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Sample records for dosimetric mapping dosmap

  1. Space radiation measurements on-board ISS--the DOSMAP experiment.

    PubMed

    Reitz, G; Beaujean, R; Benton, E; Burmeister, S; Dachev, Ts; Deme, S; Luszik-Bhadra, M; Olko, P

    2005-01-01

    The experiment 'Dosimetric Mapping' conducted as part of the science program of NASA's Human Research Facility (HRF) between March and August 2001 was designed to measure integrated total absorbed doses (ionising radiation and neutrons), heavy ion fluxes and its energy, mass and linear energy transfer (LET) spectra, time-dependent count rates of charged particles and their corresponding dose rates at different locations inside the US Lab at the International Space Station. Owing to the variety of particles and energies, a dosimetry package consisting of thermoluminescence dosemeter (TLD) chips and nuclear track detectors with and without converters (NTDPs), a silicon dosimetry telescope (DOSTEL), four mobile silicon detector units (MDUs) and a TLD reader unit (PILLE) with 12 TLD bulbs as dosemeters was used. Dose rates of the ionising part of the radiation field measured with TLD bulbs applying the PILLE readout system at different locations varied between 153 and 231 microGy d(-1). The dose rate received by the active devices fits excellent to the TLD measurements and is significantly lower compared with measurements for the Shuttle (STS) to MIR missions. The comparison of the absorbed doses from passive and active devices showed an agreement within +/- 10%. The DOSTEL measurements in the HRF location yielded a mean dose equivalent rate of 535 microSv d(-1). DOSTEL measurements were also obtained during the Solar Particle Event on 15 April 2001. PMID:16604663

  2. High spatial resolution dosimetric response maps for radiotherapy ionization chambers measured using kilovoltage synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Butler, D. J.; Stevenson, A. W.; Wright, T. E.; Harty, P. D.; Lehmann, J.; Livingstone, J.; Crosbie, J. C.

    2015-11-01

    Small circular beams of synchrotron radiation (0.1 mm and 0.4 mm in diameter) were used to irradiate ionization chambers of the types commonly used in radiotherapy. By scanning the chamber through the beam and measuring the ionization current, a spatial map of the dosimetric response of the chamber was recorded. The technique is able to distinguish contributions to the large-field ionization current from the chamber walls, central electrode and chamber stem. Scans were recorded for the NE 2571 Farmer chamber, the PTW 30013, IBA FC65-G Farmer-type chambers, the NE 2611A and IBA CC13 thimble chambers, the PTW 31006 and 31014 pinpoint chambers, the PTW Roos and Advanced Markus plane-parallel chambers, and the PTW 23342 thin-window soft x-ray chamber. In all cases, large contributions to the response arise from areas where the incident beam grazes the cavity surfaces. Quantitative as well as qualitative information about the relative chamber response was extracted from the maps, including the relative contribution of the central electrode. Line scans using monochromatic beams show the effect of the photon energy on the chamber response. For Farmer-type chambers, a simple Monte Carlo model was in good agreement with the measured response.

  3. Direct dose mapping versus energy/mass transfer mapping for 4D dose accumulation: fundamental differences and dosimetric consequences

    NASA Astrophysics Data System (ADS)

    Li, Haisen S.; Zhong, Hualiang; Kim, Jinkoo; Glide-Hurst, Carri; Gulam, Misbah; Nurushev, Teamour S.; Chetty, Indrin J.

    2014-01-01

    The direct dose mapping (DDM) and energy/mass transfer (EMT) mapping are two essential algorithms for accumulating the dose from different anatomic phases to the reference phase when there is organ motion or tumor/tissue deformation during the delivery of radiation therapy. DDM is based on interpolation of the dose values from one dose grid to another and thus lacks rigor in defining the dose when there are multiple dose values mapped to one dose voxel in the reference phase due to tissue/tumor deformation. On the other hand, EMT counts the total energy and mass transferred to each voxel in the reference phase and calculates the dose by dividing the energy by mass. Therefore it is based on fundamentally sound physics principles. In this study, we implemented the two algorithms and integrated them within the Eclipse treatment planning system. We then compared the clinical dosimetric difference between the two algorithms for ten lung cancer patients receiving stereotactic radiosurgery treatment, by accumulating the delivered dose to the end-of-exhale (EE) phase. Specifically, the respiratory period was divided into ten phases and the dose to each phase was calculated and mapped to the EE phase and then accumulated. The displacement vector field generated by Demons-based registration of the source and reference images was used to transfer the dose and energy. The DDM and EMT algorithms produced noticeably different cumulative dose in the regions with sharp mass density variations and/or high dose gradients. For the planning target volume (PTV) and internal target volume (ITV) minimum dose, the difference was up to 11% and 4% respectively. This suggests that DDM might not be adequate for obtaining an accurate dose distribution of the cumulative plan, instead, EMT should be considered.

