1mm and 0.5mm) and systematic extension/ contraction errors (±2mm, ±1mm and ±0.5mm) of the MLC leaf position were introduced respectively into the original plans to create the simulated plans.more » Dosimetry factors were compared between the original and the simulated plans. Results: The dosimetric impact of the random and system shift errors of MLC position was insignificant within 2mm, the maximum changes in D95% of PGTV,PTV1,PTV2 were-0.92±0.51%,1.00±0.24% and 0.62±0.17%, the maximum changes in the D0.1cc of spinal cord and brainstem were 1.90±2.80% and −1.78±1.42%, the maximum changes in the Dmean of parotids were1.36±1.23% and −2.25±2.04%.However,the impact of MLC extension or contraction errors was found significant. For 2mm leaf extension errors, the average changes in D95% of PGTV,PTV1,PTV2 were 4.31±0.67%,4.29±0.65% and 4.79±0.82%, the averaged value of the D0.1cc to spinal cord and brainstem were increased by 7.39±5.25% and 6.32±2.28%,the averaged value of the mean dose to left and right parotid were increased by 12.75±2.02%,13.39±2.17% respectively. Conclusion: The dosimetric effect was insignificant for random MLC leaf position errors up to 2mm. There was a high sensitivity to dose distribution for MLC extension or contraction errors.We should pay attention to the anatomic changes in target organs and anatomical structures during the course,individual radiotherapy was recommended to ensure adaptive doses.« less

Plan averaging for multicriteria navigation of sliding window IMRT and VMAT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Craft, David, E-mail: dcraft@partners.org; Papp, Dávid; Unkelbach, Jan

2014-02-15

Purpose: To describe a method for combining sliding window plans [intensity modulated radiation therapy (IMRT) or volumetric modulated arc therapy (VMAT)] for use in treatment plan averaging, which is needed for Pareto surface navigation based multicriteria treatment planning. Methods: The authors show that by taking an appropriately defined average of leaf trajectories of sliding window plans, the authors obtain a sliding window plan whose fluence map is the exact average of the fluence maps corresponding to the initial plans. In the case of static-beam IMRT, this also implies that the dose distribution of the averaged plan is the exact dosimetricmore » average of the initial plans. In VMAT delivery, the dose distribution of the averaged plan is a close approximation of the dosimetric average of the initial plans. Results: The authors demonstrate the method on three Pareto optimal VMAT plans created for a demanding paraspinal case, where the tumor surrounds the spinal cord. The results show that the leaf averaged plans yield dose distributions that approximate the dosimetric averages of the precomputed Pareto optimal plans well. Conclusions: The proposed method enables the navigation of deliverable Pareto optimal plans directly, i.e., interactive multicriteria exploration of deliverable sliding window IMRT and VMAT plans, eliminating the need for a sequencing step after navigation and hence the dose degradation that is caused by such a sequencing step.« less

Architectural mutation and leaf form, for the palmate series.

PubMed

White, D A

2005-07-21

Palmate leaf form occurs in both the ferns and angiosperms. The palmate leaf form, and its variants, is present in distantly separated clades within both ferns and angiosperms. There tend not to be intermediate forms which link these palmate leaves to other leaf forms within the taxonomic groups in question. The recurrence of homoplasious leaf forms in separate taxonomic groups could be a consequence of the algorithmic like mode of leaf growth. Leaves develop through the reiteration of modular units. It is probable that the homoplasious leaf forms in different taxa are derived independently through re-combinations of the parameters in the basic leaf form development algorithm.

Clinical impact of dosimetric changes for volumetric modulated arc therapy in log file-based patient dose calculations.

PubMed

Katsuta, Yoshiyuki; Kadoya, Noriyuki; Fujita, Yukio; Shimizu, Eiji; Matsunaga, Kenichi; Matsushita, Haruo; Majima, Kazuhiro; Jingu, Keiichi

2017-10-01

A log file-based method cannot detect dosimetric changes due to linac component miscalibration because log files are insensitive to miscalibration. Herein, clinical impacts of dosimetric changes on a log file-based method were determined. Five head-and-neck and five prostate plans were applied. Miscalibration-simulated log files were generated by inducing a linac component miscalibration into the log file. Miscalibration magnitudes for leaf, gantry, and collimator at the general tolerance level were ±0.5mm, ±1°, and ±1°, respectively, and at a tighter tolerance level achievable on current linac were ±0.3mm, ±0.5°, and ±0.5°, respectively. Re-calculations were performed on patient anatomy using log file data. Changes in tumor control probability/normal tissue complication probability from treatment planning system dose to re-calculated dose at the general tolerance level was 1.8% on planning target volume (PTV) and 2.4% on organs at risk (OARs) in both plans. These changes at the tighter tolerance level were improved to 1.0% on PTV and to 1.5% on OARs, with a statistically significant difference. We determined the clinical impacts of dosimetric changes on a log file-based method using a general tolerance level and a tighter tolerance level for linac miscalibration and found that a tighter tolerance level significantly improved the accuracy of the log file-based method. Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Modeling canopy-level productivity: is the "big-leaf" simplification acceptable?

NASA Astrophysics Data System (ADS)

Sprintsin, M.; Chen, J. M.

2009-05-01

The "big-leaf" approach to calculating the carbon balance of plant canopies assumes that canopy carbon fluxes have the same relative responses to the environment as any single unshaded leaf in the upper canopy. Widely used light use efficiency models are essentially simplified versions of the big-leaf model. Despite its wide acceptance, subsequent developments in the modeling of leaf photosynthesis and measurements of canopy physiology have brought into question the assumptions behind this approach showing that big leaf approximation is inadequate for simulating canopy photosynthesis because of the additional leaf internal control on carbon assimilation and because of the non-linear response of photosynthesis on leaf nitrogen and absorbed light, and changes in leaf microenvironment with canopy depth. To avoid this problem a sunlit/shaded leaf separation approach, within which the vegetation is treated as two big leaves under different illumination conditions, is gradually replacing the "big-leaf" strategy, for applications at local and regional scales. Such separation is now widely accepted as a more accurate and physiologically based approach for modeling canopy photosynthesis. Here we compare both strategies for Gross Primary Production (GPP) modeling using the Boreal Ecosystem Productivity Simulator (BEPS) at local (tower footprint) scale for different land cover types spread over North America: two broadleaf forests (Harvard, Massachusetts and Missouri Ozark, Missouri); two coniferous forests (Howland, Maine and Old Black Spruce, Saskatchewan); Lost Creek shrubland site (Wisconsin) and Mer Bleue petland (Ontario). BEPS calculates carbon fixation by scaling Farquhar's leaf biochemical model up to canopy level with stomatal conductance estimated by a modified version of the Ball-Woodrow-Berry model. The "big-leaf" approach was parameterized using derived leaf level parameters scaled up to canopy level by means of Leaf Area Index. The influence of sunlit/shaded leaf separation on GPP prediction was evaluated accounting for the degree of the deviation of 3-dimensional leaf spatial distribution from the random case. More specifically, we compared and evaluated the behavior of both models showing the advantages of sunlit/shaded leaf separation strategy over a simplified big-leaf approach. Keywords: canopy photosynthesis, leaf area index, clumping index, remote sensing.

Development and validation of a BEAMnrc component module for a miniature multileaf collimator.

PubMed

Doerner, E; Hartmann, G H

2012-05-21

A new component module (CM) named mini multileaf collimator (mMLC) was developed for the Monte Carlo code BEAMnrc. It models the geometry of the add-on miniature multileaf collimator ModuLeaf (MRC Systems GmbH, Heidelberg, Germany, now part of Siemens, Erlangen, Germany). The new CM is partly based on the existing CM called DYNVMLC. The development was performed using a modified EGSnrc platform which enables us to work in the Microsoft Visual Studio environment. In order to validate the new CM, the PRIMUS linac with 6 MV x-rays (Siemens OCS, Concord, CA, USA) equipped with the ModuLeaf mMLC was modelled. Validation was performed by two methods: (a) a ray-tracing method to check the correct geometry of the multileaf collimator (MLC) and (b) a comparison of calculated and measured results of the following dosimetrical parameters: output factors, dose profiles, field edge position penumbra, MLC interleaf leakage and transmission values. Excellent agreement was found for all parameters. It was, in particular, found that the relationship between leaf position and field edge depending on the shape of the leaf ends can be investigated with a higher accuracy by this new CM than by measurements demonstrating the usefulness of the new CM.

Development and validation of a BEAMnrc component module for a miniature multileaf collimator

NASA Astrophysics Data System (ADS)

Doerner, E.; Hartmann, G. H.

2012-05-01

A new component module (CM) named mini multileaf collimator (mMLC) was developed for the Monte Carlo code BEAMnrc. It models the geometry of the add-on miniature multileaf collimator ModuLeaf (MRC Systems GmbH, Heidelberg, Germany, now part of Siemens, Erlangen, Germany). The new CM is partly based on the existing CM called DYNVMLC. The development was performed using a modified EGSnrc platform which enables us to work in the Microsoft Visual Studio environment. In order to validate the new CM, the PRIMUS linac with 6 MV x-rays (Siemens OCS, Concord, CA, USA) equipped with the ModuLeaf mMLC was modelled. Validation was performed by two methods: (a) a ray-tracing method to check the correct geometry of the multileaf collimator (MLC) and (b) a comparison of calculated and measured results of the following dosimetrical parameters: output factors, dose profiles, field edge position penumbra, MLC interleaf leakage and transmission values. Excellent agreement was found for all parameters. It was, in particular, found that the relationship between leaf position and field edge depending on the shape of the leaf ends can be investigated with a higher accuracy by this new CM than by measurements demonstrating the usefulness of the new CM.

SU-F-T-495: Method for Simultaneous Commissioning of Multiple Truebeam (TB) Linacs: Small Field Data and the Choice of Dosimetric Lead Gap (DLG)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mihailidis, D; Mallah, J

2016-06-15

Purpose: Many times a set of multiple Varian-Truebeam (TB) linacs are acquired by an institution. Since “beam matching” is an important requirement for many facilities, we developed a strategy to perform a “simultaneous” commissioning between multiple linacs.Methods and Materials: We first commissioned the required photon beam data for eclipse on the 1st TB for all the energy modalities with a beam scanning system, while integrated measurements for output factors, of all field sizes (from 1×1 to 40×40cm{sup 2}) were conducted on the 2nd TB. Care was exercised during small field dosimetry so the appropriate detectors were used with data takenmore » between two detectors be “linked” to a larger field size (4×4cm{sup 2}) with the “daisy-chaining” technique via: OF=[M-PTW(fs)×(M-PTW(4×4))-1]×[MA12s(4×4)×(M-A12S(10×10))−1]. For all energy modalities, data that span the entire range of field size, was repeated on the next TB linac, for verification. The primarily energy-dependent dosimetric leaf gap (DLG) which was measured separately on each TB. The modeled data was validated with special measurements conducted on both linacs during commissioning. Results: Our data agreed with the “TB representative beam data” to within 0.5% for all energy modalities and field sizes ≥3×3cm2. Sample depth-doses and cross-profiles of a 3×3cm2 between the linacs agreeing to within 1% between linacs. The measured DLGs were quite different with a uniform difference of 1.3% between the two linacs. The measured DLG values are independent of the average dose rate and medium used for the measurements. Conclusion: A comprehensive method of commissioning identical Varian-TB linacs, outlining the critical issues, especially small field dosimetry and DLG. The dosimetric effect of different DLG values, when it comes to, dynamic delivery and data comparisons will be presented. The dependence of DLG value on the measurement medium (in-air vs. water) or dose rate used will also be discussed. This work was supported by CAMC Cancer Center and Alliance Oncology.« less

TH-AB-BRA-01: A Novel Doubly-Focused Multileaf Collimator Design for MR-Guided Radiation Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, H; Mutic, S; Green, O

2016-06-15

Purpose: To describe the physical and dosimetric properties of a novel double-stack multileaf collimator (MLC). Methods: One of the compromises made in the MLC design has been to employ linear-motion singly-divergent shapes. Because the MLC leading edge moves linearly, it is rounded to provide a consistent, albeit compromised penumbra. The MLC employed in the new linac-based MR-IGRT unit is designed to be doubly focused in that each leaf moves in an arc centered at the source, and the sides of the leaves are machined such that they lie parallel to a line between the leaf edge and the source. Themore » curvature of the MLC keeps motors and encoders in lower magnetic field. However, high spatial-resolution leaves are difficult to manufacture to sufficiently tight tolerances and difficult to move due to restricted space on the gantry. Wider leaves alleviate this problem with less moving parts but the coarse resolution disallows treating very small lesions. This compromise has been overcome by splitting the MLC leaf bank into two sets, stacked one upon the other and offset half of a leaf width. The dosimetry has been simulated using Monte-Carlo and a 6 MV linac in a 0.35 T magnetic field. Results: The combined MLC leaf set has a spatial resolution of effectively half of the leaf width, 4mm here. The dosimetry resolution and conformality are consistent with 4mm wide MLC assisted by inverse fluence modulation. Also, because each leaf junction is backed up by the stacked leaf that lies over the junction, the problem of tongue-and-groove dosimetry has been greatly reduced. The novel MLC design allows the use of more powerful leaf motors than would be otherwise possible if a single MLC bank is employed. Conclusions: The stacked MLC will provide highly conformal dose distributions suitable for stereotactic radiation therapy of small lesions. The research was funded by ViewRay, Inc.« less

Separation and identification of Musa acuminate Colla (banana) leaf proteins by two-dimensional gel electrophoresis and mass spectrometry.

PubMed

Lu, Y; Qi, Y X; Zhang, H; Zhang, H Q; Pu, J J; Xie, Y X

2013-12-19

To establish a proteomic reference map of Musa acuminate Colla (banana) leaf, we separated and identified leaf proteins using two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and mass spectrometry (MS). Tryptic digests of 44 spots were subjected to peptide mass fingerprinting (PMF) by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) MS. Three spots that were not identified by MALDI-TOF MS analysis were identified by searching against the NCBInr, SwissProt, and expressed sequence tag (EST) databases. We identified 41 unique proteins. The majority of the identified leaf proteins were found to be involved in energy metabolism. The results indicate that 2D-PAGE is a sensitive and powerful technique for the separation and identification of Musa leaf proteins. A summary of the identified proteins and their putative functions is discussed.

An extended PROSPECT: Advance in the leaf optical properties model separating total chlorophylls into chlorophyll a and b.

PubMed

Zhang, Yao; Huang, Jingfeng; Wang, Fumin; Blackburn, George Alan; Zhang, Hankui K; Wang, Xiuzhen; Wei, Chuanwen; Zhang, Kangyu; Wei, Chen

2017-07-25

The PROSPECT leaf optical model has, to date, well-separated the effects of total chlorophyll and carotenoids on leaf reflectance and transmittance in the 400-800 nm. Considering variations in chlorophyll a:b ratio with leaf age and physiological stress, a further separation of total plant-based chlorophylls into chlorophyll a and chlorophyll b is necessary for advanced monitoring of plant growth. In this study, we present an extended version of PROSPECT model (hereafter referred to as PROSPECT-MP) that can combine the effects of chlorophyll a, chlorophyll b and carotenoids on leaf directional hemispherical reflectance and transmittance (DHR and DHT) in the 400-800 nm. The LOPEX93 dataset was used to evaluate the capabilities of PROSPECT-MP for spectra modelling and pigment retrieval. The results show that PROSPECT-MP can both simultaneously retrieve leaf chlorophyll a and b, and also performs better than PROSPECT-5 in retrieving carotenoids concentrations. As for the simulation of DHR and DHT, the performances of PROSPECT-MP are similar to that of PROSPECT-5. This study demonstrates the potential of PROSPECT-MP for improving capabilities of remote sensing of leaf photosynthetic pigments (chlorophyll a, chlorophyll b and carotenoids) and for providing a framework for future refinements in the modelling of leaf optical properties.

SU-E-T-01: 2-D Characterization of DLG Among All MLC Leaf Pairs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumaraswamy, L; Xu, Z; Podgorsak, M

Purpose: The aim of this study is to evaluate the variation of dosimetric leaf-gap (DLG) along the travel path of each MLC leaf pair. This study evaluates whether the spatial variations in DLG could cause dose differences between TPS-calculated and measured dose. Methods: The 6MV DLG values were measured for all leaf pairs in the direction of leaf motion using a 2-D diode array and 0.6cc ion chamber. These measurements were performed on two Varian Linacs, employing the Millennium 120-leaf MLC and a 2-D-DLG variation map was created via in-house software. Several test plans were created with sweeping MLC fieldsmore » using constant gaps from 2mm to 10mm and corrected for 2-D variation utilizing in-house software. Measurements were performed utilizing the MapCHECK at 5.0cm depth for plans with and without the 2-D DLG correction and compared to the TPS calculated dose via gamma analysis (3%/3mm). Results: The measured DLGs for the middle 40 MLC leaf pairs (0.5cm width) were very similar along the central superior-inferior axis, with maximum variation of 0.2mm. The outer 20 MLC leaf pairs (1.0cm width) have DLG values from 0.32mm (mean) to 0.65mm (maximum) lower than the central leaf-pair, depending on off-axis distance. Gamma pass rates for the 2mm, 4mm, and 6mm sweep plans increased by 23.2%, 28.7%, and 26.0% respectively using the 2-D-DLG correction. The most improved dose points occur in areas modulated by the 1.0cm leaf-pairs. The gamma pass rate for the 10mm sweep plan increased by only 7.7%, indicating that the 2D variation becomes less significant for dynamic plans with larger MLC gaps. Conclusion: Fluences residing significantly off-axis with narrow sweeping gaps may exhibit significant variations from planned dose due to large differences between the true DLG exhibited by the 1.0cm leaf-pairs versus the constant DLG value utilized by the TPS for dose calculation.« less

SU-F-E-06: Dosimetric Characterization of Small Photons Beams of a Novel Linear Accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Almonte, A; Polanco, G; Sanchez, E

2016-06-15

Purpose: The aim of the present contribution was to measure the main dosimetric quantities of small fields produced by UNIQUE and evaluate its matching with the corresponding dosimetric data of one 21EX conventional linear accelerator (Varian) in operation at the same center. The second step was to evaluate comparative performance of the EDGE diode detector and the PinPoint micro-ionization chamber for dosimetry of small fields. Methods: UNIQUE is configured with MLC (120 leaves with 0.5 cm leaf width) and a single low photon energy of 6 MV. Beam data were measured with scanning EDGE diode detector (volume of 0.019 mm{supmore » 3}), a PinPoint micro-ionization chamber (PTW) and for larger fields (≥ 4×4cm{sup 2}) a PTW Semi flex chamber (0.125 cm{sup 3}) was used. The scanning system used was the 3D cylindrical tank manufactured by Sun Nuclear, Inc. The measurement of PDD and profiles were done at 100 cm SSD and 1.5 depth; the relative output factors were measured at 10 cm depth. Results: PDD and the profile data showed less than 1% variation between the two linear accelerators for fields size between 2×2 cm{sup 2} and 5×5cm{sup 2}. Output factor differences was less than 1% for field sizes between 3×3 cm{sup 2} and 10×10 cm{sup 2} and less of 1.5 % for fields of 1.5×1.5 cm{sup 2} and 2×2 cm{sup 2} respectively. The dmax value of the EDGE diode detector, measured from the PDD, was 8.347 mm for 0.5×0,5cm{sup 2} for UNIQUE. The performance of EDGE diode detector was comparable for all measurements in small fields. Conclusion: UNIQUE linear accelerator show similar dosimetrics characteristics as conventional 21EX Varian linear accelerator for small, medium and large field sizes.EDGE detector show good performance by measuring dosimetrics quantities in small fields typically used in IMRT and radiosurgery treatments.« less

Volumetric‐modulated arc therapy planning using multicriteria optimization for localized prostate cancer

PubMed Central

Ghandour, Sarah; Matzinger, Oscar

2015-01-01

The purpose of this work is to evaluate the volumetric‐modulated arc therapy (VMAT) multicriteria optimization (MCO) algorithm clinically available in the RayStation treatment planning system (TPS) and its ability to reduce treatment planning time while providing high dosimetric plan quality. Nine patients with localized prostate cancer who were previously treated with 78 Gy in 39 fractions using VMAT plans and rayArc system based on the direct machine parameter optimization (DMPO) algorithm were selected and replanned using the VMAT‐MCO system. First, the dosimetric quality of the plans was evaluated using multiple conformity metrics that account for target coverage and sparing of healthy tissue, used in our departmental clinical protocols. The conformity and homogeneity index, number of monitor units, and treatment planning time for both modalities were assessed. Next, the effects of the technical plan parameters, such as constraint leaf motion CLM (cm/°) and maximum arc delivery time T (s), on the accuracy of delivered dose were evaluated using quality assurance passing rates (QAs) measured using the Delta4 phantom from ScandiDos. For the dosimetric plan's quality analysis, the results show that the VMAT‐MCO system provides plans comparable to the rayArc system with no statistical difference for V95% (p<0.01), D1% (p<0.01), CI (p<0.01), and HI (p<0.01) of the PTV, bladder (p<0.01), and rectum (p<0.01) constraints, except for the femoral heads and healthy tissues, for which a dose reduction was observed using MCO compared with rayArc (p<0.01). The technical parameter study showed that a combination of CLM equal to 0.5 cm/degree and a maximum delivery time of 72 s allowed the accurate delivery of the VMAT‐MCO plan on the Elekta Versa HD linear accelerator. Planning evaluation and dosimetric measurements showed that VMAT‐MCO can be used clinically with the advantage of enhanced planning process efficiency by reducing the treatment planning time without impairing dosimetric quality. PACS numbers: 87.55.D, 87.55.de, 87.55.Qr PMID:26103500

SU-F-T-165: Daily QA Analysis for Spot Scanning Beamline

DOE Office of Scientific and Technical Information (OSTI.GOV)

Poenisch, F; Gillin, M; Sahoo, N

2016-06-15

Purpose: The dosimetric results of our daily quality assurance over the last 8 years for discrete pencil beam scanning proton therapy will be presented. Methods: To perform the dosimetric checks, a multi-ion chamber detector is used, which consists of an array of 5 single parallel plate ion chambers that are aligned as a cross separated by 10cm each. The Tracker is snapped into a jig, which is placed on the tabletop. Different amounts of Solid Water buildup are added to shift the dose distribution. The dosimetric checks consist of 3 parts: position check, range check and volume dose check. Results:more » The average deviation of all position-check data were 0.2±1.3%. For the range check, the average deviation was 0.1%±1.2%, which also corresponds to a range stability of better than 1 mm over all measurements. The volumetric dose output readings were all within ±1% with the exception of 2 occasions when the cable to the dose monitor was being repaired. Conclusion: Morning QA using the Tracker device gives very stable dosimetric readings but is also sensitive to mechanical and output changes in the proton therapy delivery system.« less

SU-E-T-247: Multi-Leaf Collimator Model Adjustments Improve Small Field Dosimetry in VMAT Plans

DOE Office of Scientific and Technical Information (OSTI.GOV)

Young, L; Yang, F

2014-06-01

Purpose: The Elekta beam modulator linac employs a 4-mm micro multileaf collimator (MLC) backed by a fixed jaw. Out-of-field dose discrepancies between treatment planning system (TPS) calculations and output water phantom measurements are caused by the 1-mm leaf gap required for all moving MLCs in a VMAT arc. In this study, MLC parameters are optimized to improve TPS out-of-field dose approximations. Methods: Static 2.4 cm square fields were created with a 1-mm leaf gap for MLCs that would normally park behind the jaw. Doses in the open field and leaf gap were measured with an A16 micro ion chamber andmore » EDR2 film for comparison with corresponding point doses in the Pinnacle TPS. The MLC offset table and tip radius were adjusted until TPS point doses agreed with photon measurements. Improvements to the beam models were tested using static arcs consisting of square fields ranging from 1.6 to 14.0 cm, with 45° collimator rotation, and 1-mm leaf gap to replicate VMAT conditions. Gamma values for the 3-mm distance, 3% dose difference criteria were evaluated using standard QA procedures with a cylindrical detector array. Results: The best agreement in point doses within the leaf gap and open field was achieved by offsetting the default rounded leaf end table by 0.1 cm and adjusting the leaf tip radius to 13 cm. Improvements in TPS models for 6 and 10 MV photon beams were more significant for smaller field sizes 3.6 cm or less where the initial gamma factors progressively increased as field size decreased, i.e. for a 1.6cm field size, the Gamma increased from 56.1% to 98.8%. Conclusion: The MLC optimization techniques developed will achieve greater dosimetric accuracy in small field VMAT treatment plans for fixed jaw linear accelerators. Accurate predictions of dose to organs at risk may reduce adverse effects of radiotherapy.« less

An experimental comparison of conventional two-bank and novel four-bank dynamic MLC tracking.

PubMed

Davies, G A; Clowes, P; McQuaid, D; Evans, P M; Webb, S; Poludniowski, G

2013-03-07

The AccuLeaf mMLC featuring four multileaf-collimator (MLC) banks has been used for the first time for an experimental comparison of conventional two-bank with novel four-bank dynamic MLC tracking of a two-dimensional sinusoidal respiratory motion. This comparison was performed for a square aperture, and for three conformal treatment apertures from clinical radiotherapy lung cancer patients. The system latency of this prototype tracking system was evaluated and found to be 1.0 s and the frequency at which MLC positions could be updated, 1 Hz, and therefore accurate MLC tracking of irregular patient motion would be difficult with the system in its current form. The MLC leaf velocity required for two-bank-MLC and four-bank-MLC tracking was evaluated for the apertures studied and a substantial decrease was found in the maximum MLC velocity required when four-banks were used for tracking rather than two. A dosimetric comparison of the two techniques was also performed and minimal difference was found between two-bank-MLC and four-bank-MLC tracking. The use of four MLC banks for dynamic MLC tracking is shown to be potentially advantageous for increasing the delivery efficiency compared with two-bank-MLC tracking where difficulties are encountered if large leaf shifts are required to track motion perpendicular to the direction of leaf travel.

Linking log files with dosimetric accuracy--A multi-institutional study on quality assurance of volumetric modulated arc therapy.

PubMed

Pasler, Marlies; Kaas, Jochem; Perik, Thijs; Geuze, Job; Dreindl, Ralf; Künzler, Thomas; Wittkamper, Frits; Georg, Dietmar

2015-12-01

To systematically evaluate machine specific quality assurance (QA) for volumetric modulated arc therapy (VMAT) based on log files by applying a dynamic benchmark plan. A VMAT benchmark plan was created and tested on 18 Elekta linacs (13 MLCi or MLCi2, 5 Agility) at 4 different institutions. Linac log files were analyzed and a delivery robustness index was introduced. For dosimetric measurements an ionization chamber array was used. Relative dose deviations were assessed by mean gamma for each control point and compared to the log file evaluation. Fourteen linacs delivered the VMAT benchmark plan, while 4 linacs failed by consistently terminating the delivery. The mean leaf error (±1SD) was 0.3±0.2 mm for all linacs. Large MLC maximum errors up to 6.5 mm were observed at reversal positions. Delivery robustness index accounting for MLC position correction (0.8-1.0) correlated with delivery time (80-128 s) and depended on dose rate performance. Dosimetric evaluation indicated in general accurate plan reproducibility with γ(mean)(±1 SD)=0.4±0.2 for 1 mm/1%. However single control point analysis revealed larger deviations and attributed well to log file analysis. The designed benchmark plan helped identify linac related malfunctions in dynamic mode for VMAT. Log files serve as an important additional QA measure to understand and visualize dynamic linac parameters. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Patient feature based dosimetric Pareto front prediction in esophageal cancer radiotherapy.

PubMed

Wang, Jiazhou; Jin, Xiance; Zhao, Kuaike; Peng, Jiayuan; Xie, Jiang; Chen, Junchao; Zhang, Zhen; Studenski, Matthew; Hu, Weigang

2015-02-01

To investigate the feasibility of the dosimetric Pareto front (PF) prediction based on patient's anatomic and dosimetric parameters for esophageal cancer patients. Eighty esophagus patients in the authors' institution were enrolled in this study. A total of 2928 intensity-modulated radiotherapy plans were obtained and used to generate PF for each patient. On average, each patient had 36.6 plans. The anatomic and dosimetric features were extracted from these plans. The mean lung dose (MLD), mean heart dose (MHD), spinal cord max dose, and PTV homogeneity index were recorded for each plan. Principal component analysis was used to extract overlap volume histogram (OVH) features between PTV and other organs at risk. The full dataset was separated into two parts; a training dataset and a validation dataset. The prediction outcomes were the MHD and MLD. The spearman's rank correlation coefficient was used to evaluate the correlation between the anatomical features and dosimetric features. The stepwise multiple regression method was used to fit the PF. The cross validation method was used to evaluate the model. With 1000 repetitions, the mean prediction error of the MHD was 469 cGy. The most correlated factor was the first principal components of the OVH between heart and PTV and the overlap between heart and PTV in Z-axis. The mean prediction error of the MLD was 284 cGy. The most correlated factors were the first principal components of the OVH between heart and PTV and the overlap between lung and PTV in Z-axis. It is feasible to use patients' anatomic and dosimetric features to generate a predicted Pareto front. Additional samples and further studies are required improve the prediction model.

TU-C-17A-10: Patient Features Based Dosimetric Pareto Front Prediction In Esophagus Cancer Radiotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, J; Zhao, K; Peng, J

2014-06-15

Purpose: The purpose of this study is to study the feasibility of the dosimetric pareto front (PF) prediction based on patient anatomic and dosimetric parameters for esophagus cancer patients. Methods: Sixty esophagus patients in our institution were enrolled in this study. A total 2920 IMRT plans were created to generated PF for each patient. On average, each patient had 48 plans. The anatomic and dosimetric features were extracted from those plans. The mean lung dose (MLD), mean heart dose (MHD), spinal cord max dose and PTV homogeneous index (PTVHI) were recorded for each plan. The principal component analysis (PCA) wasmore » used to extract overlap volume histogram (OVH) features between PTV and other critical organs. The full dataset was separated into two parts include the training dataset and the validation dataset. The prediction outcomes were the MHD and MLD for the current study. The spearman rank correlation coefficient was used to evaluate the correlation between the anatomical features and dosimetric features. The PF was fit by the the stepwise multiple regression method. The cross-validation method was used to evaluation the model. Results: The mean prediction error of the MHD was 465 cGy with 100 repetitions. The most correlated factors were the first principal components of the OVH between heart and PTV, and the overlap between heart and PTV in Z-axis. The mean prediction error of the MLD was 195 cGy. The most correlated factors were the first principal components of the OVH between lung and PTV, and the overlap between lung and PTV in Z-axis. Conclusion: It is feasible to use patients anatomic and dosimetric features to generate a predicted PF. Additional samples and further studies were required to get a better prediction model.« less

Patient feature based dosimetric Pareto front prediction in esophageal cancer radiotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Jiazhou; Zhao, Kuaike; Peng, Jiayuan

2015-02-15

Purpose: To investigate the feasibility of the dosimetric Pareto front (PF) prediction based on patient’s anatomic and dosimetric parameters for esophageal cancer patients. Methods: Eighty esophagus patients in the authors’ institution were enrolled in this study. A total of 2928 intensity-modulated radiotherapy plans were obtained and used to generate PF for each patient. On average, each patient had 36.6 plans. The anatomic and dosimetric features were extracted from these plans. The mean lung dose (MLD), mean heart dose (MHD), spinal cord max dose, and PTV homogeneity index were recorded for each plan. Principal component analysis was used to extract overlapmore » volume histogram (OVH) features between PTV and other organs at risk. The full dataset was separated into two parts; a training dataset and a validation dataset. The prediction outcomes were the MHD and MLD. The spearman’s rank correlation coefficient was used to evaluate the correlation between the anatomical features and dosimetric features. The stepwise multiple regression method was used to fit the PF. The cross validation method was used to evaluate the model. Results: With 1000 repetitions, the mean prediction error of the MHD was 469 cGy. The most correlated factor was the first principal components of the OVH between heart and PTV and the overlap between heart and PTV in Z-axis. The mean prediction error of the MLD was 284 cGy. The most correlated factors were the first principal components of the OVH between heart and PTV and the overlap between lung and PTV in Z-axis. Conclusions: It is feasible to use patients’ anatomic and dosimetric features to generate a predicted Pareto front. Additional samples and further studies are required improve the prediction model.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheng, Y; Ge, Y; Yuan, L

Purpose: To investigate the impact of outliers on knowledge modeling in radiation therapy, and develop a systematic workflow for identifying and analyzing geometric and dosimetric outliers using pelvic cases. Methods: Four groups (G1-G4) of pelvic plans were included: G1 (37 prostate cases), G2 (37 prostate plus lymph node cases), and G3 (37 prostate bed cases) are all clinical IMRT cases. G4 are 10 plans outside G1 re-planned with dynamic-arc to simulate dosimetric outliers. The workflow involves 2 steps: 1. identify geometric outliers, assess impact and clean up; 2. identify dosimetric outliers, assess impact and clean up.1. A baseline model wasmore » trained with all G1 cases. G2/G3 cases were then individually added to the baseline model as geometric outliers. The impact on the model was assessed by comparing leverage statistic of inliers (G1) and outliers (G2/G3). Receiver-operating-characteristics (ROC) analysis was performed to determine optimal threshold. 2. A separate baseline model was trained with 32 G1 cases. Each G4 case (dosimetric outliers) was then progressively added to perturb this model. DVH predictions were performed using these perturbed models for remaining 5 G1 cases. Normal tissue complication probability (NTCP) calculated from predicted DVH were used to evaluate dosimetric outliers’ impact. Results: The leverage of inliers and outliers was significantly different. The Area-Under-Curve (AUC) for differentiating G2 from G1 was 0.94 (threshold: 0.22) for bladder; and 0.80 (threshold: 0.10) for rectum. For differentiating G3 from G1, the AUC (threshold) was 0.68 (0.09) for bladder, 0.76 (0.08) for rectum. Significant increase in NTCP started from models with 4 dosimetric outliers for bladder (p<0.05), and with only 1 dosimetric outlier for rectum (p<0.05). Conclusion: We established a systematic workflow for identifying and analyzing geometric and dosimetric outliers, and investigated statistical metrics for detecting. Results validated the necessity for outlier detection and clean-up to enhance model quality in clinical practice. Research Grant: Varian master research grant.« less

SU-D-204-04: Correlations Between Dosimetric Indices and Follow-Up Data for Salivary Glands Six Months After Radiation Therapy for Head and Neck Cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chera, B; Price, A; Kostich, M

Purpose: To investigate the correlation between different dosimetric indices of salivary glands (as separate or combined structures) to patient-reported dry mouth 6 months post radiotherapy using the novel patient reported outcome version of the CTCAE (PRO-CTCAE). Methods: Forty-three patients with oropharyngeal squamous cell carcinoma were treated on a prospective multi-institutional study. All patients received de-intensified 60 Gy intensity modulated radiotherapy. Dosimetric constraints were used for the salivary glands (e.g. mean dose to the contralateral-parotid < 26 Gy). We investigated correlations of individual patient dosimetric data of the parotid and submandibular glands (as separate or combined structures) to their self-reported 6more » month post-treatment dry mouth responses. Moderate dry mouth responses were most prevalent and were used as the clinical endpoint indicating response. The correlation of Dmean, Dmax and a range of dosevolume (VD) points were assessed through the area under the Receiver Operating Characteristic curve (ROC) and Odds Ratios (OR). Results: Patients reporting non/mild dry mouth response (N=22) had average Dmean = 19.6 ± 6.2Gy to the contralateral-parotid compared to an average Dmean = 28.0 ± 8.3Gy and an AUC = 0.758 for the patients reporting moderate/severe/very severe dry mouth (N=21). Analysis of the range of VD’s for patients who had reported dry mouth showed that for the contralateral-parotid the indices V18 through V22 had the highest area under the curves (AUC) (0.762 – 0.772) compared to a more traditional dosimetric index V30, which had an AUC = 0.732. The highest AUC was observed for the combination of contralateral parotid and contralateral submandibular glands, for which V16 through V28 had AUC = 0.801 – 0.834. Conclusion: Patients who report moderate/severe/very severe dry mouth 6 months post radiotherapy had on average higher Dmean. The V16-V28 of the combination of the contralateral glands showed the highest correlation with the clinical endpoint.« less

SU-E-T-313: Dosimetric Deviation of Misaligned Beams for a 6 MV Photon Linear Accelerator Using Monte Carlo Simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, S

2015-06-15

Purpose: To quantify the dosimetric variations of misaligned beams for a linear accelerator by using Monte Carlo (MC) simulations. Method and Materials: Misaligned beams of a Varian 21EX Clinac were simulated to estimate the dosimetric effects. All the linac head components for a 6 MV photon beam were implemented in BEAMnrc/EGSnrc system. For incident electron beam parameters, 6 MeV with 0.1 cm full-width-half-max Gaussian beam was used. A phase space file was obtained below the jaw per each misalignment condition of the incident electron beam: (1) The incident electron beams were tilted by 0.5, 1.0 and 1.5 degrees on themore » x-axis from the central axis. (2) The center of the incident electron beam was off-axially moved toward +x-axis by 0.1, 0.2, and 0.3 cm away from the central axis. Lateral profiles for each misaligned beam condition were acquired at dmax = 1.5 cm and 10 cm depth in a rectangular water phantom. Beam flatness and symmetry were calculated by using the lateral profile data. Results: The lateral profiles were found to be skewed opposite to the angle of the incident beam for the tilted beams. For the displaced beams, similar skewed lateral profiles were obtained with small shifts of penumbra on the +x-axis. The variations of beam flatness were 3.89–11.18% and 4.12–42.57% for the tilted beam and the translated beam, respectively. The beam symmetry was separately found to be 2.95 −9.93% and 2.55–38.06% separately. It was found that the percent increase of the flatness and the symmetry values are approximated 2 to 3% per 0.5 degree tilt or per 1 mm displacement. Conclusion: This study quantified the dosimetric effects of misaligned beams using MC simulations. The results would be useful to understand the magnitude of the dosimetric deviations for the misaligned beams.« less

Diffuse and specular characteristics of leaf reflectance

NASA Technical Reports Server (NTRS)

Grant, Lois

1987-01-01

In this paper, the evolution of current understanding of the mechanisms of leaf reflectance is reviewed. The use of measurements of polarized reflectance to separate leaf reflectance into diffuse and specular components is discussed. A section on the factors influencing leaf reflectance - leaf structure and physiological disturbances - is included along with discussion on the manner in which these influences are manifested.

Commissioning of the tongue-and-groove modelling in treatment planning systems: from static fields to VMAT treatments

NASA Astrophysics Data System (ADS)

Hernandez, Victor; Vera-Sánchez, Juan Antonio; Vieillevigne, Laure; Saez, Jordi

2017-08-01

Adequate modelling of the multi-leaf collimator (MLC) by treatment planning systems (TPS) is essential for accurate dose calculations in intensity-modulated radiation-therapy. For this reason modern TPSs incorporate MLC characteristics such as the leaf end curvature, MLC transmission and the tongue-and-groove. However, the modelling of the tongue-and-groove is often neglected during TPS commissioning and it is not known how accurate it is. This study evaluates the dosimetric consequences of the tongue-and-groove effect for two different MLC models using both film dosimetry and ionisation chambers. A set of comprehensive tests are presented that evaluate the ability of TPSs to accurately model this effect in (a) static fields, (b) sliding window beams and (c) VMAT arcs. The tests proposed are useful for the commissioning of TPSs and for the validation of major upgrades. With the ECLIPSE TPS, relevant differences were found between calculations and measurements for beams with dynamic MLCs in the presence of the TG effect, especially for the High Definition MLC, small gap sizes and the 1 mm calculation grid. For this combination, dose differences as high as 10% and 7% were obtained for dynamic MLC gaps of 5 mm and 10 mm, respectively. These differences indicate inadequate modelling of the tongue-and-groove effect, which might not be identified without the proposed tests. In particular, the TPS tended to underestimate the calculated dose, which may require tuning of other configuration parameters in the TPS (such as the dosimetric leaf gap) in order to maximise the agreement between calculations and measurements in clinical plans. In conclusion, a need for better modelling of the MLC by TPSs is demonstrated, one of the relevant aspects being the tongue-and-groove effect. This would improve the accuracy of TPS calculations, especially for plans using small MLC gaps, such as plans with small target volumes or high complexities. Improved modelling of the MLC would also reduce the need for tuning parameters in the TPS, facilitating a more comprehensive configuration and commissioning of TPSs.

Dosimetric effect of Elekta Beam Modulator micromultileaf in three-dimensional conformal radiotherapy and intensity-modulated radiotherapy for prostate cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carosi, Alessandra, E-mail: alessandra.carosi@katamail.com; Ingrosso, Gianluca; Ponti, Elisabetta

2014-07-01

The purpose of this study is to analyze the dosimetric effect of Elekta Beam Modulator in 3-dimensional conformal radiation therapy (3DCRT) and in intensity-modulated radiation therapy (IMRT) for localized prostate cancer. We compared treatment plans developed with 2 different Elekta multileaf collimators (MLC): Beam Modulator micro-MLC (mMLC) (4-mm leaf width at the isocenter) and standard MLC (10-mm leaf width at the isocenter). The comparison was performed for 15 patients with localized prostate cancer in 3DCRT and IMRT delivery; a total of 60 treatment plans were processed. The dose-volume histograms were used to provide the quantitative comparison between plans. In particular,more » we analyzed differences between rectum and bladder sparing in terms of a set of appropriate Vx (percentage of organ at risk [OAR] volume receiving the x dose) and differences between target conformity and coverage in terms of coverage factor and conformation number. Our analysis demonstrates that in 3DCRT there is an advantage in the use of Elekta Beam Modulator mMLC in terms of organ sparing; in particular, a significant decrease in rectal V{sub 60} and V{sub 50} (p = 0.001) and in bladder V{sub 70} and V{sub 65} (p = 0.007 and 0.002, respectively) was found. Moreover, a better target dose conformity was obtained (p = 0.002). IMRT plans comparison demonstrated no significant differences between the use of the 4 or 10-mm MLCs. Our analysis shows that in 3DCRT the use of the Elekta Beam Modulator mMLC gives a gain in target conformity and in OARs dose sparing whereas in IMRT plans there is no advantage.« less

Dosimetric properties of high energy current (HEC) detector in keV x-ray beams.

PubMed

Zygmanski, Piotr; Shrestha, Suman; Elshahat, Bassem; Karellas, Andrew; Sajo, Erno

2015-04-07

We introduce a new x-ray radiation detector. The detector employs high-energy current (HEC) formed by secondary electrons consisting predominantly of photoelectrons and Auger electrons, to directly convert x-ray energy to detector signal without externally applied power and without amplification. The HEC detector is a multilayer structure composed of thin conducting layers separated by dielectric layers with an overall thickness of less than a millimeter. It can be cut to any size and shape, formed into curvilinear surfaces, and thus can be designed for a variety of QA applications. We present basic dosimetric properties of the detector as function of x-ray energy, depth in the medium, area and aspect ratio of the detector, as well as other parameters. The prototype detectors show similar dosimetric properties to those of a thimble ionization chamber, which operates at high voltage. The initial results obtained for kilovoltage x-rays merit further research and development towards specific medical applications.

Automation of a Linear Accelerator Dosimetric Quality Assurance Program

NASA Astrophysics Data System (ADS)

Lebron Gonzalez, Sharon H.

According to the American Society of Radiation Oncology, two-thirds of all cancer patients will receive radiation therapy during their illness with the majority of the treatments been delivered by a linear accelerator (linac). Therefore, quality assurance (QA) procedures must be enforced in order to deliver treatments with a machine in proper conditions. The overall goal of this project is to automate the linac's dosimetric QA procedures by analyzing and accomplishing various tasks. First, the photon beam dosimetry (i.e. total scatter correction factor, infinite percentage depth dose (PDD) and profiles) were parameterized. Parameterization consists of defining the parameters necessary for the specification of a dosimetric quantity model creating a data set that is portable and easy to implement for different applications including: beam modeling data input into a treatment planning system (TPS), comparing measured and TPS modelled data, the QA of a linac's beam characteristics, and the establishment of a standard data set for comparison with other data, etcetera. Second, this parameterization model was used to develop a universal method to determine the radiation field size of flattened (FF), flattening-filter-free (FFF) and wedge beams which we termed the parameterized gradient method (PGM). Third, the parameterized model was also used to develop a profile-based method for assessing the beam quality of photon FF and FFF beams using an ionization chamber array. The PDD and PDD change was also predicted from the measured profile. Lastly, methods were created to automate the multileaf collimator (MLC) calibration and QA procedures as well as the acquisition of the parameters included in monthly and annual photon dosimetric QA. A two field technique was used for the calculation of the MLC leaf relative offsets using an electronic portal imaging device (EPID). A step-and-shoot technique was used to accurately acquire the radiation field size, flatness, symmetry, output and beam quality specifiers in a single delivery to an ionization chamber array for FF and FFF beams.

An Artificial Diet for Cottonwood and Imported Williow leaf Beetles (Coleoptera: Chrysomelidae) and Comparative Performance on Poplar Foliage1,2

Treesearch

Leah S. Bauer; Joann Meerschaert; Thomas O. Forrester

1989-01-01

An artificial diet was developed for labortory rearing of the cottonwood leaf beetle, Chrysomela scripta F., and the imported willow leaf beetle, Plagiodera versicolira (Laicharting). To reduce microbial contamination of the media, procedures were developed for the separating egg masses and sterilizing egg surfaces. Cottonwood leaf...

Effect of MLC leaf width on treatment adaptation and accuracy for concurrent irradiation of prostate and pelvic lymph nodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shang Qingyang; Qi Peng; Ferjani, Samah

2013-06-15

Purpose: The aim of the study was to evaluate the impact of multileaf collimator (MLC) leaf width on treatment adaptation and delivery accuracy for concurrent treatment of the prostate and pelvic lymph nodes with intensity modulated radiation therapy (IMRT). Methods: Seventy-five kilovoltage cone beam CTs (KV-CBCT) from six patients were included for this retrospective study. For each patient, three different IMRT plans were created based on a planning CT using three different MLC leaf widths of 2.5, 5, and 10 mm, respectively. For each CBCT, the prostate displacement was determined by a dual image registration. Adaptive plans were created bymore » shifting selected MLC leaf pairs to compensate for daily prostate movements. To evaluate the impact of MLC leaf width on the adaptive plan for each daily CBCT, three MLC shifted plans were created using three different leaf widths of MLCs (a total of 225 adaptive treatment plans). Selective dosimetric endpoints for the tumor volumes and organs at risk (OARs) were evaluated for these adaptive plans. Using the planning CT from a selected patient, MLC shifted plans for three hypothetical longitudinal shifts of 2, 4, and 8 mm were delivered on the three linear accelerators to test the deliverability of the shifted plans and to compare the dose accuracy of the shifted plans with the original IMRT plans. Results: Adaptive plans from 2.5 and 5 mm MLCs had inadequate dose coverage to the prostate (D99 < 97%, or D{sub mean} < 99% of the planned dose) in 6%-8% of the fractions, while adaptive plans from 10 mm MLC led to inadequate dose coverage to the prostate in 25.3% of the fractions. The average V{sub 56Gy} of the prostate over the six patients was improved by 6.4% (1.6%-32.7%) and 5.8% (1.5%-35.7%) with adaptive plans from 2.5 and 5 mm MLCs, respectively, when compared with adaptive plans from 10 mm MLC. Pelvic lymph nodes were well covered for all MLC adaptive plans, as small differences were observed for D99, D{sub mean}, and V{sub 50.4Gy}. Similar OAR sparing could be achieved for the bladder and rectum with all three MLCs for treatment adaptation. The MLC shifted plans can be accurately delivered on all three linear accelerators with accuracy similar to their original IMRT plans, where gamma (3%/3 mm) passing rates were 99.6%, 93.0%, and 92.1% for 2.5, 5, and 10 mm MLCs, respectively. The percentages of pixels with dose differences between the measurement and calculation being less than 3% of the maximum dose were 85.9%, 82.5%, and 70.5% for the original IMRT plans from the three MLCs, respectively. Conclusions: Dosimetric advantages associated with smaller MLC leaves were observed in terms of the coverage to the prostate, when the treatment was adapted to account for daily prostate movement for concurrent irradiation of the prostate and pelvic lymph nodes. The benefit of switching the MLC from 10 to 5 mm was significant (p Much-Less-Than 0.01); however, switching the MLC from 5 to 2.5 mm would not gain significant (p= 0.15) improvement. IMRT plans with smaller MLC leaf widths achieved more accurate dose delivery.« less

SU-G-BRC-16: Theory and Clinical Implications of the Constant Dosimetric Leaf Gap (DLG) Approximation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumaraswamy, L; Xu, Z; Podgorsak, M

Purpose: Commercial dose calculation algorithms incorporate a single DLG value for a given beam energy that is applied across an entire treatment field. However, the physical processes associated with beam generation and dose delivery suggest that the DLG is not constant. The aim of this study is to evaluate the variation of DLG among all leaf pairs, to quantify how this variation impacts delivered dose, and to establish a novel method to correct dose distributions calculated using the approximation of constant DLG. Methods: A 2D diode array was used to measure the DLG for all 60 leaf pairs at severalmore » points along each leaf pair travel direction. This approach was validated by comparison to DLG values measured at select points using a 0.6 cc ion chamber with the standard formalism. In-house software was developed to enable incorporation of position dependent DLG values into dose distribution optimization and calculation. The accuracy of beam delivery of both the corrected and uncorrected treatment plans was studied through gamma pass rate evaluation. A comparison of DVH statistics in corrected and uncorrected treatment plans was made. Results: The outer 20 MLC leaf pairs (1.0 cm width) have DLG values that are 0.32 mm (mean) to 0.65 mm (maximum) lower than the central leaf-pair. VMAT plans using a large number of 1 cm wide leaves were more accurately delivered (gamma pass rate increased by 5%) and dose coverage was higher (D100 increased by 3%) when the 2D DLG was modeled. Conclusion: Using a constant DLG value for a given beam energy will result in dose optimization, dose calculation and treatment delivery inaccuracies that become significant for treatment plans with high modulation complexity scores delivered with 1 cm wide leaves.« less

Pacific Northwest Laboratory annual report for 1978 to the DOE Assistant Secretary for Environment. Part 4. Physical sciences.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nielsen, J.M.

1979-02-01

Separate abstracts were prepared for each of the five sections of this report as follows: coal; fission; geothermal; oil shale; and multitechnology. In addition, abstracts were prepared for six of the nine individual subsections of the section on fission, that relate to dosimetric studies. (ERB)

Dissecting a new connection between cytokinin and jasmonic acid in control of leaf growth

USDA-ARS?s Scientific Manuscript database

Plant growth is mediated by two cellular processes: division and elongation. The maize leaf is an excellent model to study plant growth since these processes are spatially separated into discreet zones - a division zone (DZ), transition zone (TZ), and elongation zone (EZ) - at the base of the leaf. ...

Rounded leaf end modeling in Pinnacle VMAT treatment planning for fixed jaw linacs

PubMed Central

Yang, Fei; Cao, Ning; Meyer, Juergen

2016-01-01

During volume‐modulated arc therapies (VMAT), dosimetric errors are introduced by multiple open dynamic leaf gaps that are present in fixed diaphragm linear accelerators. The purpose of this work was to develop a methodology for adjusting the rounded leaf end modeling parameters to improve out‐of‐field dose agreement in SmartArc VMAT treatment plans delivered by fixed jaw linacs where leaf gap dose is not negligible. Leaf gap doses were measured for an Elekta beam modulator linac with 0.4 cm micro‐multileaf collimators (MLC) using an A16 micro‐ionization chamber, a MatriXX ion chamber detector array, and Kodak EDR2 film dosimetry in a solid water phantom. The MLC offset and rounded end tip radius were adjusted in the Pinnacle treatment planning system (TPS) to iteratively arrive at the optimal configuration for 6 MV and 10 MV photon energies. Improvements in gamma index with a 3%/3 mm acceptance criteria and an inclusion threshold of 5% of maximum dose were measured, analyzed, and validated using an ArcCHECK diode detector array for field sizes ranging from 1.6 to 14 cm square field arcs and Task Group (TG) 119 VMAT test cases. The best results were achieved for a rounded leaf tip radius of 13 cm with a 0.1 cm MLC offset. With the optimized MLC model, measured gamma indices ranged between 99.9% and 91.7% for square field arcs with sizes between 3.6 cm and 1.6 cm, with a maximum improvement of 42.7% for the 1.6 cm square field size. Gamma indices improved up to 2.8% in TG‐119 VMAT treatment plans. Imaging and Radiation Oncology Core (IROC) credentialing of a VMAT plan with the head and neck phantom passed with a gamma index of 100%. Fine‐tune adjustments to MLC rounded leaf ends may improve patient‐specific QA pass rates and provide more accurate predictions of dose deposition to avoidance structures. PACS number(s): 87.55.D‐, 87.55.kd, 87.55.kh PMID:27929490

SU-E-T-119: Dosimetric and Mechanical Characteristics of Elekta Infinity LINAC with Agility MLC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, J; Xu, Q; Xue, J

2014-06-01

Purpose: Elekta Infinity is the one of the latest generation LINAC with unique features. Two Infinity LINACs are recently commissioned at our institution. The dosimetric and mechanical characteristics of the machines are presented. Methods: Both Infinity LINACs with Agility MLC (160 leaves with 0.5 cm leaf width) are configured with five electron energies (6, 9, 12, 15, and 18 MeV) and two photon energies (6 and 15 MV). One machine has additional photon energy (10 MV). The commissioning was performed by following the manufacturer's specifications and AAPM TG recommendations. Beam data of both electron and photon beams are measured withmore » scanning ion chambers and linear diode array. Machines are adjusted to have the dosimetrically equivalent characteristics. Results: The commissioning of mechanical and imaging system meets the tolerances by TG recommendations. The PDD{sub 10} of various field sizes for 6 and 15 MV shows < 0.5% difference between two machines. For each electron beams, R{sub 80} matches with < 0.4 mm difference. The symmetry and flatness agree within 0.8% and 0.9% differences for photon beams, respectively. For electron beams, the differences of the symmetry and flatness are within 1.2% and 0.8%, respectively. The mean inline penumbras for 6, 10, and 15 MV are respectively 5.1±0.24, 5.6±0.07, and 5.9±0.10 mm for 10x10 cm at 10 cm depth. The crossline penumbras are larger than inline penumbras by 2.2, 1.4, and 1.0 mm, respectively. The MLC transmission factor with interleaf leakage is 0.5 % for all photon energies. Conclusion: The dosimetric and mechanical characteristics of two Infinity LINACs show good agreements between them. Although the Elekta Infinity has been used in many institutions, the detailed characteristics of the machine have not been reported. This study provides invaluable information to understand the Infinity LINAC and to compare the quality of commissioning data for other LINACs.« less

Determination of active ingredients in corn silk, leaf, and kernel by capillary electrophoresis with electrochemicaI detection.

PubMed

Lin, Miao; Chu, Qing-Cui; Tian, Xiu-Hui; Ye, Jian-Nong

2007-01-01

Corn has been known for its accumulation of flavones and phenolic acids. However, many parts of corn, except kernel, have not drawn much attention. In this work, a method based on capillary zone electrophoresis with electrochemical detection has been used for the separation and determination of epicatechin, rutin, ascorbic acid (Vc), kaempferol, chlorogenic acid, and quercetin in corn silk, leaf, and kernel. The distribution comparison of the ingredients among silk, leaf, and kernel is discussed. Several important factors--including running buffer acidity, separation voltage, and working electrode potential--were evaluated to acquire the optimum analysis conditions. Under the optimum conditions, the analytes could be well separated within 19 min in a 40-mmol/L borate buffer (pH 9.2). The response was linear over three orders of magnitude with detection limits (S/N = 3) ranging from 4.97 x 10(-8) to 9.75 x 10(-8) g/mL. The method has been successfully applied for the analysis of corn silk, leaf, and kernel with satisfactory results.

Basic Principles and Practices of Integrated Dosimetric Passportization of the Settlements in Ukraine.

PubMed

Likhtarov, I A; Kovgan, L M; Masiuk, S V; Ivanova, O M; Chepurny, M I; Boyko, Z N; Gerasymenko, V B

2015-12-01

The purpose of the review is to demonstrate the results of dosimetric passportization (performed in 1991-2014) for the settlements of Ukraine which suffered from radioactive contamination caused by the Chornobyl accident. The dosimetric passportization played a key role in the National program on the liquidation of aftermath of the Chornobyl accident directed on recovery through all stages of the current radiation situation control and decision support touching upon various types of interventions and social benefits to the population of radioactively contaminated areas. The works being performed under dosimetric passportization did not have analogues among the researches which took place after other large-scale industrial and municipal accidents as well their scales as the duration of both radio-ecological and dosimetric monitoring.The new methodological approaches to the assessment of so-called passport doses of a settlement as well as to the definition of the concept of annual dose being the dose used to make decisions for providing both direct and indirect emergency countermeasures for the settlements of Ukraine became pioneering ones. During all the post-accident period there were issued sixteen collections of general dosimetric passportization data which accumulate the results of hundreds of thousands spectrometric, radiochemical and radiation levels measurements and WBC measurements carried out in 1991-2014.The annual passport doses calculated on the basis of these measurements (including their components) are unique information that quantifies the level and time dynamics of the radiation situation for each of the 2161 settlements of 74 raions in 12 oblasts during all the post-accident period. Thanks to the works of dosimetric passportization of the settlements of Ukraine there were created databases to be unique in their structure and content with quantitative characteristics of the territorial and temporal distribution, the dynamics of changes of a number of important radiological parameters, namely over 500 thousands of measurements of concentration of 137Cs and 90Sr in the local foodstuff (milk and potatoes); there are more than 1.3 million of measurements of the cesium content in the body of residents of the settlements of Ukraine; there are 100 thousands of dose estimates (both internal and external ones were measured separately) of inhabitants living on the radioactively contaminated areas. The results of the dosimetric passportization served as one of the main exposure criteria for generalized aftermath of the Chornobyl accident represented in the National reports for the first 15, 20 and 25 years after the accident. I. A. Likhtarov, L. M. Kovgan, S. V. Masiuk, O. M. Ivanova, M. I. Chepurny.

Coordination between leaf and stem traits related to leaf carbon gain and hydraulics across 32 drought-tolerant angiosperms.

PubMed

Ishida, Atsushi; Nakano, Takashi; Yazaki, Kenichi; Matsuki, Sawako; Koike, Nobuya; Lauenstein, Diego L; Shimizu, Michiru; Yamashita, Naoko

2008-05-01

We examined 15 traits in leaves and stems related to leaf C economy and water use for 32 co-existing angiosperms at ridge sites with shallow soil in the Bonin Islands. Across species, stem density was positively correlated to leaf mass per area (LMA), leaf lifespan (LLS), and total phenolics and condensed tannins per unit leaf N (N-based), and negatively correlated to leaf osmotic potential and saturated water content in leaves. LMA and LLS were negatively correlated to photosynthetic parameters, such as area-, mass-, and N-based assimilation rates. Although stem density and leaf osmotic potential were not associated with photosynthetic parameters, they were associated with some parameters of the leaf C economy, such as LMA and LLS. In the principal component (PCA) analysis, the first three axes accounted for 74.4% of total variation. Axis 1, which explained 41.8% of the total variation, was well associated with parameters for leaf C and N economy. Similarly, axis 2, which explained 22.3% of the total variation, was associated with parameters for water use. Axis 3, which explained 10.3% of the total variation, was associated with chemical defense within leaves. Axes 1 and 2 separated functional types relatively well, i.e., creeping trees, ruderal trees, other woody plants, C(3) shrubs and forbs, palms, and CAM plants, indicating that plant functional types were characterized by similar attributes of traits related to leaf C and N economy and water use. In addition, when the plot was extended by two unrelated traits, leaf mass-based assimilation rates and stem density, it also separated these functional types. These data indicate that differences in the functional types with contrasting plant strategies can be attributed to functional integration among leaf C economy, hydraulics, and leaf longevity, and that both leaf mass-based assimilation rates and stem density are key factors reflecting the different functions of plant species.

Correction of respiratory motion for IMRT using aperture adaptive technique and visual guidance: A feasibility study

NASA Astrophysics Data System (ADS)

Chen, Ho-Hsing; Wu, Jay; Chuang, Keh-Shih; Kuo, Hsiang-Chi

2007-07-01

Intensity-modulated radiation therapy (IMRT) utilizes nonuniform beam profile to deliver precise radiation doses to a tumor while minimizing radiation exposure to surrounding normal tissues. However, the problem of intrafraction organ motion distorts the dose distribution and leads to significant dosimetric errors. In this research, we applied an aperture adaptive technique with a visual guiding system to toggle the problem of respiratory motion. A homemade computer program showing a cyclic moving pattern was projected onto the ceiling to visually help patients adjust their respiratory patterns. Once the respiratory motion becomes regular, the leaf sequence can be synchronized with the target motion. An oscillator was employed to simulate the patient's breathing pattern. Two simple fields and one IMRT field were measured to verify the accuracy. Preliminary results showed that after appropriate training, the amplitude and duration of volunteer's breathing can be well controlled by the visual guiding system. The sharp dose gradient at the edge of the radiation fields was successfully restored. The maximum dosimetric error in the IMRT field was significantly decreased from 63% to 3%. We conclude that the aperture adaptive technique with the visual guiding system can be an inexpensive and feasible alternative without compromising delivery efficiency in clinical practice.

Dosimetric investigations of cosmic radiation aboard the Kosmos-936 AES (joint Soviet-American experiment K-206)

NASA Technical Reports Server (NTRS)

Benton, E. V.; Kovalyev, Y. Y.; Dudkin, V. Y.

1980-01-01

The Soviet and American parts of the experiment are described separately. Particular attention was given to the following problems: placement of the detectors; study of neutron radiation within the biosatellite; and studies of fragmentation of heavy nuclei on accelerators. Unified methods were developed for the calibration of Soviet and American detectors.

Geometric morphometrics analysis of the hind wing of leaf beetles: proximal and distal parts are separate modules.

PubMed

Ren, Jing; Bai, Ming; Yang, Xing-Ke; Zhang, Run-Zhi; Ge, Si-Qin

2017-01-01

The success of beetles is mainly attributed to the possibility to hide the hindwings under the sclerotised elytra. The acquisition of the transverse folding function of the hind wing is an important event in the evolutionary history of beetles. In this study, the morphological and functional variances in the hind wings of 94 leaf beetle species (Coleoptera: Chrysomelinae) is explored using geometric morphometrics based on 36 landmarks. Principal component analysis and Canonical variate analysis indicate that changes of apical area, anal area, and middle area are three useful phylogenetic features at a subtribe level of leaf beetles. Variances of the apical area are the most obvious, which strongly influence the entire venation variance. Partial least squares analysis indicates that the proximal and distal parts of hind wings are weakly associated. Modularity tests confirm that the proximal and distal compartments of hind wings are separate modules. It is deduced that for leaf beetles, or even other beetles, the hind wing possibly exhibits significant functional divergences that occurred during the evolution of transverse folding that resulted in the proximal and distal compartments of hind wings evolving into separate functional modules.

Scaling up stomatal conductance from leaf to canopy using a dual-leaf model for estimating crop evapotranspiration.

PubMed

Ding, Risheng; Kang, Shaozhong; Du, Taisheng; Hao, Xinmei; Zhang, Yanqun

2014-01-01

The dual-source Shuttleworth-Wallace model has been widely used to estimate and partition crop evapotranspiration (λET). Canopy stomatal conductance (Gsc), an essential parameter of the model, is often calculated by scaling up leaf stomatal conductance, considering the canopy as one single leaf in a so-called "big-leaf" model. However, Gsc can be overestimated or underestimated depending on leaf area index level in the big-leaf model, due to a non-linear stomatal response to light. A dual-leaf model, scaling up Gsc from leaf to canopy, was developed in this study. The non-linear stomata-light relationship was incorporated by dividing the canopy into sunlit and shaded fractions and calculating each fraction separately according to absorbed irradiances. The model includes: (1) the absorbed irradiance, determined by separately integrating the sunlit and shaded leaves with consideration of both beam and diffuse radiation; (2) leaf area for the sunlit and shaded fractions; and (3) a leaf conductance model that accounts for the response of stomata to PAR, vapor pressure deficit and available soil water. In contrast to the significant errors of Gsc in the big-leaf model, the predicted Gsc using the dual-leaf model had a high degree of data-model agreement; the slope of the linear regression between daytime predictions and measurements was 1.01 (R2 = 0.98), with RMSE of 0.6120 mm s-1 for four clear-sky days in different growth stages. The estimates of half-hourly λET using the dual-source dual-leaf model (DSDL) agreed well with measurements and the error was within 5% during two growing seasons of maize with differing hydrometeorological and management strategies. Moreover, the estimates of soil evaporation using the DSDL model closely matched actual measurements. Our results indicate that the DSDL model can produce more accurate estimation of Gsc and λET, compared to the big-leaf model, and thus is an effective alternative approach for estimating and partitioning λET.

Projected Improvements in Accelerated Partial Breast Irradiation Using a Novel Breast Stereotactic Radiotherapy Device: A Dosimetric Analysis.

PubMed

Snider, James W; Mutaf, Yildirim; Nichols, Elizabeth; Hall, Andrea; Vadnais, Patrick; Regine, William F; Feigenberg, Steven J

2017-01-01

Accelerated partial breast irradiation has caused higher than expected rates of poor cosmesis. At our institution, a novel breast stereotactic radiotherapy device has demonstrated dosimetric distributions similar to those in brachytherapy. This study analyzed comparative dose distributions achieved with the device and intensity-modulated radiation therapy accelerated partial breast irradiation. Nine patients underwent computed tomography simulation in the prone position using device-specific immobilization on an institutional review board-approved protocol. Accelerated partial breast irradiation target volumes (planning target volume_10mm) were created per the National Surgical Adjuvant Breast and Bowel Project B-39 protocol. Additional breast stereotactic radiotherapy volumes using smaller margins (planning target volume_3mm) were created based on improved immobilization. Intensity-modulated radiation therapy and breast stereotactic radiotherapy accelerated partial breast irradiation plans were separately generated for appropriate volumes. Plans were evaluated based on established dosimetric surrogates of poor cosmetic outcomes. Wilcoxon rank sum tests were utilized to contrast volumes of critical structures receiving a percentage of total dose ( Vx). The breast stereotactic radiotherapy device consistently reduced dose to all normal structures with equivalent target coverage. The ipsilateral breast V20-100 was significantly reduced ( P < .05) using planning target volume_10mm, with substantial further reductions when targeting planning target volume_3mm. Doses to the chest wall, ipsilateral lung, and breast skin were also significantly lessened. The breast stereotactic radiotherapy device's uniform dosimetric improvements over intensity-modulated accelerated partial breast irradiation in this series indicate a potential to improve outcomes. Clinical trials investigating this benefit have begun accrual.

Temporal versus spatial variation in leaf reflectance under changing water stress conditions

NASA Technical Reports Server (NTRS)

Cohen, Warren B.

1991-01-01

Leaf reflectance changes associated with changes in water stress were analyzed in two separate experiments. Results indicate that the variation in reflectance among collections of leaves of a given species all at the same level of water stress is at least as great as the variation in reflectance associated with changes in water stress for a given leaf collection of that species. The implications is that results from leaf reflectance-water stress studies have only limited applicability to the remote sensing of plant canopy water stress.

Scaling Up Stomatal Conductance from Leaf to Canopy Using a Dual-Leaf Model for Estimating Crop Evapotranspiration

PubMed Central

Ding, Risheng; Kang, Shaozhong; Du, Taisheng; Hao, Xinmei; Zhang, Yanqun

2014-01-01

The dual-source Shuttleworth-Wallace model has been widely used to estimate and partition crop evapotranspiration (λET). Canopy stomatal conductance (Gsc), an essential parameter of the model, is often calculated by scaling up leaf stomatal conductance, considering the canopy as one single leaf in a so-called “big-leaf” model. However, Gsc can be overestimated or underestimated depending on leaf area index level in the big-leaf model, due to a non-linear stomatal response to light. A dual-leaf model, scaling up Gsc from leaf to canopy, was developed in this study. The non-linear stomata-light relationship was incorporated by dividing the canopy into sunlit and shaded fractions and calculating each fraction separately according to absorbed irradiances. The model includes: (1) the absorbed irradiance, determined by separately integrating the sunlit and shaded leaves with consideration of both beam and diffuse radiation; (2) leaf area for the sunlit and shaded fractions; and (3) a leaf conductance model that accounts for the response of stomata to PAR, vapor pressure deficit and available soil water. In contrast to the significant errors of Gsc in the big-leaf model, the predicted Gsc using the dual-leaf model had a high degree of data-model agreement; the slope of the linear regression between daytime predictions and measurements was 1.01 (R2 = 0.98), with RMSE of 0.6120 mm s−1 for four clear-sky days in different growth stages. The estimates of half-hourly λET using the dual-source dual-leaf model (DSDL) agreed well with measurements and the error was within 5% during two growing seasons of maize with differing hydrometeorological and management strategies. Moreover, the estimates of soil evaporation using the DSDL model closely matched actual measurements. Our results indicate that the DSDL model can produce more accurate estimation of Gsc and λET, compared to the big-leaf model, and thus is an effective alternative approach for estimating and partitioning λET. PMID:24752329

The effect of glyphosate on import into a sink leaf of sugar beet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shieh, Wenjang; Geiger, D.R.

1990-05-01

The basis for glyphosate inducted limitation of carbon import into developing leaves was studied in sugar beet. To separate the effects of the herbicide on export from those on import, glyphosate was supplied to a developing leaf from two exporting source leaves which fed the sink leaf. Carbon import into the sink leaf was determined by supplying {sup 14}CO{sub 2} to a third source leaf which also supplies carbon to the monitored sink leaf. Import into the sink leaf decreased within 2 to 3 h after glyphosate application, even though photosynthesis and export in the source leaf supplying {sup 14}Cmore » were unaffected. Reduced import into the sink leaf was accompanied by increased import by the tap root. Elongation of the sink leaf was only slightly decreased following arrival of glyphosate. Photosynthesis by the sink leaf was not inhibited. The results to data support the view that import is slowed by the inhibition of synthesis of structural or storage compounds in the developing leaves.« less

Expanded separation technique for chlorophyll metabolites in Oriental tobacco leaf using non aqueous reversed phase chromatography.

PubMed

Ishida, Naoyuki

2011-08-26

An improved separation method for chlorophyll metabolites in Oriental tobacco leaf was developed. While Oriental leaf still gives the green color even after the curing process, little attention has been paid to the detailed composition of the remaining green pigments. This study aimed to identify the green pigments using non aqueous reversed phase chromatography (NARPC). To this end, liquid chromatograph (LC) equipped with a photo diode array detector (DAD) and an atmospheric pressure chemical ionization/mass spectrometer (APCI/MSD) was selected, because it is useful for detecting low polar non-volatile compounds giving green color such as pheophytin a. Identification was based on the wavelength spectrum, mass spectrum and retention time, comparing the analytes in Oriental leaf with the commercially available and synthesized components. Consequently, several chlorophyll metabolites such as hydroxypheophytin a, solanesyl pheophorbide a and solanesyl hydroxypheophorbide a were newly identified, in addition to typical green pigments such as chlorophyll a and pheophytin a. Chlorophyll metabolites bound to solanesol were considered the tobacco specific components. NARPC expanded the number of detectable low polar chlorophyll metabolites in Oriental tobacco leaf. Copyright © 2011 Elsevier B.V. All rights reserved.

SU-E-T-315: Dosimetric Effects of Couch Top Shift On VMAT Delivery in Absence of Indexing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Islam, M; Jin, H; Ferguson, S

2015-06-15

Purpose: To investigate dosimetric effects of couch top shift for volumetric-modulated arc therapy (VMAT) in absence of indexing of immobilization devices. Methods: A total of twelve VMAT treatment plans were selected from three regions (lung, abdomen, and pelvis) to account for the variation of the patient position relative to the couch top. The treatment plans were generated using the Varian Eclipse system. A pinpoint ionization chamber (PTW TN31014) was placed at the center of 16-cm solid water phantom and the dose was delivered using the Varian TrueBeam STx with BrainLAB ExacTrac couch top. To simulate the day-to-day variation of themore » patient position relative to couch top, the couch top was laterally shifted up to 50 mm, with an increment of 5 mm from 0 to 20 mm; and of 10 mm afterwards, and the phantom was moved back to 0 cm shift for measurement. The dose was also delivered using a Varian tennis racket grid insert at 0 cm shift to simulate the absence of couch top. The treatment plans were delivered with 6, 10, and 15 MV photons using the same leaf sequencing to investigate the energy dependence of couch top shift. The dose difference was normalized to 0 cm shift for the regular couch top for comparison. Results: The percent difference of dose was found to increase with lateral shift for all energies; however, the average differences were close to 0% and the maximum difference was within 1% along the lateral shifts. The differences with the absence of couch top were 2.2±0.5% (6MV), 1.7±0.3% (10MV), and 1.6±0.2% (15MV), respectively. Conclusion: The inclusion of couch top is recommended in treatment planning to minimize the dosimetric uncertainty between calculated and delivered dose even in absence of indexing of immobilization devices in VMAT delivery.« less

Evaluation of a commercially‐available block for spatially fractionated radiation therapy

PubMed Central

Buckey, Courtney; Cashon, Ken; Gutierrez, Alonso; Esquivel, Carlos; Shi, Chengyu; Papanikolaou, Nikos

2010-01-01

In this paper, we present the dosimetric characteristics of a commercially‐produced universal GRID block for spatially fractioned radiation therapy. The dosimetric properties of the GRID block were evaluated. Ionization chamber and film measurements using both Kodak EDR2 and Gafchromic EBT film were performed in a solid water phantom to determine the relative output of the GRID block as well as its spatial dosimetric characteristics. The surface dose under the block and at the openings was measured using ultra thin TLDs. After introducing the GRID block into the treatment planning system, a treatment plan was created using the GRID block and also by creating a GRID pattern using the multi‐leaf collimator. The percent depth doses measured with film showed that there is a shift of the dmax towards shallower depths for both energies (6 MV and 18 MV) under investigation. It was observed that the skin dose at the GRID openings was higher than the corresponding open field by a factor as high as 50% for both photon energies. The profiles showed the transmission under the block was in the order of 15–20% for 6 MV and 30% for 18 MV. The MUs calculated for a real patient using the block were about 80% less than the corresponding MUs for the same plan using the multileaf collimator to define the GRID. Based on this investigation, this brass GRID compensator is a viable alternative to other solid compensators or MLC‐based fields currently in use. Its ease of creation and use give it decided advantages. Its ability to be created once and used for multiple patients (by varying the collimation of the linear accelerator jaws) makes it attractive from a cost perspective. We believe this compensator can be put to clinical use, and will allow more centers to offer GRID therapy to their patients. PACS number: 87.53.Mr

LEAF AREA INDEX (LAI) CHANGE DETECTION ANALYSIS ON LOBLOLLY PINE (PINUS TAEDA) FOLLOWING COMPLETE UNDERSTORY REMOVAL

EPA Science Inventory

The confounding effect of understory vegetation contributions to satellite-derived estimates of leaf area index (LAI) was investigated on two loblolly pine (Pinus taeda) forest stands located in Virginia and North Carolina. In order to separate NDVI contributions of the dominantc...

Performance of a multi leaf collimator system for MR-guided radiation therapy.

PubMed

Cai, Bin; Li, Harold; Yang, Deshan; Rodriguez, Vivian; Curcuru, Austen; Wang, Yuhe; Wen, Jie; Kashani, Rojano; Mutic, Sasa; Green, Olga

2017-12-01

The purpose of this study was to investigate and characterize the performance of a Multi Leaf Collimator (MLC) designed for Cobalt-60 based MR-guided radiation therapy system in a 0.35 T magnetic field. The MLC design and unique assembly features in the ViewRay MRIdian system were first reviewed. The RF cage shielding of MLC motor and cables were evaluated using ACR phantoms with real-time imaging and quantified by signal-to-noise ratio. The dosimetric characterizations, including the leaf transmission, leaf penumbra, tongue-and-groove effect, were investigated using radiosensitive films. The output factor of MLC-defined fields was measured with ionization chambers for both symmetric fields from 2.1 × 2.1 cm 2 to 27.3 × 27.3 cm 2 and asymmetric fields from 10.5 × 10.5 cm 2 to 10.5 × 2.0 cm 2 . Multi leaf collimator (MLC) positional accuracy was assessed by delivering either a picket fence (PF) style pattern on radiochromic films with wire-jig phantom or double and triple-rectangular patterns on ArcCheck-MR (Sun Nuclear, Melbourne, FL, USA) with gamma analysis as the pass/fail indicator. Leaf speed tests were performed to assess the capability of full range leaf travel within manufacture's specifications. Multi leaf collimator plan delivery reproducibility was tested by repeatedly delivering both open fields and fields with irregular shaped segments over 1-month period. Comparable SNRs within 4% were observed for MLC moving and stationary plans on vendor-reconstructed images, and the direct k-space reconstructed images showed that the three SNRs are within 1%. The maximum leaf transmission for all three MLCs was less than 0.35% and the average leakage was 0.153 ± 0.006%, 0.151 ± 0.008%, and 0.159 ± 0.015% for head 1, 2, and 3, respectively. Both the leaf edge and leaf end penumbra showed comparable values within 0.05 cm, and the measured values are within 0.1 cm with TPS values. The leaf edge TG effect indicated 10% underdose and the leaf end TG showed a shifted dose distribution with 0.3 cm offset. The leaf positioning test showed a 0.2 cm accuracy in the PF style test, and a gamma passing rate above 96% was observed with a 3%/2 mm criteria when comparing the measured double/triple-rectangular pattern fluence with TPS calculated fluence. The average leaf speed when executing the test plan fell in a range from 1.86 to 1.95 cm/s. The measured and TPS calculated output factors were within 2% for squared fields and within 3% for rectangular fields. The reproducibility test showed the deviation of output factors were well within 2% for square fields and the gamma passing rate within 1.5% for fields with irregular segments. The Monte Carlo predicted output factors were within 2% compared to TPS values. 15 out of the 16 IMRT plans have gamma passing rate more than 98% compared to the TPS fluence with an average passing rate of 99.1 ± 0.6%. The MRIdian MLC has a good RF noise shielding design, low radiation leakage, good positioning accuracy, comparable TG effect, and can be modeled by an independent Monte Carlo calculation platform. © 2017 American Association of Physicists in Medicine.

SU-F-P-39: End-To-End Validation of a 6 MV High Dose Rate Photon Beam, Configured for Eclipse AAA Algorithm Using Golden Beam Data, for SBRT Treatments Using RapidArc

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ferreyra, M; Salinas Aranda, F; Dodat, D

Purpose: To use end-to-end testing to validate a 6 MV high dose rate photon beam, configured for Eclipse AAA algorithm using Golden Beam Data (GBD), for SBRT treatments using RapidArc. Methods: Beam data was configured for Varian Eclipse AAA algorithm using the GBD provided by the vendor. Transverse and diagonals dose profiles, PDDs and output factors down to a field size of 2×2 cm2 were measured on a Varian Trilogy Linac and compared with GBD library using 2% 2mm 1D gamma analysis. The MLC transmission factor and dosimetric leaf gap were determined to characterize the MLC in Eclipse. Mechanical andmore » dosimetric tests were performed combining different gantry rotation speeds, dose rates and leaf speeds to evaluate the delivery system performance according to VMAT accuracy requirements. An end-to-end test was implemented planning several SBRT RapidArc treatments on a CIRS 002LFC IMRT Thorax Phantom. The CT scanner calibration curve was acquired and loaded in Eclipse. PTW 31013 ionization chamber was used with Keithley 35617EBS electrometer for absolute point dose measurements in water and lung equivalent inserts. TPS calculated planar dose distributions were compared to those measured using EPID and MapCheck, as an independent verification method. Results were evaluated with gamma criteria of 2% dose difference and 2mm DTA for 95% of points. Results: GBD set vs. measured data passed 2% 2mm 1D gamma analysis even for small fields. Machine performance tests show results are independent of machine delivery configuration, as expected. Absolute point dosimetry comparison resulted within 4% for the worst case scenario in lung. Over 97% of the points evaluated in dose distributions passed gamma index analysis. Conclusion: Eclipse AAA algorithm configuration of the 6 MV high dose rate photon beam using GBD proved efficient. End-to-end test dose calculation results indicate it can be used clinically for SBRT using RapidArc.« less

SU-F-T-305: Clinical Effects of Dosimetric Leaf Gap (DLG) Values Between Matched Varian Truebeam (TB) Linacs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mihailidis, D; Mallah, J; Zhu, D

2016-06-15

Purpose: The dosimetric leaf gap (DLG) is an important parameter to be measured for dynamic beam delivery of modern linacs, like the Varian Truebeam (TB). The clinical effects of DLG-values on IMRT and/or VMAT commissioning of two “matched” TB linacs will be presented.Methods and Materials: The DLG values on two TB linacs were measured for all energy modalities (filtered and FFF-modes) as part of the dynamic delivery mode commissioning (IMRT and/or VMAT. After the standard beam data was modeled in eclipse treatment planning system (TPS) and validated, IMRT validation was performed based on TG1191 benchmark, IROC Head-Neck (H&N) phantom andmore » sample of clinical cases, all measured on both linacs. Although there was a single-set of data entered in the TPS, a noticeable difference was observed for the DLG-values between the linacs. The TG119, IROC phantom and selected patient plans were furnished with DLG-values of TB1 for both linacs and the delivery was performed on both TB linacs for comparison. Results: The DLG values of TB1 was first used for both linacs to perform the testing comparisons. The QA comparison of TG119 plans revealed a great dependence of the results to the DLG-values used for the linac for all energy modalities studied, especially when moving from 3%/3mm to 2%/2mm γ-analysis. Conclusion: The DLG-values have a definite influence on the dynamic dose, delivery that increases with the plan complexity. We recommend that the measured DLG-values are assigned to each of the “matched” linacs, even if a single set of beam data describes multiple linacs. The user should perform a detail test of the dynamic delivery of each linac based on end-to-end benchmark suites like TG119 and IROC phantoms.1Ezzel G., et al., “IMRT commissioning: Multiple institution planning and dosimetry comparisons, a report from AAPM Task Group 119.” Med. Phys. 36:5359–5373 (2009). partly supported by CAMC Cancer Center and Alliance Oncology.« less

Dynamic simulation of motion effects in IMAT lung SBRT.

PubMed

Zou, Wei; Yin, Lingshu; Shen, Jiajian; Corradetti, Michael N; Kirk, Maura; Munbodh, Reshma; Fang, Penny; Jabbour, Salma K; Simone, Charles B; Yue, Ning J; Rengan, Ramesh; Teo, Boon-Keng Kevin

2014-11-01

Intensity modulated arc therapy (IMAT) has been widely adopted for Stereotactic Body Radiotherapy (SBRT) for lung cancer. While treatment dose is optimized and calculated on a static Computed Tomography (CT) image, the effect of the interplay between the target and linac multi-leaf collimator (MLC) motion is not well described and may result in deviations between delivered and planned dose. In this study, we investigated the dosimetric consequences of the inter-play effect on target and organs at risk (OAR) by simulating dynamic dose delivery using dynamic CT datasets. Fifteen stage I non-small cell lung cancer (NSCLC) patients with greater than 10 mm tumor motion treated with SBRT in 4 fractions to a dose of 50 Gy were retrospectively analyzed for this study. Each IMAT plan was initially optimized using two arcs. Simulated dynamic delivery was performed by associating the MLC leaf position, gantry angle and delivered beam monitor units (MUs) for each control point with different respiratory phases of the 4D-CT using machine delivery log files containing time stamps of the control points. Dose maps associated with each phase of the 4D-CT dose were calculated in the treatment planning system and accumulated using deformable image registration onto the exhale phase of the 4D-CT. The original IMAT plans were recalculated on the exhale phase of the CT for comparison with the dynamic simulation. The dose coverage of the PTV showed negligible variation between the static and dynamic simulation. There was less than 1.5% difference in PTV V95% and V90%. The average inter-fraction and cumulative dosimetric effects among all the patients were less than 0.5% for PTV V95% and V90% coverage and 0.8 Gy for the OARs. However, in patients where target is close to the organs, large variations were observed on great vessels and bronchus for as much as 4.9 Gy and 7.8 Gy. Limited variation in target dose coverage and OAR constraints were seen for each SBRT fraction as well as over all four fractions. Large dose variations were observed on critical organs in patients where these organs were closer to the target.

SU-E-T-360: End-To-End Dosimetric Testing of a Versa HD Linear Accelerator with the Agility Head Modeled in Pinnacle3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saenz, D; Narayanasamy, G; Cruz, W

2015-06-15

Purpose: The Versa HD incorporates a variety of upgrades, primarily including the Agility head. The distinct dosimetric properties of the head from its predecessors combined with flattening-filter-free (FFF) beams require a new investigation of modeling in planning systems and verification of modeling accuracy. Methods: A model was created in Pinnacle{sup 3} v9.8 with commissioned beam data. Leaf transmission was modeled as <0.5% with maximum leaf speed of 3 cm/s. Photon spectra were tuned for FFF beams, for which profiles were modeled with arbitrary profiles rather than with cones. For verification, a variety of plans with varied parameters were devised, andmore » point dose measurements were compared to calculated values. A phantom of several plastic water and Styrofoam slabs was scanned and imported into Pinnacle{sup 3}. Beams of different field sizes, SSD, wedges, and gantry angles were created. All available photon energies (6 MV, 10 MV, 18 MV, 6 FFF, 10 FFF) as well four clinical electron energies (6, 9, 12, and 15 MeV) were investigated. The plans were verified at a calculation point (8 cm deep for photons, variable for electrons) by measurement with a PTW Semiflex ionization chamber. In addition, IMRT testing was performed with three standard plans (step and shoot IMRT, small and large field VMAT plans). The plans were delivered on the Delta4 IMRT QA phantom (ScandiDos, Uppsala, Sweden). Results: Homogeneous point dose measurement agreed within 2% for all photon and electron beams. Open field photon measurements along the central axis at 100 cm SSD passed within 1%. Gamma passing rates were >99.5% for all plans with a 3%/3mm tolerance criteria. The IMRT QA results for the first 23 patients yielded gamma passing rates of 97.4±2.3%. Conclusion: The end-to-end testing ensured confidence in the ability of Pinnacle{sup 3} to model photon and electron beams with the Agility head.« less

Influences of the El Nino Southern Oscillation and the Pacific Decadal Oscillation on the Timing of the North American Spring

NASA Technical Reports Server (NTRS)

McCabe, Gregory J.; Ault, Toby R.; Cook, Benjamin I.; Betancourt, Julio L.; Schwartz, Mark D.

2012-01-01

Detrended, modelled first leaf dates for 856 sites across North America for the period 1900-2008 are used to examine how the El Nino Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) separately and together might influence the timing of spring. Although spring (mean March through April) ENSO and PDO signals are apparent in first leaf dates, the signals are not statistically significant (at a 95% confidence level (p <0.05)) for most sites. The most significant ENSO/PDO signal in first leaf dates occurs for El Nino and positive PDO conditions. An analysis of the spatial distributions of first leaf dates for separate and combined ENSO/PDO conditions features a northwest-southeast dipole that is significantly (at p <0.05) different than the distributions for neutral conditions. The nature of the teleconnection between Pacific SST's and first leaf dates is evident in comparable composites for detrended sea level pressure (SLP) in the spring months. During positive ENSO/PDO, there is an anomalous flow of warm air from the southwestern US into the northwestern US and an anomalous northeasterly flow of cold air from polar regions into the eastern and southeastern US. These flow patterns are reversed during negative ENSO/PDO. Although the magnitudes of first leaf date departures are not necessarily significantly related to ENSO and PDO, the spatial patterns of departures are significantly related to ENSO and PDO. These significant relations and the long-lived persistence of SSTs provide a potential tool for forecasting the tendencies for first leaf dates to be early or late.

Systems-level Proteomics of Two Ubiquitous Leaf Commensals Reveals Complementary Adaptive Traits for Phyllosphere Colonization*

PubMed Central

Müller, Daniel B.; Schubert, Olga T.; Röst, Hannes; Aebersold, Ruedi; Vorholt, Julia A.

2016-01-01

Plants are colonized by a diverse community of microorganisms, the plant microbiota, exhibiting a defined and conserved taxonomic structure. Niche separation based on spatial segregation and complementary adaptation strategies likely forms the basis for coexistence of the various microorganisms in the plant environment. To gain insights into organism-specific adaptations on a molecular level, we selected two exemplary community members of the core leaf microbiota and profiled their proteomes upon Arabidopsis phyllosphere colonization. The highly quantitative mass spectrometric technique SWATH MS was used and allowed for the analysis of over two thousand proteins spanning more than three orders of magnitude in abundance for each of the model strains. The data suggest that Sphingomonas melonis utilizes amino acids and hydrocarbon compounds during colonization of leaves whereas Methylobacterium extorquens relies on methanol metabolism in addition to oxalate metabolism, aerobic anoxygenic photosynthesis and alkanesulfonate utilization. Comparative genomic analyses indicates that utilization of oxalate and alkanesulfonates is widespread among leaf microbiota members whereas, aerobic anoxygenic photosynthesis is almost exclusively found in Methylobacteria. Despite the apparent niche separation between these two strains we also found a relatively small subset of proteins to be coregulated, indicating common mechanisms, underlying successful leaf colonization. Overall, our results reveal for two ubiquitous phyllosphere commensals species-specific adaptations to the host environment and provide evidence for niche separation within the plant microbiota. PMID:27457762

Impact of potato psyllid (Hemiptera: Triozide) feeding on free amino acid composition in potato

USDA-ARS?s Scientific Manuscript database

Foliage feeding impacts of potato psyllid (Bactericera cockerelli) on the free amino acids (FAAs) composition in potato leaf and tuber were determined under the greenhouse conditions. The free amino acids in plant extracts were separated by HPLC, and in both leaf and tuber samples, at least, 17 FAAs...

SU-E-T-404: Simple Field-In-Field Technique for Total Body Irradiation in Large Patients

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chi, P; Pinnix, C; Dabaja, B

2014-06-01

Purpose: A simple Field-in-Field technique for Total Body Irradiation (TBI) was developed for traditional AP/PA TBI treatments to improve dosimetric uniformity in patients with large separation. Methods: TBI at our institution currently utilizes an AP/PA technique at an extended source-to-surface distance (SSD) of 380cm with patients in left decubitus position during the AP beam and in right decubitus during the PA beam. Patients who have differences in thickness (separation) between the abdomen and head greater than 10cm undergo CT simulation in both left and right decubitus treatment positions. One plan for each CT is generated to evaluate dose to patientmore » midline with both AP and PA fields, but only corresponding AP fields will be exported for treatment for patient left decubitus position and PA fields for patient right decubitus position. Subfields are added by collimating with the x-ray jaws according to separation changes at 5–7% steps to minimize hot regions to less than 10%. Finally, the monitor units (MUs) for the plans are verified with hand calculation and water phantom measurements. Results: Dose uniformity (+/−10%) is achieved with field-in-field using only asymmetric jaws. It is dosimetrically robust with respect to minor setup/patient variations inevitable due to patient conditions. MUs calculated with Pinnacle were verified in 3 clinical cases and only a 2% difference was found compared to homogeneous calculation. In-vivo dosimeters were also used to verify doses received by each patient with and confirmed dose variations less than 10%. Conclusion: We encountered several cases with separation differences that raised uniformity concerns — based on a 1% dose difference per cm separation difference assumption. This could Resultin an unintended hot spot, often in the head/neck, up to 25%. This method allows dose modulation without adding treatment complexity nor introducing radiobiological variations, providing a reasonable solution for this unique TBI situation.« less

SU-E-T-467: Monte Carlo Dosimetric Study of the New Flexisource Co-60 High Dose Rate Source.