  4. Dosimetric evaluation of MapCHECK 2 and 3DVH in the IMRT delivery quality assurance process

    SciTech Connect

    Song, Ju-Young; Kim, Yong-Hyeob; Jeong, Jae-Uk; Yoon, Mee Sun; Ahn, Sung-Ja; Chung, Woong-Ki; Nam, Taek-Keun

    2014-07-01

    Based on per-field data, 3 dose-volume histogram (DVH) is designed to calculate 3-dimensional (3D) dose using patient-computed tomography (CT) for an intensity-modulated radiation therapy (IMRT) delivery quality assurance (DQA) process measured with diode detector arrays. In this study, the characteristics and suitability of 3DVH for an IMRT DQA process were evaluated by assessment of clinically applied results. The DQA plans were prepared with a 2D diode detector array (MapCHECK 2) for 20 IMRT patients (10 with head and neck cancer and 10 with prostate cancer), and the matching rate between the calculated dose and the measured dose was analyzed. The relative dose differences between the original IMRT plan and the recalculated plan by 3DVH were evaluated for tumor target and organs at risk (OARs). Confidence limits (CLs) were determined for quantification of the degree of agreement that should be expected in each DQA method. The individual CLs for DQA accuracy of 3D dosimetric evaluation in the tumor target and OARs were also calculated to evaluate the differences compared with conventional 2D-based DQA results. The matching rates were sufficient to validate the accuracy of IMRT DQA analyses and the calculated CL values were reasonable values considering the normal criteria of our institution. The 3DVH analysis generally had better matching rate than per-field measurement analysis and the CL values for OARs were better than those for the planning target volume (PTV). The usefulness of the 3DVH tool was verified for IMRT DQA from the point of view of dose evaluation in the corresponding patient's CT data. It also enables dosimetric evaluation in each important structure (PTV and OARs), which can promote more effective evaluation of DQA error in terms of tumor treatment and side effects.

  5. SU-E-J-151: Dosimetric Evaluation of DIR Mapped Contours for Image Guided Adaptive Radiotherapy with 4D Cone-Beam CT

    SciTech Connect

    Balik, S; Weiss, E; Williamson, J; Hugo, G; Jan, N; Zhang, L; Roman, N; Christensen, G

    2014-06-01

    Purpose: To estimate dosimetric errors resulting from using contours deformably mapped from planning CT to 4D cone beam CT (CBCT) images for image-guided adaptive radiotherapy of locally advanced non-small cell lung cancer (NSCLC). Methods: Ten locally advanced non-small cell lung cancer (NSCLC) patients underwent one planning 4D fan-beam CT (4DFBCT) and weekly 4DCBCT scans. Multiple physicians delineated the gross tumor volume (GTV) and normal structures in planning CT images and only GTV in CBCT images. Manual contours were mapped from planning CT to CBCTs using small deformation, inverse consistent linear elastic (SICLE) algorithm for two scans in each patient. Two physicians reviewed and rated the DIR-mapped (auto) and manual GTV contours as clinically acceptable (CA), clinically acceptable after minor modification (CAMM) and unacceptable (CU). Mapped normal structures were visually inspected and corrected if necessary, and used to override tissue density for dose calculation. CTV (6mm expansion of GTV) and PTV (5mm expansion of CTV) were created. VMAT plans were generated using the DIR-mapped contours to deliver 66 Gy in 33 fractions with 95% and 100% coverage (V66) to PTV and CTV, respectively. Plan evaluation for V66 was based on manual PTV and CTV contours. Results: Mean PTV V66 was 84% (range 75% – 95%) and mean CTV V66 was 97% (range 93% – 100%) for CAMM scored plans (12 plans); and was 90% (range 80% – 95%) and 99% (range 95% – 100%) for CA scored plans (7 plans). The difference in V66 between CAMM and CA was significant for PTV (p = 0.03) and approached significance for CTV (p = 0.07). Conclusion: The quality of DIR-mapped contours directly impacted the plan quality for 4DCBCT-based adaptation. Larger safety margins may be needed when planning with auto contours for IGART with 4DCBCT images. Reseach was supported by NIH P01CA116602.