PubMed

Vijande, J; Granero, D; Perez-Calatayud, J; Ballester, F

2012-06-01

Recently, a new HDR 60Co brachytherapy source, Flexisource Co-60, has been developed (Nucletron B.V.). This study aims to obtain quality dosimetric data for this source for its use in clinical practice as required by AAPM and ESTRO. Penelope2008 and GEANT4 Monte Carlo codes were used to dosimetrically characterize this source. Water composition and mass density was that recommended by AAPM. Due to the high energy of the 60Co, dose for small distances cannot be approximated by collisional kerma. Therefore, we have considered absorbed dose to water for r<0.75 cm and collisional kerma from 0.75 0.8 cm and up to 2% closer to the source. Using Penelope2008 and GEANT4, an average of Î> = 1.085±0.003 cGy/(h U) (with k = 1, Type A uncertainties) was obtained. Dose rate constant, radial dose function and anisotropy functions for the Flexisource Co-60 are compared with published data for other Co-60 sources. Dosimetric data are provided for the new Flexisource Co-60 source not studied previously in the literature. Using the data provided by this study in the treatment planning systems, it can be used in clinical practice. This project has been funded by Nucletron BV. © 2012 American Association of Physicists in Medicine.

Dosimetric Predictors of Duodenal Toxicity After Intensity Modulated Radiation Therapy for Treatment of the Para-aortic Nodes in Gynecologic Cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Verma, Jonathan; Sulman, Erik P.; Jhingran, Anuja

Purpose: To determine the incidence of duodenal toxicity in patients receiving intensity modulated radiation therapy (IMRT) for treatment of para-aortic nodes and to identify dosimetric parameters predictive of late duodenal toxicity. Methods and Materials: We identified 105 eligible patients with gynecologic malignancies who were treated with IMRT for gross metastatic disease in the para-aortic nodes from January 1, 2005, through December 31, 2009. Patients were treated to a nodal clinical target volume to 45 to 50.4 Gy with a boost to 60 to 66 Gy. The duodenum was contoured, and dosimetric data were exported for analysis. Duodenal toxicity was scoredmore » according to Radiation Therapy Oncology Group criteria. Univariate Cox proportional hazards analysis and recursive partitioning analysis were used to determine associations between dosimetric variables and time to toxicity and to identify the optimal threshold that separated patients according to risk of toxicity. Results: Nine of the 105 patients experienced grade 2 to grade 5 duodenal toxicity, confirmed by endoscopy in all cases. The 3-year actuarial rate of any duodenal toxicity was 11.7%. A larger volume of the duodenum receiving 55 Gy (V55) was associated with higher rates of duodenal toxicity. The 3-year actuarial rates of duodenal toxicity with V55 above and below 15 cm{sup 3} were 48.6% and 7.4%, respectively (P<.01). In Cox univariate analysis of dosimetric variables, V55 was associated with duodenal toxicity (P=.029). In recursive partitioning analysis, V55 less than 13.94% segregated all patients with duodenal toxicity. Conclusions: Dose-escalated IMRT can safely and effectively treat para-aortic nodal disease in gynecologic malignancies, provided that care is taken to limit the dose to the duodenum to reduce the risk of late duodenal toxicity. Limiting V55 to below 15 cm{sup 3} may reduce the risk of duodenal complications. In cases where the treatment cannot be delivered within these constraints, consideration should be given to other treatment approaches such as resection or initial chemotherapy.« less

Effect of blood activity on dosimetric calculations for radiopharmaceuticals

NASA Astrophysics Data System (ADS)

Zvereva, Alexandra; Petoussi-Henss, Nina; Li, Wei Bo; Schlattl, Helmut; Oeh, Uwe; Zankl, Maria; Graner, Frank Philipp; Hoeschen, Christoph; Nekolla, Stephan G.; Parodi, Katia; Schwaiger, Markus

2016-11-01

The objective of this work was to investigate the influence of the definition of blood as a distinct source on organ doses, associated with the administration of a novel radiopharmaceutical for positron emission tomography-computed tomography (PET/CT) imaging—(S)-4-(3-18F-fluoropropyl)-L-glutamic acid (18F-FSPG). Personalised pharmacokinetic models were constructed based on clinical PET/CT images from five healthy volunteers and blood samples from four of them. Following an identifiability analysis of the developed compartmental models, person-specific model parameters were estimated using the commercial program SAAM II. Organ doses were calculated in accordance to the formalism promulgated by the Committee on Medical Internal Radiation Dose (MIRD) and the International Commission on Radiological Protection (ICRP) using specific absorbed fractions for photons and electrons previously derived for the ICRP reference adult computational voxel phantoms. Organ doses for two concepts were compared: source organ activities in organs parenchyma with blood as a separate source (concept-1); aggregate activities in perfused source organs without blood as a distinct source (concept-2). Aggregate activities comprise the activities of organs parenchyma and the activity in the regional blood volumes (RBV). Concept-1 resulted in notably higher absorbed doses for most organs, especially non-source organs with substantial blood contents, e.g. lungs (92% maximum difference). Consequently, effective doses increased in concept-1 compared to concept-2 by 3-10%. Not considering the blood as a distinct source region leads to an underestimation of the organ absorbed doses and effective doses. The pronounced influence of the blood even for a radiopharmaceutical with a rapid clearance from the blood, such as 18F-FSPG, suggests that blood should be introduced as a separate compartment in most compartmental pharmacokinetic models and blood should be considered as a distinct source in dosimetric calculations. Hence, blood samples should be included in all pharmacokinetic and dosimetric studies for new tracers if possible.

Incorporating geometric ray tracing to generate initial conditions for intensity modulated arc therapy optimization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oliver, Mike; Gladwish, Adam; Craig, Jeff

2008-07-15

Purpose and background: Intensity modulated arc therapy (IMAT) is a rotational variant of Intensity modulated radiation therapy (IMRT) that is achieved by allowing the multileaf collimator (MLC) positions to vary as the gantry rotates around the patient. This work describes a method to generate an IMAT plan through the use of a fast ray tracing technique based on dosimetric and geometric information for setting initial MLC leaf positions prior to final IMAT optimization. Methods and materials: Three steps were used to generate an IMAT plan. The first step was to generate arcs based on anatomical contours. The second step wasmore » to generate ray importance factor (RIF) maps by ray tracing the dose distribution inside the planning target volume (PTV) to modify the MLC leaf positions of the anatomical arcs to reduce the maximum dose inside the PTV. The RIF maps were also segmented to create a new set of arcs to improve the dose to low dose voxels within the PTV. In the third step, the MLC leaf positions from all arcs were put through a leaf position optimization (LPO) algorithm and brought into a fast Monte Carlo dose calculation engine for a final dose calculation. The method was applied to two phantom cases, a clinical prostate case and the Radiological Physics Center (RPC)'s head and neck phantom. The authors assessed the plan improvements achieved by each step and compared plans with and without using RIF. They also compared the IMAT plan with an IMRT plan for the RPC phantom. Results: All plans that incorporated RIF and LPO had lower objective function values than those that incorporated LPO only. The objective function value was reduced by about 15% after the generation of RIF arcs and 52% after generation of RIF arcs and leaf position optimization. The IMAT plan for the RPC phantom had similar dose coverage for PTV1 and PTV2 (the same dose volume histogram curves), however, slightly lower dose to the normal tissues compared to a six-field IMRT plan. Conclusion: The use of a ray importance factor can generate initial IMAT arcs efficiently for further MLC leaf position optimization to obtain more favorable IMAT plan.« less

Solar UV exposures measured simultaneously to all arbitrarily oriented leaves on a plant.

PubMed

Parisi, Alfio V; Schouten, Peter; Downs, Nathan J; Turner, Joanna

2010-05-03

The possible ramifications of climate change include the influence it has upon the amount of cloud cover in the atmosphere. Clouds cause significant variation in the solar UV radiation reaching the earth's surface and in turn the amount incident on ecosystems. The consequences of changes in solar UV radiation delivered to ecosystems due to climate change may be significant and should be investigated. Plants are an integral part of the world wide ecological balance, and research has shown they are affected by variations in solar UV radiation. Therefore research into the influence of solar UV radiation on plants is of particular significance. However, this requires a means of obtaining detailed information on the solar UV radiation received by plants. This research describes a newly developed dosimetric technique employed to gather information on solar UV radiation incident to the leaves of plants in combination with the measurement of spectral irradiances in order to provide an accurate method of collecting detailed information on the solar UV radiation affecting the canopy and lower leaf layers of individual plants. Variations in the measurements take into account the inclination and orientation of each leaf investigated, as well as the influence of shading by other leaves in the plant canopy. Copyright 2010 Elsevier B.V. All rights reserved.

SU-E-T-261: Plan Quality Assurance of VMAT Using Fluence Images Reconstituted From Log-Files

DOE Office of Scientific and Technical Information (OSTI.GOV)

Katsuta, Y; Shimizu, E; Matsunaga, K

2014-06-01

Purpose: A successful VMAT plan delivery includes precise modulations of dose rate, gantry rotational and multi-leaf collimator (MLC) shapes. One of the main problem in the plan quality assurance is dosimetric errors associated with leaf-positional errors are difficult to analyze because they vary with MU delivered and leaf number. In this study, we calculated integrated fluence error image (IFEI) from log-files and evaluated plan quality in the area of all and individual MLC leaves scanned. Methods: The log-file reported the expected and actual position for inner 20 MLC leaves and the dose fraction every 0.25 seconds during prostate VMAT onmore » Elekta Synergy. These data were imported to in-house software that developed to calculate expected and actual fluence images from the difference of opposing leaf trajectories and dose fraction at each time. The IFEI was obtained by adding all of the absolute value of the difference between expected and actual fluence images corresponding. Results: In the area all MLC leaves scanned in the IFEI, the average and root mean square (rms) were 2.5 and 3.6 MU, the area of errors below 10, 5 and 3 MU were 98.5, 86.7 and 68.1 %, the 95 % of area was covered with less than error of 7.1 MU. In the area individual MLC leaves scanned in the IFEI, the average and rms value were 2.1 – 3.0 and 3.1 – 4.0 MU, the area of errors below 10, 5 and 3 MU were 97.6 – 99.5, 81.7 – 89.5 and 51.2 – 72.8 %, the 95 % of area was covered with less than error of 6.6 – 8.2 MU. Conclusion: The analysis of the IFEI reconstituted from log-file was provided detailed information about the delivery in the area of all and individual MLC leaves scanned.« less

SWIMRT: A graphical user interface using the sliding window algorithm to construct a fluence map machine file

PubMed Central

Chow, James C.L.; Grigorov, Grigor N.; Yazdani, Nuri

2006-01-01

A custom‐made computer program, SWIMRT, to construct “multileaf collimator (MLC) machine” file for intensity‐modulated radiotherapy (IMRT) fluence maps was developed using MATLAB® and the sliding window algorithm. The user can either import a fluence map with a graphical file format created by an external treatment‐planning system such as Pinnacle3 or create his or her own fluence map using the matrix editor in the program. Through comprehensive calibrations of the dose and the dimension of the imported fluence field, the user can use associated image‐processing tools such as field resizing and edge trimming to modify the imported map. When the processed fluence map is suitable, a “MLC machine” file is generated for our Varian 21 EX linear accelerator with a 120‐leaf Millennium MLC. This machine file is transferred to the MLC console of the LINAC to control the continuous motions of the leaves during beam irradiation. An IMRT field is then irradiated with the 2D intensity profiles, and the irradiated profiles are compared to the imported or modified fluence map. This program was verified and tested using film dosimetry to address the following uncertainties: (1) the mechanical limitation due to the leaf width and maximum traveling speed, and (2) the dosimetric limitation due to the leaf leakage/transmission and penumbra effect. Because the fluence map can be edited, resized, and processed according to the requirement of a study, SWIMRT is essential in studying and investigating the IMRT technique using the sliding window algorithm. Using this program, future work on the algorithm may include redistributing the time space between segmental fields to enhance the fluence resolution, and readjusting the timing of each leaf during delivery to avoid small fields. Possible clinical utilities and examples for SWIMRT are given in this paper. PACS numbers: 87.53.Kn, 87.53.St, 87.53.Uv PMID:17533330

WE-H-BRC-05: Catastrophic Error Metrics for Radiation Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murphy, S; Molloy, J

Purpose: Intuitive evaluation of complex radiotherapy treatments is impractical, while data transfer anomalies create the potential for catastrophic treatment delivery errors. Contrary to prevailing wisdom, logical scrutiny can be applied to patient-specific machine settings. Such tests can be automated, applied at the point of treatment delivery and can be dissociated from prior states of the treatment plan, potentially revealing errors introduced early in the process. Methods: Analytical metrics were formulated for conventional and intensity modulated RT (IMRT) treatments. These were designed to assess consistency between monitor unit settings, wedge values, prescription dose and leaf positioning (IMRT). Institutional metric averages formore » 218 clinical plans were stratified over multiple anatomical sites. Treatment delivery errors were simulated using a commercial treatment planning system and metric behavior assessed via receiver-operator-characteristic (ROC) analysis. A positive result was returned if the erred plan metric value exceeded a given number of standard deviations, e.g. 2. The finding was declared true positive if the dosimetric impact exceeded 25%. ROC curves were generated over a range of metric standard deviations. Results: Data for the conventional treatment metric indicated standard deviations of 3%, 12%, 11%, 8%, and 5 % for brain, pelvis, abdomen, lung and breast sites, respectively. Optimum error declaration thresholds yielded true positive rates (TPR) between 0.7 and 1, and false positive rates (FPR) between 0 and 0.2. Two proposed IMRT metrics possessed standard deviations of 23% and 37%. The superior metric returned TPR and FPR of 0.7 and 0.2, respectively, when both leaf position and MUs were modelled. Isolation to only leaf position errors yielded TPR and FPR values of 0.9 and 0.1. Conclusion: Logical tests can reveal treatment delivery errors and prevent large, catastrophic errors. Analytical metrics are able to identify errors in monitor units, wedging and leaf positions with favorable sensitivity and specificity. In part by Varian.« less

SU-E-T-610: Comparison of Treatment Times Between the MLCi and Agility Multileaf Collimators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramsey, C; Bowling, J

2014-06-01

Purpose: The Agility is a new 160-leaf MLC developed by Elekta for use in their Infinity and Versa HD linacs. As compared to the MLCi, the Agility increased the maximum leaf speed from 2 cm/s to 3.5 cm/s, and the maximum primary collimator speed from 1.5 cm/s to 9.0 cm/s. The purpose of this study was to determine if the Agility MLC resulted in improved plan quality and/or shorter treatment times. Methods: An Elekta Infinity that was originally equipped with a 80 leaf MLCi was upgraded to an 160 leaf Agility. Treatment plan quality was evaluated using the Pinnacle planningmore » system with SmartArc. Optimization was performed once for the MLCi and once for the Agility beam models using the same optimization parameters and the same number of iterations. Patient treatment times were measured for all IMRT, VMAT, and SBRT patients treated on the Infinity with the MLCi and Agility MLCs. Treatment times were extracted from the EMR and measured from when the patient first walked into the treatment room until exiting the treatment room. Results: 11,380 delivery times were measured for patients treated with the MLCi, and 1,827 measurements have been made for the Agility MLC. The average treatment times were 19.1 minutes for the MLCi and 20.8 minutes for the Agility. Using a t-test analysis, there was no difference between the two groups (t = 0.22). The dose differences between patients planned with the MLCi and the Agility MLC were minimal. For example, the dose difference for the PTV, GTV, and cord for a head and neck patient planned using Pinnacle were effectively equivalent. However, the dose to the parotid glands was slightly worse with the Agility MLC. Conclusion: There was no statistical difference in treatment time, or any significant dosimetric difference between the Agility MLC and the MLCi.« less

Influences of the El Niño Southern Oscillation and the Pacific Decadal Oscillation on the timing of the North American spring

USGS Publications Warehouse

McCabe, Gregory J.; Ault, Toby R.; Cook, Benjamin I.; Betancourt, Julio L.; Schwartz, Mark D.

2012-01-01

Detrended, modelled first leaf dates for 856 sites across North America for the period 1900–2008 are used to examine how the El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) separately and together might influence the timing of spring. Although spring (mean March through April) ENSO and PDO signals are apparent in first leaf dates, the signals are not statistically significant (at a 95% confidence level (p < 0.05)) for most sites. The most significant ENSO/PDO signal in first leaf dates occurs for El Niño and positive PDO conditions. An analysis of the spatial distributions of first leaf dates for separate and combined ENSO/PDO conditions features a northwest–southeast dipole that is significantly (at p < 0.05) different than the distributions for neutral conditions. The nature of the teleconnection between Pacific SST's and first leaf dates is evident in comparable composites for detrended sea level pressure (SLP) in the spring months. During positive ENSO/PDO, there is an anomalous flow of warm air from the southwestern US into the northwestern US and an anomalous northeasterly flow of cold air from polar regions into the eastern and southeastern US. These flow patterns are reversed during negative ENSO/PDO. Although the magnitudes of first leaf date departures are not necessarily significantly related to ENSO and PDO, the spatial patterns of departures are significantly related to ENSO and PDO. These significant relations and the long-lived persistence of SSTs provide a potential tool for forecasting the tendencies for first leaf dates to be early or late.

Leaf hydraulic conductance declines in coordination with photosynthesis, transpiration and leaf water status as soybean leaves age regardless of soil moisture

PubMed Central

Locke, Anna M.; Ort, Donald R.

2014-01-01

Photosynthesis requires sufficient water transport through leaves for stomata to remain open as water transpires from the leaf, allowing CO2 to diffuse into the leaf. The leaf water needs of soybean change over time because of large microenvironment changes over their lifespan, as leaves mature in full sun at the top of the canopy and then become progressively shaded by younger leaves developing above. Leaf hydraulic conductance (K leaf), a measure of the leaf’s water transport capacity, can often be linked to changes in microenvironment and transpiration demand. In this study, we tested the hypothesis that K leaf would decline in coordination with transpiration demand as soybean leaves matured and aged. Photosynthesis (A), stomatal conductance (g s) and leaf water potential (Ψleaf) were also measured at various leaf ages with both field- and chamber-grown soybeans to assess transpiration demand. K leaf was found to decrease as soybean leaves aged from maturity to shading to senescence, and this decrease was strongly correlated with midday A. Decreases in K leaf were further correlated with decreases in g s, although the relationship was not as strong as that with A. Separate experiments investigating the response of K leaf to drought demonstrated no acclimation of K leaf to drought conditions to protect against cavitation or loss of g s during drought and confirmed the effect of leaf age in K leaf observed in the field. These results suggest that the decline of leaf hydraulic conductance as leaves age keeps hydraulic supply in balance with demand without K leaf becoming limiting to transpiration water flux. PMID:25281701

Systems-level Proteomics of Two Ubiquitous Leaf Commensals Reveals Complementary Adaptive Traits for Phyllosphere Colonization.

PubMed

Müller, Daniel B; Schubert, Olga T; Röst, Hannes; Aebersold, Ruedi; Vorholt, Julia A

2016-10-01

Plants are colonized by a diverse community of microorganisms, the plant microbiota, exhibiting a defined and conserved taxonomic structure. Niche separation based on spatial segregation and complementary adaptation strategies likely forms the basis for coexistence of the various microorganisms in the plant environment. To gain insights into organism-specific adaptations on a molecular level, we selected two exemplary community members of the core leaf microbiota and profiled their proteomes upon Arabidopsis phyllosphere colonization. The highly quantitative mass spectrometric technique SWATH MS was used and allowed for the analysis of over two thousand proteins spanning more than three orders of magnitude in abundance for each of the model strains. The data suggest that Sphingomonas melonis utilizes amino acids and hydrocarbon compounds during colonization of leaves whereas Methylobacterium extorquens relies on methanol metabolism in addition to oxalate metabolism, aerobic anoxygenic photosynthesis and alkanesulfonate utilization. Comparative genomic analyses indicates that utilization of oxalate and alkanesulfonates is widespread among leaf microbiota members whereas, aerobic anoxygenic photosynthesis is almost exclusively found in Methylobacteria. Despite the apparent niche separation between these two strains we also found a relatively small subset of proteins to be coregulated, indicating common mechanisms, underlying successful leaf colonization. Overall, our results reveal for two ubiquitous phyllosphere commensals species-specific adaptations to the host environment and provide evidence for niche separation within the plant microbiota. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Dosimetric evaluation of the interplay effect in respiratory-gated RapidArc radiation therapy.

PubMed

Riley, Craig; Yang, Yong; Li, Tianfang; Zhang, Yongqian; Heron, Dwight E; Huq, M Saiful

2014-01-01

Volumetric modulated arc therapy (VMAT) with gating capability has had increasing adoption in many clinics in the United States. In this new technique, dose rate, gantry rotation speed, and the leaf motion speed of multileaf collimators (MLCs) are modulated dynamically during gated beam delivery to achieve highly conformal dose coverage of the target and normal tissue sparing. Compared with the traditional gated intensity-modulated radiation therapy technique, this complicated beam delivery technique may result in larger dose errors due to the intrafraction tumor motion. The purpose of this work is to evaluate the dosimetric influence of the interplay effect for the respiration-gated VMAT technique (RapidArc, Varian Medical Systems, Palo Alto, CA). Our work consisted of two parts: (1) Investigate the interplay effect for different target residual errors during gated RapidArc delivery using a one-dimensional moving phantom capable of producing stable sinusoidal movement; (2) Evaluate the dosimetric influence in ten clinical patients' treatment plans using a moving phantom driven with a patient-specific respiratory curve. For the first part of this study, four plans were created with a spherical target for varying residual motion of 0.25, 0.5, 0.75, and 1.0 cm. Appropriate gating windows were applied for each. The dosimetric effect was evaluated using EDR2 film by comparing the gated delivery with static delivery. For the second part of the project, ten gated lung stereotactic body radiotherapy cases were selected and reoptimized to be delivered by the gated RapidArc technique. These plans were delivered to a phantom, and again the gated treatments were compared to static deliveries by the same methods. For regular sinusoidal motion, the dose delivered to the target was not substantially affected by the gating windows when evaluated with the gamma statistics, suggesting the interplay effect has a small role in respiratory-gated RapidArc therapy. Varied results were seen when gated therapy was performed on the patient plans that could only be attributed to differences in patient respiratory patterns. Patients whose plans had the largest percentage of pixels failing the gamma statistics exhibited irregular breathing patterns including substantial interpatient variation in depth of respiration. The interplay effect has a limited impact on gated RapidArc therapy when evaluated with a linear phantom. Variations in patient breathing patterns, however, are of much greater clinical significance. Caution must be taken when evaluating patients' respiratory efforts for gated arc therapy.

De novo transcriptome sequencing and customized abscission zone-specific microarray as a new molecular tool for analysis of tomato organ abscission

USDA-ARS?s Scientific Manuscript database

Abscission, which is the process of organ separation, is a highly regulated process occurring as a final stage of organ development. In the tomato (Solanum lycopersicum) system, flower and leaf abscission was induced by flower removal or leaf deblading, leading to auxin depletion which results in in...

Biomass and decay rates of roots and detritus in sediments of intermittent coastal plain streams

Treesearch

Ken M. Fritz; Jack W. Feminella; Chris Colson; B. Graeme Lockaby; Robin Governo; Robert B. Rummer

2006-01-01

Biomass and breakdown of tree roots within streambed sediments were compared with leaf and wood detritus in three Coastal Plain headwater intermittent streams. Three separate riparian forest treatments were applied: thinned, clearcut, and reference. Biomass of roots (live and dead) and leaf/wood was significantly higher in stream banks than in the channel and declined...

Image Segmentation of Historical Handwriting from Palm Leaf Manuscripts

NASA Astrophysics Data System (ADS)

Surinta, Olarik; Chamchong, Rapeeporn

Palm leaf manuscripts were one of the earliest forms of written media and were used in Southeast Asia to store early written knowledge about subjects such as medicine, Buddhist doctrine and astrology. Therefore, historical handwritten palm leaf manuscripts are important for people who like to learn about historical documents, because we can learn more experience from them. This paper presents an image segmentation of historical handwriting from palm leaf manuscripts. The process is composed of three steps: 1) background elimination to separate text and background by Otsu's algorithm 2) line segmentation and 3) character segmentation by histogram of image. The end result is the character's image. The results from this research may be applied to optical character recognition (OCR) in the future.

Protein profiling in potato (Solanum tuberosum L.) leaf tissues by differential centrifugation.

PubMed

Lim, Sanghyun; Chisholm, Kenneth; Coffin, Robert H; Peters, Rick D; Al-Mughrabi, Khalil I; Wang-Pruski, Gefu; Pinto, Devanand M

2012-04-06

Foliar diseases, such as late blight, result in serious threats to potato production. As such, potato leaf tissue becomes an important substrate to study biological processes, such as plant defense responses to infection. Nonetheless, the potato leaf proteome remains poorly characterized. Here, we report protein profiling of potato leaf tissues using a modified differential centrifugation approach to separate the leaf tissues into cell wall and cytoplasmic fractions. This method helps to increase the number of identified proteins, including targeted putative cell wall proteins. The method allowed for the identification of 1484 nonredundant potato leaf proteins, of which 364 and 447 were reproducibly identified proteins in the cell wall and cytoplasmic fractions, respectively. Reproducibly identified proteins corresponded to over 70% of proteins identified in each replicate. A diverse range of proteins was identified based on their theoretical pI values, molecular masses, functional classification, and biological processes. Such a protein extraction method is effective for the establishment of a highly qualified proteome profile.

Assessment of dosimetric impact of system specific geometric distortion in an MRI only based radiotherapy workflow for prostate

NASA Astrophysics Data System (ADS)

Gustafsson, C.; Nordström, F.; Persson, E.; Brynolfsson, J.; Olsson, L. E.

2017-04-01

Dosimetric errors in a magnetic resonance imaging (MRI) only radiotherapy workflow may be caused by system specific geometric distortion from MRI. The aim of this study was to evaluate the impact on planned dose distribution and delineated structures for prostate patients, originating from this distortion. A method was developed, in which computer tomography (CT) images were distorted using the MRI distortion field. The displacement map for an optimized MRI treatment planning sequence was measured using a dedicated phantom in a 3 T MRI system. To simulate the distortion aspects of a synthetic CT (electron density derived from MR images), the displacement map was applied to CT images, referred to as distorted CT images. A volumetric modulated arc prostate treatment plan was applied to the original CT and the distorted CT, creating a reference and a distorted CT dose distribution. By applying the inverse of the displacement map to the distorted CT dose distribution, a dose distribution in the same geometry as the original CT images was created. For 10 prostate cancer patients, the dose difference between the reference dose distribution and inverse distorted CT dose distribution was analyzed in isodose level bins. The mean magnitude of the geometric distortion was 1.97 mm for the radial distance of 200-250 mm from isocenter. The mean percentage dose differences for all isodose level bins, were  ⩽0.02% and the radiotherapy structure mean volume deviations were  <0.2%. The method developed can quantify the dosimetric effects of MRI system specific distortion in a prostate MRI only radiotherapy workflow, separated from dosimetric effects originating from synthetic CT generation. No clinically relevant dose difference or structure deformation was found when 3D distortion correction and high acquisition bandwidth was used. The method could be used for any MRI sequence together with any anatomy of interest.

Assessment of dosimetric impact of system specific geometric distortion in an MRI only based radiotherapy workflow for prostate.

PubMed

Gustafsson, C; Nordström, F; Persson, E; Brynolfsson, J; Olsson, L E

2017-04-21

Dosimetric errors in a magnetic resonance imaging (MRI) only radiotherapy workflow may be caused by system specific geometric distortion from MRI. The aim of this study was to evaluate the impact on planned dose distribution and delineated structures for prostate patients, originating from this distortion. A method was developed, in which computer tomography (CT) images were distorted using the MRI distortion field. The displacement map for an optimized MRI treatment planning sequence was measured using a dedicated phantom in a 3 T MRI system. To simulate the distortion aspects of a synthetic CT (electron density derived from MR images), the displacement map was applied to CT images, referred to as distorted CT images. A volumetric modulated arc prostate treatment plan was applied to the original CT and the distorted CT, creating a reference and a distorted CT dose distribution. By applying the inverse of the displacement map to the distorted CT dose distribution, a dose distribution in the same geometry as the original CT images was created. For 10 prostate cancer patients, the dose difference between the reference dose distribution and inverse distorted CT dose distribution was analyzed in isodose level bins. The mean magnitude of the geometric distortion was 1.97 mm for the radial distance of 200-250 mm from isocenter. The mean percentage dose differences for all isodose level bins, were  ⩽0.02% and the radiotherapy structure mean volume deviations were  <0.2%. The method developed can quantify the dosimetric effects of MRI system specific distortion in a prostate MRI only radiotherapy workflow, separated from dosimetric effects originating from synthetic CT generation. No clinically relevant dose difference or structure deformation was found when 3D distortion correction and high acquisition bandwidth was used. The method could be used for any MRI sequence together with any anatomy of interest.

Impact of Chemotherapy on Normal Tissue Complication Probability Models of Acute Hematologic Toxicity in Patients Receiving Pelvic Intensity Modulated Radiation Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bazan, Jose G.; Luxton, Gary; Kozak, Margaret M.

Purpose: To determine how chemotherapy agents affect radiation dose parameters that correlate with acute hematologic toxicity (HT) in patients treated with pelvic intensity modulated radiation therapy (P-IMRT) and concurrent chemotherapy. Methods and Materials: We assessed HT in 141 patients who received P-IMRT for anal, gynecologic, rectal, or prostate cancers, 95 of whom received concurrent chemotherapy. Patients were separated into 4 groups: mitomycin (MMC) + 5-fluorouracil (5FU, 37 of 141), platinum ± 5FU (Cis, 32 of 141), 5FU (26 of 141), and P-IMRT alone (46 of 141). The pelvic bone was contoured as a surrogate for pelvic bone marrow (PBM) andmore » divided into subsites: ilium, lower pelvis, and lumbosacral spine (LSS). The volumes of each region receiving 5-40 Gy were calculated. The endpoint for HT was grade ≥3 (HT3+) leukopenia, neutropenia or thrombocytopenia. Normal tissue complication probability was calculated using the Lyman-Kutcher-Burman model. Logistic regression was used to analyze association between HT3+ and dosimetric parameters. Results: Twenty-six patients experienced HT3+: 10 of 37 (27%) MMC, 14 of 32 (44%) Cis, 2 of 26 (8%) 5FU, and 0 of 46 P-IMRT. PBM dosimetric parameters were correlated with HT3+ in the MMC group but not in the Cis group. LSS dosimetric parameters were well correlated with HT3+ in both the MMC and Cis groups. Constrained optimization (0« less

Validation of Pinnacle treatment planning system for use with Novalis delivery unit.

PubMed

Faygelman, Vladimir; Hunt, Dylan; Walker, Luke; Mueller, Richard; Demarco, Mary Lou; Dilling, Thomas; Stevens, Craig; Zhang, Geoffrey

2010-06-15

For an institution that already owns the licenses, it is economically advantageous and technically feasible to use Pinnacle TPS (Philips Radiation Oncology Systems, Fitchburg, WI) with the BrainLab Novalis delivery system (BrainLAB A.G., Heimstetten, Germany). This takes advantage of the improved accuracy of the convolution algorithm in the presence of heterogeneities compared with the pencil beam calculation, which is particularly significant for lung SBRT treatments. The reference patient positioning DRRs still have to be generated by the BrainLab software from the CT images and isocenter coordinates transferred from Pinnacle. We validated this process with the end-to-end hidden target test, which showed an isocenter positioning error within one standard deviation from the previously established mean value. The Novalis treatment table attenuation is substantial (up to 6.2% for a beam directed straight up and up to 8.4% for oblique incidence) and has to be accounted for in calculations. A simple single-contour treatment table model was developed, resulting in mean differences between the measured and calculated attenuation factors of 0.0%-0.2%, depending on the field size. The maximum difference for a single incidence angle is 1.1%. The BrainLab micro-MLC (mMLC) leaf tip, although not geometrically round, can be represented in Pinnacle by an arch with satisfactory dosimetric accuracy. Subsequently, step-and-shoot (direct machine parameter optimization) IMRT dosimetric agreement is excellent. VMAT (called "SmartArc" in Pinnacle) treatments with constant gantry speed and dose rate are feasible without any modifications to the accelerator. Due to the 3 mm-wide mMLC leaves, the use of a 2 mm calculation grid is recommended. When dual arcs are used for the more complex cases, the overall dosimetric agreement for the SmartArc plans compares favorably with the previously reported results for other implementations of VMAT: gamma(3%,3mm) for absolute dose obtained with the biplanar diode array passing rates above 97% with the mean of 98.6%. However, a larger than expected dose error with the single-arc plans, confined predominantly to the isocenter region, requires further investigation.

SU-F-T-352: Development of a Knowledge Based Automatic Lung IMRT Planning Algorithm with Non-Coplanar Beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, W; Wu, Q; Yuan, L

Purpose: To improve the robustness of a knowledge based automatic lung IMRT planning method and to further validate the reliability of this algorithm by utilizing for the planning of clinical cases with non-coplanar beams. Methods: A lung IMRT planning method which automatically determines both plan optimization objectives and beam configurations with non-coplanar beams has been reported previously. A beam efficiency index map is constructed to guide beam angle selection in this algorithm. This index takes into account both the dose contributions from individual beams and the combined effect of multiple beams which is represented by a beam separation score. Wemore » studied the effect of this beam separation score on plan quality and determined the optimal weight for this score.14 clinical plans were re-planned with the knowledge-based algorithm. Significant dosimetric metrics for the PTV and OARs in the automatic plans are compared with those in the clinical plans by the two-sample t-test. In addition, a composite dosimetric quality index was defined to obtain the relationship between the plan quality and the beam separation score. Results: On average, we observed more than 15% reduction on conformity index and homogeneity index for PTV and V{sub 40}, V{sub 60} for heart while an 8% and 3% increase on V{sub 5}, V{sub 20} for lungs, respectively. The variation curve of the composite index as a function of angle spread score shows that 0.6 is the best value for the weight of the beam separation score. Conclusion: Optimal value for beam angle spread score in automatic lung IMRT planning is obtained. With this value, model can result in statistically the “best” achievable plans. This method can potentially improve the quality and planning efficiency for IMRT plans with no-coplanar angles.« less

Preparation and characterization of a novel adsorbent from Moringa oleifera leaf

NASA Astrophysics Data System (ADS)

Bello, Olugbenga Solomon; Adegoke, Kayode Adesina; Akinyunni, Opeyemi Omowumi

2017-06-01

A new and novel adsorbent was obtained by impregnation of Moringa oleifera leaf in H2SO4 and NaOH, respectively. Prepared adsorbents were characterized using elemental analysis, FT-IR, SEM, TGA and EDX analyses, respectively. The effects of operational parameters, such as pH, moisture content, ash content, porosity and iodine number on these adsorbents were investigated and compared with those of commercial activated carbon (CAC). EDX results of acid activated M. oleifera leaf have the highest percentage of carbon by weight (69.40 %) and (76.11 %) by atom, respectively. Proximate analysis showed that the fixed carbon content of acid activated M. oleifera leaf (69.14 ± 0.01) was the highest of all adsorbents studied. Conclusively, the present investigation shows that acid activated M. oleifera leaf is a good alternative adsorbent that could be used in lieu of CAC for recovery of dyes and heavy metal from aqueous solutions and other separation techniques.

Simultaneous separation of three isomeric sennosides from senna leaf (Cassia acutifolia) using counter-current chromatography.

PubMed

Park, Sait Byul; Kim, Yeong Shik

2015-10-01

Senna leaf is widely consumed as tea to treat constipation or to aid in weight loss. Sennoside A, A1 , and B are dirheinanthrone glucosides that are abundant and the bioactive constituents in the plant. They are isomers that refer to the (R*R*), (S*S*), and (R*S*) forms of protons on C-10 and C-10' centers and it is difficult to refine them individually due to their structural similarities. The new separation method using counter-current chromatography successfully purified sennoside A, A1 , and B from senna leaf (Cassia acutifolia) while reversed-phase medium-pressure liquid chromatography yielded sennoside A only. n-Butanol/isopropanol/water (5:1:6, v/v/v) was selected as the solvent system for counter-current chromatography operation, and the partition coefficients were carefully determined by adding different concentrations of formic acid. High-resolution mass spectrometry and NMR spectroscopy were performed to verify the chemical properties of the compounds. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electric tempest in a teacup: The tea leaf analogy to microfluidic blood plasma separation

NASA Astrophysics Data System (ADS)

Yeo, Leslie Y.; Friend, James R.; Arifin, Dian R.

2006-09-01

In a similar fashion to Einstein's tea leaf paradox, the rotational liquid flow induced by ionic wind above a liquid surface can trap suspended microparticles by a helical motion, spinning them down towards a bottom stagnation point. The motion is similar to Batchelor [Q. J. Mech. Appl. Math. 4, 29 (1951)] flows occurring between stationary and rotating disks and arises due to a combination of the primary azimuthal and secondary bulk meridional recirculation that produces a centrifugal and enhanced inward radial force near the chamber bottom. The technology is thus useful for microfluidic particle trapping/concentration; the authors demonstrate its potential for rapid erythrocyte/blood plasma separation for miniaturized medical diagnostic kits.

The WRKY transcription factor family and senescence in switchgrass.

PubMed

Rinerson, Charles I; Scully, Erin D; Palmer, Nathan A; Donze-Reiner, Teresa; Rabara, Roel C; Tripathi, Prateek; Shen, Qingxi J; Sattler, Scott E; Rohila, Jai S; Sarath, Gautam; Rushton, Paul J

2015-11-09

Early aerial senescence in switchgrass (Panicum virgatum) can significantly limit biomass yields. WRKY transcription factors that can regulate senescence could be used to reprogram senescence and enhance biomass yields. All potential WRKY genes present in the version 1.0 of the switchgrass genome were identified and curated using manual and bioinformatic methods. Expression profiles of WRKY genes in switchgrass flag leaf RNA-Seq datasets were analyzed using clustering and network analyses tools to identify both WRKY and WRKY-associated gene co-expression networks during leaf development and senescence onset. We identified 240 switchgrass WRKY genes including members of the RW5 and RW6 families of resistance proteins. Weighted gene co-expression network analysis of the flag leaf transcriptomes across development readily separated clusters of co-expressed genes into thirteen modules. A visualization highlighted separation of modules associated with the early and senescence-onset phases of flag leaf growth. The senescence-associated module contained 3000 genes including 23 WRKYs. Putative promoter regions of senescence-associated WRKY genes contained several cis-element-like sequences suggestive of responsiveness to both senescence and stress signaling pathways. A phylogenetic comparison of senescence-associated WRKY genes from switchgrass flag leaf with senescence-associated WRKY genes from other plants revealed notable hotspots in Group I, IIb, and IIe of the phylogenetic tree. We have identified and named 240 WRKY genes in the switchgrass genome. Twenty three of these genes show elevated mRNA levels during the onset of flag leaf senescence. Eleven of the WRKY genes were found in hotspots of related senescence-associated genes from multiple species and thus represent promising targets for future switchgrass genetic improvement. Overall, individual WRKY gene expression profiles could be readily linked to developmental stages of flag leaves.

Parameterization of Forest Canopies with the PROSAIL Model

NASA Astrophysics Data System (ADS)

Austerberry, M. J.; Grigsby, S.; Ustin, S.

2013-12-01

Particularly in forested environments, arboreal characteristics such as Leaf Area Index (LAI) and Leaf Inclination Angle have a large impact on the spectral characteristics of reflected radiation. The reflected spectrum can be measured directly with satellites or airborne instruments, including the MASTER and AVIRIS instruments. This particular project dealt with spectral analysis of reflected light as measured by AVIRIS compared to tree measurements taken from the ground. Chemical properties of leaves including pigment concentrations and moisture levels were also measured. The leaf data was combined with the chemical properties of three separate trees, and served as input data for a sequence of simulations with the PROSAIL Model, a combination of PROSPECT and Scattering by Arbitrarily Inclined Leaves (SAIL) simulations. The output was a computed reflectivity spectrum, which corresponded to the spectra that were directly measured by AVIRIS for the three trees' exact locations within a 34-meter pixel resolution. The input data that produced the best-correlating spectral output was then cross-referenced with LAI values that had been obtained through two entirely separate methods, NDVI extraction and use of the Beer-Lambert law with airborne LiDAR. Examination with regressive techniques between the measured and modeled spectra then enabled a determination of the trees' probable structure and leaf parameters. Highly-correlated spectral output corresponded well to specific values of LAI and Leaf Inclination Angle. Interestingly, it appears that varying Leaf Angle Distribution has little or no noticeable effect on the PROSAIL model. Not only is the effectiveness and accuracy of the PROSAIL model evaluated, but this project is a precursor to direct measurement of vegetative indices exclusively from airborne or satellite observation.

SU-E-T-602: Patient-Specific Online Dose Verification Based On Transmission Detector Measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thoelking, J; Yuvaraj, S; Jens, F

Purpose: Intensity modulated radiotherapy requires a comprehensive quality assurance program in general and ideally independent verification of dose delivery. Since conventional 2D detector arrays allow only pre-treatment verification, there is a debate concerning the need of online dose verification. This study presents the clinical performance, including dosimetric plan verification in 2D as well as in 3D and the error detection abilities of a new transmission detector (TD) for online dose verification of 6MV photon beam. Methods: To validate the dosimetric performance of the new device, dose reconstruction based on TD measurements were compared to a conventional pre-treatment verification method (reference)more » and treatment planning system (TPS) for 18 IMRT and VMAT treatment plans. Furthermore, dose reconstruction inside the patient based on TD read-out was evaluated by comparing various dose volume indices and 3D gamma evaluations against independent dose computation and TPS. To investigate the sensitivity of the new device, different types of systematic and random errors for leaf positions and linac output were introduced in IMRT treatment sequences. Results: The 2D gamma index evaluation of transmission detector based dose reconstruction showed an excellent agreement for all IMRT and VMAT plans compared to reference measurements (99.3±1.2)% and TPS (99.1±0.7)%. Good agreement was also obtained for 3D dose reconstruction based on TD read-out compared to dose computation (mean gamma value of PTV = 0.27±0.04). Only a minimal dose underestimation within the target volume was observed when analyzing DVH indices (<1%). Positional errors in leaf banks larger than 1mm and errors in linac output larger than 2% could clearly identified with the TD. Conclusion: Since 2D and 3D evaluations for all IMRT and VMAT treatment plans were in excellent agreement with reference measurements and dose computation, the new TD is suitable to qualify for routine treatment plan verification. Funding Support, Disclosures, and Conflict of Interest: COIs: Frank Lohr: Elekta: research grant, travel grants, teaching honoraria IBA: research grant, travel grants, teaching honoraria, advisory board C-Rad: board honoraria, travel grants Frederik Wenz: Elekta: research grant, teaching honoraria, consultant, advisory board Zeiss: research grant, teaching honoraria, patent Hansjoerg Wertz: Elekta: research grant, teaching honoraria IBA: research grant.« less

Spectral reflectance and emissivity features of broad leaf plants: Prospects for remote sensing in the thermal infrared (8.0-14.0 μm)

USGS Publications Warehouse

Ribeiro da Luz, Beatriz; Crowley, James K.

2007-01-01

In contrast to visible and short-wave infrared data, thermal infrared spectra of broad leaf plants show considerable spectral diversity, suggesting that such data eventually could be utilized to map vegetation composition. However, remotely measuring the subtle emissivity features of leaves still presents major challenges. To be successful, sensors operating in the 8–14 μm atmospheric window must have high signal-to-noise and a small enough instantaneous field of view to allow measurements of only a few leaf surfaces. Methods for atmospheric compensation, temperature–emissivity separation, and spectral feature analysis also will need to be refined to allow the recognition, and perhaps, exploitation of leaf thermal infrared spectral properties.

The dosimetric effects of photon energy on the quality of prostate volumetric modulated arc therapy.

PubMed

Mattes, Malcolm D; Tai, Cyril; Lee, Alvin; Ashamalla, Hani; Ikoro, N C

2014-01-01

Studies comparing the dosimetric effects of high- and low-energy photons to treat prostate cancer using 3-dimensional conformal and intensity modulated radiation therapy have yielded mixed results. With the advent of newer radiation delivery systems like volumetric modulated arc therapy (VMAT), the impact of changing photon energy is readdressed. Sixty-five patients treated for prostate cancer at our institution from 2011 to 2012 underwent CT simulation. A target volume encompassing the prostate and entire seminal vesicles was treated to 50.4 Gy, followed by a boost to the prostate and proximal seminal vesicles to a total dose of 81 Gy. The VMAT plans were generated for 6-MV and 10-MV photons under identical optimization conditions using the Eclipse system version 8.6 (Varian Medical Systems, Palo Alto, CA). The analytical anisotropic algorithm was used for all dose calculations. Plans were normalized such that 98% of the planning target volume (PTV) received 100% of the prescribed dose. Dose-volumetric data from the treatment planning system was recorded for both 6-MV and 10-MV plans, which were compared for both the entire cohort and subsets of patients stratified according to the anterior-posterior separation. Plans using 10-MV photons had statistically significantly lower relative integral dose (4.1%), gradient measure (4.1%), skin Dmax (16.9%), monitor units (13.0%), and bladder V(30) (3.1%) than plans using 6-MV photons (P < .05). There was no difference in rectal dose, high-dose-region bladder dose, PTV coverage, or conformity index. The benefit of 10-MV photons was more pronounced for thicker patients (anterior-posterior separation >21 cm) for most parameters, with statistically significant differences in bladder V(30), bladder V(65), integral dose, conformity index, and monitor units. The main dosimetric benefits of 10-MV as compared with 6-MV photons are seen in thicker patients, though for the entire cohort 10-MV plans resulted in a lower integral dose, gradient measure, skin Dmax, monitor units, and bladder V(30), possibly at the expense of higher rectum V(81). Copyright © 2014 American Society for Radiation Oncology. Published by Elsevier Inc. All rights reserved.

Effect of litter, leaf cover and cover of basal internodes of the dominant species Molinia caerulea on seedling recruitment and established vegetation

NASA Astrophysics Data System (ADS)

Janeček, Štěpán; Lepš, Jan

2005-09-01

The effects of litter removal, leaf cover of established plants and cover of basal internodes of a dominant species Molinia caerulea on seedling germination and the dynamics of established plants were studied in a field experiment in an oligotrophic wet meadow. Although the negative influence of litter on total seedling number and seedling species composition was non-significant, litter significantly affected the dynamics of the established vegetation and caused inhibition of total leaf cover development. The effects of total leaf cover of established plants on seedling establishment changed during the vegetation season. Whereas the effect of total leaf cover was positive at the start and in the middle of the vegetation season, at the end the total leaf cover negatively affected seedling establishment. Both total leaf cover and cover of basal internodes affected seedling composition. Effects of these two variables were statistically separable suggesting that they are based on different mechanisms. The response of seedling establishment to these factors was species specific and, consequently, our data support the hypothesis that that biotically generated spatial heterogeneity can promote species co-existence through the differentiation of species regeneration niches.

Controls on declining carbon balance with leaf age among 10 woody species in Australian woodland: do leaves have zero daily net carbon balances when they die?

PubMed

Reich, Peter B; Falster, Daniel S; Ellsworth, David S; Wright, Ian J; Westoby, Mark; Oleksyn, Jacek; Lee, Tali D

2009-01-01

* Here, we evaluated how increased shading and declining net photosynthetic capacity regulate the decline in net carbon balance with increasing leaf age for 10 Australian woodland species. We also asked whether leaves at the age of their mean life-span have carbon balances that are positive, zero or negative. * The net carbon balances of 2307 leaves on 53 branches of the 10 species were estimated. We assessed three-dimensional architecture, canopy openness, photosynthetic light response functions and dark respiration rate across leaf age sequences on all branches. We used YPLANT to estimate light interception and to model carbon balance along the leaf age sequences. * As leaf age increased to the mean life-span, increasing shading and declining photosynthetic capacity each separately reduced daytime carbon gain by approximately 39% on average across species. Together, they reduced daytime carbon gain by 64% on average across species. * At the age of their mean life-span, almost all leaves had positive daytime carbon balances. These per leaf carbon surpluses were of a similar magnitude to the estimated whole-plant respiratory costs per leaf. Thus, the results suggest that a whole-plant economic framework, including respiratory costs, may be useful in assessing controls on leaf longevity.

Study on beta-galactosidase enzymatic activity of herbal yogurt.

PubMed

Chowdhury, Banani Ray; Chakraborty, Runu; Raychaudhuri, Utpal

2008-03-01

Different types of herbal yogurts were developed by mixing standardized milk with pretreated herbs, namely tulsi leaf (Ocimum sanctum), pudina leaf (Mentha arvensis) and coriander leaf (Coriandrum sativum), with leaves separately and a 1:1 (v/v) mixture of the strains of lactic starter cultures---Lactobacillus acidophilus (NCIM 2903) and Lactobacillus plantarum (NCIM 2083)-followed by incubation at 40 degrees C for 6 h. The beta-galactosidase enzymatic activity of the abovementioned herbal yogurts was determined and interestingly noted to exhibit higher enzymatic activity compared with the control yogurt (without any herbs). Among all herbal yogurts, tulsi yogurt had the maximum beta-galactosidase activity.

VMAT optimization with dynamic collimator rotation.

PubMed

Lyu, Qihui; O'Connor, Daniel; Ruan, Dan; Yu, Victoria; Nguyen, Dan; Sheng, Ke

2018-04-16

Although collimator rotation is an optimization variable that can be exploited for dosimetric advantages, existing Volumetric Modulated Arc Therapy (VMAT) optimization uses a fixed collimator angle in each arc and only rotates the collimator between arcs. In this study, we develop a novel integrated optimization method for VMAT, accounting for dynamic collimator angles during the arc motion. Direct Aperture Optimization (DAO) for Dynamic Collimator in VMAT (DC-VMAT) was achieved by adding to the existing dose fidelity objective an anisotropic total variation term for regulating the fluence smoothness, a binary variable for forming simple apertures, and a group sparsity term for controlling collimator rotation. The optimal collimator angle for each beam angle was selected using the Dijkstra's algorithm, where the node costs depend on the estimated fluence map at the current iteration and the edge costs account for the mechanical constraints of multi-leaf collimator (MLC). An alternating optimization strategy was implemented to solve the DAO and collimator angle selection (CAS). Feasibility of DC-VMAT using one full-arc with dynamic collimator rotation was tested on a phantom with two small spherical targets, a brain, a lung and a prostate cancer patient. The plan was compared against a static collimator VMAT (SC-VMAT) plan using three full arcs with 60 degrees of collimator angle separation in patient studies. With the same target coverage, DC-VMAT achieved 20.3% reduction of R50 in the phantom study, and reduced the average max and mean OAR dose by 4.49% and 2.53% of the prescription dose in patient studies, as compared with SC-VMAT. The collimator rotation co-ordinated with the gantry rotation in DC-VMAT plans for deliverability. There were 13 beam angles in the single-arc DC-VMAT plan in patient studies that requires slower gantry rotation to accommodate multiple collimator angles. The novel DC-VMAT approach utilizes the dynamic collimator rotation during arc delivery. In doing so, DC-VMAT affords more sophisticated intensity modulation, alleviating the limitation previously imposed by the square beamlet from the MLC leaf thickness and achieves higher effective modulation resolution. Consequently, DC-VMAT with a single arc manages to achieve superior dosimetry than SC-VMAT with three full arcs. © 2018 American Association of Physicists in Medicine.

The hydrostatic gradient, not light availability, drives height-related variation in Sequoia sempervirens (Cupressaceae) leaf anatomy.

PubMed

Oldham, Alana R; Sillett, Stephen C; Tomescu, Alexandru M F; Koch, George W

2010-07-01

Leaves at the tops of most trees are smaller, thicker, and in many other ways different from leaves on the lowermost branches. This height-related variation in leaf structure has been explained as acclimation to differing light environments and, alternatively, as a consequence of hydrostatic, gravitational constraints on turgor pressure that reduce leaf expansion. • To separate hydrostatic effects from those of light availability, we used anatomical analysis of height-paired samples from the inner and outer tree crowns of tall redwoods (Sequoia sempervirens). • Height above the ground correlates much more strongly with leaf anatomy than does light availability. Leaf length, width, and mesophyll porosity all decrease linearly with height and help explain increases in leaf-mass-to-area ratio and decreases in both photosynthetic capacity and internal gas-phase conductance with increasing height. Two functional traits-leaf thickness and transfusion tissue-also increase with height and may improve water-stress tolerance. Transfusion tissue area increases enough that whole-leaf vascular volume does not change significantly with height in most trees. Transfusion tracheids become deformed with height, suggesting they may collapse under water stress and act as a hydraulic buffer that improves leaf water status and reduces the likelihood of xylem dysfunction. • That such variation in leaf structure may be caused more by gravity than by light calls into question use of the terms "sun" and "shade" to describe leaves at the tops and bottoms of tall tree crowns.

Assessment of Agroforestry Trees in Dry-land Savanna Supports Ecohydrologic Separation

NASA Astrophysics Data System (ADS)

Ceperley, Natalie; Mande, Theophile; Van de Giesen, Nick; Tyler, Scott; Parlange, Marc

2016-04-01

We use stable isotopes of water to demonstrate the ecohydrologic separation, or the plant controlled compartmentalization, of different water sources in a catchment in South Eastern Burkina Faso. We analyze water extracted from the groundwater, stream water, precipitation, perched aquifer, xylem water of agroforestry trees, and sub-canopy soil water over a 6 year period to explore how the separation affects different components of the system over time. The ratio between deuterium and O18 allows us to assess whether the water that plants use is the same as the water that recharges the aquifer and runs off in the stream. Water extracted from the tree at leaf out in February corresponded to deuterium and O18 concentrations of the groundwater, a drop from its dry season, enriched, levels which mimicked the soil water. Examination of the isotopic signature suggests that the size of tree plays an important role in duration and timing of this leaf-out as well as the degree of enrichment during the peak of the dry season. Dates of leaf out were confirmed by analyzing sub-canopy radiation and photographs. Water extracted from roots suggests that the trees are performing hydraulic redistribution, or lifting the ground water and 'sharing it' with the rooting zone soil during the dry season. The enriched level of xylem, in this case, is a product of water loss and enrichment along the travel path of the water from the roots to the tip of the branch, as evidenced by the variation according to size of tree. Vapor pressure deficit, sap flow, soil water, and soil moisture interactions support this picture of interacting controls, separate from hydrologic triggers on the water movement in the tree. A second round of sampling focused on the leaf out period by extracting and analyzing stem water from throughout the canopy during the leaf out. Simultaneous large eddy correlation revealed high levels of latent energy flux, even during the dry season. Our isotope analysis allowed us to conclude that tree level transpiration explains this discrepancy since it does not access the same reservoirs of water as the rest of the catchment. Most current land surface models do not differentiate between different reservoirs of water.

SU-E-T-331: Dosimetric Impact of Multileaf Collimator Leaf Width On Stereotactic Radiosurgery (SRS) RapidArc Treatment Plans for Single and Multiple Brain Metastases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hossain, S; Keeling, V; Ahmad, S

Purpose: To determine the effects of multileaf collimator (MLC) leaf width on normal-brain-tissue doses and dose conformity of SRS RapidArc treatment plans for brain tumors. Methods: Ten patients with 24 intracranial tumors (seven with 1–2 and three with 4–6 lesions) were planned using RapidArc for both Varian Millennium 120 MLC (5 mm leaf width) and high definition (HD) MLC (2.5 mm leaf width). Between 2 and 8 arcs were used with two full coplanar arcs and the rest non-coplanar half arcs. 6 MV beams were used and plans were optimized with a high priority to the Normal Tissue Objective (tomore » achieve dose conformity and sharp dose fall-off) and normal brain tissue. Calculation was done using AAA on a 1 mm grid size. The prescription dose ranged from 14–22 Gy. Plans were normalized such that 99% of the target received the prescription dose. Identical beam geometries, optimizations, calculations, and normalizations were used for both plans. Paddick Conformity Index (PCI), V4, V8 and V12 Gy for normal brain tissue and Integral Dose were used for analysis. Results: In all cases, HD MLC plans performed better in sparing normal brain tissue, achieving a higher PCI with a lower Integral Dose. The average PCI for all 24 targets was 0.75±0.23 and 0.70±0.23 (p ≤0.0015) for HD MLC and Millennium MLC plans, respectively. The average ratio of normal brain doses for Millennium MLC to HD MLC plans was 1.30±0.16, 1.27±0.15, and 1.31±0.18 for the V4, V8, and V12, respectively. The differences in normal brain dose for all criteria were statistically significant with p-value < 0.02. On average Millennium MLC plans had a 16% higher integral dose than HD MLC plans. Conclusion: Significantly better dose conformity with reduced volume of normal brain tissue and integral dose was achieved with HD MLC plans compared to Millennium MLC plans.« less

Dosimetric predictors of radiation-induced pericardial effusion in esophageal cancer.

PubMed

Ogino, Ichiro; Watanabe, Shigenobu; Sakamaki, Kentaro; Ogino, Yuka; Kunisaki, Chikara; Kimura, Kazuo

2017-07-01

To evaluate the dose-volume parameters of the pericardium and heart in order to reduce the risk of radiation-induced pericardial effusion (PE) and symptomatic PE (SPE) in esophageal cancer patients treated with concurrent chemoradiotherapy. In 86 of 303 esophageal cancer patients, follow-up CT was obtained at least 24 months after concurrent chemoradiotherapy. Correlations between clinical factors, including risk factors for cardiac disease, dosimetric factors, and the incidence of PE and SPE after radiotherapy were analyzed using Cox proportional hazard regression analysis. Significant dosimetric factors with the highest hazard ratios were investigated using zones separated according to their distance from esophagus. PE developed in 49 patients. Univariate analysis showed the mean heart dose, heart V 5 -V 55 , mean pericardium dose, and pericardium V 5 -V 50 to all significantly affect the incidence of PE. Additionally, body surface area was correlated with the incidence of PE in multivariate analysis. Grade 3 and 4 SPE developed in 5 patients. The pericardium V 50 and pericardium D 10 significantly affected the incidence of SPE. The pericardium V 50 in patients with SPE ranged from 17.1 to 21.7%. Factors affecting the incidence of SPE were the V 50 of the pericardium zones within 3 cm and 4 cm of the esophagus. A wide range of radiation doses to the heart and pericardium were related to the incidence of PE. A pericardium V 50  ≤ 17% is important to avoid symptomatic PE in esophageal cancer patients treated with concurrent chemoradiotherapy.

Application of mixed cloud point extraction for the analysis of six flavonoids in Apocynum venetum leaf samples by high performance liquid chromatography.

PubMed

Zhou, Jun; Sun, Jiang Bing; Xu, Xin Yu; Cheng, Zhao Hui; Zeng, Ping; Wang, Feng Qiao; Zhang, Qiong

2015-03-25

A simple, inexpensive and efficient method based on the mixed cloud point extraction (MCPE) combined with high performance liquid chromatography was developed for the simultaneous separation and determination of six flavonoids (rutin, hyperoside, quercetin-3-O-sophoroside, isoquercitrin, astragalin and quercetin) in Apocynum venetum leaf samples. The non-ionic surfactant Genapol X-080 and cetyl-trimethyl ammonium bromide (CTAB) was chosen as the mixed extracting solvent. Parameters that affect the MCPE processes, such as the content of Genapol X-080 and CTAB, pH, salt content, extraction temperature and time were investigated and optimized. Under the optimized conditions, the calibration curve for six flavonoids were all linear with the correlation coefficients greater than 0.9994. The intra-day and inter-day precision (RSD) were below 8.1% and the limits of detection (LOD) for the six flavonoids were 1.2-5.0 ng mL(-1) (S/N=3). The proposed method was successfully used to separate and determine the six flavonoids in A. venetum leaf samples. Copyright © 2015 Elsevier B.V. All rights reserved.

Automated Analysis of Barley Organs Using 3D Laser Scanning: An Approach for High Throughput Phenotyping

PubMed Central

Paulus, Stefan; Dupuis, Jan; Riedel, Sebastian; Kuhlmann, Heiner

2014-01-01

Due to the rise of laser scanning the 3D geometry of plant architecture is easy to acquire. Nevertheless, an automated interpretation and, finally, the segmentation into functional groups are still difficult to achieve. Two barley plants were scanned in a time course, and the organs were separated by applying a histogram-based classification algorithm. The leaf organs were represented by meshing algorithms, while the stem organs were parameterized by a least-squares cylinder approximation. We introduced surface feature histograms with an accuracy of 96% for the separation of the barley organs, leaf and stem. This enables growth monitoring in a time course for barley plants. Its reliability was demonstrated by a comparison with manually fitted parameters with a correlation R2 = 0.99 for the leaf area and R2 = 0.98 for the cumulated stem height. A proof of concept has been given for its applicability for the detection of water stress in barley, where the extension growth of an irrigated and a non-irrigated plant has been monitored. PMID:25029283

SU-E-T-367: Optimization of DLG Using TG-119 Test Cases and a Weighted Mean Approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sintay, B; Vanderstraeten, C; Terrell, J

2014-06-01

Purpose: Optimization of the dosimetric leaf gap (DLG) is an important step in commissioning the Eclipse treatment planning system for sliding window intensity-modulated radiation therapy (SW-IMRT) and RapidArc. Often the values needed for optimal dose delivery differ markedly from those measured at commissioning. We present a method to optimize this value using the AAPM TG-119 test cases. Methods: For SW-IMRT and RapidArc, TG-119 based test plans were created using a water-equivalent phantom. Dose distributions measured on film and ion chamber (IC) readings taken in low-gradient regions within the targets were analyzed separately. Since DLG is a single value per energy,more » SW-IMRT and RapidArc must be considered simultaneously. Plans were recalculated using a linear sweep from 0.02cm (the minimum DLG) to 0.3 cm. The calculated point doses were compared to the measured doses for each plan, and based on these comparisons an optimal DLG value was computed for each plan. TG-119 cases are designed to push the system in various ways, thus, a weighted mean of the DLG was computed where the relative importance of each type of plan was given a score from 0.0 to 1.0. Finally, SW-IMRT and RapidArc are assigned an overall weight based on clinical utilization. Our routine patient-QA (PQA) process was performed as independent validation. Results: For a Varian TrueBeam, the optimized DLG varied with σ = 0.044cm for SW-IMRT and σ = 0.035cm for RapidArc. The difference between the weighted mean SW-IMRT and RapidArc value was 0.038cm. We predicted utilization of 25% SW-IMRT and 75% RapidArc. The resulting DLG was ~1mm different than that found by commissioning and produced an average error of <1% for SW-IMRT and RapidArc PQA test cases separately. Conclusion: The weighted mean method presented is a useful tool for determining an optimal DLG value for commissioning Eclipse.« less

Contura Multi-Lumen Balloon breast brachytherapy catheter: comparative dosimetric findings of a phase 4 trial.

PubMed

Arthur, Douglas W; Vicini, Frank A; Todor, Dorin A; Julian, Thomas B; Cuttino, Laurie W; Mukhopadhyay, Nitai D

2013-06-01

Final dosimetric findings of a completed, multi-institutional phase 4 registry trial using the Contura Multi-Lumen Balloon (MLB) breast brachytherapy catheter to deliver accelerated partial breast irradiation (APBI) in patients with early-stage breast cancer are presented. Three dosimetric plans with identical target coverage were generated for each patient for comparison: multilumen multidwell (MLMD); central-lumen multidwell (CLMD); and central-lumen single-dwell (CLSD) loading of the Contura catheter. For this study, a successful treatment plan achieved ideal dosimetric goals and included the following: ≥ 95% of the prescribed dose (PD) covering ≥ 95% of the target volume (TV); maximum skin dose ≤ 125% of the PD; maximum rib dose ≤ 145% of the PD; and V150 ≤50 cc and V200 ≤ 10 cc. Between January 2008 and February 2011, 23 institutions participated. A total of 318 patients were available for dosimetric review. Using the Contura MLB, all dosimetric criteria were met in 78.93% of cases planned with MLMD versus 55.38% with the CLMD versus 37.66% with the CLSD (P ≤.0001). Evaluating all patients with the full range of skin to balloon distance represented, median maximum skin dose was reduced by 12% and median maximum rib dose by 13.9% when using MLMD-based dosimetric plans compared to CLSD. The dosimetric benefit of MLMD was further demonstrated in the subgroup of patients where skin thickness was <5 mm, where MLMD use allowed a 38% reduction in median maximum skin dose over CLSD. For patients with rib distance <5 mm, the median maximum rib dose reduction was 27%. Use of the Contura MLB catheter produced statistically significant improvements in dosimetric capabilities between CLSD and CLMD treatments. This device approach demonstrates the ability not only to overcome the barriers of limited skin thickness and close rib proximity, but to consistently achieve a higher standard of dosimetric planning goals. Copyright © 2013 Elsevier Inc. All rights reserved.

Contura Multi-Lumen Balloon Breast Brachytherapy Catheter: Comparative Dosimetric Findings of a Phase 4 Trial

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arthur, Douglas W., E-mail: darthur@mcvh-vcu.edu; Vicini, Frank A.; Todor, Dorin A.

2013-06-01

Purpose: Final dosimetric findings of a completed, multi-institutional phase 4 registry trial using the Contura Multi-Lumen Balloon (MLB) breast brachytherapy catheter to deliver accelerated partial breast irradiation (APBI) in patients with early-stage breast cancer are presented. Methods and Materials: Three dosimetric plans with identical target coverage were generated for each patient for comparison: multilumen multidwell (MLMD); central-lumen multidwell (CLMD); and central-lumen single-dwell (CLSD) loading of the Contura catheter. For this study, a successful treatment plan achieved ideal dosimetric goals and included the following: ≥95% of the prescribed dose (PD) covering ≥95% of the target volume (TV); maximum skin dose ≤125%more » of the PD; maximum rib dose ≤145% of the PD; and V150 ≤50 cc and V200 ≤10 cc. Results: Between January 2008 and February 2011, 23 institutions participated. A total of 318 patients were available for dosimetric review. Using the Contura MLB, all dosimetric criteria were met in 78.93% of cases planned with MLMD versus 55.38% with the CLMD versus 37.66% with the CLSD (P≤.0001). Evaluating all patients with the full range of skin to balloon distance represented, median maximum skin dose was reduced by 12% and median maximum rib dose by 13.9% when using MLMD-based dosimetric plans compared to CLSD. The dosimetric benefit of MLMD was further demonstrated in the subgroup of patients where skin thickness was <5 mm, where MLMD use allowed a 38% reduction in median maximum skin dose over CLSD. For patients with rib distance <5 mm, the median maximum rib dose reduction was 27%. Conclusions: Use of the Contura MLB catheter produced statistically significant improvements in dosimetric capabilities between CLSD and CLMD treatments. This device approach demonstrates the ability not only to overcome the barriers of limited skin thickness and close rib proximity, but to consistently achieve a higher standard of dosimetric planning goals.« less

Laboratory investigations of the trail-following responses of four species of leaf-cutting ants with notes on the specificity of a trail pheromone of Atta texana (Buckley)

Treesearch

S. W. Robinson; John C. Moser; M. S. Blum; E. Amante

1974-01-01

Interspecific trail following activity of poison sac contents from four species of leaf-cutting ants was investigated. with only one exception, all the species teste followed trails made from each others poison sac contents. however when the ants were given a choice of following one of two separate trails, clear differences were shown in the poison sac contents of the...

Vinca drug components accumulate exclusively in leaf exudates of Madagascar periwinkle

PubMed Central

Roepke, Jonathan; Salim, Vonny; Wu, Maggie; Thamm, Antje M. K.; Murata, Jun; Ploss, Kerstin; Boland, Wilhelm; De Luca, Vincenzo

2010-01-01

The monoterpenoid indole alkaloids (MIAs) of Madagascar periwinkle (Catharanthus roseus) continue to be the most important source of natural drugs in chemotherapy treatments for a range of human cancers. These anticancer drugs are derived from the coupling of catharanthine and vindoline to yield powerful dimeric MIAs that prevent cell division. However the precise mechanisms for their assembly within plants remain obscure. Here we report that the complex development-, environment-, organ-, and cell-specific controls involved in expression of MIA pathways are coupled to secretory mechanisms that keep catharanthine and vindoline separated from each other in living plants. Although the entire production of catharanthine and vindoline occurs in young developing leaves, catharanthine accumulates in leaf wax exudates of leaves, whereas vindoline is found within leaf cells. The spatial separation of these two MIAs provides a biological explanation for the low levels of dimeric anticancer drugs found in the plant that result in their high cost of commercial production. The ability of catharanthine to inhibit the growth of fungal zoospores at physiological concentrations found on the leaf surface of Catharanthus leaves, as well as its insect toxicity, provide an additional biological role for its secretion. We anticipate that this discovery will trigger a broad search for plants that secrete alkaloids, the biological mechanisms involved in their secretion to the plant surface, and the ecological roles played by them. PMID:20696903

Isolation of Mesophyll Cells and Bundle Sheath Cells from Digitaria sanguinalis (L.) Scop. Leaves and a Scanning Microscopy Study of the Internal Leaf Cell Morphology 1

PubMed Central

Edwards, Gerald E.; Black, Clanton C.

1971-01-01

A technique is described for the separation of mesophyll and bundle sheath cells from Digitaria sanguinalis leaves and evidence for separation is given with light and scanning electron micrographs. Gentle grinding of fully differentiated leaves in a mortar releases mesophyll cells which are isolated on nylon nets by filtration. More extensive grinding of the remaining tissue yields bundle sheath strands which are isolated by filtration with stainless steel sieves and nylon nets. Further grinding of bundle sheath strands in a tissue homogenizer releases bundle sheath cells which are collected on nylon nets. Percentage of purity derived from cell counts and yield data on a chlorophyll basis are given. The internal leaf cell morphology is presented in scanning electron micrographs and compared with light micrographs of fully-differentiated D. sanguinalis leaves. In leaves of plants which possess the C4-dicarboxylic acid cycle of photosynthesis, the relationship of leaf morphology to photosynthesis in mesophyll and bundle sheath cells is considered, and the hypothesis is presented that as atmospheric CO2 enters a leaf about 85% is fixed by the C4-dicarboxylic acid cycle in the mesophyll cells and 10 to 15% is fixed by the reductive pentose phosphate cycle in the bundle sheath cells. A technique also is given for the isolation of mesophyll cells from spinach leaves. Images PMID:16657571

Isolation of Mesophyll Cells and Bundle Sheath Cells from Digitaria sanguinalis (L.) Scop. Leaves and a Scanning Microscopy Study of the Internal Leaf Cell Morphology.

PubMed

Edwards, G E; Black, C C

1971-01-01

A technique is described for the separation of mesophyll and bundle sheath cells from Digitaria sanguinalis leaves and evidence for separation is given with light and scanning electron micrographs. Gentle grinding of fully differentiated leaves in a mortar releases mesophyll cells which are isolated on nylon nets by filtration. More extensive grinding of the remaining tissue yields bundle sheath strands which are isolated by filtration with stainless steel sieves and nylon nets. Further grinding of bundle sheath strands in a tissue homogenizer releases bundle sheath cells which are collected on nylon nets. Percentage of purity derived from cell counts and yield data on a chlorophyll basis are given.The internal leaf cell morphology is presented in scanning electron micrographs and compared with light micrographs of fully-differentiated D. sanguinalis leaves. In leaves of plants which possess the C(4)-dicarboxylic acid cycle of photosynthesis, the relationship of leaf morphology to photosynthesis in mesophyll and bundle sheath cells is considered, and the hypothesis is presented that as atmospheric CO(2) enters a leaf about 85% is fixed by the C(4)-dicarboxylic acid cycle in the mesophyll cells and 10 to 15% is fixed by the reductive pentose phosphate cycle in the bundle sheath cells.A technique also is given for the isolation of mesophyll cells from spinach leaves.

Separation of abscission zone cells in detached Azolla roots depends on apoplastic pH.

PubMed

Fukuda, Kazuma; Yamada, Yoshiya; Miyamoto, Kensuke; Ueda, Junichi; Uheda, Eiji

2013-01-01

In studies on the mechanism of cell separation during abscission, little attention has been paid to the apoplastic environment. We found that the apoplastic pH surrounding abscission zone cells in detached roots of the water fern Azolla plays a major role in cell separation. Abscission zone cells of detached Azolla roots were separated rapidly in a buffer at neutral pH and slowly in a buffer at pH below 4.0. However, cell separation rarely occurred at pH 5.0-5.5. Light and electron microscopy revealed that cell separation was caused by a degradation of the middle lamella between abscission zone cells at both pH values, neutral and below 4.0. Low temperature and papain treatment inhibited cell separation. Enzyme(s) in the cell wall of the abscission zone cells might be involved in the degradation of the pectin of the middle lamella and the resultant, pH-dependent cell separation. By contrast, in Phaseolus leaf petioles, unlike Azolla roots, cell separation was slow and increased only at acidic pH. The rapid cell separation, as observed in Azolla roots at neutral pH, did not occur. Indirect immunofluorescence microscopy, using anti-pectin monoclonal antibodies, revealed that the cell wall pectins of the abscission zone cells of Azolla roots and Phaseolus leaf petioles looked similar and changed similarly during cell separation. Thus, the pH-related differences in cell separation mechanisms of Azolla and Phaseolus might not be due to differences in cell wall pectin, but to differences in cell wall-located enzymatic activities responsible for the degradation of pectic substances. A possible enzyme system is discussed. Copyright © 2012 Elsevier GmbH. All rights reserved.

A Physiological and Behavioral Mechanism for Leaf Herbivore-Induced Systemic Root Resistance1[OPEN

PubMed Central

Erb, Matthias; Robert, Christelle A.M.; Marti, Guillaume; Lu, Jing; Doyen, Gwladys R.; Villard, Neil; Barrière, Yves; Wolfender, Jean-Luc; Turlings, Ted C.J.

2015-01-01

Indirect plant-mediated interactions between herbivores are important drivers of community composition in terrestrial ecosystems. Among the most striking examples are the strong indirect interactions between spatially separated leaf- and root-feeding insects sharing a host plant. Although leaf feeders generally reduce the performance of root herbivores, little is known about the underlying systemic changes in root physiology and the associated behavioral responses of the root feeders. We investigated the consequences of maize (Zea mays) leaf infestation by Spodoptera littoralis caterpillars for the root-feeding larvae of the beetle Diabrotica virgifera virgifera, a major pest of maize. D. virgifera strongly avoided leaf-infested plants by recognizing systemic changes in soluble root components. The avoidance response occurred within 12 h and was induced by real and mimicked herbivory, but not wounding alone. Roots of leaf-infested plants showed altered patterns in soluble free and soluble conjugated phenolic acids. Biochemical inhibition and genetic manipulation of phenolic acid biosynthesis led to a complete disappearance of the avoidance response of D. virgifera. Furthermore, bioactivity-guided fractionation revealed a direct link between the avoidance response of D. virgifera and changes in soluble conjugated phenolic acids in the roots of leaf-attacked plants. Our study provides a physiological mechanism for a behavioral pattern that explains the negative effect of leaf attack on a root-feeding insect. Furthermore, it opens up the possibility to control D. virgifera in the field by genetically mimicking leaf herbivore-induced changes in root phenylpropanoid patterns. PMID:26430225

DOE Office of Scientific and Technical Information (OSTI.GOV)

Teng, C; Janssens, G; Ainsley, C

Purpose: Proton dose distribution is sensitive to tumor regression and tissue and normal anatomy changes. Replanning is sometimes necessary during treatment to ensure continue tumor coverage or avoid overtreatment of organs at risk (OARs). We investigated action thresholds for replanning and identified both dosimetric and non-dosimetric metrics that would predict a need for replan. Methods: All consecutive lung cancer patients (n = 188) who received definitive proton radiotherapy and had more than two evaluation CT scans at the Roberts Proton Therapy Center (Philadelphia, USA) from 2011 to 2015 were included in this study. The cohort included a variety of tumormore » sizes, locations, histology, beam angles, as well as radiation-induced tumor and lung change. Dosimetric changes during therapy were characterized by changes in the dose volume distribution of PTV, ITV, and OARs (heart, cord, esophagus, brachial plexus and lungs). Tumor and lung change were characterized by changes in sizes, and in the distribution of Hounsfield numbers and water equivalent thickness (WET) along the beam path. We applied machine learning tools to identify both dosimetric and non-dosimetric metrics that predicted a replan. Results: Preliminary data showed that clinical indicators (n = 54) were highly correlated; thus, a simple indicator may be derived to guide the action threshold for replanning. Additionally, tumor regression alone could not predict dosimetric changes in OARs; it required further information about beam angles and tumor locations. Conclusion: Both dosimetric and non-dosimetric factors are predictive of the need for replanning during proton treatment.« less

Genomic Dissection of Leaf Angle in Maize (Zea mays L.) Using a Four-Way Cross Mapping Population.

PubMed

Ding, Junqiang; Zhang, Luyan; Chen, Jiafa; Li, Xiantang; Li, Yongming; Cheng, Hongliang; Huang, Rongrong; Zhou, Bo; Li, Zhimin; Wang, Jiankang; Wu, Jianyu

2015-01-01

Increasing grain yield by the selection for optimal plant architecture has been the key focus in modern maize breeding. As a result, leaf angle, an important determinant of plant architecture, has been significantly improved to adapt to the ever-increasing plant density in maize production over the past several decades. To extend our understanding on the genetic mechanisms of leaf angle in maize, we developed the first four-way cross mapping population, consisting of 277 lines derived from four maize inbred lines with varied leaf angles. The four-way cross mapping population together with the four parental lines were evaluated for leaf angle in two environments. In this study, we reported linkage maps built in the population and quantitative trait loci (QTL) on leaf angle detected by inclusive composite interval mapping (ICIM). ICIM applies a two-step strategy to effectively separate the cofactor selection from the interval mapping, which controls the background additive and dominant effects at the same time. A total of 14 leaf angle QTL were identified, four of which were further validated in near-isogenic lines (NILs). Seven of the 14 leaf angle QTL were found to overlap with the published leaf angle QTL or genes, and the remaining QTL were unique to the four-way population. This study represents the first example of QTL mapping using a four-way cross population in maize, and demonstrates that the use of specially designed four-way cross is effective in uncovering the basis of complex and polygenetic trait like leaf angle in maize.

Genomic Dissection of Leaf Angle in Maize (Zea mays L.) Using a Four-Way Cross Mapping Population

PubMed Central

Li, Xiantang; Li, Yongming; Cheng, Hongliang; Huang, Rongrong; Zhou, Bo; Li, Zhimin; Wang, Jiankang; Wu, Jianyu

2015-01-01

Increasing grain yield by the selection for optimal plant architecture has been the key focus in modern maize breeding. As a result, leaf angle, an important determinant of plant architecture, has been significantly improved to adapt to the ever-increasing plant density in maize production over the past several decades. To extend our understanding on the genetic mechanisms of leaf angle in maize, we developed the first four-way cross mapping population, consisting of 277 lines derived from four maize inbred lines with varied leaf angles. The four-way cross mapping population together with the four parental lines were evaluated for leaf angle in two environments. In this study, we reported linkage maps built in the population and quantitative trait loci (QTL) on leaf angle detected by inclusive composite interval mapping (ICIM). ICIM applies a two-step strategy to effectively separate the cofactor selection from the interval mapping, which controls the background additive and dominant effects at the same time. A total of 14 leaf angle QTL were identified, four of which were further validated in near-isogenic lines (NILs). Seven of the 14 leaf angle QTL were found to overlap with the published leaf angle QTL or genes, and the remaining QTL were unique to the four-way population. This study represents the first example of QTL mapping using a four-way cross population in maize, and demonstrates that the use of specially designed four-way cross is effective in uncovering the basis of complex and polygenetic trait like leaf angle in maize. PMID:26509792

The leaf angle distribution of natural plant populations: assessing the canopy with a novel software tool.

PubMed

Müller-Linow, Mark; Pinto-Espinosa, Francisco; Scharr, Hanno; Rascher, Uwe

2015-01-01

Three-dimensional canopies form complex architectures with temporally and spatially changing leaf orientations. Variations in canopy structure are linked to canopy function and they occur within the scope of genetic variability as well as a reaction to environmental factors like light, water and nutrient supply, and stress. An important key measure to characterize these structural properties is the leaf angle distribution, which in turn requires knowledge on the 3-dimensional single leaf surface. Despite a large number of 3-d sensors and methods only a few systems are applicable for fast and routine measurements in plants and natural canopies. A suitable approach is stereo imaging, which combines depth and color information that allows for easy segmentation of green leaf material and the extraction of plant traits, such as leaf angle distribution. We developed a software package, which provides tools for the quantification of leaf surface properties within natural canopies via 3-d reconstruction from stereo images. Our approach includes a semi-automatic selection process of single leaves and different modes of surface characterization via polygon smoothing or surface model fitting. Based on the resulting surface meshes leaf angle statistics are computed on the whole-leaf level or from local derivations. We include a case study to demonstrate the functionality of our software. 48 images of small sugar beet populations (4 varieties) have been analyzed on the base of their leaf angle distribution in order to investigate seasonal, genotypic and fertilization effects on leaf angle distributions. We could show that leaf angle distributions change during the course of the season with all varieties having a comparable development. Additionally, different varieties had different leaf angle orientation that could be separated in principle component analysis. In contrast nitrogen treatment had no effect on leaf angles. We show that a stereo imaging setup together with the appropriate image processing tools is capable of retrieving the geometric leaf surface properties of plants and canopies. Our software package provides whole-leaf statistics but also a local estimation of leaf angles, which may have great potential to better understand and quantify structural canopy traits for guided breeding and optimized crop management.

Modeling the influence of leaf demography on remotely sensed data using DART and PROSPECT-D

NASA Astrophysics Data System (ADS)

Feret, J. B.; Grau, E.; Barbier, N.; Berveiller, D.; Chave, J.; Durrieu, S.; Gastellu-Etchegorry, J. P.; Hmimina, G.; Lefèvre-Fonollosa, M. J.; Proisy, C.; Soudani, K.; Vincent, G.

2016-12-01

The seasonality of Amazon forest productivity and photosynthetic activity has recently been investigated under a new perspective by a series of publications. The debate about possible factors explaining this seasonality is vivid, and the possibility of several hypotheses has been tested, including canopy phenology and leaf demography, and changes in illumination geometry combined with the complex 3D structure of the canopy. A manifold of measurements and techniques have been used to test these hypotheses, including field observations of leaf demography from ground measured litterfall and phenocam, airborne and satellite remote sensing and 3 dimensional radiative transfer modeling. Our study explores the relative influence of leaf demography and illumination geometry on remotely sensed data. To achieve this, we take advantage of the latest advances in the domain of physical modeling at both leaf and canopy scale. The leaf optical properties model PROSPECT-D was used to model leaf optical properties at various growth stages based on field observations and theoretical leaf biochemical composition during its development and senescence. The 3-dimensional radiative transfer model DART was used to simulate various levels of complexity of canopy covers, from a turbid layer to complex canopy derived from airborne LiDAR acquisitions. Data for leaf demography and ontogeny taken from recent publications was used and integrated into canopy simulations corresponding to year-long observations. Data acquisitions were performed in the frame of the HyperTropik project, funded by CNES, Our results focus on analyzing the influence of separated and combined factors such as illumination geometry, leaf biochemistry and leaf demography on various spectral attributes, including Enhanced vegetation index and hyperspectral metrics.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lafata, K; Ren, L; Wu, Q

Purpose: To develop a data-mining methodology based on quantum clustering and machine learning to predict expected dosimetric endpoints for lung SBRT applications based on patient-specific anatomic features. Methods: Ninety-three patients who received lung SBRT at our clinic from 2011–2013 were retrospectively identified. Planning information was acquired for each patient, from which various features were extracted using in-house semi-automatic software. Anatomic features included tumor-to-OAR distances, tumor location, total-lung-volume, GTV and ITV. Dosimetric endpoints were adopted from RTOG-0195 recommendations, and consisted of various OAR-specific partial-volume doses and maximum point-doses. First, PCA analysis and unsupervised quantum-clustering was used to explore the feature-space tomore » identify potentially strong classifiers. Secondly, a multi-class logistic regression algorithm was developed and trained to predict dose-volume endpoints based on patient-specific anatomic features. Classes were defined by discretizing the dose-volume data, and the feature-space was zero-mean normalized. Fitting parameters were determined by minimizing a regularized cost function, and optimization was performed via gradient descent. As a pilot study, the model was tested on two esophageal dosimetric planning endpoints (maximum point-dose, dose-to-5cc), and its generalizability was evaluated with leave-one-out cross-validation. Results: Quantum-Clustering demonstrated a strong separation of feature-space at 15Gy across the first-and-second Principle Components of the data when the dosimetric endpoints were retrospectively identified. Maximum point dose prediction to the esophagus demonstrated a cross-validation accuracy of 87%, and the maximum dose to 5cc demonstrated a respective value of 79%. The largest optimized weighting factor was placed on GTV-to-esophagus distance (a factor of 10 greater than the second largest weighting factor), indicating an intuitively strong correlation between this feature and both endpoints. Conclusion: This pilot study shows that it is feasible to predict dose-volume endpoints based on patient-specific anatomic features. The developed methodology can potentially help to identify patients at risk for higher OAR doses, thus improving the efficiency of treatment planning. R01-184173.« less

Surface characterization and adhesion and friction properties of hydrophobic leaf surfaces.

PubMed

Burton, Zachary; Bhushan, Bharat

2006-01-01

Super-hydrophobic surfaces as well as low adhesion and friction are desirable for various industrial applications. Certain plant leaves are known to be hydrophobic in nature. These leaves are hydrophobic due to the presence of microbumps and a thin wax film on the surface of the leaf. The purpose of this study is to fully characterize the leaf surface and to separate out the effects of the microbumps and the wax on the hydrophobicity. Furthermore, the adhesion and friction properties of the leaves, with and without wax, are studied. Using an optical profiler and an atomic/friction force microscope (AFM/FFM), measurements on the hydrophobic leaves, both with and without wax, were made to fully characterize the leaf surface. Using a model that predicts contact angle as a function of roughness, the roughness factor for the hydrophobic leaves has been calculated, which is used to calculate the contact angle for a flat leaf surface. It is shown that both the microbumps and the wax play an equally important role in the hydrophobic nature as well as adhesion and friction of the leaf. This study will be useful in developing super-hydrophobic surfaces.

Neofusicoccum ribis Associated with Leaf Blight on Rubber (Hevea brasiliensis) in Peninsular Malaysia

PubMed Central

Nyaka Ngobisa, A. I. C.; Zainal Abidin, M. A.; Wong, M. Y.; Wan Noordin, M. W. D.

2013-01-01

Hevea brasiliensis is a natural source of rubber and an important plantation tree species in Malaysia. Leaf blight disease caused by Fusicoccum substantially reduces the growth and performance of H. brasiliensis. The aim of this study was to use a combination of both morphological characteristics and molecular data to clarify the taxonomic position of the fungus associated with leaf blight disease. Fusicoccum species were isolated from infected leaves collected from plantations at 3 widely separated locations – Selangor, Perak, and Johor states – in Peninsular Malaysia in 2010. All the isolates were identified according to their conidial patterns and DNA sequences generated from internal transcribed spacers (ITS1 and ITS2), the 5.8S rRNA, and an unknown locus (BotF15) containing microsatellite repeats. Based on taxonomic and sequence data, Neofusicoccum ribis was identified as the main cause of leaf blight disease in H. brasiliensis in commercial plantations in Malaysia. A pathogenicity trial on detached leaves further confirmed that N. ribis causes leaf blight disease. N. ribis is an important leaf pathogen, and its detection in Malaysia has important implications for future planting of H. brasiliensis. PMID:25288924

Neofusicoccum ribis Associated with Leaf Blight on Rubber (Hevea brasiliensis) in Peninsular Malaysia.

PubMed

Nyaka Ngobisa, A I C; Zainal Abidin, M A; Wong, M Y; Wan Noordin, M W D

2013-03-01

Hevea brasiliensis is a natural source of rubber and an important plantation tree species in Malaysia. Leaf blight disease caused by Fusicoccum substantially reduces the growth and performance of H. brasiliensis. The aim of this study was to use a combination of both morphological characteristics and molecular data to clarify the taxonomic position of the fungus associated with leaf blight disease. Fusicoccum species were isolated from infected leaves collected from plantations at 3 widely separated locations - Selangor, Perak, and Johor states - in Peninsular Malaysia in 2010. All the isolates were identified according to their conidial patterns and DNA sequences generated from internal transcribed spacers (ITS1 and ITS2), the 5.8S rRNA, and an unknown locus (BotF15) containing microsatellite repeats. Based on taxonomic and sequence data, Neofusicoccum ribis was identified as the main cause of leaf blight disease in H. brasiliensis in commercial plantations in Malaysia. A pathogenicity trial on detached leaves further confirmed that N. ribis causes leaf blight disease. N. ribis is an important leaf pathogen, and its detection in Malaysia has important implications for future planting of H. brasiliensis.

Inducible repression of multiple expansin genes leads to growth suppression during leaf development.

PubMed

Goh, Hoe-Han; Sloan, Jennifer; Dorca-Fornell, Carmen; Fleming, Andrew

2012-08-01

Expansins are cell wall proteins implicated in the control of plant growth via loosening of the extracellular matrix. They are encoded by a large gene family, and data linked to loss of single gene function to support a role of expansins in leaf growth remain limited. Here, we provide a quantitative growth analysis of transgenics containing an inducible artificial microRNA construct designed to down-regulate the expression of a number of expansin genes that an expression analysis indicated are expressed during the development of Arabidopsis (Arabidopsis thaliana) leaf 6. The results support the hypothesis that expansins are required for leaf growth and show that decreased expansin gene expression leads to a more marked repression of growth during the later stage of leaf development. In addition, a histological analysis of leaves in which expansin gene expression was suppressed indicates that, despite smaller leaves, mean cell size was increased. These data provide functional evidence for a role of expansins in leaf growth, indicate the importance of tissue/organ developmental context for the outcome of altered expansin gene expression, and highlight the separation of the outcome of expansin gene expression at the cellular and organ levels.

Hot pixel generation in active pixel sensors: dosimetric and micro-dosimetric response

NASA Technical Reports Server (NTRS)

Scheick, Leif; Novak, Frank

2003-01-01

The dosimetric response of an active pixel sensor is analyzed. heavy ions are seen to damage the pixel in much the same way as gamma radiation. The probability of a hot pixel is seen to exhibit behavior that is not typical with other microdose effects.

The first clinical implementation of electromagnetic transponder-guided MLC tracking.

PubMed

Keall, Paul J; Colvill, Emma; O'Brien, Ricky; Ng, Jin Aun; Poulsen, Per Rugaard; Eade, Thomas; Kneebone, Andrew; Booth, Jeremy T

2014-02-01

We report on the clinical process, quality assurance, and geometric and dosimetric results of the first clinical implementation of electromagnetic transponder-guided MLC tracking which occurred on 28 November 2013 at the Northern Sydney Cancer Centre. An electromagnetic transponder-based positioning system (Calypso) was modified to send the target position output to in-house-developed MLC tracking code, which adjusts the leaf positions to optimally align the treatment beam with the real-time target position. Clinical process and quality assurance procedures were developed and performed. The first clinical implementation of electromagnetic transponder-guided MLC tracking was for a prostate cancer patient being treated with dual-arc VMAT (RapidArc). For the first fraction of the first patient treatment of electromagnetic transponder-guided MLC tracking we recorded the in-room time and transponder positions, and performed dose reconstruction to estimate the delivered dose and also the dose received had MLC tracking not been used. The total in-room time was 21 min with 2 min of beam delivery. No additional time was needed for MLC tracking and there were no beam holds. The average prostate position from the initial setup was 1.2 mm, mostly an anterior shift. Dose reconstruction analysis of the delivered dose with MLC tracking showed similar isodose and target dose volume histograms to the planned treatment and a 4.6% increase in the fractional rectal V60. Dose reconstruction without motion compensation showed a 30% increase in the fractional rectal V60 from that planned, even for the small motion. The real-time beam-target correction method, electromagnetic transponder-guided MLC tracking, has been translated to the clinic. This achievement represents a milestone in improving geometric and dosimetric accuracy, and by inference treatment outcomes, in cancer radiotherapy.

Log file-based patient dose calculations of double-arc VMAT for head-and-neck radiotherapy.