  6. 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

  7. Dosimetric adaptive IMRT driven by fiducial points

    SciTech Connect

    Crijns, Wouter; Van Herck, Hans; Defraene, Gilles; Van den Bergh, Laura; Haustermans, Karin; Slagmolen, Pieter; Maes, Frederik; Van den Heuvel, Frank

    2014-06-15

    Purpose: Intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy have become standard treatments but are more sensitive to anatomical variations than 3D conformal techniques. To correct for inter- and intrafraction anatomical variations, fast and easy to implement methods are needed. Here, the authors propose a full dosimetric IMRT correction that finds a compromise in-between basic repositioning (the current clinical practice) and full replanning. It simplifies replanning by avoiding a recontouring step and a full dose calculation. It surpasses repositioning by updating the preoptimized fluence and monitor units (MU) using a limited number of fiducial points and a pretreatment (CB)CT. To adapt the fluence the fiducial points were projected in the beam's eye view (BEV). To adapt the MUs, point dose calculation towards the same fiducial points were performed. The proposed method is intrinsically fast and robust, and simple to understand for operators, because of the use of only four fiducial points and the beam data based point dose calculations. Methods: To perform our dosimetric adaptation, two fluence corrections in the BEV are combined with two MU correction steps along the beam's path. (1) A transformation of the fluence map such that it is realigned with the current target geometry. (2) A correction for an unintended scaling of the penumbra margin when the treatment beams scale to the current target size. (3) A correction for the target depth relative to the body contour and (4) a correction for the target distance to the source. The impact of the correction strategy and its individual components was evaluated by simulations on a virtual prostate phantom. This heterogeneous reference phantom was systematically subjected to population based prostate transformations to simulate interfraction variations. Additionally, a patient example illustrated the clinical practice. The correction strategy was evaluated using both dosimetric (CTV mean

  8. Mapping

    ERIC Educational Resources Information Center

    Kinney, Douglas M.; McIntosh, Willard L.

    1978-01-01

    Geologic mapping in the United States increased by about one-quarter in the past year. Examinations of mapping trends were in the following categories: (1) Mapping at scales of 1:100, 000; (2) Metric-scale base maps; (3) International mapping, and (4) Planetary mapping. (MA)

  9. Developing and improving a scanning system for dosimetric applications

    SciTech Connect

    Perez, P.; Galvan, V.; Castellanoa, G.; Valente, M.

    2010-08-04

    Radiotherapy is nowadays one of the most used techniques for the treatment of different pathologies, particularly cancer diseases. The accuracy regarding the application of these treatments, which are planned according to patient information, depends mainly on the dosimetric measurements of absorbed dose within irradiated tissues. The present work is devoted to the study, design and construction of an original device capable of performing visible light transmission measurements in order to analyze Fricke gel dosimeters. Furthermore, a suitable bi-dimensional positioning system along with a dedicated control system and image processing software has been adapted to the dosimetric device in order to perform 2D dose mapping. The obtained results confirm the feasibility of the proposed method, therefore suggesting its potentiality for clinical applications.

  10. Dosimetric Characteristics for Brachytherapy Sources

    SciTech Connect

    DeWerd, Larry A.; Davis, Stephen D.

    2011-05-05

    Brachytherapy sources are characterized by the dosimetric parameters in a protocol such as the American Association of Physicists in Medicine Task Group 43. The air-kerma strength is measured and traceable to a primary standard. Then the parameters such as dose-rate constant, radial dose function, and anisotropy function are measured and related back to the primary standard. This is normally accomplished with thermoluminescent dosimeters (TLDs). Since radial dose function and anisotropy function are relative parameters, some of the dosimetric corrections are negligible. For the dose-rate constant, parameters such as the energy dependence compared with a calibration beam such as {sup 60}Co need to be accounted for. A description of the primary standard measurements and TLD measurements will be discussed.

  11. Mapping.

    ERIC Educational Resources Information Center

    Kinney, Douglas M.; McIntosh, Willard L.

    1979-01-01

    The area of geological mapping in the United States in 1978 increased greatly over that reported in 1977; state geological maps were added for California, Idaho, Nevada, and Alaska last year. (Author/BB)

  12. Dosimetric methodology of the ICRP

    SciTech Connect

    Eckerman, K.F.

    1994-12-31

    Establishment of guidance for the protection of workers and members of the public from radiation exposures necessitates estimation of the radiation dose to tissues of the body at risk. The dosimetric methodology formulated by the International Commission on Radiological Protection (ICRP) is intended to be responsive to this need. While developed for radiation protection, elements of the methodology are often applied in addressing other radiation issues; e.g., risk assessment. This chapter provides an overview of the methodology, discusses its recent extension to age-dependent considerations, and illustrates specific aspects of the methodology through a number of numerical examples.