PubMed

Katsuta, Yoshiyuki; Kadoya, Noriyuki; Fujita, Yukio; Shimizu, Eiji; Majima, Kazuhiro; Matsushita, Haruo; Takeda, Ken; Jingu, Keiichi

2018-04-01

The log file-based method cannot display dosimetric changes due to linac component miscalibration because of the insensitivity of log files to linac component miscalibration. The purpose of this study was to supply dosimetric changes in log file-based patient dose calculations for double-arc volumetric-modulated arc therapy (VMAT) in head-and-neck cases. Fifteen head-and-neck cases participated in this study. For each case, treatment planning system (TPS) doses were produced by double-arc and single-arc VMAT. Miscalibration-simulated log files were generated by inducing a leaf miscalibration of ±0.5 mm into the log files that were acquired during VMAT irradiation. Subsequently, patient doses were estimated using the miscalibration-simulated log files. For double-arc VMAT, regarding planning target volume (PTV), the change from TPS dose to miscalibration-simulated log file dose in D mean was 0.9 Gy and that for tumor control probability was 1.4%. As for organ-at-risks (OARs), the change in D mean was <0.7 Gy and normal tissue complication probability was <1.8%. A comparison between double-arc and single-arc VMAT for PTV showed statistically significant differences in the changes evaluated by D mean and radiobiological metrics (P < 0.01), even though the magnitude of these differences was small. Similarly, for OARs, the magnitude of these changes was found to be small. Using the log file-based method for PTV and OARs, the log file-based method estimate of patient dose using the double-arc VMAT has accuracy comparable to that obtained using the single-arc VMAT. Copyright © 2018 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Quantitative evaluation of patient-specific quality assurance using online dosimetry system

NASA Astrophysics Data System (ADS)

Jung, Jae-Yong; Shin, Young-Ju; Sohn, Seung-Chang; Min, Jung-Whan; Kim, Yon-Lae; Kim, Dong-Su; Choe, Bo-Young; Suh, Tae-Suk

2018-01-01

In this study, we investigated the clinical performance of an online dosimetry system (Mobius FX system, MFX) by 1) dosimetric plan verification using gamma passing rates and dose volume metrics and 2) error-detection capability evaluation by deliberately introduced machine error. Eighteen volumetric modulated arc therapy (VMAT) plans were studied. To evaluate the clinical performance of the MFX, we used gamma analysis and dose volume histogram (DVH) analysis. In addition, to evaluate the error-detection capability, we used gamma analysis and DVH analysis utilizing three types of deliberately introduced errors (Type 1: gantry angle-independent multi-leaf collimator (MLC) error, Type 2: gantry angle-dependent MLC error, and Type 3: gantry angle error). A dosimetric verification comparison of physical dosimetry system (Delt4PT) and online dosimetry system (MFX), gamma passing rates of the two dosimetry systems showed very good agreement with treatment planning system (TPS) calculation. For the average dose difference between the TPS calculation and the MFX measurement, most of the dose metrics showed good agreement within a tolerance of 3%. For the error-detection comparison of Delta4PT and MFX, the gamma passing rates of the two dosimetry systems did not meet the 90% acceptance criterion with the magnitude of error exceeding 2 mm and 1.5 ◦, respectively, for error plans of Types 1, 2, and 3. For delivery with all error types, the average dose difference of PTV due to error magnitude showed good agreement between calculated TPS and measured MFX within 1%. Overall, the results of the online dosimetry system showed very good agreement with those of the physical dosimetry system. Our results suggest that a log file-based online dosimetry system is a very suitable verification tool for accurate and efficient clinical routines for patient-specific quality assurance (QA).

The first clinical implementation of electromagnetic transponder-guided MLC tracking

PubMed Central

Keall, Paul J.; Colvill, Emma; O’Brien, Ricky; Ng, Jin Aun; Poulsen, Per Rugaard; Eade, Thomas; Kneebone, Andrew; Booth, Jeremy T.

2014-01-01

Purpose: We report on the clinical process, quality assurance, and geometric and dosimetric results of the first clinical implementation of electromagnetic transponder-guided MLC tracking which occurred on 28 November 2013 at the Northern Sydney Cancer Centre. Methods: An electromagnetic transponder-based positioning system (Calypso) was modified to send the target position output to in-house-developed MLC tracking code, which adjusts the leaf positions to optimally align the treatment beam with the real-time target position. Clinical process and quality assurance procedures were developed and performed. The first clinical implementation of electromagnetic transponder-guided MLC tracking was for a prostate cancer patient being treated with dual-arc VMAT (RapidArc). For the first fraction of the first patient treatment of electromagnetic transponder-guided MLC tracking we recorded the in-room time and transponder positions, and performed dose reconstruction to estimate the delivered dose and also the dose received had MLC tracking not been used. Results: The total in-room time was 21 min with 2 min of beam delivery. No additional time was needed for MLC tracking and there were no beam holds. The average prostate position from the initial setup was 1.2 mm, mostly an anterior shift. Dose reconstruction analysis of the delivered dose with MLC tracking showed similar isodose and target dose volume histograms to the planned treatment and a 4.6% increase in the fractional rectal V60. Dose reconstruction without motion compensation showed a 30% increase in the fractional rectal V60 from that planned, even for the small motion. Conclusions: The real-time beam-target correction method, electromagnetic transponder-guided MLC tracking, has been translated to the clinic. This achievement represents a milestone in improving geometric and dosimetric accuracy, and by inference treatment outcomes, in cancer radiotherapy. PMID:24506591

American Beech Leaf-litter Leachate Chemistry: Effects of Geography and Phenophase

NASA Astrophysics Data System (ADS)

Hudson, J. E.; Levia, D. F., Jr.; Wheeler, K. I.; Winters, C. G.; Vaughan, M.; Chace, J.; Sleeper, R.

2017-12-01

The decomposition of leaves from broadleaved trees contributes to the energy budget of forested watersheds via dissolved organic matter, nutrients, and biological activity. Although it is often implicitly assumed that intraspecific differences in leaf-litter leachate chemistry do not significantly differ geographically, we attempted to discern how these inputs may vary from single tree species that is known to have two genetically distinct and geographically separate populations, as well as how these inputs may change throughout autumn senescence and after abscission. We analyzed the physical and chemical leaf traits and leaf leachates of leaves from Fagus grandifolia (American beech; n = 360) during three phenophases: fresh green, senescing, and fallen. During each phenophase, leaves were collected from four sites along a geographic transect stretching from Vermont to North Carolina (over 1400 km), with two sites representing each genetic population and differing climatic conditions. Pooled leaf leachates from each site and phenophase were analyzed for routine solutes and nutrients, as well as fluorescent and UV-visible absorbance indices. Quantities of macro- and micronutrients were highly variable among sites and phenophases but tended to be lowest from fallen leaves, while measured fluorescence and absorbance indices tended to increase during leaves collected during senescence. Results suggest significant differences in leached nutrients among field sites, while optical properties and nutrients varied significantly among phenophases. Aromaticity and molecular weight of DOM in leachates was generally low, and aromaticity and humification of leachates both increased as leaves aged throughout the selected phenophases. Results also suggest that geographically (or genetically) separate populations of the same species do not experience senescence in the same way and that implicit assumptions of intraspecific uniformity of leaf-litter leachate chemistry for a given tree species may be invalid. Funding note: Research made possible by the U.S. National Science Foundation (Grant No. IIA-1330238, IIA-1330446, and IIA-1330406).

Intra- and interspecific variability of carbon isotope composition (d13C) and water-use efficiency in 5 deciduous tree species growing a mixed stand in North-Eastern France

NASA Astrophysics Data System (ADS)

Zapater, M.; Breda, N.; Storchi, G.; Granier, A.

2005-12-01

Intra and interspecific variability in leaf gas exchange (net assimilation, stomatal conductance, transpiration, water use efficiency: WUE), in carbon isotope composition (d13C) and leaf characteristics related to photosynthesis was assessed in 5 trees species growing in a young broad-leaved mixed forest in North-Eastern France (Hesse, Lorraine). The studied species belong to contrasted functional groups of light tolerance: European beech (Fagus sylvatica) as shade tolerant species; sessile oak (Quercus petraea) and hornbeam (Carpinus betulus) as semitolerant species; silver birch (Betula pendula) and European aspen (Populus tremula) as shade intolerant species (pioneer species). Gas exchange was measured at leaf level in the upper and the lower canopy layers using a portable system (LI-6200, Licor). d13C signatures were determined in the sun and shade leaves in both bulk material and soluble sugars. Clear differences in bulk leaves and soluble sugars d13C and intrinsic WUEint were found among the investigated species, whatever the leaf location in the canopy. Within each tree species, shade leaves exhibited lower WUEint and more negative d13C than sun leaves. Little variability among trees was found for a given species. The 3 functional groups were separated by their leaf carbon content. Nevertheless each of the variables d13C, leaf mass area and nitrogen content, alone, could not separate the groups. A linear relationship was found between WUEint and d13C at the intraspecific level (r2 = 0.87 for leaves; r2 =0.89 for sugars) and at the interspecific level (r2 = 0.72 for bulk leaves). Nevertheless, this relationship differed from that of Farquhar et al. (1982), due to a different intercept, while the slope was the same. The causes of these variations are discussed. Key words: d13C; deciduous; mixed forest; WUEint; shade tolerance.

Design and clinical use of a rotational phantom for dosimetric verification of IMRT/VMAT treatments.

PubMed

Grams, Michael P; de Los Santos, Luis E Fong

2018-06-01

To describe the design and clinical use of a rotational phantom for dosimetric verification of IMRT/VMAT treatment plans using radiochromic film. A solid water cylindrical phantom was designed with separable upper and lower halves and rests on plastic bearings allowing for 360° rotation about its central axis. The phantom accommodates a half sheet of radiochromic film, and by rotating the cylinder, the film can be placed in any plane between coronal and sagittal. Calculated dose planes coinciding with rotated film measurements are exported by rotating the CT image and dose distribution within the treatment planning system. The process is illustrated with 2 rotated film measurements of an SRS treatment plan involving 4 separate targets. Additionally, 276 patient specific QA measurements were obtained with the phantom and analyzed with a 2%/2 mm gamma criterion. The average 2%/2 mm gamma passing rate for all 276 plans was 99.3%. Seventy-two of the 276 plans were measured with the plane of the film rotated between the coronal and sagittal planes and had an average passing rate of 99.4%. The rotational phantom allows for accurate film measurements in any plane. With this technique, regions of a dose distribution which might otherwise require multiple sagittal or coronal measurements can be verified with as few as a single measurement. This increases efficiency and, in combination with the high spatial resolution inherent to film dosimetry, makes the rotational technique an attractive option for patient-specific QA. Copyright © 2018 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

In vitro evaluation of genotoxicity of avocado (Persea americana) fruit and leaf extracts in human peripheral lymphocytes.

PubMed

Kulkarni, Paresh; Paul, Rajkumar; Ganesh, N

2010-07-01

Persea americana is much sought after both for the nutritional value of its fruit and the medicinal values of its various plant parts. A chromosomal aberration assay was undertaken to evaluate the potential genotoxicity of crude extracts from avocado fruits and leaves. Chromosomal aberrations were observed in cultured human peripheral lymphocytes exposed to separately increasing concentrations of 50% methanolic extracts of Persea americana fruit and leaves. The groups exposed to leaf and fruit extracts, respectively, showed a concentration-dependent increase in chromosomal aberrations as compared to that in a control group. The mean percentage total aberrant metaphases at 100 mg/kg, 200 mg/kg, and 300 mg/kg concentrations of leaf extract were found respectively to be 58 ± 7.05, 72 ± 6.41, and 78 ± 5.98, which were significantly higher (p < 0.0001 each) than that in the control group (6 ± 3.39). The mean percentage total aberrant metaphases at 100 mg/kg, 200 mg/kg, and 300 mg/kg concentrations of fruit extract were found to be 18 ± 5.49, 40 ± 10.00, and 52 ± 10.20, respectively, which were significantly higher (p = 0.033, p < 0.0001, and p < 0.0001, respectively) than that for control (6 ± 3.39). Acrocentric associations and premature centromeric separation were the two most common abnormalities observed in both the exposed groups. The group exposed to leaf extracts also showed a significant number of a variety of other structural aberrations, including breaks, fragments, dicentrics, terminal deletion, minutes, and Robertsonian translocations. The group exposed to leaf extract showed higher frequency of all types of aberrations at equal concentrations as compared to the group exposed to fruit extract.

Effect of greenhouse conditions on the leaf apoplastic proteome of Coffea arabica plants.

PubMed

Guerra-Guimarães, Leonor; Vieira, Ana; Chaves, Inês; Pinheiro, Carla; Queiroz, Vagner; Renaut, Jenny; Ricardo, Cândido P

2014-06-02

This work describes the coffee leaf apoplastic proteome and its modulation by the greenhouse conditions. The apoplastic fluid (APF) was obtained by leaf vacuum infiltration, and the recovered proteins were separated by 2-DE and subsequently identified by matrix assisted laser desorption/ionization time of flight-mass spectrometry, followed by homology search in EST coffee databases. Prediction tools revealed that the majority of the 195 identified proteins are involved in cell wall metabolism and in stress/defense responses. Although most of the proteins follow the classical secretory mechanism, a low percentage of them seem to result from unconventional secretion (leaderless secreted proteins). Principal components analysis revealed that the APF samples formed two distinct groups, with the temperature amplitude mostly contributing for this separation (higher or lower than 10°C, respectively). Sixty one polypeptide spots allowed defining these two groups and 28 proteins were identified, belonging to carbohydrate metabolism, cell wall modification and proteolysis. Interestingly stress/defense proteins appeared as more abundant in Group I which is associated with a higher temperature amplitude. It seems that the proteins in the coffee leaf APF might be implicated in structural modifications in the extracellular space that are crucial for plant development/adaptation to the conditions of the prevailing environment. This is the first detailed proteomic study of the coffee leaf apoplastic fluid (APF) and of its modulation by the greenhouse conditions. The comprehensive overview of the most abundant proteins present in the extra-cellular compartment is particularly important for the understanding of coffee responses to abiotic/biotic stress. This article is part of a Special Issue entitled: Environmental and structural proteomics. Copyright © 2014 Elsevier B.V. All rights reserved.

SU-E-T-125: Dosimetric Comparison of Intensity Modulated Radiation Therapy Using Robotic Versus Traditional Linac Platform in Prostate Cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hayes, T; Rella, J; Yang, J

Purpose: Recent development of an MLC for robotic external beam radiotherapy has the potential of new clinical application in conventionally fractionated radiation therapy. This study offers a dosimetric comparison of IMRT plans using Cyberknife with MLC versus conventional linac plans. Methods: Ten prostate cancer patients treated on a traditional linac with IMRT to 7920cGy at 180cGy/fraction were randomly selected. GTVs were defined as prostate plus proximal seminal vesicles. PTVs were defined as GTV+8mm in all directions except 5mm posteriorly. Conventional IMRT planning was performed on Philips Pinnacle and delivered on a standard linac with CBCT and 10mm collimator leaf width.more » For each case a Cyberknife plan was created using Accuray Multiplan with same CT data set, contours, and dose constraints. All dosimetric data was transferred to third party software for independent computation of contour volumes and DVH. Delivery efficiency was evaluated using total MU, treatment time, number of beams, and number of segments. Results: Evaluation criteria including percent target coverage, homogeneity index, and conformity index were found to be comparable. All dose constraints from QUANTEC were found to be statistically similar except rectum V50Gy and bladder V65Gy. Average rectum V50Gy was lower for robotic IMRT (30.07%±6.57) versus traditional (34.73%±3.62, p=0.0130). Average bladder V65Gy was lower for robotic (17.87%±12.74) versus traditional (21.03%±11.93, p=0.0405). Linac plans utilized 9 coplanar beams, 48.9±3.8 segments, and 19381±2399MU. Robotic plans utilized 38.4±9.0 non-coplanar beams, 85.5±21.0 segments and 42554.71±16381.54 MU. The average treatment was 15.02±0.60 minutes for traditional versus 20.90±2.51 for robotic. Conclusion: The robotic IMRT plans were comparable to the traditional IMRT plans in meeting the target volume dose objectives. Critical structure dose constraints were largely comparable although statistically significant differences were found in favor of the robotic platform in terms of rectum V50Gy and bladder V65Gy at a cost of 25% longer treatment time.« less

Dosimetric Verification of IMRT Treatment Plans Using an Electronic Portal Imaging Device

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kruszyna, Marta

This paper presents the procedures and results of dosimetric verification using an Electronic Portal Imaging Device as a tool for pre-treatment dosimetry in IMRT technique at the Greater Poland Cancer Centre in Poznan, Poland. The evaluation of dosimetric verification for various organ, during a 2 year period is given.

TH-E-BRE-04: An Online Replanning Algorithm for VMAT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahunbay, E; Li, X; Moreau, M

2014-06-15

Purpose: To develop a fast replanning algorithm based on segment aperture morphing (SAM) for online replanning of volumetric modulated arc therapy (VMAT) with flattening filtered (FF) and flattening filter free (FFF) beams. Methods: A software tool was developed to interface with a VMAT planning system ((Monaco, Elekta), enabling the output of detailed beam/machine parameters of original VMAT plans generated based on planning CTs for FF or FFF beams. A SAM algorithm, previously developed for fixed-beam IMRT, was modified to allow the algorithm to correct for interfractional variations (e.g., setup error, organ motion and deformation) by morphing apertures based on themore » geometric relationship between the beam's eye view of the anatomy from the planning CT and that from the daily CT for each control point. The algorithm was tested using daily CTs acquired using an in-room CT during daily IGRT for representative prostate cancer cases along with their planning CTs. The algorithm allows for restricted MLC leaf travel distance between control points of the VMAT delivery to prevent SAM from increasing leaf travel, and therefore treatment delivery time. Results: The VMAT plans adapted to the daily CT by SAM were found to improve the dosimetry relative to the IGRT repositioning plans for both FF and FFF beams. For the adaptive plans, the changes in leaf travel distance between control points were < 1cm for 80% of the control points with no restriction. When restricted to the original plans' maximum travel distance, the dosimetric effect was minimal. The adaptive plans were delivered successfully with similar delivery times as the original plans. The execution of the SAM algorithm was < 10 seconds. Conclusion: The SAM algorithm can quickly generate deliverable online-adaptive VMAT plans based on the anatomy of the day for both FF and FFF beams.« less

SU-E-T-32: A Feasibility Study of Independent Dose Verification for IMAT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kamima, T; Takahashi, R; Sato, Y

2015-06-15

Purpose: To assess the feasibility of the independent dose verification (Indp) for intensity modulated arc therapy (IMAT). Methods: An independent dose calculation software program (Simple MU Analysis, Triangle Products, JP) was used in this study, which can compute the radiological path length from the surface to the reference point for each control point using patient’s CT image dataset and the MLC aperture shape was simultaneously modeled in reference to the information of MLC from DICOM-RT plan. Dose calculation was performed using a modified Clarkson method considering MLC transmission and dosimetric leaf gap. In this study, a retrospective analysis was conductedmore » in which IMAT plans from 120 patients of the two sites (prostate / head and neck) from four institutes were retrospectively analyzed to compare the Indp to the TPS using patient CT images. In addition, an ion-chamber measurement was performed to verify the accuracy of the TPS and the Indp in water-equivalent phantom. Results: The agreements between the Indp and the TPS (mean±1SD) were −0.8±2.4% and −1.3±3.8% for the regions of prostate and head and neck, respectively. The measurement comparison showed similar results (−0.8±1.6% and 0.1±4.6% for prostate and head and neck). The variation was larger in the head and neck because the number of the segments was increased that the reference point was under the MLC and the modified Clarkson method cannot consider the smooth falloff of the leaf penumbra. Conclusion: The independent verification program would be practical and effective for secondary check for IMAT with the sufficient accuracy in the measurement and CT-based calculation. The accuracy would be improved if considering the falloff of the leaf penumbra.« less

SU-G-BRA-14: Dose in a Rigidly Moving Phantom with Jaw and MLC Compensation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chao, E; Lucas, D

Purpose: To validate dose calculation for a rigidly moving object with jaw motion and MLC shifts to compensate for the motion in a TomoTherapy™ treatment delivery. Methods: An off-line version of the TomoTherapy dose calculator was extended to perform dose calculations for rigidly moving objects. A variety of motion traces were added to treatment delivery plans, along with corresponding jaw compensation and MLC shift compensation profiles. Jaw compensation profiles were calculated by shifting the jaws such that the center of the treatment beam moved by an amount equal to the motion in the longitudinal direction. Similarly, MLC compensation profiles weremore » calculated by shifting the MLC leaves by an amount that most closely matched the motion in the transverse direction. The same jaw and MLC compensation profiles were used during simulated treatment deliveries on a TomoTherapy system, and film measurements were obtained in a rigidly moving phantom. Results: The off-line TomoTherapy dose calculator accurately predicted dose profiles for a rigidly moving phantom along with jaw motion and MLC shifts to compensate for the motion. Calculations matched film measurements to within 2%/1 mm. Jaw and MLC compensation substantially reduced the discrepancy between the delivered dose distribution and the calculated dose with no motion. For axial motion, the compensated dose matched the no-motion dose within 2%/1mm. For transverse motion, the dose matched within 2%/3mm (approximately half the width of an MLC leaf). Conclusion: The off-line TomoTherapy dose calculator accurately computes dose delivered to a rigidly moving object, and accurately models the impact of moving the jaws and shifting the MLC leaf patterns to compensate for the motion. Jaw tracking and MLC leaf shifting can effectively compensate for the dosimetric impact of motion during a TomoTherapy treatment delivery.« less

SU-E-T-478: Sliding Window Multi-Criteria IMRT Optimization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Craft, D; Papp, D; Unkelbach, J

2014-06-01

Purpose: To demonstrate a method for what-you-see-is-what-you-get multi-criteria Pareto surface navigation for step and shoot IMRT treatment planning. Methods: We show mathematically how multiple sliding window treatment plans can be averaged to yield a single plan whose dose distribution is the dosimetric average of the averaged plans. This is incorporated into the Pareto surface navigation based approach to treatment planning in such a way that as the user navigates the surface, the plans he/she is viewing are ready to be delivered (i.e. there is no extra ‘segment the plans’ step that often leads to unacceptable plan degradation in step andmore » shoot Pareto surface navigation). We also describe how the technique can be applied to VMAT. Briefly, sliding window VMAT plans are created such that MLC leaves paint out fluence maps every 15 degrees or so. These fluence map leaf trajectories are averaged in the same way the static beam IMRT ones are. Results: We show mathematically that fluence maps are exactly averaged using our leaf sweep averaging algorithm. Leaf transmission and output factor corrections effects, which are ignored in this work, can lead to small errors in terms of the dose distributions not being exactly averaged even though the fluence maps are. However, our demonstrations show that the dose distributions are almost exactly averaged as well. We demonstrate the technique both for IMRT and VMAT. Conclusions: By turning to sliding window delivery, we show that the problem of losing plan fidelity during the conversion of an idealized fluence map plan into a deliverable plan is remedied. This will allow for multicriteria optimization that avoids the pitfall that the planning has to be redone after the conversion into MLC segments due to plan quality decline. David Craft partially funded by RaySearch Laboratories.« less

Personalized treatment planning with a model of radiation therapy outcomes for use in multiobjective optimization of IMRT plans for prostate cancer.

PubMed

Smith, Wade P; Kim, Minsun; Holdsworth, Clay; Liao, Jay; Phillips, Mark H

2016-03-11

To build a new treatment planning approach that extends beyond radiation transport and IMRT optimization by modeling the radiation therapy process and prognostic indicators for more outcome-focused decision making. An in-house treatment planning system was modified to include multiobjective inverse planning, a probabilistic outcome model, and a multi-attribute decision aid. A genetic algorithm generated a set of plans embodying trade-offs between the separate objectives. An influence diagram network modeled the radiation therapy process of prostate cancer using expert opinion, results of clinical trials, and published research. A Markov model calculated a quality adjusted life expectancy (QALE), which was the endpoint for ranking plans. The Multiobjective Evolutionary Algorithm (MOEA) was designed to produce an approximation of the Pareto Front representing optimal tradeoffs for IMRT plans. Prognostic information from the dosimetrics of the plans, and from patient-specific clinical variables were combined by the influence diagram. QALEs were calculated for each plan for each set of patient characteristics. Sensitivity analyses were conducted to explore changes in outcomes for variations in patient characteristics and dosimetric variables. The model calculated life expectancies that were in agreement with an independent clinical study. The radiation therapy model proposed has integrated a number of different physical, biological and clinical models into a more comprehensive model. It illustrates a number of the critical aspects of treatment planning that can be improved and represents a more detailed description of the therapy process. A Markov model was implemented to provide a stronger connection between dosimetric variables and clinical outcomes and could provide a practical, quantitative method for making difficult clinical decisions.

Bleaching of leaf litter and associated microfungi in subboreal and subalpine forests.

PubMed

Hagiwara, Yusuke; Matsuoka, Shunsuke; Hobara, Satoru; Mori, Akira S; Hirose, Dai; Osono, Takashi

2015-10-01

Fungal decomposition of lignin leads to the whitening, or bleaching, of leaf litter, especially in temperate and tropical forests, but less is known about such bleaching in forests of cooler regions, such as boreal and subalpine forests. The purposes of the present study were to examine the extent of bleached area on the surface of leaf litter and its variation with environmental conditions in subboreal and subalpine forests in Japan and to examine the microfungi associated with the bleaching of leaf litter by isolating fungi from the bleached portions of the litter. Bleached area accounted for 21.7%-32.7% and 2.0%-10.0% of total leaf area of Quercus crispula and Betula ermanii, respectively, in subboreal forests, and for 6.3% and 18.6% of total leaf area of B. ermanii and Picea jezoensis var. hondoensis, respectively, in a subalpine forest. In subboreal forests, elevation, C/N ratio and pH of the FH layer, and slope aspect were selected as predictor variables for the bleached leaf area. Leaf mass per area and lignin content were consistently lower in the bleached area than in the nonbleached area of the same leaves, indicating that the selective decomposition of acid unhydrolyzable residue (recalcitrant compounds such as lignin, tannins, and cutins) enhanced the mass loss of leaf tissues in the bleached portions. Isolates of a total of 11 fungal species (6 species of Ascomycota and 5 of Basidiomycota) exhibited leaf-litter-bleaching activity under pure culture conditions. Two fungal species (Coccomyces sp. and Mycena sp.) occurred in both subboreal and subalpine forests, which were separated from each other by approximately 1100 km.

Genetic analysis of rice mutants responsible for narrow leaf phenotype and reduced vein number.

PubMed

Kubo, Fumika Clara; Yasui, Yukiko; Kumamaru, Toshihiro; Sato, Yutaka; Hirano, Hiro-Yuki

2017-03-17

Leaves are a major site for photosynthesis and a key determinant of plant architecture. Rice produces thin and slender leaves, which consist of the leaf blade and leaf sheath separated by the lamina joint. Two types of vasculature, the large and small vascular bundles, run in parallel, together with a strong structure, the midrib. In this paper, we examined the function of four genes that regulate the width of the leaf blade and the vein number: NARROW LEAF1 (NAL1), NAL2, NAL3 and NAL7. We backcrossed original mutants of these genes with the standard wild-type rice, Taichung 65. We then compared the effect of each mutation on similar genetic backgrounds and examined genetic interactions of these genes. The nal1 single mutation and the nal2 nal3 double mutation showed a severe effect on leaf width, resulting in very narrow leaves. Although vein number was also reduced in the nal1 and nal2 nal3 mutants, the small vein number was more strongly reduced than the large vein number. In contrast, the nal7 mutation showed a milder effect on leaf width and vein number, and both the large and small veins were similarly affected. Thus, the genes responsible for narrow leaf phenotype seem to play distinct roles. The nal7 mutation showed additive effects on both leaf width and vein number, when combined with the nal1 single or the nal2 nal3 double mutation. In addition, observations of inner tissues revealed that cell differentiation was partially compromised in the nal2 nal3 nal7 mutant, consistent with the severe reduction in leaf width in this triple mutant.

Spatial variation of deuterium enrichment in bulk water of snowgum leaves.

PubMed

Santrucek, Jirí; Kveton, Jirí; Setlík, Jirí; Bulícková, Lenka

2007-01-01

Deuterium enrichment of bulk water was measured and modeled in snowgum (Eucalyptus pauciflora Sieber ex Sprengel) leaves grown under contrasting air and soil humidity in arid and wet conditions in a glasshouse. A map of the enrichment was constructed with a resolution of 4 mm by using a newly designed cryodistillation method. There was progressively increasing enrichment in both longitudinal (along the leaf midrib) and transversal (perpendicular to the midrib) directions, most pronounced in the arid-grown leaf. The whole-leaf average of the enrichment was well below the value estimated by the Craig-Gordon model. The discrepancy between model and measurements persisted when the estimates were carried out separately for the leaf base and tip, which differed in temperature and stomatal conductance. The discrepancy was proportional to the transpiration rate, indicating the significance of diffusion-advection interplay (Péclet effect) of deuterium-containing water molecules in small veins close to the evaporating sites in the leaf. Combined Craig-Gordon and desert-river models, with or without the Péclet number, P, were used for predicting the leaf longitudinal enrichment. The predictions without P overestimated the measured values of deltadeuterium. Fixed P value partially improved the coincidence. We suggest that P should vary along the leaf length l to reconcile the modeled data with observations of longitudinal enrichment. Local values of P, P(l), integrating the upstream fraction of water used or the leaf area, substantially improved the model predictions.

Relative dosimetrical verification in high dose rate brachytherapy using two-dimensional detector array IMatriXX

PubMed Central

Manikandan, A.; Biplab, Sarkar; David, Perianayagam A.; Holla, R.; Vivek, T. R.; Sujatha, N.

2011-01-01

For high dose rate (HDR) brachytherapy, independent treatment verification is needed to ensure that the treatment is performed as per prescription. This study demonstrates dosimetric quality assurance of the HDR brachytherapy using a commercially available two-dimensional ion chamber array called IMatriXX, which has a detector separation of 0.7619 cm. The reference isodose length, step size, and source dwell positional accuracy were verified. A total of 24 dwell positions, which were verified for positional accuracy gave a total error (systematic and random) of –0.45 mm, with a standard deviation of 1.01 mm and maximum error of 1.8 mm. Using a step size of 5 mm, reference isodose length (the length of 100% isodose line) was verified for single and multiple catheters of same and different source loadings. An error ≤1 mm was measured in 57% of tests analyzed. Step size verification for 2, 3, 4, and 5 cm was performed and 70% of the step size errors were below 1 mm, with maximum of 1.2 mm. The step size ≤1 cm could not be verified by the IMatriXX as it could not resolve the peaks in dose profile. PMID:21897562

Exposure scheme separates effects of electric shock and electric field for honey bees, Apis mellifera L

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bindokas, V.P.; Gauger, J.R.; Greenberg, B.

Mechanisms to explain disturbance of honey bee colonies under a 765-kV, 60-Hz transmission line (electric (E) field = 7 kV/m) fall into two categories: direct bee perception of enhanced in-hive E fields, and perception of shock from induced currents. The same adverse biological effects previously observed in honey bee colonies exposed under a 765-kV transmission line can be reproduced by exposing worker bees to shock or E field within elongated hive entranceways (= tunnels). Exposure to intense E field caused disturbance only if bees were in contact with a conductive substrate. E-field and shock exposure can be separated and preciselymore » defined within tunnels, eliminating dosimetric vagaries that occur when entire hives are exposed to E field.« less

Mortality among workers with chronic radiation sickness

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shilnikova, N.S.; Koshurnikova, N.A.; Bolotnikova, M.G.

1996-07-01

This study is based on a registry containing medical and dosimetric data of the employees who began working at different plants of the Mayak nuclear complex between 1948 and 1958 who developed chronic radiation sickness. Mayak is the first nuclear weapons plutonium production enterprise built in Russia and includes nuclear reactors, a radiochemical plant for plutonium separation, and a plutonium production enterprise built in Russia and includes nuclear reactors, a radiochemical plant for plutonium separation, and a plutonium production plant.Workers whose employment began between 1948 and 1958 exhibited a 6-28% incidence of chronic radiation sickness at the different facilities. Theremore » were no cases of chronic radiation sickness among those who began working after 1958. Data on doses of external whole-body gamma-irradiation and mortality in workers with chronic radiation sickness are presented. 6 refs., 5 tabs.« less

Regulation of Compound Leaf Development in Medicago truncatula by Fused Compound Leaf1, a Class M KNOX Gene[C][W

PubMed Central

Peng, Jianling; Yu, Jianbin; Wang, Hongliang; Guo, Yingqing; Li, Guangming; Bai, Guihua; Chen, Rujin

2011-01-01

Medicago truncatula is a legume species belonging to the inverted repeat lacking clade (IRLC) with trifoliolate compound leaves. However, the regulatory mechanisms underlying development of trifoliolate leaves in legumes remain largely unknown. Here, we report isolation and characterization of fused compound leaf1 (fcl1) mutants of M. truncatula. Phenotypic analysis suggests that FCL1 plays a positive role in boundary separation and proximal-distal axis development of compound leaves. Map-based cloning indicates that FCL1 encodes a class M KNOX protein that harbors the MEINOX domain but lacks the homeodomain. Yeast two-hybrid assays show that FCL1 interacts with a subset of Arabidopsis thaliana BEL1-like proteins with slightly different substrate specificities from the Arabidopsis homolog KNATM-B. Double mutant analyses with M. truncatula single leaflet1 (sgl1) and palmate-like pentafoliata1 (palm1) leaf mutants show that fcl1 is epistatic to palm1 and sgl1 is epistatic to fcl1 in terms of leaf complexity and that SGL1 and FCL1 act additively and are required for petiole development. Previous studies have shown that the canonical KNOX proteins are not involved in compound leaf development in IRLC legumes. The identification of FCL1 supports the role of a truncated KNOX protein in compound leaf development in M. truncatula. PMID:22080596

Improvements in Critical Dosimetric Endpoints Using the Contura Multilumen Balloon Breast Brachytherapy Catheter to Deliver Accelerated Partial Breast Irradiation: Preliminary Dosimetric Findings of a Phase IV Trial

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arthur, Douglas W., E-mail: darthur@mcvh-vcu.ed; Vicini, Frank A.; Todor, Dorin A.

2011-01-01

Purpose: Dosimetric findings in patients treated with the Contura multilumen balloon (MLB) breast brachytherapy catheter to deliver accelerated partial breast irradiation (APBI) on a multi-institutional Phase IV registry trial are presented. Methods and Materials: Computed tomography-based three-dimensional planning with dose optimization was performed. For the trial, new ideal dosimetric goals included (1) {>=}95% of the prescribed dose (PD) covering {>=}90% of the target volume, (2) a maximum skin dose {<=}125% of the PD, (3) maximum rib dose {<=}145% of the PD, and (4) the V150 {<=}50 cc and V200 {<=}10 cc. The ability to concurrently achieve these dosimetric goals usingmore » the Contura MLB was analyzed. Results: 144 cases were available for review. Using the MLB, all dosimetric criteria were met in 76% of cases. Evaluating dosimetric criteria individually, 92% and 89% of cases met skin and rib dose criteria, respectively. In 93% of cases, ideal target volume coverage goals were met, and in 99%, dose homogeneity criteria (V150 and V200) were satisfied. When skin thickness was {>=}5 mm to <7 mm, the median skin dose was limited to 120.1% of the PD, and when skin thickness was <5 mm, the median skin dose was 124.2%. When rib distance was <5 mm, median rib dose was reduced to 136.5% of the PD. When skin thickness was <7 mm and distance to rib was <5 mm, median skin and rib doses were jointly limited to 120.6% and 142.1% of the PD, respectively. Conclusion: The Contura MLB catheter provided the means of achieving the imposed higher standard of dosimetric goals in the majority of clinical scenarios encountered.« less

Practical simplifications for radioimmunotherapy dosimetric models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, S.; DeNardo, G.L.; O`Donnell, R.T.

1999-01-01

Radiation dosimetry is potentially useful for assessment and prediction of efficacy and toxicity for radionuclide therapy. The usefulness of these dose estimates relies on the establishment of a dose-response model using accurate pharmacokinetic data and a radiation dosimetric model. Due to the complexity in radiation dose estimation, many practical simplifications have been introduced in the dosimetric modeling for clinical trials of radioimmunotherapy. Although research efforts are generally needed to improve the simplifications used at each stage of model development, practical simplifications are often possible for specific applications without significant consequences to the dose-response model. In the development of dosimetric methodsmore » for radioimmunotherapy, practical simplifications in the dosimetric models were introduced. This study evaluated the magnitude of uncertainty associated with practical simplifications for: (1) organ mass of the MIRD phantom; (2) radiation contribution from target alone; (3) interpolation of S value; (4) macroscopic tumor uniformity; and (5) fit of tumor pharmacokinetic data.« less

Analysis of arsenical metabolites in biological samples.

PubMed

Hernandez-Zavala, Araceli; Drobna, Zuzana; Styblo, Miroslav; Thomas, David J

2009-11-01

Quantitation of iAs and its methylated metabolites in biological samples provides dosimetric information needed to understand dose-response relations. Here, methods are described for separation of inorganic and mono-, di-, and trimethylated arsenicals by thin layer chromatography. This method has been extensively used to track the metabolism of the radionuclide [(73)As] in a variety of in vitro assay systems. In addition, a hydride generation-cryotrapping-gas chromatography-atomic absorption spectrometric method is described for the quantitation of arsenicals in biological samples. This method uses pH-selective hydride generation to differentiate among arsenicals containing trivalent or pentavalent arsenic.

"Supermarket Column Chromatography of Leaf Pigments" Revisited: Simple and Ecofriendly Separation of Plant Carotenoids, Chlorophylls, and Flavonoids from Green and Red Leaves

ERIC Educational Resources Information Center

Dias, Alice M.; Ferreira, Maria La Salete

2015-01-01

A simple and ecofriendly procedure was developed in order to prepare extracts from red and green leaves. This procedure enables the separation of yellow, green, and red band pigments and optimizes the previously reported baking soda "supermarket column". The same extract also led to a novel and colorful potato starch column, which can…

Study of the Phototransference in GR-200 Dosimetric Material and its Convenience for Dose Re-estimation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baly, L.; Otazo, M. R.; Molina, D.

2006-09-08

A study of the phototransference of charges from deep to dosimetric traps in GR-200 material is presented and its convenience for dose re-estimation in the dose range between 2 and 100mSv is also analyzed. The recovering coefficient (RC) defined as the ratio between the phototransferred thermoluminescence (PTTL) and the original thermoluminescence (TL) of the dosimetric trap was used to evaluate the ratio of phototransferred charges from deep traps and the original charges in the dosimetric traps. The results show the convenience of this method for dose re-estimation for this material in the selected range of doses.

Scaling leaf respiration with nitrogen and phosphorus in tropical forests across two continents.

PubMed

Rowland, Lucy; Zaragoza-Castells, Joana; Bloomfield, Keith J; Turnbull, Matthew H; Bonal, Damien; Burban, Benoit; Salinas, Norma; Cosio, Eric; Metcalfe, Daniel J; Ford, Andrew; Phillips, Oliver L; Atkin, Owen K; Meir, Patrick

2017-05-01

Leaf dark respiration (R dark ) represents an important component controlling the carbon balance in tropical forests. Here, we test how nitrogen (N) and phosphorus (P) affect R dark and its relationship with photosynthesis using three widely separated tropical forests which differ in soil fertility. R dark was measured on 431 rainforest canopy trees, from 182 species, in French Guiana, Peru and Australia. The variation in R dark was examined in relation to leaf N and P content, leaf structure and maximum photosynthetic rates at ambient and saturating atmospheric CO 2 concentration. We found that the site with the lowest fertility (French Guiana) exhibited greater rates of R dark per unit leaf N, P and photosynthesis. The data from Australia, for which there were no phylogenetic overlaps with the samples from the South American sites, yielded the most distinct relationships of R dark with the measured leaf traits. Our data indicate that no single universal scaling relationship accounts for variation in R dark across this large biogeographical space. Variability between sites in the absolute rates of R dark and the R dark  : photosynthesis ratio were driven by variations in N- and P-use efficiency, which were related to both taxonomic and environmental variability. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Leaf trait dissimilarities between Dutch elm hybrids with a contrasting tolerance to Dutch elm disease.

PubMed

Durkovic, Jaroslav; Canová, Ingrid; Lagana, Rastislav; Kucerová, Veronika; Moravcík, Michal; Priwitzer, Tibor; Urban, Josef; Dvorák, Milon; Krajnáková, Jana

2013-02-01

Previous studies have shown that Ophiostoma novo-ulmi, the causative agent of Dutch elm disease (DED), is able to colonize remote areas in infected plants of Ulmus such as the leaf midrib and secondary veins. The objective of this study was to compare the performances in leaf traits between two Dutch elm hybrids 'Groeneveld' and 'Dodoens' which possess a contrasting tolerance to DED. Trait linkages were also tested with leaf mass per area (LMA) and with the reduced Young's modulus of elasticity (MOE) as a result of structural, developmental or functional linkages. Measurements and comparisons were made of leaf growth traits, primary xylem density components, gas exchange variables and chlorophyll a fluorescence yields between mature plants of 'Groeneveld' and 'Dodoens' grown under field conditions. A recently developed atomic force microscopy technique, PeakForce quantitative nanomechanical mapping, was used to reveal nanomechanical properties of the cell walls of tracheary elements such as MOE, adhesion and dissipation. 'Dodoens' had significantly higher values for LMA, leaf tissue thickness variables, tracheary element lumen area (A), relative hydraulic conductivity (RC), gas exchange variables and chlorophyll a fluorescence yields. 'Groeneveld' had stiffer cell walls of tracheary elements, and higher values for water-use efficiency and leaf water potential. Leaves with a large carbon and nutrient investment in LMA tended to have a greater leaf thickness and a higher net photosynthetic rate, but LMA was independent of RC. Significant linkages were also found between the MOE and some vascular traits such as RC, A and the number of tracheary elements per unit area. Strong dissimilarities in leaf trait performances were observed between the examined Dutch elm hybrids. Both hybrids were clearly separated from each other in the multivariate leaf trait space. Leaf growth, vascular and gas exchange traits in the infected plants of 'Dodoens' were unaffected by the DED fungus. 'Dodoens' proved to be a valuable elm germplasm for further breeding strategies.

Stomatal clustering in Begonia associates with the kinetics of leaf gaseous exchange and influences water use efficiency

PubMed Central

Papanatsiou, Maria; Amtmann, Anna

2017-01-01

Abstract Stomata are microscopic pores formed by specialized cells in the leaf epidermis and permit gaseous exchange between the interior of the leaf and the atmosphere. Stomata in most plants are separated by at least one epidermal pavement cell and, individually, overlay a single substomatal cavity within the leaf. This spacing is thought to enhance stomatal function. Yet, there are several genera naturally exhibiting stomata in clusters and therefore deviating from the one-cell spacing rule with multiple stomata overlaying a single substomatal cavity. We made use of two Begonia species to investigate whether clustering of stomata alters guard cell dynamics and gas exchange under different light and dark treatments. Begonia plebeja, which forms stomatal clusters, exhibited enhanced kinetics of stomatal conductance and CO2 assimilation upon light stimuli that in turn were translated into greater water use efficiency. Our findings emphasize the importance of spacing in stomatal clusters for gaseous exchange and plant performance under environmentally limited conditions. PMID:28369641

Identification of Isolates that Cause a Leaf Spot Disease of Brassicas as Xanthomonas campestris pv. raphani and Pathogenic and Genetic Comparison with Related Pathovars.

PubMed

Vicente, J G; Everett, B; Roberts, S J

2006-07-01

ABSTRACT Twenty-five Xanthomonas isolates, including some isolates received as either X. campestris pv. armoraciae or pv. raphani, caused discrete leaf spot symptoms when spray-inoculated onto at least one Brassica oleracea cultivar. Twelve of these isolates and four other Xanthomonas isolates were spray- and pin-inoculated onto 21 different plant species/cultivars including horseradish (Armoracia rusticana), radish (Raphanus sativus), and tomato (Lycopersicon esculentum). The remaining 13 leaf spot isolates were spray-inoculated onto a subset of 10 plant species/cultivars. The leaf spot isolates were very aggressive on several Brassica spp., radish, and tomato causing leaf spots and dark sunken lesions on the middle vein, petiole, and stem. Based on the differential reactions of several Brassica spp. and radish cultivars, the leaf spot isolates were divided into three races, with races 1 and 3 predominating. A differential series was established to determine the race-type of isolates and a gene-for-gene model based on the interaction of two avirulence genes in the pathogen races and two matching resistance genes in the differential hosts is proposed. Repetitive-DNA polymerase chain reaction-based fingerprinting was used to assess the genetic diversity of the leaf spot isolates and isolates of closely related Xanthomonas pathovars. Although there was variability within each race, the leaf spot isolates were clustered separately from the X. campestris pv. campestris isolates. We propose that X. campestris isolates that cause a nonvascular leaf spot disease on Brassica spp. should be identified as pv. raphani and not pv. armoraciae. Race-type strains and a neopathotype strain for X. campestris pv. raphani are proposed.

Patterns of Leaf Biochemical and Structural Properties of Cerrado Life Forms: Implications for Remote Sensing

PubMed Central

Ball, Aaron; Sanchez-Azofeifa, Arturo; Portillo-Quintero, Carlos; Rivard, Benoit; Castro-Contreras, Saulo; Fernandes, Geraldo

2015-01-01

Aim The general goal of this study is to investigate and analyze patterns of ecophysiological leaf traits and spectral response among life forms (trees, shrubs and lianas) in the Cerrado ecosystem. In this study, we first tested whether life forms are discriminated through leaf level functional traits. We then explored the correlation between leaf-level plant functional traits and spectral reflectance. Location Serra do Cipo National Park, Minas Gerais, Brazil. Methods Six ecophysiological leaf traits were selected to best characterize differences between life forms in the woody plant community of the Cerrado. Results were compared to spectral vegetation indices to determine if plant groups provide means to separate leaf spectral responses. Results Values obtained from leaf traits were similar to results reported from other tropical dry sites. Trees and shrubs significantly differed from lianas in terms of the percentage of leaf water content and Specific Leaf Area. Spectral indices were insufficient to capture the differences of these key traits between groups, though indices were still adequately correlated to overall trait variation. Conclusion The importance of life forms as biochemical and structurally distinctive groups is a significant finding for future remote sensing studies of vegetation, especially in arid and semi-arid environments. The traits we found as indicative of these groups (SLA and water content) are good candidates for spectral characterization. Future studies need to use the full wavelength (400 nm–2500 nm) in order to capture the potential response of these traits. The ecological linkage to water balance and life strategies encourages these traits as starting points for modeling plant communities using hyperspectral remote sensing. PMID:25692675

Storage effects on genomic DNA in rolled and mature coca leaves.

PubMed

Johnson, Emanuel L; Kim, Soo-Hyung; Emche, Stephen D

2003-08-01

Rolled and mature leaf tissue was harvested from Erythroxylum coca var. coca Lam. (coca) to determine a method for storage that would maintain DNA with high quality and content up to 50 days. Harvesting coca leaf tissue under Andean field conditions often requires storage from 3 to 10 days before extraction where tissue integrity is lost. All samples of rolled and mature coca leaf tissue were harvested and separately stored fresh in RNAlater for 50 days at 4 degrees, -20 degrees, and 23 degrees C, while similar samples were air-dried for 72 h at 23 degrees C or oven-dried for 72 h at 40 degrees C after storage, before extraction. Triplicate samples of each tissue type were extracted for DNA at 10-day intervals and showed that DNA integrity and content were preserved in leaf tissue stored at 4 degrees and -20 degrees C for 50 days. Rolled and mature leaf tissue stored at 4 degrees, -20 degrees, and 23 degrees C showed insignificant degradation of DNA after 10 days, and by day 50, only leaf tissue stored at 4 degrees and -20 degrees C had not significantly degraded. All air- and oven-dried leaf tissue extracts showed degradation upon drying (day 0) and continuous degradation up to day 50, despite storage conditions. Amplified fragment length polymorphism analysis of DNA from rolled and mature leaf tissue of coca stored at 4 degrees and -20 degrees C for 0, 10, and 50 days showed that DNA integrity and content were preserved. We recommend that freshly harvested rolled or mature coca leaf tissue be stored at 4 degrees, -20 degrees, and 23 degrees C for 10 days after harvest, and if a longer storage is required, then store at 4 degrees or -20 degrees C.

Diurnal variations of vegetation canopy structure

NASA Technical Reports Server (NTRS)

Kimes, D. S.; Kirchner, J. A.

1983-01-01

The significance and magnitude of diurnal variations of vegetation canopy structure are reviewed. Diurnal leaf inclination-azimuth angle distributions of a soybean and cotton canopy were documented using a simple measurement technique. The precision of the measurements was on the order of + or -5 deg for the inclination and + or -14 deg for the azimuth. The experimental results and a review of the literature showed that this distribution can vary significantly on a diurnal basis due to vegetation type, heliotropic leaf movement, environmental conditions, and vegetation stress. The study also showed that it is erroneous to treat two separate distributions of azimuth and inclination angles rather than one three-dimensional distribution of leaf orientation. The latter distribution needs to be routinely collected in studies which document variations of diurnal spectral reflectance with changes in solar zenith angle.

PHYTOCHEMICAL SCREENING, ANTI-INFLAMMATORY AND ANALGESIC PROPERTIES OF PENTANISIA PRUNELLOIDES FROM THE EASTERN CAPE PROVINCE, SOUTH AFRICA.

PubMed

Mathews, Miya Gugulethu; Ajayi, Oyemitan Idris; Opeoluwa, Oyedeji Oyehan; Oluwatobi, Oluwafemi Samuel; Benedicta N, Nkeh-Chungag; Phindile, Songca Sandile; Oyedeji; Omowumi, Adebola

2016-01-01

Pentanisia prunelloides is a medicinal plant widely used to remedy various ailments including infections, fever and rheumatism in Eastern Cape Province of South Africa. There is scanty report on the phytochemical and biological properties of the plant; hence various solvent extracts of the dried plant materials were phytochemically screened, and its aqueous extract evaluated for acute toxicity effect, analgesic and antiinflammatory properties in rodents. Different extracts of both leaf and rhizome were obtained separately with ethanol, methanol and water. Portions of the filtrate were used for qualitative screening of secondary metabolites and remaining portions were concentrated and dried. Dried grounded leaf and rhizome of the plant were also used for quantitative screening for some major components. The aqueous extract of the leaf and rhizome were used for acute toxicity (LD 50 ) test, antiinflammatory and analgesic activities in rodents. The qualitative phytochemical screening showed the presence of several phytoconstituents with saponins, flavonoids and alkaloids constituting highest constituents in the leaf and rhizome. The LD50: of the aqueous extracts (from leaf or rhizome) was found to be ≥5000 mg/kg orally. The leaf and rhizome aqueous extract (250-500 mg/kg) significantly (p<0.01) reduced egg albumin-induced paw oedema and paw licking in mice induced by formalin, signifying antinociceptive and antiinflammatory activities respectively. It is concluded that the leaf and rhizome of P. prunelloides are rich in various phytochemicals which could be associated with their medicinal uses. The aqueous leaf and rhizome extracts are similarly non-toxic orally, showed antiinflammatory and analgesic potentials thus rationalizing its use in folkloric medicine.

Molecular analysis of new isolates of Tomato leaf curl Philippines virus and an associated betasatellite occurring in the Philippines.

PubMed

Sharma, Pradeep; Matsuda, N; Bajet, N B; Ikegami, M

2011-02-01

Three new begomovirus isolates and one betasatellite were obtained from a tomato plant exhibiting leaf curl symptom in Laguna, the Philippines. Typical begomovirus DNA components representing the three isolates (PH01, PH02 and PH03) were cloned, and their full-length sequences were determined to be 2754 to 2746 nucleotides. The genome organizations of these isolates were similar to those of other Old World monopartite begomoviruses. The sequence data indicated that PH01 and PH02 were variants of strain B of the species Tomato leaf curl Philippines virus, while PH03 was a variant of strain A of the species Tomato leaf curl Philippines virus. These isolates were designated ToLCPV-B[PH:Lag1:06], ToLCPV-B[PH:Lag2:06], and ToLCPV-A[PH:Lag3:06], respectively. Phylogenetic analysis revealed that the present isolates form a separate monophyletic cluster with indigenous begomoviruses reported earlier in the Philippines. A betasatellite isolated from same sample belongs to the betasatellite species Tomato leaf curl Philippines betasatellite and designated Tomato leaf curl Philippines betasatellite-[Philippines:Laguna1:2006], ToLCPHB-[PH:Lag1:06]. When co-inoculated with this betasatellite, tomato leaf curl Philippines virus induced severe symptoms in N. benthamiana and Solanum lycopersicum plants. Using a PVX-mediated transient assay, we found that the C4 and C2 proteins of tomato leaf curl Philippines virus and the βC1 protein of ToLCPHB-[PH:Lag1:06] function as a suppressor of RNA silencing.

Effects of nitrogen nutrition on the growth, yield and reflectance characteristics of corn canopies. [Purdue Agronomy Farm, Indiana

NASA Technical Reports Server (NTRS)

Bauer, M. E. (Principal Investigator); Walburg, G.; Daughtry, C. S. T.

1981-01-01

Spectral and agronomic measurements were collected from corn (Zea mays L.) canopies under four nitrogen treatment levels (0, 67, 134, and 202 kg/ha) on 11 dates during 1978 and 12 dates during 1979. Data were analyzed to determine the relationship between the spectral responses of canopies and their argonomic characteristics as well as the spectral separability of the four treatments. Red reflectance was increased, while the near infrared reflectance was decreased for canopies under nitrogen deprivation. Spectral differences between treatments were seen throughout each growing season. The near infrared/red reflectance ratio increased spectral treatment differences over those shown by single band reflectance measures. Of the spectral variables examined, the near infrared/red reflectance ratio most effectively separated the treatments. Differences in spectral response between treatments were attributed to varying soil cover, leaf area index, and leaf pigmentation values, all of which changed with N treatment.

An improved Monte-Carlo model of the Varian EPID separating support arm and rear-housing backscatter

NASA Astrophysics Data System (ADS)

Monville, M. E.; Kuncic, Z.; Greer, P. B.

2014-03-01

Previous investigators of EPID dosimetric properties have ascribed the backscatter, that contaminates dosimetric EPID images, to its supporting arm. Accordingly, Monte-Carlo (MC) EPID models have approximated the backscatter signal from the layers under the detector and the robotic support arm using either uniform or non-uniform solid water slabs, or through convolutions with back-scatter kernels. The aim of this work is to improve the existent MC models by measuring and modelling the separate backscatter contributions of the robotic arm and the rear plastic housing of the EPID. The EPID plastic housing is non-uniform with a 11.9 cm wide indented section that runs across the cross-plane direction in the superior half of the EPID which is 1.75 cm closer to the EPID sensitive layer than the rest of the housing. The thickness of the plastic housing is 0.5 cm. Experiments were performed with and without the housing present by removing all components of the EPID from the housing. The robotic support arm was not present for these measurements. A MC model of the linear accelerator and the EPID was modified to include the rear-housing indentation and results compared to the measurement. The rear housing was found to contribute a maximum of 3% additional signal. The rear housing contribution to the image is non-uniform in the in-plane direction with 2% asymmetry across the central 20 cm of an image irradiating the entire detector. The MC model was able to reproduce this non-uniform contribution. The EPID rear housing contributes a non-uniform backscatter component to the EPID image, which has not been previously characterized. This has been incorporated into an improved MC model of the EPID.

Cloud Classification in Polar and Desert Regions and Smoke Classification from Biomass Burning Using a Hierarchical Neural Network

NASA Technical Reports Server (NTRS)

Alexander, June; Corwin, Edward; Lloyd, David; Logar, Antonette; Welch, Ronald

1996-01-01

This research focuses on a new neural network scene classification technique. The task is to identify scene elements in Advanced Very High Resolution Radiometry (AVHRR) data from three scene types: polar, desert and smoke from biomass burning in South America (smoke). The ultimate goal of this research is to design and implement a computer system which will identify the clouds present on a whole-Earth satellite view as a means of tracking global climate changes. Previous research has reported results for rule-based systems (Tovinkere et at 1992, 1993) for standard back propagation (Watters et at. 1993) and for a hierarchical approach (Corwin et al 1994) for polar data. This research uses a hierarchical neural network with don't care conditions and applies this technique to complex scenes. A hierarchical neural network consists of a switching network and a collection of leaf networks. The idea of the hierarchical neural network is that it is a simpler task to classify a certain pattern from a subset of patterns than it is to classify a pattern from the entire set. Therefore, the first task is to cluster the classes into groups. The switching, or decision network, performs an initial classification by selecting a leaf network. The leaf networks contain a reduced set of similar classes, and it is in the various leaf networks that the actual classification takes place. The grouping of classes in the various leaf networks is determined by applying an iterative clustering algorithm. Several clustering algorithms were investigated, but due to the size of the data sets, the exhaustive search algorithms were eliminated. A heuristic approach using a confusion matrix from a lightly trained neural network provided the basis for the clustering algorithm. Once the clusters have been identified, the hierarchical network can be trained. The approach of using don't care nodes results from the difficulty in generating extremely complex surfaces in order to separate one class from all of the others. This approach finds pairwise separating surfaces and forms the more complex separating surface from combinations of simpler surfaces. This technique both reduces training time and improves accuracy over the previously reported results. Accuracies of 97.47%, 95.70%, and 99.05% were achieved for the polar, desert and smoke data sets.

Response of vegetation indices to changes in three measures of leaf water stress

NASA Technical Reports Server (NTRS)

Cohen, Warren B.

1991-01-01

The responses of vegetation indices to changes in water stress were evaluated in two separate laboratory experiments. In one experiment the normalized difference vegetation index (NDVI), the near-IR to red ratio (near-IR/red), the Infrared Index (II), and the Moisture Stress Index (MSI) were more highly correlated to leaf water potential in lodgepole pine branches than were the Leaf Water Content Index (LWCI), the mid-IR ratio (Mid-IR), or any of the single Thematic Mapper (TM) bands. In the other experiment, these six indices and the TM Tasseled Cap brightness, greenness, and wetness indices responded to changes in leaf relative water content (RWC) differently than they responded to changes in leaf water content (WC) of three plant species, and the responses were dependent on how experimental replicates were pooled. With no pooling, the LWCI was the most highly correlated index to both RWC and WC among replications, followed by the II, MSI, and wetness. Only the LWCI was highly correlated to RWC and WC when replications were pooled within species. With among species pooling the LWCI was the only index highly correlated with RWC, while the II, MSI, Mid-IR, and wetness were most highly correlated with WC.

Antihyperglycemic effects of separate and composite extract of root of Musa paradisiaca and leaf of Coccinia indica in streptozotocin-induced diabetic male albino rat.

PubMed

Mallick, Chhanda; Chatterjee, Kausik; Guhabiswas, Mehuli; Ghosh, Debidas

2007-02-16

We evaluated the antihyperglycaemic properties of aqueous-methanolic (40:60) extract of root of Musa paradisiaca and leaf of Coccinia indica in separate as well as in composite manner by conducting experiment on streptozotocin-induced diabetic rats. We measured food and water intake ability, the fasting blood glucose level, glucose tolerance, activities of important carbohydrate metabolic enzymes like glucose-6-phosphatase, glucose-6-phosphate dehydrogenase, hexokinase in liver along with quantification of glycogen in liver and in skeletal muscle and serum insulin level. We noted that after treatment of aqueous methanolic extract of above plant parts in separate as well as in composite manner at a concentration of 80 mg/100 g body weight/day to streptozotocin-induced diabetic rat resulted in a significant remedial effect on blood glucose level as well as carbohydrate metabolic enzymes and the quantity of liver and skeletal muscle glycogen. Serum insulin level that was diminished in streptozotocin-induced diabetic rat recovered significantly after the co-administration of extract of above plant parts. All the above parameters showed a more potent remedial effect after composite extract treatment with respect to separate treatment and none of the extract has any general metabolic toxicity induction.

Breakdown of middle lamella pectin by (●) OH during rapid abscission in Azolla.

PubMed

Yamada, Yoshiya; Koibuchi, Mizuki; Miyamoto, Kensuke; Ueda, Junichi; Uheda, Eiji

2015-08-01

Azolla, a small water fern, abscises its roots and branches within 30 min upon treatment with various stresses. This study was conducted to test whether, in the rapid abscission that occurs in Azolla, breakdown of wall components of abscission zone cells by (●) OH is involved. Experimentally generated (●) OH caused the rapid separation of abscission zone cells from detached roots and the rapid shedding of roots from whole plants. Electron microscopic observations revealed that (●) OH rapidly and selectively dissolved a well-developed middle lamella between abscission zone cells and resultantly caused rapid cell separation and shedding. Treatment of abscission zones of Impatiens leaf petiole with (●) OH also accelerated the separation of abscission zone cells. However, compared with that of Azolla roots, accelerative effects in Impatiens were weak. A large amount of (●) OH was cytochemically detected in abscission zone cells both of Azolla roots and of Impatiens leaf petioles. These results suggest that (●) OH is involved in the cell separation process not only in the rapid abscission in Azolla but also in the abscission of Impatiens. However, for rapid abscission to occur, a well-developed middle lamella, a unique structure, which is sensitive to the attack of (●) OH, might be needed. © 2015 John Wiley & Sons Ltd.

Dosimetric audit in brachytherapy

PubMed Central

Bradley, D A; Nisbet, A

2014-01-01

Dosimetric audit is required for the improvement of patient safety in radiotherapy and to aid optimization of treatment. The reassurance that treatment is being delivered in line with accepted standards, that delivered doses are as prescribed and that quality improvement is enabled is as essential for brachytherapy as it is for the more commonly audited external beam radiotherapy. Dose measurement in brachytherapy is challenging owing to steep dose gradients and small scales, especially in the context of an audit. Several different approaches have been taken for audit measurement to date: thimble and well-type ionization chambers, thermoluminescent detectors, optically stimulated luminescence detectors, radiochromic film and alanine. In this work, we review all of the dosimetric brachytherapy audits that have been conducted in recent years, look at current audits in progress and propose required directions for brachytherapy dosimetric audit in the future. The concern over accurate source strength measurement may be essentially resolved with modern equipment and calibration methods, but brachytherapy is a rapidly developing field and dosimetric audit must keep pace. PMID:24807068

Reversible Deformation of Transfusion Tracheids in Taxus baccata Is Associated with a Reversible Decrease in Leaf Hydraulic Conductance1[OPEN

PubMed Central

Zhang, Yong-Jiang; Rockwell, Fulton E.; Wheeler, James K.; Holbrook, N. Michele

2014-01-01

Declines in leaf hydraulic conductance (Kleaf) with increasing water stress have been attributed to cavitation of the leaf xylem. However, in the leaves of conifers, the reversible collapse of transfusion tracheids may provide an alternative explanation. Using Taxus baccata, a conifer species without resin, we developed a modified rehydration technique that allows the separation of declines in Kleaf into two components: one reversible and one irreversible upon relaxation of water potential to −1 MPa. We surveyed leaves at a range of water potentials for evidence of cavitation using cryo-scanning electron microscopy and quantified dehydration-induced structural changes in transfusion tracheids by cryo-fluorescence microscopy. Irreversible declines in Kleaf did not occur until leaf water potentials were more negative than −3 MPa. Declines in Kleaf between −2 and −3 MPa were reversible and accompanied by the collapse of transfusion tracheids, as evidenced by cryo-fluorescence microscopy. Based on cryo-scanning electron microscopy, cavitation of either transfusion or xylem tracheids did not contribute to declines in Kleaf in the reversible range. Moreover, the deformation of transfusion tracheids was quickly reversible, thus acting as a circuit breaker regulating the flux of water through the leaf vasculature. As transfusion tissue is present in all gymnosperms, the reversible collapse of transfusion tracheids may be a general mechanism in this group for the protection of leaf xylem from excessive loads generated in the living leaf tissue. PMID:24948828

Relationship of leaf oxygen and carbon isotopic composition with transpiration efficiency in the C4 grasses Setaria viridis and Setaria italica.

PubMed

Ellsworth, Patrick Z; Ellsworth, Patrícia V; Cousins, Asaph B

2017-06-15

Leaf carbon and oxygen isotope ratios can potentially provide a time-integrated proxy for stomatal conductance (gs) and transpiration rate (E), and can be used to estimate transpiration efficiency (TE). In this study, we found significant relationships of bulk leaf carbon isotopic signature (δ13CBL) and bulk leaf oxygen enrichment above source water (Δ18OBL) with gas exchange and TE in the model C4 grasses Setaria viridis and S. italica. Leaf δ13C had strong relationships with E, gs, water use, biomass, and TE. Additionally, the consistent difference in δ13CBL between well-watered and water-limited plants suggests that δ13CBL is effective in separating C4 plants with different availability of water. Alternatively, the use of Δ18OBL as a proxy for E and TE in S. viridis and S. italica was problematic. First, the oxygen isotopic composition of source water, used to calculate leaf water enrichment (Δ18OLW), was variable with time and differed across water treatments. Second, water limitations changed leaf size and masked the relationship of Δ18OLW and Δ18OBL with E. Therefore, the data collected here suggest that δ13CBL but not Δ18OBL may be an effective proxy for TE in C4 grasses. © The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Revision of the dosimetric parameters of the CSM11 LDR Cs-137 source.

PubMed

Otal, Antonio; Martínez-Fernández, Juan Manuel; Granero, Domingo

2011-03-01

The clinical use of brachytherapy sources requires the existence of dosimetric data with enough of quality for the proper application of treatments in clinical practice. It has been found that the published data for the low dose rate CSM11 Cs-137 source lacks of smoothness in some regions because the data are too noisy. The purpose of this study was to calculate the dosimetric data for this source in order to provide quality dosimetric improvement of the existing dosimetric data of Ballester et al . [1]. In order to obtain the dose rate distributions Monte Carlo simulations were done using the GEANT4 code. A spherical phantom 40 cm in radius with the Cs-137 source located at the centre of the phantom was used. The results from Monte Carlo simulations were applied to derive AAPM Task Group 43 dosimetric parameters: anisotropy function, radial dose function, air kerma strength and dose rate constant. The dose rate constant obtained was 1.094 ± 0.002 cGy h -1 U -1 . The new calculated data agrees within experimental uncertainties with the existing data of Ballester et al . but without the statistical noise of that study. The obtained data presently fulfills all the requirements of the TG-43U1 update and thus it can be used in clinical practice.

Poster - 53: Improving inter-linac DMLC IMRT dose precision by fine tuning of MLC leaf calibration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakonechny, Keith; Tran, Muoi; Sasaki, David

Purpose: To develop a method to improve the inter-linac precision of DMLC IMRT dosimetry. Methods: The distance between opposing MLC leaf banks (“gap size”) can be finely tuned on Varian linacs. The dosimetric effect due to small deviations from the nominal gap size (“gap error”) was studied by introducing known errors for several DMLC sliding gap sizes, and for clinical plans based on the TG119 test cases. The plans were delivered on a single Varian linac and the relationship between gap error and the corresponding change in dose was measured. The plans were also delivered on eight Varian 2100 seriesmore » linacs (at two institutions) in order to quantify the inter-linac variation in dose before and after fine tuning the MLC calibration. Results: The measured dose differences for each field agreed well with the predictions of LoSasso et al. Using the default MLC calibration, the variation in the physical MLC gap size was determined to be less than 0.4 mm between all linacs studied. The dose difference between the linacs with the largest and smallest physical gap was up to 5.4% (spinal cord region of the head and neck TG119 test case). This difference was reduced to 2.5% after fine tuning the MLC gap calibration. Conclusions: The inter-linac dose precision for DMLC IMRT on Varian linacs can be improved using a simple modification of the MLC calibration procedure that involves fine adjustment of the nominal gap size.« less

Separating foliar physiology from morphology reveals the relative roles of vertically structured transpiration factors within red maple crowns and limitations of larger scale models

PubMed Central

Bauerle, William L.; Bowden, Joseph D.

2011-01-01

A spatially explicit mechanistic model, MAESTRA, was used to separate key parameters affecting transpiration to provide insights into the most influential parameters for accurate predictions of within-crown and within-canopy transpiration. Once validated among Acer rubrum L. genotypes, model responses to different parameterization scenarios were scaled up to stand transpiration (expressed per unit leaf area) to assess how transpiration might be affected by the spatial distribution of foliage properties. For example, when physiological differences were accounted for, differences in leaf width among A. rubrum L. genotypes resulted in a 25% difference in transpiration. An in silico within-canopy sensitivity analysis was conducted over the range of genotype parameter variation observed and under different climate forcing conditions. The analysis revealed that seven of 16 leaf traits had a ≥5% impact on transpiration predictions. Under sparse foliage conditions, comparisons of the present findings with previous studies were in agreement that parameters such as the maximum Rubisco-limited rate of photosynthesis can explain ∼20% of the variability in predicted transpiration. However, the spatial analysis shows how such parameters can decrease or change in importance below the uppermost canopy layer. Alternatively, model sensitivity to leaf width and minimum stomatal conductance was continuous along a vertical canopy depth profile. Foremost, transpiration sensitivity to an observed range of morphological and physiological parameters is examined and the spatial sensitivity of transpiration model predictions to vertical variations in microclimate and foliage density is identified to reduce the uncertainty of current transpiration predictions. PMID:21617246

Fast detection of leaf pigments and isoprenoids for ecophysiological studies, plant phenotyping and validating remote-sensing of vegetation.

PubMed

Junker, Laura V; Ensminger, Ingo

2016-12-01

Rapid developments in remote-sensing of vegetation and high-throughput precision plant phenotyping promise a range of real-life applications using leaf optical properties for non-destructive assessment of plant performance. Use of leaf optical properties for assessing plant performance requires the ability to use photosynthetic pigments as proxies for physiological properties and the ability to detect these pigments fast, reliably and at low cost. We describe a simple and cost-effective protocol for the rapid analysis of chlorophylls, carotenoids and tocopherols using high-performance liquid chromatography (HPLC). Many existing methods are based on the expensive solvent acetonitrile, take a long time or do not include lutein epoxide and α-carotene. We aimed to develop an HPLC method which separates all major chlorophylls and carotenoids as well as lutein epoxide, α-carotene and α-tocopherol. Using a C 30 -column and a mobile phase with a gradient of methanol, methyl-tert-butyl-ether (MTBE) and water, our method separates the above pigments and isoprenoids within 28 min. The broad applicability of our method is demonstrated using samples from various plant species and tissue types, e.g. leaves of Arabidopsis and avocado plants, several deciduous and conifer tree species, various crops, stems of parasitic dodder, fruit of tomato, roots of carrots and Chlorella algae. In comparison to previous methods, our method is very affordable, fast and versatile and can be used to analyze all major photosynthetic pigments that contribute to changes in leaf optical properties and which are of interest in most ecophysiological studies. © 2016 Scandinavian Plant Physiology Society.

Improvements in critical dosimetric endpoints using the Contura multilumen balloon breast brachytherapy catheter to deliver accelerated partial breast irradiation: preliminary dosimetric findings of a phase iv trial.

PubMed

Arthur, Douglas W; Vicini, Frank A; Todor, Dorin A; Julian, Thomas B; Lyden, Maureen R

2011-01-01

Dosimetric findings in patients treated with the Contura multilumen balloon (MLB) breast brachytherapy catheter to deliver accelerated partial breast irradiation (APBI) on a multi-institutional Phase IV registry trial are presented. Computed tomography-based three-dimensional planning with dose optimization was performed. For the trial, new ideal dosimetric goals included (1) ≥95% of the prescribed dose (PD) covering ≥90% of the target volume, (2) a maximum skin dose ≤125% of the PD, (3) maximum rib dose ≤145% of the PD, and (4) the V150 ≤50 cc and V200 ≤10 cc. The ability to concurrently achieve these dosimetric goals using the Contura MLB was analyzed. 144 cases were available for review. Using the MLB, all dosimetric criteria were met in 76% of cases. Evaluating dosimetric criteria individually, 92% and 89% of cases met skin and rib dose criteria, respectively. In 93% of cases, ideal target volume coverage goals were met, and in 99%, dose homogeneity criteria (V150 and V200) were satisfied. When skin thickness was ≥5 mm to <7 mm, the median skin dose was limited to 120.1% of the PD, and when skin thickness was <5 mm, the median skin dose was 124.2%. When rib distance was <5 mm, median rib dose was reduced to 136.5% of the PD. When skin thickness was <7 mm and distance to rib was <5 mm, median skin and rib doses were jointly limited to 120.6% and 142.1% of the PD, respectively. The Contura MLB catheter provided the means of achieving the imposed higher standard of dosimetric goals in the majority of clinical scenarios encountered. Copyright © 2011 Elsevier Inc. All rights reserved.

TU-CD-BRB-01: Normal Lung CT Texture Features Improve Predictive Models for Radiation Pneumonitis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krafft, S; The University of Texas Graduate School of Biomedical Sciences, Houston, TX; Briere, T

2015-06-15

Purpose: Existing normal tissue complication probability (NTCP) models for radiation pneumonitis (RP) traditionally rely on dosimetric and clinical data but are limited in terms of performance and generalizability. Extraction of pre-treatment image features provides a potential new category of data that can improve NTCP models for RP. We consider quantitative measures of total lung CT intensity and texture in a framework for prediction of RP. Methods: Available clinical and dosimetric data was collected for 198 NSCLC patients treated with definitive radiotherapy. Intensity- and texture-based image features were extracted from the T50 phase of the 4D-CT acquired for treatment planning. Amore » total of 3888 features (15 clinical, 175 dosimetric, and 3698 image features) were gathered and considered candidate predictors for modeling of RP grade≥3. A baseline logistic regression model with mean lung dose (MLD) was first considered. Additionally, a least absolute shrinkage and selection operator (LASSO) logistic regression was applied to the set of clinical and dosimetric features, and subsequently to the full set of clinical, dosimetric, and image features. Model performance was assessed by comparing area under the curve (AUC). Results: A simple logistic fit of MLD was an inadequate model of the data (AUC∼0.5). Including clinical and dosimetric parameters within the framework of the LASSO resulted in improved performance (AUC=0.648). Analysis of the full cohort of clinical, dosimetric, and image features provided further and significant improvement in model performance (AUC=0.727). Conclusions: To achieve significant gains in predictive modeling of RP, new categories of data should be considered in addition to clinical and dosimetric features. We have successfully incorporated CT image features into a framework for modeling RP and have demonstrated improved predictive performance. Validation and further investigation of CT image features in the context of RP NTCP modeling is warranted. This work was supported by the Rosalie B. Hite Fellowship in Cancer research awarded to SPK.« less

TU-F-17A-06: Motion Stability and Dosimetric Impact of Spirometer-Based DIBH-RT of Left-Sided Breast Cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

McKenzie, E; Yang, W; Burnison, M

2014-06-15

Purpose: Patients undergoing radiotherapy (RT) for left-sided breast cancer have increased risk of coronary artery disease. Deep Inhalation Breath Hold assisted RT (DIBH-RT) is shown to increase the geometric separation of the target area and heart, reducing cardiac radiation dose. The purposes of this study are to use Cine MV portal images to determine the stability of spirometer-guided DIBH-RT and examine the dosimetric cardiopulmonary impact of this technique. Methods: Twenty consecutive patients with left-sided breast cancer were recruited to the IRB-approved study. Free-breathing (FB) and DIBH-CT's were acquired at simulation. Rigid registration of the FB-CT and DIBH-CT was performed usingmore » primarily breast tissue. Treatment plans were created for each FB-CT and DIBH-CT using identical paired tangent fields with field-in-field or electronic compensation techniques. Dosimetric evaluation included mean and maximum (Dmax) doses for the left anterior descending artery (LAD), mean heart dose, and left lung V20. Cine MV portal images were acquired for medial and lateral fields during treatment. Analysis of Cine images involved chest wall segmentation using an algorithm developed in-house. Intra- and inter-fractional chest wall motion were determined through affine registration to the first frame of each Cine. Results: Dose to each cardiac structure evaluated was significantly (p<0.001) reduced with the DIBH plans. Mean heart dose decreased from 2.9(0.9–6.6) to 1.6(0.6–5.3) Gy; mean LAD dose from 16.6(3–43.6) to 7.4(1.7–32.7) Gy; and LAD Dmax from 35.4 (6.1–53) to 18.4(2.5–51.2) Gy. No statistically significant reduction was found for the left lung V20. Average AP and SI median chest wall motion (intrafractional) was 0.1 (SD=0.9) and 0.5 (SD=1.1) mm, respectively. Average AP inter-fractional chest wall motion was 2.0 (SD=1.4) mm. Conclusion: Spirometer-based DIBH treatments of the left breast are reproducible both inter- and intra-fractionally, and provide a statistically and potentially clinically useful dosimetric advantage to cardiac structures.« less

[Effects of mixed decomposition of Populus simonii and other tree species leaf litters on soil properties in Loess Plateau].

PubMed

Li, Qian; Liu, Zeng-Wen; Du, Liang-Zhen

2012-03-01

In this study, the leaf litters of Populus simonii and other 11 tree species were put into soil separately or in mixture after grinding, and incubated in laboratory to analyze the effects of their decomposition on soil properties and the interactions between the litters decomposition. The decomposition of each kind of the leaf litters in soil increased the soil urease, dehydrogenase, and phosphatase activities and the soil organic matter and available N contents markedly, but had greater differences in the effects on the soil available P content and CEC. The decomposition of the leaf litters of Caragana microphylla and of Amorpha fruticosa showed obvious effects in improving soil properties. The decomposition of the mixed leaf litters of P. simonii and Pinus tabulaeformis, Platycladus orientalis, Robinia pseudoacacia, or Ulmus pumila showed interactive promotion effects on the abundance of soil microbes, and that of the mixed leaf litters of P. simonii and P. orientalis or C. microphylla showed interactive promotion effects on the soil organic matter, available P, and available K contents and soil CEC but interactive inhibition effects on the activities of most of the soil enzymes tested. The decomposition of the mixed leaf litters of P. simonii and Larix principis-rupprechtii showed interactive promotion effects on the activities of most of the soil enzymes and soil nutrient contents, while that of the mixed leaf litters of P. simonii and P. sylvestris var. mongolica showed interactive inhibition effects. Overall, the decomposition of the mixed leaf litters of P. simo- nii and U. pumila, P. tabulaeformis, L. principis-rupprechtii, or R. pseudoacacia could improve soil quality, but the mixed leaf litters of P. simonii and P. orientalis, C. microphylla, P. sylvestris var. mongolica, Hippophae rhamnoides, or A. fruticosa showed an interactive inhibition effect during their decomposition.

Dosimetric assessment of the PRESAGE dosimeter for a proton pencil beam

NASA Astrophysics Data System (ADS)

Wuu, C.-S.; Xu, Y.; Qian, X.; Adamovics, J.; Cascio, E.; Lu, H.-M.

2013-06-01

The objective of this study is to assess the feasibility of using PRESAGE dosimeters for proton pencil beam dosimetry. Two different formulations of phantom materials were tested for their suitability in characterizing a single proton pencil beam. The dosimetric response of PRESAGE was found to be linear up to 4Gy. First-generation optical CT scanner, OCTOPUSTM was used to implement dose distributions for proton pencil beams since it provides most accurate readout. Percentage depth dose curves and beam profiles for two proton energy, 110 MeV, and 93 MeV, were used to evaluate the dosimetric performance of two PRESAGE phantom formulas. The findings from this study show that the dosimetric properties of the phantom materials match with basic physics of proton beams.

Arabidopsis ASYMMETRIC LEAVES2 protein required for leaf morphogenesis consistently forms speckles during mitosis of tobacco BY-2 cells via signals in its specific sequence.

PubMed

Luo, Lilan; Ando, Sayuri; Sasabe, Michiko; Machida, Chiyoko; Kurihara, Daisuke; Higashiyama, Tetsuya; Machida, Yasunori

2012-09-01

Leaf primordia with high division and developmental competencies are generated around the periphery of stem cells at the shoot apex. Arabidopsis ASYMMETRIC-LEAVES2 (AS2) protein plays a key role in the regulation of many genes responsible for flat symmetric leaf formation. The AS2 gene, expressed in leaf primordia, encodes a plant-specific nuclear protein containing an AS2/LOB domain with cysteine repeats (C-motif). AS2 proteins are present in speckles in and around the nucleoli, and in the nucleoplasm of some leaf epidermal cells. We used the tobacco cultured cell line BY-2 expressing the AS2-fused yellow fluorescent protein to examine subnuclear localization of AS2 in dividing cells. AS2 mainly localized to speckles (designated AS2 bodies) in cells undergoing mitosis and distributed in a pairwise manner during the separation of sets of daughter chromosomes. Few interphase cells contained AS2 bodies. Deletion analyses showed that a short stretch of the AS2 amino-terminal sequence and the C-motif play negative and positive roles, respectively, in localizing AS2 to the bodies. These results suggest that AS2 bodies function to properly distribute AS2 to daughter cells during cell division in leaf primordia; and this process is controlled at least partially by signals encoded by the AS2 sequence itself.

Leaf gas films contribute to rice (Oryza sativa) submergence tolerance during saline floods.

PubMed

Herzog, Max; Konnerup, Dennis; Pedersen, Ole; Winkel, Anders; Colmer, Timothy David

2018-05-01

Floods and salinization of agricultural land adversely impact global rice production. We investigated whether gas films on leaves of submerged rice delay salt entry during saline submergence. Two-week-old plants with leaf gas films (+GF) or with gas films experimentally removed (-GF) were submerged in artificial floodwater with 0 or 50 mm NaCl for up to 16 d. Gas films were present >9 d on GF plants after which gas films were diminished. Tissue ion analysis (Na + , Cl - and K + ) showed that gas films caused some delay of Na + entry, as leaf Na + concentration was 36-42% higher in -GF leaves than +GF leaves on days 1-5. However, significant net uptakes of Na + and Cl - , and K + net loss, occurred despite the presence of gas films, indicating the likely presence of some leaf-to-floodwater contact, so that the gas layer must not have completely separated the leaf surfaces from the water. Natural loss and removal of gas films resulted in severe declines in growth, underwater photosynthesis, chlorophyll a and tissue porosity. Submergence was more detrimental to leaf P N and growth than the additional effect of 50 mm NaCl, as salt did not significantly affect underwater P N at 200 μm CO 2 nor growth. © 2016 John Wiley & Sons Ltd.

Foliage motion under wind, from leaf flutter to branch buffeting.

PubMed

Tadrist, Loïc; Saudreau, Marc; Hémon, Pascal; Amandolese, Xavier; Marquier, André; Leclercq, Tristan; de Langre, Emmanuel

2018-05-01

The wind-induced motion of the foliage in a tree is an important phenomenon both for biological issues (photosynthesis, pathogens development or herbivory) and for more subtle effects such as on wi-fi transmission or animal communication. Such foliage motion results from a combination of the motion of the branches that support the leaves, and of the motion of the leaves relative to the branches. Individual leaf dynamics relative to the branch, and branch dynamics have usually been studied separately. Here, in an experimental study on a whole tree in a large-scale wind tunnel, we present the first empirical evidence that foliage motion is actually dominated by individual leaf flutter at low wind velocities, and by branch turbulence buffeting responses at higher velocities. The transition between the two regimes is related to a weak dependence of leaf flutter on wind velocity, while branch turbulent buffeting is strongly dependent on it. Quantitative comparisons with existing engineering-based models of leaf and branch motion confirm the prevalence of these two mechanisms. Simultaneous measurements of the wind-induced drag on the tree and of the light interception by the foliage show the role of an additional mechanism, reconfiguration, whereby leaves bend and overlap, limiting individual leaf flutter. We then discuss the consequences of these findings on the role of wind-mediated phenomena. © 2018 The Author(s).

Leaf Surface Effects on Retrieving Chlorophyll Content from Hyperspectral Remote Sensing

NASA Astrophysics Data System (ADS)

Qiu, Feng; Chen, JingMing; Ju, Weimin; Wang, Jun; Zhang, Qian

2017-04-01

Light reflected directly from the leaf surface without entering the surface layer is not influenced by leaf internal biochemical content. Leaf surface reflectance varies from leaf to leaf due to differences in the surface roughness features and is relatively more important in strong absorption spectral regions. Therefore it introduces dispersion of data points in the relationship between biochemical concentration and reflectance (especially in the visible region). Separation of surface from total leaf reflection is important to improve the link between leaf pigments content and remote sensing data. This study aims to estimate leaf surface reflectance from hyperspectral remote sensing data and retrieve chlorophyll content by inverting a modified PROSPECT model. Considering leaf surface reflectance is almost the same in the visible and near infrared spectral regions, a surface layer with a reflectance independent of wavelength but varying from leaf to leaf was added to the PROSPECT model. The specific absorption coefficients of pigments were recalibrated. Then the modified model was inverted on independent datasets to check the performance of the model in predicting the chlorophyll content. Results show that differences in estimated surface layer reflectance of various species are noticeable. Surface reflectance of leaves with epicuticular waxes and trichomes is usually higher than other samples. Reconstruction of leaf reflectance and transmittance in the 400-1000 nm wavelength region using the modified PROSPECT model is excellent with low root mean square error (RMSE) and bias. Improvements for samples with high surface reflectance (e.g. maize) are significant, especially for high pigment leaves. Moreover, chlorophyll retrieved from inversion of the modified model is consequently improved (RMSE from 5.9-13.3 ug/cm2 with mean value 8.1 ug/cm2, while mean correlation coefficient is 0.90) compared to results of PROSPECT-5 (RMSE from 9.6-20.2 ug/cm2 with mean value 13.1 ug/cm2, while mean correlation coefficient is 0.81). Underestimation of high chlorophyll content, which is due to underestimation of reflectance in the visible region of PROSPECT, is partially corrected or alleviated. Improvements are particularly noticeable for leaves with high surface reflectance or high chlorophyll content, which both lead to large proportions of surface reflectance to the total leaf reflectance.

Potential Rapid Effects on Soil Organic Matter Characteristics and Chemistry Following a Change in Dominant Litter Inputs

NASA Astrophysics Data System (ADS)

Crow, S. E.; Filley, T.; Conyers, G.; Stott, D.; McCormick, M.; Whigham, D.; Taylor, D.

2006-12-01

Changes in vegetation structure are expected in forests globally under predicted future climate scenarios. Shifts in type or quantity of litter inputs, which will be associated with changes in plant community, may influence soil organic matter (SOM) characteristics. We altered litter inputs in a mixed-deciduous forest at the Smithsonian Environmental Research Center beginning in May 2004: litter removal, leaf amendment, and wood amendment plots were established in three old (120-150 y) and three young (50-70 y) forests. Plots were amended with wood and leaves collected locally from the dominant tree species, tulip poplar (Lirodendron tulipifera). 0-5 cm A horizon soil was collected in November 2005, 18 months after initial treatment, and physically fractionated first by dispersal in HMP and size separation (53 μm) to remove silts and clays then the >53 μm fraction by density (1.4 g cm-3) in SPT to separate the organic debris (light fraction, LF) from the mineral material. Soil with the greatest amount of C present within the LF came from the wood amendment treatment (35.2 ± 0.1%), followed by the leaf amendment (27.7 ± 0.0%) and the litter removal (24.5 ± 0.0%) treatments. In a pattern opposite of the other treatments, leaf amended soil from the old sites had less C within LF than the young. Potentially, a priming effect from the leaf addition at the old sites resulted in increased decomposition of soil LF. While at the young sites, invasive earthworms potentially provided a rapid, direct mode for incorporation of fresh leaf inputs into LF. Preliminary data indicate differences in lignin and cutin/suberin decay rates during litter decomposition between old and young sites. An investigation into the biopolymer composition of LF will determine whether altering litter inputs will ultimately influence SOM dynamics at both the old and young forest sites.

Analysis of spatial diffusion of ferric ions in PVA-GTA gel dosimeters through magnetic resonance imaging

NASA Astrophysics Data System (ADS)

Marrale, Maurizio; Collura, Giorgio; Gallo, Salvatore; Nici, Stefania; Tranchina, Luigi; Abbate, Boris Federico; Marineo, Sandra; Caracappa, Santo; d'Errico, Francesco

2017-04-01

This work focused on the analysis of the temporal diffusion of ferric ions through PVA-GTA gel dosimeters. PVA-GTA gel samples, partly exposed with 6 MV X-rays in order to create an initial steep gradient, were mapped using magnetic resonance imaging on a 7T MRI scanner for small animals. Multiple images of the gels were acquired over several hours after irradiation and were analyzed to quantitatively extract the signal profile. The spatial resolution achieved is 200 μm and this makes this technique particularly suitable for the analysis of steep gradients of ferric ion concentration. The results obtained with PVA-GTA gels were compared with those achieved with agarose gels, which is a standard dosimetric gel formulation. The analysis showed that the diffusion process is much slower (more than five times) for PVA-GTA gels than for agarose ones. Furthermore, it is noteworthy that the diffusion coefficient value obtained through MRI analysis is significantly consistent with that obtained in separate study Marini et al. (Submitted for publication) using a totally independent method such as spectrophotometry. This is a valuable result highlighting that the good dosimetric features of this gel matrix not only can be reproduced but also can be measured through independent experimental techniques based on different physical principles.

Contrasting cDNA-AFLP profiles between crown and leaf tissues of cold-acclimated wheat plants indicate differing regulatory circuitries for low temperature tolerance.

PubMed

Ganeshan, Seedhabadee; Sharma, Pallavi; Young, Lester; Kumar, Ashwani; Fowler, D Brian; Chibbar, Ravindra N

2011-03-01

Low-temperature (LT) tolerance in winter wheat (Triticum aestivum L.) is an economically important but complex trait. Four selected wheat genotypes, a winter hardy cultivar, Norstar, a tender spring cultivar, Manitou and two near-isogenic lines with Vrn-A1 (spring Norstar) and vrn-A1 (winter Manitou) alleles of Manitou and Norstar were cold-acclimated at 6°C and crown and leaf tissues were collected at 0, 2, 14, 21, 35, 42, 56 and 70 days of cold acclimation. cDNA-AFLP profiling was used to determine temporal expression profiles of transcripts during cold-acclimation in crown and leaf tissues, separately to determine if LT regulatory circuitries in crown and leaf tissues could be delineated using this approach. Screening 64 primer combinations identified 4,074 and 2,757 differentially expressed transcript-derived fragments (TDFs) out of which 38 and 16% were up-regulated as compared to 3 and 6% that were down-regulated in crown and leaf tissues, respectively. DNA sequencing of TDFs revealed sequences common to both tissues including genes coding for DEAD-box RNA helicase, choline-phosphate cytidylyltransferase and delta-1-pyrroline carboxylate synthetase. TDF specific to crown tissues included genes coding for phospahtidylinositol kinase, auxin response factor protein and brassinosteroid insensitive 1-associated receptor kinase. In leaf, genes such as methylene tetrahydrofolate reductase, NADH-cytochrome b5 reductase and malate dehydrogenase were identified. However, 30 and 14% of the DNA sequences from the crown and leaf tissues, respectively, were hypothetical or unknown proteins. Cluster analysis of up-, down-regulated and unique TDFs, DNA sequence and real-time PCR validation, infer that mechanisms operating in crown and leaf tissue in response to LT are differently regulated and warrant further studies.

PHYTOCHEMICAL SCREENING, ANTI-INFLAMMATORY AND ANALGESIC PROPERTIES OF PENTANISIA PRUNELLOIDES FROM THE EASTERN CAPE PROVINCE, SOUTH AFRICA

PubMed Central

Mathews, Miya Gugulethu; Ajayi, Oyemitan Idris; Opeoluwa, Oyedeji Oyehan; Oluwatobi, Oluwafemi Samuel; Benedicta N, Nkeh-Chungag; Phindile, Songca Sandile; Oyedeji; Omowumi, Adebola

2016-01-01

Background: Pentanisia prunelloides is a medicinal plant widely used to remedy various ailments including infections, fever and rheumatism in Eastern Cape Province of South Africa. There is scanty report on the phytochemical and biological properties of the plant; hence various solvent extracts of the dried plant materials were phytochemically screened, and its aqueous extract evaluated for acute toxicity effect, analgesic and antiinflammatory properties in rodents. Methods and Materials: Different extracts of both leaf and rhizome were obtained separately with ethanol, methanol and water. Portions of the filtrate were used for qualitative screening of secondary metabolites and remaining portions were concentrated and dried. Dried grounded leaf and rhizome of the plant were also used for quantitative screening for some major components. The aqueous extract of the leaf and rhizome were used for acute toxicity (LD50) test, antiinflammatory and analgesic activities in rodents. Results: The qualitative phytochemical screening showed the presence of several phytoconstituents with saponins, flavonoids and alkaloids constituting highest constituents in the leaf and rhizome. The LD50: of the aqueous extracts (from leaf or rhizome) was found to be ≥5000 mg/kg orally. The leaf and rhizome aqueous extract (250-500 mg/kg) significantly (p<0.01) reduced egg albumin-induced paw oedema and paw licking in mice induced by formalin, signifying antinociceptive and antiinflammatory activities respectively. Conclusion: It is concluded that the leaf and rhizome of P. prunelloides are rich in various phytochemicals which could be associated with their medicinal uses. The aqueous leaf and rhizome extracts are similarly non-toxic orally, showed antiinflammatory and analgesic potentials thus rationalizing its use in folkloric medicine. PMID:28480377

Remote sensing and the optical properties of the narrow cylindrical leaves of Juncus roemerianus

USGS Publications Warehouse

Ramsey, Elijah W.; Rangoonwala, A.

2004-01-01

To develop a more complete foundation for remote sensing of the marsh grass Juncus roemerianus, we measured the optical properties of its cylindrical leaves at sites of different canopy height, biomass composition and amount, and connectivity to ocean flushing. To measure the leaf optical properties, we adapted a technique used for conifer needles. After establishing the reliability and limits of the adapted technique to the wider J.roemerianus leaves, mean transmittance and reflectance spectra were compared to associated leaf diameters from two dates in 1999 and 2002 and at each site. Transmittance was inversely related to leaf diameter. Mean transmittance and reflectance generated from reoccupation of many field sites in 2002 indicated little or no difference in transmittance between years, a slight reflectance difference in the visible (<2%) and a slightly higher reflectance difference in the near infrared (NIR) (<4%). Site comparison indicated limited ability to separate leaf transmittance but not reflectance by marsh type (e.g., low, medium, high) or biomass. Excluding one outlier, we found leaf transmittances could be adequately represented as 1% ?? 0.2% in the visible and 9% ?? 1% in the NIR and leaf reflectances represented from 14% to 16% in the visible and 71% to 75% in the NIR (the reflectance ranges represent 1999 and 2002 means). Reflectance and transmittance spectra associated with the dead J. roemerianus leaves displayed a spectrally flat increase from the visible to the NIR wavelengths. In total, we documented the atypical optical properties of the cylindrical J. roemerianus leaves and showed that to a first approximation, single means could represent leaf transmittance and visible leaf reflectance across all marsh zones and, after accounting for sample standardization, possibly the NIR reflectance as well.

Terminalia ferdinandiana Exell. Extracts inhibit the growth of body odour-forming bacteria.

PubMed

McManus, K; Wood, A; Wright, M H; Matthews, B; Greene, A C; Cock, I E

2017-10-01

Terminalia ferdinandiana extracts are potent growth inhibitors of many bacterial pathogens. They may also inhibit the growth of malodour-producing bacteria and thus be useful deodorant components, although this is yet to be tested. Terminalia ferdinandiana fruit and leaf solvent extracts were investigated by disc diffusion and liquid dilution MIC assays against the most significant bacterial contributors to axillary and plantar malodour formation. Toxicity was determined using the Artemia franciscana nauplii bioassay. Non-targeted HPLC separation of the methanolic leaf extract coupled to high-resolution time-of-flight (TOF) mass spectroscopy was used for the identification and characterization of individual components in the extract. The T. ferdinandiana leaf extracts were the most potent bacterial growth inhibitors. The leaf methanolic extract was particularly potent, with low MIC values against C. jeikeium (233 μg mL -1 ), S. epidermidis (220 μg mL -1 ), P. acnes (625 μg mL -1 ) and B. linens (523 μg mL -1 ). The aqueous and ethyl acetate leaf extracts were also potent growth inhibitors of C. jeikeium and S. epidermidis (MICs < 1000 μg mL -1 ). In comparison, the fruit extracts were substantially less potent antibacterial agents, although still with MIC values indicative of moderate growth inhibitory activity. All T. ferdinandiana leaf extracts were non-toxic in the Artemia franciscana bioassay. Non-biased phytochemical analysis of the methanolic leaf extract revealed the presence of high levels of and high diversity of tannins and high levels of the flavone luteolin. The low toxicity of the T. ferdinandiana leaf extracts and their potent growth inhibition of axillary and plantar malodour-producing bacteria indicate their potential as deodorant components. © 2017 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

Leaf gas exchange characteristics of three neotropical mangrove species in response to varying hydroperiod

USGS Publications Warehouse

Krauss, Ken W.; Twilley, Robert R.; Doyle, Thomas W.; Gardiner, Emile S.

2006-01-01

We determined how different hydroperiods affected leaf gas exchange characteristics of greenhouse-grown seedlings (2002) and saplings (2003) of the mangrove species Avicennia germinans (L.) Stearn., Laguncularia racemosa (L.) Gaertn. f., and Rhizophora mangle L. Hydroperiod treatments included no flooding (unflooded), intermittent flooding (intermittent), and permanent flooding (flooded). Plants in the intermittent treatment were measured under both flooded and drained states and compared separately. In the greenhouse study, plants of all species maintained different leaf areas in the contrasting hydroperiods during both years. Assimilation–light response curves indicated that the different hydroperiods had little effect on leaf gas exchange characteristics in either seedlings or saplings. However, short-term intermittent flooding for between 6 and 22 days caused a 20% reduction in maximum leaf-level carbon assimilation rate, a 51% lower light requirement to attain 50% of maximum assimilation, and a 38% higher demand from dark respiration. Although interspecific differences were evident for nearly all measured parameters in both years, there was little consistency in ranking of the interspecific responses. Species by hydroperiod interactions were significant only for sapling leaf area. In a field study, R. mangle saplings along the Shark River in the Everglades National Park either demonstrated no significant effect or slight enhancement of carbon assimilation and water-use efficiency while flooded. We obtained little evidence that contrasting hydroperiods affect leaf gas exchange characteristics of mangrove seedlings or saplings over long time intervals; however, intermittent flooding may cause short-term depressions in leaf gas exchange. The resilience of mangrove systems to flooding, as demonstrated in the permanently flooded treatments, will likely promote photosynthetic and morphological adjustment to slight hydroperiod shifts in many settings..

Dosimetric study of GZP6 60 Co high dose rate brachytherapy source.

PubMed

Lei, Qin; Xu, Anjian; Gou, Chengjun; Wen, Yumei; He, Donglin; Wu, Junxiang; Hou, Qing; Wu, Zhangwen

2018-05-28

The purpose of this study was to obtain dosimetric parameters of GZP6 60 Co brachytherapy source number 3. The Geant4 MC code has been used to obtain the dose rate distribution following the American Association of Physicists in Medicine (AAPM) TG-43U1 dosimetric formalism. In the simulation, the source was centered in a 50 cm radius water phantom. The cylindrical ring voxels were 0.1 mm thick for r ≤ 1 cm, 0.5 mm for 1 cm < r ≤ 5 cm, and 1 mm for r > 5 cm. The kerma-dose approximation was performed for r > 0.75 cm to increase the simulation efficiency. Based on the numerical results, the dosimetric datasets were obtained. These results were compared with the available data of the similar 60 Co high dose rate sources and the detailed dosimetric characterization was discussed. © 2018 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

Comparative Transcriptomics Unravel Biochemical Specialization of Leaf Tissues of Stevia for Diterpenoid Production1

PubMed Central

Kim, Mi Jung; Jin, Jingjing; Zheng, Junshi

2015-01-01

Stevia (Stevia rebaudiana) produces not only a group of diterpenoid glycosides known as steviol glycosides (SGs), but also other labdane-type diterpenoids that may be spatially separated from SGs. However, their biosynthetic routes and spatial distribution in leaf tissues have not yet been elucidated. Here, we integrate metabolome and transcriptome analyses of Stevia to explore the biosynthetic capacity of leaf tissues for diterpenoid metabolism. Tissue-specific chemical analyses confirmed that SGs were accumulated in leaf cells but not in trichomes. On the other hand, Stevia leaf trichomes stored other labdane-type diterpenoids such as oxomanoyl oxide and agatholic acid. RNA sequencing analyses from two different tissues of Stevia provided a comprehensive overview of dynamic metabolic activities in trichomes and leaf without trichomes. These metabolite-guided transcriptomics and phylogenetic and gene expression analyses clearly identified specific gene members encoding enzymes involved in the 2-C-methyl-d-erythritol 4-phosphate pathway and the biosynthesis of steviol or other labdane-type diterpenoids. Additionally, our RNA sequencing analysis uncovered copalyl diphosphate synthase (SrCPS) and kaurene synthase1 (SrKS1) homologs, SrCPS2 and KS-like (SrKSL), which were specifically expressed in trichomes. In vitro and in planta assays showed that unlike SrCPS and SrKS1, SrCPS2 synthesized labda-13-en-8-ol diphosphate and successively catalyzed the formation of manoyl oxide and epi-manoyl oxide in combination with SrKSL. Our findings suggest that Stevia may have evolved to use distinct metabolic pathways to avoid metabolic interferences in leaf tissues for efficient production of diverse secondary metabolites. PMID:26438788

On the Relationship Between Hyperspectral Data and Foliar Nitrogen Content in Closed Canopy Forests

NASA Astrophysics Data System (ADS)

Knyazikhin, Y.; Schull, M.; Lepine, L. C.; Stenberg, P.; Mõttus, M.; Rautiainen, M.; Latorre, P.; Myneni, R.; Kaufmann, R.

2011-12-01

The importance of nitrogen for terrestrial ecosystem carbon dynamics and its climate feedback has been well recognized by the ecological community. Interaction between carbon and nitrogen at leaf level is among the fundamental mechanisms that directly control the dynamics of terrestrial vegetation carbon. This process influences absorption and scattering of solar radiation by foliage, which in turn impacts radiation reflected by the vegetation and measured by satellite sensors. NASA's Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) and ground based data on canopy structure and foliage nitrogen concentration acquired over six sites in Maine, New England, Florida, North Carolina and Washington were analyzed to assess the role of canopy structure, leaf optics and its biochemical constituents in the spectral variation of radiation reflected by the forest. The study sites represent closed canopy forests (LAI~5). Our results suggest: 1. Impact of canopy structure is so strong that it can significantly suppress the sensitivity of hyperspectral data to leaf optics. 2. Forest reflectance spectra in the interval [710, 790 nm] are required to obtain the fraction of the total leaf area that a "sensor sees" in a given direction. For closed canopy forests its retrieval does not require canopy reflectance models, suggesting that canopy reflectance spectra in this interval provide a direct estimate of the leaf area fraction. 3. The leaf area fraction fully explains variation in measured reflectance spectra due to variation in canopy structure. This variable is used to estimate the mean leaf scattering over foliage that the "sensor sees." For example the nadir-viewing AVIRIS sensor accumulates foliage optical properties over 25% of the total foliage area in needle leaf forest and about 50% in broadleaf forest. 4. Leaf surface properties have an impact on forest reflectivity, lowering its sensitivity to leaf absorbing pigments. 5. Variation in foliar nitrogen concentration can explain up to 55% of variation in AVIRIS spectra in the interval between 400 and 900 nm. The remaining factors could be due to (a) impact of leaf surface properties and/or (b) under-sampling of leaf optical properties due to the single view of the AVIRIS sensor. The theory of canopy spectral invariants underlies the separation of leaf scattering from the total canopy reflectance spectrum.

Leaf trait dissimilarities between Dutch elm hybrids with a contrasting tolerance to Dutch elm disease

PubMed Central

Ďurkovič, Jaroslav; Čaňová, Ingrid; Lagaňa, Rastislav; Kučerová, Veronika; Moravčík, Michal; Priwitzer, Tibor; Urban, Josef; Dvořák, Miloň; Krajňáková, Jana

2013-01-01

Background and Aims Previous studies have shown that Ophiostoma novo-ulmi, the causative agent of Dutch elm disease (DED), is able to colonize remote areas in infected plants of Ulmus such as the leaf midrib and secondary veins. The objective of this study was to compare the performances in leaf traits between two Dutch elm hybrids ‘Groeneveld’ and ‘Dodoens’ which possess a contrasting tolerance to DED. Trait linkages were also tested with leaf mass per area (LMA) and with the reduced Young's modulus of elasticity (MOE) as a result of structural, developmental or functional linkages. Methods Measurements and comparisons were made of leaf growth traits, primary xylem density components, gas exchange variables and chlorophyll a fluorescence yields between mature plants of ‘Groeneveld’ and ‘Dodoens’ grown under field conditions. A recently developed atomic force microscopy technique, PeakForce quantitative nanomechanical mapping, was used to reveal nanomechanical properties of the cell walls of tracheary elements such as MOE, adhesion and dissipation. Key Results ‘Dodoens’ had significantly higher values for LMA, leaf tissue thickness variables, tracheary element lumen area (A), relative hydraulic conductivity (RC), gas exchange variables and chlorophyll a fluorescence yields. ‘Groeneveld’ had stiffer cell walls of tracheary elements, and higher values for water-use efficiency and leaf water potential. Leaves with a large carbon and nutrient investment in LMA tended to have a greater leaf thickness and a higher net photosynthetic rate, but LMA was independent of RC. Significant linkages were also found between the MOE and some vascular traits such as RC, A and the number of tracheary elements per unit area. Conclusions Strong dissimilarities in leaf trait performances were observed between the examined Dutch elm hybrids. Both hybrids were clearly separated from each other in the multivariate leaf trait space. Leaf growth, vascular and gas exchange traits in the infected plants of ‘Dodoens’ were unaffected by the DED fungus. ‘Dodoens’ proved to be a valuable elm germplasm for further breeding strategies. PMID:23264236

Stomatal clustering in Begonia associates with the kinetics of leaf gaseous exchange and influences water use efficiency.

PubMed

Papanatsiou, Maria; Amtmann, Anna; Blatt, Michael R

2017-04-01

Stomata are microscopic pores formed by specialized cells in the leaf epidermis and permit gaseous exchange between the interior of the leaf and the atmosphere. Stomata in most plants are separated by at least one epidermal pavement cell and, individually, overlay a single substomatal cavity within the leaf. This spacing is thought to enhance stomatal function. Yet, there are several genera naturally exhibiting stomata in clusters and therefore deviating from the one-cell spacing rule with multiple stomata overlaying a single substomatal cavity. We made use of two Begonia species to investigate whether clustering of stomata alters guard cell dynamics and gas exchange under different light and dark treatments. Begonia plebeja, which forms stomatal clusters, exhibited enhanced kinetics of stomatal conductance and CO2 assimilation upon light stimuli that in turn were translated into greater water use efficiency. Our findings emphasize the importance of spacing in stomatal clusters for gaseous exchange and plant performance under environmentally limited conditions. © The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology.

SU-C-BRB-04: Characteristics and Performance Evaluation of the First Commercial MLC for a Robotic Delivery System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fuerweger, C; European Cyberknife Center Munich, Munich, DE; Prins, P

Purpose: To assess characteristics and performance of the “Incise™” MLC (41 leaf pairs, 2.5mm width, FFF linac) mounted on the robotic SRS/SBRT platform “CyberKnife M6™” in a pre-clinical 5 months (11/2014–03/2015) test period. Methods: Beam properties were measured with unshielded diodes and EBT3 film. The CyberKnife workspace for MLC was analyzed by transforming robot node coordinates (cranial / body paths) into Euler geometry. Bayouth tests for leaf / bank position accuracy were performed in standard (A/P) and clinically relevant non-standard positions, before and after exercising the MLC for 10+ minutes. Total system and delivery accuracy were assessed in End-to-End testsmore » and dosimetric verification of exemplary plans. Stability over time was evaluated in Picket-Fence-and adapted Winston-Lutz-tests (AQA) for different collimator angles. Results: Penumbrae (80–20%, with 100%=2*dose at inflection point; SAD 80cm; 10cm depth) parallel / perpendicular to leaf motion were 2.87/2.64mm for the smallest (0×76×0.75cm{sup 2}) and 5.34/4.94mm for the largest (9.76×9.75cm{sup 2}) square field. MLC circular field penumbrae exceeded fixed cones by 10–20% (e.g. 60mm: 4.0 vs. 3.6mm; 20mm: 3.6 vs. 2.9mm). Interleaf leakage was <0.5%. Clinically accessible workspace with MLC covered (non-coplanar) gantry angles of [-113°;+112°] (cranial) and [-108°;+102°] (body), and collimator angles of [-100°;+107°] (cranial) and [-91°;+100°] (body). Average leaf position offsets were ≤0.2mm in 14 standard A/P Bayouth tests and ≤0.6mm in 8 non-standard direction tests. Pre-test MLC exercise increased jaggedness (range ±0.3mm vs. ±0.5mm) and allowed to identify one malfunctioning leaf motor. Total system accuracy with MLC was 0.39±0.06mm in 6 End-to-End tests. Picket-Fence and AQA showed no adverse trends during the test period. Conclusion: The Incise™ MLC for CyberKnife M6™ displayed high accuracy and mechanical stability over the test period. The specific CyberKnife geometry and performance after exercise demand dedicated QA measures. This work is in part funded by a research grant from Accuray Inc, Sunnyvale, USA. Erasmus MC Cancer Institute also has research collaborations with Elekta AB, Stockholm, Sweden. C Fuerweger has previously received speaker honoraria from Accuray Inc, Sunnyvale, USA.« less

Determination of saponins and flavonoids in ivy leaf extracts using HPLC-DAD.

PubMed

Yu, Miao; Shin, Young June; Kim, Nanyoung; Yoo, Guijae; Park, SeonJu; Kim, Seung Hyun

2015-04-01

A new method for the determination of six compounds, chlorogenic acid, rutin, nicotiflorin, hederacoside C, hederasaponin B and α-hederin, in ivy leaf extracts using high-performance liquid chromatography with diode array detector was developed. The chromatographic separation was performed on a YMC Hydrosphere C18 analytical column using a gradient elution of 0.1% phosphoric acid and acetonitrile. The method was validated in terms of specificity, linearity (r(2) > 0.9999), precision [relative standard deviation (RSD) < 0.36%] and accuracy (97.4-103.8%). The limit of detection and limit of quantification were <20.32 and 61.56 ng for all analytes, respectively. The tested compounds were found to be stable in the ivy leaf extract from 0 to 48 h, and the RSD value for each compound was <0.90%. The validated method was successfully applied to quantify all six compounds in a 30% ethanol ivy leaf extract and 13 ivy leaf extract products. The results showed that all the tested products satisfied the minimum requirement for the content of hederacoside C. However, there were some differences between the contents of other constituents. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Leaf gas films delay salt entry and enhance underwater photosynthesis and internal aeration of Melilotus siculus submerged in saline water.

PubMed

Teakle, Natasha Lea; Colmer, Timothy David; Pedersen, Ole

2014-10-01

A combination of flooding and salinity is detrimental to most plants. We studied tolerance of complete submergence in saline water for Melilotus siculus, an annual legume with superhydrophobic leaf surfaces that retain gas films when under water. M. siculus survived complete submergence of 1 week at low salinity (up to 50 mol m(-3) NaCl), but did not recover following de-submergence from 100 mol m(-3) NaCl. The leaf gas films protected against direct salt ingress into the leaves when submerged in saline water, enabling underwater photosynthesis even after 3 d of complete submergence. By contrast, leaves with the gas films experimentally removed suffered from substantial Na(+) and Cl(-) intrusion and lost the capacity for underwater photosynthesis. Similarly, plants in saline water and without gas films lost more K(+) than those with intact gas films. This study has demonstrated that leaf gas films reduce Na(+) and Cl(-) ingress into leaves when submerged by saline water - the thin gas layer physically separates the floodwater from the leaf surface. This feature aids survival of plants exposed to short-term saline submergence, as well as the previously recognized beneficial effects of gas exchange under water. © 2014 John Wiley & Sons Ltd.

A novel geometry-dosimetry label fusion method in multi-atlas segmentation for radiotherapy: a proof-of-concept study

NASA Astrophysics Data System (ADS)

Chang, Jina; Tian, Zhen; Lu, Weiguo; Gu, Xuejun; Chen, Mingli; Jiang, Steve B.

2017-05-01

Multi-atlas segmentation (MAS) has been widely used to automate the delineation of organs at risk (OARs) for radiotherapy. Label fusion is a crucial step in MAS to cope with the segmentation variabilities among multiple atlases. However, most existing label fusion methods do not consider the potential dosimetric impact of the segmentation result. In this proof-of-concept study, we propose a novel geometry-dosimetry label fusion method for MAS-based OAR auto-contouring, which evaluates the segmentation performance in terms of both geometric accuracy and the dosimetric impact of the segmentation accuracy on the resulting treatment plan. Differently from the original selective and iterative method for performance level estimation (SIMPLE), we evaluated and rejected the atlases based on both Dice similarity coefficient and the predicted error of the dosimetric endpoints. The dosimetric error was predicted using our previously developed geometry-dosimetry model. We tested our method in MAS-based rectum auto-contouring on 20 prostate cancer patients. The accuracy in the rectum sub-volume close to the planning tumor volume (PTV), which was found to be a dosimetric sensitive region of the rectum, was greatly improved. The mean absolute distance between the obtained contour and the physician-drawn contour in the rectum sub-volume 2 mm away from PTV was reduced from 3.96 mm to 3.36 mm on average for the 20 patients, with the maximum decrease found to be from 9.22 mm to 3.75 mm. We also compared the dosimetric endpoints predicted for the obtained contours with those predicted for the physician-drawn contours. Our method led to smaller dosimetric endpoint errors than the SIMPLE method in 15 patients, comparable errors in 2 patients, and slightly larger errors in 3 patients. These results indicated the efficacy of our method in terms of considering both geometric accuracy and dosimetric impact during label fusion. Our algorithm can be applied to different tumor sites and radiation treatments, given a specifically trained geometry-dosimetry model.

A novel geometry-dosimetry label fusion method in multi-atlas segmentation for radiotherapy: a proof-of-concept study.

PubMed

Chang, Jina; Tian, Zhen; Lu, Weiguo; Gu, Xuejun; Chen, Mingli; Jiang, Steve B

2017-05-07

Multi-atlas segmentation (MAS) has been widely used to automate the delineation of organs at risk (OARs) for radiotherapy. Label fusion is a crucial step in MAS to cope with the segmentation variabilities among multiple atlases. However, most existing label fusion methods do not consider the potential dosimetric impact of the segmentation result. In this proof-of-concept study, we propose a novel geometry-dosimetry label fusion method for MAS-based OAR auto-contouring, which evaluates the segmentation performance in terms of both geometric accuracy and the dosimetric impact of the segmentation accuracy on the resulting treatment plan. Differently from the original selective and iterative method for performance level estimation (SIMPLE), we evaluated and rejected the atlases based on both Dice similarity coefficient and the predicted error of the dosimetric endpoints. The dosimetric error was predicted using our previously developed geometry-dosimetry model. We tested our method in MAS-based rectum auto-contouring on 20 prostate cancer patients. The accuracy in the rectum sub-volume close to the planning tumor volume (PTV), which was found to be a dosimetric sensitive region of the rectum, was greatly improved. The mean absolute distance between the obtained contour and the physician-drawn contour in the rectum sub-volume 2 mm away from PTV was reduced from 3.96 mm to 3.36 mm on average for the 20 patients, with the maximum decrease found to be from 9.22 mm to 3.75 mm. We also compared the dosimetric endpoints predicted for the obtained contours with those predicted for the physician-drawn contours. Our method led to smaller dosimetric endpoint errors than the SIMPLE method in 15 patients, comparable errors in 2 patients, and slightly larger errors in 3 patients. These results indicated the efficacy of our method in terms of considering both geometric accuracy and dosimetric impact during label fusion. Our algorithm can be applied to different tumor sites and radiation treatments, given a specifically trained geometry-dosimetry model.

What happens in the pith stays in the pith: tissue-localized defense responses facilitate chemical niche differentiation between two spatially separated herbivores.

PubMed

Lee, Gisuk; Joo, Youngsung; Kim, Sang-Gyu; Baldwin, Ian T

2017-11-01

Herbivore attack is known to elicit systemic defense responses that spread throughout the host plant and influence the performance of other herbivores. While these plant-mediated indirect competitive interactions are well described, and the co-existence of herbivores from different feeding guilds is common, the mechanisms of co-existence are poorly understood. In both field and glasshouse experiments with a native tobacco, Nicotiana attenuata, we found no evidence of negative interactions when plants were simultaneously attacked by two spatially separated herbivores: a leaf chewer Manduca sexta and a stem borer Trichobaris mucorea. T. mucorea attack elicited jasmonic acid (JA) and jasmonoyl-l-isoleucine bursts in the pith of attacked stems similar to those that occur in leaves when M. sexta attacks N. attenuata leaves. Pith chlorogenic acid (CGA) levels increased 1000-fold to levels 6-fold higher than leaf levels after T. mucorea attack; these increases in pith CGA levels, which did not occur in M. sexta-attacked leaves, required JA signaling. With plants silenced in CGA biosynthesis (irHQT plants), CGA, as well as other caffeic acid conjugates, was demonstrated in both glasshouse and field experiments to function as a direct defense protecting piths against T. mucorea attack, but not against leaf chewers or sucking insects. T. mucorea attack does not systemically activate JA signaling in leaves, while M. sexta leaf-attack transiently induces detectable but minor pith JA levels that are dwarfed by local responses. We conclude that tissue-localized defense responses allow tissue-specialized herbivores to share the same host and occupy different chemical defense niches in the same hostplant. © 2017 The Authors The Plant Journal © 2017 John Wiley & Sons Ltd.

The content of secondary phenol metabolites in pruned leaves of Aloe arborescens, a comparison between two methods: leaf exudates and leaf water extract.

PubMed

Gutterman, Yitzchak; Chauser-Volfson, Elena

2008-10-01

Aloe arborescens plants, originating from the deserts of South Africa, are grown in the Introduction Garden at Sede Boker in the Negev Desert of Israel. In previous studies, we developed agro-technical methods to raise the content of secondary phenol metabolites (SPhMs) in the Aloe leaves. Plants that are subjected to repeated leaf pruning respond by increasing the content of their SPhMs. The SPhMs found in Aloe arborescens include barbaloin, aloenin and derivatives of aloeresin. Such compounds are used for many purposes, including human skin protection from sun and fire burns and high radiation, as products of the pharmaceutics and cosmetics industries, and as food supplements for treating stomach ulcers and diabetes. In the current study, the SPhMs were separated from pruned leaves of the same A. arborescens plants at the same time by two methods: (1) exudation by squeezing the tissues of the leaves, (2) immersion of the leaves' pruned cut bottom in water and collection of the extract. The exudates and extract were frozen, freeze-dried to a powder and the SPhMs were then separated by chromatography. The yield of powder from water extraction from pruned leaves was much lower than the yield from the exudates. However, higher percentages of the powder from the water extraction contained SPhMs (between 80 and 92.7%). The content of powder in leaf exudates from pruned leaves was much higher because the SPhMs were squeezed out from the cells and tissues. However, the percentages of SPhMs in this powder were much lower (between 39 and 62%).

Poster — Thur Eve — 19: Performance assessment of a 160-leaf beam collimation system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ali, E. S. M.; La Russa, D. J.; Vandervoort, E.

2014-08-15

In this study, the performance of the new beam collimation system with 160 leaves, each with a 5 mm leaf width projected at isocenter, is evaluated in terms of positional accuracy and plan/delivery quality. Positional accuracy was evaluated using a set of static and dynamic MLC/jaw delivery patterns at different gantry angles, dose rates, and MLC/jaw speeds. The impact on IMRT plan quality was assessed by comparing against a previous generation collimation system using the same optimization parameters, while delivery quality was quantified using a combination of patient-specific QA measurements with ion chambers, film, and a bi-planar diode array. Positionalmore » accuracy for four separate units was comparable. The field size accuracy, junction width, and total displacement over 16 cm leaf travel are 0.3 ± 0.2 mm, 0.4 ± 0.3 mm, and 0.5 ± 0.2 mm, respectively. The typical leaf minor offset is 0.05 ± 0.04 mm, and MLC hysteresis effects are 0.2 ± 0.1 mm over 16 cm travel. The dynamic output is linear with MU and MLC/jaw speed, and is within 0.7 ± 0.3 % of the planning system value. Plan quality is significantly improved both in terms of target coverage and OAR sparing due, in part, to the larger allowable MLC and jaw speeds. γ-index pass rates for the patient-specific QA measurements exceeded 97% using criteria of 2%/2 mm. In conclusion, the performance of the Agility system is consistent among four separate installations, and is superior to its previous generations of collimation systems.« less

SU-E-T-424: Dosimetric Verification of Modulated Electron Radiation Therapy Delivered Using An Electron Specific Multileaf Collimator for Treatment of Scalp Cases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eldib, A; Al-Azhar University Cairo; Jin, L

2014-06-01

Purpose: Modulated electron radiotherapy (MERT) has the potential to achieve better treatment outcome for shallow tumors such as those of breast and scalp. In a separate study with scalp lesions, MERT was compared to volumetric modulated arc therapy. Our results showed a reduction in the dose reaching the brain with MERT. However dose calculation accuracy and delivery efficiency challenges remain. Thus in the current study we proceed to add more cases to demonstrate MERT beneficial outcome and its delivery accuracy using an electron specific multileaf collimator (eMLC). Methods: We have used the MCBEAM code for treatment head simulation and formore » generating phase space files to be used as radiation source input for our Monte Carlo based treatment planning system (MC TPS). MCPLAN code is used for calculation of patient specific dose deposition coefficient and for final MERT plan dose calculation. An in-house developed optimization code is used for the optimization process. MERT plans were generated for real patients and head and neck phantom. Film was used for dosimetric verification. The film was cut following the contour of the curved phantom surface and then sealed with black masking tape. In the measurement, the sealed film packet was sandwiched between two adjacent slabs of the head and neck phantom. The measured 2D dose distribution was then compared with calculations. Results: The eMLC allows effective treatment of scalps with multi-lesions spreading around the patient head, which was usually difficult to plan or very time consuming with conventional applicators. MERT continues to show better reduction in the brain dose. The dosimetric measurements showed slight discrepancy, which was attributed to the film setup. Conclusion: MERT can improve treatment plan quality for patients with scalp cancers. Our in-house MC TPS is capable of performing treatment planning and accurate dose calculation for MERT using the eMLC.« less

Differences in Radiation Dosimetry and Anorectal Function Testing Imply That Anorectal Symptoms May Arise From Different Anatomic Substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smeenk, Robert Jan, E-mail: r.smeenk@rther.umcn.nl; Hopman, Wim P.M.; Hoffmann, Aswin L.

2012-01-01

Purpose: To explore the influence of functional changes and dosimetric parameters on specific incontinence-related anorectal complaints after prostate external beam radiotherapy and to estimate dose-effect relations for the anal wall and rectal wall. Methods and Materials: Sixty patients, irradiated for localized prostate cancer, underwent anorectal manometry and barostat measurements to evaluate anal pressures, rectal capacity, and rectal sensory functions. In addition, 30 untreated men were analyzed as a control group. In 36 irradiated patients, the anal wall and rectal wall were retrospectively delineated on planning computed tomography scans, and dosimetric parameters were retrieved from the treatment plans. Functional and dosimetricmore » parameters were compared between patients with and without complaints, focusing on urgency, incontinence, and frequency. Results: After external beam radiotherapy, reduced anal pressures and tolerated rectal volumes were observed, irrespective of complaints. Patients with urgency and/or incontinence showed significantly lower anal resting pressures (mean 38 and 39 vs. 49 and 50 mm Hg) and lower tolerated rectal pressures (mean 28 and 28 vs. 33 and 34 mm Hg), compared to patients without these complaints. In patients with frequency, almost all rectal parameters were reduced. Several dosimetric parameters to the anal wall and rectal wall were predictive for urgency (e.g., anal D{sub mean}>38Gy), whereas some anal wall parameters correlated to incontinence and no dose-effect relation for frequency was found. Conclusions: Anorectal function deteriorates after external beam radiotherapy. Different incontinence-related complaints show specific anorectal dysfunctions, suggesting different anatomic and pathophysiologic substrates: urgency and incontinence seem to originate from both anal wall and rectal wall, whereas frequency seems associated with rectal wall dysfunction. Also, dose-effect relations differed between these complaints. This implies that anal wall and rectal wall should be considered separate organs in radiotherapy planning.« less

SU-E-T-176: Clinical Experience of Brass Mesh Bolus: Patient-Specific Parameters as Predictors of Measured Dosimetric Effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yock, A; Manger, R; Einck, J

2015-06-15

Purpose: Increasingly, brass mesh bolus is used to insure dosimetric coverage of the skin for patients treated post-mastectomy for breast cancer. Contribution of photoelectrons from interactions between the bolus and the primary beam increases dose superficially without affecting dose at greater depths. We present our experience using brass mesh bolus – including patients for whom the bolus was dosimetrically inadequate – along with analysis of relevant patient-specific parameters. Methods: Optically-stimulated luminescent dosimeters (OSLDs) were used to determine the effect of the bolus for 15 patients. They were positioned beneath the bolus within the tangent fields at three positions: 1.5–3cm insidemore » the medial and lateral field edges, and midway between the two. All OSLDs were midfield in the cranial-caudal direction. The measurements were compared with patient-specific parameters including separation, chest wall/breast tissue thickness, beam angle incidence, and planned surface dose. Results: The average OSLD measurement at the medial field edge, midfield, and lateral field edge position was 86.8%, 101.8%, and 92.8% of the prescription dose, respectively. A measurement for one patient was low enough (77.0%) to warrant a switch to an alternative type of bolus. Anatomic parameters were analyzed to investigate the low dose in this case, not observed in the planning system. The patient was observed to have a thin chest wall and very oblique beam angles. A second patient was also switched to an alternative type of bolus due to her being high risk and treated with an electron patch that extended onto the breast. Conclusion: Brass mesh bolus increases dose superficially while leaving dose at greater depths unaffected. However, our results suggest that this effect may be insufficient in patients with a thin chest wall or very oblique beam angles. More data and analysis is necessary to proactively identify patients for whom brass mesh bolus is effective.« less

Determining density of maize canopy. 3: Temporal considerations

NASA Technical Reports Server (NTRS)

Stoner, E. R.; Baumgardner, M. F.; Anuta, P. E.; Cipra, J. E.

1972-01-01

Multispectral scanner data were collected in two flights over ground cover plots at an altitude of 305 m. Eight ground reflectance panels in close proximity to the ground cover plots were used to normalize the scanner data obtained on different dates. Separate prediction equations were obtained for both flight dates for all eleven reflective wavelength bands of the multispectral scanner. Ratios of normalized scanner data were related to leaf area index over time. Normalized scanner data were used to plot relative reflectance versus wavelength for the ground cover plots. Spectral response curves were similar to those for bare soil and green vegetation as determined by laboratory measurements. The spectral response curves from the normalized scanner data indicated that reflectance in the 0.72 to 1.3 micron wavelength range increased as leaf area index increased. A decrease in reflectance was observed in the 0.65 micron chlorophyll absorption band as leaf area index increased.

Intercepted photosynthetically active radiation in wheat canopies estimated by spectral reflectance. [Phoenix, Arizona

NASA Technical Reports Server (NTRS)

Hatfield, J. L.; Asrar, G.; Kanemasu, E. T.

1982-01-01

The interception of photosynthetically active radiation (PAR) was evaluated relative to greenness and normalized difference (MSS 7-5/7+5) for five planting dates of wheat for 1978-79 and 1979-80 in Phoenix. Intercepted PAR was calculated from a model driven by leaf area index and stage of growth. Linear relationships were found between greenness and normalized difference with a separate model representing growth and senescence of the crop. Normalized difference was a significantly better model and would be easier to apply than the empirically derived greenness parameter. For the leaf area growth portion of the season the model between PAR interception and normalized difference was the same over years, however, for the leaf senescence the models showed more variability due to the lack of data on measured interception in sparse canopies. Normalized difference could be used to estimate PAR interception directly for crop growth models.

A Dosimetric Evaluation of The Eclipse and Pinnacle Treatment Planning Systems in Treatment of Vertebral Bodies Using IMRT and VMAT with Modeled and Commissioned Flattening Filter Free (FFF) Fields

NASA Astrophysics Data System (ADS)

Ajo, Ramzi, Jr.

Modern treatment planning systems (TPS's) utilize different algorithms in computing dose within the patient medium. The algorithms rely on properly modeled clinical setups in order to perform optimally. Aside from various parameters of the beam, modifiers, such as multileaf collimators (MLC's), must also be modeled properly. That could not be more true today, where dynamic delivery such as intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) are being increasingly utilized due to their ability to deliver higher dose precisely to the target while sparing more surrounding normal tissue. Two of the most popular TPS's, Pinnacle (Philips) and Eclipse (Varian), were compared, with special emphasis placed on parameterization of the dosimetric leaf gap (DLG) in Eclipse. The DLG is a parameter that accounts for Varian's rounded MLC leaf ends. While Pinnacle accounts for the rounded leaf end by modeling the MLC's, Eclipse uses a measured parameter. This study investigated whether a single value measured DLG is sufficient for dynamic delivery. Using five planning volumes for vertebral body SBRT treatments, each prescribed for 3000 cGy in 5 fractions, an array of 20 treatment plans was generated using varying energies of 6MV-FFF and 10MV-FFF. Treatment techniques consisted of 9-field Step-and-shoot IMRT, and dual-arc VMAT using patient specific optimization criteria in the Pinnacle TPS v9.8. Each plan was normalized to ensure coverage of 3000cGy to 95% of the target volume. The dose was computed in Pinnacle v9.8, with the Collapsed Cone Convolution Superposition algorithm and Eclipse v11, with the Acuros XB algorithm, using a dose grid resolution of 2 mm in both systems. Dose volume histograms (DVH's) were generated for a comparison of max and mean dose to the targets and spinal cord, as well as 95% coverage of the targets and the volume of the spinal cord receiving 14.5 Gy (V14.5). Patient specific quality assurance (PSQA) fields were generated and then delivered, using a Varian Edge linear accelerator, to a 4D QA phantom for a gamma analysis and distance to agreement (DTA) comparison. All Eclipse calculations were made for both measured and optimized DLG parameters. Calculated vs. measured point dose for the Pinnacle TPS had an average difference of 2.79 +/- 2.00%. Gamma analysis using a 3% and 3 mm DTA had 99/100 fields passing at > 95%. Using measured values of the DLG in Eclipse, calculated vs. measured point dose was -4.44 +/- 1.97%, and DTA had 33/110 fields passing at > 95%. After an optimization of the DLG in Eclipse, calculated vs. measured point dose had an average difference of 2.20 +/- 2.23%, and DTA with 95/110 fields passing at > 95%. This study looked at the performance of the Pinnacle and Eclipse TPS's, with special consideration given to the DLG parameterization used by Eclipse. The results support the idea that a single valued DLG is not sufficient for dynamic delivery. An optimization of the parameter is necessary to account for the high modulation of IMRT and VMAT techniques.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huh, S; Lee, S; Dagan, R

Purpose: To investigate the feasibility of utilizing Dynamic Arc (DA) and IMRT with 5mm MLC leaf of VERO treatment unit for SRS/FSRT brain cancer patients with non-invasive stereotactic treatments. The DA and IMRT plans using the VERO unit (BrainLab Inc, USA) are compared with cone-based planning and proton plans to evaluate their dosimetric advantages. Methods: The Vero treatment has unique features like no rotational or translational movements of the table during treatments, Dynamic Arc/IMRT, tracking of IR markers, limitation of Ring rotation. Accuracies of the image fusions using CBCT, orthogonal x-rays, and CT are evaluated less than ∼ 0.7mm withmore » a custom-made target phantom with 18 hidden targets. 1mm margin is given to GTV to determine PTV for planning constraints considering all the uncertainties of planning computer and mechanical uncertainties of the treatment unit. Also, double-scattering proton plans with 6F to 9F beams and typical clinical parameters, multiple isocenter plans with 6 to 21 isocenters, and DA/IMRT plans are evaluated to investigate the dosimetric advantages of the DA/IMRT for complex shape of targets. Results: 3 Groups of the patients are divided: (1) Group A (complex target shape), CI's are same for IMRT, and DGI of the proton plan are better by 9.5% than that of the IMRT, (2) Group B, CI of the DA plans (1.91+/−0.4) are better than cone-based plan, while DGI of the DA plan is 4.60+/−1.1 is better than cone-based plan (5.32+/−1.4), (3) Group C (small spherical targets), CI of the DA and cone-based plans are almost the same. Conclusion: For small spherical targets, cone-based plans are superior to other 2 plans: DS proton and DA plans. For complex or irregular plans, dynamic and IMRT plans are comparable to cone-based and proton plans for complex targets.« less

Dosimetric advantages of generalised equivalent uniform dose-based optimisation on dose–volume objectives in intensity-modulated radiotherapy planning for bilateral breast cancer

PubMed Central

Lee, T-F; Ting, H-M; Chao, P-J; Wang, H-Y; Shieh, C-S; Horng, M-F; Wu, J-M; Yeh, S-A; Cho, M-Y; Huang, E-Y; Huang, Y-J; Chen, H-C; Fang, F-M

2012-01-01

Objective We compared and evaluated the differences between two models for treating bilateral breast cancer (BBC): (i) dose–volume-based intensity-modulated radiation treatment (DV plan), and (ii) dose–volume-based intensity-modulated radiotherapy with generalised equivalent uniform dose-based optimisation (DV-gEUD plan). Methods The quality and performance of the DV plan and DV-gEUD plan using the Pinnacle3® system (Philips, Fitchburg, WI) were evaluated and compared in 10 patients with stage T2–T4 BBC. The plans were delivered on a Varian 21EX linear accelerator (Varian Medical Systems, Milpitas, CA) equipped with a Millennium 120 leaf multileaf collimator (Varian Medical Systems). The parameters analysed included the conformity index, homogeneity index, tumour control probability of the planning target volume (PTV), the volumes V20 Gy and V30 Gy of the organs at risk (OAR, including the heart and lungs), mean dose and the normal tissue complication probability. Results Both plans met the requirements for the coverage of PTV with similar conformity and homogeneity indices. However, the DV-gEUD plan had the advantage of dose sparing for OAR: the mean doses of the heart and lungs, lung V20 Gy, and heart V30 Gy in the DV-gEUD plan were lower than those in the DV plan (p<0.05). Conclusions A better result can be obtained by starting with a DV-generated plan and then improving it by adding gEUD-based improvements to reduce the number of iterations and to improve the optimum dose distribution. Advances to knowledge The DV-gEUD plan provided superior dosimetric results for treating BBC in terms of PTV coverage and OAR sparing than the DV plan, without sacrificing the homogeneity of dose distribution in the PTV. PMID:23091290

SU-F-T-437: 3 Field VMAT Technique for Irradiation of Large Pelvic Tumors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stakhursky, V

2016-06-15

Purpose: VMAT treatment planning for large pelvic volume irradiation could be suboptimal due to inability of Varian linac to split MLC carriage during VMAT delivery for fields larger than 14.5cm in X direction (direction of leaf motion). We compare the dosimetry between 3 VMAT planning techniques, two 2-arc field techniques and a 3-arc field technique: a) two small in X direction (less than 14.5cm) arc fields, complementing each other to cover the whole lateral extent of target during gantry rotation, b) two large arc fields, each covering the targets completely during the rotation, c) a 3 field technique with 2more » small in X direction arcs and 1 large field covering whole target. Methods: 5 GYN cancer patients were selected to evaluate the 3 VMAT planning techniques. Treatment plans were generated using Varian Eclipse (ver. 11) TPS. Dose painting technique was used to deliver 5300 cGy to primary target and 4500 cGy to pelvic/abdominal node target. All the plans were normalized so that the prescription dose of 5300 cGy covered 95% of primary target volume. PTV and critical structures DVH curves were compared to evaluate all 3 planning techniques. Results: The dosimetric differences between the two 2-arc techniques were minor. The small field 2-arc technique showed a colder hot spot (0.4% averaged), while variations in maximum doses to critical structures were statistically nonsignificant (under 1.3%). In comparison, the 3-field technique demonstrated a colder hot spot (1.1% less, 105.8% averaged), and better sparing of critical structures. The maximum doses to larger bowel, small bowel and gluteal fold were 3% less, cord/cauda sparing was 4.2% better, and bladder maximum dose was 4.6% less. The differences in maximum doses to stomach and rectum were statistically nonsignificant. Conclusion: 3-arc VMAT technique for large field irradiation of pelvis demonstrates dosimetric advantages compared to 2-arc VMAT techniques.« less

SESAME: a software tool for the numerical dosimetric reconstruction of radiological accidents involving external sources and its application to the accident in Chile in December 2005.

PubMed

Huet, C; Lemosquet, A; Clairand, I; Rioual, J B; Franck, D; de Carlan, L; Aubineau-Lanièce, I; Bottollier-Depois, J F

2009-01-01

Estimating the dose distribution in a victim's body is a relevant indicator in assessing biological damage from exposure in the event of a radiological accident caused by an external source. This dose distribution can be assessed by physical dosimetric reconstruction methods. Physical dosimetric reconstruction can be achieved using experimental or numerical techniques. This article presents the laboratory-developed SESAME--Simulation of External Source Accident with MEdical images--tool specific to dosimetric reconstruction of radiological accidents through numerical simulations which combine voxel geometry and the radiation-material interaction MCNP(X) Monte Carlo computer code. The experimental validation of the tool using a photon field and its application to a radiological accident in Chile in December 2005 are also described.

Dosimetric effects of patient rotational setup errors on prostate IMRT treatments

NASA Astrophysics Data System (ADS)

Fu, Weihua; Yang, Yong; Li, Xiang; Heron, Dwight E.; Saiful Huq, M.; Yue, Ning J.

2006-10-01

The purpose of this work is to determine dose delivery errors that could result from systematic rotational setup errors (ΔΦ) for prostate cancer patients treated with three-phase sequential boost IMRT. In order to implement this, different rotational setup errors around three Cartesian axes were simulated for five prostate patients and dosimetric indices, such as dose-volume histogram (DVH), tumour control probability (TCP), normal tissue complication probability (NTCP) and equivalent uniform dose (EUD), were employed to evaluate the corresponding dosimetric influences. Rotational setup errors were simulated by adjusting the gantry, collimator and horizontal couch angles of treatment beams and the dosimetric effects were evaluated by recomputing the dose distributions in the treatment planning system. Our results indicated that, for prostate cancer treatment with the three-phase sequential boost IMRT technique, the rotational setup errors do not have significant dosimetric impacts on the cumulative plan. Even in the worst-case scenario with ΔΦ = 3°, the prostate EUD varied within 1.5% and TCP decreased about 1%. For seminal vesicle, slightly larger influences were observed. However, EUD and TCP changes were still within 2%. The influence on sensitive structures, such as rectum and bladder, is also negligible. This study demonstrates that the rotational setup error degrades the dosimetric coverage of target volume in prostate cancer treatment to a certain degree. However, the degradation was not significant for the three-phase sequential boost prostate IMRT technique and for the margin sizes used in our institution.

Plant genotypes affect aboveground and belowground herbivore interactions by changing chemical defense.

PubMed

Li, Xiaoqiong; Guo, Wenfeng; Siemann, Evan; Wen, Yuanguang; Huang, Wei; Ding, Jianqing

2016-12-01

Spatially separated aboveground (AG) and belowground (BG) herbivores are closely linked through shared host plants, and both patterns of AG-BG interactions and plant responses may vary among plant genotypes. We subjected invasive (USA) and native (China) genotypes of tallow tree (Triadica sebifera) to herbivory by the AG specialist leaf-rolling weevil Heterapoderopsis bicallosicollis and/or the root-feeding larvae of flea beetle Bikasha collaris. We measured leaf damage and leaves rolled by weevils, quantified beetle survival, and analyzed flavonoid and tannin concentrations in leaves and roots. AG and BG herbivores formed negative feedbacks on both native and invasive genotypes. Leaf damage by weevils and the number of beetle larvae emerging as adults were higher on invasive genotypes. Beetles reduced weevil damage and weevils reduced beetle larval emergence more strongly for invasive genotypes. Invasive genotypes had lower leaf and root tannins than native genotypes. BG beetles decreased leaf tannins of native genotypes but increased root tannins of invasive genotypes. AG herbivory increased root flavonoids of invasive genotypes while BG herbivory decreased leaf flavonoids. Invasive genotypes had lower AG and BG herbivore resistance, and negative AG-BG herbivore feedbacks were much stronger for invasive genotypes. Lower tannin concentrations explained overall better AG and BG herbivore performances on invasive genotypes. However, changes in tannins and flavonoids affected AG and BG herbivores differently. These results suggest that divergent selection on chemical production in invasive plants may be critical in regulating herbivore performances and novel AG and BG herbivore communities in new environments.

Organ-specific proteomics analysis for identification of response mechanism in soybean seedlings under flooding stress.

PubMed

Khatoon, Amana; Rehman, Shafiq; Hiraga, Susumu; Makino, Takahiro; Komatsu, Setsuko

2012-10-22

Flooding is one of the severe environmental factors which impair growth and yield in soybean plant. To investigate the organ specific response mechanism of soybean under flooding stress, changes in protein species were analyzed using a proteomics approach. Two-day-old soybeans were subjected to flooding for 5 days. Proteins were extracted from root, hypocotyl and leaf, and separated by two-dimensional polyacrylamide gel electrophoresis. In root, hypocotyl and leaf, 51, 66 and 51 protein species were significantly changed, respectively, under flooding stress. In root, metabolism related proteins were increased; however these proteins were decreased in hypocotyl and leaf. In all 3 organs, cytoplasm localized proteins were decreased, and leaf chloroplastic proteins were also decreased. Isoflavone reductase was commonly decreased at protein level in all 3 organs; however, mRNA of isoflavone reductase gene was up-regulated in leaf under flooding stress. Biophoton emission was increased in all 3 organs under flooding stress. The up-regulation of isoflavone reductase gene at transcript level; while decreased abundance at protein level indicated that flooding stress affected the mRNA translation to proteins. These results suggest that concurrence in expression of isoflavone reductase gene at mRNA and protein level along with imbalance in other disease/defense and metabolism related proteins might lead to impaired growth of root, hypocotyl and leaf of soybean seedlings under flooding stress. Copyright © 2012 Elsevier B.V. All rights reserved.

Environmental and genetic variation in leaf anatomy among populations of Andropogon gerardii (Poaceae) along a precipitation gradient.

PubMed

Olsen, Jacob T; Caudle, Keri L; Johnson, Loretta C; Baer, Sara G; Maricle, Brian R

2013-10-01

Phenotypes of two Andropogon gerardii subspecies, big bluestem and sand bluestem, vary throughout the prairie ecosystem of North America. This study sought to determine the role of genetics and environment in driving adaptive variation of leaf structure in big bluestem and sand bluestem. • Four populations of big bluestem and one population of sand bluestem were planted in common gardens at four sites across a precipitation gradient from western Kansas to southern Illinois. Internal leaf structure and trichome density of A. gerardii were examined by light microscopy to separate genetic and environmentally controlled traits. Leaf thickness, midrib thickness, bulliform cells, interveinal distance, vein size, and trichome density were quantified. • At all planting sites, sand bluestem and the xeric population of A. gerardii had thicker leaves and fewer bulliform cells compared with mesic populations. Environment and genetic source population were both influential for leaf anatomy. Leaves from plants grown in mesic sites (Carbondale, Illinois and Manhattan, Kansas) had thicker midribs, larger veins, fewer trichomes, and a greater proportion of bulliform cells compared to plants grown in drier sites (Colby and Hays, Kansas). • Water availability has driven adaptive variation in leaf structure in populations of A. gerardii, particularly between sand bluestem and big bluestem. Genetically based differences in leaves of A. gerardii indicate adaptive variation and evolutionary forces differentiating sand bluestem from big bluestem. Environmental responses of A. gerardii leaves suggest an ability to adjust to drought, even in populations adapted to mesic home environments.

Dosimetric performance of the new high-definition multileaf collimator for intracranial stereotactic radiosurgery.

PubMed

Dhabaan, Anees; Elder, Eric; Schreibmann, Eduard; Crocker, Ian; Curran, Walter J; Oyesiku, Nelson M; Shu, Hui-Kuo; Fox, Tim

2010-06-21

The objective was to evaluate the performance of a high-definition multileaf collimator (MLC) of 2.5 mm leaf width (MLC2.5) and compare to standard 5 mm leaf width MLC (MLC5) for the treatment of intracranial lesions using dynamic conformal arcs (DCA) technique with a dedicated radiosurgery linear accelerator. Simulated cases of spherical targets were created to study solely the effect of target volume size on the performance of the two MLC systems independent of target shape complexity. In addition, 43 patients previously treated for intracranial lesions in our institution were retrospectively planned using DCA technique with MLC2.5 and MLC5 systems. The gross tumor volume ranged from 0.07 to 40.57 cm3 with an average volume of 5.9 cm3. All treatment parameters were kept the same for both MLC-based plans. The plan evaluation was performed using figures of merits (FOM) for a rapid and objective assessment on the quality of the two treatment plans for MLC2.5 and MLC5. The prescription isodose surface was selected as the greatest isodose surface covering >or= 95% of the target volume and delivering 95% of the prescription dose to 99% of target volume. A Conformity Index (CI) and conformity distance index (CDI) were used to quantifying the dose conformity to a target volume. To assess normal tissue sparing, a normal tissue difference (NTD) was defined as the difference between the volume of normal tissue receiving a certain dose utilizing MLC5 and the volume receiving the same dose using MLC2.5. The CI and normal tissue sparing for the simulated spherical targets were better with the MLC2.5 as compared to MLC5. For the clinical patients, the CI and CDI results indicated that the MLC2.5 provides better treatment conformity than MLC5 even at large target volumes. The CI's range was 1.15 to 2.44 with a median of 1.59 for MLC2.5 compared to 1.60-2.85 with a median of 1.71 for MLC5. Improved normal tissue sparing was also observed for MLC2.5 over MLC5, with the NTD always positive, indicating improvement, and ranging from 0.1 to 8.3 for normal tissue receiving 50% (NTV50), 70% (NTV70) and 90% (NTV90) of the prescription dose. The MLC2.5 has a dosimetric advantage over the MLC5 in Linac-based radiosurgery using DCA method for intracranial lesions, both in treatment conformity and normal tissue sparing when target shape complexity increases.

Juniperus phoenicea var. turbinata (Guss.) Parl. Leaf Essential Oil Variability in the Balkans.

PubMed

Rajčević, Nemanja F; Labus, Marina G; Dodoš, Tanja Z; Novaković, Jelica J; Marin, Petar D

2018-06-15

In the present work leaf essential oil from 97 individuals of Juniperus phoenicea var. turbinata (GUSS.) PARL. from the Balkan Peninsula was analysed. The essential oil was dominated by monoterpene hydrocarbons (45.5 - 71.8%), of which α-pinene was the most abundant in almost all of the samples (38.2 - 55.8%). Several other monoterpenes and sesquiterpenes were also present in relatively high abundances in samples such as myrcene, δ-3-carene, ß-phellandrene, α-terpinyl acetate, (E)-caryophyllene and germacrene D. Multivariate statistical analysis suggested the existence of three possible chemotypes based on the abundance of the four components. Even though the intrapopulation variability was high, discriminant analysis (DA) was able to separate populations. DA showed high separation between western and eastern populations but also grouped geographically closer populations along the west Balkan shoreline. The potential influence of the climate on the composition of the essential oil was also studied. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

SU-E-J-57: First Development of Adapting to Intrafraction Relative Motion Between Prostate and Pelvic Lymph Nodes Targets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ge, Y; Colvill, E; O’Brien, R

2015-06-15

Purpose Large intrafraction relative motion of multiple targets is common in advanced head and neck, lung, abdominal, gynaecological and urological cancer, jeopardizing the treatment outcomes. The objective of this study is to develop a real-time adaptation strategy, for the first time, to accurately correct for the relative motion of multiple targets by reshaping the treatment field using the multi-leaf collimator (MLC). Methods The principle of tracking the simultaneously treated but differentially moving tumor targets is to determine the new aperture shape that conforms to the shifted targets. Three dimensional volumes representing the individual targets are projected to the beam’s eyemore » view. The leaf openings falling inside each 2D projection will be shifted according to the measured motion of each target to form the new aperture shape. Based on the updated beam shape, new leaf positions will be determined with optimized trade-off between the target underdose and healthy tissue overdose, and considerations of the physical constraints of the MLC. Taking a prostate cancer patient with pelvic lymph node involvement as an example, a preliminary dosimetric study was conducted to demonstrate the potential treatment improvement compared to the state-of- art adaptation technique which shifts the whole beam to track only one target. Results The world-first intrafraction adaptation system capable of reshaping the beam to correct for the relative motion of multiple targets has been developed. The dose in the static nodes and small bowel are closer to the planned distribution and the V45 of small bowel is decreased from 110cc to 75cc, corresponding to a 30% reduction by this technique compared to the state-of-art adaptation technique. Conclusion The developed adaptation system to correct for intrafraction relative motion of multiple targets will guarantee the tumour coverage and thus enable PTV margin reduction to minimize the high target dose to the adjacent organs-at-risk. The authors acknowledge funding support from the Australian NHMRC Australia Fellowship and NHMRC Project Grant No. APP1042375.« less

SU-F-T-629: Effect of Multi-Leaf Collimator (MLC) Width On Plan Quality of Single-Isocenter VMAT Intracranial Stereotactic Radiosurgery for Multiple Metastases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kraus, J; Thomas, E; Wu, X

2016-06-15

Purpose: Single-isocenter VMAT has been shown able to create high quality plans for complex intracranial multiple metastasis SRS cases. Linacs capable of the technique are typically outfitted with an MLC that consists of a combination of 5 mm and 10 mm leaves (standard) or 2.5 mm and 5 mm leaves (high-definition). In this study, we test the hypothesis that thinner collimator leaves are associated with improved plan quality. Methods: Ten multiple metastasis cases were identified and planned for VMAT SRS using a 10 MV flattening filter free beam. Plans were created for a standard (std) and a high-definition (HD) MLC.more » Published values for leaf transmission factor and dosimetric leaf gap were utilized. All other parameters were invariant. Conformity (plan and individual target), moderate isodose spill (V50%), and low isodose spill (mean brain dose) were selected for analysis. Results: Compared to standard MLC, HD-MLC improved overall plan conformity (median: Paddick CI-HD = 0.83, Paddick CI-std = 0.79; p = 0.004 and median: RTOG CI-HD =1.18, RTOG CI-std =1.24; p = 0.01 ), improved individual lesion conformity (median: Paddick CI-HD,i =0.77, Paddick CI-std,i =0.72; p < 0.001 and median: RTOG CI-HD,i = 1.28, RTOG CI-std,i =1.35; p < 0.001), improved moderate isodose spill (median: V50%-HD = 37.0 cc, V50%-std = 45.7 cc; p = 0.002), and improved low dose spill (median: dmean-HD = 2.90 Gy, dmean-std = 3.19 Gy; p = 0.002). Conclusion: For the single-isocenter VMAT SRS of multiple metastasis plans examined, use of HD-MLC modestly improved conformity, moderate isodose, and low isodose spill compared to standard MLC. However, in all cases we were able to generate clinically acceptable plans with the standard MLC. More work is need to further quantify the difference in cases with higher numbers of small targets and to better understand any potential clinical significance. This research was supported in part by Varian Medical Systems.« less

Egg-hatching synchrony and larval cannibalism in the dock leaf beetle Gastrophysa viridula (Coleoptera: Chrysomelidae).

PubMed

Kutcherov, Dmitry

2015-12-01

Females of leaf beetles and many other herbivorous insects lay eggs in coherent batches. Hatchlings emerge more or less simultaneously and often prey on their late-hatching clutchmates. It is not certain, however, whether this synchrony of hatching is a mere by-product of cannibalism or whether an additional synchronizing factor exists. The following simple experiment was aimed at determining the causal relationship between cannibalism and simultaneous larval emergence. Egg clutches of the dock leaf beetle Gastrophysa viridula were split into two halves. These halves were either kept as coherent groups in two separate dishes or, alternatively, only one half remained whole, whereas the other one was divided into single eggs, each of which was incubated in a separate dish. Halving of a clutch into coherent groups only slightly disrupted the synchrony of emergence. The consequence of individual isolation was more dramatic. Half-clutches consisting of disconnected solitary eggs required almost twice as much time for complete emergence of all larvae, which was significantly more than cannibalism as a sole synchronizing factor might explain. Moreover, survival rates were the same in coherent half-clutches (in the presence of cannibalism) and among isolated individuals. This group effect and the small contribution of cannibalism suggest the existence of an additional synchronizing factor. Possible mechanisms underpinning this phenomenon are discussed. Copyright © 2015 Elsevier GmbH. All rights reserved.

Comparison of dosimetric and radiobiological parameters on plans for prostate stereotactic body radiotherapy using an endorectal balloon for different dose-calculation algorithms and delivery-beam modes

NASA Astrophysics Data System (ADS)

Kang, Sang-Won; Suh, Tae-Suk; Chung, Jin-Beom; Eom, Keun-Yong; Song, Changhoon; Kim, In-Ah; Kim, Jae-Sung; Lee, Jeong-Woo; Cho, Woong

2017-02-01

The purpose of this study was to evaluate the impact of dosimetric and radiobiological parameters on treatment plans by using different dose-calculation algorithms and delivery-beam modes for prostate stereotactic body radiation therapy using an endorectal balloon. For 20 patients with prostate cancer, stereotactic body radiation therapy (SBRT) plans were generated by using a 10-MV photon beam with flattening filter (FF) and flattening-filter-free (FFF) modes. The total treatment dose prescribed was 42.7 Gy in 7 fractions to cover at least 95% of the planning target volume (PTV) with 95% of the prescribed dose. The dose computation was initially performed using an anisotropic analytical algorithm (AAA) in the Eclipse treatment planning system (Varian Medical Systems, Palo Alto, CA) and was then re-calculated using Acuros XB (AXB V. 11.0.34) with the same monitor units and multileaf collimator files. The dosimetric and the radiobiological parameters for the PTV and organs at risk (OARs) were analyzed from the dose-volume histogram. An obvious difference in dosimetric parameters between the AAA and the AXB plans was observed in the PTV and rectum. Doses to the PTV, excluding the maximum dose, were always higher in the AAA plans than in the AXB plans. However, doses to the other OARs were similar in both algorithm plans. In addition, no difference was observed in the dosimetric parameters for different delivery-beam modes when using the same algorithm to generate plans. As a result of the dosimetric parameters, the radiobiological parameters for the two algorithm plans presented an apparent difference in the PTV and the rectum. The average tumor control probability of the AAA plans was higher than that of the AXB plans. The average normal tissue complication probability (NTCP) to rectum was lower in the AXB plans than in the AAA plans. The AAA and the AXB plans yielded very similar NTCPs for the other OARs. In plans using the same algorithms, the NTCPs for delivery-beam modes showed no differences. This study demonstrated that the dosimetric and the radiobiological parameters for the PTV and the rectum affected the dose-calculation algorithms for prostate SBRT using an endorectal balloon. However, the dosimetric and the radiobiological parameters in the AAA and the AXB plans for other OARs were similar. Furthermore, difference between the dosimetric and the radiobiological parameters for different delivery-beam modes were not found when the same algorithm was used to generate the treatment plan.

Dosimetric verification for primary focal hypermetabolism of nasopharyngeal carcinoma patients treated with dynamic intensity-modulated radiation therapy.

PubMed

Xin, Yong; Wang, Jia-Yang; Li, Liang; Tang, Tian-You; Liu, Gui-Hong; Wang, Jian-She; Xu, Yu-Mei; Chen, Yong; Zhang, Long-Zhen

2012-01-01

To make sure the feasibility with (18F)FDG PET/CT to guided dynamic intensity-modulated radiation therapy (IMRT) for nasopharyngeal carcinoma patients, by dosimetric verification before treatment. Chose 11 patients in III~IVA nasopharyngeal carcinoma treated with functional image-guided IMRT and absolute and relative dosimetric verification by Varian 23EX LA, ionization chamber, 2DICA of I'mRT Matrixx and IBA detachable phantom. Drawing outline and making treatment plan were by different imaging techniques (CT and (18F)FDG PET/CT). The dose distributions of the various regional were realized by SMART. The absolute mean errors of interest area were 2.39%±0.66 using 0.6 cc ice chamber. Results using DTA method, the average relative dose measurements within our protocol (3%, 3 mm) were 87.64% at 300 MU/min in all filed. Dosimetric verification before IMRT is obligatory and necessary. Ionization chamber and 2DICA of I'mRT Matrixx was the effective dosimetric verification tool for primary focal hyper metabolism in functional image-guided dynamic IMRT for nasopharyngeal carcinoma. Our preliminary evidence indicates that functional image-guided dynamic IMRT is feasible.

Low frequency acoustic properties of Posidonia oceanica seagrass leaf blades

PubMed Central

Johnson, Jay R.; Venegas, Gabriel R.; Wilson, Preston S.; Hermand, Jean-Pierre

2017-01-01

The acoustics of seagrass meadows impacts naval and oceanographic sonar applications. To study this environment, a one-dimensional resonator was used to assess the low-frequency (1–5 kHz) acoustic response of the leaf blades of the Mediterranean seagrass Posidonia oceanica in water. Three separate collections of plants from Crete, Greece, and Sicily, Italy were investigated. A high consistency in effective sound speed was observed within each collection while a strong variability was observed between different collections. Average size, mass, and epiphytic coverage within each collection were quantified, and discoloration and stiffness are discussed qualitatively with respect to the observed acoustic variability. PMID:28618796

Herbivory by leaf-cutter ants changes the glandular trichomes density and the volatile components in an aromatic plant model

PubMed Central

Mayo Marques, Marcia Ortiz; Maria Rodrigues, Tatiane

2017-01-01

Abstract Herbivory can induce several structural and functional alterations in the plant secretory system. Glandular trichomes are the main sites of production of volatile organic compounds (VOCs) with several chemical properties in Lamiaceae species. Ocimum species usually have three morphotypes of glandular trichomes (morphotype I is peltate and has a wide four-celled head; morphotype II is capitate and has a unicellular head; and morphotype III is capitate with a bicellular head) which produce a great amount of terpenes, although other chemical categories of substances are also produced. Despite the abundance of trichomes producing important anti-herbivory components in their leaves, the association between Ocimum species and leaf-cutter ants has been commonly registered in Brazil. We investigated the effect of leaf-cutter ant attack on the density of the glandular trichomes and on the chemistry of the VOCs released from leaves of O. gratissimum. Plants were subjected to Acromyrmex rugosus attack until 90 % of leaves were removed. After 40 days from the leaf-cutter attack, both treatments were sampled. The glandular trichome density was analysed by scanning electron microscopy. The VOCs were extracted utilizing headspace solid-phase microextraction (HS-SPME) technique and analysed by gas chromatography. Generally, the density of glandular trichomes increased in the adaxial leaf surface of the attacked plants. However, we bring novelties on this topic since we analysed the density of each morphotype separately. The morphotype I decreased in the abaxial leaf surface, and increased in the adaxial leaf surface; the morphotype II increased in both leaf surfaces; and the morphotype III decreased in the abaxial leaf surface and remained constant in the adaxial leaf surface of attacked plants. In leaves of attacked plants, the (Z)-β-ocimene increased by 50 %, the α-selinene by 13 % and the germacrene D by 126 %, whereas the eugenol decreased by 70 %. Our data point to a differential response of each glandular morphotype in O. gratissimum and are consistent with the idea of a compartmentalization of functions among the different glandular morphotypes in the plant defence against environmental factors. PMID:29218139

Direct and indirect effects of light environment generate ecological trade-offs in herbivore performance and parasitism.

PubMed

Stoepler, Teresa M; Lill, John T

2013-10-01

A variety of ecological factors influence host use by parasitoids, including both abiotic and biotic factors. Light environment is one important abiotic parameter that differs among habitats and influences a suite of plant nutritional and resistance traits that in turn affect herbivore performance. However, the extent to which these bottom-up effects "cascade up" to affect higher trophic levels and the relative importance of direct and indirect effects of sunlight on tritrophic interactions are unclear. The objective of this study was to test how light environment (light gap vs. shaded forest understory) and leaf type (sun vs. shade leaves) affect the performance and incidence of parasitism of two species of moth larvae, Euclea delphinii and Acharia stimulea (Limacodidae). We manipulated the leaf phenotype of potted white oak saplings by growing them in either full sun or full shade throughout leaf expansion to produce sun and shade leaves, respectively. These saplings were then placed in light gap and adjacent shaded understory habitats in the forest in a full-factorial design, and stocked with sentinel larvae that were exposed to parasitism ("exposed" experiments). We reared additional larvae in sleeve cages (protected from parasitism) to isolate light environment and leaf phenotype treatment effects on larval performance in the absence of enemies ("bagged" experiments). In the exposed experiments, light environment strongly affected the likelihood of parasitism, while leaf phenotype did not. Euclea delphinii larvae were up to 6.6 times more likely to be parasitized in light gaps than in shaded understory habitats. This pattern was consistent for both tachinid fly and wasp parasitoids across two separate experiments. However, the larval performance of both species in the bagged experiments was maximized in the shade-habitat/sun-leaf treatment, a habitat/leaf-type combination that occurs infrequently in nature. Taken together, our results suggest that the direct effects of light environment on the incidence of parasitism supersede any indirect effects resulting from altered leaf quality and reveal inherent ecological trade-offs for herbivores confronted with choosing between sunny (high leaf quality, harsh environment, high parasitism) and shaded (reduced leaf quality less harsh environment, reduced parasitism) habitats.

Design considerations for a computer controlled multileaf collimator for the Harper Hospital fast neutron therapy facility.

PubMed

Maughan, Richard L; Yudelev, Mark; Aref, Amr; Chuba, Paul J; Forman, Jeffrey; Blosser, Emanuel J; Horste, Timothy

2002-04-01

The d(48.5) + Be neutron beam from the Harper Hospital superconducting cyclotron is collimated using a unique multirod collimator (MRC). A computer controlled multileaf collimator (MLC) is being designed to improve efficiency and allow for the future development of intensity modulated radiation therapy with neutrons. For the current study the use of focused or unfocused collimator leaves has been studied. Since the engineering effort associated with the leaf design and materials choice impacts significantly on cost, it was desirable to determine the clinical impact of using unfocused leaves in the MLC design. The MRC is a useful tool for studying the effects of using focused versus unfocused beams on beam penumbra. The effects of the penumbra for the different leaf designs on tumor and normal tissue DVHs in two selected sites (prostate and head and neck) was investigated. The increase in the penumbra resulting from using unfocused beams was small (approximately 1.5 mm for a 5 x 5 cm2 field and approximately 7.6 mm for a 25 x 25 cm2 field at 10 cm depth) compared to the contribution of phantom scatter to the penumbra width (5.4 and 20 mm for the small and large fields at 10 cm depth, respectively). Comparison of DVHs for tumor and critical normal tissue in a prostate and head and neck case showed that the dosimetric disadvantages of using an unfocused rather than focused beam were minimal and only significant at shallow depths. For the rare cases, where optimum penumbra conditions are required, a MLC incorporating tapered leaves and, thus, providing focused collimation in one plane is necessary.

Comparative Transcriptomics Unravel Biochemical Specialization of Leaf Tissues of Stevia for Diterpenoid Production.

PubMed

Kim, Mi Jung; Jin, Jingjing; Zheng, Junshi; Wong, Limsoon; Chua, Nam-Hai; Jang, In-Cheol

2015-12-01

Stevia (Stevia rebaudiana) produces not only a group of diterpenoid glycosides known as steviol glycosides (SGs), but also other labdane-type diterpenoids that may be spatially separated from SGs. However, their biosynthetic routes and spatial distribution in leaf tissues have not yet been elucidated. Here, we integrate metabolome and transcriptome analyses of Stevia to explore the biosynthetic capacity of leaf tissues for diterpenoid metabolism. Tissue-specific chemical analyses confirmed that SGs were accumulated in leaf cells but not in trichomes. On the other hand, Stevia leaf trichomes stored other labdane-type diterpenoids such as oxomanoyl oxide and agatholic acid. RNA sequencing analyses from two different tissues of Stevia provided a comprehensive overview of dynamic metabolic activities in trichomes and leaf without trichomes. These metabolite-guided transcriptomics and phylogenetic and gene expression analyses clearly identified specific gene members encoding enzymes involved in the 2-C-methyl-d-erythritol 4-phosphate pathway and the biosynthesis of steviol or other labdane-type diterpenoids. Additionally, our RNA sequencing analysis uncovered copalyl diphosphate synthase (SrCPS) and kaurene synthase1 (SrKS1) homologs, SrCPS2 and KS-like (SrKSL), which were specifically expressed in trichomes. In vitro and in planta assays showed that unlike SrCPS and SrKS1, SrCPS2 synthesized labda-13-en-8-ol diphosphate and successively catalyzed the formation of manoyl oxide and epi-manoyl oxide in combination with SrKSL. Our findings suggest that Stevia may have evolved to use distinct metabolic pathways to avoid metabolic interferences in leaf tissues for efficient production of diverse secondary metabolites. © 2015 American Society of Plant Biologists. All Rights Reserved.

Model estimates of leaf area and reference canopy stomatal conductance suggest correlation between phenology and physiology in both trembling aspen and red pine

NASA Astrophysics Data System (ADS)

Mackay, D. S.; Ewers, B. E.; Kruger, E. L.

2006-12-01

Phenological variations impact water and carbon fluxes, as evidenced by the large interannual variability of net ecosystem exchange of carbon dioxide and evapotranspiration (ET). In northern Wisconsin we observed daily variations of canopy transpiration from hardwoods from 1.0 to 1.7 mm/day during the leaf unfolding period and 1.7 to 2.6 mm/day with leaves fully out. Correlations between such flux rates and phenology have not been extensively tested and mechanistic connections are in their infancy. Some data suggest that stomatal conductance and photosynthesis increases up to full expansion. Moreover, in conifers, the interaction of phenology and physiology is more complicated than in deciduous trees because needles are retained for several years. Using inverse modeling with a coupled photosynthesis-transpiration model we estimated reference canopy stomatal conductance, Gsref, for red pine (Pinus resinosa), and Gsref and leaf area index, L, for trembling aspen (Populus tremuloides), using 30-min continuous sap flux data spanning a period from just prior to the start of leaf expansion to just after leaf senescence. The red pine showed Gsref ramp up from 105 to 179 mmol m-2 leaf s-1, which represented a 37 to 50 percent increase in Gsref after accounting for maximum possible changes in L. After full leaf out, the trembling aspen were almost immediately defoliated, and then reflushed after three weeks. Model estimates of L reflected this pattern and were consistent with measurements. However, Gsref never exceeded 45 mmol m-2 s-1 prior to defoliation, but peaked at 112 mmol m-2 s-1 after reflushing. These results support the need for further work that aims to separate phenology and physiology.

The fate of glyphosate in water hyacinth and its physiological and biochemical influences on growth of algae

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsai, Baolong.

Absorption, translocation, distribution, exudation, and guttation of {sup 14}C-glyphosate in water hyacinth (Eichhornia crassipes) were studied. Glyphosphate entered the plant by foliage and solution treatment. Plants were harvested and separated into the following parts: treated leaf blade, treated leaf petiole, young leaf blade, young leaf petiole, old leak blade, old leaf petiole, and root. Each part was extracted with methanol. Treated leaves, which exist only in foliage treatment, were washed with water and chloroform to remove the glyphosate residues. All {sup 14}C counting was made by liquid scintillation spectrometry. Autoradiography was used to locate {sup 14}C-glyphosate after foliage treatment. Resultsmore » indicated that glyphosate can be absorbed from the leaf surface and translocated rapidly through phloem tissues into the whole plant body. The roots of water hyacinth absorbed glyphosate without vertical transport. Guttation of glyphosate occurred in treated leaf tips. Exudation of glyphosate from roots of water hyacinth occurred within 8 hr after foliage treatment. Chlorella vulgaris, Chlamydomonas reihardii, Anabaena cylindrica, and Chroococcus turgidus were used to explore the physiological and biochemical effects of glyphosate on algae. Spectrophotometric assays were performed for algal growth, chlorophyll, carotenoids, phycobiliprotein, carbohydrate, and protein. TLC procedures and an image analyzer were used to detect the metabolites of glyphosate inside algal cells. The common visible symptom of glyphosate toxicity in all algal cells were bleaching effect and reduction of contents of carbohydrate, protein, and pigments. The results highly suggested that glyphosate injured the algal cells by destruction of photosynthetic pigments and resulted in lowering the contents of carbohydrate and protein in algal cells.« less

Anatomical basis of variation in mesophyll resistance in eastern Australian sclerophylls: news of a long and winding path

PubMed Central

Tosens, Tiina

2012-01-01

In sclerophylls, photosynthesis is particularly strongly limited by mesophyll diffusion resistance from substomatal cavities to chloroplasts (r m), but the controls on diffusion limits by integral leaf variables such as leaf thickness, density, and dry mass per unit area and by the individual steps along the diffusion pathway are imperfectly understood. To gain insight into the determinants of r m in leaves with varying structure, the full CO2 physical diffusion pathway was analysed in 32 Australian species sampled from sites contrasting in soil nutrients and rainfall, and having leaf structures from mesophytic to strongly sclerophyllous. r m was estimated based on combined measurements of gas exchange and chlorophyll fluorescence. In addition, r m was modelled on the basis of detailed anatomical measurements to separate the importance of different serial resistances affecting CO2 diffusion into chloroplasts. The strongest sources of variation in r m were S c/S, the exposed surface area of chloroplasts per unit leaf area, and mesophyll cell wall thickness, t cw. The strong correlation of r m with t cw could not be explained by cell wall thickness alone, and most likely arose from a further effect of cell wall porosity. The CO2 drawdown from intercellular spaces to chloroplasts was positively correlated with t cw, suggesting enhanced diffusional limitations in leaves with thicker cell walls. Leaf thickness and density were poorly correlated with S c/S, indicating that widely varying combinations of leaf anatomical traits occur at given values of leaf integrated traits, and suggesting that detailed anatomical studies are needed to predict r m for any given species. PMID:22888123

Autumnal leaf senescence in Miscanthus × giganteus and leaf [N] differ by stand age

PubMed Central

Boersma, Nicholas N.; Dohleman, Frank G.; Miguez, Fernando E.; Heaton, Emily A.

2015-01-01

Poor first winter survival in Miscanthus × giganteus has been anecdotally attributed to incomplete first autumn senescence, but these assessments never paired first-year with older M. × giganteus in side-by-side trials to separate the effect of weather from stand age. Here CO2 assimilation rate (A), photosystem II efficiency (ΦPSII), and leaf N concentration ([N]) were used to directly compare senescence in first, second, and third-year stands of M. × giganteus. Three M. × giganteus fields were planted with eight plots, one field each in 2009, 2010, and 2011. To quantify autumnal leaf senescence of plants within each stand age, photosynthetic and leaf [N] measurements were made twice weekly from early September until a killing frost. Following chilling events (daily temperature averages below 10 °C), photosynthetic rates in first year plants rebounded to a greater degree than those in second- and third-year plants. By the end of the growing season, first-year M. × giganteus had A and ΦPSII rates up to 4 times greater than third-year M. × giganteus, while leaf [N] was up to 2.4 times greater. The increased photosynthetic capability and leaf N status in first-year M. × giganteus suggests that the photosynthetic apparatus was not dismantled before a killing frost, thus potentially limiting nutrient translocation, and may explain why young M. × giganteus stands do not survive winter when older stands do. Because previous senescence research has primarily focused on annual or woody species, our results suggest that M. × giganteus may be an interesting herbaceous perennial system to investigate the interactive effects of plant ageing and nutrient status on senescence and may highlight management strategies that could potentially increase winter survival rates in first-year stands. PMID:25873682

Relationship between leaf traits and fire-response strategies in shrub species of a mountainous region of south-eastern Australia.

PubMed

Vivian, Lyndsey M; Cary, Geoffrey J

2012-01-01

Resprouting and seed recruitment are important ways in which plants respond to fire. However, the investments a plant makes into ensuring the success of post-fire resprouting or seedling recruitment can result in trade-offs that are manifested in a range of co-occurring morphological, life history and physiological traits. Relationships between fire-response strategies and other traits have been widely examined in fire-prone Mediterranean-type climates. In this paper, we aim to determine whether shrubs growing in a non-Mediterranean climate region exhibit relationships between their fire-response strategy and leaf traits. Field surveys were used to classify species into fire-response types. We then compared specific leaf area, leaf dry-matter content, leaf width, leaf nitrogen and carbon to nitrogen ratios between (a) obligate seeders and all other resprouters, and (b) obligate seeders, facultative resprouters and obligate resprouters. Leaf traits only varied between fire-response types when we considered facultative resprouters as a separate group to obligate resprouters, as observed after a large landscape-scale fire. We found no differences between obligate seeders and obligate resprouters, nor between obligate seeders and resprouters considered as one group. The results suggest that facultative resprouters may require a strategy of rapid resource acquisition and fast growth in order to compete with species that either resprout, or recruit from seed. However, the overall lack of difference between obligate seeders and obligate resprouters suggests that environmental factors are exerting similar effects on species' ecological strategies, irrespective of the constraints and trade-offs that may be associated with obligate seeding and obligate resprouting. These results highlight the limits to trait co-occurrences across different ecosystems and the difficulty in identifying global-scale relationships amongst traits.

Relationship between leaf traits and fire-response strategies in shrub species of a mountainous region of south-eastern Australia

PubMed Central

Vivian, Lyndsey M.; Cary, Geoffrey J.

2012-01-01

Background and Aims Resprouting and seed recruitment are important ways in which plants respond to fire. However, the investments a plant makes into ensuring the success of post-fire resprouting or seedling recruitment can result in trade-offs that are manifested in a range of co-occurring morphological, life history and physiological traits. Relationships between fire-response strategies and other traits have been widely examined in fire-prone Mediterranean-type climates. In this paper, we aim to determine whether shrubs growing in a non-Mediterranean climate region exhibit relationships between their fire-response strategy and leaf traits. Methods Field surveys were used to classify species into fire-response types. We then compared specific leaf area, leaf dry-matter content, leaf width, leaf nitrogen and carbon to nitrogen ratios between (a) obligate seeders and all other resprouters, and (b) obligate seeders, facultative resprouters and obligate resprouters. Key Results Leaf traits only varied between fire-response types when we considered facultative resprouters as a separate group to obligate resprouters, as observed after a large landscape-scale fire. We found no differences between obligate seeders and obligate resprouters, nor between obligate seeders and resprouters considered as one group. Conclusions The results suggest that facultative resprouters may require a strategy of rapid resource acquisition and fast growth in order to compete with species that either resprout, or recruit from seed. However, the overall lack of difference between obligate seeders and obligate resprouters suggests that environmental factors are exerting similar effects on species' ecological strategies, irrespective of the constraints and trade-offs that may be associated with obligate seeding and obligate resprouting. These results highlight the limits to trait co-occurrences across different ecosystems and the difficulty in identifying global-scale relationships amongst traits. PMID:21994052

Dosimetric effects of rotational offsets in stereotactic body radiation therapy (SBRT) for lung cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Yun; Catalano, Suzanne; Kelsey, Chris R.

2014-04-01

To quantitatively evaluate dosimetric effects of rotational offsets in stereotactic body radiation therapy (SBRT) for lung cancer. Overall, 11 lung SBRT patients (8 female and 3 male; mean age: 75.0 years) with medially located tumors were included. Treatment plans with simulated rotational offsets of 1°, 3°, and 5° in roll, yaw, and pitch were generated and compared with the original plans. Both clockwise and counterclockwise rotations were investigated. The following dosimetric metrics were quantitatively evaluated: planning target volume coverage (PTV V{sub 100%}), max PTV dose (PTV D{sub max}), percentage prescription dose to 0.35 cc of cord (cord D{sub 0.35} {submore » cc}), percentage prescription dose to 0.35 cc and 5 cc of esophagus (esophagus D{sub 0.35} {sub cc} and D{sub 5} {sub cc}), and volume of the lungs receiving at least 20 Gy (lung V{sub 20}). Statistical significance was tested using Wilcoxon signed rank test at the significance level of 0.05. Overall, small differences were found in all dosimetric matrices at all rotational offsets: 95.6% of differences were < 1% or < 1 Gy. Of all rotational offsets, largest change in PTV V{sub 100%}, PTV D{sub max}, cord D{sub 0.35} {sub cc}, esophagus D{sub 0.35} {sub cc}, esophagus D{sub 5} {sub cc}, and lung V{sub 20} was − 8.36%, − 6.06%, 11.96%, 8.66%, 6.02%, and − 0.69%, respectively. No significant correlation was found between any dosimetric change and tumor-to-cord/esophagus distances (R{sup 2} range: 0 to 0.44). Larger dosimetric changes and intersubject variations were observed at larger rotational offsets. Small dosimetric differences were found owing to rotational offsets up to 5° in lung SBRT for medially located tumors. Larger intersubject variations were observed at larger rotational offsets.« less

SU-F-T-05: Dosimetric Evaluation and Validation of Newlydeveloped Well Chamber for Use in the Calibration of Brachytherapy Sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saminathan, S; Godson, H; Ponmalar, R

2016-06-15

Purpose: To evaluate the dosimetric characteristics of newly developed well type ionization chamber and to validate the results with the commercially available calibrated well chambers that are being used for the calibration of brachytherapy sources. Methods: The newly developed well type ionization chamber (BDS 1000) has been designed for the convenient use in brachytherapy which is open to atmospheric condition. The chamber has a volume of 240 cm3 and weight of 2.5 Kg. The calibration of the radioactive source with activities from 0.01 mCi to 20 Ci can be carried out using this chamber. The dosimetric parameters such as leakagemore » current, stability, scattering effect, ion collection efficiency, reference air kerma rate and nominal response with energy were carried out with the BDS 1000 well type ion chamber. The evaluated dosimetric characteristics of BDS1000 well chamber were validated with two other commercially available well chambers (HDR 1000 plus and BTC/3007). Results: The measured leakage current observed was negligible for the newly developed BDS 1000 well type ion chamber. The ion collection efficiency was close to 1 and the response of the chamber was found to be very stable. The determined sweet spot was at 42 mm from bottom of the chamber insert. The reference air kerma rate was found to be 4.634 × 105 Gym2hr-1A-1 for the BDS 1000 well chamber. The overall dosimetric characteristics of BDS 1000 well chamber was in good agreement with the dosimetric properties of other two well chambers. Conclusion: The dosimetric study shows that the newly developed BDS 1000 well type ionization chamber is high sensitive and reliable chamber for reference air kerma strength calibration. The results obtained confirm that this chamber can be used for the calibration of HDR and LDR brachytherapy sources.« less

On the use of advanced numerical models for the evaluation of dosimetric parameters and the verification of exposure limits at workplaces.

PubMed

Catarinucci, L; Tarricone, L

2009-12-01

With the next transposition of the 2004/40/EC Directive, employers will become responsible for the electromagnetic field level at the workplace. To make this task easier, the scientific community is compiling practical guidelines to be followed. This work aims at enriching such guidelines, especially for the dosimetric issues. More specifically, some critical aspects related to the application of numerical dosimetric techniques for the verification of the safety limit compliance have been highlighted. In particular, three different aspects have been considered: the dosimetric parameter dependence on the shape and the inner characterisation of the exposed subject as well as on the numerical algorithm used, and the correlation between reference limits and basic restriction. Results and discussions demonstrate how, even by using sophisticated numerical techniques, in some cases a complex interpretation of the result is mandatory.

Comparison of the dose distribution obtained from dosimetric systems with intensity modulated radiotherapy planning system in the treatment of prostate cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gökçe, M., E-mail: mgokce@adu.edu.tr; Uslu, D. Koçyiğit; Ertunç, C.

The aim of this study is to compare Intensity Modulated Radiation Therapy (IMRT) plan of prostate cancer patients with different dose verification systems in dosimetric aspects and to compare these systems with each other in terms of reliability, applicability and application time. Dosimetric control processes of IMRT plan of three prostate cancer patients were carried out using thermoluminescent dosimeter (TLD), ion chamber (IC) and 2D Array detector systems. The difference between the dose values obtained from the dosimetric systems and treatment planning system (TPS) were found to be about % 5. For the measured (TLD) and calculated (TPS) doses %3more » percentage differences were obtained for the points close to center while percentage differences increased at the field edges. It was found that TLD and IC measurements will increase the precision and reliability of the results of 2D Array.« less

CyberArc: a non-coplanar-arc optimization algorithm for CyberKnife

NASA Astrophysics Data System (ADS)

Kearney, Vasant; Cheung, Joey P.; McGuinness, Christopher; Solberg, Timothy D.

2017-07-01

The goal of this study is to demonstrate the feasibility of a novel non-coplanar-arc optimization algorithm (CyberArc). This method aims to reduce the delivery time of conventional CyberKnife treatments by allowing for continuous beam delivery. CyberArc uses a 4 step optimization strategy, in which nodes, beams, and collimator sizes are determined, source trajectories are calculated, intermediate radiation models are generated, and final monitor units are calculated, for the continuous radiation source model. The dosimetric results as well as the time reduction factors for CyberArc are presented for 7 prostate and 2 brain cases. The dosimetric quality of the CyberArc plans are evaluated using conformity index, heterogeneity index, local confined normalized-mutual-information, and various clinically relevant dosimetric parameters. The results indicate that the CyberArc algorithm dramatically reduces the treatment time of CyberKnife plans while simultaneously preserving the dosimetric quality of the original plans.

CyberArc: a non-coplanar-arc optimization algorithm for CyberKnife.

PubMed

Kearney, Vasant; Cheung, Joey P; McGuinness, Christopher; Solberg, Timothy D

2017-06-26

The goal of this study is to demonstrate the feasibility of a novel non-coplanar-arc optimization algorithm (CyberArc). This method aims to reduce the delivery time of conventional CyberKnife treatments by allowing for continuous beam delivery. CyberArc uses a 4 step optimization strategy, in which nodes, beams, and collimator sizes are determined, source trajectories are calculated, intermediate radiation models are generated, and final monitor units are calculated, for the continuous radiation source model. The dosimetric results as well as the time reduction factors for CyberArc are presented for 7 prostate and 2 brain cases. The dosimetric quality of the CyberArc plans are evaluated using conformity index, heterogeneity index, local confined normalized-mutual-information, and various clinically relevant dosimetric parameters. The results indicate that the CyberArc algorithm dramatically reduces the treatment time of CyberKnife plans while simultaneously preserving the dosimetric quality of the original plans.