  13. Determination of dosimetric properties of MgO doped natural amethyst samples.

    PubMed

    Nur, N; Guckan, V; Kizilkaya, N; Depci, T; Ahmedova, C; Yucel, A; Ozdemir, A; Altunal, V; Koc, V; Yegingil, Z

    2016-10-01

    In this paper, the thermoluminescence (TL) dosimetric characteristics of MgO doped natural amethyst samples (Mg-NA) are presented. The morphologies and chemical structures of the powder form samples were identified using XRD, FTIR, SEM, SEM mapping and EDX. Comparison of the TL intensities showed that 10wt% Mg-NA was nearly 150 times more sensitive than undoped amethyst and the main dosimetric properties proved that 10wt% Mg-NA may be a promising phosphor for clinical and radiotherapy purposes. PMID:27526353

  14. Dosimetric Predictors of Laryngeal Edema

    SciTech Connect

    Sanguineti, Giuseppe . E-mail: gisangui@utmb.edu; Adapala, Prashanth; Endres, Eugene J. C; Brack, Collin; Fiorino, Claudio; Sormani, Maria Pia; Parker, Brent

    2007-07-01

    Purpose: To investigate dosimetric predictors of laryngeal edema after radiotherapy (RT). Methods and Materials: A total of 66 patients were selected who had squamous cell carcinoma of the head and neck with grossly uninvolved larynx at the time of RT, no prior major surgical operation except for neck dissection and tonsillectomy, treatment planning data available for analysis, and at least one fiberoptic examination of the larynx within 2 years from RT performed by a single observer. Both the biologically equivalent mean dose at 2 Gy per fraction and the cumulative biologic dose-volume histogram of the larynx were extracted for each patient. Laryngeal edema was prospectively scored after treatment. Time to endpoint, moderate or worse laryngeal edema (Radiation Therapy Oncology Group Grade 2+), was calculated with log rank test from the date of treatment end. Results: At a median follow-up of 17.1 months (range, 0.4- 50.0 months), the risk of Grade 2+ edema was 58.9% {+-} 7%. Mean dose to the larynx, V30, V40, V50, V60, and V70 were significantly correlated with Grade 2+ edema at univariate analysis. At multivariate analysis, mean laryngeal dose (continuum, hazard ratio, 1.11; 95% confidence interval, 1.06-1.15; p < 0.001), and positive neck stage at RT (N0-x vs. N +, hazard ratio, 3.66; 95% confidence interval, 1.40-9.58; p = 0.008) were the only independent predictors. Further stratification showed that, to minimize the risk of Grade 2+ edema, the mean dose to the larynx has to be kept {<=}43.5 Gy at 2 Gy per fraction. Conclusion: Laryngeal edema is strictly correlated with various dosimetric parameters; mean dose to the larynx should be kept {<=}43.5 Gy.

  15. Practical simplifications for radioimmunotherapy dosimetric models

    SciTech Connect

    Shen, S.; DeNardo, G.L.; O`Donnell, R.T.; Yuan, A.; DeNardo, D.A.; Macey, D.J.; DeNardo, S.J.

    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 methods 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.

  16. Dosimetric Characteristics of a Two-Dimensional Diode Array Detector Irradiated with Passively Scattered Proton Beams

    PubMed Central

    Liengsawangwong, Praimakorn; Sahoo, Nanayan; Ding, Xiaoning; Lii, MingFwu; Gillin, Michale T.; Zhu, Xiaorong Ronald

    2015-01-01

    Purpose: To evaluate the dosimetric characteristics of a two-dimensional (2D) diode array detector irradiated with passively scattered proton beams. Materials and Methods: A diode array detector, MapCHECK (Model 1175, Sun Nuclear, Melbourne, FL, USA) was characterized in passive-scattered proton beams. The relative sensitivity of the diodes and absolute dose calibration were determined using a 250 MeV beam. The pristine Bragg curves (PBCs) measured by MapCHECK diodes were compared with those of an ion chamber using a range shift method. The water-equivalent thickness (WET) of the diode array detector’s intrinsic buildup also was determined. The inverse square dependence, linearity, and other proton dosimetric quantities measured by MapCHECK were also compared with those of the ion chambers. The change in the absolute dose response of the MapCHECK as a function of accumulated radiation dose was used as an indicator of radiation damage to the diodes. 2D dose distribution with and without the compensator were measured and compared with the treatment planning system (TPS) calculations. Results: The WET of the MapCHECK diode’s buildup was determined to be 1.7 cm. The MapCHECK-measured PBC were virtually identical to those measured by a parallel-plate ion chamber for 160, 180, and 250 MeV proton beams. The inverse square results of the MapCHECK were within ±0.4% of the ion chamber results. The linearity of MapCHECK results was within 1% of those from the ion chamber as measured in the range between 10 and 300 MU. All other dosimetric quantities were within 1.3% of the ion chamber results. The 2D dose distributions for non-clinical fields without compensator and the patient treatment fields with the compensator were consistent with the TPS results. The absolute dose response of the MapCHECK was changed by 7.4% after an accumulated dose increased by 170 Gy. Conclusions: The MapCHECK is a convenient and useful tool for 2D dose distribution measurements using passively