Errors in radiation oncology: A study in pathways and dosimetric impact

PubMed Central

Drzymala, Robert E.; Purdy, James A.; Michalski, Jeff

2005-01-01

As complexity for treating patients increases, so does the risk of error. Some publications have suggested that record and verify (R&V) systems may contribute in propagating errors. Direct data transfer has the potential to eliminate most, but not all, errors. And although the dosimetric consequences may be obvious in some cases, a detailed study does not exist. In this effort, we examined potential errors in terms of scenarios, pathways of occurrence, and dosimetry. Our goal was to prioritize error prevention according to likelihood of event and dosimetric impact. For conventional photon treatments, we investigated errors of incorrect source‐to‐surface distance (SSD), energy, omitted wedge (physical, dynamic, or universal) or compensating filter, incorrect wedge or compensating filter orientation, improper rotational rate for arc therapy, and geometrical misses due to incorrect gantry, collimator or table angle, reversed field settings, and setup errors. For electron beam therapy, errors investigated included incorrect energy, incorrect SSD, along with geometric misses. For special procedures we examined errors for total body irradiation (TBI, incorrect field size, dose rate, treatment distance) and LINAC radiosurgery (incorrect collimation setting, incorrect rotational parameters). Likelihood of error was determined and subsequently rated according to our history of detecting such errors. Dosimetric evaluation was conducted by using dosimetric data, treatment plans, or measurements. We found geometric misses to have the highest error probability. They most often occurred due to improper setup via coordinate shift errors or incorrect field shaping. The dosimetric impact is unique for each case and depends on the proportion of fields in error and volume mistreated. These errors were short‐lived due to rapid detection via port films. The most significant dosimetric error was related to a reversed wedge direction. This may occur due to incorrect collimator angle or wedge orientation. For parallel‐opposed 60° wedge fields, this error could be as high as 80% to a point off‐axis. Other examples of dosimetric impact included the following: SSD, ~2%/cm for photons or electrons; photon energy (6 MV vs. 18 MV), on average 16% depending on depth, electron energy, ~0.5cm of depth coverage per MeV (mega‐electron volt). Of these examples, incorrect distances were most likely but rapidly detected by in vivo dosimetry. Errors were categorized by occurrence rate, methods and timing of detection, longevity, and dosimetric impact. Solutions were devised according to these criteria. To date, no one has studied the dosimetric impact of global errors in radiation oncology. Although there is heightened awareness that with increased use of ancillary devices and automation, there must be a parallel increase in quality check systems and processes, errors do and will continue to occur. This study has helped us identify and prioritize potential errors in our clinic according to frequency and dosimetric impact. For example, to reduce the use of an incorrect wedge direction, our clinic employs off‐axis in vivo dosimetry. To avoid a treatment distance setup error, we use both vertical table settings and optical distance indicator (ODI) values to properly set up fields. As R&V systems become more automated, more accurate and efficient data transfer will occur. This will require further analysis. Finally, we have begun examining potential intensity‐modulated radiation therapy (IMRT) errors according to the same criteria. PACS numbers: 87.53.Xd, 87.53.St PMID:16143793

Normal and Reversed-Phase Thin Layer Chromatography of Green Leaf Extracts

ERIC Educational Resources Information Center

Sjursnes, Birte Johanne; Kvittingen, Lise; Schmid, Rudolf

2015-01-01

Introductory experiments of chromatography are often conducted by separating colored samples, such as inks, dyes, and plant extracts, using filter paper, chalk, or thin layer chromatography (TLC) plates with various solvent systems. Many simple experiments have been reported. The relationship between normal chromatography and reversed-phase…

The plant economics spectrum is structured by leaf habits and growth forms across subtropical species.

PubMed

Zhao, Yan-Tao; Ali, Arshad; Yan, En-Rong

2017-02-01

The plant economics spectrum that integrates the combination of leaf and wood syndromes provides a useful framework for the examination of species strategies at the whole-plant level. However, it remains unclear how species that differ in leaf habits and growth forms are integrated within the plant economics spectrum in subtropical forests. We measured five leaf and six wood traits across 58 subtropical plant species, which represented two leaf habits (evergreen vs deciduous) and two growth forms (tree vs shrub) in eastern China. Principal component analysis (PCA) was employed separately to construct the leaf (LES), wood (WES) and whole-plant (WPES) economics spectra. Leaf and wood traits are highly intra- and intercorrelated, thus defining not only the LES and WES, but also a WPES. Multi-trait variations in PCAs revealed that the traits which were representative of the acquisitive strategy, i.e., cheap tissue investment and rapid returns on that investment, were clustered at one end, while traits that represented the conservative strategy, i.e., expensive tissue investment and slower returns, were clustered at other end in each of the axes of the leaf and wood syndromes (PC1-axis) and the plant height strategy (PC2-axis). The local WPES, LES and WES were tightly correlated with each other. Evergreens shaped the conservative side, while deciduous species structured the acquisitive side of the WPES and LES. With respect to plant height strategies, trees formulated the acquisitive side and shrub species made up the conservative side of the WPES, LES and WES. In conclusion, our results suggested that the LES and WES were coordinated to a WPES for subtropical species. The finding of this local spectrum of plant form and function would be beneficial for modeling nutrient fluxes and species compositions in the changing climate, but also for understanding species strategies in an evolutionary context. © The Author 2016. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Comparative study on anti-oxidant and anti-inflammatory activities of Caesalpinia crista and Centella asiatica leaf extracts

PubMed Central

Ramesh, B. N.; Girish, T. K.; Raghavendra, R. H.; Naidu, K. Akhilender; Rao, U. J. S. Prasada; Rao, K. S.

2014-01-01

Background: Amyloidosis, oxidative stress and inflammation have been strongly implicated in neurodegenerative disorders like Alzheimer's disease. Traditionally, Caesalpinia crista and Centella asiatica leaf extracts are used to treat brain related diseases in India. C. crista is used as a mental relaxant drink as well as to treat inflammatory diseases, whereas C. asiatica is reported to be used to enhance memory and to treat dementia. Objective: The present study is aimed to understand the anti-oxidant and anti-inflammatory potential of C. asiatica and C. crista leaf extracts. Materials and Methods: Phenolic acid composition of the aqueous extracts of C. crista and C. asiatica were separated on a reverse phase C18 column (4.6 x 250 mm) using HPLC system. Antioxidant properties of the leaf extracts were determined by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay and the reducing potential assay. The anti-inflammatory activities of aqueous extracts of C. crista and C. asiatica were studied using 5-lipoxygenase assay. Polymorphonuclear leukocytes (PMNLs) were isolated from blood by Ficoll-Histopaque density gradient followed by hypotonic lysis of erythrocytes. Results: Gallic, protocatechuic, gentisic, chlorogenic, caffeic, p-coumaric and ferulic acids were the phenolic acids identified in C. crista and C. asiatica leaf aqueous extracts. However, gallic acid and ferulic acid contents were much higher in C. crista compared to C. asiatica. Leaf extracts of C. asiatica and C. crista exhibited antioxidant properties and inhibited 5-lipoxygenase (anti-inflammatory) in a dose dependent manner. However, leaf extracts of C. crista had better antioxidant and anti-inflammatory activity compared to that of C. asiatica. The better activity of C. crista is attributed to high gallic acid and ferulic acid compared to C. asiatica. Conclusions: Thus, the leaf extract of C. crista can be a potential therapeutic role for Alzheimer's disease. PMID:24741275

A novel method of measuring leaf epidermis and mesophyll stiffness shows the ubiquitous nature of the sandwich structure of leaf laminas in broad-leaved angiosperm species

PubMed Central

Onoda, Yusuke; Schieving, Feike; Anten, Niels P. R.

2015-01-01

Plant leaves commonly exhibit a thin, flat structure that facilitates a high light interception per unit mass, but may increase risks of mechanical failure when subjected to gravity, wind and herbivory as well as other stresses. Leaf laminas are composed of thin epidermis layers and thicker intervening mesophyll layers, which resemble a composite material, i.e. sandwich structure, used in engineering constructions (e.g. airplane wings) where high bending stiffness with minimum weight is important. Yet, to what extent leaf laminas are mechanically designed and behave as a sandwich structure remains unclear. To resolve this issue, we developed and applied a novel method to estimate stiffness of epidermis- and mesophyll layers without separating the layers. Across a phylogenetically diverse range of 36 angiosperm species, the estimated Young’s moduli (a measure of stiffness) of mesophyll layers were much lower than those of the epidermis layers, indicating that leaf laminas behaved similarly to efficient sandwich structures. The stiffness of epidermis layers was higher in evergreen species than in deciduous species, and strongly associated with cuticle thickness. The ubiquitous nature of sandwich structures in leaves across studied species suggests that the sandwich structure has evolutionary advantages as it enables leaves to be simultaneously thin and flat, efficiently capturing light and maintaining mechanical stability under various stresses. PMID:25675956

Topological detector: measuring continuous dosimetric quantities with few-element detector array.

PubMed

Han, Zhaohui; Brivio, Davide; Sajo, Erno; Zygmanski, Piotr

2016-08-21

A prototype topological detector was fabricated and investigated for quality assurance of radiation producing medical devices. Unlike a typical array or flat panel detector, a topological detector, while capable of achieving a very high spatial resolution, consists of only a few elements and therefore is much simpler in construction and more cost effective. The key feature allowing this advancement is a geometry-driven design that is customized for a specific dosimetric application. In the current work, a topological detector of two elements was examined for the positioning verification of the radiation collimating devices (jaws, MLCs, and blades etc). The detector was diagonally segmented from a rectangular thin film strip (2.5 cm  ×  15 cm), giving two contiguous but independent detector elements. The segmented area was the central portion of the strip measuring 5 cm in length. Under irradiation, signals from each detector element were separately digitized using a commercial multichannel data acquisition system. The center and size of an x-ray field, which were uniquely determined by the collimator positions, were shown mathematically to relate to the difference and sum of the two signals. As a proof of concept, experiments were carried out using slit x-ray fields ranging from 2 mm to 20 mm in size. It was demonstrated that, the collimator positions can be accurately measured with sub-millimeter precisions.

Tomato growth as affected by root-zone temperature and the addition of gibberellic acid and kinetin to nutrient solutions

NASA Technical Reports Server (NTRS)

Bugbee, B.; White, J. W.; Salisbury, F. B. (Principal Investigator)

1984-01-01

The effect of root-zone temperature on young tomato plants (Lycopersicon esculentum Mill. cv. Heinz 1350) was evaluated in controlled environments using a recirculating solution culture system. Growth rates were measured at root-zone temperatures of 15 degrees, 20 degrees, 25 degrees, and 30 degrees C in a near optimum foliar environment. Optimum growth occurred at 25 degrees to 30 degrees during the first 4 weeks of growth and 20 degrees to 25 degrees during the 5th and 6th weeks. Growth was severely restricted at 15 degrees. Four concentrations of gibberellic acid (GA3) and kinetin were added to the nutrient solution in a separate trial; root-zone temperature was maintained at 15 degrees and 25 degrees. Addition of 15 micromoles GA3 to solutions increased specific leaf area, total leaf area, and dry weight production of plants in both temperature treatments. GA3-induced growth stimulation was greater at 15 degrees than at 25 degrees. GA3 may promote growth by increasing leaf area, enhancing photosynthesis per unit leaf area, or both. Kinetic was not useful in promoting growth at either temperature.

The significance of the choice of radiobiological (NTCP) models in treatment plan objective functions.

PubMed

Miller, J; Fuller, M; Vinod, S; Suchowerska, N; Holloway, L

2009-06-01

A Clinician's discrimination between radiation therapy treatment plans is traditionally a subjective process, based on experience and existing protocols. A more objective and quantitative approach to distinguish between treatment plans is to use radiobiological or dosimetric objective functions, based on radiobiological or dosimetric models. The efficacy of models is not well understood, nor is the correlation of the rank of plans resulting from the use of models compared to the traditional subjective approach. One such radiobiological model is the Normal Tissue Complication Probability (NTCP). Dosimetric models or indicators are more accepted in clinical practice. In this study, three radiobiological models, Lyman NTCP, critical volume NTCP and relative seriality NTCP, and three dosimetric models, Mean Lung Dose (MLD) and the Lung volumes irradiated at 10Gy (V10) and 20Gy (V20), were used to rank a series of treatment plans using, harm to normal (Lung) tissue as the objective criterion. None of the models considered in this study showed consistent correlation with the Radiation Oncologists plan ranking. If radiobiological or dosimetric models are to be used in objective functions for lung treatments, based on this study it is recommended that the Lyman NTCP model be used because it will provide most consistency with traditional clinician ranking.

Dosimetric impact of geometric errors due to respiratory motion prediction on dynamic multileaf collimator-based four-dimensional radiation delivery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vedam, S.; Docef, A.; Fix, M.

2005-06-15

The synchronization of dynamic multileaf collimator (DMLC) response with respiratory motion is critical to ensure the accuracy of DMLC-based four dimensional (4D) radiation delivery. In practice, however, a finite time delay (response time) between the acquisition of tumor position and multileaf collimator response necessitates predictive models of respiratory tumor motion to synchronize radiation delivery. Predicting a complex process such as respiratory motion introduces geometric errors, which have been reported in several publications. However, the dosimetric effect of such errors on 4D radiation delivery has not yet been investigated. Thus, our aim in this work was to quantify the dosimetric effectsmore » of geometric error due to prediction under several different conditions. Conformal and intensity modulated radiation therapy (IMRT) plans for a lung patient were generated for anterior-posterior/posterior-anterior (AP/PA) beam arrangements at 6 and 18 MV energies to provide planned dose distributions. Respiratory motion data was obtained from 60 diaphragm-motion fluoroscopy recordings from five patients. A linear adaptive filter was employed to predict the tumor position. The geometric error of prediction was defined as the absolute difference between predicted and actual positions at each diaphragm position. Distributions of geometric error of prediction were obtained for all of the respiratory motion data. Planned dose distributions were then convolved with distributions for the geometric error of prediction to obtain convolved dose distributions. The dosimetric effect of such geometric errors was determined as a function of several variables: response time (0-0.6 s), beam energy (6/18 MV), treatment delivery (3D/4D), treatment type (conformal/IMRT), beam direction (AP/PA), and breathing training type (free breathing/audio instruction/visual feedback). Dose difference and distance-to-agreement analysis was employed to quantify results. Based on our data, the dosimetric impact of prediction (a) increased with response time, (b) was larger for 3D radiation therapy as compared with 4D radiation therapy, (c) was relatively insensitive to change in beam energy and beam direction, (d) was greater for IMRT distributions as compared with conformal distributions, (e) was smaller than the dosimetric impact of latency, and (f) was greatest for respiration motion with audio instructions, followed by visual feedback and free breathing. Geometric errors of prediction that occur during 4D radiation delivery introduce dosimetric errors that are dependent on several factors, such as response time, treatment-delivery type, and beam energy. Even for relatively small response times of 0.6 s into the future, dosimetric errors due to prediction could approach delivery errors when respiratory motion is not accounted for at all. To reduce the dosimetric impact, better predictive models and/or shorter response times are required.« less

SU-F-T-304: Complex Multi-PTV Treatment Evaluation Using a Remotely Processed 3D Gel Dosimeter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoisak, J; Dragojevic, I; Sutlief, S

Purpose: A new 3D gel dosimeter (ClearView™, Modus Medical Systems) was investigated for use as a QA tool for stereotactic radiosurgery (SRS) plans exhibiting high dose gradients and spatially separated treatment targets. The unique feature of this gel dosimeter is the remote processing service provided by Modus Medical Systems. Methods: The gel dosimeters were filled in either 10 cm diameter or 15 cm diameter clear plastic jars. The jars were then shipped in ice-cooled containers to our department for irradiation. Clinical SRS plans for treatment of multiple metastases and plans with simulated concave structures were applied to a CT scanmore » of the gel dosimeter. The gel was irradiated in treatment position using modulated arcs and then returned in the cooled container for processing. The 3D gel dose was compared to the DICOM-RT dose from the treatment plan to assess dosimetric and geometric agreement. Results: There was no discernible difference between the planned and measured dose for dose gradients as high as 10%/mm, which was the highest gradient we evaluated. Geometric agreement for distant metastases separated by 6 cm was within 1.5 mm. Among three identically irradiated gels using a plan intended for nine metastases, the 3%/3mm gamma passing rate was 84.5% with a range of 14.7%, measured over the entire volume of the dosimeter. Regions of larger gamma values correlated with geometric offsets between the planned and measured data. Conclusion: The gel dosimeter exhibits the dosimetric and geometric characteristics necessary for 3D evaluation of treatment plan deliverability. The range of observed gamma passing rates suggests a high sensitivity to geometric registration. With proper management of geometric registration between planned and measured data, this service should enable a radiation oncology department to use 3D dosimetry in end-to-end testing or patient plan delivery QA without the expense of an in-house processing system.« less

Combined performance of biochar sorption and magnetic separation processes for treatment of chromium-contained electroplating wastewater.

PubMed

Wang, Sheng-ye; Tang, Yan-kui; Li, Kun; Mo, Ya-yuan; Li, Hao-feng; Gu, Zhan-qi

2014-12-01

Magnetic biochar was prepared with eucalyptus leaf residue remained after essential oil being extracted. Batch experiments were conducted to examine the capacity of the magnetic biochar to remove Cr (VI) from electroplating wastewater and to be separated by an external magnetic field. The results show that the initial solution pH plays an important role on both sorption and separation. The removal rates of Cr (VI), total Cr, Cu (II), and Ni (II) were 97.11%, 97.63%, 100% and 100%, respectively. The turbidity of the sorption-treated solution was reduced to 21.8NTU from 4075NTU after 10min magnetic separation. The study also confirms that the magnetic biochar still retains the original magnetic separation performance after the sorption process. Copyright © 2014 Elsevier Ltd. All rights reserved.

Monte Carlo dosimetric characterization of the Flexisource Co-60 high-dose-rate brachytherapy source using PENELOPE.

PubMed

Almansa, Julio F; Guerrero, Rafael; Torres, Javier; Lallena, Antonio M

60 Co sources have been commercialized as an alternative to 192 Ir sources for high-dose-rate (HDR) brachytherapy. One of them is the Flexisource Co-60 HDR source manufactured by Elekta. The only available dosimetric characterization of this source is that of Vijande et al. [J Contemp Brachytherapy 2012; 4:34-44], whose results were not included in the AAPM/ESTRO consensus document. In that work, the dosimetric quantities were calculated as averages of the results obtained with the Geant4 and PENELOPE Monte Carlo (MC) codes, though for other sources, significant differences have been quoted between the values obtained with these two codes. The aim of this work is to perform the dosimetric characterization of the Flexisource Co-60 HDR source using PENELOPE. The MC simulation code PENELOPE (v. 2014) has been used. Following the recommendations of the AAPM/ESTRO report, the radial dose function, the anisotropy function, the air-kerma strength, the dose rate constant, and the absorbed dose rate in water have been calculated. The results we have obtained exceed those of Vijande et al. In particular, the absorbed dose rate constant is ∼0.85% larger. A similar difference is also found in the other dosimetric quantities. The effect of the electrons emitted in the decay of 60 Co, usually neglected in this kind of simulations, is significant up to the distances of 0.25 cm from the source. The systematic and significant differences we have found between PENELOPE results and the average values found by Vijande et al. point out that the dosimetric characterizations carried out with the various MC codes should be provided independently. Copyright © 2017 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

Application of dual-energy CT to suppression of metal artefact caused by pedicle screw fixation in radiotherapy: a feasibility study using original phantom

NASA Astrophysics Data System (ADS)

Wang, Tianyuan; Ishihara, Takeaki; Kono, Atsushi; Yoshida, Naoki; Akasaka, Hiroaki; Mukumoto, Naritoshi; Yada, Ryuichi; Ejima, Yasuo; Yoshida, Kenji; Miyawaki, Daisuke; Kakutani, Kenichiro; Nishida, Kotaro; Negi, Noriyuki; Minami, Toshiaki; Aoyama, Yuuichi; Takahashi, Satoru; Sasaki, Ryohei

2017-08-01

The objective of the present study was the determination of the potential dosimetric benefits of using metal-artefact-suppressed dual-energy computed tomography (DECT) images for cases involving pedicle screw implants in spinal sites. A heterogeneous spinal phantom was designed for the investigation of the dosimetric effect of the pedicle-screw-related artefacts. The dosimetric comparisons were first performed using a conventional two-directional opposed (AP-PA) plan, and then a volumetric modulated arc therapy (VMAT) plan, which are both used for the treatment of spinal metastases in our institution. The results of Acuros® XB dose-to-medium (Dm) and dose-to-water (Dw) calculations using different imaging options were compared with experimental measurements including the chamber and film dosimetries in the spinal phantom. A dual-energy composition image with a weight factor of  -0.2 and a dual-energy monochromatic image (DEMI) with an energy level of 180 keV were found to have superior abilities for artefact suppression. The Dm calculations revealed greater dosimetric effects of the pedicle screw-related artefacts compared to the Dw calculations. The results of conventional single-energy computed tomography showed that, although the pedicle screws were made from low-Z titanium alloy, the metal artefacts still have dosimetric effects, namely, an average (maximum) Dm error of 4.4% (5.6%) inside the spinal cord for a complex VMAT treatment plan. Our findings indicate that metal-artefact suppression using the proposed DECT (DEMI) approach is promising for improving the dosimetric accuracy near the implants and inside the spinal cord (average (maximum) Dm error of 1.1% (2.0%)).

Dosimetric evaluation of Plastic Water Diagnostic-Therapy.

PubMed

Ramaseshan, Ramani; Kohli, Kirpal; Cao, Fred; Heaton, Robert K

2008-04-29

High-precision radiotherapy planning and quality assurance require accurate dosimetric and geometric phantom measurements. Phantom design requires materials with mechanical strength and resilience, and dosimetric properties close to those of water over diagnostic and therapeutic ranges. Plastic Water Diagnostic Therapy (PWDT: CIRS, Norfolk, VA) is a phantom material designed for water equivalence in photon beams from 0.04 MeV to 100 MeV; the material has also good mechanical properties. The present article reports the results of computed tomography (CT) imaging and dosimetric studies of PWDT to evaluate the suitability of the material in CT and therapy energy ranges. We characterized the water equivalence of PWDT in a series of experiments in which the basic dosimetric properties of the material were determined for photon energies of 80 kVp, 100 kVp, 250 kVp, 4 MV, 6 MV, 10 MV, and 18 MV. Measured properties included the buildup and percentage depth dose curves for several field sizes, and relative dose factors as a function of field size. In addition, the PWDT phantom underwent CT imaging at beam qualities ranging from 80 kVp to 140 kVp to determine the water equivalence of the phantom in the diagnostic energy range. The dosimetric quantities measured with PWDT agreed within 1.5% of those determined in water and Solid Water (Gammex rmi, Middleton, WI). Computed tomography imaging of the phantom was found to generate Hounsfield numbers within 0.8% of those generated using water. The results suggest that PWDT material is suitable both for regular radiotherapy quality assurance measurements and for intensity-modulated radiation therapy (IMRT) verification work. Sample IMRT verification results are presented.

Dosimetric effects of endorectal balloons on intensity-modulated radiation therapy plans for prostate cancer

NASA Astrophysics Data System (ADS)

Kim, Jae-Sung; Chung, Jin-Beom; Kim, In-Ah; Eom, Keun-Yong

2013-10-01

We used an endorectal balloon (ERB) for prostate immobilization during intensity-modulated radiotherapy (IMRT) for prostate cancer treatment. To investigate the dosimetric effects of ERB-filling materials, we changed the ERB Hounsfield unit (HU) from 0 to 1000 HU in 200-HU intervals to simulate the various ERB fillings; 0 HU simulated a water-filled ERB, and 1000 HU simulated the densest material-filled ERB. Dosimetric data (coverage, homogeneity, conformity, maximal dose, and typical volume dose) for the tumor and the organs at risk (OARs) were evaluated in prostate IMRT treatment plans with 6-MV and 15-MV beams. The tumor coverage appeared to differ by approximately 1%, except for the clinical target volume (CTV) V100% and the planning target volume (PTV) V100%. The largest difference for the various ERB fillings was observed in the PTV V100%. In spite of increasing HU, the prostate IMRT plans at both energies had relatively low dosimetric effects on the PTV and the CTV. However, the maximal and the typical volume doses (D25%, D30%, and D50%) to the rectal wall and the bladder increased with increasing HU. For an air-filled ERB, the maximal doses to the rectal wall and the monitor units were lower than the corresponding values for the water-filled and the densest material-filled ERBs. An air-filled ERB spared the rectal wall because of its dosimetric effect. Thus, we conclude that the use of an air-filled ERB provides a dosimetric benefit to the rectal wall without a loss of target coverage and is an effective option for prostate IMRT treatment.

[Inhibitory effect on Microcystis aeruginosa as well as separation and identification of the allelochemicals of welsh onion].

PubMed

Zhou, Yang; Li, Yuan; Li, Cheng; Liu, Lu; Zhang, Tingting

2013-11-01

To study the inhibition of welsh onion on Microcystis aeruginosa, and separat and identify of the allelochemicals from welsh onion. METHEDS: The inhibitory effect of different concentrations of fistular onion stalk and fistular onion leaf water extracts on M. aeruginosa were studied; besides, separation and identification of the allelochemicals of welsh onion were also studied. Both fistular onion stalk and fistular onion leaf water extracts had, to different degree, inhibitory effect on the growth of M. aeruginosat. Compared with the control group, the fluorescence intensity of fistular onion stalk and fistular onion leaf were lower than the control group in the same period, and the inhibitory effect were more obvious with the increase of the water extract concentrations, to the fifth day, M. aeruginosa almost completely dead of the highest concentration(50 ml/L) of fistular onion stalk water extract treated group, the EC50 of water extract from fistular onion stalk to M. aeruginosa was 12.7 ml/L, equivalent to fresh weight 1.27 g/L. Main allelochemicals in fistular onion stalk includes allyl mercaptan, cyclopentyl mercaptan, and so on. The inhibiting assay on M. aeruginosa showed that the EC50 of allyl mercaptan and cyclopentyl mercaptan respectively were 0.03 and 0.02 g/L. The fistular onion stalk water extracts has very good algicidal effect, allelopathic algal inhibiting substances primarily are sulfocompound, which have the potential to develop into biological algicide.

Segregation and Alteration of Phenolic and Aliphatic Components of Root and Leaf Litter by Detritivores and Microbes

NASA Astrophysics Data System (ADS)

Filley, T. R.; Altmann, J.; Szlavecz, K. A.; Kalbitz, K.; Gamblin, D.; Nierop, K.

2012-12-01

The physical and microbial transformation of plant detritus in the litter layer and soil is accompanied by chemical separation of progressively soluble fractions and their movement into the rhizosphere driving subsequent soil processes. We investigated the combined action of specific detritivores, microbial decay, and leaching on the chemical separation of plant aromatic and aliphatic components from root, wood, and leaf tissue using 13C-TMAH thermochemolysis. This method enabled the simultaneous analysis of hydrolyzable tannin and lignin fragments, substituted fatty acids, and condensed tannin composition and revealed process-specific chemical transformations to plant secondary compounds. Long-term incubation and field sampling demonstrated how plant residues are progressively leached of the water soluble, oxidized fragments generated through decay. The residues appeared only slightly altered, in the case of brown rot wood, or enriched in aliphatic fragments, in the case of leaf and root tissue. Water extractable fractions were always selectively dominated by polyphenolics, either as demethylated lignin or tannins, and nearly devoid of aliphatic materials, despite high concentrations in the starting materials. Additionally, for plant materials with high tannin contents, such as pine needles, consumption and passage through some arthropod guts revealed what appeared to be microbially-mediated methylation of phenols, and a loss of tannins in leachates. These findings are indications for an in-situ phenol detoxification mechanism. This research provides important information regarding the links between biochemical decay and the chemical nature of organic matter removed and remaining in the soil profile.

Validation of a novel robot-assisted 3DUS system for real-time planning and guidance of breast interstitial HDR brachytherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Poulin, Eric; Beaulieu, Luc, E-mail: Luc.Beaulieu@phy.ulaval.ca; Gardi, Lori

Purpose: In current clinical practice, there is no integrated 3D ultrasound (3DUS) guidance system clinically available for breast brachytherapy. In this study, the authors present a novel robot-assisted 3DUS system for real-time planning and guidance of breast interstitial high dose rate (HDR) brachytherapy treatment. Methods: For this work, a new computer controlled robotic 3DUS system was built to perform a hybrid motion scan, which is a combination of a 6 cm linear translation with a 30° rotation at both ends. The new 3DUS scanner was designed to fit on a modified Kuske assembly, keeping the current template grid configuration butmore » modifying the frame to allow the mounting of the 3DUS system at several positions. A finer grid was also tested. A user interface was developed to perform image reconstruction, semiautomatic segmentation of the surgical bed as well as catheter reconstruction and tracking. A 3D string phantom was used to validate the geometric accuracy of the reconstruction. The volumetric accuracy of the system was validated with phantoms using magnetic resonance imaging (MRI) and computed tomography (CT) images. In order to accurately determine whether 3DUS can effectively replace CT for treatment planning, the authors have compared the 3DUS catheter reconstruction to the one obtained from CT images. In addition, in agarose-based phantoms, an end-to-end procedure was performed by executing six independent complete procedures with both 14 and 16 catheters, and for both standard and finer Kuske grids. Finally, in phantoms, five end-to-end procedures were performed with the final CT planning for the validation of 3DUS preplanning. Results: The 3DUS acquisition time is approximately 10 s. A paired Student t-test showed that there was no statistical significant difference between known and measured values of string separations in each direction. Both MRI and CT volume measurements were not statistically different from 3DUS volume (Student t-test: p > 0.05) and they were significantly correlated to 3DUS measurement (Pearson test: MRI p < 0.05 and CT p < 0.001). The mean angular separation distance between catheter trajectories segmented from 3DUS and CT images was 0.42° ± 0.24°, while the maximum and mean trajectory separations were 0.51 ± 0.19 and 0.37 ± 0.17 mm, respectively. Overall, the new finer grid has performed significantly better in terms of dosimetric indices. The planning target volume dosimetric indices were not found statistically different between 3DUS and CT planning (Student t-test, p > 0.05). Both the skin and the pectoral muscle dosimetric indices were within ABS guidelines. Conclusions: A novel robot-assisted 3DUS system was designed and validated. To their knowledge, this is the first system capable of performing real-time guidance and planning of breast multicatheter HDR brachytherapy treatments. Future investigation will test the feasibility of using the system in the clinic and for permanent breast brachytherapy.« less

Comparative analysis of peroxidase profiles in Chinese kale (Brassica alboglabra L.): evaluation of leaf growth related isozymes.

PubMed

Tang, Lei; Wang, Chenchen; Huang, Jiabao; Zhang, Jianhua; Mao, Zhonggui; Wang, Haiou

2013-01-15

Plant peroxidases (EC 1.11.1.7) with different isoforms catalyze various reactions in plant growth and development. However, it is difficult to elucidate the function of each isozyme in one plant. Here, we compared profiles of entire isozyme in young seedling and mature leaves of Chinese kale (Brassica alboglabra L.) on zymogram and ion exchange chromatography in order to investigate leaf growth related peroxidase isozymes. The results showed that four isozymes were constitutively expressed in kale leaves, whereas other two isozymes were induced in the mature leaves. The Mono Q ion exchange chromatography separated the six isozymes into two major groups due to the difference in their isoelectric points. The results suggested that although there were several isozymes in the leaves of Chinese kale, one isozyme functioned mainly through the leaf development. Two anionic isozymes with molecular weights lower than 32 kDa were considered mature related. Copyright © 2012 Elsevier Ltd. All rights reserved.

Characterization anatomical leaf blade five species Nepenthes from Kerinci Seblat National Park, Kerinci regency, Jambi Province

NASA Astrophysics Data System (ADS)

Al Farishy, D. D.; Nisyawati, Metusala, D.

2017-07-01

Nepenthes is one of carnivorous plant genera which have key characters on leaf and pitcher as the modification. However, wide varieties of morphological features on pitcher intraspecies and between species could be tough for identification process. The objective was to provide alternative characters for identification process by anatomical features. Kerinci Seblat National Park was chosen because lack of update data on wild type of species there. Whole five species were collected at Lingkat Lake and Gunung Tujuh Lake as representative lowland and highland species. Leaves collected fresh, flawless, and has grown pitcher. Each leaf was separated into the paradermal and transversal section, dehydrated by series alcohol, and stained by safranin and fast green. Sections observed by light microscope. Result show there were specific differences between species that could be potential to be key characters. That features are stomatal density, stomatal length, sessile glands surface shaped, sessile glands density, trichome distribution, adaxial cuticle thickness, adaxial hypodermic thickness, and the number of layers of adaxial hypodermis

Effects of high salinity from desalination brine on growth, photosynthesis, water relations and osmolyte concentrations of seagrass Posidonia australis.

PubMed

Cambridge, M L; Zavala-Perez, A; Cawthray, G R; Mondon, J; Kendrick, G A

2017-02-15

Highly saline brines from desalination plants expose seagrass communities to salt stress. We examined effects of raised salinity (46 and 54psu) compared with seawater controls (37psu) over 6weeks on the seagrass, Posidonia australis, growing in tanks with the aim of separating effects of salinity from other potentially deleterious components of brine and determining appropriate bioindicators. Plants survived exposures of 2-4weeks at 54psu, the maximum salinity of brine released from a nearby desalination plant. Salinity significantly reduced maximum quantum yield of PSII (chlorophyll a fluorescence emissions). Leaf water potential (Ψ w ) and osmotic potential (Ψ π ) were more negative at increased salinity, while turgor pressure (Ψ p ) was unaffected. Leaf concentrations of K + and Ca 2+ decreased, whereas concentrations of sugars (mainly sucrose) and amino acids increased. We recommend leaf osmolarity, ion, sugar and amino acid concentrations as bioindicators for salinity effects, associated with brine released in desalination plant outfalls. Copyright © 2016 Elsevier Ltd. All rights reserved.

Leaf water stress detection utilizing thematic mapper bands 3, 4 and 5 in soybean plants

NASA Technical Reports Server (NTRS)

Holben, B. N.; Schutt, J. B.; Mcmurtrey, J., III

1983-01-01

The total and diffuse radiance responses of Thematic Mapper bands 3 (0.63-0.69 microns), 4 (0.76-0.90 microns), and 5 (1.55-1.75 microns) to water stress in a soybean canopy are compared. Polarization measurements were used to separate the total from the diffuse reflectance; the reflectances were compared statistically at a variety of look angles at 15 min intervals from about 09.00 until 14.00 hrs EST. The results suggest that remotely sensed data collected in the photographic infrared region (TM4) are sensitive to leaf water stress in a 100 percent canopy cover of soybeans, and that TM3 is less sensitive than TM4 for detection of reversible foliar water stress. The mean values of TM5 reflectance data show similar trends to TM4. The primary implication of this study is that remote sensing of water stress in green plant canopies is possible in TM4 from ground-based observations primarily through the indirect link of leaf geometry.

Gamma dosimetric parameters in some skeletal muscle relaxants

NASA Astrophysics Data System (ADS)

Manjunatha, H. C.

2017-09-01

We have studied the attenuation of gamma radiation of energy ranging from 84 keV to 1330 keV (^{170}Tm, ^{22}Na,^{137}Cs, and ^{60}Co) in some commonly used skeletal muscle relaxants such as tubocurarine chloride, gallamine triethiodide, pancuronium bromide, suxamethonium bromide and mephenesin. The mass attenuation coefficient is measured from the attenuation experiment. In the present work, we have also proposed the direct relation between mass attenuation coefficient (μ /ρ ) and mass energy absorption coefficient (μ _{en}/ρ ) based on the nonlinear fitting procedure. The gamma dosimetric parameters such as mass energy absorption coefficient (μ _{en}/ρ ), effective atomic number (Z_{eff}), effective electron density (N_{el}), specific γ-ray constant, air kerma strength and dose rate are evaluated from the measured mass attentuation coefficient. These measured gamma dosimetric parameters are compared with the theoretical values. The measured values agree with the theoretical values. The studied gamma dosimetric values for the relaxants are useful in medical physics and radiation medicine.

SU-G-TeP3-11: Radiobiological-Cum-Dosimetric Quality Assurance of Complex Radiotherapy Plans

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paudel, N; Narayanasamy, G; Zhang, X

2016-06-15

Purpose: Dosimetric gamma-analysis used for QA of complex radiotherapy plans tests the dosimetric equivalence of a delivered plan with the treatment planning system (TPS) optimized plan. It does not examine whether a dosimetric difference results in any radiobiological difference. This study introduces a method to test the radiobiological and dosimetric equivalence between a delivered and the TPS optimized plan. Methods: Six head and neck and seven lung cancer VMAT or IMRT plans optimized for patient treatment were calculated and delivered to an ArcCheck phantom. ArcCheck measured dose distributions were compared with the TPS calculated dose distributions using a 2-D gamma-analysis.more » Dose volume histograms (DVHs) for various patient structures were obtained by using measured data in 3DVH software and compared against the TPS calculated DVHs using 3-D gamma analysis. DVH data were used in the Poisson model to calculate tumor control probability (TCP) for the treatment targets and in the sigmoid dose response model to calculate normal tissue complication probability (NTCP) for the normal structures. Results: Two-D and three-D gamma passing rates among six H&N patient plans differed by 0 to 2.7% and among seven lung plans by 0.1 to 4.5%. Average ± SD TCPs based on measurement and TPS were 0.665±0.018 and 0.674±0.044 for H&N, and 0.791±0.027 and 0.733±0.031 for lung plans, respectively. Differences in NTCPs were usually negligible. The differences in dosimetric results, TCPs and NTCPs were insignificant. Conclusion: The 2-D and 3-D gamma-analysis based agreement between measured and planned dose distributions may indicate their dosimetric equivalence. Small and insignificant differences in TCPs and NTCPs based on measured and planned dose distributions indicate the radiobiological equivalence between the measured and optimized plans. However, patient plans showing larger differences between 2-D and 3-D gamma-analysis can help us make a more definite conclusion through our ongoing research with a larger number of patients.« less

SU-F-T-460: Dosimetric Matching Between Trilogy Tx and TrueBeam STx

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choi, Y; Kwak, J; Jeong, C

Purpose: To compare the commissioned beam data for one flattening filter photon mode (6 MV) and two flattening filter-free (FFF) photon modes (6 and 10 MV-FFF) between Trilogy Tx and TrueBeam STx and evaluate the possibility of dosimetric matching Methods: Dosimetric characteristics of the new Trilogy Tx including percent depth doses (PDDs), profiles, and output factors were measured for commissioning. Linear diode array detector and ion chambers were used to measure dosimetric data. The depth of dose maximum (dmax) and PDD at 10 cm (PDD10) were evaluated: 3×3 cm{sup 2}, 10×10 cm{sup 2}, and 40×40 cm{sup 2}. The beam profilesmore » were compared and then penumbras were evaluated. As a further test of the dosimetric matching, the same VMAT plans were delivered, measured with film, and compared with TPS calculation. Results: All the measured PDDs matched well across the two units. PDD10 showed less than 0.5% variation and dmax were within 1.5 mm at the field sizes evaluated. Within the central 80% of transverse axis, profile data were almost identical. TrueBeam data resulted in a slightly greater penumbra width (up to 1.9 mm). The greatest differences of output factors were found at 40 × 40 cm{sup 2}: 2.40%, 2.03%, and 2.22% for 6 MV, 6 MV-FFF, and 10 MV-FFF, respectively. For smaller field sizes, less than 1% differences were observed. The film measurements demonstrated over 97.3% pixels passing-gamma analysis (2%/2mm). The results showed excellent agreement between measurements of two machines. Conclusion: The differences between Trilogy Tx and TrueBeam STx found could possibly affect small field and also very large field sizes in dosimetric matching considerations. These differences encountered are mostly related with the changes in the head design of the TrueBeam. Although it cannot guarantee full interchangeability of two machines, dosimetric matching by field size of 25 × 25 cm{sup 2} might be clinically acceptable.« less

First report of natural occurrence of Turnip vein-clearing virus in garlic mustard (Alliaria petiolata) in the United States

USDA-ARS?s Scientific Manuscript database

During 2011-2013 plants of the invasive weed species Alliaria petiolata (garlic mustard) were observed with virus-like disease symptoms in three separate locations in Ramsey and Anoka counties, Minnesota. Symptoms consisted of conspicuous mosaic, leaf deformation and stunting. Numerous virus-like pa...

Numerical and Experimental study of secondary flows in a rotating two-phase flow: the tea leaf paradox

NASA Astrophysics Data System (ADS)

Calderer, Antoni; Neal, Douglas; Prevost, Richard; Mayrhofer, Arno; Lawrenz, Alan; Foss, John; Sotiropoulos, Fotis

2015-11-01

Secondary flows in a rotating flow in a cylinder, resulting in the so called ``tea leaf paradox'', are fundamental for understanding atmospheric pressure systems, developing techniques for separating red blood cells from the plasma, and even separating coagulated trub in the beer brewing process. We seek to gain deeper insights in this phenomenon by integrating numerical simulations and experiments. We employ the Curvilinear Immersed boundary method (CURVIB) of Calderer et al. (J. Comp. Physics 2014), which is a two-phase flow solver based on the level set method, to simulate rotating free-surface flow in a cylinder partially filled with water as in the tea leave paradox flow. We first demonstrate the validity of the numerical model by simulating a cylinder with a rotating base filled with a single fluid, obtaining results in excellent agreement with available experimental data. Then, we present results for the cylinder case with free surface, investigate the complex formation of secondary flow patterns, and show comparisons with new experimental data for this flow obtained by Lavision. Computational resources were provided by the Minnesota Supercomputing Institute.

Effect of dilute alkaline pretreatment on the conversion of different parts of corn stalk to fermentable sugars and its application in acetone-butanol-ethanol fermentation.

PubMed

Cai, Di; Li, Ping; Luo, Zhangfeng; Qin, Peiyong; Chen, Changjing; Wang, Yong; Wang, Zheng; Tan, Tianwei

2016-07-01

To investigate the effect of dilute alkaline pretreatment on different parts of biomass, corn stalk was separated into flower, leaf, cob, husk and stem, which were treated by NaOH in range of temperature and chemical loading. The NaOH-pretreated solid was then enzymatic hydrolysis and used as the substrate for batch acetone-butanol-ethanol (ABE) fermentation. The results demonstrated the five parts of corn stalk could be used as potential feedstock separately, with vivid performances in solvents production. Under the optimized conditions towards high product titer, 7.5g/L, 7.6g/L, 9.4g/L, 7g/L and 7.6g/L of butanol was obtained in the fermentation broth of flower, leaf, cob, husk and stem hydrolysate, respectively. Under the optimized conditions towards high product yield, 143.7g/kg, 126.3g/kg, 169.1g/kg, 107.7g/kg and 116.4g/kg of ABE solvent were generated, respectively. Copyright © 2016 Elsevier Ltd. All rights reserved.

Comparative Analysis of Different Measurement Techniques for MLC Characterization: Preliminary Results

DOE Office of Scientific and Technical Information (OSTI.GOV)

Larraga-Gutierrez, J. M.; Ballesteros-Zebadua, P.; Garcia-Garduno, O. A.

2008-08-11

Radiation transmission, leakage and beam penumbra are essential dosimetric parameters related to the commissioning of a multileaf collimation system. This work shows a comparative analysis of commonly used film detectors: X-OMAT V2 and EDR2 radiographic films, and GafChromic EBT registered radiochromic film. The results show that X-OMAT over-estimates radiation leakage and 80-20% beam penumbra. However, according to the reference values reported by the manufacturer for these dosimetric parameters, all three films are adequate for MLC dosimetric characterization, but special care must be taken when X-OMAT V2 film is used due to its low energy photon dependence.

[Latitudinal Changes in Plant Stoichiometric and Soil C, N, P Stoichiometry in Loess Plateau].

PubMed

Li, Ting; Deng, Qiang; Yuan, Zhi-you; Jiao, Feng

2015-08-01

Field investigations and sampling were conducted in Loess Plateau, including Fu County, Ganquan County, Ansai County, Jingbian County and Hengshan County and Yuyang District. Our objective was to examine changes of leaf and soil stoichiometry characteristics along latitudinal gradient in Loess Plateau, and to provide references for the prediction of soil nutrient status of the ecosystem and constraints of plant nutrition elements in Loess Plateau. The results showed that (1) Across the 35.95 degrees-38.36 degrees N latitude gradient, leaf C, N and P stoichiometry were ranging from 336.95 to 477.38 mg x g(-1) for C, from 18.09 to 33.173 mg x g(-1) for N and from 1.07 to 1.73 mg x g(-1) for P, the arithmetic means were 442.9 mg x g(-1), 25.79 mg x g(-1) and 1.37 mg x g(-1), separately, the variation coefficients were 11.9%, 17.4% and 13.3%. There were obvious correlation between leaf C, N, P and latitude, leaf C, C : N ratio and C: P ratio significantly decreased with the increasing latitude, while leaf N and P significantly increased with the increasing latitude. The relationship between N: P ratio and latitude was not significant. (2) The content of soil organic C and soil total N decreased with increasing latitude and soil layer. In contrast, with the increase of latitude, soil P increased and then decreased. In the 0-10 cm, 10-20 cm soil layers, soil C: N ratio did not change significantly with latitude, while in the 20-40 cm layer, C: N ratio decreased obviously, but soil C: P and N: P ratios decreased with the increasing latitude in all soil layers. (3) Leaf C, C: N and C: P ratios were correlated to soil organic C, soil total N and soil total P in all soil layers, leaf N and P were correlated to soil organic C and soil total N, while leaf N: P ratio was not correlated to soil organic C, soil total N and soil total P. There was a certain correlation between the leaf C, N, P and latitude, however, the correlations between leaf and soil C, N, P were inconsistent. These results demonstrate that the plants were under P limitation in Loess Plateau.

Separate loci underlie resistance to root infection and leaf scorch during soybean sudden death syndrome.

PubMed

Kazi, S; Shultz, J; Afzal, J; Johnson, J; Njiti, V N; Lightfoot, D A

2008-05-01

Soybean [Glycine max (L.) Merr.] cultivars show differences in their resistance to both the leaf scorch and root rot of sudden death syndrome (SDS). The syndrome is caused by root colonization by Fusarium virguliforme (ex. F. solani f. sp. glycines). Root susceptibility combined with reduced leaf scorch resistance has been associated with resistance to Heterodera glycines HG Type 1.3.6.7 (race 14) of the soybean cyst nematode (SCN). In contrast, the rhg1 locus underlying resistance to Hg Type 0 was found clustered with three loci for resistance to SDS leaf scorch and one for root infection. The aims of this study were to compare the inheritance of resistance to leaf scorch and root infection in a population that segregated for resistance to SCN and to identify the underlying quantitative trait loci (QTL). "Hartwig", a cultivar partially resistant to SDS leaf scorch, F. virguliforme root infection and SCN HG Type 1.3.6.7 was crossed with the partially susceptible cultivar "Flyer". Ninety-two F5-derived recombinant inbred lines and 144 markers were used for map development. Four QTL found in earlier studies were confirmed. One contributed resistance to leaf scorch on linkage group (LG) C2 (Satt277; P = 0.004, R2 = 15%). Two on LG G underlay root infection at R8 (Satt038; P = 0.0001 R2 = 28.1%; Satt115; P = 0.003, R2 = 12.9%). The marker Satt038 was linked to rhg1 underlying resistance to SCN Hg Type 0. The fourth QTL was on LG D2 underlying resistance to root infection at R6 (Satt574; P = 0.001, R2 = 10%). That QTL was in an interval previously associated with resistance to both SDS leaf scorch and SCN Hg Type 1.3.6.7. The QTL showed repulsion linkage with resistance to SCN that may explain the relative susceptibility to SDS of some SCN resistant cultivars. One additional QTL was discovered on LG G underlying resistance to SDS leaf scorch measured by disease index (Satt130; P = 0.003, R2 = 13%). The loci and markers will provide tagged alleles with which to improve the breeding of cultivars combining resistances to SDS leaf scorch, root infection and SCN HG Type 1.3.6.7.

Inclusion of dosimetric data as covariates in toxicity-related radiogenomic studies : A systematic review.

PubMed

Yahya, Noorazrul; Chua, Xin-Jane; Manan, Hanani A; Ismail, Fuad

2018-05-17

This systematic review evaluates the completeness of dosimetric features and their inclusion as covariates in genetic-toxicity association studies. Original research studies associating genetic features and normal tissue complications following radiotherapy were identified from PubMed. The use of dosimetric data was determined by mining the statement of prescription dose, dose fractionation, target volume selection or arrangement and dose distribution. The consideration of the dosimetric data as covariates was based on the statement mentioned in the statistical analysis section. The significance of these covariates was extracted from the results section. Descriptive analyses were performed to determine their completeness and inclusion as covariates. A total of 174 studies were found to satisfy the inclusion criteria. Studies published ≥2010 showed increased use of dose distribution information (p = 0.07). 33% of studies did not include any dose features in the analysis of gene-toxicity associations. Only 29% included dose distribution features as covariates and reported the results. 59% of studies which included dose distribution features found significant associations to toxicity. A large proportion of studies on the correlation of genetic markers with radiotherapy-related side effects considered no dosimetric parameters. Significance of dose distribution features was found in more than half of the studies including these features, emphasizing their importance. Completeness of radiation-specific clinical data may have increased in recent years which may improve gene-toxicity association studies.

Arctic Climate during Eocene Hyperthermals: Wet Summers on Ellesmere Island?

NASA Astrophysics Data System (ADS)

Greenwood, D. R.; West, C. K.; Basinger, J. F.

2012-12-01

Previous work has shown that during the late Paleocene to middle Eocene, mesothermal conditions (i.e., MAT ~12-15° C) and high precipitation (MAP > 150cm/yr) characterized Arctic climates - an Arctic rain forest. Recent analyses of Arctic Eocene wood stable isotope chemistry are consistent with the annual and seasonal temperature estimates from leaf physiognomy and nearest living relative analogy from fossil plants, including the lack of freezing winters, but is interpreted as showing that there was a summer peak in precipitation - modern analogs are best sought on the summer-wet east coasts (e.g., China, Japan, South Korea) not the winter-wet west coasts of present-day northern temperate continents (e.g., Pacific northwest of North America). Highly seasonal 'monsoon-type' summer-wet precipitation regimes (i.e., summer precip./winter precip. > 3.0) seem to characterize Eocene hyperthermal conditions in several regions of the earth, including the Arctic and Antarctic, based on both climate model sensitivity experiments and the paleoclimate proxy evidence. The leaf physiognomy proxy previously applied to estimate Arctic Paleogene precipitation was leaf area analysis (LAA), a correlation between mean leaf size in woody dicot vegetation and annual precipitation. New data from modern monsoonal sites, however demonstrates that for deciduous-dicot dominated vegetation, summer precipitation determines mean leaf size, not annual totals, and therefore that under markedly seasonal precipitation and/or light regimes that summer precipitation is being estimated using LAA. Presented here is a new analysis of a leaf macrofloras from 3 separate florules of the Margaret Formation (Split Lake, Stenkul Fiord and Strathcona Fiord) from Ellesmere Island that are placed stratigraphically as early Eocene, and likely fall within Eocene thermal maximum 1 (ETM1; = the 'PETM') or ETM2. These floras are each characterized by a mix of large-leafed and small-leafed dicot taxa, with overall mean leaf size across all leaf morphotypes comparable to that previously reported for late Paleocene to middle Eocene floras from Ellesmere and Axel Heiberg islands of Nunavut. Applying the conventional leaf area analysis to the putatively ETM1 floras yielded estimates of mean annual precipitation 100-200cm/yr, consistent with the previous reports for the late Paleocene to middle Eocene. CLAMP analysis applied to these floras yields growing season precipitation comparable to the annual precipitation estimate from leaf area analysis. These data are interpreted as reflecting high summer precipitation in the Arctic during the late Paleocene to middle Eocene, including ETM1, as precipitation in the dark polar winter months will have had no effect on leaf size while the trees were dormant, corroborating the results from Eocene wood chemistry. High summer precipitation (i.e., light-season = wettest season) in the Eocene Arctic during hyperthermals would have contributed to regional warmth.

Effects of foliage clumping on the estimation of global terrestrial gross primary productivity

NASA Astrophysics Data System (ADS)

Chen, Jing M.; Mo, Gang; Pisek, Jan; Liu, Jane; Deng, Feng; Ishizawa, Misa; Chan, Douglas

2012-03-01

Sunlit and shaded leaf separation proposed by Norman (1982) is an effective way to upscale from leaf to canopy in modeling vegetation photosynthesis. The Boreal Ecosystem Productivity Simulator (BEPS) makes use of this methodology, and has been shown to be reliable in modeling the gross primary productivity (GPP) derived from CO2flux and tree ring measurements. In this study, we use BEPS to investigate the effect of canopy architecture on the global distribution of GPP. For this purpose, we use not only leaf area index (LAI) but also the first ever global map of the foliage clumping index derived from the multiangle satellite sensor POLDER at 6 km resolution. The clumping index, which characterizes the degree of the deviation of 3-dimensional leaf spatial distributions from the random case, is used to separate sunlit and shaded LAI values for a given LAI. Our model results show that global GPP in 2003 was 132 ± 22 Pg C. Relative to this baseline case, our results also show: (1) global GPP is overestimated by 12% when accurate LAI is available but clumping is ignored, and (2) global GPP is underestimated by 9% when the effective LAI is available and clumping is ignored. The clumping effects in both cases are statistically significant (p < 0.001). The effective LAI is often derived from remote sensing by inverting the measured canopy gap fraction to LAI without considering the clumping. Global GPP would therefore be generally underestimated when remotely sensed LAI (actually effective LAI by our definition) is used. This is due to the underestimation of the shaded LAI and therefore the contribution of shaded leaves to GPP. We found that shaded leaves contribute 50%, 38%, 37%, 39%, 26%, 29% and 21% to the total GPP for broadleaf evergreen forest, broadleaf deciduous forest, evergreen conifer forest, deciduous conifer forest, shrub, C4 vegetation, and other vegetation, respectively. The global average of this ratio is 35%.

Age- and size-related changes in physiological characteristics and chemical composition of Acer pseudoplatanus and Fraxinus excelsior trees.

PubMed

Abdul-Hamid, Hazandy; Mencuccini, Maurizio

2009-01-01

Forest growth is an important factor both economically and ecologically, and it follows a predictable trend with age. Generally, growth accelerates as canopies develop in young forests and declines substantially soon after maximum leaf area is attained. The causes of this decline are multiple and may be linked to age- or size-related processes, or both. Our objective was to determine the relative effects of tree age and tree size on the physiological attributes of two broadleaf species. As age and size are normally coupled during growth, an approach based on grafting techniques to separate the effects of size from those of age was adopted. Genetically identical grafted seedlings were produced from scions taken from trees of four age classes, ranging from 4 to 162 years. We found that leaf-level net photosynthetic rate per unit of leaf mass and some other leaf structural and biochemical characteristics had decreased substantially with increasing size of the donor trees in the field, whereas other gas exchange parameters expressed on a leaf area basis did not. In contrast, these parameters remained almost constant in grafted seedlings, i.e., scions taken from donor trees with different meristematic ages show no age-related trend after they were grafted onto young rootstocks. In general, the results suggested that size-related limitations triggered the declines in photosynthate production and tree growth, whereas less evidence was found to support a role of meristematic age.

Application of an online post-column derivatization HPLC-DPPH assay to detect compounds responsible for antioxidant activity in Sonchus oleraceus L. leaf extracts.

PubMed

Ou, Zong-Quan; Schmierer, David M; Rades, Thomas; Larsen, Lesley; McDowell, Arlene

2013-02-01

To use an online assay to identify key antioxidants in Sonchus oleraceus leaf extracts and to investigate the effect of leaf position and extraction conditions on antioxidant concentration and activity. Separation of phytochemicals and simultaneous assessment of antioxidant activity were performed online using HPLC and post-column reaction with a free-radical reagent (2, 2-diphenylpicrylhydrazyl, DPPH). Active compounds were identified using nuclear magnetic resonance spectroscopy and mass spectrometry. We applied the online HPLC-DPPH radical assay to evaluate antioxidants in leaves from different positions on the plant and to assess the effect of pre-treatment of leaves with liquid N(2) before grinding, extraction time, extraction temperature and method of concentrating extracts. Key antioxidants identified in S. oleraceus leaf extracts were caftaric acid, chlorogenic acid and chicoric acid. Middle leaves contained the highest total amount of the three key antioxidant compounds, consisting mainly of chicoric acid. Pre-treatment with liquid N(2), increasing the extraction temperature and time and freeze-drying the extract did not enhance the yield of the key antioxidants. The online HPLC-DPPH radical assay was validated as a useful screening tool for investigating individual antioxidants in leaf extracts. Optimized extraction conditions were middle leaves pre-treated with liquid N(2), extraction at 25°C for 0.5 h and solvent removal by rotary evaporation. © 2012 The Authors. JPP © 2012. Royal Pharmaceutical Society.

A novel method of measuring leaf epidermis and mesophyll stiffness shows the ubiquitous nature of the sandwich structure of leaf laminas in broad-leaved angiosperm species.

PubMed

Onoda, Yusuke; Schieving, Feike; Anten, Niels P R

2015-05-01

Plant leaves commonly exhibit a thin, flat structure that facilitates a high light interception per unit mass, but may increase risks of mechanical failure when subjected to gravity, wind and herbivory as well as other stresses. Leaf laminas are composed of thin epidermis layers and thicker intervening mesophyll layers, which resemble a composite material, i.e. sandwich structure, used in engineering constructions (e.g. airplane wings) where high bending stiffness with minimum weight is important. Yet, to what extent leaf laminas are mechanically designed and behave as a sandwich structure remains unclear. To resolve this issue, we developed and applied a novel method to estimate stiffness of epidermis- and mesophyll layers without separating the layers. Across a phylogenetically diverse range of 36 angiosperm species, the estimated Young's moduli (a measure of stiffness) of mesophyll layers were much lower than those of the epidermis layers, indicating that leaf laminas behaved similarly to efficient sandwich structures. The stiffness of epidermis layers was higher in evergreen species than in deciduous species, and strongly associated with cuticle thickness. The ubiquitous nature of sandwich structures in leaves across studied species suggests that the sandwich structure has evolutionary advantages as it enables leaves to be simultaneously thin and flat, efficiently capturing light and maintaining mechanical stability under various stresses. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Global Transcriptional Analysis Reveals the Complex Relationship between Tea Quality, Leaf Senescence and the Responses to Cold-Drought Combined Stress in Camellia sinensis

PubMed Central

Zheng, Chao; Wang, Yu; Ding, Zhaotang; Zhao, Lei

2016-01-01

In field conditions, especially in arid and semi-arid areas, tea plants are often simultaneously exposed to various abiotic stresses such as cold and drought, which have profound effects on leaf senescence process and tea quality. However, most studies of gene expression in stress responses focus on a single inciting agent, and the confounding effect of multiple stresses on crop quality and leaf senescence remain unearthed. Here, global transcriptome profiles of tea leaves under separately cold and drought stress were compared with their combination using RNA-Seq technology. This revealed that tea plants shared a large overlap in unigenes displayed “similar” (26%) expression pattern and avoid antagonistic responses (lowest level of “prioritized” mode: 0%) to exhibit very congruent responses to co-occurring cold and drought stress; 31.5% differential expressed genes and 38% of the transcriptome changes in response to combined stresses were unpredictable from cold or drought single-case studies. We also identified 319 candidate genes for enhancing plant resistance to combined stress. We then investigated the combined effect of cold and drought on tea quality and leaf senescence. Our results showed that drought-induced leaf senescence were severely delayed by (i) modulation of a number of senescence-associated genes and cold responsive genes, (ii) enhancement of antioxidant capacity, (iii) attenuation of lipid degradation, (iv) maintenance of cell wall and photosynthetic system, (v) alteration of senescence-induced sugar effect/sensitivity, as well as (vi) regulation of secondary metabolism pathways that significantly influence the quality of tea during combined stress. Therefore, care should be taken when utilizing a set of stresses to try and maximize leaf longevity and tea quality. PMID:28018394

Structure Measurements of Leaf and Woody Components of Forests with Dual-Wavelength Lidar Scanning Data

NASA Astrophysics Data System (ADS)

Strahler, A. H.; Li, Z.; Schaaf, C.; Howe, G.; Martel, J.; Hewawasam, K.; Douglas, E. S.; Chakrabarti, S.; Cook, T.; Paynter, I.; Saenz, E. J.; Wang, Z.; Woodcock, C. E.; Jupp, D. L. B.; Schaefer, M.; Newnham, G.

2014-12-01

Forest structure plays a critical role in the exchange of energy, carbon and water between land and atmosphere and nutrient cycle. We can provide detailed forest structure measurements of leaf and woody components with the Dual Wavelength Echidna® Lidar (DWEL), which acquires full-waveform scans at both near-infrared (NIR, 1064 nm) and shortwave infrared (SWIR, 1548 nm) wavelengths from simultaneous laser pulses. We collected DWEL scans at a broadleaf forest stand and a conifer forest stand at Harvard Forest in June 2014. Power returned from leaves is much lower than from woody materials such as trunks and branches at the SWIR wavelength due to the liquid water absorption by leaves, whereas returned power at the NIR wavelength is similar from both leaves and woody materials. We threshold a normalized difference index (NDI), defined as the difference between returned power at the two wavelengths divided by their sum, to classify each return pulse as a leaf or trunk/branch hit. We obtain leaf area index (LAI), woody area index (WAI) and vertical profiles of leaf and woody components directly from classified lidar hits without empirical wood-to-total ratios as are commonly used in optical methods of LAI estimation. Tree heights, diameter at breast height (DBH), and stem count density are the other forest structure parameters estimated from our DWEL scans. The separation of leaf and woody components in tandem with fine-scale forest structure measurements will benefit studies on carbon allocation of forest ecosystems and improve our understanding of the effects of forest structure on ecosystem functions. This research is supported by NSF grant, MRI-0923389

Reducing cell wall feruloylation by expression of a fungal ferulic acid esterase in Festuca arundinacea modifies plant growth, leaf morphology and the turnover of cell wall arabinoxylans

PubMed Central

Iyer, Prashanti R.; Buanafina, M. Fernanda; Shearer, Erica A.

2017-01-01

A feature of cell wall arabinoxylan in grasses is the presence of ferulic acid which upon oxidative coupling by the action of peroxidases forms diferuloyl bridges between formerly separated arabinoxylans. Ferulate cross-linking is suspected of playing various roles in different plant processes. Here we investigate the role of cell wall feruloyaltion in two major processes, that of leaf growth and the turnover of cell wall arabinoxylans on leaf senescence in tall fescue using plants in which the level of cell wall ferulates has been reduced by targeted expression of the Aspergillus niger ferulic acid esterase A (FAEA) to the apoplast or Golgi. Analysis of FAE expressing plants showed that all the lines had shorter and narrower leaves compared to control, which may be a consequence of the overall growth rate being lower and occurring earlier in FAE expressing leaves than in controls. Furthermore, the final length of epidermal cells was shorter than controls, indicating that their expansion was curtailed earlier than in control leaves. This may be due to the observations that the deposition of both ether and ester linked monomeric hydroxycinnamic acids and ferulate dimerization stopped earlier in FAE expressing leaves but at a lower level than controls, and hydroxycinnamic acid deposition started to slow down when peroxidase levels increased. It would appear therefore that one of the possible mechanisms for controlling overall leaf morphology such as leaf length and width in grasses, where leaf morphology is highly variable between species, may be the timing of hydroxycinnamic acid deposition in the expanding cell walls as they emerge from cell division into the elongation zone, controlled partially by the onset of peroxidase activity in this region. PMID:28934356

Cloning and characterization of a serotonin N-acetyltransferase from a gymnosperm, loblolly pine (Pinus taeda).

PubMed

Park, Sangkyu; Byeon, Yeong; Lee, Hyoung Yool; Kim, Young-Soon; Ahn, Taeho; Back, Kyoungwhan

2014-10-01

Serotonin N-acetyltransferase (SNAT) is the penultimate enzyme in melatonin biosynthesis in both animals and plants. SNAT catalyzes serotonin into N-acetylserotonin, an immediate precursor for melatonin biosynthesis by N-acetylserotonin methyltransferase (ASMT). We cloned the SNAT gene from a gymnosperm loblolly pine (Pinus teada). The loblolly pine SNAT (PtSNAT) gene encodes 255 amino acids harboring a transit sequence with 67 amino acids and shows 67% amino acid identity with rice SNAT when comparing the mature polypeptide regions. Purified recombinant PtSNAT showed peak activity at 55°C with the K(m) (428 μM) and Vmax (3.9 nmol/min/mg protein) values. As predicted, PtSNAT localized to chloroplasts. The SNAT mRNA was constitutively expressed in all tissues, including leaf, bud, flower, and pinecone, whereas the corresponding protein was detected only in leaf. In accordance with the exclusive SNAT protein expression in leaf, melatonin was detected only in leaf at 0.45 ng per gram fresh weight. Sequence and phylogenetic analysis indicated that the gymnosperm PtSNAT had high homology with SNATs from all plant phyla (even with cyanobacteria), and formed a clade separated from the angiosperm SNATs, suggestive of direct gene transfer from cyanobacteria via endosymbiosis. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Arabidopsis REGULATOR OF AXILLARY MERISTEMS1 controls a leaf axil stem cell niche and modulates vegetative development.

PubMed

Keller, Thomas; Abbott, Jessica; Moritz, Thomas; Doerner, Peter

2006-03-01

Shoot branching is a major determinant of variation in plant stature. Branches, which form secondary growth axes, originate from stem cells activated in leaf axils. The initial steps by which axillary meristems (AMs) are specified and their stem cells organized are still poorly understood. We identified gain- and loss-of-function alleles at the Arabidopsis thaliana REGULATOR OF AXILLARY MERISTEMS1 (RAX1) locus. RAX1 is encoded by the Myb-like transcription factor MYB37 and is an Arabidopsis homolog of the tomato (Solanum lycopersicum) Blind gene. RAX1 is transiently expressed in a small central domain within the boundary zone separating shoot apical meristem and leaf primordia early in leaf primordium development. RAX1 genetically interacts with CUP-SHAPED COTYLEDON (CUC) genes and is required for the expression of CUC2 in the RAX1 expression domain, suggesting that RAX1 acts through CUC2. We propose that RAX1 functions to positionally specify a stem cell niche for AM formation. RAX1 also affects the timing of developmental phase transitions by negatively regulating gibberellic acid levels in the shoot apex. RAX1 thus defines a novel activity that links the specification of AM formation with the modulation of the rate of progression through developmental phases.

A worldwide analysis of within-canopy variations in leaf structural, chemical and physiological traits across plant functional types

PubMed Central

Niinemets, Ülo; Keenan, Trevor F.; Hallik, Lea

2018-01-01

Summary Extensive within-canopy light gradients importantly affect photosynthetic productivity of leaves in different canopy positions and lead to light-dependent increases in foliage photosynthetic capacity per area (AA). However, the controls on AA variations by changes in underlying traits are poorly known. We constructed an unprecedented worldwide database including 831 within-canopy gradients with standardized light estimates for 304 species belonging to major vascular plant functional types, and analyzed within-canopy variations in 12 key foliage structural, chemical and physiological traits by quantitatively separating the contributions of different traits to photosynthetic acclimation. Although the light-dependent increase in AA is surprisingly similar in different plant functional types, they fundamentally differ in the share of the controls on AA by constituent traits. Species with high rates of canopy development and leaf turnover exhibiting highly dynamic light environments, actively change AA by nitrogen reallocation among and partitioning within leaves. In contrast, species with slow leaf turnover exhibit a passive AA acclimation response primarily determined by acclimation of leaf structure to growth light. This review emphasizes that different combinations of traits are responsible for within-canopy photosynthetic acclimation in different plant functional types and solves an old enigma of the role of mass- vs. area-based traits in vegetation acclimation. PMID:25318596

SU-E-J-165: Dosimetric Impact of Liver Rotations in Stereotactic Body Radiation Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pinnaduwage, D; Paulsson, A; Sudhyadhom, A

2015-06-15

Purpose: Often in liver stereotactic body radiotherapy a single fiducial is implanted near the tumor for image-guided treatment delivery. In such cases, rotational corrections are calculated based on the spine. This study quantifies rotational differences between the spine and liver, and investigates the corresponding dosimetric impact. Methods: Seven patients with 3 intrahepatic fiducials and 4DCT scans were identified. The planning CT was separately co-registered with 4 phases of the 4DCT (0%, 50%, 100% inhale and 50% exhale) by 1) rigid registration of the spine, and 2) point-based registration of the 3 fiducials. Rotation vectors were calculated for each registration. Translationalmore » differences in fiducial positions between the 2 registrations methods were investigated. Dosimetric impact due to liver rotations and deformations was assessed using critical structures delineated on the 4DCT phases. For dose comparisons, a single fiducial was translationally aligned following spine alignment to represent what is typically done in the clinic. Results: On average, differences between spine and liver rotations during the 0%, 50%, 100% inhale, and 50% exhale phases were 3.23°, 3.27°, 2.26° and 3.11° (pitch), 3.00°, 2.24°, 3.12° and 1.73° (roll), and 1.57°, 1.98°, 2.09° and 1.36° (yaw), respectively. The maximum difference in rotations was 12°, with differences of >3° seen in 14/28 (pitch), 10/28 (roll), and 6/28 (yaw) cases. Average fiducial displacements of 2.73 (craniocaudal), 1.04 (lateral) and 1.82 mm (vertical) were seen. Evaluating percent dose differences for 5 patients at the peaks of the respiratory cycle, the maximum dose to the duodenum, stomach, bowel and esophagus differed on average by 11.4%, 5.3%, 11.2% and 49.1% between the 2 registration methods. Conclusion: Lack of accounting for liver rotation during treatment might Result in clinically significant dose differences to critical structures. Both rotational and translational deviations should be considered in planning margins when using spine alignment for liver treatments.« less

Dosimetric Analysis of Organs at Risk During Expiratory Gating in Stereotactic Body Radiation Therapy for Pancreatic Cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taniguchi, Cullen M.; Murphy, James D.; Eclov, Neville

2013-03-15

Purpose: To determine how the respiratory phase impacts dose to normal organs during stereotactic body radiation therapy (SBRT) for pancreatic cancer. Methods and Materials: Eighteen consecutive patients with locally advanced, unresectable pancreatic adenocarcinoma treated with SBRT were included in this study. On the treatment planning 4-dimensional computed tomography (CT) scan, the planning target volume (PTV), defined as the gross tumor volume plus 3-mm margin, the duodenum, and the stomach were contoured on the end-expiration (CT{sub exp}) and end-inspiration (CT{sub insp}) phases for each patient. A separate treatment plan was constructed for both phases with the dose prescription of 33 Gymore » in 5 fractions with 95% coverage of the PTV by the 100% isodose line. The dose-volume histogram (DVH) endpoints, volume of duodenum that received 20 Gy (V{sub 20}), V{sub 25}, and V{sub 30} and maximum dose to 5 cc of contoured organ (D{sub 5cc}), D{sub 1cc}, and D{sub 0.1cc}, were evaluated. Results: Dosimetric parameters for the duodenum, including V{sub 25}, V{sub 30}, D{sub 1cc}, and D{sub 0.1cc} improved by planning on the CT{sub exp} compared to those on the CT{sub insp}. There was a statistically significant overlap of the PTV with the duodenum but not the stomach during the CT{sub insp} compared to the CT{sub exp} (0.38 ± 0.17 cc vs 0.01 ± 0.01 cc, P=.048). A larger expansion of the PTV, in accordance with a Danish phase 2 trial, showed even more overlapping volume of duodenum on the CT{sub insp} compared to that on the CT{sub exp} (5.5 ± 0.9 cc vs 3.0 ± 0.8 cc, P=.0003) but no statistical difference for any stomach dosimetric DVH parameter. Conclusions: Dose to the duodenum was higher when treating on the inspiratory than on the expiratory phase. These data suggest that expiratory gating may be preferable to inspiratory breath-hold and free breathing strategies for minimizing risk of toxicity.« less

TU-EF-304-04: A Heart Motion Model for Proton Scanned Beam Chest Radiotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

White, B; Kiely, J Blanco; Lin, L

Purpose: To model fast-moving heart surface motion as a function of cardiac-phase in order to compensate for the lack of cardiac-gating in evaluating accurate dose to coronary structures. Methods: Ten subjects were prospectively imaged with a breath-hold, cardiac-gated MRI protocol to determine heart surface motion. Radial and planar views of the heart were resampled into a 3-dimensional volume representing one heartbeat. A multi-resolution optical flow deformable image registration algorithm determined tissue displacement during the cardiac-cycle. The surface of the heart was modeled as a thin membrane comprised of voxels perpendicular to a pencil beam scanning (PBS) beam. The membrane’s out-of-planemore » spatial displacement was modeled as a harmonic function with Lame’s equations. Model accuracy was assessed with the root mean squared error (RMSE). The model was applied to a cohort of six chest wall irradiation patients with PBS plans generated on phase-sorted 4DCT. Respiratory motion was separated from the cardiac motion with a previously published technique. Volumetric dose painting was simulated and dose accumulated to validate plan robustness (target coverage variation accepted within 2%). Maximum and mean heart surface dose assessed the dosimetric impact of heart and coronary artery motion. Results: Average and maximum heart surface displacements were 2.54±0.35mm and 3.6mm from the end-diastole phase to the end-systole cardiac-phase respectively. An average RMSE of 0.11±0.04 showed the model to be accurate. Observed errors were greatest between the circumflex artery and mitral valve level of the heart anatomy. Heart surface displacements correspond to a 3.6±1.0% and 5.1±2.3% dosimetric impact on the maximum and mean heart surface DVH indicators respectively. Conclusion: Although heart surface motion parallel to beam’s direction was substantial, its maximum dosimetric impact was 5.1±2.3%. Since PBS delivers low doses to coronary structures relative to photon radiotherapy, it is unknown whether this variation would be clinically significant for late effects.« less

SU-G-TeP2-15: Feasibility Study of Fiber-Optic Cerenkov Radiation Sensors for in Vivo Measurement: Dosimetric Characterization and Clinical Application in Proton Beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lah, J; Son, J; Kim, G

Purpose: To evaluate the possibility of a fiber-optic Cerenkov radiation sensor (FCRS) for in vivo dose verification in proton therapy. Methods: The Cerenkov radiation due to the proton beam was measured using a homemade phantom, consisting of a plastic optical fiber (POF, PGSCD1001-13-E, Toray, Tokyo, Japan) connected to each channel of a multianode photomultiplier tube (MAPMT:H7546, Hamamatsu Photonics, Shizuoka, Japan). Data were acquired using a multi-anode photomultiplier tube with the NI-DAQ system (National Instruments Texas, USA). The real-time monitoring graphic user interface was programmed using Labview. The FCRS was analyzed for its dosimetrics characteristic in proton beam. To determine themore » accuracy of the FCRS in proton dose measurements, we compared the ionization chamber dose measurements using a water phantom. We investigated the feasibility of the FCRS for the measurement of dose distributions near the superficial region for proton plans with a varying separation between the target volume and the surface of 3 patients using a humanoid phantom. Results: The dose-response has good linearity. Dose-rate and energy dependence were found to be within 1%. Depth-dose distributions in non-modulated proton beams obtained with the FCRS was in good agreement with the depth-dose measurements from the ionization chamber. To evaluate the dosimetric accuracy of the FCRS, the difference of isocenter dose between the delivery dose calculated by the treatment planning system and that measured by the FCRS was within 3%. With in vivo dosimetry using the humanoid phantom, the calculated surface doses overestimated measurements by 4%–8% using FCRS. Conclusion: In previous study, our results indicate that the performance of the array-type FCRS was comparable to that of the currently used a multi-layer ion chamber system. In this study, we also believe that the fiber-optic Cerenkov radiation sensor has considerable potential for use with in vivo patient proton dosimetry.« less

Neutron spectrometry for radiation protection purposes

NASA Astrophysics Data System (ADS)

McDonald, J. C.; Siebert, B. R. L.; Alberts, W. G.

2002-01-01

Determination of the dose equivalent is required for radiation protection purposes, however such a determination is quite difficult for neutron radiation. In order to perform accurate dosimetric determinations, it is advantageous to acquire information about the neutron fluence spectrum in the workplace as well as the reference radiations used to calibrate dosimetric instruments. This information can then be used to select the appropriate dosimetric instrument, the optimum calibration condition or to establish correction factors that account for the differences in calibration and workplace conditions. For quite some time, neutron spectrometry has been used for these purposes. A brief review of the applications of spectrometers in radiation protection and some recommendations for further development are given here.

Effect of advance seedling size and vigor on survival after clearcutting

Treesearch

David A. Marquis

1982-01-01

In several separate experiments, it was found that survival of advance seedlings after clearcutting in Allegheny hardwood stands is a function of initial seedling size-larger seedlings survive best. Age, number of leaves, and leaf size also were important determinants of survival. In Allegheny hardwood stands, where advance regeneration is typically less than 1 foot in...

Effective atomic numbers and electron density of dosimetric material

PubMed Central

Kaginelli, S. B.; Rajeshwari, T.; Sharanabasappa; Kerur, B. R.; Kumar, Anil S.

2009-01-01

A novel method for determination of mass attenuation coefficient of x-rays employing NaI (Tl) detector system and radioactive sources is described.in this paper. A rigid geometry arrangement and gating of the spectrometer at FWHM position and selection of absorber foils are all done following detailed investigation, to minimize the effect of small angle scattering and multiple scattering on the mass attenuation coefficient, μ/ρ, value. Firstly, for standardization purposes the mass attenuation coefficients of elemental foils such as Aluminum, Copper, Molybdenum, Tantalum and Lead are measured and then, this method is utilized for dosimetric interested material (sulfates). The experimental mass attenuation coefficient values are compared with the theoretical values to find good agreement between the theory and experiment within one to two per cent. The effective atomic numbers of the biological substitute material are calculated by sum rule and from the graph. The electron density of dosimetric material is calculated using the effective atomic number. The study has discussed in detail the attenuation coefficient, effective atomic number and electron density of dosimetric material/biological substitutes. PMID:20098566

Dosimetric characteristics of Novalis Tx system with high definition multileaf collimator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang Zheng; Wang Zhiheng; Wu, Q. Jackie

A new Novalis Tx system equipped with a high definition multileaf collimator (HDMLC) recently became available to perform both image-guided radiosurgery and conventional radiotherapy. It is capable of delivering a highly conformal radiation dose with three energy modes: 6 MV photon energy, 15 MV photon energy, and 6 MV photon energy in a stereotactic radiosurgery mode with 1000 MU/min dose rate. Dosimetric characteristics of the new Novalis Tx treatment unit with the HDMLC are systematically measured for commissioning. A high resolution diode detector and miniion-chamber detector are used to measure dosimetric data for a range of field sizes from 4x4more » mm to 400x400 mm. The commissioned Novalis Tx system has passed the RPC stereotactic radiosurgery head phantom irradiation test. The Novalis Tx system not only expands its capabilities with three energy modes, but also achieves better beam conformity and sharer beam penumbra with HDMLC. Since there is little beam data information available for the new Novalis Tx system, we present in this work the dosimetric data of the new modality for reference and comparison.« less

Dosimetric characterization of a bi-directional micromultileaf collimator for stereotactic applications.

PubMed

Bucciolini, M; Russo, S; Banci Buonamici, F; Pini, S; Silli, P

2002-07-01

A 6 MV photon beam from Linac SL75-5 has been collimated with a new micromultileaf device that is able to shape the field in the two orthogonal directions with four banks of leaves. This is the first clinical installation of the collimator and in this paper the dosimetric characterization of the system is reported. The dosimetric parameters required by the treatment planning system used for the dose calculation in the patient are: tissue maximum ratios, output factors, transmission and leakage of the leaves, penumbra values. Ionization chambers, silicon diode, radiographic films, and LiF thermoluminescent dosimeters have been employed for measurements of absolute dose and beam dosimetric data. Measurements with different dosimeters supply results in reasonable agreement among them and consistent with data available in literature for other models of micromultileaf collimator; that permits the use of the measured parameters for clinical applications. The discrepancies between results obtained with the different detectors (around 2%) for the analyzed parameters can be considered an indication of the accuracy that can be reached by current stereotactic dosimetry.

Monte Carlo Determination of Dosimetric Parameters of a New (125)I Brachytherapy Source According to AAPM TG-43 (U1) Protocol.

PubMed

Baghani, Hamid Reza; Lohrabian, Vahid; Aghamiri, Mahmoud Reza; Robatjazi, Mostafa

2016-03-01

(125)I is one of the important sources frequently used in brachytherapy. Up to now, several different commercial models of this source type have been introduced to the clinical radiation oncology applications. Recently, a new source model, IrSeed-125, has been added to this list. The aim of the present study is to determine the dosimetric parameters of this new source model based on the recommendations of TG-43 (U1) protocol using Monte Carlo simulation. The dosimetric characteristics of Ir-125 including dose rate constant, radial dose function, 2D anisotropy function and 1D anisotropy function were determined inside liquid water using MCNPX code and compared to those of other commercially available iodine sources. The dose rate constant of this new source was found to be 0.983+0.015 cGyh-1U-1 that was in good agreement with the TLD measured data (0.965 cGyh-1U-1). The 1D anisotropy function at 3, 5, and 7 cm radial distances were obtained as 0.954, 0.953 and 0.959, respectively. The results of this study showed that the dosimetric characteristics of this new brachytherapy source are comparable with those of other commercially available sources. Furthermore, the simulated parameters were in accordance with the previously measured ones. Therefore, the Monte Carlo calculated dosimetric parameters could be employed to obtain the dose distribution around this new brachytherapy source based on TG-43 (U1) protocol.

Dosimetry in radiotherapy using a-Si EPIDs: Systems, methods, and applications focusing on 3D patient dose estimation

NASA Astrophysics Data System (ADS)

McCurdy, B. M. C.

2013-06-01

An overview is provided of the use of amorphous silicon electronic portal imaging devices (EPIDs) for dosimetric purposes in radiation therapy, focusing on 3D patient dose estimation. EPIDs were originally developed to provide on-treatment radiological imaging to assist with patient setup, but there has also been a natural interest in using them as dosimeters since they use the megavoltage therapy beam to form images. The current generation of clinically available EPID technology, amorphous-silicon (a-Si) flat panel imagers, possess many characteristics that make them much better suited to dosimetric applications than earlier EPID technologies. Features such as linearity with dose/dose rate, high spatial resolution, realtime capability, minimal optical glare, and digital operation combine with the convenience of a compact, retractable detector system directly mounted on the linear accelerator to provide a system that is well-suited to dosimetric applications. This review will discuss clinically available a-Si EPID systems, highlighting dosimetric characteristics and remaining limitations. Methods for using EPIDs in dosimetry applications will be discussed. Dosimetric applications using a-Si EPIDs to estimate three-dimensional dose in the patient during treatment will be overviewed. Clinics throughout the world are implementing increasingly complex treatments such as dynamic intensity modulated radiation therapy and volumetric modulated arc therapy, as well as specialized treatment techniques using large doses per fraction and short treatment courses (ie. hypofractionation and stereotactic radiosurgery). These factors drive the continued strong interest in using EPIDs as dosimeters for patient treatment verification.

Dosimetric and clinical predictors for radiation-induced esophageal injury.

PubMed

Ahn, Sung-Ja; Kahn, Daniel; Zhou, Sumin; Yu, Xiaoli; Hollis, Donna; Shafman, Timothy D; Marks, Lawrence B

2005-02-01

To evaluate the clinical and three-dimensional dosimetric parameters associated with esophageal injury after radiotherapy (RT) for non-small-cell lung cancer. The records of 254 patients treated for non-small-cell lung cancer between 1992 and 2001 were reviewed. A variety of metrics describing the esophageal dose were extracted. The Radiation Therapy Oncology Group toxicity criteria for grading of esophageal injury were used. The median follow-up time for all patients was 43 months (range, 0.5-120 months). Logistic regression analysis, contingency table analyses, and Fisher's exact tests were used for statistical analysis. Acute toxicity occurred in 199 (78%) of 254 patients. For acute toxicity of Grade 2 or worse, twice-daily RT, age, nodal stage of N2 or worse, and most dosimetric parameters were predictive. Late toxicity occurred in 17 (7%) of 238 patients. The median and maximal time to the onset of late toxicity was 5 and 40 months after RT, respectively. Late toxicity occurred in 2%, 3%, 17%, 26%, and 100% of patients with acute Grade 0, 1, 2, 3, and 4 toxicity, respectively. For late toxicity, the severity of acute toxicity was most predictive. A variety of dosimetric parameters are predictive of acute and late esophageal injury. A strong correlation between the dosimetric parameters prevented a comparison between the predictive abilities of these metrics. The presence of acute injury was the most predictive factor for the development of late injury. Additional studies to define better the predictors of RT-induced esophageal injury are needed.

Potential benefits of dosimetric VMAT tracking verified with 3D film measurements.

PubMed

Crijns, Wouter; Defraene, Gilles; Van Herck, Hans; Depuydt, Tom; Haustermans, Karin; Maes, Frederik; Van den Heuvel, Frank

2016-05-01

To evaluate three different plan adaptation strategies using 3D film-stack dose measurements of both focal boost and hypofractionated prostate VMAT treatments. The adaptation strategies (a couch shift, geometric tracking, and dosimetric tracking) were applied for three realistic intrafraction prostate motions. A focal boost (35 × 2.2 and 35 × 2.7 Gy) and a hypofractionated (5 × 7.25 Gy) prostate VMAT plan were created for a heterogeneous phantom that allows for internal prostate motion. For these plans geometric tracking and dosimetric tracking were evaluated by ionization chamber (IC) point dose measurements (zero-D) and measurements using a stack of EBT3 films (3D). The geometric tracking applied translations, rotations, and scaling of the MLC aperture in response to realistic prostate motions. The dosimetric tracking additionally corrected the monitor units to resolve variations due to difference in depth, tissue heterogeneity, and MLC-aperture. The tracking was based on the positions of four fiducial points only. The film measurements were compared to the gold standard (i.e., IC measurements) and the planned dose distribution. Additionally, the 3D measurements were converted to dose volume histograms, tumor control probability, and normal tissue complication probability parameters (DVH/TCP/NTCP) as a direct estimate of clinical relevance of the proposed tracking. Compared to the planned dose distribution, measurements without prostate motion and tracking showed already a reduced homogeneity of the dose distribution. Adding prostate motion further blurs the DVHs for all treatment approaches. The clinical practice (no tracking) delivered the dose distribution inside the PTV but off target (CTV), resulting in boost dose errors up to 10%. The geometric and dosimetric tracking corrected the dose distribution's position. Moreover, the dosimetric tracking could achieve the planned boost DVH, but not the DVH of the more homogeneously irradiated prostate. A drawback of both the geometric and dosimetric tracking was a reduced MLC blocking caused by the rotational component of the MLC aperture corrections. Because of the used CTV to PTV margins and the high doses in the considered fractionation schemes, the TCP differed less than 0.02 from the planned value for all targets and all correction methods. The rectal NTCP constraints, however, could not be realized using any of these methods. The geometric and dosimetric tracking use only a limited input, but they deposit the dose distribution with higher geometric accuracy than the clinical practice. The latter case has boost dose errors up to 10%. The increased accuracy has a modest impact [Δ(NT)CP < 0.02] because of the applied margins and the high dose levels used. To allow further margin reduction tracking methods are vital. The proposed methodology could further be improved by implementing a rotational correction using collimator rotations.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mutaf, Yildirim D.; Yi, Byong Yong; Prado, Karl

Purpose: A dedicated stereotactic gamma irradiation device, the GammaPod Trade-Mark-Sign from Xcision Medical Systems, was developed specifically to treat small breast cancers. This study presents the first evaluation of dosimetric and geometric characteristics from the initial prototype installed at University of Maryland Radiation Oncology Department. Methods: The GammaPod Trade-Mark-Sign stereotactic radiotherapy device is an assembly of a hemi-spherical source carrier containing 36 {sup 60}Co sources, a tungsten collimator, a dynamically controlled patient support table, and the breast immobilization system which also functions as a stereotactic frame. The source carrier contains the sources in six columns spaced longitudinally at 60 Degree-Signmore » intervals and it rotates together with the variable-size collimator to form 36 noncoplanar, concentric arcs focused at the isocenter. The patient support table enables motion in three dimensions to position the patient tumor at the focal point of the irradiation. The table moves continuously in three cardinal dimensions during treatment to provide dynamic shaping of the dose distribution. The breast is immobilized using a breast cup applying a small negative pressure, where the immobilization cup is embedded with fiducials also functioning as the stereotactic frame for the breast. Geometric and dosimetric evaluations of the system as well as a protocol for absorbed dose calibration are provided. Dosimetric verifications of dynamically delivered patient plans are performed for seven patients using radiochromic films in hypothetical preop, postop, and target-in-target treatment scenarios. Results: Loaded with 36 {sup 60}Co sources with cumulative activity of 4320 Ci, the prototype GammaPod Trade-Mark-Sign unit delivers 5.31 Gy/min at the isocenter using the largest 2.5 cm diameter collimator. Due to the noncoplanar beam arrangement and dynamic dose shaping features, the GammaPod Trade-Mark-Sign device is found to deliver uniform doses to targets with good conformity. The spatial accuracy of the device to locate the radiation isocenter is determined to be less than 1 mm. Single shot profiles with 2.5 cm collimator are measured with radiochromic film and found to be in good agreement with respect to the Monte Carlo based calculations (congruence of FWHM less than 1 mm). Dosimetric verifications corresponding to all hypothetical treatment plans corresponding to three target scenarios for each of the seven patients demonstrated good agreement with gamma index pass rates of better than 97% (99.0%{+-} 0.7%). Conclusions: Dosimetric evaluation of the first GammaPod Trade-Mark-Sign stereotactic breast radiotherapy unit was performed and the dosimetric and spatial accuracy of this novel technology is found to be feasible with respect to clinical radiotherapy standards. The observed level of agreement between the treatment planning system calculations and dosimetric measurements has confirmed that the system can deliver highly complex treatment plans with remarkable geometric and dosimetric accuracy.« less

Dosimetric measurements of an n-butyl cyanoacrylate embolization material for arteriovenous malformations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Labby, Zacariah E., E-mail: zelabby@humonc.wisc.edu; Chaudhary, Neeraj; Gemmete, Joseph J.

2015-04-15

Purpose: The therapeutic regimen for cranial arteriovenous malformations often involves both stereotactic radiosurgery and endovascular embolization. Embolization agents may contain tantalum or other contrast agents to assist the neurointerventionalists, leading to concerns regarding the dosimetric effects of these agents. This study investigated dosimetric properties of n-butyl cyanoacrylate (n-BCA) plus lipiodol with and without tantalum powder. Methods: The embolization agents were provided cured from the manufacturer with and without added tantalum. Attenuation measurements were made for the samples and compared to the attenuation of a solid water substitute using a 6 MV photon beam. Effective linear attenuation coefficients (ELAC) were derivedmore » from attenuation measurements made using a portal imager and derived sample thickness maps projected in an identical geometry. Probable dosimetric errors for calculations in which the embolized regions are overridden with the properties of water were calculated using the ELAC values. Interface effects were investigated using a parallel plate ion chamber placed at set distances below fixed samples. Finally, Hounsfield units (HU) were measured using a stereotactic radiosurgery CT protocol, and more appropriate HU values were derived from the ELAC results and the CT scanner’s HU calibration curve. Results: The ELAC was 0.0516 ± 0.0063 cm{sup −1} and 0.0580 ± 0.0091 cm{sup −1} for n-BCA without and with tantalum, respectively, compared to 0.0487 ± 0.0009 cm{sup −1} for the water substitute. Dose calculations with the embolized region set to be water equivalent in the treatment planning system would result in errors of −0.29% and −0.93% per cm thickness of n-BCA without and with tantalum, respectively. Interface effects compared to water were small in magnitude and limited in distance for both embolization materials. CT values at 120 kVp were 2082 and 2358 HU for n-BCA without and with tantalum, respectively; dosimetrically appropriate HU values were estimated to be 79 and 199 HU, respectively. Conclusions: The dosimetric properties of the embolization agents are very close to those of water for a 6 MV beam. Therefore, treating the entire intracranial space as uniform in composition will result in less than 1% dosimetric error for n-BCA emboli smaller than 3.4 cm without added tantalum and n-BCA emboli smaller than 1.1 cm with added tantalum. Furthermore, when effective embolization can be achieved by the neurointerventionalist using n-BCA without tantalum, the dosimetric impact of overriding material properties will be lessened. However, due to the high attenuation of embolization agents with and without added tantalum for diagnostic energies, artifacts may occur that necessitate additional imaging to accurately identify the spatial extent of the region to be treated.« less

Evaluation of a method for removing cesium and reducing the volume of leaf litter from broad-leaved trees contaminated by the Fukushima Daiichi nuclear accident during the Great East Japan Earthquake.

PubMed

Harada, Shigeki; Yanagisawa, Mitsunori

2017-04-01

The town of Marumori in southern Miyagi Prefecture borders on Fukushima Prefecture, and following the accident at the Fukushima Daiichi nuclear power plant, there were concerns about cesium deposition in forested areas. One of the authors of this paper has continually surveyed leaf litter from the forested areas. As leaf litter may be a source of cesium contamination from the forest to downstream areas, we considered a simplified version of wet oxidation, a method previously presented by one of the authors of this study, as a technology to reduce leaf litter weight and cesium concentration, separating radioactive nuclides from non-radioactive ones, in leaf litter. We tested our method in three experiments. Experiment 1 used new leaf litter (232 Bq/kg) from the surface of a small stream at the forest edge nearby an area with air dose level higher than the national standard threshold of 0.23 μSv/h for the implementation of governmental decontamination works. Experiment 2 applied wet oxidation to older leaf litter (705 Bq/kg) harvested from a pasture nearby the stream mentioned above. We also used the same leaf litter in experiment 3 for a cesium release tests using pure water. In experiment 1 and 2 we treated leaf litter with a sodium hypochlorite solution, optimizing sodium hypochlorite concentration and reaction temperature. We measured a 50-60% decrease in the leaf litter weight and a 60% decrease in the cesium concentration. Moreover, we also measured the amount of cesium washout. The cesium budget of experiment 1 showed no cesium gasification (wet oxidation avoids airborne cesium as this element is prone to be volatile at 600 °C), and that high sodium hypochlorite concentration and high temperature had a strong positive effect on leaf litter volume reduction and cesium decontamination. Experiment 2 confirmed the reproducibility of these results in leaves with different cesium concentration and harvested in different conditions. We could also explain the mechanism behind leaf litter weight and cesium concentration reduction. Experiment 3 helped us to investigate the effects of the matter present on the surface of the water and the contribution of water soluble cesium. Concurrent experiments on changes in leaf litter chemical composition confirmed that our modified wet oxidation method had an effect on the removal of acid-insoluble lignin. Removal of lignin, a refractory component, might allow for a better utilization of the residue left after implementation of the proposed simplified wet oxidation. Thus, real wastes could be smaller than the residues. Together with the observed smaller cesium concentration in the residue, the proposed method in this study is expected to contribute to mitigate the risk due to the fallen leaves containing cesium. Copyright © 2017 Elsevier Ltd. All rights reserved.

ENDOR-Induced EPR of Disordered Systems: Application to X-Irradiated Alanine.

PubMed

Kusakovskij, Jevgenij; Maes, Kwinten; Callens, Freddy; Vrielinck, Henk

2018-02-15

The electron paramagnetic resonance (EPR) spectra of radiation-induced radicals in organic solids are generally composed of multiple components that largely overlap due to their similar weak g anisotropy and a large number of hyperfine (HF) interactions. Such properties make these systems difficult to study using standard cw EPR spectroscopy even in single crystals. Electron-nuclear double-resonance (ENDOR) spectroscopy is a powerful and widely used complementary technique. In particular, ENDOR-induced EPR (EIE) experiments are useful for separating the overlapping contributions. In the present work, these techniques were employed to study the EPR spectrum of stable radicals in X-irradiated alanine, which is widely used in dosimetric applications. The principal values of all major proton HF interactions of the dominant radicals were determined by analyzing the magnetic field dependence of the ENDOR spectrum at 50 K, where the rotation of methyl groups is frozen. Accurate simulations of the EPR spectrum were performed after the major components were separated using an EIE analysis. As a result, new evidence in favor of the model of the second dominant radical was obtained.

TH-AB-202-04: Auto-Adaptive Margin Generation for MLC-Tracked Radiotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Glitzner, M; Lagendijk, J; Raaymakers, B

Purpose: To develop an auto-adaptive margin generator for MLC tracking. The generator is able to estimate errors arising in image guided radiotherapy, particularly on an MR-Linac, which depend on the latencies of machine and image processing, as well as on patient motion characteristics. From the estimated error distribution, a segment margin is generated, able to compensate errors up to a user-defined confidence. Method: In every tracking control cycle (TCC, 40ms), the desired aperture D(t) is compared to the actual aperture A(t), a delayed and imperfect representation of D(t). Thus an error e(t)=A(T)-D(T) is measured every TCC. Applying kernel-density-estimation (KDE), themore » cumulative distribution (CDF) of e(t) is estimated. With CDF-confidence limits, upper and lower error limits are extracted for motion axes along and perpendicular leaf-travel direction and applied as margins. To test the dosimetric impact, two representative motion traces were extracted from fast liver-MRI (10Hz). The traces were applied onto a 4D-motion platform and continuously tracked by an Elekta Agility 160 MLC using an artificially imposed tracking delay. Gafchromic film was used to detect dose exposition for static, tracked, and error-compensated tracking cases. The margin generator was parameterized to cover 90% of all tracking errors. Dosimetric impact was rated by calculating the ratio between underexposed points (>5% underdosage) to the total number of points inside FWHM of static exposure. Results: Without imposing adaptive margins, tracking experiments showed a ratio of underexposed points of 17.5% and 14.3% for two motion cases with imaging delays of 200ms and 300ms, respectively. Activating the margin generated yielded total suppression (<1%) of underdosed points. Conclusion: We showed that auto-adaptive error compensation using machine error statistics is possible for MLC tracking. The error compensation margins are calculated on-line, without the need of assuming motion or machine models. Further strategies to reduce consequential overdosages are currently under investigation. This work was funded by the SoRTS consortium, which includes the industry partners Elekta, Philips and Technolution.« less

SU-E-T-269: Quality Assurance of Spine Volumetric Modulated Arc Therapy with Flattening Filter Free Beams Using Gafchromic EBT3 Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choi, Y; Cho, B; Kwak, J

2014-06-01

Purpose: We implemented the Gafchromic film-based patient specific QA of volumetric modulated arc therapy (VMAT) with flattening-filter free (FFF) beams for spine metastases and validated the accuracy of fast arc delivery. Methods: EBT3 films and a homemade cylindrical QA phantom were employed for dosimetric verification of VMATs. For 14 FFF VMAT plans (10 with 10-MV FFF beams and 4 with 6-MV FFF beams), the doses were recalculated on the phantom and delivered by a TrueBeam STx accelerator equipped with a high-definition 120 leaf MLC. The EBT3 films were scanned using an Epson 10000XL scanner through the FilmQA Pro software. Allmore » the irradiated film images were converted to dose map using a calibration response curve. The resulting dose map of film measurement was compared with treatment plan and evaluated using gamma analysis with dose tolerance of 2% within 2 mm. In addition, the point-dose measurement in the phantom using an ion chamber was evaluated as a reference in a ratio of measured and planned doses. Results: The gamma pass rates averaged over all FFF plans for composite-field measurements were 96.0 ± 3.6% (88.9%–99.5%). When adopting a tolerance level of 3% - 3 mm, the gamma pass rates were improved with the ranges from 98% to 100%. In addition, dose profiles and dose distributions showed that spinal cord was protected by the rapid dose fall-off and by delivering the treatment with high precision. In point-dose measurements, the average differences between the measured and planned doses were 0.5% ± 1.0% of the prescription dose. Conclusion: We demonstrated that Gafchromic EBT3 film would be an effective patient-specific QA tool, especially for VMAT of spine SBRT with treatment of small fields and highly gradient dose distributions. The results of film QA verified that the dosimetric accuracy of spine SBRT utilizing RapidArc with FFF beams in our institution is reliable.« less

DOSIMETRIC CHARACTERISTICS OF GAMMA-TRON-2 (in Russian)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krongauz, A.N.; Pavlova, T.G.; Frolova, A.V.

1963-01-01

Dosimetric characteristics of the Gammatron-2 during operation in a static regimen are presented. The air dose and the distribution of doses along the central ray of the beam and on the sides were determined. The protective properties of Gammatron-2 were studied. On the basis of the measurements, charts of isodoses were elaborated. (P.C.H.)

SU-F-T-285: Evaluation of a Patient DVH-Based IMRT QA System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhen, H; Redler, G; Chu, J

2016-06-15

Purpose: To evaluate the clinical performance of a patient DVH-based QA system for prostate VMAT QA. Methods: Mobius3D(M3D) is a QA software with an independent beam model and dose engine. The MobiusFX(MFX) add-on predicts patient dose using treatment machine log files. We commissioned the Mobius beam model in two steps. First, the stock beam model was customized using machine commissioning data, then verified against the TPS with 12 simple phantom plans and 7 clinical 3D plans. Secondly, the Dosimetric Leaf Gap(DLG) in the Mobius model was fine-tuned for VMAT treatment based on ion chamber measurements for 6 clinical VMAT plans.more » Upon successful commissioning, we retrospectively performed IMRT QA for 12 VMAT plans with the Mobius system as well as the ArcCHECK-3DVH system. Selected patient DVH values (PTV D95, D50; Bladder D2cc, Dmean; Rectum D2cc) were compared between TPS, M3D, MFX, and 3DVH. Results: During the first commissioning step, TPS and M3D calculated target Dmean for 3D plans agree within 0.7%±0.7%, with 3D gamma passing rates of 98%±2%. In the second commissioning step, the Mobius DLG was adjusted by 1.2mm from the stock value, reducing the average difference between MFX calculation and ion chamber measurement from 3.2% to 0.1%. In retrospective prostate VMAT QA, 5 of 60 MFX calculated DVH values have a deviation greater than 5% compared to TPS. One large deviation at high dose level was identified as a potential QA failure. This echoes the 3DVH QA result, which identified 2 instances of large DVH deviation on the same structure. For all DVH’s evaluated, M3D and MFX show high level of agreement (0.1%±0.2%), indicating that the observed deviation is likely from beam modelling differences rather than delivery errors. Conclusion: Mobius system provides a viable solution for DVH based VMAT QA, with the capability of separating TPS and delivery errors.« less

Light-stimulated cell expansion in bean (Phaseolus vulgaris L.) leaves. II. Quantity and quality of light required

NASA Technical Reports Server (NTRS)

Van Volkenburgh, E.; Cleland, R. E.; Watanabe, M.

1990-01-01

The quantity and quality of light required for light-stimulated cell expansion in leaves of Phaseolus vulgaris L. have been determined. Seedlings were grown in dim red light (RL; 4 micromoles photons m-2 s-1) until cell division in the primary leaves was completed, then excised discs were incubated in 10 mM sucrose plus 10 mM KCl in a variety of light treatments. The growth response of discs exposed to continuous white light (WL) for 16 h was saturated at 100 micromoles m-2 s-1, and did not show reciprocity. Extensive, but not continuous, illumination was needed for maximal growth. The wavelength dependence of disc expansion was determined from fluence-response curves obtained from 380 to 730 nm provided by the Okazaki Large Spectrograph. Blue (BL; 460 nm) and red light (RL; 660 nm) were most effective in promoting leaf cell growth, both in photosynthetically active and inhibited leaf discs. Far-red light (FR; 730 nm) reduced the effectiveness of RL, but not BL, indicating that phytochrome and a separate blue-light receptor mediate expansion of leaf cells.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Okita, T.W.; Nakata, P.A.; Anderson, J.M.

ADPglucose pyrophosphorylase has been extensively purified from potato (Solanum tuberosum L.) tuber tissue to study its structure. By employing a modified published procedure together with Mono Q chromatography, a near homogeneous enzyme preparation was obtained with substantial improvement in enzyme yield and specific activity. In single dimensional sodium dodecyl sulfate polyacrylamide gels, the enzyme migrated as a single polypeptide band with a mobility of about 50,000 daltons. Analysis by two-dimensional polyacrylamide gel electrophoresis, however, revealed the presence of two types of subunits which could be distinguished by their slight differences in net charge and molecular weight. The smaller potato tubermore » subunit was recognized by antiserum prepared against the smaller spinach leaf 51 kilodalton ADPglucose pyrophosphorylase subunit. In contrast, the anti-54 kilodalton raised against the spinach leaf subunit did not significantly react to the tuber enzyme subunits. The results are consistent with the hypothesis that the potato tuber ADPglucose pyrophosphorylase is not composed of a simple homotetramer as previously suggested, but is a product of two separate and distinct subunits as observed for the spinach leaf and maize enzymes.« less

Effect of leaf incubation temperature profiles on Agrobacterium tumefaciens-mediated transient expression.

PubMed

Jung, Sang-Kyu; McDonald, Karen A; Dandekar, Abhaya M

2015-01-01

Agrobacterium tumefaciens-mediated transient expression is known to be highly dependent on incubation temperature. Compared with early studies that were conducted at constant temperature, we examined the effect of variable leaf incubation temperature on transient expression. As a model system, synthetic endoglucanase (E1) and endoxylanase (Xyn10A) genes were transiently expressed in detached whole sunflower leaves via vacuum infiltration for biofuel applications. We found that the kinetics of transient expression strongly depended on timing of the temperature change as well as leaf incubation temperature. Surprisingly, we found that high incubation temperature (27-30 °C) which is suboptimal for T-DNA transfer, significantly enhanced transient expression if the high temperature was applied during the late phase (Day 3-6) of leaf incubation whereas incubation temperature in a range of 20-25 °C for an early phase (Day 0-2) resulted in higher production. On the basis of these results, we propose that transient expression is governed by both T-DNA transfer and protein synthesis in plant cells that have different temperature dependent kinetics. Because the phases were separated in time and had different optimal temperatures, we were then able to develop a novel two phase optimization strategy for leaf incubation temperature. Applying the time-varying temperature profile, we were able to increase the protein accumulation by fivefold compared with the control at a constant temperature of 20 °C. From our knowledge, this is the first report illustrating the effect of variable temperature profiling for improved transient expression. © 2015 American Institute of Chemical Engineers.

Probing the Reproducibility of Leaf Growth and Molecular Phenotypes: A Comparison of Three Arabidopsis Accessions Cultivated in Ten Laboratories1[W

PubMed Central

Massonnet, Catherine; Vile, Denis; Fabre, Juliette; Hannah, Matthew A.; Caldana, Camila; Lisec, Jan; Beemster, Gerrit T.S.; Meyer, Rhonda C.; Messerli, Gaëlle; Gronlund, Jesper T.; Perkovic, Josip; Wigmore, Emma; May, Sean; Bevan, Michael W.; Meyer, Christian; Rubio-Díaz, Silvia; Weigel, Detlef; Micol, José Luis; Buchanan-Wollaston, Vicky; Fiorani, Fabio; Walsh, Sean; Rinn, Bernd; Gruissem, Wilhelm; Hilson, Pierre; Hennig, Lars; Willmitzer, Lothar; Granier, Christine

2010-01-01

A major goal of the life sciences is to understand how molecular processes control phenotypes. Because understanding biological systems relies on the work of multiple laboratories, biologists implicitly assume that organisms with the same genotype will display similar phenotypes when grown in comparable conditions. We investigated to what extent this holds true for leaf growth variables and metabolite and transcriptome profiles of three Arabidopsis (Arabidopsis thaliana) genotypes grown in 10 laboratories using a standardized and detailed protocol. A core group of four laboratories generated similar leaf growth phenotypes, demonstrating that standardization is possible. But some laboratories presented significant differences in some leaf growth variables, sometimes changing the genotype ranking. Metabolite profiles derived from the same leaf displayed a strong genotype × environment (laboratory) component. Genotypes could be separated on the basis of their metabolic signature, but only when the analysis was limited to samples derived from one laboratory. Transcriptome data revealed considerable plant-to-plant variation, but the standardization ensured that interlaboratory variation was not considerably larger than intralaboratory variation. The different impacts of the standardization on phenotypes and molecular profiles could result from differences of temporal scale between processes involved at these organizational levels. Our findings underscore the challenge of describing, monitoring, and precisely controlling environmental conditions but also demonstrate that dedicated efforts can result in reproducible data across multiple laboratories. Finally, our comparative analysis revealed that small variations in growing conditions (light quality principally) and handling of plants can account for significant differences in phenotypes and molecular profiles obtained in independent laboratories. PMID:20200072

Seasonal root biomass and nitrogen dynamics of big bluestem (Andropogon gerardii vitman) under wet and dry conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hayes, D.C.

1986-01-01

The relative influences of nitrogen and water deficits on plant responses to drought stress of reduced biomass and leaf nitrogen were assessed. Big blustem rhizomes were transplanted into clear polyvinyl tubes with a capillary breaker placed in the middle of the tube to allow separate watering of the upper and lower soil section. One month later, factorial treatments of nitrogen fertilizer and water deficit by soil section were initiated. Two soil types were used, coarse river sand and a very fine sandy loam. Plants were harvested and biomass and total nitrogen was determined by tissue type. Nitrogen deficit was shownmore » to have more influence on plant responses to drought stress than water deficit. The treatments with no nitrogen added averaged 70% of the leaf biomass and 43% of the total leaf nitrogen of plants with nitrogen fertilizer. The plants with a water deficit averaged 87% of the leaf biomass and 105% of the total leaf nitrogen of plants watered in both soil sections. Root dynamics were studied using root windows at Konza Prairie, a tallgrass prairie site, during a dry year (1984) and a wet year (1985). Amounts, production and disappearance of root length decreased rapidly with the onset of a drought period. Yearly summaries show that amounts, productivity and decomposition were less affected by drought with increasing soil depth. Quantitative biomass data obtained from soil cores were used to provide perspective to the root window study. Results were comparable to previous studies, with an average total root turnover rate of 31%.« less

Polyethylene Naphthalate Scintillator: A Novel Detector for the Dosimetry of Radioactive Ophthalmic Applicators.

PubMed

Flühs, Dirk; Flühs, Andrea; Ebenau, Melanie; Eichmann, Marion

2015-09-01

Dosimetric measurements in small radiation fields with large gradients, such as eye plaque dosimetry with β or low-energy photon emitters, require dosimetrically almost water-equivalent detectors with volumes of <1 mm(3) and linear responses over several orders of magnitude. Polyvinyltoluene-based scintillators fulfil these conditions. Hence, they are a standard for such applications. However, they show disadvantages with regard to certain material properties and their dosimetric behaviour towards low-energy photons. Polyethylene naphthalate, recently recognized as a scintillator, offers chemical, physical and basic dosimetric properties superior to polyvinyltoluene. Its general applicability as a clinical dosimeter, however, has not been shown yet. To prove this applicability, extensive measurements at several clinical photon and electron radiation sources, ranging from ophthalmic plaques to a linear accelerator, were performed. For all radiation qualities under investigation, covering a wide range of dose rates, a linearity of the detector response to the dose was shown. Polyethylene naphthalate proved to be a suitable detector material for the dosimetry of ophthalmic plaques, including low-energy photon emitters and other small radiation fields. Due to superior properties, it has the potential to replace polyvinyltoluene as the standard scintillator for such applications.

Dosimetric property of mineral extracted from calamari and exposed to gamma rays

NASA Astrophysics Data System (ADS)

Cruz-Zaragoza, E.; Roman-Lopez, J.; Cruz, L. Pérez; Furetta, C.; Chiaravalle, E.; Mangiacotti, M.; Marchesani, G.

2013-07-01

Dosimetric property of polymineral fraction, quartz mainly, obtained from calamari was investigated. The commercial calamari samples from China and Sud Africa were collected in the markets of Italy. All polymineral debris were extracted and isolated from the whole body of calamari. The surface of the polymineral samples was analyzed by using the Scanning Electron Microscopy (SEM) and their chemical composition was determined using Energy Dispersive Spectroscopy (EDS). The polymineral was exposed to gamma rays (60Co) at different doses (0.5-80 Gy) to determine dosimetric property. Thermoluminescent (TL) glow curves showed two peaks centered at around 98-100 °C and 128-138 °C temperature range. The glow curves have been analyzed by using a deconvolution program. A linear dose response between 0.5 to 20 Gy was observed. The TL response of the samples as a function of the time storage, fading, presented a reduction of about 36-40 % at the end of 24 h. The reproducibility of the TL response after ten cycles of irradiation-readout showed an acceptable standard deviation in dosimetry. The polimineral fraction obtained from calamari shows an interesting dosimetric property and it may be useful for dosimetry in gamma radiation field.

Performance analysis of a film dosimetric quality assurance procedure for IMRT with regard to the employment of quantitative evaluation methods.

PubMed

Winkler, Peter; Zurl, Brigitte; Guss, Helmuth; Kindl, Peter; Stuecklschweiger, Georg

2005-02-21

A system for dosimetric verification of intensity-modulated radiotherapy (IMRT) treatment plans using absolute calibrated radiographic films is presented. At our institution this verification procedure is performed for all IMRT treatment plans prior to patient irradiation. Therefore clinical treatment plans are transferred to a phantom and recalculated. Composite treatment plans are irradiated to a single film. Film density to absolute dose conversion is performed automatically based on a single calibration film. A software application encompassing film calibration, 2D registration of measurement and calculated distributions, image fusion, and a number of visual and quantitative evaluation utilities was developed. The main topic of this paper is a performance analysis for this quality assurance procedure, with regard to the specification of tolerance levels for quantitative evaluations. Spatial and dosimetric precision and accuracy were determined for the entire procedure, comprising all possible sources of error. The overall dosimetric and spatial measurement uncertainties obtained thereby were 1.9% and 0.8 mm respectively. Based on these results, we specified 5% dose difference and 3 mm distance-to-agreement as our tolerance levels for patient-specific quality assurance for IMRT treatments.

Dosimetric Evaluation of Intensity Modulated Radiotherapy and 4-Field 3-D Conformal Radiotherapy in Prostate Cancer Treatment

PubMed Central

Uysal, Bora; Beyzadeoğlu, Murat; Sager, Ömer; Dinçoğlan, Ferrat; Demiral, Selçuk; Gamsız, Hakan; Sürenkök, Serdar; Oysul, Kaan

2013-01-01

Objective: The purpose of this dosimetric study is the targeted dose homogeneity and critical organ dose comparison of 7-field Intensity Modulated Radiotherapy (IMRT) and 3-D 4-field conformal radiotherapy. Study Design: Cross sectional study. Material and Methods: Twenty patients with low and moderate risk prostate cancer treated at Gülhane Military Medical School Radiation Oncology Department between January 2009 and December 2009 are included in this study. Two seperate dosimetric plans both for 7-field IMRT and 3D-CRT have been generated for each patient to comparatively evaluate the dosimetric status of both techniques and all the patients received 7-field IMRT. Results: Dose-comparative evaluation of two techniques revealed the superiority of IMRT technique with statistically significantly lower femoral head doses along with reduced critical organ dose-volume parameters of bladder V60 (the volume receiving 60 Gy) and rectal V40 (the volume receiving 40 Gy) and V60. Conclusion: It can be concluded that IMRT is an effective definitive management tool for prostate cancer with improved critical organ sparing and excellent dose homogenization in target organs of prostate and seminal vesicles. PMID:25207069

Gaussian Radial Basis Function for Efficient Computation of Forest Indirect Illumination

NASA Astrophysics Data System (ADS)

Abbas, Fayçal; Babahenini, Mohamed Chaouki

2018-06-01

Global illumination of natural scenes in real time like forests is one of the most complex problems to solve, because the multiple inter-reflections between the light and material of the objects composing the scene. The major problem that arises is the problem of visibility computation. In fact, the computing of visibility is carried out for all the set of leaves visible from the center of a given leaf, given the enormous number of leaves present in a tree, this computation performed for each leaf of the tree which also reduces performance. We describe a new approach that approximates visibility queries, which precede in two steps. The first step is to generate point cloud representing the foliage. We assume that the point cloud is composed of two classes (visible, not-visible) non-linearly separable. The second step is to perform a point cloud classification by applying the Gaussian radial basis function, which measures the similarity in term of distance between each leaf and a landmark leaf. It allows approximating the visibility requests to extract the leaves that will be used to calculate the amount of indirect illumination exchanged between neighbor leaves. Our approach allows efficiently treat the light exchanges in the scene of a forest, it allows a fast computation and produces images of good visual quality, all this takes advantage of the immense power of computation of the GPU.

Xeromorphic traits help to maintain photosynthesis in the perhumid climate of a Taiwanese cloud forest.

PubMed

Pariyar, Shyam; Chang, Shih-Chieh; Zinsmeister, Daniel; Zhou, Haiyang; Grantz, David A; Hunsche, Mauricio; Burkhardt, Juergen

2017-07-01

Previous flux measurements in the perhumid cloud forest of northeastern Taiwan have shown efficient photosynthesis of the endemic tree species Chamaecyparis obtusa var. formosana even under foggy conditions in which leaf surface moisture would be expected. We hypothesized this to be the result of 'xeromorphic' traits of the Chamaecyparis leaves (hydrophobicity, stomatal crypts, stomatal clustering), which could prevent coverage of stomata by precipitation, fog, and condensation, thereby maintaining CO 2 uptake. Here we studied the amount, distribution, and composition of moisture accumulated on Chamaecyparis leaf surfaces in situ in the cloud forest. We studied the effect of surface tension on gas penetration to stomata using optical O 2 microelectrodes in the laboratory. We captured the dynamics of condensation to the leaf surfaces with an environmental scanning electron microscope (ESEM). In spite of substantial surface hydrophobicity, the mean water film thickness on branchlets under foggy conditions was 80 µm (upper surface) and 40 µm (lower surface). This amount of water could cover stomata and prevent CO 2 uptake. This is avoided by the clustered arrangement of stomata within narrow clefts and the presence of Florin rings. These features keep stomatal pores free from water due to surface tension and provide efficient separation of plant and atmosphere in this perhumid environment. Air pollutants, particularly hygroscopic aerosol, may disturb this functionality by enhancing condensation and reducing the surface tension of leaf surface water.

Morphological and physiological divergences within Quercus ilex support the existence of different ecotypes depending on climatic dryness

PubMed Central

Peguero-Pina, José Javier; Sancho-Knapik, Domingo; Barrón, Eduardo; Camarero, Julio Jesús; Vilagrosa, Alberto; Gil-Pelegrín, Eustaquio

2014-01-01

Background and Aims Several studies show apparently contradictory findings about the functional convergence within the Mediterranean woody flora. In this context, this study evaluates the variability of functional traits within holm oak (Quercus ilex) to elucidate whether provenances corresponding to different morphotypes represent different ecotypes locally adapted to the prevaling stress levels. Methods Several morphological and physiological traits were measured at leaf and shoot levels in 9-year-old seedlings of seven Q. ilex provenances including all recognized morphotypes. Plants were grown in a common garden for 9 years under the same environmental conditions to avoid possible biases due to site-specific characteristics. Key Results Leaf morphometry clearly separates holm oak provenances into ‘ilex’ (more elongated leaves with low vein density) and ‘rotundifolia’ (short and rounded leaves with high vein density) morphotypes. Moreover, these morphotypes represent two consistent and very contrasting functional types in response to dry climates, mainly in terms of leaf area, major vein density, leaf specific conductivity, resistance to drought-induced cavitation and turgor loss point. Conclusions The ‘ilex’ and ‘rotundifolia’ morphotypes correspond to different ecotypes as inferred from their contrasting functional traits. To the best of our knowledge, this is the first time that the combined use of morphological and physiological traits has provided support for the concept of these two holm oak morphotypes being regarded as two different species. PMID:24941998

[GPC Fingerprint Chromatograms of Aloe vera Leaf Gel Polysaccharides].

PubMed

Wang, Qiao-e; Xie, Dan; Qian, Jie; Dong, Yin-mao

2015-10-01

To establish the gel permeation chromatography (GPC) fingerprint chromatograms of polysaccharides in Aloe vera leaf gel from the same habitat (Beijing) and different habitats for evaluating the quality of Aloe vera leaf gel products commercially available and testing common adulterated substances. The samples were prepared by water-extraction and alcohol-precipitation method. GPC separation was performed on a Shodex SUGAR KS-805 (300 mm x 8.0 mm, 7 μm) column and a Shodex SUGAR KS-803 (300 mm x 8.0 mm, 6 μm) column at the temperature of 60 degrees C by eluting with 0.1 mol/L NaNO3 (containing 0.2 per thousand NaN) at a flow rate of 0.8 mL/min, the chromatographic effluent was detected by refractive index detector (RID) at the temperature of 50 degrees C. The common pattern of GPC fingerprint chromatograms was established and four common peaks were demarcated. The similarities of samples from the same habitat (Beijing) and different habitats were over 0.9. Taking the GPC fingerprint chromatograms for the qualified model, three commercially available aloe products were evaluated to be made of Aloe vera by the different manufacturing processes and four common adulterated substances of aloe polysaccharides were identified effectively. The method is simple and accurate with a good reproducibility, and it can be used for the identification and quality evaluation of Aloe vera leaf gel products.

A worldwide analysis of within-canopy variations in leaf structural, chemical and physiological traits across plant functional types.

PubMed

Niinemets, Ülo; Keenan, Trevor F; Hallik, Lea

2015-02-01

Extensive within-canopy light gradients importantly affect the photosynthetic productivity of leaves in different canopy positions and lead to light-dependent increases in foliage photosynthetic capacity per area (AA). However, the controls on AA variations by changes in underlying traits are poorly known. We constructed an unprecedented worldwide database including 831 within-canopy gradients with standardized light estimates for 304 species belonging to major vascular plant functional types, and analyzed within-canopy variations in 12 key foliage structural, chemical and physiological traits by quantitative separation of the contributions of different traits to photosynthetic acclimation. Although the light-dependent increase in AA is surprisingly similar in different plant functional types, they differ fundamentally in the share of the controls on AA by constituent traits. Species with high rates of canopy development and leaf turnover, exhibiting highly dynamic light environments, actively change AA by nitrogen reallocation among and partitioning within leaves. By contrast, species with slow leaf turnover exhibit a passive AA acclimation response, primarily determined by the acclimation of leaf structure to growth light. This review emphasizes that different combinations of traits are responsible for within-canopy photosynthetic acclimation in different plant functional types, and solves an old enigma of the role of mass- vs area-based traits in vegetation acclimation. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

A retrospective analysis for patient-specific quality assurance of volumetric-modulated arc therapy plans.

PubMed

Li, Guangjun; Wu, Kui; Peng, Guang; Zhang, Yingjie; Bai, Sen

2014-01-01

Volumetric-modulated arc therapy (VMAT) is now widely used clinically, as it is capable of delivering a highly conformal dose distribution in a short time interval. We retrospectively analyzed patient-specific quality assurance (QA) of VMAT and examined the relationships between the planning parameters and the QA results. A total of 118 clinical VMAT cases underwent pretreatment QA. All plans had 3-dimensional diode array measurements, and 69 also had ion chamber measurements. Dose distribution and isocenter point dose were evaluated by comparing the measurements and the treatment planning system (TPS) calculations. In addition, the relationship between QA results and several planning parameters, such as dose level, control points (CPs), monitor units (MUs), average field width, and average leaf travel, were also analyzed. For delivered dose distribution, a gamma analysis passing rate greater than 90% was obtained for all plans and greater than 95% for 100 of 118 plans with the 3%/3-mm criteria. The difference (mean ± standard deviation) between the point doses measured by the ion chamber and those calculated by TPS was 0.9% ± 2.0% for all plans. For all cancer sites, nasopharyngeal carcinoma and gastric cancer have the lowest and highest average passing rates, respectively. From multivariate linear regression analysis, the dose level (p = 0.001) and the average leaf travel (p < 0.001) showed negative correlations with the passing rate, and the average field width (p = 0.003) showed a positive correlation with the passing rate, all indicating a correlation between the passing rate and the plan complexity. No statistically significant correlation was found between MU or CP and the passing rate. Analysis of the results of dosimetric pretreatment measurements as a function of VMAT plan parameters can provide important information to guide the plan parameter setting and optimization in TPS. Copyright © 2014 American Association of Medical Dosimetrists. Published by Elsevier Inc. All rights reserved.

MO-G-BRE-04: Automatic Verification of Daily Treatment Deliveries and Generation of Daily Treatment Reports for a MR Image-Guided Treatment Machine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, D; Li, X; Li, H

2014-06-15

Purpose: Two aims of this work were to develop a method to automatically verify treatment delivery accuracy immediately after patient treatment and to develop a comprehensive daily treatment report to provide all required information for daily MR-IGRT review. Methods: After systematically analyzing the requirements for treatment delivery verification and understanding the available information from a novel MR-IGRT treatment machine, we designed a method to use 1) treatment plan files, 2) delivery log files, and 3) dosimetric calibration information to verify the accuracy and completeness of daily treatment deliveries. The method verifies the correctness of delivered treatment plans and beams, beammore » segments, and for each segment, the beam-on time and MLC leaf positions. Composite primary fluence maps are calculated from the MLC leaf positions and the beam-on time. Error statistics are calculated on the fluence difference maps between the plan and the delivery. We also designed the daily treatment delivery report by including all required information for MR-IGRT and physics weekly review - the plan and treatment fraction information, dose verification information, daily patient setup screen captures, and the treatment delivery verification results. Results: The parameters in the log files (e.g. MLC positions) were independently verified and deemed accurate and trustable. A computer program was developed to implement the automatic delivery verification and daily report generation. The program was tested and clinically commissioned with sufficient IMRT and 3D treatment delivery data. The final version has been integrated into a commercial MR-IGRT treatment delivery system. Conclusion: A method was developed to automatically verify MR-IGRT treatment deliveries and generate daily treatment reports. Already in clinical use since December 2013, the system is able to facilitate delivery error detection, and expedite physician daily IGRT review and physicist weekly chart review.« less

A retrospective analysis for patient-specific quality assurance of volumetric-modulated arc therapy plans

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Guangjun; Wu, Kui; Peng, Guang

2014-01-01

Volumetric-modulated arc therapy (VMAT) is now widely used clinically, as it is capable of delivering a highly conformal dose distribution in a short time interval. We retrospectively analyzed patient-specific quality assurance (QA) of VMAT and examined the relationships between the planning parameters and the QA results. A total of 118 clinical VMAT cases underwent pretreatment QA. All plans had 3-dimensional diode array measurements, and 69 also had ion chamber measurements. Dose distribution and isocenter point dose were evaluated by comparing the measurements and the treatment planning system (TPS) calculations. In addition, the relationship between QA results and several planning parameters,more » such as dose level, control points (CPs), monitor units (MUs), average field width, and average leaf travel, were also analyzed. For delivered dose distribution, a gamma analysis passing rate greater than 90% was obtained for all plans and greater than 95% for 100 of 118 plans with the 3%/3-mm criteria. The difference (mean ± standard deviation) between the point doses measured by the ion chamber and those calculated by TPS was 0.9% ± 2.0% for all plans. For all cancer sites, nasopharyngeal carcinoma and gastric cancer have the lowest and highest average passing rates, respectively. From multivariate linear regression analysis, the dose level (p = 0.001) and the average leaf travel (p < 0.001) showed negative correlations with the passing rate, and the average field width (p = 0.003) showed a positive correlation with the passing rate, all indicating a correlation between the passing rate and the plan complexity. No statistically significant correlation was found between MU or CP and the passing rate. Analysis of the results of dosimetric pretreatment measurements as a function of VMAT plan parameters can provide important information to guide the plan parameter setting and optimization in TPS.« less

Analysis of estimation of electromagnetic dosimetric values from non-ionizing radiofrequency fields in conventional road vehicle environments.

PubMed

Aguirre, Erik; Iturri, Peio Lopez; Azpilicueta, Leire; de Miguel-Bilbao, Silvia; Ramos, Victoria; Gárate, Uxue; Falcone, Francisco

2015-03-01

A high number of wireless technologies can be found operating in vehicular environments with the aim of offering different services. The dosimetric evaluation of this kind of scenarios must be performed in order to assess their compatibility with current exposure limits. In this work, a dosimetric evaluation inside a conventional car is performed, with the aid of an in-house 3D Ray Launching computational code, which has been compared with measurement results of wireless sensor networks located inside the vehicle. These results can aid in an adequate assessment of human exposure to non-ionizing radiofrequency fields, taking into account the impact of the morphology and the topology of the vehicle for current as well as for future exposure limits.

Dosimetric evaluation of lithium carbonate (Li2CO3) as a dosemeter for gamma-radiation dose measurements.

PubMed

Popoca, R; Ureña-Núñez, F

2009-06-01

This work reports the possibility of using lithium carbonate as a dosimetric material for gamma-radiation measurements. Carboxi-radical ions, CO(2)(-) and CO(3)(-), arise from the gamma irradiation of Li(2)CO(3), and these radical ions can be quantified by electron paramagnetic resonance (EPR) spectrometry. The EPR-signal response of gamma-irradiated lithium carbonate has been investigated to determine some dosimetric characteristics such as: peak-to-peak signal intensity versus gamma dose received, zero-dose response, signal fading, signal repeatability, batch homogeneity, dose rate effect and stability at different environmental conditions. Using the conventional peak-to-peak method of stable ion radicals, it is concluded that lithium carbonate could be used as a gamma dosemeter in the range of 3-100 Gy.

Process Model for Studying Regional 13C Stable Isotope Exchange between Vegetation and Atmosphere

NASA Astrophysics Data System (ADS)

Chen, J. M.; Chen, B.; Huang, L.; Tans, P.; Worthy, D.; Ishizawa, M.; Chan, D.

2007-12-01

The variation of the stable isotope 13CO2 in the air in exchange with land ecosystems results from fractionation processes in both plants and soil during photosynthesis and respiration. Its diurnal and seasonal variations therefore contain information on the carbon cycle. We developed a model (BEPS-iso) to simulate its exchange between vegetation and the atmosphere. To be useful for regional carbon cycle studies, the model has the following characteristics: (i) it considers the turbulent mixing in the vertical profile from the soil surface to the top of the planetary boundary layer (PBL); (ii) it scales individual leaf photosynthetic discrimination to the whole canopy through the separation of sunlit and shaded leaf groups; (iii) through simulating leaf-level photosynthetic processes, it has the capacity to mechanistically examine isotope discrimination resulting from meteorological forcings, such as radiation, precipitation and humidity; and (iv) through complete modeling of radiation, energy and water fluxes, it also simulates soil moisture and temperature needed for estimating ecosystem respiration and the 13C signal from the soil. After validation using flask data acquired at 20 m level on a tower near Fraserdale, Ontario, Canada, during intensive campaigns (1998-2000), the model has been used for several purposes: (i) to investigate the diurnal and seasonal variations in the disequilibrium in 13C fractionation between ecosystem respiration and photosynthesis, which is an important step in using 13C measurements to separate these carbon cycle components; (ii) to quantify the 13C rectification in the PBL, which differs significantly from CO2 rectification because of the diurnal and seasonal disequilibriums; and (iii) to model the 13C spatial and temporal variations over the global land surface for the purpose of CO2 inversion using 13C as an additional constraint.

Biological variation of Vanilla planifolia leaf metabolome.

PubMed

Palama, Tony Lionel; Fock, Isabelle; Choi, Young Hae; Verpoorte, Robert; Kodja, Hippolyte

2010-04-01

The metabolomic analysis of Vanilla planifolia leaves collected at different developmental stages was carried out using (1)H-nuclear magnetic resonance (NMR) spectroscopy and multivariate data analysis in order to evaluate their variation. Ontogenic changes of the metabolome were considered since leaves of different ages were collected at two different times of the day and in two different seasons. Principal component analysis (PCA) and partial least square modeling discriminate analysis (PLS-DA) of (1)H NMR data provided a clear separation according to leaf age, time of the day and season of collection. Young leaves were found to have higher levels of glucose, bis[4-(beta-D-glucopyranosyloxy)-benzyl]-2-isopropyltartrate (glucoside A) and bis[4-(beta-D-glucopyranosyloxy)-benzyl]-2-(2-butyl)-tartrate (glucoside B), whereas older leaves had more sucrose, acetic acid, homocitric acid and malic acid. Results obtained from PLS-DA analysis showed that leaves collected in March 2008 had higher levels of glucosides A and B as compared to those collected in August 2007. However, the relative standard deviation (RSD) exhibited by the individual values of glucosides A and B showed that those compounds vary more according to their developmental stage (50%) than to the time of day or the season in which they were collected (19%). Although morphological variations of the V. planifolia accessions were observed, no clear separation of the accessions was determined from the analysis of the NMR spectra. The results obtained in this study, show that this method based on the use of (1)H NMR spectroscopy in combination with multivariate analysis has a great potential for further applications in the study of vanilla leaf metabolome. Copyright 2009 Elsevier Ltd. All rights reserved.

SU-E-T-327: Dosimetric Impact of Beam Energy for Intrabeam Breast IORT with Different Residual Cancer Cell Distributions After Surgery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schwid, M; Zhang, H

Purpose: The purpose of this study was to evaluate the dosimetric impact of beam energy to the IORT treatment of residual cancer cells with different cancer cell distributions after breast-conserving surgery. Methods: The three dimensional (3D) radiation doses of IORT using a 4-cm spherical applicator at the energy of 40 keV and 50 keV were separately calculated at different depths of the postsurgical tumor bed. The modified linear quadratic model (MLQ) was used to estimate the radiobiological response of the tumor cells assuming different radio-sensitivities and density distributions. The impact of radiation was evaluated for two types of breast cancermore » cell lines (α /β=10, and α /β =3.8) at 20 Gy dose prescribed at the applicator surface. Cancer cell distributions in the postsurgical tissue field were assumed to be a Gaussian with the standard deviations of 0.5, 1 and 2 mm respectively, namely the cancer cell infiltrations of 1.5, 3, and 6 mm respectively. The surface cancer cell percentage was assumed to be 0.01%, 0.1%, 1% and 10% separately. The equivalent uniform doses (EUD) for all the scenarios were calculated. Results: The EUDs were found to be dependent on the distributions of cancer cells, but independent of the cancer cell radio-sensitivities and the density at the surface. EUDs of 50 keV are 1% larger than that of 40 keV. For a prescription dose of 20 Gy, EUDs of 50 keV beam are 17.52, 16.21 and 13.14 Gy respectively for 0.5, 1.0 and 2.0 mm of the standard deviation of cancer cell Gaussian distributions. Conclusion: The impact by selected energies of IORT beams is very minimal. When energy is changed from 50 keV to 40 keV, the EUDs are almost the same for the same cancer cell distribution. 40 keV can be safely used as an alternative of 50 keV beam in IORT.« less

Vitex negundo inhibits cyclooxygenase-2 inflammatory cytokine-mediated inflammation on carrageenan-induced rat hind paw edema

PubMed Central

Chattopadhyay, Pronobesh; Hazarika, Soilyadhar; Dhiman, Sunil; Upadhyay, Aadesh; Pandey, Anurag; Karmakar, Sanjeev; Singh, Lokendra

2012-01-01

Background: Vitex negundo L. (Verbenaceae) is a hardy plant widely distributed in the Indian subcontinent and used for treatment of a wide spectrum of health disorders in traditional and folk medicine, some of which have been experimentally validated. In present study, we aimed to investigate the anti-inflammatory effects of V. negundo in carrageenan-induced paw edema in rats, and to investigate the probable mechanism of anti-inflammatory action. Materials and Methods: Paw edema was produced by injecting 1% solution of carrageenan, and the paw volume was measured before and after carrageenan injection up to 5 h. V. negundo leaf oil was extracted using a Clevenger apparatus and administered by a trans-dermal route to Wistar rats and the percentage of inhibition of inflammation was observed using a Plethysmometer by comparing a compound aerosol-based formulation with 1 mg diclofinac diethylamine BP and 7 mg methyl salicylate IP/kg body weight served as a standard drug whereas paraffin oil served as the placebo group. After withdrawing of blood, serum was separated and cyclooxygenase (COX)-1 and COX-2 inhibitory activities were measured by the enzyme immuno assay (EIA) method by using a COX inhibitor screening assay kit. Results and Discussion: V. negundo leaf oil significantly (P < 0.05) reduced the carrageenan-induced paw edema as compared to the placebo group (paraffin oil) and 1 mg diclofinac diethylamine BP and 7 mg methyl salicylate IP showed the maximum inhibition of paw edema as compared to the V. negundo leaf oil treated group and the control group. Also in the present study V. negundo leaf oil showed significantly (P < 0.05) inhibits COX-1 pathways rather than COX-2 pathways as compared to the V. negundo leaf oil treated group. Conclusion: It is suggested that the V. negundo leaf oil is a potent anti-inflammatory agent and acts via inhibition of COX-2 without much interfering COX-1 pathways. PMID:22923950

A technique system for the measurement, reconstruction and character extraction of rice plant architecture

PubMed Central

Li, Xumeng; Wang, Xiaohui; Wei, Hailin; Zhu, Xinguang; Peng, Yulin; Li, Ming; Li, Tao; Huang, Huang

2017-01-01

This study developed a technique system for the measurement, reconstruction, and trait extraction of rice canopy architectures, which have challenged functional–structural plant modeling for decades and have become the foundation of the design of ideo-plant architectures. The system uses the location-separation-measurement method (LSMM) for the collection of data on the canopy architecture and the analytic geometry method for the reconstruction and visualization of the three-dimensional (3D) digital architecture of the rice plant. It also uses the virtual clipping method for extracting the key traits of the canopy architecture such as the leaf area, inclination, and azimuth distribution in spatial coordinates. To establish the technique system, we developed (i) simple tools to measure the spatial position of the stem axis and azimuth of the leaf midrib and to capture images of tillers and leaves; (ii) computer software programs for extracting data on stem diameter, leaf nodes, and leaf midrib curves from the tiller images and data on leaf length, width, and shape from the leaf images; (iii) a database of digital architectures that stores the measured data and facilitates the reconstruction of the 3D visual architecture and the extraction of architectural traits; and (iv) computation algorithms for virtual clipping to stratify the rice canopy, to extend the stratified surface from the horizontal plane to a general curved surface (including a cylindrical surface), and to implement in silico. Each component of the technique system was quantitatively validated and visually compared to images, and the sensitivity of the virtual clipping algorithms was analyzed. This technique is inexpensive and accurate and provides high throughput for the measurement, reconstruction, and trait extraction of rice canopy architectures. The technique provides a more practical method of data collection to serve functional–structural plant models of rice and for the optimization of rice canopy types. Moreover, the technique can be easily adapted for other cereal crops such as wheat, which has numerous stems and leaves sheltering each other. PMID:28558045

Characteristics of a novel treatment system for linear accelerator–based stereotactic radiosurgery

PubMed Central

Li, Haisen; Song, Kwang; Chin‐Snyder, Karen; Qin, Yujiao; Kim, Jinkoo; Bellon, Maria; Gulam, Misbah; Gardner, Stephen; Doemer, Anthony; Devpura, Suneetha; Gordon, James; Chetty, Indrin; Siddiqui, Farzan; Ajlouni, Munther; Pompa, Robert; Hammoud, Zane; Simoff, Michael; Kalkanis, Steven; Movsas, Benjamin; Siddiqui, M. Salim

2015-01-01

The purpose of this study is to characterize the dosimetric properties and accuracy of a novel treatment platform (Edge radiosurgery system) for localizing and treating patients with frameless, image‐guided stereotactic radiosurgery (SRS) and stereotactic body radiotherapy (SBRT). Initial measurements of various components of the system, such as a comprehensive assessment of the dosimetric properties of the flattening filter‐free (FFF) beams for both high definition (HD120) MLC and conical cone‐based treatment, positioning accuracy and beam attenuation of a six degree of freedom (6DoF) couch, treatment head leakage test, and integrated end‐to‐end accuracy tests, have been performed. The end‐to‐end test of the system was performed by CT imaging a phantom and registering hidden targets on the treatment couch to determine the localization accuracy of the optical surface monitoring system (OSMS), cone‐beam CT (CBCT), and MV imaging systems, as well as the radiation isocenter targeting accuracy. The deviations between the percent depth‐dose curves acquired on the new linac‐based system (Edge), and the previously published machine with FFF beams (TrueBeam) beyond Dmax were within 1.0% for both energies. The maximum deviation of output factors between the Edge and TrueBeam was 1.6%. The optimized dosimetric leaf gap values, which were fitted using Eclipse dose calculations and measurements based on representative spine radiosurgery plans, were 0.700 mm and 1.000 mm, respectively. For the conical cones, 6X FFF has sharper penumbra ranging from 1.2−1.8 mm (80%‐20%) and 1.9−3.8 mm (90%‐10%) relative to 10X FFF, which has 1.2−2.2 mm and 2.3−5.1 mm, respectively. The relative attenuation measurements of the couch for PA, PA (rails‐in), oblique, oblique (rails‐out), oblique (rails‐in) were: −2.0%, −2.5%, −15.6%, −2.5%, −5.0% for 6X FFF and −1.4%, −1.5%, −12.2%, −2.5%, −5.0% for 10X FFF, respectively, with a slight decrease in attenuation versus field size. The systematic deviation between the OSMS and CBCT was −0.4±0.2 mm, 0.1±0.3 mm, and 0.0±0.1 mm in the vertical, longitudinal, and lateral directions. The mean values and standard deviations of the average deviation and maximum deviation of the daily Winston‐Lutz tests over three months are 0.20±0.03 mm and 0.66±0.18 mm, respectively. Initial testing of this novel system demonstrates the technology to be highly accurate and suitable for frameless, linac‐based SRS and SBRT treatment. PACS number: 87.56.J‐ PMID:26218998

WE-AB-209-12: Quasi Constrained Multi-Criteria Optimization for Automated Radiation Therapy Treatment Planning

DOE Office of Scientific and Technical Information (OSTI.GOV)

Watkins, W.T.; Siebers, J.V.

Purpose: To introduce quasi-constrained Multi-Criteria Optimization (qcMCO) for unsupervised radiation therapy optimization which generates alternative patient-specific plans emphasizing dosimetric tradeoffs and conformance to clinical constraints for multiple delivery techniques. Methods: For N Organs At Risk (OARs) and M delivery techniques, qcMCO generates M(N+1) alternative treatment plans per patient. Objective weight variations for OARs and targets are used to generate alternative qcMCO plans. For 30 locally advanced lung cancer patients, qcMCO plans were generated for dosimetric tradeoffs to four OARs: each lung, heart, and esophagus (N=4) and 4 delivery techniques (simple 4-field arrangements, 9-field coplanar IMRT, 27-field non-coplanar IMRT, and non-coplanarmore » Arc IMRT). Quasi-constrained objectives included target prescription isodose to 95% (PTV-D95), maximum PTV dose (PTV-Dmax)< 110% of prescription, and spinal cord Dmax<45 Gy. The algorithm’s ability to meet these constraints while simultaneously revealing dosimetric tradeoffs was investigated. Statistically significant dosimetric tradeoffs were defined such that the coefficient of determination between dosimetric indices which varied by at least 5 Gy between different plans was >0.8. Results: The qcMCO plans varied mean dose by >5 Gy to ipsilateral lung for 24/30 patients, contralateral lung for 29/30 patients, esophagus for 29/30 patients, and heart for 19/30 patients. In the 600 plans computed without human interaction, average PTV-D95=67.4±3.3 Gy, PTV-Dmax=79.2±5.3 Gy, and spinal cord Dmax was >45 Gy in 93 plans (>50 Gy in 2/600 plans). Statistically significant dosimetric tradeoffs were evident in 19/30 plans, including multiple tradeoffs of at least 5 Gy between multiple OARs in 7/30 cases. The most common statistically significant tradeoff was increasing PTV-Dmax to reduce OAR dose (15/30 patients). Conclusion: The qcMCO method can conform to quasi-constrained objectives while revealing significant variations in OAR doses including mean dose reductions >5 Gy. Clinical implementation will facilitate patient-specific decision making based on achievable dosimetry as opposed to accept/reject models based on population derived objectives.« less

Preliminary study for small animal preclinical hadrontherapy facility

NASA Astrophysics Data System (ADS)

Russo, G.; Pisciotta, P.; Cirrone, G. A. P.; Romano, F.; Cammarata, F.; Marchese, V.; Forte, G. I.; Lamia, D.; Minafra, L.; Bravatá, V.; Acquaviva, R.; Gilardi, M. C.; Cuttone, G.

2017-02-01

Aim of this work is the study of the preliminary steps to perform a particle treatment of cancer cells inoculated in small animals and to realize a preclinical hadrontherapy facility. A well-defined dosimetric protocol was developed to explicate the steps needed in order to perform a precise proton irradiation in small animals and achieve a highly conformal dose into the target. A precise homemade positioning and holding system for small animals was designed and developed at INFN-LNS in Catania (Italy), where an accurate Monte Carlo simulation was developed, using Geant4 code to simulate the treatment in order to choose the best animal position and perform accurately all the necessary dosimetric evaluations. The Geant4 application can also be used to realize dosimetric studies and its peculiarity consists in the possibility to introduce the real target composition in the simulation using the DICOM micro-CT image. This application was fully validated comparing the results with the experimental measurements. The latter ones were performed at the CATANA (Centro di AdroTerapia e Applicazioni Nucleari Avanzate) facility at INFN-LNS by irradiating both PMMA and water solid phantom. Dosimetric measurements were performed using previously calibrated EBT3 Gafchromic films as a detector and the results were compared with the Geant4 simulation ones. In particular, two different types of dosimetric studies were performed: the first one involved irradiation of a phantom made up of water solid slabs where a layer of EBT3 was alternated with two different slabs in a sandwich configuration, in order to validate the dosimetric distribution. The second one involved irradiation of a PMMA phantom made up of a half hemisphere and some PMMA slabs in order to simulate a subcutaneous tumour configuration, normally used in preclinical studies. In order to evaluate the accordance between experimental and simulation results, two different statistical tests were made: Kolmogorov test and gamma index test. This work represents the first step towards the realization of a preclinical hadrontherapy facility at INFN-LNS in Catania for the future in vivo studies.

SU-F-T-107: Correlations Between Dosimetric Indices of Pharyngeal Constrictors and Proximal Esophagus with Associated Patient-Reported Outcomes Six Months After Radiation Therapy for Head and Neck Cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chera, B; Price, A; Kostich, M

Purpose: To compare the correlations between different dosimetric indices derived from the pharyngeal constrictor muscles and proximal esophagus with patient-reported difficulty in swallowing 6 months post radiotherapy using a novel patient reported outcome version of CTCAE (PRO-CTCAE). Methods: Forty-three patients with oropharyngeal squamous cell carcinoma were treated on a prospective multi-institutional study. All patients received de-intensified 60 Gy intensity modulated radiotherapy. We investigated correlations of individual patient dosimetric data of the superior (SPC), middle (MPC), inferior (IPC) pharyngeal constrictor muscles, the superior esophagus (SES), and the inferior esophagus (IES) to their self-reported 6 month post-treatment swallowing difficulty responses. Mild (≥more » Grade 1) swallowing difficulty responses were used as the clinical endpoint indicating response. The predictive efficacy of Dmean and dose-volume (VD) points were assessed through the area under the Receiver Operating Characteristic curve (ROC) and Odds Ratio (OR). Results: The SES and SPC had more favorable area under the curves (AUC) for the Dmean (0.62 and 0.70) while the Dmean to the IPC, MPC, and IES produced suboptimal AUCs (0.42, 0.48, and 0.52). Additionally, over the range of VD, the V54 and V55 for the SES and SPC demonstrated the highest AUCs: AUC(SES) = 0.76–0.73 and AUC(SPC) = 0.72–0.69, respectively. The IES, IPC, and MPC had worse AUC results over the range of VD. An optimal OR can be found when V54 = 96% for the SPC, where OR = 3.96 (1.07–14.62). Conclusion: The V45 and V55 of the SES and SPC had the highest correlation to the clinical endpoint compared to the commonly used dosimetric index, Dmean for both the esophagus and constrictor muscles. The reported dosimetric data demonstrates that new dosimetric indices may need to be considered in the setting of dose de-escalation and self-reported outcomes.« less

Dosimetric comparison between proton beam therapy and photon radiation therapy for locally advanced esophageal squamous cell carcinoma.

PubMed

Hirano, Yasuhiro; Onozawa, Masakatsu; Hojo, Hidehiro; Motegi, Atsushi; Zenda, Sadatomo; Hotta, Kenji; Moriya, Shunsuke; Tachibana, Hidenobu; Nakamura, Naoki; Kojima, Takashi; Akimoto, Tetsuo

2018-02-09

The purpose of this study was to perform a dosimetric comparison between proton beam therapy (PBT) and photon radiation therapy in patients with locally advanced esophageal squamous cell carcinoma (ESCC) who were treated with PBT in our institution. In addition, we evaluated the correlation between toxicities and dosimetric parameters, especially the doses to normal lung or heart tissue, to clarify the clinical advantage of PBT over photon radiation therapy. A total of 37 consecutive patients with Stage III thoracic ESCC who had received PBT with or without concurrent chemotherapy between October 2012 and December 2015 were evaluated in this study. The dose distributions of PBT were compared with those of dummy 3-dimensional conformal radiation therapy (3DCRT) and Intensity Modulated Radiation Therapy (IMRT), focusing especially on the doses to organs at risk, such as normal lung and heart tissue. Of the 37 patients, the data from 27 patients were analyzed. Among these 27 patients, four patients (15%) developed grade 2 pericardial effusion as a late toxicity. None of the patients developed grade 3 or worse acute or late pulmonary and cardiac toxicities. When the dosimetric parameters between PBT and planned 3DCRT were compared, all the PBT domestic variables for the lung dose except for lung V10 GyE and V15 GyE were significantly lower than those for the dummy 3DCRT plans, and the PBT domestic variables for the heart dose were also significantly lower than those for the dummy 3DCRT plans. When the PBT and IMRT plans were compared, all the PBT domestic variables for the doses to the lung and heart were significantly lower than those for the dummy IMRT plans. Regarding the correlation between the grades of toxicities and the dosimetric parameters, no significant correlation was seen between the occurrence of grade 2 pericardial effusion and the dose to the heart. When the dosimetric parameters of the dose distributions for the treatment of patients with locally advanced stage III ESCC were compared between PBT and 3DCRT or IMRT, PBT enabled a significant reduction in the dose to the lung and heart, compared with 3DCRT or IMRT.

Adaptive optimization by 6 DOF robotic couch in prostate volumetric IMRT treatment: rototranslational shift and dosimetric consequences

PubMed Central

Placidi, Lorenzo; Azario, Luigi; Mattiucci, Gian Carlo; Greco, Francesca; Damiani, Andrea; Mantini, Giovanna; Frascino, Vincenzo; Piermattei, Angelo; Valentini, Vincenzo; Balducci, Mario

2015-01-01

The purpose of this study was to investigate the magnitude and dosimetric relevance of translational and rotational shifts on IGRT prostate volumetric‐modulated arc therapy (VMAT) using Protura six degrees of freedom (DOF) Robotic Patient Positioning System. Patients with cT3aN0M0 prostate cancer, treated with VMAT simultaneous integrated boost (VMAT‐SIB), were enrolled. PTV2 was obtained adding 0.7 cm margin to seminal vesicles base (CTV2), while PTV1 adding to prostate (CTV1) 0.7 cm margin in all directions, except 1.2 cm, as caudal margin. A daily CBCT was acquired before dose delivery. The translational and rotational displacements were corrected through Protura Robotic Couch, collected and applied to the simulation CT to obtain a translated CT (tCT) and a rototranslated CT (rtCT) on which we recalculated the initial treatment plan (TP). We analyzed the correlation between dosimetric coverage, organs at risk (OAR) sparing, and translational or rotational displacements. The dosimetric impact of a rototranslational correction was calculated. From October 2012 to September 2013, a total of 263 CBCT scans from 12 patients were collected. Translational shifts were <5mm in 81% of patients and the rotational shifts were <2∘ in 93% of patient scans. The dosimetric analysis was performed on 172 CBCT scans and calculating 344 VMAT‐TP. Two significant linear correlations were observed between yaw and the V20 femoral heads and between pitch rotation and V50 rectum (p<0.001); rototranslational correction seems to impact more on PTV2 than on PTV1, especially when margins are reduced. Rotational errors are of dosimetric significance in sparing OAR and in target coverage. This is relevant for femoral heads and rectum because of major distance from isocenter, and for seminal vesicles because of irregular shape. No correlation was observed between translational and rotational errors. A study considering the intrafractional error and the deformable registration is ongoing. PACS number: 87.55.de PMID:26699314

Proton Therapy Dose Characterization and Verification

DTIC Science & Technology

2016-10-01

than recommended as these patients are on a separate UPENN research study where dose maximum accepted was 6700 cGy. 15... Research Protection Office. 8.0 Data Handling and Record Keeping All patients must have a signed Informed Consent Form and an On - study (confirmation...this award. Phase 1 concentrated on designing and building a Multi-leaf collimator for use in proton therapy. Phase 2 focused on studying the

Simultaneous determination of aegeline and six coumarins from different parts of the plant Aegle marmelos using UHPLC-PDA-MS and chiral separation of aegeline using HPLC-ToF-MS

USDA-ARS?s Scientific Manuscript database

A fast UHPLC-PDA method was developed for the simultaneous analysis of one alkaloid, aegeline, and six coumarins namely: umbelliferone; scopoletin; marmesinin; 8-hydroxypsoralen angelicin and marmelosin from leaf, fruit, root and bark of Aegle marmelos (L.) Corrêa (Rutaceae). The method was validate...

Spectral separability and mapping potential of cassava leaf damage symptoms caused by whiteflies (Bemisia tabaci).

PubMed

Sims, Neil C; De Barro, Paul; Newnham, Glenn J; Kalyebi, Andrew; Macfadyen, Sarina; Malthus, Tim J

2018-01-01

This study examines whether leaf spectra can be used to measure damage to cassava plants from whitefly (Bemisia tabaci), and the potential to translate measurements from leaf to landscape scale in eastern Africa. Symptoms of the cassava brown streak disease (CBSD) and cassava mosaic disease (CMD) viruses, and sooty mould (SM) blackening of lower leaves from whiteflies feeding on the upper leaves, were measured at the leaf scale with a high-resolution spectroradiometer and a single photon avalanche diode (SPAD) meter, which retrieves relative chlorophyll concentration. Spectral measurements were compared to the five-level visual scores used to assess the severity of each of the three damaging agents in the field, and also to leaf chemistry data. Leaves exhibiting severe CBSD and CMD were spectrally indistinguishable from leaves without any symptoms. Severe SM was spectrally distinctive but is likely to be difficult to map because of its occurrence in the lower crown. SPAD measurements were highly correlated with most foliar chemistry measurements and field scores of disease severity. Regression models between simulated Sentinel 2 bands, field scores and SPAD measurements were strongest using wavelengths with high importance weightings in random forest models. SPAD measurements are highly correlated to many foliar chemistry parameters, and should be considered for use in mapping disease severity over larger areas. Remaining challenges for mapping relate to the subtle expression of symptoms, the spatial distribution of disease severity within fields, and the small size and complex structure of the cassava fields themselves. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Decomposition of oak leaf litter and millipede faecal pellets in soil under temperate mixed oak forest

NASA Astrophysics Data System (ADS)

Tajovský, Karel; Šimek, Miloslav; Háněl, Ladislav; Šantrůčková, Hana; Frouz, Jan

2015-04-01

The millipedes Glomeris hexasticha (Diplopoda, Glomerida) were maintained under laboratory conditions and fed on oak leaf litter collected from a mixed oak forest (Abieto-Quercetum) in South Bohemia, Czech Republic. Every fourth day litter was changed and produced faecal pellets were separated and afterwards analysed. Content of organic carbon and C:N ratio lowered in faecal pellets as compared with consumed litter. Changes in content of chemical elements (P, K, Ca, Mg, Na) were recognised as those characteristic for the first stage of degradation of plant material. Samples of faecal pellets and oak leaf litter were then exposed in mesh bags between the F and H layers of forest soil for up to one year, subsequently harvested and analysed. A higher rate of decomposition of exposed litter than that of faecal pellets was found during the first two weeks. After 1-year exposure, the weight of litter was reduced to 51%, while that of pellets to 58% only, although the observed activity of present biotic components (algae, protozoans, nematodes; CO2 production, nitrogenase activity) in faecal pellets was higher as compared with litter. Different micro-morphological changes were observed in exposed litter and in pellets although these materials originated from the same initial sources. Comparing to intact leaf litter, another structural and functional processes occurred in pellets due to the fragmentation of plant material by millipedes. Both laboratory and field experiments showed that the millipede faecal pellets are not only a focal point of biodegradation activity in upper soil layers, but also confirmed that millipede feces undergo a slower decomposition than original leaf litter.

Characterizing the cytoprotective activity of Sarracenia purpurea L., a medicinal plant that inhibits glucotoxicity in PC12 cells.

PubMed

Harris, Cory S; Asim, Muhammad; Saleem, Ammar; Haddad, Pierre S; Arnason, John T; Bennett, Steffany A L

2012-12-05

The purple pitcher plant, Sarracenia purpurea L., is a widely distributed species in North America with a history of use as both a marketed pain therapy and a traditional medicine in many aboriginal communities. Among the Cree of Eeyou Istchee in northern Québec, the plant is employed to treat symptoms of diabetes and the leaf extract demonstrates multiple anti-diabetic activities including cytoprotection in an in vitro model of diabetic neuropathy. The current study aimed to further investigate this activity by identifying the plant parts and secondary metabolites that contribute to these cytoprotective effects. Ethanolic extracts of S. purpurea leaves and roots were separately administered to PC12 cells exposed to glucose toxicity with subsequent assessment by two cell viability assays. Assay-guided fractionation of the active extract and fractions was then conducted to identify active principles. Using high pressure liquid chromatography together with mass spectrometry, the presence of identified actives in both leaf and root extracts were determined. The leaf extract, but not that of the root, prevented glucose-mediated cell loss in a concentration-dependent manner. Several fractions elicited protective effects, indicative of multiple active metabolites, and, following subfractionation of the polar fraction, hyperoside (quercetin-3-O-galactoside) and morroniside were isolated as active constituents. Phytochemical analysis confirmed the presence of hyperoside in the leaf but not root extract and, although morroniside was detected in both organs, its concentration was seven times higher in the leaf. Our results not only support further study into the therapeutic potential and safety of S. purpurea as an alternative and complementary treatment for diabetic complications associated with glucose toxicity but also identify active principles that can be used for purposes of standardization and quality control.

Characterizing the cytoprotective activity of Sarracenia purpurea L., a medicinal plant that inhibits glucotoxicity in PC12 cells

PubMed Central

2012-01-01

Background The purple pitcher plant, Sarracenia purpurea L., is a widely distributed species in North America with a history of use as both a marketed pain therapy and a traditional medicine in many aboriginal communities. Among the Cree of Eeyou Istchee in northern Québec, the plant is employed to treat symptoms of diabetes and the leaf extract demonstrates multiple anti-diabetic activities including cytoprotection in an in vitro model of diabetic neuropathy. The current study aimed to further investigate this activity by identifying the plant parts and secondary metabolites that contribute to these cytoprotective effects. Methods Ethanolic extracts of S. purpurea leaves and roots were separately administered to PC12 cells exposed to glucose toxicity with subsequent assessment by two cell viability assays. Assay-guided fractionation of the active extract and fractions was then conducted to identify active principles. Using high pressure liquid chromatography together with mass spectrometry, the presence of identified actives in both leaf and root extracts were determined. Results The leaf extract, but not that of the root, prevented glucose-mediated cell loss in a concentration-dependent manner. Several fractions elicited protective effects, indicative of multiple active metabolites, and, following subfractionation of the polar fraction, hyperoside (quercetin-3-O-galactoside) and morroniside were isolated as active constituents. Phytochemical analysis confirmed the presence of hyperoside in the leaf but not root extract and, although morroniside was detected in both organs, its concentration was seven times higher in the leaf. Conclusion Our results not only support further study into the therapeutic potential and safety of S. purpurea as an alternative and complementary treatment for diabetic complications associated with glucose toxicity but also identify active principles that can be used for purposes of standardization and quality control. PMID:23216659

Anatomy and ultrastructure of embryonic leaves of the C4 species Setaria viridis.

PubMed

Junqueira, Nicia E G; Ortiz-Silva, Bianca; Leal-Costa, Marcos Vinícius; Alves-Ferreira, Márcio; Dickinson, Hugh G; Langdale, Jane A; Reinert, Fernanda

2018-05-11

Setaria viridis is being promoted as a model C4 photosynthetic plant because it has a small genome (~515 Mb), a short life cycle (~60 d) and it can be transformed. Unlike other C4 grasses such as maize, however, there is very little information about how C4 leaf anatomy (Kranz anatomy) develops in S. viridis. As a foundation for future developmental genetic studies, we provide an anatomical and ultrastructural framework of early shoot development in S. viridis, focusing on the initiation of Kranz anatomy in seed leaves. Setaria viridis seeds were germinated and divided into five stages covering development from the dry seed (stage S0) to 36 h after germination (stage S4). Material at each of these stages was examined using conventional light, scanning and transmission electron microscopy. Dry seeds contained three embryonic leaf primordia at different developmental stages (plastochron 1-3 primordia). The oldest (P3) leaf primordium possessed several procambial centres whereas P2 displayed only ground meristem. At the tip of P3 primordia at stage S4, C4 leaf anatomy typical of the malate dehydrogenase-dependent nicotinamide dinucleotide phosphate (NADP-ME) subtype was evident in that vascular bundles lacked a mestome layer and were surrounded by a single layer of bundle sheath cells that contained large, centrifugally located chloroplasts. Two to three mesophyll cells separated adjacent vascular bundles and one mesophyll cell layer on each of the abaxial and adaxial sides delimited vascular bundles from the epidermis. The morphological trajectory reported here provides a foundation for studies of gene regulation during early leaf development in S. viridis and a framework for comparative analyses with other C4 grasses.

Spectral separability and mapping potential of cassava leaf damage symptoms caused by whiteflies (Bemisia tabaci)

PubMed Central

De Barro, Paul; Newnham, Glenn J; Kalyebi, Andrew; Macfadyen, Sarina; Malthus, Tim J

2017-01-01

Abstract BACKGROUND This study examines whether leaf spectra can be used to measure damage to cassava plants from whitefly (Bemisia tabaci), and the potential to translate measurements from leaf to landscape scale in eastern Africa. Symptoms of the cassava brown streak disease (CBSD) and cassava mosaic disease (CMD) viruses, and sooty mould (SM) blackening of lower leaves from whiteflies feeding on the upper leaves, were measured at the leaf scale with a high‐resolution spectroradiometer and a single photon avalanche diode (SPAD) meter, which retrieves relative chlorophyll concentration. Spectral measurements were compared to the five‐level visual scores used to assess the severity of each of the three damaging agents in the field, and also to leaf chemistry data. RESULTS Leaves exhibiting severe CBSD and CMD were spectrally indistinguishable from leaves without any symptoms. Severe SM was spectrally distinctive but is likely to be difficult to map because of its occurrence in the lower crown. SPAD measurements were highly correlated with most foliar chemistry measurements and field scores of disease severity. Regression models between simulated Sentinel 2 bands, field scores and SPAD measurements were strongest using wavelengths with high importance weightings in random forest models. CONCLUSION SPAD measurements are highly correlated to many foliar chemistry parameters, and should be considered for use in mapping disease severity over larger areas. Remaining challenges for mapping relate to the subtle expression of symptoms, the spatial distribution of disease severity within fields, and the small size and complex structure of the cassava fields themselves. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. PMID:28851022

Are rates of species diversification and body size evolution coupled in the ferns?

PubMed

Testo, Weston L; Sundue, Michael A

2018-03-01

Understanding the relationship between phenotypic evolution and lineage diversification is a central goal of evolutionary biology. To extend our understanding of the role morphological evolution plays in the diversification of plants, we examined the relationship between leaf size evolution and lineage diversification across ferns. We tested for an association between body size evolution and lineage diversification using a comparative phylogenetic approach that combined a time-calibrated phylogeny and leaf size data set for 2654 fern species. Rates of leaf size change and lineage diversification were estimated using BAMM, and rate correlations were performed for rates obtained for all families and individual species. Rates and patterns of rate-rate correlation were also analyzed separately for terrestrial and epiphytic taxa. We find no significant correlation between rates of leaf area change and lineage diversification, nor was there a difference in this pattern when growth habit is considered. Our results are consistent with the findings of an earlier study that reported decoupled rates of body size evolution and diversification in the Polypodiaceae, but conflict with a recent study that reported a positive correlation between body size evolution and lineage diversification rates in the tree fern family Cyatheaceae. Our findings indicate that lineage diversification in ferns is largely decoupled from shifts in body size, in contrast to several other groups of organisms. Speciation in ferns appears to be primarily driven by hybridization and isolation along elevational gradients, rather than adaptive radiations featuring prominent morphological restructuring. The exceptional diversity of leaf morphologies in ferns appears to reflect a combination of ecophysiological constraints and adaptations that are not key innovations. © 2018 Botanical Society of America.

The sky is falling III: The effect of deposition from static solid rocket motor tests on juvenile crops.

PubMed

Doucette, William J; Curry, Eric; McNeill, Laurie S; Heavilin, Justin

2017-12-01

A mixture of combustion products (mainly hydrogen chloride, aluminum oxide, and water) and entrained soil, referred to as Test Fire Soil (TFS), can be deposited on crops during static solid rocket motor tests. The impact of a reported worst-case event was previously evaluated by exposing corn and alfalfa to 3200-gTFS/m 2 at 54days after emergence. Exposures via soil and leaves were evaluated separately. Reduced growth (soil exposure) and leaf "scorch" (leaf exposure) were attributed mainly to the high chloride concentrations in the TFS (56,000mg/kg). A follow-up study was conducted to evaluate the effect of a typical deposition event (70-gTFS/m 2 , estimated by radar during several tests) and exposure (soil and leaves simultaneously) on juvenile corn, alfalfa, and winter wheat. Younger crops were used to examine potential age sensitivity differences. Impact was evaluated by comparing the growth, elemental composition, and leaf chlorophyll content of treated and untreated plants. The relationship between deposition exposure and response was also addressed. Growth of corn, alfalfa, and winter wheat exposed to a typical TFS loading was not impacted, although slightly elevated concentrations of aluminum and iron were found in the leaves. At the highest loadings used for the exposure-response experiment, concentrations of chloride and calcium were higher in TFS-exposed corn leaves than in the untreated leaves. Overall results indicate that exposure to a typical deposition event does not adversely impact juvenile crops and that younger plants may be less vulnerable to TFS. However, higher TFS loadings can cause leaf scorch and increase the leaf concentrations of some elements. Copyright © 2017 Elsevier B.V. All rights reserved.

Leaf absorbance and photosynthesis

NASA Technical Reports Server (NTRS)

Schurer, Kees

1994-01-01

The absorption spectrum of a leaf is often thought to contain some clues to the photosynthetic action spectrum of chlorophyll. Of course, absorption of photons is needed for photosynthesis, but the reverse, photosynthesis when there is absorption, is not necessarily true. As a check on the existence of absorption limits we measured spectra for a few different leaves. Two techniques for measuring absorption have been used, viz. the separate determination of the diffuse reflectance and the diffuse transmittance with the leaf at a port of an integrating sphere and the direct determination of the non-absorbed fraction with the leaf in the sphere. In a cross-check both methods yielded the same results for the absorption spectrum. The spectrum of a Fuchsia leaf, covering the short-wave region from 350 to 2500 nm, shows a high absorption in UV, blue and red, the well known dip in the green and a steep fall-off at 700 nm. Absorption drops to virtually zero in the near infrared, with subsequent absorptions, corresponding to the water absorption bands. In more detailed spectra, taken at 5 nm intervals with a 5 nm bandwidth, differences in chlorophyll content show in the different depths of the dip around 550 nm and in a small shift of the absorption edge at 700 nm. Spectra for Geranium (Pelargonium zonale) and Hibiscus (with a higher chlorophyll content) show that the upper limit for photosynthesis can not be much above 700 nm. No evidence, however, is to be seen of a lower limit for photosynthesis and, in fact, some experiments down to 300 nm still did not show a decrease of the absorption although it is well recognized that no photosynthesis results with 300 nm wavelengths.

Dosimetric treatment course simulation based on a statistical model of deformable organ motion

NASA Astrophysics Data System (ADS)

Söhn, M.; Sobotta, B.; Alber, M.

2012-06-01

We present a method of modeling dosimetric consequences of organ deformation and correlated motion of adjacent organ structures in radiotherapy. Based on a few organ geometry samples and the respective deformation fields as determined by deformable registration, principal component analysis (PCA) is used to create a low-dimensional parametric statistical organ deformation model (Söhn et al 2005 Phys. Med. Biol. 50 5893-908). PCA determines the most important geometric variability in terms of eigenmodes, which represent 3D vector fields of correlated organ deformations around the mean geometry. Weighted sums of a few dominating eigenmodes can be used to simulate synthetic geometries, which are statistically meaningful inter- and extrapolations of the input geometries, and predict their probability of occurrence. We present the use of PCA as a versatile treatment simulation tool, which allows comprehensive dosimetric assessment of the detrimental effects that deformable geometric uncertainties can have on a planned dose distribution. For this, a set of random synthetic geometries is generated by a PCA model for each simulated treatment course, and the dose of a given treatment plan is accumulated in the moving tissue elements via dose warping. This enables the calculation of average voxel doses, local dose variability, dose-volume histogram uncertainties, marginal as well as joint probability distributions of organ equivalent uniform doses and thus of TCP and NTCP, and other dosimetric and biologic endpoints. The method is applied to the example of deformable motion of prostate/bladder/rectum in prostate IMRT. Applications include dosimetric assessment of the adequacy of margin recipes, adaptation schemes, etc, as well as prospective ‘virtual’ evaluation of the possible benefits of new radiotherapy schemes.

Dose-Volume Effects on Patient-Reported Acute Gastrointestinal Symptoms During Chemoradiation Therapy for Rectal Cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Ronald C.; Department of Radiation Oncology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina; Department of Radiation Oncology, Dana-Farber Cancer Institute and Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts

2012-07-15

Purpose: Research on patient-reported outcomes (PROs) in rectal cancer is limited. We examined whether dose-volume parameters of the small bowel and large bowel were associated with patient-reported gastrointestinal (GI) symptoms during 5-fluorouracil (5-FU)-based chemoradiation treatment for rectal cancer. Methods and Materials: 66 patients treated at the Brigham and Women's Hospital or Massachusetts General Hospital between 2006 and 2008 were included. Weekly during treatment, patients completed a questionnaire assessing severity of diarrhea, urgency, pain, cramping, mucus, and tenesmus. The association between dosimetric parameters and changes in overall GI symptoms from baseline through treatment was examined by using Spearman's correlation. Potential associationsmore » between these parameters and individual GI symptoms were also explored. Results: The amount of small bowel receiving at least 15 Gy (V15) was significantly associated with acute symptoms (p = 0.01), and other dosimetric parameters ranging from V5 to V45 also trended toward association. For the large bowel, correlations between dosimetric parameters and overall GI symptoms at the higher dose levels from V25 to V45 did not reach statistical significance (p = 0.1), and a significant association was seen with rectal pain from V15 to V45 (p < 0.01). Other individual symptoms did not correlate with small bowel or large bowel dosimetric parameters. Conclusions: The results of this study using PROs are consistent with prior studies with physician-assessed acute toxicity, and they identify small bowel V15 as an important predictor of acute GI symptoms during 5-FU-based chemoradiation treatment. A better understanding of the relationship between radiation dosimetric parameters and PROs may allow physicians to improve radiation planning to optimize patient outcomes.« less

Influence of Free Radicals Signal from Dental Resins on the Radio-Induced Signal in Teeth in EPR Retrospective Dosimetry

PubMed Central

Dos Santos-Goncalvez, Ana Maria; Beun, Sébastien; Leprince, Julian G.; Leloup, Gaëtane; Gallez, Bernard

2013-01-01

In case of radiological accident, retrospective dosimetry is needed to reconstruct the absorbed dose of overexposed individuals not wearing personal dosimeters at the onset of the incident. In such a situation, emergency mass triage will be required. In this context, it has been shown that Electron Paramagnetic Resonance (EPR) spectroscopy would be a rapid and sensitive method, on the field deployable system, allowing dose evaluation of a great number of people in a short time period. This methodology uses tooth enamel as a natural dosimeter. Ionising radiations create stable free radicals in the enamel, in a dose dependent manner, which can be detected by EPR directly in the mouth with an appropriate resonator. Teeth are often subject to restorations, currently made of synthetic dimethacrylate-based photopolymerizable composites. It is known that some dental composites give an EPR signal which is likely to interfere with the dosimetric signal from the enamel. So far, no information was available about the occurrence of this signal in the various composites available on the market, the magnitude of the signal compared to the dosimetric signal, nor its evolution with time. In this study, we conducted a systematic characterization of the signal (intensity, kinetics, interference with dosimetric signal) on 19 most widely used composites for tooth restoration, and on 14 experimental resins made with the most characteristic monomers found in commercial composites. Although a strong EPR signal was observed in every material, a rapid decay of the signal was noted. Six months after the polymerization, the signal was negligible in most composites compared to a 3 Gy dosimetric signal in a tooth. In some cases, a stable atypical signal was observed, which was still interfering with the dosimetric signal. PMID:23704875

The use of megavoltage CT (MVCT) images for dose recomputations

NASA Astrophysics Data System (ADS)

Langen, K. M.; Meeks, S. L.; Poole, D. O.; Wagner, T. H.; Willoughby, T. R.; Kupelian, P. A.; Ruchala, K. J.; Haimerl, J.; Olivera, G. H.

2005-09-01

Megavoltage CT (MVCT) images of patients are acquired daily on a helical tomotherapy unit (TomoTherapy, Inc., Madison, WI). While these images are used primarily for patient alignment, they can also be used to recalculate the treatment plan for the patient anatomy of the day. The use of MVCT images for dose computations requires a reliable CT number to electron density calibration curve. In this work, we tested the stability of the MVCT numbers by determining the variation of this calibration with spatial arrangement of the phantom, time and MVCT acquisition parameters. The two calibration curves that represent the largest variations were applied to six clinical MVCT images for recalculations to test for dosimetric uncertainties. Among the six cases tested, the largest difference in any of the dosimetric endpoints was 3.1% but more typically the dosimetric endpoints varied by less than 2%. Using an average CT to electron density calibration and a thorax phantom, a series of end-to-end tests were run. Using a rigid phantom, recalculated dose volume histograms (DVHs) were compared with plan DVHs. Using a deformed phantom, recalculated point dose variations were compared with measurements. The MVCT field of view is limited and the image space outside this field of view can be filled in with information from the planning kVCT. This merging technique was tested for a rigid phantom. Finally, the influence of the MVCT slice thickness on the dose recalculation was investigated. The dosimetric differences observed in all phantom tests were within the range of dosimetric uncertainties observed due to variations in the calibration curve. The use of MVCT images allows the assessment of daily dose distributions with an accuracy that is similar to that of the initial kVCT dose calculation.

Dosimetric treatment course simulation based on a statistical model of deformable organ motion.

PubMed

Söhn, M; Sobotta, B; Alber, M

2012-06-21

We present a method of modeling dosimetric consequences of organ deformation and correlated motion of adjacent organ structures in radiotherapy. Based on a few organ geometry samples and the respective deformation fields as determined by deformable registration, principal component analysis (PCA) is used to create a low-dimensional parametric statistical organ deformation model (Söhn et al 2005 Phys. Med. Biol. 50 5893-908). PCA determines the most important geometric variability in terms of eigenmodes, which represent 3D vector fields of correlated organ deformations around the mean geometry. Weighted sums of a few dominating eigenmodes can be used to simulate synthetic geometries, which are statistically meaningful inter- and extrapolations of the input geometries, and predict their probability of occurrence. We present the use of PCA as a versatile treatment simulation tool, which allows comprehensive dosimetric assessment of the detrimental effects that deformable geometric uncertainties can have on a planned dose distribution. For this, a set of random synthetic geometries is generated by a PCA model for each simulated treatment course, and the dose of a given treatment plan is accumulated in the moving tissue elements via dose warping. This enables the calculation of average voxel doses, local dose variability, dose-volume histogram uncertainties, marginal as well as joint probability distributions of organ equivalent uniform doses and thus of TCP and NTCP, and other dosimetric and biologic endpoints. The method is applied to the example of deformable motion of prostate/bladder/rectum in prostate IMRT. Applications include dosimetric assessment of the adequacy of margin recipes, adaptation schemes, etc, as well as prospective 'virtual' evaluation of the possible benefits of new radiotherapy schemes.

Dosimetric Considerations in Respiratory-Gated Deep Inspiration Breath-Hold for Left Breast Irradiation.

PubMed

Walston, Steve; Quick, Allison M; Kuhn, Karla; Rong, Yi

2017-02-01

To present our clinical workflow of incorporating AlignRT for left breast deep inspiration breath-hold treatments and the dosimetric considerations with the deep inspiration breath-hold protocol. Patients with stage I to III left-sided breast cancer who underwent lumpectomy or mastectomy were considered candidates for deep inspiration breath-hold technique for their external beam radiation therapy. Treatment plans were created on both free-breathing and deep inspiration breath-hold computed tomography for each patient to determine whether deep inspiration breath-hold was beneficial based on dosimetric comparison. The AlignRT system was used for patient setup and monitoring. Dosimetric measurements and their correlation with chest wall excursion and increase in left lung volume were studied for free-breathing and deep inspiration breath-hold plans. Deep inspiration breath-hold plans had significantly increased chest wall excursion when compared with free breathing. This change in geometry resulted in reduced mean and maximum heart dose but did not impact lung V 20 or mean dose. The correlation between chest wall excursion and absolute reduction in heart or lung dose was found to be nonsignificant, but correlation between left lung volume and heart dose showed a linear association. It was also identified that higher levels of chest wall excursion may paradoxically increase heart or lung dose. Reduction in heart dose can be achieved for many left-sided breast and chest wall patients using deep inspiration breath-hold. Chest wall excursion as well as left lung volume did not correlate with reduction in heart dose, and it remains to be determined what metric will provide the most optimal and reliable dosimetric advantage.

Subungual squamous cell carcinoma: A case study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neill, Cory J., E-mail: coryjneill@gmail.com

The purpose of this case study is to describe a dosimetric delivery of radiation to a superficial disease process involving the skin and bone of the distal finger. A 76-year-old male patient presented with a subungual squamous cell carcinoma (SCC) of the left distal index finger with bony involvement. The patient refused conventional surgical treatment but agreed to external beam radiation therapy (EBRT). There is a gap in the current literature describing how to successfully immobilize fingers and which EBRT modality is dosimetrically advantageous in treating them. The construction of a simple immobilization method with the patient in a reproduciblemore » position is described. The use of photons and electrons were compared ultimately showing photons to be dosimetrically advantageous. Long-term efficacy of the treatment was not evaluated because of patient noncompliance.« less

DARTAB: a program to combine airborne radionuclide environmental exposure data with dosimetric and health effects data to generate tabulations of predicted health impacts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Begovich, C.L.; Eckerman, K.F.; Schlatter, E.C.

1981-08-01

The DARTAB computer code combines radionuclide environmental exposure data with dosimetric and health effects data to generate tabulations of the predicted impact of radioactive airborne effluents. DARTAB is independent of the environmental transport code used to generate the environmental exposure data and the codes used to produce the dosimetric and health effects data. Therefore human dose and risk calculations need not be added to every environmental transport code. Options are included in DARTAB to permit the user to request tabulations by various topics (e.g., cancer site, exposure pathway, etc.) to facilitate characterization of the human health impacts of the effluents.more » The DARTAB code was written at ORNL for the US Environmental Protection Agency, Office of Radiation Programs.« less

Comparison of dose accuracy between 2D array detectors and Epid for IMRT of nasopharynx cancer

NASA Astrophysics Data System (ADS)

Altiparmak, Duygu; Coban, Yasin; Merih, Adil; Avci, Gulhan Guler; Yigitoglu, Ibrahim

2017-02-01

The aim of this study is to perform the dosimetric controls of nasopharynx cancer patient's intensity modulated radiation therapy (IMRT) treatment plans that generated by treatment planing system (TPS) with using two different equipments and also to make comparison in terms of their reliability and practicability. This study has been performed at Radiation Oncology Department, Medicine Faculty in Gaziosmanpasa University by using the VARIAN CLINAC DHX linear accelerator which is operated in the range of 6 MV. Selected 10 nasopharynx patients planned in TPS (Eclipce V13.0) and approved for treatment by medical physicists and radiation oncologists. These plans recalculated on EPID and mapcheck which are 2D dosimetric equipments to obtain dose maps. To compare these two dosimetric equipments gamma analysis method has been preferred. Achieved data is presented and discussed.

A model of plant canopy polarization

NASA Technical Reports Server (NTRS)

Vanderbilt, V. C.

1980-01-01

A model for the amount of linearly polarized light reflected by the shiny leaves of grain crops is based on the morphological and phenological characteristics of the plant canopy and upon the Fresnel equations which describe the light reflection process at the smooth boundary separating two dielectrics. The theory used demonstrates that, potentially, measurements of the linearly polarized light from a crop canopy may be used as an additional feature to discriminate between crops such as wheat and barley, two crops which are so spectrally similar that they are misclassified with unacceptable frequency. Examination of the model suggests that, potentially, satellite polarization measurements may be used to monitor crop development stage, leaf water content, leaf area index, hail damage, and certain plant diseases. The information content of these measurements is needed to evaluate the proposed polarization sensor for the satellite-borne multispectral resource sampler.

Green synthesis of the Cu/Fe3O4 nanoparticles using Morinda morindoides leaf aqueous extract: A highly efficient magnetically separable catalyst for the reduction of organic dyes in aqueous medium at room temperature

NASA Astrophysics Data System (ADS)

Nasrollahzadeh, Mahmoud; Atarod, Monireh; Sajadi, S. Mohammad

2016-02-01

This paper reports the green and in-situ preparation of the Cu/Fe3O4 magnetic nanocatalyst synthesized using Morinda morindoides leaf extract without stabilizers or surfactants. The catalyst was characterized by XRD, SEM, EDS, UV-visible, TEM, VSM and TGA-DTA. The catalytic performance of the resulting nanocatalyst was examined for the reduction of 4-nitrophenol (4-NP), Congo red (CR) and Rhodamine B (RhB) in an environmental friendly medium at room temperature. The catalyst was recovered using an external magnet and reused several times without appreciable loss of its catalytic activity. In addition, the stability of the recycled catalyst has been proved by SEM and EDS techniques.

Dosimetric variations due to interfraction organ deformation in cervical cancer brachytherapy.

PubMed

Kobayashi, Kazuma; Murakami, Naoya; Wakita, Akihisa; Nakamura, Satoshi; Okamoto, Hiroyuki; Umezawa, Rei; Takahashi, Kana; Inaba, Koji; Igaki, Hiroshi; Ito, Yoshinori; Shigematsu, Naoyuki; Itami, Jun

2015-12-01

We quantitatively estimated dosimetric variations due to interfraction organ deformation in multi-fractionated high-dose-rate brachytherapy (HDRBT) for cervical cancer using a novel surface-based non-rigid deformable registration. As the number of consecutive HDRBT fractions increased, simple addition of dose-volume histogram parameters significantly overestimated the dose, compared with distribution-based dose addition. Copyright © 2015 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.

Dosimetric property of mineral extracted from calamari and exposed to gamma rays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cruz-Zaragoza, E.; Roman-Lopez, J.; Cruz, L. Perez

2013-07-03

Dosimetric property of polymineral fraction, quartz mainly, obtained from calamari was investigated. The commercial calamari samples from China and Sud Africa were collected in the markets of Italy. All polymineral debris were extracted and isolated from the whole body of calamari. The surface of the polymineral samples was analyzed by using the Scanning Electron Microscopy (SEM) and their chemical composition was determined using Energy Dispersive Spectroscopy (EDS). The polymineral was exposed to gamma rays ({sup 60}Co) at different doses (0.5-80 Gy) to determine dosimetric property. Thermoluminescent (TL) glow curves showed two peaks centered at around 98-100 Degree-Sign C and 128-138more » Degree-Sign C temperature range. The glow curves have been analyzed by using a deconvolution program. A linear dose response between 0.5 to 20 Gy was observed. The TL response of the samples as a function of the time storage, fading, presented a reduction of about 36-40 % at the end of 24 h. The reproducibility of the TL response after ten cycles of irradiation-readout showed an acceptable standard deviation in dosimetry. The polimineral fraction obtained from calamari shows an interesting dosimetric property and it may be useful for dosimetry in gamma radiation field.« less

Polyethylene Naphthalate Scintillator: A Novel Detector for the Dosimetry of Radioactive Ophthalmic Applicators

PubMed Central

Flühs, Dirk; Flühs, Andrea; Ebenau, Melanie; Eichmann, Marion

2015-01-01

Background Dosimetric measurements in small radiation fields with large gradients, such as eye plaque dosimetry with β or low-energy photon emitters, require dosimetrically almost water-equivalent detectors with volumes of <1 mm3 and linear responses over several orders of magnitude. Polyvinyltoluene-based scintillators fulfil these conditions. Hence, they are a standard for such applications. However, they show disadvantages with regard to certain material properties and their dosimetric behaviour towards low-energy photons. Purpose, Materials and Methods Polyethylene naphthalate, recently recognized as a scintillator, offers chemical, physical and basic dosimetric properties superior to polyvinyltoluene. Its general applicability as a clinical dosimeter, however, has not been shown yet. To prove this applicability, extensive measurements at several clinical photon and electron radiation sources, ranging from ophthalmic plaques to a linear accelerator, were performed. Results For all radiation qualities under investigation, covering a wide range of dose rates, a linearity of the detector response to the dose was shown. Conclusion Polyethylene naphthalate proved to be a suitable detector material for the dosimetry of ophthalmic plaques, including low-energy photon emitters and other small radiation fields. Due to superior properties, it has the potential to replace polyvinyltoluene as the standard scintillator for such applications. PMID:27171681

Validation of a personalized dosimetric evaluation tool (Oedipe) for targeted radiotherapy based on the Monte Carlo MCNPX code

NASA Astrophysics Data System (ADS)

Chiavassa, S.; Aubineau-Lanièce, I.; Bitar, A.; Lisbona, A.; Barbet, J.; Franck, D.; Jourdain, J. R.; Bardiès, M.