  17. Dosimetric investigations on Mars-96 mission.

    PubMed

    Semkova, J; Dachev, T s; Matviichuk, Y u; Koleva, R; Tomov, B; Baynov, P; Petrov, V; Nguyen, V; Siegrist, M; Chene, J; d'Uston, C; Cotin, F

    1994-10-01

    The dosimetric experiments Dose-M and Liulin as part of the more complex French-German-Bulgarian-Russian experiments for the investigation of the radiation environment for Mars-96 mission are described. The experiments will be realized with dosemeter-radiometer instruments, measuring absorbed dose in semiconductor detectors and the particle flux. Two detectors will be mounted on board the Mars-96 orbiter. Another detector will be on the guiderope of the Mars-96 Aerostate station. The scientific aims of Dose-M and Liulin experiments are: Analysis of the absorbed dose and the flux on the path and around Mars behind different shielding. Study of the shielding characteristics of the Martian atmosphere from galactic and solar cosmic rays including solar proton events. Together with the French gamma-spectrometer and the German neutron detectors the investigation of the radiation environment on the surface of Mars and in the atmosphere up to 4000 m altitude will be conducted.

  18. Thermoluminescence dosimetric characteristics of beta irradiated salt.

    PubMed

    Murthy, K V R; Pallavi, S P; Rahul, G; Patel, Y S; Sai Prasad, A S; Elangovan, D

    2006-01-01

    The thermoluminescence (TL) characteristics of sodium chloride (NaCl), known as common salt, used for cooking purposes (iodised salt), have been studied in the present paper considering its usage as an 'accidental dosemeter' in the case of a nuclear fallout. TL characteristics of common salt have been examined under excitation with a beta dose of 20 Gy from a 90Sr beta source. The salt specimens are used in the form of discs. The average salt grain that sticks to the disc is measured to be approximately 1 mg. The TL of the beta irradiated salt is recorded in the conventional TL apparatus. Initially three peaks were observed at 133, 205 and 238 degrees C. All three peaks are well resolved, having maximum intensity at 238 degrees C. The material under investigation, i.e. 'common salt' possesses many good dosimetric properties and therefore this can be considered as an 'accidental dosemeter'.

  19. Dosimetric measurements of an n-butyl cyanoacrylate embolization material for arteriovenous malformations

    SciTech Connect

    Labby, Zacariah E.; Chaudhary, Neeraj; Gemmete, Joseph J.; Pandey, Aditya S.; Roberts, Donald A.

    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 derived 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

  20. Statistical process control for IMRT dosimetric verification.

    PubMed

    Breen, Stephen L; Moseley, Douglas J; Zhang, Beibei; Sharpe, Michael B

    2008-10-01

    Patient-specific measurements are typically used to validate the dosimetry of intensity-modulated radiotherapy (IMRT). To evaluate the dosimetric performance over time of our IMRT process, we have used statistical process control (SPC) concepts to analyze the measurements from 330 head and neck (H&N) treatment plans. The objectives of the present work are to: (i) Review the dosimetric measurements of a large series of consecutive head and neck treatment plans to better understand appropriate dosimetric tolerances; (ii) analyze the results with SPC to develop action levels for measured discrepancies; (iii) develop estimates for the number of measurements that are required to describe IMRT dosimetry in the clinical setting; and (iv) evaluate with SPC a new beam model in our planning system. H&N IMRT cases were planned with the PINNACLE treatment planning system versions 6.2b or 7.6c (Philips Medical Systems, Madison, WI) and treated on Varian (Palo Alto, CA) or Elekta (Crawley, UK) linacs. As part of regular quality assurance, plans were recalculated on a 20-cm-diam cylindrical phantom, and ion chamber measurements were made in high-dose volumes (the PTV with highest dose) and in low-dose volumes (spinal cord organ-at-risk, OR). Differences between the planned and measured doses were recorded as a percentage of the planned dose. Differences were stable over time. Measurements with PINNACLE3 6.2b and Varian linacs showed a mean difference of 0.6% for PTVs (n=149, range, -4.3% to 6.6%), while OR measurements showed a larger systematic discrepancy (mean 4.5%, range -4.5% to 16.3%) that was due to well-known limitations of the MLC model in the earlier version of the planning system. Measurements with PINNACLE3 7.6c and Varian linacs demonstrated a mean difference of 0.2% for PTVs (n=160, range, -3.0%, to 5.0%) and -1.0% for ORs (range -5.8% to 4.4%). The capability index (ratio of specification range to range of the data) was 1.3 for the PTV data, indicating that almost