2006-02-01

Dosimetric studies are necessary for all patients treated with targeted radiotherapy. In order to attain the precision required, we have developed Oedipe, a dosimetric tool based on the MCNPX Monte Carlo code. The anatomy of each patient is considered in the form of a voxel-based geometry created using computed tomography (CT) images or magnetic resonance imaging (MRI). Oedipe enables dosimetry studies to be carried out at the voxel scale. Validation of the results obtained by comparison with existing methods is complex because there are multiple sources of variation: calculation methods (different Monte Carlo codes, point kernel), patient representations (model or specific) and geometry definitions (mathematical or voxel-based). In this paper, we validate Oedipe by taking each of these parameters into account independently. Monte Carlo methodology requires long calculation times, particularly in the case of voxel-based geometries, and this is one of the limits of personalized dosimetric methods. However, our results show that the use of voxel-based geometry as opposed to a mathematically defined geometry decreases the calculation time two-fold, due to an optimization of the MCNPX2.5e code. It is therefore possible to envisage the use of Oedipe for personalized dosimetry in the clinical context of targeted radiotherapy.

Transformation of Physical DVHs to Radiobiologically Equivalent Ones in Hypofractionated Radiotherapy Analyzing Dosimetric and Clinical Parameters: A Practical Approach for Routine Clinical Practice in Radiation Oncology

PubMed Central

Thrapsanioti, Zoi; Karanasiou, Irene; Platoni, Kalliopi; Efstathopoulos, Efstathios P.; Matsopoulos, George; Dilvoi, Maria; Patatoukas, George; Chaldeopoulos, Demetrios; Kelekis, Nikolaos; Kouloulias, Vassilis

2013-01-01

Purpose. The purpose of this study was to transform DVHs from physical to radiobiological ones as well as to evaluate their reliability by correlations of dosimetric and clinical parameters for 50 patients with prostate cancer and 50 patients with breast cancer, who were submitted to Hypofractionated Radiotherapy. Methods and Materials. To achieve this transformation, we used both the linear-quadratic model (LQ model) and the Niemierko model. The outcome of radiobiological DVHs was correlated with acute toxicity score according to EORTC/RTOG criteria. Results. Concerning the prostate radiotherapy, there was a significant correlation between RTOG acute rectal toxicity and D 50 (P < 0.001) and V 60 (P = 0.001) dosimetric parameters, calculated for α/β = 10 Gy. Moreover, concerning the breast radiotherapy there was a significant correlation between RTOG skin toxicity and V ≥60 dosimetric parameter, calculated for both α/β = 2.3 Gy (P < 0.001) and α/β = 10 Gy (P < 0.001). The new tool seems reliable and user-friendly. Conclusions. Our proposed model seems user-friendly. Its reliability in terms of agreement with the presented acute radiation induced toxicity was satisfactory. However, more patients are needed to extract safe conclusions. PMID:24348743

Radiation-induced complications in prostate cancer patients treated with radiotherapy

NASA Astrophysics Data System (ADS)

Azuddin, A. Yusof; Rahman, I. Abdul; Siah, N. J.; Mohamed, F.; Saadc, M.; Ismail, F.

2014-09-01

The purpose of the study is to determine the relationship between radiation-induced complications with dosimetric and radiobiological parameters for prostate cancer patients that underwent the conformal radiotherapy treatment. 17 prostate cancer patients that have been treated with conformal radiotherapy were retrospectively analysed. The dosimetric data was retrieved in the form of dose-volume histogram (DVH) from Radiotherapy Treatment Planning System. The DVH was utilised to derived Normal Tissue Complication Probability (NTCP) in radiobiological data. Follow-up data from medical records were used to grade the occurrence of acute gastrointestinal (GI) and genitourinary (GU) complications using Radiation Therapy Oncology Group (RTOG) scoring system. The chi-square test was used to determine the relationship between radiation-induced complication with dosimetric and radiobiological parameters. 8 (47%) and 7 (41%) patients were having acute GI and GU complications respectively. The acute GI complication can be associated with V60rectum, rectal mean dose and NTCPrectum with p-value of 0.016, 0.038 and 0.049 respectively. There are no significant relationships of acute GU complication with dosimetric and radiobiological variables. Further study can be done by increase the sample size and follow up duration for deeper understanding of the factors that effecting the GU and GI complication in prostate cancer radiotherapy.

AIR Instrument Array

NASA Technical Reports Server (NTRS)

Jones, I. W.; Wilson, J. W.; Maiden, D. L.; Goldhagen, P.; Shinn, J. L.

2003-01-01

The large number of radiation types composing the atmospheric radiation requires a complicated combination of instrument types to fully characterize the environment. A completely satisfactory combination has not as yet been flown and would require a large capital outlay to develop. In that the funds of the current project were limited to essential integration costs, an international collaboration was formed with partners from six countries and fourteen different institutions with their own financial support for their participation. Instruments were chosen to cover sensitivity to all radiation types with enough differential sensitivity to separate individual components. Some instruments were chosen as important to specify the physical field component and other instruments were chosen on the basis that they could be useful in dosimetric evaluation. In the present paper we will discuss the final experimental flight package for the ER-2 flight campaign.

Steady state or non-steady state? Identifying driving mechanisms of oxygen isotope signatures of leaf transpiration in functionally distinct plant species

NASA Astrophysics Data System (ADS)

Dubbert, Maren; Kübert, Angelika; Cuntz, Matthias; Werner, Christiane

2015-04-01

Isotope techniques are widely applied in ecosystem studies. For example, isoflux models are used to separate soil evaporation from transpiration in ecosystems. These models often assume that plant transpiration occurs at isotopic steady state, i.e. that the transpired water shows the same isotopic signature as the source water. Yet, several studies found that transpiration did not occur at isotopic steady state, under both controlled and field conditions. Here we focused on identifying the internal and external factors which drive the isotopic signature of leaf transpiration. Using cavity ring-down spectroscopy (CRDS), the effect of both environmental variables and leaf physiological traits on δ18OT was investigated under controlled conditions. Six plant species with distinct leaf physiological traits were exposed to step changes in relative air humidity (RH), their response in δ18OT and gas exchange parameters and their leaf physiological traits were assessed. Moreover, two functionally distinct plant types (tree, i.e. Quercus suber, and grassland) of a semi-arid Mediterranean oak-woodland where observed under natural conditions throughout an entire growth period in the field. The species differed substantially in their leaf physiological traits and their turn-over times of leaf water. They could be grouped in species with fast (<60 min.), intermediate (ca. 120 min.) and slow (>240 min.) turn-over times, mostly due to differences in stomatal conductance, leaf water content or a combination of both. Changes in RH caused an immediate response in δ18OT, which were similarly strong in all species, while leaf physiological traits affected the subsequent response in δ18OT. The turn-over time of leaf water determined the speed of return to the isotopic steady or a stable δ18OT value (Dubbert & Kübert et al., in prep.). Under natural conditions, changes in environmental conditions over the diurnal cycle had a huge impact on the diurnal development of δ18OT in both observed plant functional types. However, in accordance with our findings in the lab, species specific differences in the leaf water turn over time, significantly influenced the amount of time plants transpired at non-steady state during the day (Dubbert et al., 2013, 2014). Our results emphasize the significance of considering isotopic non-steady state of transpiration and specifically to account for the specific differences of plant species resulting from distinct physiological traits of their leaves when applying isoflux models in ecosystem studies. Dubbert, M; Cuntz, M; Piayda, A; Maguas, C; Werner, C: Partitioning evapotranspiration - Testing the Craig and Gordon model with field measurements of oxygen isotope ratios of evaporative fluxes. J Hydrol (2013) Dubbert, M; Piayda, A; Cuntz, M; Correia, AC; Costa e Silva, F; Pereira, JS; Werner, C: Stable oxygen isotope and flux partitioning demonstrates understory of an oak savanna contributes up to half of ecosystem carbon and water exchange, Frontiers in Plant Science (2014a)

Functional Groups Based on Leaf Physiology: Are they Spatially and Temporally Robust?

NASA Technical Reports Server (NTRS)

Foster, Tammy E.; Brooks, J. Renee; Quincy, Charles (Technical Monitor)

2002-01-01

The functional grouping hypothesis, which suggests that complexity in function can be simplified by grouping species with similar responses, was tested in the Florida scrub habitat. Functional groups were identified based on how species in fire maintained FL scrub function in terms of carbon, water and nitrogen dynamics. The suite of physiologic parameters measured to determine function included both instantaneous gas exchange measurements obtained from photosynthetic light response curves and integrated measures of function. Using cluster analysis, five distinct physiologically-based functional groups were identified. Using non-parametric multivariate analyses, it was determined that these five groupings were not altered by plot differences or by the three different management regimes; prescribed burn, mechanically treated and burn, and fire-suppressed. The physiological groupings also remained robust between the two years 1999 and 2000. In order for these groupings to be of use for scaling ecosystem processes, there needs to be an easy-to-measure morphological indicator of function. Life form classifications were able to depict the physiological groupings more adequately than either specific leaf area or leaf thickness. THe ability of life forms to depict the groupings was improved by separating the parasitic Ximenia americana from the shrub category.

HPLC method for measurement of human salivary α-amylase inhibition by aqueous plant extracts.

PubMed

Takács, István; Takács, Ákos; Pósa, Anikó; Gyémánt, Gyöngyi

2017-06-01

Control of hyperglycemia is an important treatment in metabolic disorders such as type II diabetes and obesity. α-Amylase, as the first enzyme of glucose release from dietary polysaccharides, is a potential target to identify new sources of novel anti-obesity and anti-diabetic drugs. In this work, different herbal extracts as α-amylase inhibitors were studied by measuring the rate of the cleavage of a maltooligomer substrate 2-chloro-4-nitrophenyl-β-D-maltoheptoside. Measurement of chromophore containing products after reversed phase HPLC separation was used for α-amylase activity measurement. Rates of hydrolysis catalysed by human salivary α-amylase were determined in the presence and absence of lyophilised water extracts of eleven herbs. Remarkable bioactivities were found for extracts of Cinnamomum zeylanicum Blume (bark), Camellia sinensis L. (leaf), Ribes nigrum L. (leaf), Laurus nobilis L. (leaf), Vaccinium macrocarpon Aiton (fruit) and Syzygium aromaticum L. (bud). Determined IC 50 values were in 0.017-41 μg/ml range for these six selected plant extracts. Our results confirm the applicability of this HPLC-based method for the quick and reliable comparison of plants as α-amylase inhibitors.

Proteomic Analysis of the Salt-Responsive Leaf and Root Proteins in the Anticancer Plant Andrographis paniculata Nees

PubMed Central

Rafii, Mohd Yusop; Maziah, Mahmood

2014-01-01

Separation of proteins based on the physicochemical properties with different molecular weight and isoelectric points would be more accurate. In the current research, the 45-day-old seedlings were treated with 0 (control) and 12 dS m−1 of sodium chloride in the hydroponic system. After 15 days of salt exposure, the total protein of the fresh leaves and roots was extracted and analyzed using two-dimensional electrophoresis system (2-DE). The analysis led to the detection of 32 induced proteins (19 proteins in leaf and 13 proteins in the root) as well as 12 upregulated proteins (four proteins in leaf and eight proteins in the root) in the salt-treated plants. Of the 44 detected proteins, 12 were sequenced, and three of them matched with superoxide dismutase, ascorbate peroxidase and ribulose-1, 5-bisphosphate oxygenase whereas the rest remained unknown. The three known proteins associate with plants response to environmental stresses and could represent the general stress proteins in the present study too. In addition, the proteomic feedback of different accessions of A. paniculata to salt stress can potentially be used to breed salt-tolerant varieties of the herb. PMID:25423252

Biogeographic variation of foliar n-alkanes of Juniperus communis var. saxatilis Pallas from the Balkans.

PubMed

Rajčević, Nemanja; Janaćković, Pedja; Dodoš, Tanja; Tešević, Vele; Marin, Petar D

2014-12-01

The composition of the epicuticular n-alkanes isolated from the leaves of ten populations of Juniperus communis L. var. saxatilis Pallas from central (continental) and western (coastal) areas of the Balkan Peninsula was characterized by GC-FID and GC/MS analyses. In the leaf waxes, 14 n-alkane homologues with chain-lengths ranging from C22 to C35 were identified. All samples were dominated by n-tritriacontane (C33 ), but differences in two other dominant n-alkanes allowed separating the coastal from the continental populations. Several statistical methods (ANOVA, principal component, discriminant, and cluster analyses as well as the Mantel test) were deployed to analyze the diversity and variability of the epicuticular-leaf-n-alkane patterns of the ten natural populations of J. communis var. saxatilis and their relation to different geographic and bioclimatic parameters. Cluster analysis showed a high correlation of the leaf-n-alkane patterns with the geographical distribution of the investigated samples, differentiating the coastal from the continental populations of this taxon. Several bioclimatic parameters related to aridity were highly correlated with this differentiation. Copyright © 2014 Verlag Helvetica Chimica Acta AG, Zürich.

[Characterization of the damage of Spodoptera eridania (Cramer) and Spodoptera cosmioides (Walker) (Lepidoptera: Noctuidae) to structures of cotton plants].

PubMed

Santos, Karen B Dos; Meneguim, Ana M; Santos, Walter J Dos; Neves, Pedro M O J; Santos, Rachel B Dos

2010-01-01

The cotton plant, Gossypium hirsutum, hosts various pests that damage different structures. Among these pests, Spodoptera cosmioides (Walker) and Spodoptera eridania (Cramer) (Lepidoptera: Noctuidae) are considered important. The objectives of this study were to characterize and to quantify the potential damage of S. eridania and S. cosmioides feeding on different structures of cotton plants. For this purpose, newly-hatched larvae were reared on the following plant parts: leaf and flower bud; leaf and boll; flower bud or boll; and leaf, flower bud and boll. The survival of S. cosmioides and S. eridania was greater than 80% and 70% for larvae fed on cotton plant parts offered separately or together, respectively. One larva of S. eridania damaged 1.7 flower buds, but did not damage bolls, while one larva of S. cosmioides damaged 5.2 flower buds and 3.0 cotton bolls. Spodoptera eridania and S. cosmioides can be considered species with potential to cause economic damage to cotton plants because they can occur throughout cotton developmental stages causing defoliation and losses of reproductive structures. Therefore, the results validate field observations that these two species of Spodoptera are potential pests for cotton.

Effect of guava (Psidium guajava L.) leaf extract on glucose uptake in rat hepatocytes.

PubMed

Cheng, Fang-Chi; Shen, Szu-Chuan; Wu, James Swi-Bea

2009-06-01

People in oriental countries, including Japan and Taiwan, boil guava leaves (Psidium guajava L.) in water and drink the extract as a folk medicine for diabetes. The present study investigated the enhancement of aqueous guava leaf extract on glucose uptake in rat clone 9 hepatocytes and searched for the active compound. The extract was eluted with MeOH-H(2)O solutions through Diaion, Sephadex, and MCI-gel columns to separate into fractions with different polarities. The uptake test of 2-[1-(14)C] deoxy-D-glucose in rat clone 9 hepatocytes was performed to evaluate the hypoglycemic effect of these fractions. The active compound was identified by nuclear magnetic resonance analysis and high-performance liquid chromatography (HPLC). The results revealed that phenolics are the principal component of the extract, that high polarity fractions of the guava leaf extract are enhancers to glucose uptake in rat clone 9 hepatocytes, and that quercetin is the major active compound. We suggest that quercetin in the aqueous extract of guava leaves promotes glucose uptake in liver cells, and contributes to the alleviation of hypoglycemia in diabetes as a consequence.

GDP-L-fucose is required for boundary definition in plants.

PubMed

Gonçalves, Beatriz; Maugarny-Calès, Aude; Adroher, Bernard; Cortizo, Millán; Borrega, Nero; Blein, Thomas; Hasson, Alice; Gineau, Emilie; Mouille, Grégory; Laufs, Patrick; Arnaud, Nicolas

2017-12-16

The CUP-SHAPED COTYLEDON (CUC) transcription factors control plant boundary formation, thus allowing the emergence of novel growth axes. While the developmental roles of the CUC genes in different organs and across species are well characterized, upstream and downstream events that contribute to their function are still poorly understood. To identify new players in this network, we performed a suppressor screen of CUC2g-m4, a line overexpressing CUC2 that has highly serrated leaves. We identified a mutation that simplifies leaf shape and affects MURUS1 (MUR1), which is responsible for GDP-L-fucose production. Using detailed morphometric analysis, we show that GDP-L-fucose has an essential role in leaf shape acquisition by sustaining differential growth at the leaf margins. Accordingly, reduced CUC2 expression levels are observed in mur1 leaves. Furthermore, genetic analyses reveal a conserved role for GDP-L-fucose in different developmental contexts where it contributes to organ separation in the same pathway as CUC2. Taken together, our results reveal that GDP-L-fucose is necessary for proper establishment of boundary domains in various developmental contexts. © The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology.

A New Canopy Integration Factor

NASA Astrophysics Data System (ADS)

Badgley, G.; Anderegg, L. D. L.; Baker, I. T.; Berry, J. A.

2017-12-01

Ecosystem modelers have long debated how to best represent within-canopy heterogeneity. Can one big leaf represent the full range of canopy physiological responses? Or you need two leaves - sun and shade - to get things right? Is it sufficient to treat the canopy as a diffuse medium? Or would it be better to explicitly represent separate canopy layers? These are open questions that have been subject of an enormous amount of research and scrutiny. Yet regardless of how the canopy is represented, each model must grapple with correctly parameterizing its canopy in a way that properly translates leaf-level processes to the canopy and ecosystem scale. We present a new approach for integrating whole-canopy biochemistry by combining remote sensing with ecological theory. Using the Simple Biosphere model (SiB), we redefined how SiB scales photosynthetic processes from leaf-to-canopy as a function of satellite-derived measurements of solar-induced chlorophyll fluorescence (SIF). Across multiple long-term study sites, our approach improves the accuracy of daily modeled photosynthesis by as much as 25 percent. We share additional insights on how SIF might be more directly integrated into photosynthesis models, as well as present ideas for harnessing SIF to more accurately parameterize canopy biochemical variables.

The DosiMap, a new 2D scintillating dosimeter for IMRT quality assurance: characterization of two Cerenkov discrimination methods.

PubMed

Frelin, A M; Fontbonne, J M; Ban, G; Colin, J; Labalme, M; Batalla, A; Vela, A; Boher, P; Braud, M; Leroux, T

2008-05-01

New radiation therapy techniques such as IMRT present significant efficiency due to their highly conformal dose distributions. A consequence of the complexity of their dose distributions (high gradients, small irradiation fields, low dose distribution, ...) is the requirement for better precision quality assurance than in classical radiotherapy in order to compare the conformation of the delivered dose with the planned dose distribution and to guarantee the quality of the treatment. Currently this control is mostly performed by matrices of ionization chambers, diode detectors, dosimetric films, portal imaging, or dosimetric gels. Another approach is scintillation dosimetry, which has been developed in the last 15 years mainly through scintillating fiber devices. Despite having many advantages over other methods it is still at an experimental level for routine dosimetry because the Cerenkov radiation produced under irradiation represents an important stem effect. A new 2D water equivalent scintillating dosimeter, the DosiMap, and two different Cerenkov discrimination methods were developed with the collaboration of the Laboratoire de Physique Corpusculaire of Caen, the Comprehensive Cancer Center François Baclesse, and the ELDIM Co., in the frame of the MAESTRO European project. The DosiMap consists of a plastic scintillating sheet placed inside a transparent polystyrene phantom. The light distribution produced under irradiation is recorded by a CCD camera. Our first Cerenkov discrimination technique is subtractive. It uses a chessboard pattern placed in front of the scintillator, which provides a background signal containing only Cerenkov light. Our second discrimination technique is colorimetric. It performs a spectral analysis of the light signal, which allows the unfolding of the Cerenkov radiation and the scintillation. Tests were carried out with our DosiMap prototype and the performances of the two discrimination methods were assessed. The comparison of the dose measurements performed with the DosiMap and with dosimetric films for three different irradiation configurations showed discrepancies smaller than 3.5% for a 2 mm spatial resolution. Two innovative discrimination solutions were demonstrated to separate the scintillation from the Cerenkov radiation. It was also shown that the DosiMap, which is water equivalent, fast, and user friendly, is a very promising tool for radiotherapy quality assurance.

Thin Layer Chromatography-Bioautography and Gas Chromatography-Mass Spectrometry of Antimicrobial Leaf Extracts from Philippine Piper betle L. against Multidrug-Resistant Bacteria.

PubMed

Valle, Demetrio L; Puzon, Juliana Janet M; Cabrera, Esperanza C; Rivera, Windell L

2016-01-01

This study isolated and identified the antimicrobial compounds of Philippine Piper betle L. leaf ethanol extracts by thin layer chromatography- (TLC-) bioautography and gas chromatography-mass spectrometry (GC-MS). Initially, TLC separation of the leaf ethanol extracts provided a maximum of eight compounds with R f values of 0.92, 0.86, 0.76, 0.53, 0.40, 0.25, 0.13, and 0.013, best visualized when inspected under UV 366 nm. Agar-overlay bioautography of the isolated compounds demonstrated two spots with R f values of 0.86 and 0.13 showing inhibitory activities against two Gram-positive multidrug-resistant (MDR) bacteria, namely, methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus. The compound with an R f value of 0.86 also possessed inhibitory activity against Gram-negative MDR bacteria, namely, carbapenem-resistant Enterobacteriaceae-Klebsiella pneumoniae and metallo-β-lactamase-producing Acinetobacter baumannii. GC-MS was performed to identify the semivolatile and volatile compounds present in the leaf ethanol extracts. Six compounds were identified, four of which are new compounds that have not been mentioned in the medical literature. The chemical compounds isolated include ethyl diazoacetate, tris(trifluoromethyl)phosphine, heptafluorobutyrate, 3-fluoro-2-propynenitrite, 4-(2-propenyl)phenol, and eugenol. The results of this study could lead to the development of novel therapeutic agents capable of dealing with specific diseases that either have weakened reaction or are currently not responsive to existing drugs.

Thin Layer Chromatography-Bioautography and Gas Chromatography-Mass Spectrometry of Antimicrobial Leaf Extracts from Philippine Piper betle L. against Multidrug-Resistant Bacteria

PubMed Central

Valle, Demetrio L.; Puzon, Juliana Janet M.; Cabrera, Esperanza C.

2016-01-01

This study isolated and identified the antimicrobial compounds of Philippine Piper betle L. leaf ethanol extracts by thin layer chromatography- (TLC-) bioautography and gas chromatography-mass spectrometry (GC-MS). Initially, TLC separation of the leaf ethanol extracts provided a maximum of eight compounds with R f values of 0.92, 0.86, 0.76, 0.53, 0.40, 0.25, 0.13, and 0.013, best visualized when inspected under UV 366 nm. Agar-overlay bioautography of the isolated compounds demonstrated two spots with R f values of 0.86 and 0.13 showing inhibitory activities against two Gram-positive multidrug-resistant (MDR) bacteria, namely, methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus. The compound with an R f value of 0.86 also possessed inhibitory activity against Gram-negative MDR bacteria, namely, carbapenem-resistant Enterobacteriaceae-Klebsiella pneumoniae and metallo-β-lactamase-producing Acinetobacter baumannii. GC-MS was performed to identify the semivolatile and volatile compounds present in the leaf ethanol extracts. Six compounds were identified, four of which are new compounds that have not been mentioned in the medical literature. The chemical compounds isolated include ethyl diazoacetate, tris(trifluoromethyl)phosphine, heptafluorobutyrate, 3-fluoro-2-propynenitrite, 4-(2-propenyl)phenol, and eugenol. The results of this study could lead to the development of novel therapeutic agents capable of dealing with specific diseases that either have weakened reaction or are currently not responsive to existing drugs. PMID:27478476

Reproduction reduces photosynthetic capacity in females of the subdioecious Honckenya peploides

NASA Astrophysics Data System (ADS)

Sánchez-Vilas, Julia; Retuerto, Rubén

2011-03-01

As a consequence of the different reproductive functions performed by the sexes, sexually dimorphic/polymorphic plants may exhibit gender-related variations in the energy and resources allocated to reproduction, and in the physiological processes that underlie these differences. This study investigated whether the sexes of the subdioecious plant Honckenya peploides differ in ecophysiological traits related to photosynthetic capacity and whether possible differences depend on reproductive status and on the plant's position (edge or centre) in the population. We registered in three sites in NW Spain, the sex and density of shoots of two segregated clumps of plants. These clumps represent an extreme case of sex-ratio variation across space, with separated single-sex clumps of plants. In two of these sites we measured photosynthetic efficiencies, chlorophyll content, and specific leaf areas. In females, reproduction reduced photochemical efficiency, chlorophyll content and increased the specific leaf area, which is a key leaf trait related to photosynthetic capacity. In males, no differences due to reproduction were detected. The position within the clump affected the specific leaf area of the shoots, with shoots growing at the edge having the lowest values, regardless of the sex. Finally, the effects of position in photosynthetic efficiency and chlorophyll content where highly variable among clumps. We conclude that the differential effects of reproduction on sexes may entail different costs that could be crucial in the outcome of interactions between them, contributing to their spatial segregation.

Method optimization for proteomic analysis of soybean leaf: Improvements in identification of new and low-abundance proteins

PubMed Central

Mesquita, Rosilene Oliveira; de Almeida Soares, Eduardo; de Barros, Everaldo Gonçalves; Loureiro, Marcelo Ehlers

2012-01-01

The most critical step in any proteomic study is protein extraction and sample preparation. Better solubilization increases the separation and resolution of gels, allowing identification of a higher number of proteins and more accurate quantitation of differences in gene expression. Despite the existence of published results for the optimization of proteomic analyses of soybean seeds, no comparable data are available for proteomic studies of soybean leaf tissue. In this work we have tested the effects of modification of a TCA-acetone method on the resolution of 2-DE gels of leaves and roots of soybean. Better focusing was obtained when both mercaptoethanol and dithiothreitol were used in the extraction buffer simultaneously. Increasing the number of washes of TCA precipitated protein with acetone, using a final wash with 80% ethanol and using sonication to ressuspend the pellet increased the number of detected proteins as well the resolution of the 2-DE gels. Using this approach we have constructed a soybean protein map. The major group of identified proteins corresponded to genes of unknown function. The second and third most abundant groups of proteins were composed of photosynthesis and metabolism related genes. The resulting protocol improved protein solubility and gel resolution allowing the identification of 122 soybean leaf proteins, 72 of which were not detected in other published soybean leaf 2-DE gel datasets, including a transcription factor and several signaling proteins. PMID:22802721

Combination of HPLC chromatogram and hypoglycemic effect identifies isoflavones as the principal active fraction of Belamcanda chinensis leaf extract in diabetes treatment.

PubMed

Chen, Yan; Wu, Chong-Ming; Dai, Rong-Ji; Li, Liang; Yu, Yu-Hong; Li, Yan; Meng, Wei-Wei; Zhang, Liang; Zhang, Yongqian; Deng, Yu-Lin

2011-02-15

In previous study, we demonstrated the hypoglycemic effect of aqueous extract of Belamcanda chinensis leaves in rats. Here, we separated the aqueous extract of B. chinensis leaves and investigated the spectrum-effect relationships between HPLC chromatograms and hypoglycemic activities of different isolates from B. chinensis leaf extract. Sequential solvent extraction with petroleum ether, chloroform, acetic ester and n-butanol provided several isolates showing similar hypoglycemic activities, making it difficult to discriminate the active fractions. Stepwise elution through HP20 macroporous resin by water, 40% and 95% ethanol provided isolates with distinct hypoglycemic activities, representing a simple, rapid and efficient preparative separation method. Combination of HPLC chromatogram and pharmacological effect targeted a hypoglycemic activity-related region in HPLC chromatogram. Each peak in this region was analyzed by UV spectrum scan. Most of them were flavonoids in which tectoridin and swertisin were known flavonoids with anti-diabetic activities. In together, this work provides a general model of combination of HPLC chromatography and pharmacological effect to study the spectrum-effect relationships of aqueous extract from B. chinensis leaves, which can be used to find principle components of B. chinensis on pharmacological activity. Copyright © 2011 Elsevier B.V. All rights reserved.

X-Ray Attenuation and Absorption for Materials of Dosimetric Interest

National Institute of Standards and Technology Data Gateway

SRD 126 X-Ray Attenuation and Absorption for Materials of Dosimetric Interest (Web, free access)   Tables and graphs of the photon mass attenuation coefficient and the mass energy-absorption coefficient are presented for all of the elements Z = 1 to 92, and for 48 compounds and mixtures of radiological interest. The tables cover energies of the photon (x-ray, gamma ray, bremsstrahlung) from 1 keV to 20 MeV.

Potential dosimetric benefit of dose-warping based 4D planning compared to conventional 3D planning in liver stereotactic body radiotherapy (SBRT)

NASA Astrophysics Data System (ADS)

Yeo, U. J.; Taylor, M. L.; Kron, T.; Pham, D.; Siva, S.; Franich, R. D.

2013-06-01

Respiratory motion induces dosimetric uncertainties for thoracic and abdominal cancer radiotherapy (RT) due to deforming and moving anatomy. This study investigates the extent of dosimetric differences between conventional 3D treatment planning and path-integrated 4D treatment planning in liver stereotactic body radiotherapy (SBRT). Respiratory-correlated 4DCT image sets with 10 phases were acquired for patients with liver tumours. Path-integrated 4D dose accumulation was performed using dose-warping techniques based on deformable image registration. Dose-volume histogram analysis demonstrated that the 3D planning approach overestimated doses to targets by up to 24% and underestimated dose to normal liver by ~4.5%, compared to the 4D planning methodology. Therefore, 4D planning has the potential to quantify such issues of under- and/or over-dosage and improve treatment accuracy.

The work of the ICRP dose calculational task group: Issues in implementation of the ICRP dosimetric methodology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eckerman, K.F.

Committee 2 of the International Commission on Radiological Protection (ICRP) has had efforts underway to provide the radiation protection community with age-dependent dose coefficients, i.e.g, the dose per unit intake. The Task Group on Dose Calculations, chaired by the author, is responsible for the computation of these coefficients. The Task Group, formed in 1974 to produce ICRP Publication 30, is now international in its membership and its work load has been distributed among the institutions represented on the task group. This paper discusses: (1) recent advances in biokinetic modeling; (2) the recent changes in the dosimetric methodology; (3) the novelmore » computational problems with some of the ICRP quantities; and (4) quality assurance issues which the Task Group has encountered. Potential future developments of the dosimetric framework which might strengthen the relationships with the emerging understanding of radiation risk will also be discussed.« less

2D dose distribution images of a hybrid low field MRI-γ detector

NASA Astrophysics Data System (ADS)

Abril, A.; Agulles-Pedrós, L.

2016-07-01

The proposed hybrid system is a combination of a low field MRI and dosimetric gel as a γ detector. The readout system is based on the polymerization process induced by the gel radiation. A gel dose map is obtained which represents the functional part of hybrid image alongside with the anatomical MRI one. Both images should be taken while the patient with a radiopharmaceutical is located inside the MRI system with a gel detector matrix. A relevant aspect of this proposal is that the dosimetric gel has never been used to acquire medical images. The results presented show the interaction of the 99mTc source with the dosimetric gel simulated in Geant4. The purpose was to obtain the planar γ 2D-image. The different source configurations are studied to explore the ability of the gel as radiation detector through the following parameters; resolution, shape definition and radio-pharmaceutical concentration.

Geometric and dosimetric evaluations of atlas-based segmentation methods of MR images in the head and neck region.

PubMed

Kieselmann, Jennifer Petra; Kamerling, Cornelis Philippus; Burgos, Ninon; Menten, Martin J; Fuller, Clifton David; Nill, Simeon; Cardoso, M Jorge; Oelfke, Uwe

2018-06-08

Owing to its excellent soft-tissue contrast, magnetic resonance (MR) imaging has found an increased application in radiation therapy (RT). Harnessing these properties for treatment planning, automated segmentation methods can alleviate the manual workload burden to the clinical workflow. We investigated atlas-based segmentation methods of organs at risk (OARs) in the head and neck (H&N) region: one approach selecting the most similar atlas from a library of segmented images and two multi-atlas approaches. The latter were based on weighted majority voting and an iterative atlas-fusion approach called STEPS. We built the atlas library from pre-treatment T1-weighted MR images of 12 patients with manual contours of the parotids, spinal cord and mandible, delineated by a clinician. Following a leave-one-out cross-validation strategy, we measured geometric accuracy calculating Dice similarity coefficients (DSC), standard and 95% Hausdorff distances (HD and HD95), as well as the mean surface distance (MSD), whereby the manual contours served as the gold standard. To benchmark the algorithm, we determined the inter-expert variability (IEV) between three experts. To investigate the dosimetric effect of segmentation inaccuracies, we implemented an auto-planning strategy within the treatment planning system Monaco (Elekta AB, Stockholm, Sweden). For each set of auto-segmented volumes of interest (VOIs), we generated a plan for a 9-beam step and shoot intensity modulated RT treatment, designed according to our institution's clinical H\\&N protocol. Superimposing the dose distributions on the gold standard VOIs, we calculated dose differences to OARs caused by contouring differences between auto-segmented and gold standard VOIs. We investigated the correlation between geometric and dosimetric differences. The mean DSC was larger than 0.8 and the mean MSD smaller than 2mm for the multi-atlas approaches, resulting in a geometric accuracy comparable to previously published results and within the range of the IEV. While dosimetric differences could be as large as 23% of the clinical goal, treatment plans fulfilled all imposed clinical goals for the gold standard OARs. Correlations between geometric and dosimetric measures were low with R²<0.5. The geometric accuracy and ability to achieve clinically acceptable treatment plans indicate the suitability of using atlas-based contours for RT treatment planning purposes. The low correlations between geometric and dosimetric measures indicate that geometric measures alone are not sufficient to predict the dosimetric impact of segmentation inaccuracies on treatment planning for the data utilised in this study. Creative Commons Attribution license.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crijns, Wouter, E-mail: wouter.crijns@uzleuven.be; Depuydt, Tom; Haustermans, Karin

Purpose: To evaluate three different plan adaptation strategies using 3D film-stack dose measurements of both focal boost and hypofractionated prostate VMAT treatments. The adaptation strategies (a couch shift, geometric tracking, and dosimetric tracking) were applied for three realistic intrafraction prostate motions. Methods: A focal boost (35 × 2.2 and 35 × 2.7 Gy) and a hypofractionated (5 × 7.25 Gy) prostate VMAT plan were created for a heterogeneous phantom that allows for internal prostate motion. For these plans geometric tracking and dosimetric tracking were evaluated by ionization chamber (IC) point dose measurements (zero-D) and measurements using a stack of EBT3more » films (3D). The geometric tracking applied translations, rotations, and scaling of the MLC aperture in response to realistic prostate motions. The dosimetric tracking additionally corrected the monitor units to resolve variations due to difference in depth, tissue heterogeneity, and MLC-aperture. The tracking was based on the positions of four fiducial points only. The film measurements were compared to the gold standard (i.e., IC measurements) and the planned dose distribution. Additionally, the 3D measurements were converted to dose volume histograms, tumor control probability, and normal tissue complication probability parameters (DVH/TCP/NTCP) as a direct estimate of clinical relevance of the proposed tracking. Results: Compared to the planned dose distribution, measurements without prostate motion and tracking showed already a reduced homogeneity of the dose distribution. Adding prostate motion further blurs the DVHs for all treatment approaches. The clinical practice (no tracking) delivered the dose distribution inside the PTV but off target (CTV), resulting in boost dose errors up to 10%. The geometric and dosimetric tracking corrected the dose distribution’s position. Moreover, the dosimetric tracking could achieve the planned boost DVH, but not the DVH of the more homogeneously irradiated prostate. A drawback of both the geometric and dosimetric tracking was a reduced MLC blocking caused by the rotational component of the MLC aperture corrections. Because of the used CTV to PTV margins and the high doses in the considered fractionation schemes, the TCP differed less than 0.02 from the planned value for all targets and all correction methods. The rectal NTCP constraints, however, could not be realized using any of these methods. Conclusions: The geometric and dosimetric tracking use only a limited input, but they deposit the dose distribution with higher geometric accuracy than the clinical practice. The latter case has boost dose errors up to 10%. The increased accuracy has a modest impact [Δ(NT)CP < 0.02] because of the applied margins and the high dose levels used. To allow further margin reduction tracking methods are vital. The proposed methodology could further be improved by implementing a rotational correction using collimator rotations.« less

The artificial leaf.

PubMed

Nocera, Daniel G

2012-05-15

To convert the energy of sunlight into chemical energy, the leaf splits water via the photosynthetic process to produce molecular oxygen and hydrogen, which is in a form of separated protons and electrons. The primary steps of natural photosynthesis involve the absorption of sunlight and its conversion into spatially separated electron-hole pairs. The holes of this wireless current are captured by the oxygen evolving complex (OEC) of photosystem II (PSII) to oxidize water to oxygen. The electrons and protons produced as a byproduct of the OEC reaction are captured by ferrodoxin of photosystem I. With the aid of ferrodoxin-NADP(+) reductase, they are used to produce hydrogen in the form of NADPH. For a synthetic material to realize the solar energy conversion function of the leaf, the light-absorbing material must capture a solar photon to generate a wireless current that is harnessed by catalysts, which drive the four electron/hole fuel-forming water-splitting reaction under benign conditions and under 1 sun (100 mW/cm(2)) illumination. This Account describes the construction of an artificial leaf comprising earth-abundant elements by interfacing a triple junction, amorphous silicon photovoltaic with hydrogen- and oxygen-evolving catalysts made from a ternary alloy (NiMoZn) and a cobalt-phosphate cluster (Co-OEC), respectively. The latter captures the structural and functional attributes of the PSII-OEC. Similar to the PSII-OEC, the Co-OEC self-assembles upon oxidation of an earth-abundant metal ion from 2+ to 3+, may operate in natural water at room temperature, and is self-healing. The Co-OEC also activates H(2)O by a proton-coupled electron transfer mechanism in which the Co-OEC is increased by four hole equivalents akin to the S-state pumping of the Kok cycle of PSII. X-ray absorption spectroscopy studies have established that the Co-OEC is a structural relative of Mn(3)CaO(4)-Mn cubane of the PSII-OEC, where Co replaces Mn and the cubane is extended in a corner-sharing, head-to-tail dimer. The ability to perform the oxygen-evolving reaction in water at neutral or near-neutral conditions has several consequences for the construction of the artificial leaf. The NiMoZn alloy may be used in place of Pt to generate hydrogen. To stabilize silicon in water, its surface is coated with a conducting metal oxide onto which the Co-OEC may be deposited. The net result is that immersing a triple-junction Si wafer coated with NiMoZn and Co-OEC in water and holding it up to sunlight can effect direct solar energy conversion via water splitting. By constructing a simple, stand-alone device composed of earth-abundant materials, the artificial leaf provides a means for an inexpensive and highly distributed solar-to-fuels system that employs low-cost systems engineering and manufacturing. Through this type of system, solar energy can become a viable energy supply to those in the non-legacy world.

TH-AB-202-03: A Novel Tool for Computing Deliverable Doses in Dynamic MLC Tracking Treatments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fast, M; Kamerling, C; Menten, M

2016-06-15

Purpose: In tracked dynamic multi-leaf collimator (MLC) treatments, segments are continuously adapted to the target centroid motion in beams-eye-view. On-the-fly segment adaptation, however, potentially induces dosimetric errors due to the finite MLC leaf width and non-rigid target motion. In this study, we outline a novel tool for computing the 4d dose of lung SBRT plans delivered with MLC tracking. Methods: The following automated workflow was developed: A) centroid tracking, where the initial segments are morphed to each 4dCT phase based on the beams-eye-view GTV shift (followed by a dose calculation on each phase); B) re-optimized tracking, in which all morphedmore » initial plans from (A) are further optimised (“warm-started”) in each 4dCT phase using the initial optimisation parameters but phase-specific volume definitions. Finally, both dose sets are accumulated to the reference phase using deformable image registration. Initial plans were generated according to the RTOG-1021 guideline (54Gy, 3-Fx, equidistant 9-beam IMRT) on the peak-exhale (reference) phase of a phase-binned 4dCT. Treatment planning and delivery simulations were performed in RayStation (research v4.6) using our in-house segment-morphing algorithm, which directly links to RayStation through a native C++ interface. Results: Computing the tracking plans and 4d dose distributions via the in-house interface takes 5 and 8 minutes respectively for centroid and re-optimized tracking. For a sample lung SBRT patient with 14mm peak-to-peak motion in sup-inf direction, mainly perpendicular leaf motion (0-collimator) resulted in small dose changes for PTV-D95 (−13cGy) and GTV-D98 (+18cGy) for the centroid tracking case compared to the initial plan. Modest reductions of OAR doses (e.g. spinal cord D2: −11cGy) were achieved in the idealized tracking case. Conclusion: This study presents an automated “1-click” workflow for computing deliverable MLC tracking doses in RayStation. Adding a non-deliverable re-optimized tracking scenario is expected to help quantify plan robustness for more challenging patients with anatomy deformations. We acknowledge support of the MLC tracking research from Elekta AB. MFF is supported by Cancer Research UK under Programme C33589/A19908. Research at ICR is also supported by Cancer Research UK under Programme C33589/A19727 and NHS funding to the NIHR Biomedical Research Centre at RMH and ICR.« less

Using measurable dosimetric quantities to characterize the inter-structural tradeoff in inverse planning

NASA Astrophysics Data System (ADS)

Liu, Hongcheng; Dong, Peng; Xing, Lei

2017-08-01

Traditional inverse planning relies on the use of weighting factors to balance the conflicting requirements of different structures. Manual trial-and-error determination of weighting factors has long been recognized as a time-consuming part of treatment planning. The purpose of this work is to develop an inverse planning framework that parameterizes the dosimetric tradeoff among the structures with physically meaningful quantities to simplify the search for clinically sensible plans. In this formalism, instead of using weighting factors, the permissible variation range of the prescription dose or dose volume histogram (DVH) of the involved structures are used to characterize the ‘importance’ of the structures. The inverse planning is then formulated into a convex feasibility problem, called the dosimetric variation-controlled model (DVCM), whose goal is to generate plans with dosimetric or DVH variations of the structures consistent with the pre-specified values. For simplicity, the dosimetric variation range for a structure is extracted from a library of previous cases which possess similar anatomy and prescription. A two-phase procedure (TPP) is designed to solve the model. The first phase identifies a physically feasible plan to satisfy the prescribed dosimetric variation, and the second phase automatically improves the plan in case there is room for further improvement. The proposed technique is applied to plan two prostate cases and two head-and-neck cases and the results are compared with those obtained using a conventional CVaR approach and with a moment-based optimization scheme. Our results show that the strategy is able to generate clinically sensible plans with little trial and error. In all cases, the TPP generates a very competitive plan as compared to those obtained using the alternative approaches. Particularly, in the planning of one of the head-and-neck cases, the TPP leads to a non-trivial improvement in the resultant dose distribution—the fractional volumes receiving a dose above 20 Gy for the spinal cord are reduced by more than 40% when compared to the alternative schemes, while maintaining the same PTV coverage. With physically more meaningful modeling of the inter-structural tradeoff, the reported technique enables us to substantially reduce the need for trial-and-error adjustment of the model parameters. The new formalism also opens new opportunities for incorporating prior knowledge to facilitate the treatment planning process.

Visualization of a variety of possible dosimetric outcomes in radiation therapy using dose-volume histogram bands.

PubMed

Trofimov, Alexei; Unkelbach, Jan; DeLaney, Thomas F; Bortfeld, Thomas

2012-01-01

Dose-volume histograms (DVH) are the most common tool used in the appraisal of the quality of a clinical treatment plan. However, when delivery uncertainties are present, the DVH may not always accurately describe the dose distribution actually delivered to the patient. We present a method, based on DVH formalism, to visualize the variability in the expected dosimetric outcome of a treatment plan. For a case of chordoma of the cervical spine, we compared 2 intensity modulated proton therapy plans. Treatment plan A was optimized based on dosimetric objectives alone (ie, desired target coverage, normal tissue tolerance). Plan B was created employing a published probabilistic optimization method that considered the uncertainties in patient setup and proton range in tissue. Dose distributions and DVH for both plans were calculated for the nominal delivery scenario, as well as for scenarios representing deviations from the nominal setup, and a systematic error in the estimate of range in tissue. The histograms from various scenarios were combined to create DVH bands to illustrate possible deviations from the nominal plan for the expected magnitude of setup and range errors. In the nominal scenario, the DVH from plan A showed superior dose coverage, higher dose homogeneity within the target, and improved sparing of the adjacent critical structure. However, when the dose distributions and DVH from plans A and B were recalculated for different error scenarios (eg, proton range underestimation by 3 mm), the plan quality, reflected by DVH, deteriorated significantly for plan A, while plan B was only minimally affected. In the DVH-band representation, plan A produced wider bands, reflecting its higher vulnerability to delivery errors, and uncertainty in the dosimetric outcome. The results illustrate that comparison of DVH for the nominal scenario alone does not provide any information about the relative sensitivity of dosimetric outcome to delivery uncertainties. Thus, such comparison may be misleading and may result in the selection of an inferior plan for delivery to a patient. A better-informed decision can be made if additional information about possible dosimetric variability is presented; for example, in the form of DVH bands. Copyright © 2012 American Society for Radiation Oncology. Published by Elsevier Inc. All rights reserved.

Effect of solvent polarity levels on separation of xanthone and coumarin from Calophyllum inophyllum leaves extract

NASA Astrophysics Data System (ADS)

Susanto, D. F.; Hapsari, S.; Trilutfiani, Z.; Borhet, A.; Aparamarta, H. W.; Widjaja, A.; Gunawan, S.

2018-03-01

Calophyllum inophyllum has various benefits that can be utilized from root, stem, leaf, until seed. C. inophyllum leaves contain many bioactive compounds, such as xanthone and coumarin which are useful as antioxidant, and inhibitors of enzyme activity from HIV virus. The aim of this research was to investigate the effect of solvent polarity levels on the separation of xanthone and coumarin compounds contained in the crude extract of C. inophyllum leaves. Crude leaves extract was obtained by percolation method. Moreover, Liquid Liquid Extraction (LLE) was used for separating xanthone and coumarin compounds. It was performed by methanol (polar solvent) and hexane (non-polar solvent) with solvent ratio of 1. Methanol concentration in water used were 20%, 50%, 80%, and 100%. Each fraction obtained was tested qualitatively using Thin Layer Chromatography (TLC) and quantitatively using Gas Chromatography (GC) to analyze xanthone and coumarin. The best separation result was obtained by using 50% methanol. In this results, coumarin and xanthones were separated in methanol fraction (81.18% recovery) and in hexane fraction (81.91% recovery), respectively.

Effect of photon energy spectrum on dosimetric parameters of brachytherapy sources.

PubMed

Ghorbani, Mahdi; Mehrpouyan, Mohammad; Davenport, David; Ahmadi Moghaddas, Toktam

2016-06-01

The aim of this study is to quantify the influence of the photon energy spectrum of brachytherapy sources on task group No. 43 (TG-43) dosimetric parameters. Different photon spectra are used for a specific radionuclide in Monte Carlo simulations of brachytherapy sources. MCNPX code was used to simulate 125I, 103Pd, 169Yb, and 192Ir brachytherapy sources. Air kerma strength per activity, dose rate constant, radial dose function, and two dimensional (2D) anisotropy functions were calculated and isodose curves were plotted for three different photon energy spectra. The references for photon energy spectra were: published papers, Lawrence Berkeley National Laboratory (LBNL), and National Nuclear Data Center (NNDC). The data calculated by these photon energy spectra were compared. Dose rate constant values showed a maximum difference of 24.07% for 103Pd source with different photon energy spectra. Radial dose function values based on different spectra were relatively the same. 2D anisotropy function values showed minor differences in most of distances and angles. There was not any detectable difference between the isodose contours. Dosimetric parameters obtained with different photon spectra were relatively the same, however it is suggested that more accurate and updated photon energy spectra be used in Monte Carlo simulations. This would allow for calculation of reliable dosimetric data for source modeling and calculation in brachytherapy treatment planning systems.

Effect of photon energy spectrum on dosimetric parameters of brachytherapy sources

PubMed Central

Ghorbani, Mahdi; Davenport, David

2016-01-01

Abstract Aim The aim of this study is to quantify the influence of the photon energy spectrum of brachytherapy sources on task group No. 43 (TG-43) dosimetric parameters. Background Different photon spectra are used for a specific radionuclide in Monte Carlo simulations of brachytherapy sources. Materials and methods MCNPX code was used to simulate 125I, 103Pd, 169Yb, and 192Ir brachytherapy sources. Air kerma strength per activity, dose rate constant, radial dose function, and two dimensional (2D) anisotropy functions were calculated and isodose curves were plotted for three different photon energy spectra. The references for photon energy spectra were: published papers, Lawrence Berkeley National Laboratory (LBNL), and National Nuclear Data Center (NNDC). The data calculated by these photon energy spectra were compared. Results Dose rate constant values showed a maximum difference of 24.07% for 103Pd source with different photon energy spectra. Radial dose function values based on different spectra were relatively the same. 2D anisotropy function values showed minor differences in most of distances and angles. There was not any detectable difference between the isodose contours. Conclusions Dosimetric parameters obtained with different photon spectra were relatively the same, however it is suggested that more accurate and updated photon energy spectra be used in Monte Carlo simulations. This would allow for calculation of reliable dosimetric data for source modeling and calculation in brachytherapy treatment planning systems. PMID:27247558

Four-dimensional computed tomography based respiratory-gated radiotherapy with respiratory guidance system: analysis of respiratory signals and dosimetric comparison.

PubMed

Lee, Jung Ae; Kim, Chul Yong; Yang, Dae Sik; Yoon, Won Sup; Park, Young Je; Lee, Suk; Kim, Young Bum

2014-01-01

To investigate the effectiveness of respiratory guidance system in 4-dimensional computed tomography (4 DCT) based respiratory-gated radiation therapy (RGRT) by comparing respiratory signals and dosimetric analysis of treatment plans. The respiratory amplitude and period of the free, the audio device-guided, and the complex system-guided breathing were evaluated in eleven patients with lung or liver cancers. The dosimetric parameters were assessed by comparing free breathing CT plan and 4 DCT-based 30-70% maximal intensity projection (MIP) plan. The use of complex system-guided breathing showed significantly less variation in respiratory amplitude and period compared to the free or audio-guided breathing regarding the root mean square errors (RMSE) of full inspiration (P = 0.031), full expiration (P = 0.007), and period (P = 0.007). The dosimetric parameters including V(5 Gy), V(10 Gy), V(20 Gy), V(30 Gy), V(40 Gy), and V(50 Gy) of normal liver or lung in 4 DCT MIP plan were superior over free breathing CT plan. The reproducibility and regularity of respiratory amplitude and period were significantly improved with the complex system-guided breathing compared to the free or the audio-guided breathing. In addition, the treatment plan based on the 4D CT-based MIP images acquired with the complex system guided breathing showed better normal tissue sparing than that on the free breathing CT.

Dosimetric verification of gated delivery of electron beams using a 2D ion chamber array

PubMed Central

Yoganathan, S. A.; Das, K. J. Maria; Raj, D. Gowtham; Kumar, Shaleen

2015-01-01

The purpose of this study was to compare the dosimetric characteristics; such as beam output, symmetry and flatness between gated and non-gated electron beams. Dosimetric verification of gated delivery was carried for all electron beams available on Varian CL 2100CD medical linear accelerator. Measurements were conducted for three dose rates (100 MU/min, 300 MU/min and 600 MU/min) and two respiratory motions (breathing period of 4s and 8s). Real-time position management (RPM) system was used for the gated deliveries. Flatness and symmetry values were measured using Imatrixx 2D ion chamber array device and the beam output was measured using plane parallel ion chamber. These detector systems were placed over QUASAR motion platform which was programmed to simulate the respiratory motion of target. The dosimetric characteristics of gated deliveries were compared with non-gated deliveries. The flatness and symmetry of all the evaluated electron energies did not differ by more than 0.7 % with respect to corresponding non-gated deliveries. The beam output variation of gated electron beam was less than 0.6 % for all electron energies except for 16 MeV (1.4 %). Based on the results of this study, it can be concluded that Varian CL2100 CD is well suitable for gated delivery of non-dynamic electron beams. PMID:26170552

Patient-specific dosimetric endpoints based treatment plan quality control in radiotherapy.

PubMed

Song, Ting; Staub, David; Chen, Mingli; Lu, Weiguo; Tian, Zhen; Jia, Xun; Li, Yongbao; Zhou, Linghong; Jiang, Steve B; Gu, Xuejun

2015-11-07

In intensity modulated radiotherapy (IMRT), the optimal plan for each patient is specific due to unique patient anatomy. To achieve such a plan, patient-specific dosimetric goals reflecting each patient's unique anatomy should be defined and adopted in the treatment planning procedure for plan quality control. This study is to develop such a personalized treatment plan quality control tool by predicting patient-specific dosimetric endpoints (DEs). The incorporation of patient specific DEs is realized by a multi-OAR geometry-dosimetry model, capable of predicting optimal DEs based on the individual patient's geometry. The overall quality of a treatment plan is then judged with a numerical treatment plan quality indicator and characterized as optimal or suboptimal. Taking advantage of clinically available prostate volumetric modulated arc therapy (VMAT) treatment plans, we built and evaluated our proposed plan quality control tool. Using our developed tool, six of twenty evaluated plans were identified as sub-optimal plans. After plan re-optimization, these suboptimal plans achieved better OAR dose sparing without sacrificing the PTV coverage, and the dosimetric endpoints of the re-optimized plans agreed well with the model predicted values, which validate the predictability of the proposed tool. In conclusion, the developed tool is able to accurately predict optimally achievable DEs of multiple OARs, identify suboptimal plans, and guide plan optimization. It is a useful tool for achieving patient-specific treatment plan quality control.

Development of patient-specific phantoms for verification of stereotactic body radiation therapy planning in patients with metallic screw fixation

NASA Astrophysics Data System (ADS)

Oh, Dongryul; Hong, Chae-Seon; Ju, Sang Gyu; Kim, Minkyu; Koo, Bum Yong; Choi, Sungback; Park, Hee Chul; Choi, Doo Ho; Pyo, Hongryull

2017-01-01

A new technique for manufacturing a patient-specific dosimetric phantom using three-dimensional printing (PSDP_3DP) was developed, and its geometrical and dosimetric accuracy was analyzed. External body contours and structures of the spine and metallic fixation screws (MFS) were delineated from CT images of a patient with MFS who underwent stereotactic body radiation therapy for spine metastasis. Contours were converted into a STereoLithography file format using in-house program. A hollow, four-section PSDP was designed and manufactured using three types of 3DP to allow filling with a muscle-equivalent liquid and insertion of dosimeters. To evaluate the geometrical accuracy of PSDP_3DP, CT images were obtained and compared with patient CT data for volume, mean density, and Dice similarity coefficient for contours. The dose distribution in the PSDP_3DP was calculated by applying the same beam parameters as for the patient, and the dosimetric characteristics of the PSDP_3DP were compared with the patient plan. The registered CT of the PSDP_3DP was well matched with that of the real patient CT in the axial, coronal, and sagittal planes. The physical accuracy and dosimetric characteristics of PSDP_3DP were comparable to those of a real patient. The ability to manufacture a PSDP representing an extreme patient condition was demonstrated.

Multispectral determination of vegetative cover in corn crop canopy

NASA Technical Reports Server (NTRS)

Stoner, E. R.; Baumgardner, M. F.

1972-01-01

The relationship between different amounts of vegetative ground cover and the energy reflected by corn canopies was investigated. Low altitude photography and an airborne multispectral scanner were used to measure this reflected energy. Field plots were laid out, representing four growth stages of corn. Two plot locations were chosen-on a very dark and a very light surface soil. Color and color infrared photographs were taken from a vertical distance of 10 m. Estimates of ground cover were made from these photographs and were related to field measurements of leaf area index. Ground cover could be predicted from leaf area index measurements by a second order equation. Microdensitometry and digitzation of the three separated dye layers of color infrared film showed that the near infrared dye layer is most valuable in ground cover determinations. Computer analysis of the digitized photography provided an accurate method of determining precent ground cover.

Tree Canopy Characterization for EO-1 Reflective and Thermal Infrared Validation Studies: Rochester, New York

NASA Technical Reports Server (NTRS)

Ballard, Jerrell R., Jr.; Smith, James A.

2002-01-01

The tree canopy characterization presented herein provided ground and tree canopy data for different types of tree canopies in support of EO-1 reflective and thermal infrared validation studies. These characterization efforts during August and September of 2001 included stem and trunk location surveys, tree structure geometry measurements, meteorology, and leaf area index (LAI) measurements. Measurements were also collected on thermal and reflective spectral properties of leaves, tree bark, leaf litter, soil, and grass. The data presented in this report were used to generate synthetic reflective and thermal infrared scenes and images that were used for the EO-1 Validation Program. The data also were used to evaluate whether the EO-1 ALI reflective channels can be combined with the Landsat-7 ETM+ thermal infrared channel to estimate canopy temperature, and also test the effects of separating the thermal and reflective measurements in time resulting from satellite formation flying.

Tissue distribution comparison between healthy and fatty liver rats after oral administration of hawthorn leaf extract.

PubMed

Yin, Jingjing; Qu, Jianguo; Zhang, Wenjie; Lu, Dongrui; Gao, Yucong; Ying, Xixiang; Kang, Tingguo

2014-05-01

Hawthorn leaves, a well-known traditional Chinese medicine, have been widely used for treating cardiovascular and fatty liver diseases. The present study aimed to investigate the therapeutic basis treating fatty liver disease by comparing the tissue distribution of six compounds of hawthorn leaf extract (HLE) in fatty liver rats and healthy rats after oral administration at first day, half month and one month, separately. Therefore, a sensitive and specific HPLC method with internal standard was developed and validated to determine chlorogenic acid, vitexin-4''-O-glucoside, vitexin-2''-O-rhamnoside, vitexin, rutin and hyperoside in the tissues including heart, liver, spleen, kidney, stomach and intestine. The results indicated that the six compounds in HLE presented some bioactivity in treating rat fatty liver as the concentrations of the six compounds varied significantly in inter- and intragroup comparisons (healthy and/or fatty liver group). Copyright © 2013 John Wiley & Sons, Ltd.

Analysis Study of Stevioside and Rebaudioside A from Stevia rebaudiana Bertoni by Normal Phase SPE and RP-HPLC

NASA Astrophysics Data System (ADS)

Martono, Y.; Rohman, A.; Riyanto, S.; Martono, S.

2018-04-01

Solid Phase Extraction (SPE) method using silica as sorbent for stevioside and rebaudiosida A analysis in Stevia rebaudiana Bertoni leaf have not been performed. The aim of this study is to develop SPE method using silica as sorbent for Reverse Phase-High Performance Liquid Chromatography (RP-HPLC) analysis of stevioside and rebaudiosida A in S. rebaudiana leaf. The results of this study indicate that the optimal conditions for normal phase SPE (silica) are conditioned with 3.0 mL of hexane. The sample loading volume is 0.1 mL. Cartridge is eluted with 1.0 mL acetonitrile: water (80: 20, v/v) to separate both analytes. The cartridge is washed with chloroform and water of 0.3 mL respectively. The developed SPE sample preparation method meets the accuracy and precision test and can be used for the analysis of stevioside and rebaudioside A by RP-HPLC.

Explaining the variability of Photochemical Reflectance Index (PRI): deconvolution of variability related to Light Use Efficiency and Canopy attributes.

NASA Astrophysics Data System (ADS)

Merlier, Elodie; Hmimina, Gabriel; Dufrêne, Eric; Soudani, Kamel

2014-05-01

The Photochemical Reflectance Index (PRI) was designed as a proxy of the state of xanthophyll cycle which is used as a response of plants to excess of light (Gamon et al., 1990; 1992). Strong relationships between PRI and LUE were shown at leaf and canopy scales and over a wide range of species (Garbulsky et al., 2011). However, its use at canopy scale was shown to be significantly hampered by effects of confounding factors such as the PRI sensitivity to leaf pigment content (Gamon et al. 2001; Nakaji et al. 2006) and to canopy structure (Hilker et al. 2008). Several approaches aimed at correcting such effects and recent works focused on the deconvolution of LUE related and LUE unrelated PRI variability (Rahimzadeh-Bajgiran et al. 2012).In this study, the PRI variability at canopy scale is investigated over two years on three species (Fagus sylvatica, Quercus robur and Pinus sylvestris) growing under two water regimes. At daily scale, PRI variability is mainly explained by radiation conditions. As already reported at leaf scale in Hmimina et al. (2014), analysis of PRI responses to incoming photosynthetically active radiation over seasonal scale allowed to separate two sources of variability : a constitutive variability mainly related to canopy structure and leaf chlorophyll content and a facultative variability mainly related to LUE and soil moisture content. These results highlight the composite nature of PRI signal measured at canopy scale and the importance of disentangling its sources of variability in order to accurately assess ecosystem light use efficiency. Gamon JA, Field CB, Bilger W, Björkman O, Fredeen AL, Peñuelas J. 1990. Remote sensing of the xanthophyll cycle and chlorophyll fluorescence in sunflower leaves and canopies. Oecologia 85, 1-7. Gamon JA, Field CB, Fredeen A AL, Thayer S. 2001. Assessing photosynthetic downregulation in sunflower stands with an optically-based model. Photosynthesis Research 67, 113-125. Gamon JA, Peñuelas J, Field CB. 1992. A narrow-waveband spectral index that tracks diurnal changes in photosynthetic efficiency. Remote Sensing of Environment 41, 35-44. Garbulsky MF, Peñuelas J, Gamon J, Inoue Y, Filella I. 2011. The photochemical reflectance index (PRI) and the remote sensing of leaf, canopy and ecosystem radiation use efficiencies: A review and meta-analysis. Remote Sensing of Environment 115, 281-297. Hilker T, Coops NC, Hall FG, Black TA, Wulder MA, Nesic Z, Krishnan P. 2008. Separating physiologically and directionally induced changes in PRI using BRDF models. Remote Sensing of Environment 112, 2777-2788. Hmimina G, Dufrêne E, Soudani K. 2014. Relationship between PRI and leaf ecophysiological and biochemical parameters under two different water statuses: toward a rapid and efficient correction method using real-time measurements. Plant, Cell & Environment 37, 2, 473-487. Nakaji T, Oguma H, Fujinuma Y. 2006. Seasonal changes in the relationship between photochemical reflectance index and photosynthetic light use efficiency of Japanese larch needles. International Journal of Remote Sensing 27, 493-509. Rahimzadeh-Bajgiran P, Munehiro M, Omasa K. 2012. Relationships between the photochemical reflectance index (PRI) and chlorophyll fluorescence parameters and plant pigment indices at different leaf growth stages. Photosynthesis Research 113, 261-271.

Mapping the understorey of deciduous woodland from leaf-on and leaf-off airborne LiDAR data: A case study in lowland Britain

NASA Astrophysics Data System (ADS)

Hill, R. A.; Broughton, R. K.

This study examines the understorey information present in discrete-return LiDAR (Light Detection And Ranging) data acquired for temperate deciduous woodland in mid summer (leaf-on) and in early spring when the understorey had mostly leafed out, but the overstorey had only just begun budburst (referred to here as leaf-off). The woodland is ancient, semi-natural broadleaf and has a heterogeneous structure with a mostly closed canopy overstorey and a patchy understorey layer. In this study, the understorey was defined as suppressed trees and shrubs growing beneath an overstorey canopy. Forest mensuration data for the study site were examined to identify thresholds (taking the 95th percentile) for crown depth as a percentage of crown top height for the six overstorey tree species present. These data were used in association with a digital tree species map and leaf-on first return LiDAR data, to identify the possible depth of space available below the overstorey canopy in which an understorey layer could exist. The leaf-off last return LiDAR data were then examined to identify whether they contained information on where this space was occupied by suppressed trees or shrubs forming an understorey. Thus, understorey was mapped from the leaf-off last return data where the height was below the predicted crown depth. A height threshold of 1 m was applied to separate the ground vegetation layer from the understorey. The derived understorey model formed a discontinuous layer covering 46.4 ha (or 31% of the study site), with an average height of 2.64 m and a 77% correspondence with field data on the presence/absence of suppressed trees and shrubs (kappa 0.53). Because the first return data in leaf-on and leaf-off conditions were very similar (differing by an average of just 0.87 m), it was also possible to map the understorey layer using leaf-off data alone. The resultant understorey model covered 39.4 ha (or 26% of the study site), and had a 72% correspondence with field data on the presence/absence of suppressed trees and shrubs (kappa 0.45). This moderate reduction in the area of understorey mapped and associated accuracy came with a saving of half of all data acquisition and pre-processing costs. Whilst the understorey modelling presented here undoubtedly benefited from the specific timing of LiDAR data acquisition and from ancillary data available for the study site, the conclusions have resonance beyond this case study. Given that the understorey and overstorey canopies in lowland broadleaf woodland can merge into one another, the modelling of understorey information from discrete-return LiDAR data must consider overstorey canopy characteristics and laser penetration through the overstorey. It is not adequate in such circumstances to apply simple height thresholds to LiDAR height frequency distributions, as this is unlikely to distinguish whether a return has backscattered from the lower parts of the overstorey canopy or from near the surface of the understorey canopy.

Feasibility Study of Glass Dosimeter for In Vivo Measurement: Dosimetric Characterization and Clinical Application in Proton Beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rah, Jeong-Eun; Oh, Do Hoon; Kim, Jong Won

Purpose: To evaluate the suitability of the GD-301 glass dosimeter for in vivo dose verification in proton therapy. Methods and Materials: The glass dosimeter was analyzed for its dosimetrics characteristic in proton beam. Dosimeters were calibrated in a water phantom using a stairlike holder specially designed for this study. To determine the accuracy of the glass dosimeter in proton dose measurements, we compared the glass dosimeter and thermoluminescent dosimeter (TLD) dose measurements using a cylindrical phantom. We investigated the feasibility of the glass dosimeter for the measurement of dose distributions near the superficial region for proton therapy plans with amore » varying separation between the target volume and the surface of 6 patients. Results and Discussion: Uniformity was within 1.5%. The dose-response has good linearity. Dose-rate, fading, and energy dependence were found to be within 3%. The beam profile measured using the glass dosimeter was in good agreement with the profile obtained from the ionization chamber. Depth-dose distributions in nonmodulated and modulated proton beams obtained with the glass dosimeter were estimated to be within 3%, which was lower than those with the ionization chamber. In the phantom study, the difference of isocenter dose between the delivery dose calculated by the treatment planning system and that measured by the glass dosimeter was within 5%. With in vivo dosimetry, the calculated surface doses overestimated measurements by 4%-16% using glass dosimeter and TLD. Conclusion: It is recommended that bolus be added for these clinical cases. We also believe that the glass dosimeter has considerable potential for use with in vivo patient proton dosimetry.« less

Feasibility study of glass dosimeter for in vivo measurement: dosimetric characterization and clinical application in proton beams.

PubMed

Rah, Jeong-Eun; Oh, Do Hoon; Kim, Jong Won; Kim, Dae-Hyun; Suh, Tae-Suk; Ji, Young Hoon; Shin, Dongho; Lee, Se Byeong; Kim, Dae Yong; Park, Sung Yong

2012-10-01

To evaluate the suitability of the GD-301 glass dosimeter for in vivo dose verification in proton therapy. The glass dosimeter was analyzed for its dosimetrics characteristic in proton beam. Dosimeters were calibrated in a water phantom using a stairlike holder specially designed for this study. To determine the accuracy of the glass dosimeter in proton dose measurements, we compared the glass dosimeter and thermoluminescent dosimeter (TLD) dose measurements using a cylindrical phantom. We investigated the feasibility of the glass dosimeter for the measurement of dose distributions near the superficial region for proton therapy plans with a varying separation between the target volume and the surface of 6 patients. Uniformity was within 1.5%. The dose-response has good linearity. Dose-rate, fading, and energy dependence were found to be within 3%. The beam profile measured using the glass dosimeter was in good agreement with the profile obtained from the ionization chamber. Depth-dose distributions in nonmodulated and modulated proton beams obtained with the glass dosimeter were estimated to be within 3%, which was lower than those with the ionization chamber. In the phantom study, the difference of isocenter dose between the delivery dose calculated by the treatment planning system and that measured by the glass dosimeter was within 5%. With in vivo dosimetry, the calculated surface doses overestimated measurements by 4%-16% using glass dosimeter and TLD. It is recommended that bolus be added for these clinical cases. We also believe that the glass dosimeter has considerable potential for use with in vivo patient proton dosimetry. Copyright © 2012 Elsevier Inc. All rights reserved.

SU-E-T-139: Feasibility Study of Glass Dosimeter for in Vivo Measurement: Dosimetric Characterization and Clinical Application in Proton Beams.

PubMed

Lah, J; Kim, D; Park, S

2012-06-01

To evaluate the suitability of the GD-301 glass dosimeter for use in in vivo dose verification in proton therapy. The glass dosimeter was analyzed for its dosimetric characteristic in proton beam. Dosimeters were calibrated in a water phantom using a stair-like holder specially designed for this study. To determine the accuracy of the glass dosimeter in proton dose measurements, we compared the glass dosimeter and TLD dose measurements of plan delivery using a cylindrical phantom. We investigated the feasibility of the glass dosimeter for the measurement of dose distributions near the superficial region for proton therapy plans with a varying separation between the target volume and the surface of 6 patients. Uniformity was within 1.5%. The dose-response has a good linear. Dose-rate, fading, and energy dependence were found to be within 3%. The beam profile measured using the glass dosimeter was in good agreement with the profile obtained from the ionization chamber. Depth-dose distributions in non-modulated and modulated proton beams obtained with the glass dosimeter were estimated to be within 3%, which was lower than those with the ionization chamber. In the phantom study, the difference of isocenter dose between the delivery dose calculated by the Eclipse and that of the measured by the glass dosimeter was within 5%. In vivo dosimetry of patients, given the results of the glass dosimeter and TLD measurements, calculated doses on the surface of the patient are typically overestimated between 4% and 16%. As such, it is recommended that bolus be added for these clinical cases. We also believe that the glass dosimeter has considerable potential to be used for in vivo patient proton dosimetry. © 2012 American Association of Physicists in Medicine.

External dose-rate conversion factors of radionuclides for air submersion, ground surface contamination and water immersion based on the new ICRP dosimetric setting.

PubMed

Yoo, Song Jae; Jang, Han-Ki; Lee, Jai-Ki; Noh, Siwan; Cho, Gyuseong

2013-01-01

For the assessment of external doses due to contaminated environment, the dose-rate conversion factors (DCFs) prescribed in Federal Guidance Report 12 (FGR 12) and FGR 13 have been widely used. Recently, there were significant changes in dosimetric models and parameters, which include the use of the Reference Male and Female Phantoms and the revised tissue weighting factors, as well as the updated decay data of radionuclides. In this study, the DCFs for effective and equivalent doses were calculated for three exposure settings: skyshine, groundshine and water immersion. Doses to the Reference Phantoms were calculated by Monte Carlo simulations with the MCNPX 2.7.0 radiation transport code for 26 mono-energy photons between 0.01 and 10 MeV. The transport calculations were performed for the source volume within the cut-off distances practically contributing to the dose rates, which were determined by a simplified calculation model. For small tissues for which the reduction of variances are difficult, the equivalent dose ratios to a larger tissue (with lower statistical errors) nearby were employed to make the calculation efficient. Empirical response functions relating photon energies, and the organ equivalent doses or the effective doses were then derived by the use of cubic-spline fitting of the resulting doses for 26 energy points. The DCFs for all radionuclides considered important were evaluated by combining the photon emission data of the radionuclide and the empirical response functions. Finally, contributions of accompanied beta particles to the skin equivalent doses and the effective doses were calculated separately and added to the DCFs. For radionuclides considered in this study, the new DCFs for the three exposure settings were within ±10 % when compared with DCFs in FGR 13.

Single-Isocenter Multiple-Target Stereotactic Radiosurgery: Risk of Compromised Coverage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roper, Justin, E-mail: justin.roper@emory.edu; Department of Biostatistics and Bioinformatics, Winship Cancer Institute of Emory University, Atlanta, Georgia; Chanyavanich, Vorakarn

2015-11-01

Purpose: To determine the dosimetric effects of rotational errors on target coverage using volumetric modulated arc therapy (VMAT) for multitarget stereotactic radiosurgery (SRS). Methods and Materials: This retrospective study included 50 SRS cases, each with 2 intracranial planning target volumes (PTVs). Both PTVs were planned for simultaneous treatment to 21 Gy using a single-isocenter, noncoplanar VMAT SRS technique. Rotational errors of 0.5°, 1.0°, and 2.0° were simulated about all axes. The dose to 95% of the PTV (D95) and the volume covered by 95% of the prescribed dose (V95) were evaluated using multivariate analysis to determine how PTV coverage was relatedmore » to PTV volume, PTV separation, and rotational error. Results: At 0.5° rotational error, D95 values and V95 coverage rates were ≥95% in all cases. For rotational errors of 1.0°, 7% of targets had D95 and V95 values <95%. Coverage worsened substantially when the rotational error increased to 2.0°: D95 and V95 values were >95% for only 63% of the targets. Multivariate analysis showed that PTV volume and distance to isocenter were strong predictors of target coverage. Conclusions: The effects of rotational errors on target coverage were studied across a broad range of SRS cases. In general, the risk of compromised coverage increased with decreasing target volume, increasing rotational error and increasing distance between targets. Multivariate regression models from this study may be used to quantify the dosimetric effects of rotational errors on target coverage given patient-specific input parameters of PTV volume and distance to isocenter.« less

Plan delivery quality assurance for CyberKnife: Statistical process control analysis of 350 film-based patient-specific QAs.

PubMed

Bellec, J; Delaby, N; Jouyaux, F; Perdrieux, M; Bouvier, J; Sorel, S; Henry, O; Lafond, C

2017-07-01

Robotic radiosurgery requires plan delivery quality assurance (DQA) but there has never been a published comprehensive analysis of a patient-specific DQA process in a clinic. We proposed to evaluate 350 consecutive film-based patient-specific DQAs using statistical process control. We evaluated the performance of the process to propose achievable tolerance criteria for DQA validation and we sought to identify suboptimal DQA using control charts. DQAs were performed on a CyberKnife-M6 using Gafchromic-EBT3 films. The signal-to-dose conversion was performed using a multichannel-correction and a scanning protocol that combined measurement and calibration in a single scan. The DQA analysis comprised a gamma-index analysis at 3%/1.5mm and a separate evaluation of spatial and dosimetric accuracy of the plan delivery. Each parameter was plotted on a control chart and control limits were calculated. A capability index (Cpm) was calculated to evaluate the ability of the process to produce results within specifications. The analysis of capability showed that a gamma pass rate of 85% at 3%/1.5mm was highly achievable as acceptance criteria for DQA validation using a film-based protocol (Cpm>1.33). 3.4% of DQA were outside a control limit of 88% for gamma pass-rate. The analysis of the out-of-control DQA helped identify a dosimetric error in our institute for a specific treatment type. We have defined initial tolerance criteria for DQA validations. We have shown that the implementation of a film-based patient-specific DQA protocol with the use of control charts is an effective method to improve patient treatment safety on CyberKnife. Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

External dose-rate conversion factors of radionuclides for air submersion, ground surface contamination and water immersion based on the new ICRP dosimetric setting

PubMed Central

Yoo, Song Jae; Jang, Han-Ki; Lee, Jai-Ki; Noh, Siwan; Cho, Gyuseong

2013-01-01

For the assessment of external doses due to contaminated environment, the dose-rate conversion factors (DCFs) prescribed in Federal Guidance Report 12 (FGR 12) and FGR 13 have been widely used. Recently, there were significant changes in dosimetric models and parameters, which include the use of the Reference Male and Female Phantoms and the revised tissue weighting factors, as well as the updated decay data of radionuclides. In this study, the DCFs for effective and equivalent doses were calculated for three exposure settings: skyshine, groundshine and water immersion. Doses to the Reference Phantoms were calculated by Monte Carlo simulations with the MCNPX 2.7.0 radiation transport code for 26 mono-energy photons between 0.01 and 10 MeV. The transport calculations were performed for the source volume within the cut-off distances practically contributing to the dose rates, which were determined by a simplified calculation model. For small tissues for which the reduction of variances are difficult, the equivalent dose ratios to a larger tissue (with lower statistical errors) nearby were employed to make the calculation efficient. Empirical response functions relating photon energies, and the organ equivalent doses or the effective doses were then derived by the use of cubic-spline fitting of the resulting doses for 26 energy points. The DCFs for all radionuclides considered important were evaluated by combining the photon emission data of the radionuclide and the empirical response functions. Finally, contributions of accompanied beta particles to the skin equivalent doses and the effective doses were calculated separately and added to the DCFs. For radionuclides considered in this study, the new DCFs for the three exposure settings were within ±10 % when compared with DCFs in FGR 13. PMID:23542764

A dosimetric phantom study of thoracic radiotherapy based on three-dimensional modeling of mediastinal lymph nodes

PubMed Central

Zhang, Ji-Bin; Zhao, Li-Rong; Cui, Tian-Xiang; Chen, Xie-Wan; Yang, Qiao; Zhou, Yi-Bing; Chen, Zheng-Tang; Zhang, Shao-Xiang; Sun, Jian-Guo

2018-01-01

The aim of the present study was to investigate the optimal strategy and dosimetric measurement of thoracic radiotherapy based on three-dimensional (3D) modeling of mediastinal lymph nodes (MLNs). A 3D model of MLNs was constructed from a Chinese Visible Human female dataset. Image registration and fusion between reconstructed MLNs and original chest computed tomography (CT) images was conducted in the Eclipse™ treatment planning system (TPS). There were three plans, including 3D conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT), which were designed based on 10 cases of simulated lung lesions (SLLs) and MLNs. The quality of these plans was evaluated via examining indexes, including conformity index (CI), homogeneity index and clinical target volume (CTV) coverage. Dose-volume histogram analysis was performed on SLL, MLNs and organs at risk (OARs). A Chengdu Dosimetric Phantom (CDP) was then drilled at specific MLNs according to 20 patients with thoracic tumors and of a medium-build. These plans were repeated on fused MLNs and CDP CT images in the Eclipse™ TPS. Radiation doses at the SLLs and MLNs of the CDP were measured and compared with calculated doses. The established 3D MLN model demonstrated the spatial location of MLNs and adjacent structures. Precise image registration and fusion were conducted between reconstructed MLNs and the original chest CT or CDP CT images. IMRT demonstrated greater values in CI, CTV coverage and OAR (lungs and spinal cord) protection, compared with 3D-CRT and VMAT (P<0.05). The deviation between the measured and calculated doses was within ± 10% at SLL, and at the 2R and 7th MLN stations. In conclusion, the 3D MLN model can benefit plan optimization and dosimetric measurement of thoracic radiotherapy, and when combined with CDP, it may provide a tool for clinical dosimetric monitoring. PMID:29556300

SU-E-T-651: Quantification of Dosimetric Accuracy of Respiratory Gated Stereotactic Body Radiation Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thiyagarajan, Rajesh; Vikraman, S; Maragathaveni, S

2015-06-15

Purpose: To quantify the dosimetric accuracy of respiratory gated stereotactic body radiation therapy delivery using dynamic thorax phantom. Methods: Three patients with mobile target (2 lung, 1liver) were chosen. Retrospective 4DCT image sets were acquired for using Varian RPM system. An in-house MATLAB program was designed for MIP, MinIP and AvgIP generation. ITV was contoured on MIP image set for lung patients and on MinIP for liver patient. Dynamic IMRT plans were generated on selected phase bin image set in Eclipse (v10.0) planning system. CIRS dynamic thorax phantom was used to perform the dosimetric quality assurance. Patient breathing pattern filemore » from RPM system was converted to phantom compatible file by an in-house MATLAB program. This respiratory pattern fed to the CIRS dynamic thorax phantom. 4DCT image set was acquired for this phantom using patient breathing pattern. Verification plans were generated using patient gating window and delivered on the phantom. Measurements were carried out using with ion chamber and EBT2 film. Exposed films were analyzed and evaluated in FilmQA software. Results: The stability of gated output in comparison with un-gated output was within 0.5%. The Ion chamber measured and TPS calculated dose compared for all the patients. The difference observed was 0.45%, −0.52% and −0.54 for Patient 1, Patient2 and Patient 3 respectively.Gamma value evaluated from EBT film shows pass rates from 92.41% to 99.93% for 3% dose difference and 3mm distance to agreement criteria. Conclusion: Dosimetric accuracy of respiratory gated SBRT delivery for lung and liver was dosimetrically acceptable. The Ion chamber measured dose was within 0.203±0.5659% of the expected dose. Gamma pass rates were within 96.63±3.84% of the expected dose.« less

Quantifying the effect of air gap, depth, and range shifter thickness on TPS dosimetric accuracy in superficial PBS proton therapy.

PubMed

Shirey, Robert J; Wu, Hsinshun Terry

2018-01-01

This study quantifies the dosimetric accuracy of a commercial treatment planning system as functions of treatment depth, air gap, and range shifter thickness for superficial pencil beam scanning proton therapy treatments. The RayStation 6 pencil beam and Monte Carlo dose engines were each used to calculate the dose distributions for a single treatment plan with varying range shifter air gaps. Central axis dose values extracted from each of the calculated plans were compared to dose values measured with a calibrated PTW Markus chamber at various depths in RW3 solid water. Dose was measured at 12 depths, ranging from the surface to 5 cm, for each of the 18 different air gaps, which ranged from 0.5 to 28 cm. TPS dosimetric accuracy, defined as the ratio of calculated dose relative to the measured dose, was plotted as functions of depth and air gap for the pencil beam and Monte Carlo dose algorithms. The accuracy of the TPS pencil beam dose algorithm was found to be clinically unacceptable at depths shallower than 3 cm with air gaps wider than 10 cm, and increased range shifter thickness only added to the dosimetric inaccuracy of the pencil beam algorithm. Each configuration calculated with Monte Carlo was determined to be clinically acceptable. Further comparisons of the Monte Carlo dose algorithm to the measured spread-out Bragg Peaks of multiple fields used during machine commissioning verified the dosimetric accuracy of Monte Carlo in a variety of beam energies and field sizes. Discrepancies between measured and TPS calculated dose values can mainly be attributed to the ability (or lack thereof) of the TPS pencil beam dose algorithm to properly model secondary proton scatter generated in the range shifter. © 2017 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

Clinical and Dosimetric Predictors of Radiation Pneumonitis in a Large Series of Patients Treated With Stereotactic Body Radiation Therapy to the Lung

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baker, Ryan; Han Gang; Sarangkasiri, Siriporn

2013-01-01

Purpose: To report clinical and dosimetric factors predictive of radiation pneumonitis (RP) in patients receiving lung stereotactic body radiation therapy (SBRT) from a series of 240 patients. Methods and Materials: Of the 297 isocenters treating 263 patients, 240 patients (n=263 isocenters) had evaluable information regarding RP. Age, gender, current smoking status and pack-years, O{sub 2} use, Charlson Comorbidity Index, prior lung radiation therapy (yes/no), dose/fractionation, V{sub 5}, V{sub 13}, V{sub 20}, V{sub prescription}, mean lung dose, planning target volume (PTV), total lung volume, and PTV/lung volume ratio were recorded. Results: Twenty-nine patients (11.0%) developed symptomatic pneumonitis (26 grade 2, 3more » grade 3). The mean V{sub 20} was 6.5% (range, 0.4%-20.2%), and the average mean lung dose was 5.03 Gy (0.547-12.2 Gy). In univariable analysis female gender (P=.0257) and Charlson Comorbidity index (P=.0366) were significantly predictive of RP. Among dosimetric parameters, V{sub 5} (P=.0186), V{sub 13} (P=.0438), and V{sub prescription} (where dose = 60 Gy) (P=.0128) were significant. There was only a trend toward significance for V{sub 20} (P=.0610). Planning target volume/normal lung volume ratio was highly significant (P=.0024). In multivariable analysis the clinical factors of female gender, pack-years smoking, and larger gross internal tumor volume and PTV were predictive (P=.0094, .0312, .0364, and .052, respectively), but no dosimetric factors were significant. Conclusions: Rate of symptomatic RP was 11%. Our mean lung dose was <600 cGy in most cases and V20 <10%. In univariable analysis, dosimetric factors were predictive, while tumor size (or tumor/lung volume ratio) played a role in multivariable and univariable and analysis, respectively.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, J; Gu, X; Lu, W

Purpose: A novel distance-dose weighting method for label fusion was developed to increase segmentation accuracy in dosimetrically important regions for prostate radiation therapy. Methods: Label fusion as implemented in the original SIMPLE (OS) for multi-atlas segmentation relies iteratively on the majority vote to generate an estimated ground truth and DICE similarity measure to screen candidates. The proposed distance-dose weighting puts more values on dosimetrically important regions when calculating similarity measure. Specifically, we introduced distance-to-dose error (DDE), which converts distance to dosimetric importance, in performance evaluation. The DDE calculates an estimated DE error derived from surface distance differences between the candidatemore » and estimated ground truth label by multiplying a regression coefficient. To determine the coefficient at each simulation point on the rectum, we fitted DE error with respect to simulated voxel shift. The DEs were calculated by the multi-OAR geometry-dosimetry training model previously developed in our research group. Results: For both the OS and the distance-dose weighted SIMPLE (WS) results, the evaluation metrics for twenty patients were calculated using the ground truth segmentation. The mean difference of DICE, Hausdorff distance, and mean absolute distance (MAD) between OS and WS have shown 0, 0.10, and 0.11, respectively. In partial MAD of WS which calculates MAD within a certain PTV expansion voxel distance, the lower MADs were observed at the closer distances from 1 to 8 than those of OS. The DE results showed that the segmentation from WS produced more accurate results than OS. The mean DE error of V75, V70, V65, and V60 were decreased by 1.16%, 1.17%, 1.14%, and 1.12%, respectively. Conclusion: We have demonstrated that the method can increase the segmentation accuracy in rectum regions adjacent to PTV. As a result, segmentation using WS have shown improved dosimetric accuracy than OS. The WS will provide dosimetrically important label selection strategy in multi-atlas segmentation. CPRIT grant RP150485.« less

Dosimetric quality endpoints for low-dose-rate prostate brachytherapy using biological effective dose (bed) vs. conventional dose

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Rachana; Al-Hallaq, Hania; Pelizzari, Charles A.

2003-12-31

The purpose of this study was to compare conventional low-dose-rate prostate brachytherapy dosimetric quality parameters with their biological effective dose (BED) counterparts. To validate a model for transformation from conventional dose to BED, the postimplant plans of 31 prostate brachytherapy patients were evaluated using conventional dose-volume histogram (DVH) quality endpoints and analogous BED-DVH endpoints. Based on CT scans obtained 4 weeks after implantation, DVHs were computed and standard dosimetric endpoints V100 (volume receiving 100% of the prescribed dose), V150, V200, HI (1-[V150/V100]), and D90 (dose that 90% of the target volume received) were obtained for quality analysis. Using known andmore » reported transformations, dose grids were transformed to BED-early ({alpha}/{beta} = 10 Gy) and BED-late ({alpha}/{beta} = 3 Gy) grids, and the same dosimetric endpoints were analyzed. For conventional, BED-early and BED-late DVHs, no differences in V100 were seen (0.896, 0.893, and 0.894, respectively). However, V150 and V200 were significantly higher for both BED-early (0.582 and 0.316) and BED-late (0.595 and 0.337), compared with the conventional (0.539 and 0.255) DVHs. D90 was significantly lower for the BED-early (103.1 Gy) and BED-late transformations (106.9 Gy) as compared with the conventional (119.5 Gy) DVHs. The conventional prescription parameter V100 is the same for the corresponding BED-early and BED-late transformed DVHs. The toxicity parameters V150 and V200 are slightly higher using the BED transformations, suggesting that the BED doses are somewhat higher than predicted using conventional DVHs. The prescription/quality parameter D90 is slightly lower, implying that target coverage is lower than predicted using conventional DVHs. This methodology can be applied to analyze BED dosimetric endpoints to improve clinical outcome and reduce complications of prostate brachytherapy.« less

SU-E-T-490: Independent Three-Dimensional (3D) Dose Verification of VMAT/SBRT Using EPID and Cloud Computing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ding, A; Han, B; Bush, K

Purpose: Dosimetric verification of VMAT/SBRT is currently performed on one or two planes in a phantom with either film or array detectors. A robust and easy-to-use 3D dosimetric tool has been sought since the advent of conformal radiation therapy. Here we present such a strategy for independent 3D VMAT/SBRT plan verification system by a combined use of EPID and cloud-based Monte Carlo (MC) dose calculation. Methods: The 3D dosimetric verification proceeds in two steps. First, the plan was delivered with a high resolution portable EPID mounted on the gantry, and the EPID-captured gantry-angle-resolved VMAT/SBRT field images were converted into fluencemore » by using the EPID pixel response function derived from MC simulations. The fluence was resampled and used as the input for an in-house developed Amazon cloud-based MC software to reconstruct the 3D dose distribution. The accuracy of the developed 3D dosimetric tool was assessed using a Delta4 phantom with various field sizes (square, circular, rectangular, and irregular MLC fields) and different patient cases. The method was applied to validate VMAT/SBRT plans using WFF and FFF photon beams (Varian TrueBeam STX). Results: It was found that the proposed method yielded results consistent with the Delta4 measurements. For points on the two detector planes, a good agreement within 1.5% were found for all the testing fields. Patient VMAT/SBRT plan studies revealed similar level of accuracy: an average γ-index passing rate of 99.2± 0.6% (3mm/3%), 97.4± 2.4% (2mm/2%), and 72.6± 8.4 % ( 1mm/1%). Conclusion: A valuable 3D dosimetric verification strategy has been developed for VMAT/SBRT plan validation. The technique provides a viable solution for a number of intractable dosimetry problems, such as small fields and plans with high dose gradient.« less

Cardiac risk index as a simple geometric indicator to select patients for the heart-sparing radiotherapy of left-sided breast cancer.

PubMed

Sung, KiHoon; Choi, Young Eun; Lee, Kyu Chan

2017-06-01

This is a dosimetric study to identify a simple geometric indicator to discriminate patients who meet the selection criterion for heart-sparing radiotherapy (RT). The authors proposed a cardiac risk index (CRI), directly measurable from the CT images at the time of scanning. Treatment plans were regenerated using the CT data of 312 consecutive patients with left-sided breast cancer. Dosimetric analysis was performed to estimate the risk of cardiac mortality using cardiac dosimetric parameters, such as the relative heart volumes receiving ≥25 Gy (heart V 25 ). For each CT data set, in-field heart depth (HD) and in-field heart width (HW) were measured to generate the geometric parameters, including maximum HW (HW max ) and maximum HD (HD max ). Seven geometric parameters were evaluated as candidates for CRI. Receiver operating characteristic (ROC) curve analyses were used to examine the overall discriminatory power of the geometric parameters to select high-risk patients (heart V 25  ≥ 10%). Seventy-one high-risk (22.8%) and 241 low-risk patients (77.2%) were identified by dosimetric analysis. The geometric and dosimetric parameters were significantly higher in the high-risk group. Heart V 25 showed the strong positive correlations with all geometric parameters examined (r > 0.8, p < 0.001). The product of HD max and HW max (CRI) revealed the largest area under the curve (AUC) value (0.969) and maintained 100% sensitivity and 88% specificity at the optimal cut-off value of 14.58 cm 2 . Cardiac risk index proposed as a simple geometric indicator to select high-risk patients provides useful guidance for clinicians considering optimal implementation of heart-sparing RT. © 2016 The Royal Australian and New Zealand College of Radiologists.

A dosimetric uncertainty analysis for photon-emitting brachytherapy sources: Report of AAPM Task Group No. 138 and GEC-ESTRO

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeWerd, Larry A.; Ibbott, Geoffrey S.; Meigooni, Ali S.

2011-02-15

This report addresses uncertainties pertaining to brachytherapy single-source dosimetry preceding clinical use. The International Organization for Standardization (ISO) Guide to the Expression of Uncertainty in Measurement (GUM) and the National Institute of Standards and Technology (NIST) Technical Note 1297 are taken as reference standards for uncertainty formalism. Uncertainties in using detectors to measure or utilizing Monte Carlo methods to estimate brachytherapy dose distributions are provided with discussion of the components intrinsic to the overall dosimetric assessment. Uncertainties provided are based on published observations and cited when available. The uncertainty propagation from the primary calibration standard through transfer to the clinicmore » for air-kerma strength is covered first. Uncertainties in each of the brachytherapy dosimetry parameters of the TG-43 formalism are then explored, ending with transfer to the clinic and recommended approaches. Dosimetric uncertainties during treatment delivery are considered briefly but are not included in the detailed analysis. For low- and high-energy brachytherapy sources of low dose rate and high dose rate, a combined dosimetric uncertainty <5% (k=1) is estimated, which is consistent with prior literature estimates. Recommendations are provided for clinical medical physicists, dosimetry investigators, and source and treatment planning system manufacturers. These recommendations include the use of the GUM and NIST reports, a requirement of constancy of manufacturer source design, dosimetry investigator guidelines, provision of the lowest uncertainty for patient treatment dosimetry, and the establishment of an action level based on dosimetric uncertainty. These recommendations reflect the guidance of the American Association of Physicists in Medicine (AAPM) and the Groupe Europeen de Curietherapie-European Society for Therapeutic Radiology and Oncology (GEC-ESTRO) for their members and may also be used as guidance to manufacturers and regulatory agencies in developing good manufacturing practices for sources used in routine clinical treatments.« less

SU-F-BRB-15: Dosimetric Study of Radiation Therapy for Head/Neck Patients with Metallic Dental Fixtures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, L; Allan, E; Putten, M Van

Purpose: To investigate the dose contributions of scattered electrons from dental amalgams during head and neck radiotherapy, and to evaluate the protective role of dosimetric dental stents during treatment to prevent oral mucositis. Methods: A phantom was produced to accurately simulate the oral cavity and head. The oral cavity consisted of a tissue equivalent upper and lower jaw and complete set of teeth. A set of 4 mm ethylene copolymer dosimetric stents was made for the upper and lower teeth. Five removable gold caps were fitted to apposing right molars, and the phantom was crafted to accomodate horizontal and verticalmore » film for 2D dosimetry and NanoDot dosimeter for recording point doses. The head was simulated using a small cylindrical glass water bath. CT simulation was performed on the phantom with and without metal fittings and, in each case, with and without the dental stent. The CT image sets were imported into Eclipse treatment planning system for contouring and treatment planning, and a 9-field IMRT treatment plan was developed for each scenario. These plans were delivered using a Varian TrueBeam linear accelerator. Doses were recorded using GafChromic EBT2 films and NanoDot dosimeters. Results: The measurements revealed a 43% relative increase in dose measured adjacent to the metal fixtures in the horizontal plane without the use of the dental stent. This equates to a total dose of 100 Gy to the oral mucosa during a standard course of definitive radiotherapy. To our knowledge, this is the first dosimetric analysis of dental stents using an anatomically realistic phantom and modern beam arrangement. Conclusion: These results support the use of dosimetric dental stents in head and neck radiotherapy for patients with metallic dental fixtures as a way to effectively reduce dose to nearby mucosal surfaces and, hence, reduce the risk and severity of mucositis.« less

The dilemma of parotid gland and pharyngeal constrictor muscles preservation—Is daily online image guidance required? A dosimetric analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duffy, Olivia; Forde, Elizabeth; Leech, Michelle, E-mail: leechm@tcd.ie

With margin reduction common in head and neck radiotherapy, it is critical that the dosimetric effects of setup deviations are quantified. With past studies focusing on the quantification of positional and volumetric changes of organs at risk (OARs), this study aimed to measure the dose delivered to these the parotid gland (PG) and pharyngeal constrictor muscles (PCMs) using cone beam computed tomography (CBCT). Furthermore, this investigation sought to establish a potential time trend of change in dose delivered to target volumes secondary to ascertaining the need for daily image guidance (IG) to reduce the dose burden to these important OARs.more » Intensity modulated radiotherapy (IMRT) plans for 5 locally advanced head and neck patients' plans were created and mapped to weekly CBCTs. Each plan was recalculated without heterogeneity correction allowing for dosimetric comparison. Dosimetric endpoints recorded to assess the effect of positional variation were as per ICRU 83 and included D{sub 95} and D{sub 98} for the target volumes, mean dose (MD) and V{sub 30} {sub Gy} for the PGs, and V{sub 50} {sub Gy} and MD for the PCMs. Results were deemed statistically significant if p < 0.05. No significant time trends were established for these OARs. A significant decrease in V{sub 50} {sub Gy} was observed for all PCMs (p < 0.001) on all CBCTs relative to the original plan. Regarding target volumes, a highly significant decrease in MD (MD = 20 Gy, CI: −20.310 to −19.820) in D{sub 98} of the high-dose planning target volume (PTV [70 Gy]; PTVD{sub 98%} = 70 Gy) for case 3 was found (p ≤ 0.001). A nonpredictable, yet significant dosimetric effect was found. A clinically acceptable balance must be achieved between OAR dosimetry and target coverage as can be achieved by frequent IG.« less

Dosimetric characterization of optically stimulated luminescence dosimeter with therapeutic photon beams for use in clinical radiotherapy measurements.

PubMed

Ponmalar, Retna; Manickam, Ravikumar; Ganesh, K M; Saminathan, Sathiyan; Raman, Arun; Godson, Henry Finlay

2017-01-01

The modern radiotherapy techniques impose new challenges for dosimetry systems with high precision and accuracy in in vivo and in phantom dosimetric measurements. The knowledge of the basic characterization of a dosimetric system before patient dose verification is crucial. This incites the investigation of the potential use of nanoDot optically stimulated luminescence dosimeter (OSLD) for application in radiotherapy with therapeutic photon beams. Measurements were carried out with nanoDot OSLDs to evaluate the dosimetric characteristics such as dose linearity, dependency on field size, dose rate, energy and source-to-surface distance (SSD), reproducibility, fading effect, reader stability, and signal depletion per read out with cobalt-60 (60 Co) beam, 6 and 18 MV therapeutic photon beams. The data acquired with OSLDs were validated with ionization chamber data where applicable. Good dose linearity was observed for doses up to 300 cGy and above which supralinear behavior. The standard uncertainty with field size observed was 1.10% ± 0.4%, 1.09% ± 0.34%, and 1.2% ± 0.26% for 6 MV, 18 MV, and 60 Co beam, respectively. The maximum difference with dose rate was 1.3% ± 0.4% for 6 MV and 1.4% ± 0.4% for 18 MV photon beams. The largest variation in SSD was 1.5% ± 1.2% for 60 Co, 1.5% ± 0.9% for 6 MV, and 1.5% ± 1.3% for 18 MV photon beams. The energy dependence of OSL response at 18 MV and 60 Co with 6 MV beam was 1.5% ± 0.7% and 1.7% ± 0.6%, respectively. In addition, good reproducibility, stability after the decay of transient signal, and predictable fading were observed. The results obtained in this study indicate the efficacy and suitability of nanoDot OSLD for dosimetric measurements in clinical radiotherapy.

Correlation between gamma index passing rate and clinical dosimetric difference for pre-treatment 2D and 3D volumetric modulated arc therapy dosimetric verification.

PubMed

Jin, X; Yan, H; Han, C; Zhou, Y; Yi, J; Xie, C

2015-03-01

To investigate comparatively the percentage gamma passing rate (%GP) of two-dimensional (2D) and three-dimensional (3D) pre-treatment volumetric modulated arc therapy (VMAT) dosimetric verification and their correlation and sensitivity with percentage dosimetric errors (%DE). %GP of 2D and 3D pre-treatment VMAT quality assurance (QA) with different acceptance criteria was obtained by ArcCHECK® (Sun Nuclear Corporation, Melbourne, FL) for 20 patients with nasopharyngeal cancer (NPC) and 20 patients with oesophageal cancer. %DE were calculated from planned dose-volume histogram (DVH) and patients' predicted DVH calculated by 3DVH® software (Sun Nuclear Corporation). Correlation and sensitivity between %GP and %DE were investigated using Pearson's correlation coefficient (r) and receiver operating characteristics (ROCs). Relatively higher %DE on some DVH-based metrics were observed for both patients with NPC and oesophageal cancer. Except for 2%/2 mm criterion, the average %GPs for all patients undergoing VMAT were acceptable with average rates of 97.11% ± 1.54% and 97.39% ± 1.37% for 2D and 3D 3%/3 mm criteria, respectively. The number of correlations for 3D was higher than that for 2D (21 vs 8). However, the general correlation was still poor for all the analysed metrics (9 out of 26 for 3D 3%/3 mm criterion). The average area under the curve (AUC) of ROCs was 0.66 ± 0.12 and 0.71 ± 0.21 for 2D and 3D evaluations, respectively. There is a lack of correlation between %GP and %DE for both 2D and 3D pre-treatment VMAT dosimetric evaluation. DVH-based dose metrics evaluation obtained from 3DVH will provide more useful analysis. Correlation and sensitivity of %GP with %DE for VMAT QA were studied for the first time.

WE-AB-209-02: A New Inverse Planning Framework with Principle-Based Modeling of Inter-Structural Dosimetric Tradeoffs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, H; Dong, P; Xing, L

Purpose: Traditional radiotherapy inverse planning relies on the weighting factors to phenomenologically balance the conflicting criteria for different structures. The resulting manual trial-and-error determination of the weights has long been recognized as the most time-consuming part of treatment planning. The purpose of this work is to develop an inverse planning framework that parameterizes the inter-structural dosimetric tradeoff among with physically more meaningful quantities to simplify the search for a clinically sensible plan. Methods: A permissible dosimetric uncertainty is introduced for each of the structures to balance their conflicting dosimetric requirements. The inverse planning is then formulated as a convex feasibilitymore » problem, which aims to generate plans with acceptable dosimetric uncertainties. A sequential procedure (SP) is derived to decompose the model into three submodels to constrain the uncertainty in the planning target volume (PTV), the critical structures, and all other structures to spare, sequentially. The proposed technique is applied to plan a liver case and a head-and-neck case and compared with a conventional approach. Results: Our results show that the strategy is able to generate clinically sensible plans with little trial-and-error. In the case of liver IMRT, the fractional volumes to liver and heart above 20Gy are found to be 22% and 10%, respectively, which are 15.1% and 33.3% lower than that of the counterpart conventional plan while maintaining the same PTV coverage. The planning of the head and neck IMRT show the same level of success, with the DVHs for all organs at risk and PTV very competitive to a counterpart plan. Conclusion: A new inverse planning framework has been established. With physically more meaningful modeling of the inter-structural tradeoff, the technique enables us to substantially reduce the need for trial-and-error adjustment of the model parameters and opens new opportunities of incorporating prior knowledge to facilitate the treatment planning process.« less

Comparing a volume based template approach and ultrasound guided freehand approach in multicatheter interstitial accelerated partial breast irradiation.

PubMed

Koh, Vicky Y; Buhari, Shaik A; Tan, Poh Wee; Tan, Yun Inn; Leong, Yuh Fun; Earnest, Arul; Tang, Johann I

2014-06-01

Currently, there are two described methods of catheter insertion for women undergoing multicatheter interstitial accelerated partial breast irradiation (APBI). These are a volume based template approach (template) and a non-template ultrasound guidance freehand approach (non-template). We aim to compare dosimetric endpoints between the template and non-template approach. Twenty patients, who received adjuvant multicatheter interstitial APBI between August 2008 to March 2010 formed the study cohort. Dosimetric planning was based on the RTOG 04-13 protocol. For standardization, the planning target volume evaluation (PTV-Eval) and organs at risk were contoured with the assistance of the attending surgeon. Dosimetric endpoints include D90 of the PTV-Eval, Dose Homogeneity Index (DHI), V200, maximum skin dose (MSD), and maximum chest wall dose (MCD). A median of 18 catheters was used per patient. The dose prescribed was 34 Gy in 10 fractions BID over 5 days. The average breast volume was 846 cm(3) (526-1384) for the entire cohort and there was no difference between the two groups (p = 0.6). Insertion time was significantly longer for the non-template approach (mean 150 minutes) compared to the template approach (mean: 90 minutes) (p = 0.02). The planning time was also significantly longer for the non-template approach (mean: 240 minutes) compared to the template approach (mean: 150 minutes) (p < 0.01). The template approach yielded a higher D90 (mean: 95%) compared to the non-template approach (mean: 92%) (p < 0.01). There were no differences in DHI (p = 0.14), V200 (p = 0.21), MSD (p = 0.7), and MCD (p = 0.8). Compared to the non-template approach, the template approach offered significant shorter insertion and planning times with significantly improved dosimetric PTV-Eval coverage without significantly compromising organs at risk dosimetrically.

A dosimetric uncertainty analysis for photon-emitting brachytherapy sources: Report of AAPM Task Group No. 138 and GEC-ESTRO

PubMed Central

DeWerd, Larry A.; Ibbott, Geoffrey S.; Meigooni, Ali S.; Mitch, Michael G.; Rivard, Mark J.; Stump, Kurt E.; Thomadsen, Bruce R.; Venselaar, Jack L. M.

2011-01-01

This report addresses uncertainties pertaining to brachytherapy single-source dosimetry preceding clinical use. The International Organization for Standardization (ISO) Guide to the Expression of Uncertainty in Measurement (GUM) and the National Institute of Standards and Technology (NIST) Technical Note 1297 are taken as reference standards for uncertainty formalism. Uncertainties in using detectors to measure or utilizing Monte Carlo methods to estimate brachytherapy dose distributions are provided with discussion of the components intrinsic to the overall dosimetric assessment. Uncertainties provided are based on published observations and cited when available. The uncertainty propagation from the primary calibration standard through transfer to the clinic for air-kerma strength is covered first. Uncertainties in each of the brachytherapy dosimetry parameters of the TG-43 formalism are then explored, ending with transfer to the clinic and recommended approaches. Dosimetric uncertainties during treatment delivery are considered briefly but are not included in the detailed analysis. For low- and high-energy brachytherapy sources of low dose rate and high dose rate, a combined dosimetric uncertainty <5% (k=1) is estimated, which is consistent with prior literature estimates. Recommendations are provided for clinical medical physicists, dosimetry investigators, and source and treatment planning system manufacturers. These recommendations include the use of the GUM and NIST reports, a requirement of constancy of manufacturer source design, dosimetry investigator guidelines, provision of the lowest uncertainty for patient treatment dosimetry, and the establishment of an action level based on dosimetric uncertainty. These recommendations reflect the guidance of the American Association of Physicists in Medicine (AAPM) and the Groupe Européen de Curiethérapie–European Society for Therapeutic Radiology and Oncology (GEC-ESTRO) for their members and may also be used as guidance to manufacturers and regulatory agencies in developing good manufacturing practices for sources used in routine clinical treatments. PMID:21452716

A planning comparison of 3-dimensional conformal multiple static field, conformal arc, and volumetric modulated arc therapy for the delivery of stereotactic body radiotherapy for early stage lung cancer.

PubMed

Dickey, Mike; Roa, Wilson; Drodge, Suzanne; Ghosh, Sunita; Murray, Brad; Scrimger, Rufus; Gabos, Zsolt

2015-01-01

The primary objective of this study was to compare dosimetric variables as well as treatment times of multiple static fields (MSFs), conformal arcs (CAs), and volumetric modulated arc therapy (VMAT) techniques for the treatment of early stage lung cancer using stereotactic body radiotherapy (SBRT). Treatments of 23 patients previously treated with MSF of 48Gy to 95% of the planning target volume (PTV) in 4 fractions were replanned using CA and VMAT techniques. Dosimetric parameters of the Radiation Therapy Oncology Group (RTOG) 0915 trial were evaluated, along with the van׳t Riet conformation number (CN), monitor units (MUs), and actual and calculated treatment times. Paired t-tests for noninferiority were used to compare the 3 techniques. CA had significant dosimetric improvements over MSF for the ratio of the prescription isodose volume to PTV (R100%, p < 0.0001), the maximum dose 2cm away from the PTV (D2cm, p = 0.005), and van׳t Riet CN (p < 0.0001). CA was not statistically inferior to MSF for the 50% prescription isodose volume to PTV (R50%, p = 0.05). VMAT was significantly better than CA for R100% (p < 0.0001), R50% (p < 0.0001), D2cm (p = 0.006), and CN (p < 0.0001). CA plans had significantly shorter treatment times than those of VMAT (p < 0.0001). Both CA and VMAT planning showed significant dosimetric improvements and shorter treatment times over those of MSF. VMAT showed the most favorable dosimetry of all 3 techniques; however, the dosimetric effect of tumor motion was not evaluated. CA plans were significantly faster to treat, and minimize the interplay of tumor motion and dynamic multileaf collimator (MLC) motion effects. Given these results, CA has become the treatment technique of choice at our facility. Copyright © 2015 American Association of Medical Dosimetrists. Published by Elsevier Inc. All rights reserved.

Correlation between gamma index passing rate and clinical dosimetric difference for pre-treatment 2D and 3D volumetric modulated arc therapy dosimetric verification

PubMed Central

Jin, X; Yan, H; Han, C; Zhou, Y; Yi, J

2015-01-01

Objective: To investigate comparatively the percentage gamma passing rate (%GP) of two-dimensional (2D) and three-dimensional (3D) pre-treatment volumetric modulated arc therapy (VMAT) dosimetric verification and their correlation and sensitivity with percentage dosimetric errors (%DE). Methods: %GP of 2D and 3D pre-treatment VMAT quality assurance (QA) with different acceptance criteria was obtained by ArcCHECK® (Sun Nuclear Corporation, Melbourne, FL) for 20 patients with nasopharyngeal cancer (NPC) and 20 patients with oesophageal cancer. %DE were calculated from planned dose–volume histogram (DVH) and patients' predicted DVH calculated by 3DVH® software (Sun Nuclear Corporation). Correlation and sensitivity between %GP and %DE were investigated using Pearson's correlation coefficient (r) and receiver operating characteristics (ROCs). Results: Relatively higher %DE on some DVH-based metrics were observed for both patients with NPC and oesophageal cancer. Except for 2%/2 mm criterion, the average %GPs for all patients undergoing VMAT were acceptable with average rates of 97.11% ± 1.54% and 97.39% ± 1.37% for 2D and 3D 3%/3 mm criteria, respectively. The number of correlations for 3D was higher than that for 2D (21 vs 8). However, the general correlation was still poor for all the analysed metrics (9 out of 26 for 3D 3%/3 mm criterion). The average area under the curve (AUC) of ROCs was 0.66 ± 0.12 and 0.71 ± 0.21 for 2D and 3D evaluations, respectively. Conclusions: There is a lack of correlation between %GP and %DE for both 2D and 3D pre-treatment VMAT dosimetric evaluation. DVH-based dose metrics evaluation obtained from 3DVH will provide more useful analysis. Advances in knowledge: Correlation and sensitivity of %GP with %DE for VMAT QA were studied for the first time. PMID:25494412

A dosimetric uncertainty analysis for photon-emitting brachytherapy sources: report of AAPM Task Group No. 138 and GEC-ESTRO.

PubMed

DeWerd, Larry A; Ibbott, Geoffrey S; Meigooni, Ali S; Mitch, Michael G; Rivard, Mark J; Stump, Kurt E; Thomadsen, Bruce R; Venselaar, Jack L M

2011-02-01

This report addresses uncertainties pertaining to brachytherapy single-source dosimetry preceding clinical use. The International Organization for Standardization (ISO) Guide to the Expression of Uncertainty in Measurement (GUM) and the National Institute of Standards and Technology (NIST) Technical Note 1297 are taken as reference standards for uncertainty formalism. Uncertainties in using detectors to measure or utilizing Monte Carlo methods to estimate brachytherapy dose distributions are provided with discussion of the components intrinsic to the overall dosimetric assessment. Uncertainties provided are based on published observations and cited when available. The uncertainty propagation from the primary calibration standard through transfer to the clinic for air-kerma strength is covered first. Uncertainties in each of the brachytherapy dosimetry parameters of the TG-43 formalism are then explored, ending with transfer to the clinic and recommended approaches. Dosimetric uncertainties during treatment delivery are considered briefly but are not included in the detailed analysis. For low- and high-energy brachytherapy sources of low dose rate and high dose rate, a combined dosimetric uncertainty <5% (k=1) is estimated, which is consistent with prior literature estimates. Recommendations are provided for clinical medical physicists, dosimetry investigators, and source and treatment planning system manufacturers. These recommendations include the use of the GUM and NIST reports, a requirement of constancy of manufacturer source design, dosimetry investigator guidelines, provision of the lowest uncertainty for patient treatment dosimetry, and the establishment of an action level based on dosimetric uncertainty. These recommendations reflect the guidance of the American Association of Physicists in Medicine (AAPM) and the Groupe Européen de Curiethérapie-European Society for Therapeutic Radiology and Oncology (GEC-ESTRO) for their members and may also be used as guidance to manufacturers and regulatory agencies in developing good manufacturing practices for sources used in routine clinical treatments.

Comparison of Hyperspectral and Multispectral Satellites for Forest Alliance Classification in the San Francisco Bay Area

NASA Astrophysics Data System (ADS)

Clark, M. L.

2016-12-01

The goal of this study was to assess multi-temporal, Hyperspectral Infrared Imager (HyspIRI) satellite imagery for improved forest class mapping relative to multispectral satellites. The study area was the western San Francisco Bay Area, California and forest alliances (e.g., forest communities defined by dominant or co-dominant trees) were defined using the U.S. National Vegetation Classification System. Simulated 30-m HyspIRI, Landsat 8 and Sentinel-2 imagery were processed from image data acquired by NASA's AVIRIS airborne sensor in year 2015, with summer and multi-temporal (spring, summer, fall) data analyzed separately. HyspIRI reflectance was used to generate a suite of hyperspectral metrics that targeted key spectral features related to chemical and structural properties. The Random Forests classifier was applied to the simulated images and overall accuracies (OA) were compared to those from real Landsat 8 images. For each image group, broad land cover (e.g., Needle-leaf Trees, Broad-leaf Trees, Annual agriculture, Herbaceous, Built-up) was classified first, followed by a finer-detail forest alliance classification for pixels mapped as closed-canopy forest. There were 5 needle-leaf tree alliances and 16 broad-leaf tree alliances, including 7 Quercus (oak) alliance types. No forest alliance classification exceeded 50% OA, indicating that there was broad spectral similarity among alliances, most of which were not spectrally pure but rather a mix of tree species. In general, needle-leaf (Pine, Redwood, Douglas Fir) alliances had better class accuracies than broad-leaf alliances (Oaks, Madrone, Bay Laurel, Buckeye, etc). Multi-temporal data classifications all had 5-6% greater OA than with comparable summer data. For simulated data, HyspIRI metrics had 4-5% greater OA than Landsat 8 and Sentinel-2 multispectral imagery and 3-4% greater OA than HyspIRI reflectance. Finally, HyspIRI metrics had 8% greater OA than real Landsat 8 imagery. In conclusion, forest alliance classification was found to be a difficult remote sensing application with moderate resolution (30 m) satellite imagery; however, of the data tested, HyspIRI spectral metrics had the best performance relative to multispectral satellites.

Does a shift in host plants trigger speciation in the Alpine leaf beetle Oreina speciosissima (Coleoptera, Chrysomelidae)?

PubMed

Borer, Matthias; van Noort, Tom; Arrigo, Nils; Buerki, Sven; Alvarez, Nadir

2011-10-20

Within the Coleoptera, the largest order in the animal kingdom, the exclusively herbivorous Chrysomelidae are recognized as one of the most species rich beetle families. The evolutionary processes that have fueled radiation into the more than thirty-five thousand currently recognized leaf beetle species remain partly unresolved. The prominent role of leaf beetles in the insect world, their omnipresence across all terrestrial biomes and their economic importance as common agricultural pest organisms make this family particularly interesting for studying the mechanisms that drive diversification. Here we specifically focus on two ecotypes of the alpine leaf beetle Oreina speciosissima (Scop.), which have been shown to exhibit morphological differences in male genitalia roughly corresponding to the subspecies Oreina speciosissima sensu stricto and Oreina speciosissima troglodytes. In general the two ecotypes segregate along an elevation gradient and by host plants: Oreina speciosissima sensu stricto colonizes high forb vegetation at low altitude and Oreina speciosissima troglodytes is found in stone run vegetation at higher elevations. Both host plants and leaf beetles have a patchy geographical distribution. Through use of gene sequencing and genome fingerprinting (AFLP) we analyzed the genetic structure and habitat use of Oreina speciosissima populations from the Swiss Alps to examine whether the two ecotypes have a genetic basis. By investigating a wide range of altitudes and focusing on the structuring effect of habitat types, we aim to provide answers regarding the factors that drive adaptive radiation in this phytophagous leaf beetle. While little phylogenetic resolution was observed based on the sequencing of four DNA regions, the topology and clustering resulting from AFLP genotyping grouped specimens according to their habitat, mostly defined by plant associations. A few specimens with intermediate morphologies clustered with one of the two ecotypes or formed separate clusters consistent with habitat differences. These results were discussed in an ecological speciation framework. The question of whether this case of ecological differentiation occurred in sympatry or allopatry remains open. Still, the observed pattern points towards ongoing divergence between the two ecotypes which is likely driven by a recent shift in host plant use.

Dosimetric implications of the infiltrated injection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Castronovo, F.P.; McKusick, K.A.; Strauss, H.W.

1984-01-01

Following inadvertent infiltration of a radiopharmaceutical, there is variable and uncertain uptake in target tissue. Concomitantly, there is also a concern for the radiation dose to the infiltrated site. This investigation determined the clearance and radiation burdens from various radiopharmaceutical infiltrates in a rat model. Nine separate sites were studied for: Tc-99m microspheres; Tc-99m MDP; Ga-67 citrate; and Tl-201 chloride. Following sc injection on the shaven posteriors of anesthetized adult male Sprague-Dawley rats, gamma camera and computer data were collected up to 24 hours. The resulting data were expressed semilogarithmically as the mean (N = 9) of the ''% retainedmore » at site'' as a f(time) after injection. Nonparticulate agents showed a tri-exponential release pattern from each site, whereas the microspheres remained for an extended period of time. Using these pharma-cokinetic curves, the % remaining at each site for various times, and rems/mCi per lcc infiltrate was determined.« less

Dosimetric characteristics of the University of Washington Clinical Neutron Therapy System

NASA Astrophysics Data System (ADS)

Moffitt, Gregory B.; Stewart, Robert D.; Sandison, George A.; Goorley, John T.; Argento, David C.; Jevremovic, Tatjana; Emery, Robert; Wootton, Landon S.; Parvathaneni, Upendra; Laramore, George E.

2018-05-01

The University of Washington (UW) Clinical Neutron Therapy System (CNTS), which generates high linear energy transfer fast neutrons through interactions of 50.5 MeV protons incident on a Be target, has depth-dose characteristics similar to 6 MV x-rays. In contrast to the fixed beam angles and primitive blocking used in early clinical trials of neutron therapy, the CNTS has a gantry with a full 360° of rotation, internal wedges, and a multi-leaf collimator (MLC). Since October of 1984, over 3178 patients have received conformal neutron therapy treatments using the UW CNTS. In this work, the physical and dosimetric characteristics of the CNTS are documented through comparisons of measurements and Monte Carlo simulations. A high resolution computed tomography scan of the model 17 ionization chamber (IC-17) has also been used to improve the accuracy of simulations of the absolute calibration geometry. The response of the IC-17 approximates well the kinetic energy released per unit mass (KERMA) in water for neutrons and photons for energies from a few tens of keV up to about 20 MeV. Above 20 MeV, the simulated model 17 ion chamber response is 20%–30% higher than the neutron KERMA in water. For CNTS neutrons, simulated on- and off-axis output factors in water match measured values within ~2%  ±  2% for rectangular and irregularly shaped field with equivalent square areas ranging in a side dimension from 2.8 cm to 30.7 cm. Wedge factors vary by less than 1.9% of the measured dose in water for clinically relevant field sizes. Simulated tissue maximum ratios in water match measured values within 3.3% at depths up to 20 cm. Although the absorbed dose for water and adipose tissue are within 2% at a depth of 1.7 cm, the absorbed dose in muscle and bone can be as much as 12 to 40% lower than the absorbed dose in water. The reported studies are significant from a historical perspective and as additional validation of a new tool for patient quality assurance and as an aid in ongoing efforts to clinically implement advanced treatment techniques, such as intensity modulated neutron therapy, at the UW.

FLUKA simulation studies on in-phantom dosimetric parameters of a LINAC-based BNCT

NASA Astrophysics Data System (ADS)

Ghal-Eh, N.; Goudarzi, H.; Rahmani, F.

2017-12-01

The Monte Carlo simulation code, FLUKA version 2011.2c.5, has been used to estimate the in-phantom dosimetric parameters for use in BNCT studies. The in-phantom parameters of a typical Snyder head, which are necessary information prior to any clinical treatment, have been calculated with both FLUKA and MCNPX codes, which exhibit a promising agreement. The results confirm that FLUKA can be regarded as a good alternative for the MCNPX in BNCT dosimetry simulations.

LabVIEW-based control and acquisition system for the dosimetric characterization of a silicon strip detector.

PubMed

Ovejero, M C; Pérez Vega-Leal, A; Gallardo, M I; Espino, J M; Selva, A; Cortés-Giraldo, M A; Arráns, R

2017-02-01

The aim of this work is to present a new data acquisition, control, and analysis software system written in LabVIEW. This system has been designed to obtain the dosimetry of a silicon strip detector in polyethylene. It allows the full automation of the experiments and data analysis required for the dosimetric characterization of silicon detectors. It becomes a useful tool that can be applied in the daily routine check of a beam accelerator.

Ethylene-induced differential gene expression during abscission of citrus leaves

PubMed Central

Merelo, Paz; Cercós, Manuel; Tadeo, Francisco R.; Talón, Manuel

2008-01-01

The main objective of this work was to identify and classify genes involved in the process of leaf abscission in Clementina de Nules (Citrus clementina Hort. Ex Tan.). A 7 K unigene citrus cDNA microarray containing 12 K spots was used to characterize the transcriptome of the ethylene-induced abscission process in laminar abscission zone-enriched tissues and the petiole of debladed leaf explants. In these conditions, ethylene induced 100% leaf explant abscission in 72 h while, in air-treated samples, the abscission period started later and took 240 h. Gene expression monitored during the first 36 h of ethylene treatment showed that out of the 12 672 cDNA microarray probes, ethylene differentially induced 725 probes distributed as follows: 216 (29.8%) probes in the laminar abscission zone and 509 (70.2%) in the petiole. Functional MIPS classification and manual annotation of differentially expressed genes highlighted key processes regulating the activation and progress of the cell separation that brings about abscission. These included cell-wall modification, lipid transport, protein biosynthesis and degradation, and differential activation of signal transduction and transcription control pathways. Expression data associated with the petiole indicated the occurrence of a double defensive strategy mediated by the activation of a biochemical programme including scavenging ROS, defence and PR genes, and a physical response mostly based on lignin biosynthesis and deposition. This work identifies new genes probably involved in the onset and development of the leaf abscission process and suggests a different but co-ordinated and complementary role for the laminar abscission zone and the petiole during the process of abscission. PMID:18515267

Influence of light, temperature and salinity on dissolved organic carbon exudation rates in Zostera marina L.

PubMed Central

2012-01-01

Background Marine angiosperms, seagrasses, are sentinel species of marine ecosystem health and function. Seagrass carbon budgets provide insight on the minimum requirements needed to maintain this valuable resource. Carbon budgets are a balance between C fixation, growth, storage and loss rates, most of which are well characterized. However, relatively few measurements of dissolved organic carbon (DOC) leaf exudation or rhizodeposition rates exist for most seagrass species. Here I evaluate how eelgrass (Zostera marina L.) DOC exudation is affected by a single factor manipulation (light, temperature or salinity). Eelgrass plants were hydroponically exposed to treatments in experimental chambers (separate leaf and rhizome/root compartments) with artificial seawater medium. Regression analysis of changes in the DOC concentration through time was used to calculate DOC exudation rates. Results Exudation rates were similar across all treatments in all experiments. For all experiments, pooled leaf DOC exudation ranged between 0.032 and 0.069 mg C gdw-1 h-1, while rhizodeposition ranged between 0.024 and 0.045 mg C gdw-1 h-1. These rates are consistent with previously published values and provide first-order estimates for mechanistic models. Conclusions Zostera marina carbon losses from either leaf exudation or rhizodeposition account for a small proportion of gross primary production (1.2-4.6%) and appear to be insensitive to short-term (e.g., hours to days) environmental variations in chamber experiments. Based on these preliminary experiments, I suggest that Z. marina DOC exudation may be a passive process and not an active transport process. PMID:22938529

Antibacterial activities and antioxidant capacity of Aloe vera

PubMed Central

2013-01-01

Background The aim of this study was to identify, quantify, and compare the phytochemical contents, antioxidant capacities, and antibacterial activities of Aloe vera lyophilized leaf gel (LGE) and 95% ethanol leaf gel extracts (ELGE) using GC-MS and spectrophotometric methods. Results Analytically, 95% ethanol is less effective than ethyl acetate/diethyl ether or hexane (in the case of fatty acids) extractions in separating phytochemicals for characterization purposes. However, although fewer compounds are extracted in the ELGE, they are approximately 345 times more concentrated as compared to the LGE, hence justifying ELGE use in biological efficacy studies in vivo. Individual phytochemicals identified included various phenolic acids/polyphenols, phytosterols, fatty acids, indoles, alkanes, pyrimidines, alkaloids, organic acids, aldehydes, dicarboxylic acids, ketones, and alcohols. Due to the presence of the antioxidant polyphenols, indoles, and alkaloids, the A. vera leaf gel shows antioxidant capacity as confirmed by ORAC and FRAP analyses. Both analytical methods used show the non-flavonoid polyphenols to contribute to the majority of the total polyphenol content. Three different solvents such as aqueous, ethanol, and acetone were used to extract the bioactive compounds from the leaves of A. vera to screen the antibacterial activity selected human clinical pathogens by agar diffusion method. The maximum antibacterial activities were observed in acetone extracts (12 ± 0.45, 20 ± 0.35, 20 ± 0.57, and 15 ± 0.38 nm) other than aqueous and ethanol extracts. Conclusion Due to its phytochemical composition, A. vera leaf gel may show promise in alleviating symptoms associated with/or prevention of cardiovascular diseases, cancer, neurodegeneration, and diabetes. PMID:23870710

Mapping Vineyard Leaf Area Using Mobile Terrestrial Laser Scanners: Should Rows be Scanned On-the-Go or Discontinuously Sampled?

PubMed Central

del-Moral-Martínez, Ignacio; Rosell-Polo, Joan R.; Company, Joaquim; Sanz, Ricardo; Escolà, Alexandre; Masip, Joan; Martínez-Casasnovas, José A.; Arnó, Jaume

2016-01-01

The leaf area index (LAI) is defined as the one-side leaf area per unit ground area, and is probably the most widely used index to characterize grapevine vigor. However, LAI varies spatially within vineyard plots. Mapping and quantifying this variability is very important for improving management decisions and agricultural practices. In this study, a mobile terrestrial laser scanner (MTLS) was used to map the LAI of a vineyard, and then to examine how different scanning methods (on-the-go or discontinuous systematic sampling) may affect the reliability of the resulting raster maps. The use of the MTLS allows calculating the enveloping vegetative area of the canopy, which is the sum of the leaf wall areas for both sides of the row (excluding gaps) and the projected upper area. Obtaining the enveloping areas requires scanning from both sides one meter length section along the row at each systematic sampling point. By converting the enveloping areas into LAI values, a raster map of the latter can be obtained by spatial interpolation (kriging). However, the user can opt for scanning on-the-go in a continuous way and compute 1-m LAI values along the rows, or instead, perform the scanning at discontinuous systematic sampling within the plot. An analysis of correlation between maps indicated that MTLS can be used discontinuously in specific sampling sections separated by up to 15 m along the rows. This capability significantly reduces the amount of data to be acquired at field level, the data storage capacity and the processing power of computers. PMID:26797618

Mapping Vineyard Leaf Area Using Mobile Terrestrial Laser Scanners: Should Rows be Scanned On-the-Go or Discontinuously Sampled?

PubMed

del-Moral-Martínez, Ignacio; Rosell-Polo, Joan R; Company, Joaquim; Sanz, Ricardo; Escolà, Alexandre; Masip, Joan; Martínez-Casasnovas, José A; Arnó, Jaume

2016-01-19

The leaf area index (LAI) is defined as the one-side leaf area per unit ground area, and is probably the most widely used index to characterize grapevine vigor. However, LAI varies spatially within vineyard plots. Mapping and quantifying this variability is very important for improving management decisions and agricultural practices. In this study, a mobile terrestrial laser scanner (MTLS) was used to map the LAI of a vineyard, and then to examine how different scanning methods (on-the-go or discontinuous systematic sampling) may affect the reliability of the resulting raster maps. The use of the MTLS allows calculating the enveloping vegetative area of the canopy, which is the sum of the leaf wall areas for both sides of the row (excluding gaps) and the projected upper area. Obtaining the enveloping areas requires scanning from both sides one meter length section along the row at each systematic sampling point. By converting the enveloping areas into LAI values, a raster map of the latter can be obtained by spatial interpolation (kriging). However, the user can opt for scanning on-the-go in a continuous way and compute 1-m LAI values along the rows, or instead, perform the scanning at discontinuous systematic sampling within the plot. An analysis of correlation between maps indicated that MTLS can be used discontinuously in specific sampling sections separated by up to 15 m along the rows. This capability significantly reduces the amount of data to be acquired at field level, the data storage capacity and the processing power of computers.

Impact of physiology, structure and BRDF in hyperspectral time series of a Citrus orchard

NASA Astrophysics Data System (ADS)

Stuckens, J.; Dzikiti, S.; Verstraeten, W. W.; Verreynne, J. S.; Swinnen, R.; Coppin, P.

2010-05-01

Monitoring of plant production systems using remote sensing requires an understanding of the mechanisms in which physiological and structural changes as well as the quality and direction of incident light alter the measured canopy reflectance. Due to the evergreen nature of Citrus, the benefits of year-round monitoring of spectral changes are counterweighted by more subtle changes and seasonal trends than in other perennials. This study presents the results of a 14 months field measurement campaign in a commercial Citrus sinensis ‘Midknight Valencia' orchard in Wellington, Western Cape Province, South-Africa. Hyperspectral data were collected of canopy and leaf reflectance (350 - 2500 nm) of 16 representative trees at monthly intervals and supplemented with local climatology, orchard management records, sap stream, water potential and leaf and soil nutrient analysis. The aim of this research is to translate spectral changes and trends at the leaf and at canopy levels into physiological processes such as plant nutrient and carbohydrate balances and stress responses. Specific research questions include the spectral detection of flowering (date of anthesis, flowering intensity), fruit drop, fruit number and coloration, vegetative flushes, leaf senescence and drop and pruning. Attention is paid to the detection and the impact of sunburn (photo-damage). In order to separate physiological and structural changes from changes caused by seasonal changes in solar elevation during measurement time (bidirectional reflectance) a normalization function is constructed using simulated and measured data. Additional research is done to up-scale measurements from tree level to orchard level, which includes the tree variability, the influence of soil and weeds and different amounts of shading.

Temporal and Spatial Expression of a Polygalacturonase during Leaf and Flower Abscission in Oilseed Rape and Arabidopsis1

PubMed Central

González-Carranza, Zinnia Haydé; Whitelaw, Catherine Ann; Swarup, Ranjan; Roberts, Jeremy Alan

2002-01-01

During leaf abscission in oilseed rape (Brassica napus), cell wall degradation is brought about by the action of several hydrolytic enzymes. One of these is thought to be polygalacturonase (PG). Degenerate primers were used to isolate a PG cDNA fragment by reverse transcriptase-polymerase chain reaction from RNA extracted from ethylene-promoted leaf abscission zones (AZs), and in turn a full-length clone (CAW471) from an oilseed rape AZ cDNA library. The highest homology of this cDNA (82%) was to an Arabidopsis sequence that was predicted to encode a PG protein. Analysis of expression revealed that CAW471 mRNA accumulated in the AZ of leaves and reached a peak 24 h after ethylene treatment. Ethylene-promoted leaf abscission in oilseed rape was not apparent until 42 h after exposure to the gas, reaching 50% at 48 h and 100% by 56 h. In floral organ abscission, expression of CAW471 correlated with cell separation. Genomic libraries from oilseed rape and Arabidopsis were screened with CAW471 and the respective genomic clones PGAZBRAN and PGAZAT isolated. Characterization of these PG genes revealed that they had substantial homology within both the coding regions and in the 5′-upstream sequences. Fusion of a 1,476-bp 5′-upstream sequence of PGAZAT to β-glucuronidase or green fluorescent protein and transformation of Arabidopsis revealed that this fragment was sufficient to drive expression of these reporter genes in the AZs at the base of the anther filaments, petals, and sepals. PMID:11842157

Gas exchange and leaf anatomy of a C3-CAM hybrid, Yucca gloriosa (Asparagaceae).

PubMed

Heyduk, Karolina; Burrell, Nia; Lalani, Falak; Leebens-Mack, Jim

2016-03-01

While the majority of plants use the typical C3 carbon metabolic pathway, ~6% of angiosperms have adapted to carbon limitation as a result of water stress by employing a modified form of photosynthesis known as Crassulacean acid metabolism (CAM). CAM plants concentrate carbon in the cells by temporally separating atmospheric carbon acquisition from fixation into carbohydrates. CAM has been studied for decades, but the evolutionary progression from C3 to CAM remains obscure. In order to better understand the morphological and physiological characteristics associated with CAM photosynthesis, phenotypic variation was assessed in Yucca aloifolia, a CAM species, Yucca filamentosa, a C3 species, and Yucca gloriosa, a hybrid species derived from these two yuccas exhibiting intermediate C3-CAM characteristics. Gas exchange, titratable leaf acidity, and leaf anatomical traits of all three species were assayed in a common garden under well-watered and drought-stressed conditions. Yucca gloriosa showed intermediate phenotypes for nearly all traits measured, including the ability to acquire carbon at night. Using the variation found among individuals of all three species, correlations between traits were assessed to better understand how leaf anatomy and CAM physiology are related. Yucca gloriosa may be constrained by a number of traits which prevent it from using CAM to as high a degree as Y. aloifolia. The intermediate nature of Y. gloriosa makes it a promising system in which to study the evolution of CAM. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Larvicidal effect of aqueous and ethanolic extracts of Senna alata on Anopheles gambiae, Culex quinquefasciatus and Aedes aegypti.

PubMed

Edwin, Ubulom Peace Mayen; Nyiutaha, Imandeh Godwin; Essien, Akpabio Eno; Nnamdi, Opara Kenneth; Sunday, Ekanem Mfon

2013-05-01

Senna alata is locally used in South Eastern Nigeria in the treatment of several infections which include ringworm and other parasitic skin diseases.The larvicidal activities of aqueous and ethanolic leaf and stem extracts of S. alata were evaluated in static bioassays, on fourth instar larvae of Anopheles gambiae, Culex quinquefasciatus and Aedes aegypti, at extract concentrations of 0.15, 0.30, 0.45, 0.60 and 0.75% w/v, for 72 hours. Mortality of larvae exposed to the different extracts increased with increase in extract concentration and time of exposure. This study revealed a differential potency of the extracts used and a difference in susceptibility of larvae to the extracts as evident by the 72hLC₅₀ values obtained. The leaf extract proved to be more lethal to the larvae than the stem extract as judged by the 72hLC₅₀ values obtained both for the aqueous as well as the ethanolic extracts assayed. Phytochemical screening of the plant parts investigated revealed the presence of some plant metabolites, which have been reported in separate studies to be lethal to mosquito larvae. Results obtained from this study suggest that the leaf and stem extracts of S. alata possess a promising larvicidal potential which can be exploited in mosquito vector control.

Genetic structure and evolution of natural populations of viruses causing the tomato yellow leaf curl disease in Spain.

PubMed

Font, María Isabel; Rubio, Luis; Martínez-Culebras, Pedro Vicente; Jordá, Concepción

2007-09-01

The population structure and genetic variation of two begomoviruses: tomato yellow leaf curl Sardinia virus (TYLCSV) and tomato yellow leaf curl virus (TYLCV) in tomato crops of Spain were studied from 1997 until 2001. Restriction digestion of a genomic region comprised of the CP coat protein gene (CPR) of 358 TYLC virus isolates enabled us to classify them into 14 haplotypes. Nucleotide sequences of two genomic regions: CPR, and the surrounding intergenic region (SIR) were determined for at least two isolates per haplotype. SIR was more variable than CPR and showed multiple recombination events whereas no recombination was detected within CPR. In all geographic regions except Murcia, the population was, or evolved to be composed of one predominant haplotype with a low genetic diversity (<0.0180). In Murcia, two successive changes of the predominant haplotype were observed in the best studied population. Phylogenetic analysis showed that the TYLCSV sequences determined clustered with sequences obtained from the GenBank of other TYLCSV Spanish isolates which were clearly separated from TYLCSV Italian isolates. Most of our TYLCV sequences were similar to those of isolates from Japan and Portugal, and the sequences obtained from TYLCV isolates from the Canary island of Lanzarote were similar to those of Caribbean TYLCV isolates.

Effective protein extraction protocol for proteomics studies of Jerusalem artichoke leaves.

PubMed

Zhang, Meide; Shen, Shihua

2013-07-01

Protein extraction is a crucial step for proteomics studies. To establish an effective protein extraction protocol suitable for two-dimensional electrophoresis (2DE) analysis in Jerusalem artichoke (Helianthus tuberosus L.), three different protein extraction methods-trichloroacetic acid/acetone, Mg/NP-40, and phenol/ammonium acetate-were evaluated using Jerusalem artichoke leaves as source materials. Of the three methods, trichloroacetic acid/acetone yielded the best protein separation pattern and highest number of protein spots in 2DE analysis. Proteins highly abundant in leaves, such as Rubisco, are typically problematic during leaf 2DE analysis, however, and this disadvantage was evident using trichloroacetic acid/acetone. To reduce the influence of abundant proteins on the detection of low-abundance proteins, we optimized the trichloroacetic acid/acetone method by incorporating a PEG fractionation approach. After optimization, 363 additional (36.2%) protein spots were detected on the 2DE gel. Our results suggest that trichloroacetic acid/acetone method is a better protein extraction technique than Mg/NP-40 and phenol/ammonium acetate in Jerusalem artichoke leaf 2DE analysis, and that trichloroacetic acid/acetone method combined with PEG fractionation procedure is the most effective approach for leaf 2DE analysis of Jerusalem artichoke. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and characterization of CaF2:Dy nanophosphor for dosimetric application

NASA Astrophysics Data System (ADS)

Bhadane, Mahesh S.; Patil, B. J.; Dahiwale, S. S.; Kulkarni, M. S.; Bhatt, B. C.; Bhoraskar, V. N.; Dhole, S. D.

2015-06-01

In this work, nanoparticles (NPs) of dysprosium doped calcium fluoride (CaF2:Dy) 1 mol % has been prepared using simple chemical co-precipitation method and its thermoluminescence (TL) dosimetric properties were studied. The synthesized nanoparticle sample was characterized by X-ray diffraction (XRD) and the particle size of face centered cubic phase NPs was found around 30 nm. The shape, morphology and size were also observed by scanning electron microscopy (SEM). From gamma irradiated CaF2:Dy TL curves, it was observed that the total areas of all the glow peak intensities are dramatically changed with increase in annealing temperature. Further, TL glow curve of the CaF2:Dy at 183 °C annealed at 400 °C, showed very sharp linear response in the dose range from 1 Gy to 750 Gy. This linear response of CaF2:Dy nanophosphor as a function of gamma dose is very useful from radiation dosimetric point of view.

Determination of dosimetric quantities in pediatric abdominal computed tomography scans*

PubMed Central

Jornada, Tiago da Silva; da Silva, Teógenes Augusto

2014-01-01

Objective Aiming at contributing to the knowledge on doses in computed tomography (CT), this study has the objective of determining dosimetric quantities associated with pediatric abdominal CT scans, comparing the data with diagnostic reference levels (DRL). Materials and methods The study was developed with a Toshiba Asteion single-slice CT scanner and a GE BrightSpeed multi-slice CT unit in two hospitals. Measurements were performed with a pencil-type ionization chamber and a 16 cm-diameter polymethylmethacrylate trunk phantom. Results No significant difference was observed in the values for weighted air kerma index (CW), but the differences were relevant in values for volumetric air kerma index (CVOL), air kerma-length product (PKL,CT) and effective dose. Conclusion Only the CW values were lower than the DRL, suggesting that dose optimization might not be necessary. However, PKL,CT and effective dose values stressed that there still is room for reducing pediatric radiation doses. The present study emphasizes the importance of determining all dosimetric quantities associated with CT scans. PMID:25741103

JCCRER Project 2.3 -- Deterministic effects of occupational exposure to radiation. Phase 1: Feasibility study; Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Okladnikova, N.; Pesternikova, V.; Sumina, M.

1998-12-01

Phase 1 of Project 2.3, a short-term collaborative Feasibility Study, was funded for 12 months starting on 1 February 1996. The overall aim of the study was to determine the practical feasibility of using the dosimetric and clinical data on the MAYAK worker population to study the deterministic effects of exposure to external gamma radiation and to internal alpha radiation from inhaled plutonium. Phase 1 efforts were limited to the period of greatest worker exposure (1948--1954) and focused on collaboratively: assessing the comprehensiveness, availability, quality, and suitability of the Russian clinical and dosimetric data for the study of deterministic effects;more » creating an electronic data base containing complete clinical and dosimetric data on a small, representative sample of MAYAK workers; developing computer software for the testing of a currently used health risk model of hematopoietic effects; and familiarizing the US team with the Russian diagnostic criteria and techniques used in the identification of Chronic Radiation Sickness.« less

Assessing the influence of biogeographical region and phylogenetic history on chemical defences and herbivory in Quercus species.

PubMed

Moreira, Xoaquín; Abdala-Roberts, Luis; Galmán, Andrea; Francisco, Marta; Fuente, María de la; Butrón, Ana; Rasmann, Sergio

2018-06-07

Biogeographical factors and phylogenetic history are key determinants of inter-specific variation in plant defences. However, few studies have conducted broad-scale geographical comparisons of plant defences while controlling for phylogenetic relationships, and, in doing so, none have separated constitutive from induced defences. This gap has limited our understanding of how historical or large-scale processes mediate biogeographical patterns in plant defences since these may be contingent upon shared evolutionary history and phylogenetic constraints. We conducted a phylogenetically-controlled experiment testing for differences in constitutive leaf chemical defences and their inducibility between Palearctic and Nearctic oak species (Quercus, total 18 species). We induced defences in one-year old plants by inflicting damage by gypsy moth larvae (Lymantria dispar), estimated the amount of leaf area consumed, and quantified various groups of phenolic compounds. There was no detectable phylogenetic signal for constitutive or induced levels of most defensive traits except for constitutive condensed tannins, as well as no phylogenetic signal in leaf herbivory. We did, however, find marked differences in defence levels between oak species from each region: Palearctic species had higher levels of constitutive condensed tannins, but less constitutive lignins and less constitutive and induced hydrolysable tannins compared with Nearctic species. Additionally, Palearctic species had lower levels of leaf damage compared with Nearctic species. These differences in leaf damage, lignins and hydrolysable (but not condensed) tannins were lost after accounting for phylogeny, suggesting that geographical structuring of phylogenetic relationships mediated biogeographical differences in defences and herbivore resistance. Together, these findings suggest that historical processes and large-scale drivers have shaped differences in allocation to constitutive defences (and in turn resistance) between Palearctic and Nearctic oaks. Moreover, although evidence of phylogenetic conservatism in the studied traits is rather weak, shared evolutionary history appears to mediate some of these biogeographical patterns in allocation to chemical defences. Copyright © 2018 Elsevier Ltd. All rights reserved.

Accumulation and ultrastructural distribution of copper in Elsholtzia splendens *

PubMed Central

Peng, Hong-yun; Yang, Xiao-e; Tian, Sheng-ke

2005-01-01

Copper accumulation and intracellular distribution in Elsholtzia splendens, a native Chinese Cu-tolerant and accumulating plant species, was investigated by transmission electron microscope (TEM) and gradient centrifugation techniques. Copper concentrations in roots, stems and leaves of E. splendens increased with increasing Cu levels in solution. After exposure to 500 μmol/L Cu for 8 d, about 1000 mg/kg Cu were accumulated in the stem and 250 mg/kg Cu in the leaf of E. splendens. At 50 µmol/L Cu, no significant toxicity was observed in the chloroplast and mitochondrion within its leaf cells, but separation appeared at the cytoplasm and the cell wall within the root cells. At >250 µmol/L Cu, both root and leaf organelles in E. splendens were damaged heavily by excessive Cu in vivo. Copper subcellular localization in the plant leaf after 8 days’ exposure to 500 µmol/L Cu using gradient centrifugation techniques was found to be decreased in the order: chloroplast>cell wall>soluble fraction>other organelles. The plant root cell wall was found to be the site of highest Cu localization. Increase of Cu exposure time from 8 d to 16 d, increased slightly Cu concentration in cell wall fraction in roots and leaves, while that in the chloroplast fraction decreased in leaves of the plants grown in both 0.25 μmol/L and 500 μmol/L Cu. TEM confirmed that much more Cu localized in cell walls of E. splendens roots and leaves, but also more Cu localized in E. splendens’ chloroplast when the plant is exposed to Cu levels>250 μmol/L, as compared to those in the plant grown in 0.25 μmol/L Cu. Copper treatment at levels>250 μmol/L caused pronounced damage in the leaf chloroplast and root organelles. Copper localization in cell walls and chloroplasts could mainly account for the high detoxification of Cu in E. splendens. PMID:15822140

Chinese tallow trees (Triadica sebifera) from the invasive range outperform those from the native range with an active soil community or phosphorus fertilization.

PubMed

Zhang, Ling; Zhang, Yaojun; Wang, Hong; Zou, Jianwen; Siemann, Evan

2013-01-01

Two mechanisms that have been proposed to explain success of invasive plants are unusual biotic interactions, such as enemy release or enhanced mutualisms, and increased resource availability. However, while these mechanisms are usually considered separately, both may be involved in successful invasions. Biotic interactions may be positive or negative and may interact with nutritional resources in determining invasion success. In addition, the effects of different nutrients on invasions may vary. Finally, genetic variation in traits between populations located in introduced versus native ranges may be important for biotic interactions and/or resource use. Here, we investigated the roles of soil biota, resource availability, and plant genetic variation using seedlings of Triadica sebifera in an experiment in the native range (China). We manipulated nitrogen (control or 4 g/m(2)), phosphorus (control or 0.5 g/m(2)), soil biota (untreated or sterilized field soil), and plant origin (4 populations from the invasive range, 4 populations from the native range) in a full factorial experiment. Phosphorus addition increased root, stem, and leaf masses. Leaf mass and height growth depended on population origin and soil sterilization. Invasive populations had higher leaf mass and growth rates than native populations did in fresh soil but they had lower, comparable leaf mass and growth rates in sterilized soil. Invasive populations had higher growth rates with phosphorus addition but native ones did not. Soil sterilization decreased specific leaf area in both native and exotic populations. Negative effects of soil sterilization suggest that soil pathogens may not be as important as soil mutualists for T. sebifera performance. Moreover, interactive effects of sterilization and origin suggest that invasive T. sebifera may have evolved more beneficial relationships with the soil biota. Overall, seedlings from the invasive range outperformed those from the native range, however, an absence of soil biota or low phosphorus removed this advantage.

Chinese Tallow Trees (Triadica sebifera) from the Invasive Range Outperform Those from the Native Range with an Active Soil Community or Phosphorus Fertilization

PubMed Central

Zhang, Ling; Zhang, Yaojun; Wang, Hong; Zou, Jianwen; Siemann, Evan

2013-01-01

Two mechanisms that have been proposed to explain success of invasive plants are unusual biotic interactions, such as enemy release or enhanced mutualisms, and increased resource availability. However, while these mechanisms are usually considered separately, both may be involved in successful invasions. Biotic interactions may be positive or negative and may interact with nutritional resources in determining invasion success. In addition, the effects of different nutrients on invasions may vary. Finally, genetic variation in traits between populations located in introduced versus native ranges may be important for biotic interactions and/or resource use. Here, we investigated the roles of soil biota, resource availability, and plant genetic variation using seedlings of Triadica sebifera in an experiment in the native range (China). We manipulated nitrogen (control or 4 g/m2), phosphorus (control or 0.5 g/m2), soil biota (untreated or sterilized field soil), and plant origin (4 populations from the invasive range, 4 populations from the native range) in a full factorial experiment. Phosphorus addition increased root, stem, and leaf masses. Leaf mass and height growth depended on population origin and soil sterilization. Invasive populations had higher leaf mass and growth rates than native populations did in fresh soil but they had lower, comparable leaf mass and growth rates in sterilized soil. Invasive populations had higher growth rates with phosphorus addition but native ones did not. Soil sterilization decreased specific leaf area in both native and exotic populations. Negative effects of soil sterilization suggest that soil pathogens may not be as important as soil mutualists for T. sebifera performance. Moreover, interactive effects of sterilization and origin suggest that invasive T. sebifera may have evolved more beneficial relationships with the soil biota. Overall, seedlings from the invasive range outperformed those from the native range, however, an absence of soil biota or low phosphorus removed this advantage. PMID:24023930

Common allometric response of open-grown leader shoots to tree height in co-occurring deciduous broadleaved trees

PubMed Central

Miyata, Rie; Kubo, Takuya; Nabeshima, Eri; Kohyama, Takashi S.

2011-01-01

Background and Aims Morphology of crown shoots changes with tree height. The height of forest trees is usually correlated with the light environment and this makes it difficult to separate the effects of tree size and of light conditions on the morphological plasticity of crown shoots. This paper addresses the tree-height dependence of shoot traits under full-light conditions where a tree crown is not shaded by other crowns. Methods Focus is given to relationships between tree height and top-shoot traits, which include the shoot's leaf-blades and non-leafy mass, its total leaf-blade area and the length and basal diameter of the shoot's stem. We examine the allometric characteristics of open-grown current-year leader shoots at the tops of forest tree crowns up to 24 m high and quantify their responses to tree height in 13 co-occurring deciduous hardwood species in a cool-temperate forest in northern Japan. Key Results Dry mass allocated to leaf blades in a leader shoot increased with tree height in all 13 species. Specific leaf area decreased with tree height. Stem basal area was almost proportional to total leaf area in a leader shoot, where the proportionality constant did not depend on tree height, irrespective of species. Stem length for a given stem diameter decreased with tree height. Conclusions In the 13 species observed, height-dependent changes in allometry of leader shoots were convergent. This finding suggests that there is a common functional constraint in tree-height development. Under full-light conditions, leader shoots of tall trees naturally experience more severe water stress than those of short trees. We hypothesize that the height dependence of shoot allometry detected reflects an integrated response to height-associated water stress, which contributes to successful crown expansion and height gain. PMID:21914698

Genotype, development and tissue-derived variation of cell-wall properties in the lignocellulosic energy crop Miscanthus

DOE Office of Scientific and Technical Information (OSTI.GOV)

da Costa, Ricardo M. F.; Lee, Scott J.; Allison, Gordon G.

Species and hybrids of the genus Miscanthus contain attributes that make them front-runners among current selections of dedicated bioenergy crops. A key trait for plant biomass conversion to biofuels and biomaterials is cell-wall quality; however, knowledge of cell-wall composition and biology in Miscanthus species is limited. This study presents data on cell-wall compositional changes as a function of development and tissue type across selected genotypes, and considers implications for the development of miscanthus as a sustainable and renewable bioenergy feedstock. Cell-wall biomass was analysed for 25 genotypes, considering different developmental stages and stem vs. leaf compositional variability, by Fourier transformmore » mid-infrared spectroscopy and lignin determination. In addition, a Clostridium phytofermentans bioassay was used to assess cell-wall digestibility and conversion to ethanol. Important cell-wall compositional differences between miscanthus stem and leaf samples were found to be predominantly associated with structural carbohydrates. Lignin content increased as plants matured and was higher in stem tissues. Although stem lignin concentration correlated inversely with ethanol production, no such correlation was observed for leaves. Leaf tissue contributed significantly to total above-ground biomass at all stages, although the extent of this contribution was genotype-dependent. In conclusion, it is hypothesized that divergent carbohydrate compositions and modifications in stem and leaf tissues are major determinants for observed differences in cell-wall quality. The findings indicate that improvement of lignocellulosic feedstocks should encompass tissue-dependent variation as it affects amenability to biological conversion. For gene-trait associations relating to cell-wall quality, the data support the separate examination of leaf and stem composition, as tissue-specific traits may be masked by considering only total above-ground biomass samples, and sample variability could be mostly due to varying tissue contributions to total biomass.« less

Genetic structure of Zymoseptoria tritici in northern France at region, field, plant and leaf layer scales.

PubMed

Siah, Ali; Bomble, Myriam; Tisserant, Benoit; Cadalen, Thierry; Holvoet, Maxime; Hilbert, Jean-Louis; Halama, Patrice; Reignault, Philippe Lucien

2018-04-16

Population genetic structure of the worldwide-distributed wheat pathogen Zymoseptoria tritici has been extensively studied at large geographical scales, but to a much less extent at small or local spatial scales. A total of 627 single-conidial fungal isolates were sampled from several locations in northern France (Hauts-de-France Region) to assess fungal genetic structure at region, field, plant and leaf layer scales, using highly polymorphic microsatellite markers and mating type idiomorphs. Important and overall similar levels of both gene and genotype diversities (gene diversity values ≥ 0.44 and haplotype frequencies ≥ 94 %) were found at all the examined scales. Such rates of diversity are likely due to an active sexual recombination in the investigated areas, as revealed by equal proportions of the two mating types scored in all sampled populations. Interestingly, a rare occurrence of clones among lesions from a same leaf, as well as among leaves from different plant leaf layers (e.g. upper vs lower leaves), was highlighted, indicating that ascospores contribute much more than expected to Z. tritci epidemics, compared to pycnidiospores. Population structure and AMOVA analyses revealed significant genetic differentiation at the regional scale (GST = 0.23) and, as expected, not at the other more local scales (GST ≤ 0.01). Further analyses using Bayesian and unweighted neighbor-joining statistical methods detected six genetic clusters within the regional population, overall distributed according to the locations from which the isolates were sampled. Neither clear directional relative migration linked to the geographical distribution of the locations, nor isolation by distance, were observed. Separate evolutionary trajectories caused by selection and adaptations to habitat heterogeneity could be the main forces shaping such structuration. This study provides new insights into the epidemiology and the genetic structure of Z. tritici at small local and, for the first time, at single plant and leaf layer scales. Such findings would be helpful in implementing effective control strategies.

Genotype, development and tissue-derived variation of cell-wall properties in the lignocellulosic energy crop Miscanthus

DOE PAGES

da Costa, Ricardo M. F.; Lee, Scott J.; Allison, Gordon G.; ...

2014-04-15

Species and hybrids of the genus Miscanthus contain attributes that make them front-runners among current selections of dedicated bioenergy crops. A key trait for plant biomass conversion to biofuels and biomaterials is cell-wall quality; however, knowledge of cell-wall composition and biology in Miscanthus species is limited. This study presents data on cell-wall compositional changes as a function of development and tissue type across selected genotypes, and considers implications for the development of miscanthus as a sustainable and renewable bioenergy feedstock. Cell-wall biomass was analysed for 25 genotypes, considering different developmental stages and stem vs. leaf compositional variability, by Fourier transformmore » mid-infrared spectroscopy and lignin determination. In addition, a Clostridium phytofermentans bioassay was used to assess cell-wall digestibility and conversion to ethanol. Important cell-wall compositional differences between miscanthus stem and leaf samples were found to be predominantly associated with structural carbohydrates. Lignin content increased as plants matured and was higher in stem tissues. Although stem lignin concentration correlated inversely with ethanol production, no such correlation was observed for leaves. Leaf tissue contributed significantly to total above-ground biomass at all stages, although the extent of this contribution was genotype-dependent. In conclusion, it is hypothesized that divergent carbohydrate compositions and modifications in stem and leaf tissues are major determinants for observed differences in cell-wall quality. The findings indicate that improvement of lignocellulosic feedstocks should encompass tissue-dependent variation as it affects amenability to biological conversion. For gene-trait associations relating to cell-wall quality, the data support the separate examination of leaf and stem composition, as tissue-specific traits may be masked by considering only total above-ground biomass samples, and sample variability could be mostly due to varying tissue contributions to total biomass.« less

Modelling leaf photosynthetic and transpiration temperature-dependent responses in Vitis vinifera cv. Semillon grapevines growing in hot, irrigated vineyard conditions

PubMed Central

Greer, Dennis H.

2012-01-01

Background and aims Grapevines growing in Australia are often exposed to very high temperatures and the question of how the gas exchange processes adjust to these conditions is not well understood. The aim was to develop a model of photosynthesis and transpiration in relation to temperature to quantify the impact of the growing conditions on vine performance. Methodology Leaf gas exchange was measured along the grapevine shoots in accordance with their growth and development over several growing seasons. Using a general linear statistical modelling approach, photosynthesis and transpiration were modelled against leaf temperature separated into bands and the model parameters and coefficients applied to independent datasets to validate the model. Principal results Photosynthesis, transpiration and stomatal conductance varied along the shoot, with early emerging leaves having the highest rates, but these declined as later emerging leaves increased their gas exchange capacities in accordance with development. The general linear modelling approach applied to these data revealed that photosynthesis at each temperature was additively dependent on stomatal conductance, internal CO2 concentration and photon flux density. The temperature-dependent coefficients for these parameters applied to other datasets gave a predicted rate of photosynthesis that was linearly related to the measured rates, with a 1 : 1 slope. Temperature-dependent transpiration was multiplicatively related to stomatal conductance and the leaf to air vapour pressure deficit and applying the coefficients also showed a highly linear relationship, with a 1 : 1 slope between measured and modelled rates, when applied to independent datasets. Conclusions The models developed for the grapevines were relatively simple but accounted for much of the seasonal variation in photosynthesis and transpiration. The goodness of fit in each case demonstrated that explicitly selecting leaf temperature as a model parameter, rather than including temperature intrinsically as is usually done in more complex models, was warranted. PMID:22567220

Genotype, development and tissue-derived variation of cell-wall properties in the lignocellulosic energy crop Miscanthus.

PubMed

da Costa, Ricardo M F; Lee, Scott J; Allison, Gordon G; Hazen, Samuel P; Winters, Ana; Bosch, Maurice

2014-10-01

Species and hybrids of the genus Miscanthus contain attributes that make them front-runners among current selections of dedicated bioenergy crops. A key trait for plant biomass conversion to biofuels and biomaterials is cell-wall quality; however, knowledge of cell-wall composition and biology in Miscanthus species is limited. This study presents data on cell-wall compositional changes as a function of development and tissue type across selected genotypes, and considers implications for the development of miscanthus as a sustainable and renewable bioenergy feedstock. Cell-wall biomass was analysed for 25 genotypes, considering different developmental stages and stem vs. leaf compositional variability, by Fourier transform mid-infrared spectroscopy and lignin determination. In addition, a Clostridium phytofermentans bioassay was used to assess cell-wall digestibility and conversion to ethanol. Important cell-wall compositional differences between miscanthus stem and leaf samples were found to be predominantly associated with structural carbohydrates. Lignin content increased as plants matured and was higher in stem tissues. Although stem lignin concentration correlated inversely with ethanol production, no such correlation was observed for leaves. Leaf tissue contributed significantly to total above-ground biomass at all stages, although the extent of this contribution was genotype-dependent. It is hypothesized that divergent carbohydrate compositions and modifications in stem and leaf tissues are major determinants for observed differences in cell-wall quality. The findings indicate that improvement of lignocellulosic feedstocks should encompass tissue-dependent variation as it affects amenability to biological conversion. For gene-trait associations relating to cell-wall quality, the data support the separate examination of leaf and stem composition, as tissue-specific traits may be masked by considering only total above-ground biomass samples, and sample variability could be mostly due to varying tissue contributions to total biomass. © The Author 2014. Published by Oxford University Press on behalf of the Annals of Botany Company.

Deep Evolutionary Comparison of Gene Expression Identifies Parallel Recruitment of Trans-Factors in Two Independent Origins of C4 Photosynthesis

PubMed Central

Kümpers, Britta M. C.; Smith-Unna, Richard D.; Hibberd, Julian M.

2014-01-01

With at least 60 independent origins spanning monocotyledons and dicotyledons, the C4 photosynthetic pathway represents one of the most remarkable examples of convergent evolution. The recurrent evolution of this highly complex trait involving alterations to leaf anatomy, cell biology and biochemistry allows an increase in productivity by ∼50% in tropical and subtropical areas. The extent to which separate lineages of C4 plants use the same genetic networks to maintain C4 photosynthesis is unknown. We developed a new informatics framework to enable deep evolutionary comparison of gene expression in species lacking reference genomes. We exploited this to compare gene expression in species representing two independent C4 lineages (Cleome gynandra and Zea mays) whose last common ancestor diverged ∼140 million years ago. We define a cohort of 3,335 genes that represent conserved components of leaf and photosynthetic development in these species. Furthermore, we show that genes encoding proteins of the C4 cycle are recruited into networks defined by photosynthesis-related genes. Despite the wide evolutionary separation and independent origins of the C4 phenotype, we report that these species use homologous transcription factors to both induce C4 photosynthesis and to maintain the cell specific gene expression required for the pathway to operate. We define a core molecular signature associated with leaf and photosynthetic maturation that is likely shared by angiosperm species derived from the last common ancestor of the monocotyledons and dicotyledons. We show that deep evolutionary comparisons of gene expression can reveal novel insight into the molecular convergence of highly complex phenotypes and that parallel evolution of trans-factors underpins the repeated appearance of C4 photosynthesis. Thus, exploitation of extant natural variation associated with complex traits can be used to identify regulators. Moreover, the transcription factors that are shared by independent C4 lineages are key targets for engineering the C4 pathway into C3 crops such as rice. PMID:24901697

Comparison of windthrow damage among thinned and unthinned hardwoods and adjacent pine stands following a late winter tornado on the Cumberland Plateau near Sewanee, TN

Treesearch

Karen Kuers; Samuel C. Grinstead

2006-01-01

In March, 2004, prior to spring leaf-out, an F0 tornado snapped or uprooted 672 trees across 25 ha of the western margin of the Cumberland Plateau near Sewanee, TN. A ridgeline separated the impacted area into two parts: westward-facing slopes of mature hardwoods and eastward-facing slopes with thinned and unthinned hardwoods, pine stands, and clearcuts. Greatest...

A canopy trimming experiment in Puerto Rico: The response of litter decomposition and nutrient release to canopy opening and debris deposition in a subtropical wet forest

Treesearch

G. Gonzalez; D.J. Lodge; B.A. Richardson; M.J. Richardson

2014-01-01

In this study, we used a replicated factorial design to separate the individual and interacting effects of two main components of a severe hurricane – canopy opening and green debris deposition on leaf litter decay in the tabonuco forest in the Luquillo Mountains of Puerto Rico. We quantify changes in percent mass remaining (PMR), the concentration and absolute amounts...

Visualizing heterogeneity of photosynthetic properties of plant leaves with two-photon fluorescence lifetime imaging microscopy.

PubMed

Iermak, Ievgeniia; Vink, Jochem; Bader, Arjen N; Wientjes, Emilie; van Amerongen, Herbert

2016-09-01

Two-photon fluorescence lifetime imaging microscopy (FLIM) was used to analyse the distribution and properties of Photosystem I (PSI) and Photosystem II (PSII) in palisade and spongy chloroplasts of leaves from the C3 plant Arabidopsis thaliana and the C4 plant Miscanthus x giganteus. This was achieved by separating the time-resolved fluorescence of PSI and PSII in the leaf. It is found that the PSII antenna size is larger on the abaxial side of A. thaliana leaves, presumably because chloroplasts in the spongy mesophyll are "shaded" by the palisade cells. The number of chlorophylls in PSI on the adaxial side of the A. thaliana leaf is slightly higher. The C4 plant M. x giganteus contains both mesophyll and bundle sheath cells, which have a different PSI/PSII ratio. It is shown that the time-resolved fluorescence of bundle sheath and mesophyll cells can be analysed separately. The relative number of chlorophylls, which belong to PSI (as compared to PSII) in the bundle sheath cells is at least 2.5 times higher than in mesophyll cells. FLIM is thus demonstrated to be a useful technique to study the PSI/PSII ratio and PSII antenna size in well-defined regions of plant leaves without having to isolate pigment-protein complexes. Copyright © 2016 Elsevier B.V. All rights reserved.

LiMgPO 4:Tb,B - A new sensitive OSL phosphor for dosimetry

NASA Astrophysics Data System (ADS)

Dhabekar, Bhushan; Menon, S. N.; Alagu Raja, E.; Bakshi, A. K.; Singh, A. K.; Chougaonkar, M. P.; Mayya, Y. S.

2011-08-01

Optically Stimulated Luminescence (OSL) technique has emerged as a serious competitor to Thermally Stimulated Luminescence (TSL) technique in various dosimetric applications, especially after the development of crystalline alumina (Al 2O 3:C) doped with carbon. Since then, several attempts are being made to develop other possible materials for OSL based dosimetric applications. Efforts conducted in our laboratory in this direction have led to the development of a new phosphor, Lithium Magnesium Phosphate doped with terbium and boron (LiMgPO 4:Tb,B). This phosphor is prepared by solid-state diffusion method involving conventional air furnaces with operating temperature 1000 °C and easily amenable to large scale production without compromising primary dosimetric advantages. In this work we present some of the dosimetric OSL characteristics of this phosphor. The phosphor exhibits a main TSL peak at 250 °C. The phosphor also emits OSL, when the irradiated phosphor is stimulated with 470 nm light with the OSL sensitivity 1.3 times that of commercially available Al 2O 3:C. Photoluminescence (PL) emission spectrum consists of sharp lines characteristics of Tb 3+ emission. The OSL discs made out of this phosphor are reusable up to at least 50 cycles, the phosphor exhibits dose linearity up to 1 kGy. Minimum detectable dose is found to be 20 μGy and fading of the OSL signal is found to be about 16% in four days, after which the OSL signal stabilizes.

Toxicity and dosimetric analysis of non-small cell lung cancer patients undergoing radiotherapy with 4DCT and image-guided intensity modulated radiotherapy: a regional centre's experience.

PubMed

Livingston, Gareth C; Last, Andrew J; Shakespeare, Thomas P; Dwyer, Patrick M; Westhuyzen, Justin; McKay, Michael J; Connors, Lisa; Leader, Stephanie; Greenham, Stuart

2016-09-01

For patients receiving radiotherapy for locally advance non-small cell lung cancer (NSCLC), the probability of experiencing severe radiation pneumonitis (RP) appears to rise with an increase in radiation received by the lungs. Intensity modulated radiotherapy (IMRT) provides the ability to reduce planned doses to healthy organs at risk (OAR) and can potentially reduce treatment-related side effects. This study reports toxicity outcomes and provides a dosimetric comparison with three-dimensional conformal radiotherapy (3DCRT). Thirty curative NSCLC patients received radiotherapy using four-dimensional computed tomography and five-field IMRT. All were assessed for early and late toxicity using common terminology criteria for adverse events. All plans were subsequently re-planned using 3DCRT to the same standard as the clinical plans. Dosimetric parameters for lungs, oesophagus, heart and conformity were recorded for comparison between the two techniques. IMRT plans achieved improved high-dose conformity and reduced OAR doses including lung volumes irradiated to 5-20 Gy. One case each of oesophagitis and erythema (3%) were the only Grade 3 toxicities. Rates of Grade 2 oesophagitis were 40%. No cases of Grade 3 RP were recorded and Grade 2 RP rates were as low as 3%. IMRT provides a dosimetric benefit when compared to 3DCRT. While the clinical benefit appears to increase with increasing target size and increasing complexity, IMRT appears preferential to 3DCRT in the treatment of NSCLC.

Retrospective evaluation of dosimetric quality for prostate carcinomas treated with 3D conformal, intensity modulated and volumetric modulated arc radiotherapy

PubMed Central

Crowe, Scott B; Kairn, Tanya; Middlebrook, Nigel; Hill, Brendan; Christie, David R H; Knight, Richard T; Kenny, John; Langton, Christian M; Trapp, Jamie V

2013-01-01

Introduction This study examines and compares the dosimetric quality of radiotherapy treatment plans for prostate carcinoma across a cohort of 163 patients treated across five centres: 83 treated with three-dimensional conformal radiotherapy (3DCRT), 33 treated with intensity modulated radiotherapy (IMRT) and 47 treated with volumetric modulated arc therapy (VMAT). Methods Treatment plan quality was evaluated in terms of target dose homogeneity and organs at risk (OAR), through the use of a set of dose metrics. These included the mean, maximum and minimum doses; the homogeneity and conformity indices for the target volumes; and a selection of dose coverage values that were relevant to each OAR. Statistical significance was evaluated using two-tailed Welch's T-tests. The Monte Carlo DICOM ToolKit software was adapted to permit the evaluation of dose metrics from DICOM data exported from a commercial radiotherapy treatment planning system. Results The 3DCRT treatment plans offered greater planning target volume dose homogeneity than the other two treatment modalities. The IMRT and VMAT plans offered greater dose reduction in the OAR: with increased compliance with recommended OAR dose constraints, compared to conventional 3DCRT treatments. When compared to each other, IMRT and VMAT did not provide significantly different treatment plan quality for like-sized tumour volumes. Conclusions This study indicates that IMRT and VMAT have provided similar dosimetric quality, which is superior to the dosimetric quality achieved with 3DCRT. PMID:26229621

Resolving the limitations of using glycine as EPR dosimeter in the intermediate level of gamma dose

NASA Astrophysics Data System (ADS)

Aboelezz, E.; Hassan, G. M.

2018-04-01

The dosimetric properties of the simplest amino acid "glycine"- using EPR technique- were investigated in comparison to reference standard alanine dosimeter. The EPR spectrum of glycine at room temperature is complex, but immediately after irradiation, it appears as a triplet hyperfine structure probably due to the dominant contribution of the (•CH2COO-) radical. The dosimetric peak of glycine is at g-factor 2.0026 ± 0.0015 and its line width is 9 G at large modulation amplitude (7 G). The optimum microwave was studied and was found to be as alanine 8 mW; the post-irradiation as well as the dose rate effects were discussed. Dosimetric peak intensity of glycine fades rapidly to be about one quarter of its original value during 20 days for dried samples and it stabilizes after that. The dose response study in an intermediate range (2-1000 Gy) reveals that the glycine SNR is about 2 times more than that of alanine pellets when measured immediately after irradiation and 4 times more than that of glycine itself after 22 days of irradiation. The effect of energy dependence was studied and interpreted theoretically by calculation of mass energy absorption coefficient. The calculated combined uncertainties for glycine and alanine are nearly the same and were found to be 2.42% and 2.33%, respectively. Glycine shows interesting dosimetric properties in the range of ionizing radiation doses investigated.

Pain and distress induced by elastomeric and spring separators in patients undergoing orthodontic treatment.

PubMed

Al-Balbeesi, Hana O; Bin Huraib, Sahar M; AlNahas, Nadia W; AlKawari, Huda M; Abu-Amara, Abdulrahman B; Vellappally, Sajith; Anil, Sukumaran

2016-01-01

The objective of the present investigation is to evaluate patients' pain perception and discomfort, the duration of pain and the level of self-medication over time during tooth separation, and the effectiveness of elastomeric and spring types of orthodontic separators in Saudi population. The study group consisted of 30 female adolescent patients who had elastomeric/spring separators as part of their orthodontic treatment. A self-administrated questionnaire comprising 16 multiple choice questions and another with visual analog scale were used to record the patient's pain perceptions at 4 hours, 24 hours, 3 days, 5 days, and 7 days from the time of insertion. The level of pain and discomfort during these time periods were assessed by a visual analog scale. After a separation period of 7 days, the amount of separation was measured with a leaf gauge. Type and frequency of analgesic consumption was also recorded. The Statistical Package for the Social Sciences (SPSS) version 20 (IBM SPSS -Chicago, IL: SPSS Inc.,) was used for statistical analysis. The data showed significant increase in the level of pain at 4 hours, 24 hours, and 3 days from separator placement. The elastomeric separators produced significantly more separation than the spring separators and also caused maximum pain during the first 3 days after insertion. However, there was no significant difference between the score of pain between two separators at all time intervals. Both elastomeric and spring separators showed comparative levels of pain and discomfort during the early phase of separation. Elastomeric separators were found to be more effective in tooth separation than spring separators. However, further studies are necessary to substantiate this preliminary observation.

Dosimetric Comparison of Helical Tomotherapy and Dynamic Conformal Arc Therapy in Stereotactic Radiosurgery for Vestibular Schwannomas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Tsair-Fwu, E-mail: tflee@cc.kuas.edu.t; Chang Gung Memorial Hospital-Kaohsiung Medical Center, Chang Gung University College of Medicine, Kaohsiung, Taiwan; Chao, Pei-Ju

2011-04-01

The dosimetric results of stereotactic radiosurgery (SRS) for vestibular schwannoma (VS) performed using dynamic conformal arc therapy (DCAT) with the Novalis system and helical TomoTherapy (HT) were compared using plan quality indices. The HT plans were created for 10 consecutive patients with VS previously treated with SRS using the Novalis system. The dosimetric indices used to compare the techniques included the conformity index (CI) and homogeneity index (HI) for the planned target volume (PTV), the comprehensive quality index (CQI) for nine organs at risk (OARs), gradient score index (GSI) for the dose drop-off outside the PTV, and plan quality indexmore » (PQI), which was verified using the plan quality discerning power (PQDP) to incorporate 3 plan indices, to evaluate the rival plans. The PTV ranged from 0.27-19.99 cm{sup 3} (median 3.39 cm{sup 3}), with minimum required PTV prescribed doses of 10-16 Gy (median 12 Gy). Both systems satisfied the minimum required PTV prescription doses. HT conformed better to the PTV (CI: 1.51 {+-} 0.23 vs. 1.94 {+-} 0.34; p < 0.01), but had a worse drop-off outside the PTV (GSI: 40.3 {+-} 10.9 vs. 64.9 {+-} 13.6; p < 0.01) compared with DCAT. No significant difference in PTV homogeneity was observed (HI: 1.08 {+-} 0.03 vs. 1.09 {+-} 0.02; p = 0.20). HT had a significantly lower maximum dose in 4 OARs and significant lower mean dose in 1 OAR; by contrast, DCAT had a significantly lower maximum dose in 1 OAR and significant lower mean dose in 2 OARs, with the CQI of the 9 OARs = 0.92 {+-} 0.45. Plan analysis using PQI (HT 0.37 {+-} 0.12 vs. DCAT 0.65 {+-} 0.08; p < 0.01), and verified using the PQDP, confirmed the dosimetric advantage of HT. However, the HT system had a longer beam-on time (33.2 {+-} 7.4 vs. 4.6 {+-} 0.9 min; p < 0.01) and consumed more monitor units (16772 {+-} 3803 vs. 1776 {+-} 356.3; p < 0.01). HT had a better dose conformity and similar dose homogeneity but worse dose gradient than DCAT. Plan analysis confirmed the dosimetric advantage of HT, although not all indices revealed a better outcome for HT. Whether this dosimetric advantage translates into a clinical benefit deserves further investigation.« less

SU-E-T-76: A Software System to Monitor VMAT Plan Complexity in a Large Radiotherapy Centre

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arumugam, S; Xing, A; Ingham Institute, Sydney, NSW

2015-06-15

Purpose: To develop a system that analyses and reports the complexity of Volumetric Modulated Arc Therapy (VMAT) plans to aid in the decision making for streamlining patient specific dosimetric quality assurance (QA) tests. Methods: A software system, Delcheck, was developed in-house to calculate VMAT plan and delivery complexity using the treatment delivery file. Delcheck has the functionality to calculate multiple plan complexity metrics including the Li-Xing Modulation Index (LI-MI), multiplicative combination of Leaf Travel and Modulation Complexity Score (LTMCSv), Monitor Units per prescribed dose (MU/D) and the delivery complexity index (MIt) that incorporates the modulation of dose rate, leaf speedmore » and gantry speed. Delcheck includes database functionality to store and compare plan metrics for a specified treatment site. The overall plan and delivery complexity is assessed based on the 95% conformance limit of the complexity metrics as Similar, More or Less complex. The functionality of the software was tested using 42 prostate conventional, 10 prostate SBRT and 15 prostate bed VMAT plans generated for an Elekta linear accelerator. Results: The mean(σ) of LI-MI for conventional, SBRT and prostate bed plans were 1690(486), 3215.4(1294) and 3258(982) respectively. The LTMCSv of the studied categories were 0.334(0.05), 0.325(0.07) and 0.3112(0.09). The MU/D of the studied categories were 2.4(0.4), 2.7(0.7) and 2.5(0.5). The MIt of the studied categories were 21.6(3.4), 18.2(3.0) and 35.9(6.6). The values of the complexity metrics show that LI-MI appeared to resolve the plan complexity better than LTMCSv and MU/D. The MIt value increased as the delivery complexity increased. Conclusion: The developed software was shown to be working as expected. In studied treatment categories Prostate bed plans are more complex in both plan and delivery and SBRT is more complex in plan and less complex in delivery as demonstrated by LI-MI and MIt. This project was funded through a Cancer Council NSW Project Grant (RG14-11)« less

WE-DE-BRA-10: Development of a Novel Scanning Beam Low-Energy Intraoperative Radiation Therapy (SBIORT) System for Pancreatic Cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wears, B; Mohiuddin, I; Flynn, R

2016-06-15

Purpose: Developing a compact collimator system and validating a 3D surface imaging module for a scanning beam low-energy x-ray radiation therapy (SBIORT) system that enables delivery of non-uniform radiation dose to targets with irregular shapes intraoperatively. Methods: SBIORT consists of a low energy x-ray source, a custom compact collimator module, a robotic arm, and a 3D surface imaging module. The 3D surface imaging system (structure sensor) is utilized for treatment planning and motion monitoring of the surgical cavity. SBIORT can deliver non-uniform dose distributions by dynamically moving the x-ray source assembly along optimal paths with various collimator apertures. The compactmore » collimator utilizes a dynamic shutter mechanism to form a variable square aperture. The accuracy and reproducibility of the collimator were evaluated using a high accuracy encoder and a high resolution camera platform. The dosimetrical characteristics of the collimator prototype were evaluated using EBT3 films with a Pantak Therapax unit. The accuracy and clinical feasibility of the 3D imaging system were evaluated using a phantom and a cadaver cavity. Results: The SBIORT collimator has a compact size: 66 mm diameter and 10 mm thickness with the maximum aperture of 20 mm. The mechanical experiment indicated the average accuracy of leaf position was 0.08 mm with a reproducibility of 0.25 mm at 95% confidence level. The dosimetry study indicated the collimator had a penumbra of 0.35 mm with a leaf transmission of 0.5%. 3D surface scans can be acquired in 5 seconds. The average difference between the acquired 3D surface and the ground truth is 1 mm with a standard deviation of 0.6 mm. Conclusion: This work demonstrates the feasibility of the compact collimator and 3D scanning system for the SBIORT. SBIORT is a way of delivering IORT with a compact system that requires minimum shielding of the procedure room. This research is supported by the University of Iowa Internal Funding Initiatives.« less

Assessing plant water relations based on hidden in formation in the hyper-spectral signatures: Parameterization of olive leaf P-V curve and estimation of water potential components

NASA Astrophysics Data System (ADS)

Rallo, Giovanni; Provenzano, Giuseppe; Jones, Hamlyn G.

2015-04-01

The Soil Plant Atmosphere Continuum (SPAC) is characterized by complex structures and biophysical processes acting over a wide range of temporal and spatial scales. Additionally, in olive grove systems, the plant adaptive strategies to respond to soil water-limited conditions make the system even more complex. One of the greatest challenges in hydrological research is to quantify changing plant water relations. A promising new technology is provided by the advent of new field spectroscopy detectors, characterized by very high resolution over the spectral range between 300 and 2500 nm, allowing the detection of narrow reflectance or absorptance peaks, to separate close lying peaks and to discover new information, hidden at lower resolutions. The general objective of the present research was to investigate a range of plant state function parameters in a non-destructive and repeatable manner and to improve methodologies aimed to parameterize hydrological models describing the entire SPAC, or each single compartment (soil or plant). We have investigated the use of hyperspectral sensing for the parameterization of the hydraulic pressure-volume curve (P-V) for olive leaf and for the indirect estimation of the two principal leaf water potential components, i.e. turgor and osmotic potentials. Experiments were carried out on an olive grove in Sicily, during the mature phase of the first vegetative flush. Leaf spectral signatures and associated P-V measurements were acquired on olive leaves collected from well-irrigated plants and from plants maintained under moderate or severe water stress. Leaf spectral reflectance was monitored with a FieldSpec 4 spectro-radiometer (Analytical Spectral Device, Inc.), in a range of wavelengths from VIS to SWIR (350-2500 nm), with sampling intervals of 1.4 nm and 2.0 nm, respectively in the regions from 350 to 1000 nm and from 1000 to 2500 nm. Measurements required the use of contact probe and leaf clip (Analytical Spectral Device, Inc.), specifically designed for plant leaves. Immediately after each spectral acquisition, water potential was measured on the same leaf with a Scholander pressure chamber (Skye, Powys, UK), by following the standard procedure usually adopted to detect leaf P-V curves (Vilagrosa et al. 2003). The relationship between pressure and volume was represented by means of the Höfler diagram (Richter, 1978) and modeled following an analytical approach. In order to parameterize the the P-V curve and to estimate the leaf water potential components, spectral indices were then examined, considering the features of water absorption in SWIR domain, sensitive to changes in leaf water content, and in NIR domain of the spectrum, sensitive to changes in leaf internal structure. A number of spectral indices were found to be related to patterns in the Höfler diagram, for leaves collected under different intensities of crop water stress. Moreover, results show that a fundamental characteristic point of the Höfler diagram, the turgor loss point, can be identified when indices accounting for both SWIR and NIR domains are considered. Acknowledgements The research was carried out thanks to the Alexander Goetz support program 2014, which provided the tools for spectral measurements and technical assistance during experiments.

The internal dosimetry code PLEIADES.

PubMed

Fell, T P; Phipps, A W; Smith, T J

2007-01-01

The International Commission on Radiological Protection (ICRP) has published dose coefficients for the ingestion or inhalation of radionuclides in a series of reports covering intakes by workers and members of the public, including children and pregnant or lactating women. The calculation of these coefficients divides naturally into two distinct parts-the biokinetic and dosimetric. This paper describes in detail the methods used to solve the biokinetic problem in the generation of dose coefficients on behalf of the ICRP, as implemented in the Health Protection Agency's internal dosimetry code PLEIADES. A summary of the dosimetric treatment is included.