  1. Statistical process control for IMRT dosimetric verification

    SciTech Connect

    Breen, Stephen L.; Moseley, Douglas J.; Zhang, Beibei; Sharpe, Michael B.

    2008-10-15

    Patient-specific measurements are typically used to validate the dosimetry of intensity-modulated radiotherapy (IMRT). To evaluate the dosimetric performance over time of our IMRT process, we have used statistical process control (SPC) concepts to analyze the measurements from 330 head and neck (H and N) treatment plans. The objectives of the present work are to: (i) Review the dosimetric measurements of a large series of consecutive head and neck treatment plans to better understand appropriate dosimetric tolerances; (ii) analyze the results with SPC to develop action levels for measured discrepancies; (iii) develop estimates for the number of measurements that are required to describe IMRT dosimetry in the clinical setting; and (iv) evaluate with SPC a new beam model in our planning system. H and N IMRT cases were planned with the PINNACLE{sup 3} treatment planning system versions 6.2b or 7.6c (Philips Medical Systems, Madison, WI) and treated on Varian (Palo Alto, CA) or Elekta (Crawley, UK) linacs. As part of regular quality assurance, plans were recalculated on a 20-cm-diam cylindrical phantom, and ion chamber measurements were made in high-dose volumes (the PTV with highest dose) and in low-dose volumes (spinal cord organ-at-risk, OR). Differences between the planned and measured doses were recorded as a percentage of the planned dose. Differences were stable over time. Measurements with PINNACLE{sup 3} 6.2b and Varian linacs showed a mean difference of 0.6% for PTVs (n=149, range, -4.3% to 6.6%), while OR measurements showed a larger systematic discrepancy (mean 4.5%, range -4.5% to 16.3%) that was due to well-known limitations of the MLC model in the earlier version of the planning system. Measurements with PINNACLE{sup 3} 7.6c and Varian linacs demonstrated a mean difference of 0.2% for PTVs (n=160, range, -3.0%, to 5.0%) and -1.0% for ORs (range -5.8% to 4.4%). The capability index (ratio of specification range to range of the data) was 1.3 for the PTV

  2. Statistical process control for IMRT dosimetric verification.

    PubMed

    Breen, Stephen L; Moseley, Douglas J; Zhang, Beibei; Sharpe, Michael B

    2008-10-01

    Patient-specific measurements are typically used to validate the dosimetry of intensity-modulated radiotherapy (IMRT). To evaluate the dosimetric performance over time of our IMRT process, we have used statistical process control (SPC) concepts to analyze the measurements from 330 head and neck (H&N) treatment plans. The objectives of the present work are to: (i) Review the dosimetric measurements of a large series of consecutive head and neck treatment plans to better understand appropriate dosimetric tolerances; (ii) analyze the results with SPC to develop action levels for measured discrepancies; (iii) develop estimates for the number of measurements that are required to describe IMRT dosimetry in the clinical setting; and (iv) evaluate with SPC a new beam model in our planning system. H&N IMRT cases were planned with the PINNACLE treatment planning system versions 6.2b or 7.6c (Philips Medical Systems, Madison, WI) and treated on Varian (Palo Alto, CA) or Elekta (Crawley, UK) linacs. As part of regular quality assurance, plans were recalculated on a 20-cm-diam cylindrical phantom, and ion chamber measurements were made in high-dose volumes (the PTV with highest dose) and in low-dose volumes (spinal cord organ-at-risk, OR). Differences between the planned and measured doses were recorded as a percentage of the planned dose. Differences were stable over time. Measurements with PINNACLE3 6.2b and Varian linacs showed a mean difference of 0.6% for PTVs (n=149, range, -4.3% to 6.6%), while OR measurements showed a larger systematic discrepancy (mean 4.5%, range -4.5% to 16.3%) that was due to well-known limitations of the MLC model in the earlier version of the planning system. Measurements with PINNACLE3 7.6c and Varian linacs demonstrated a mean difference of 0.2% for PTVs (n=160, range, -3.0%, to 5.0%) and -1.0% for ORs (range -5.8% to 4.4%). The capability index (ratio of specification range to range of the data) was 1.3 for the PTV data, indicating that almost

  3. Gamma Putty dosimetric studies in electron beam.

    PubMed

    Gloi, Aime M

    2016-01-01

    Traditionally, lead has been used for field shaping in megavoltage electron beams in radiation therapy. In this study, we analyze the dosimetric parameters of a nontoxic, high atomic number (Z = 83), bismuth-loaded material called Gamma Putty that is malleable and can be easily molded to any desired shape. First, we placed an ionization chamber at different depths in a solid water phantom under a Gamma Putty shield of thickness (t = 0, 3, 5, 10, 15, 20, and 25 mm, respectively) and measured the ionizing radiation on the central axis (CAX) for electron beam ranging in energies from 6 to 20 MeV. Next, we investigated the relationship between the relative ionization (RI) measured at a fixed depth for several Gamma Putty shield at different cutout diameters ranging from 2 to 5 cm for various beam energies and derived an exponential fitting equation for clinical purposes. The dose profiles along the CAX show that bremsstrahlung dominates for Gamma Putty thickness >15 mm. For high-energy beams (12-20 MeV) and all Gamma Putty thicknesses up to 25 mm, RI below 5% could not be achieved due to the strong bremsstrahlung component. However, Gamma Putty is a very suitable material for reducing the transmission factor below 5% and protecting underlying normal tissues for low-energy electron beams (6-9 MeV). PMID:27651563

  4. A high sensitive phosphor for dosimetric applications

    SciTech Connect

    Kore, Bhushan P. Dhoble, S. J.; Dhoble, N. S.; Lochab, S. P.

    2015-06-24

    In this study a novel TL phosphor CaMg{sub 3}(SO{sub 4}){sub 4}:Dy{sup 3+} was prepared by acid distillation method. The TL response of this phosphor towards γ-rays and carbon ion beam was tested. Good dosimetric glow curve was observed which is stable against both the type of radiations. The CaMg{sub 3}(SO{sub 4}){sub 4}:Dy{sup 3+} phosphor doped with 0.2 mol% of Dy{sup 3+}, irradiated with γ-ray shows nearly equal sensitivity to that of commercially available CaSO{sub 4}:Dy TLD phosphor whereas 3.5 times more sensitivity than CaSO{sub 4}:Dy, when irradiated with carbon ion beam. The change in glow peak intensities and glow peak temperature with variation in irradiation species and energy of ion beam is discussed here. The effect of these on trapping parameters is also illustrated.

  5. Gamma Putty dosimetric studies in electron beam

    PubMed Central

    Gloi, Aime M.

    2016-01-01

    Traditionally, lead has been used for field shaping in megavoltage electron beams in radiation therapy. In this study, we analyze the dosimetric parameters of a nontoxic, high atomic number (Z = 83), bismuth-loaded material called Gamma Putty that is malleable and can be easily molded to any desired shape. First, we placed an ionization chamber at different depths in a solid water phantom under a Gamma Putty shield of thickness (t = 0, 3, 5, 10, 15, 20, and 25 mm, respectively) and measured the ionizing radiation on the central axis (CAX) for electron beam ranging in energies from 6 to 20 MeV. Next, we investigated the relationship between the relative ionization (RI) measured at a fixed depth for several Gamma Putty shield at different cutout diameters ranging from 2 to 5 cm for various beam energies and derived an exponential fitting equation for clinical purposes. The dose profiles along the CAX show that bremsstrahlung dominates for Gamma Putty thickness >15 mm. For high-energy beams (12–20 MeV) and all Gamma Putty thicknesses up to 25 mm, RI below 5% could not be achieved due to the strong bremsstrahlung component. However, Gamma Putty is a very suitable material for reducing the transmission factor below 5% and protecting underlying normal tissues for low-energy electron beams (6–9 MeV).

  6. Gamma Putty dosimetric studies in electron beam

    PubMed Central

    Gloi, Aime M.

    2016-01-01

    Traditionally, lead has been used for field shaping in megavoltage electron beams in radiation therapy. In this study, we analyze the dosimetric parameters of a nontoxic, high atomic number (Z = 83), bismuth-loaded material called Gamma Putty that is malleable and can be easily molded to any desired shape. First, we placed an ionization chamber at different depths in a solid water phantom under a Gamma Putty shield of thickness (t = 0, 3, 5, 10, 15, 20, and 25 mm, respectively) and measured the ionizing radiation on the central axis (CAX) for electron beam ranging in energies from 6 to 20 MeV. Next, we investigated the relationship between the relative ionization (RI) measured at a fixed depth for several Gamma Putty shield at different cutout diameters ranging from 2 to 5 cm for various beam energies and derived an exponential fitting equation for clinical purposes. The dose profiles along the CAX show that bremsstrahlung dominates for Gamma Putty thickness >15 mm. For high-energy beams (12–20 MeV) and all Gamma Putty thicknesses up to 25 mm, RI below 5% could not be achieved due to the strong bremsstrahlung component. However, Gamma Putty is a very suitable material for reducing the transmission factor below 5% and protecting underlying normal tissues for low-energy electron beams (6–9 MeV). PMID:27651563

  7. Electromagnetic and Thermal Dosimetric Techniques in Humans and its Application

    NASA Astrophysics Data System (ADS)

    Hirata, Akimasa; Fujiwara, Osamu

    There has been increasing public concern about the adverse health effects of human exposure to radio frequency fields. Radio frequency fields are also used for medical application. This paper reviews electromagnetic and thermal computational dosimetric techniques, which has been developed by the authors. The feature of the thermal dosimetric method is that body core temperature can be computed reasonably unlike conventional method. This scheme is particularly useful for intense localized or whole-body electromagnetic wave exposure. Computational examples are shown to verify the effectiveness of the proposal.

  8. [Improved program maintenance of the CIRCIS dosimetric planning system].

    PubMed

    Sevast'ianov, A I; Liutova, N A; Ratner, T G

    1983-03-01

    A special computer complex CIRCIS (Informatique, France) is used in the All-Union Cancer Research Center, USSR AMS, for the dosimetric planning of radiotherapy on 5 gamma-beam units and electron accelerator. Mathematical maintenance of the complex includes programs of the calculation of dose distribution for gamma-, inhibition and electron radiation but has no program of the calculation of the time of irradiation. The authors have devised and introduced into the complex such a program in the Fortran language that makes it possible to calculate within 2-3 min the time of irradiation for multifield rotation therapy using several units as a time, thus expediting the dosimetric planning for patients' irradiation.

  9. Dosimetric investigations of Tb3+-doped strontium silicate phosphor.

    PubMed

    Barve, R A; Suriyamurthy, N; Panigrahi, B S; Venkatraman, B

    2015-03-01

    Tb(3+)-doped SrSiO(3) phosphor synthesised by co-precipitation technique exhibits intense green emission due to cross-relaxation phenomena between Tb(3+) ions. Dosimetric properties of this phosphor have been investigated using thermoluminescence (TL) technique. A dosimetrically useful glow peak observed was at 581 K along with a linear dose response over the wide dose range (100 mGy-4 Gy). TL parameters such as trap depth (E), frequency factor (s) and the order of kinetics (b) are determined by different methods such as Chen's peak shape, initial rise, isothermal decay and variable heating rate methods. Results of these methods are compared and reported in this study.

  10. Thermoluminescent properties studies of spodumene lilac sample to dosimetric applications

    NASA Astrophysics Data System (ADS)

    Lima, L. L.; Oliveira, R. A. P.; Lima, H. R. B. R.; Santos, H. N.; Santos, J. O.; Lima, A. F.; Souza, S. O.

    2010-11-01

    This work investigates the thermoluminescent (TL) dosimetric properties in natural spodumene, LiAlSi2O6, called kunzite, from Minas Gerais State, Brazil. The mineralogical and chemical composition of this material was identified by means X-ray fluorescence and X-ray diffraction. Some dosimetric properties were studied, such as thermoluminescent emission curves as function of gamma dose. The glow curves of annealed kunzite presented two very intense TL peaks at 215 °C (peak II) and 350 °C (peak III), after gamma irradiation, being both of first kinetic order. These two most prominent peaks analyzed do not presented a linear growth in the range of 50 to 5000 Gy in the range of doses studied. The peak II also presented a very short calculated lifetime, which means it is hardly can be used in dosimetry, while the peak III has a longer lifetime and could be used in some applications for high doses dosimetry.

  11. Impact of cutout off axis on electron beam dosimetric parameters.

    PubMed

    Arunkumar, T; Supe, S S; Ravikumar, M; Sathiyan, S; Ganesh, K M

    2012-04-01

    Dosimetric changes caused by the positional uncertainty of centering a small electron cutout to the machine central axis (CAX) of the linear accelerator (linac) were investigated. Six circular cutouts with 4 cm diameter were made with their centres shifted off by 0, 2, 4, 6, 8 and 10 mm from the machine CAX. The 6 x 6 cm(2) electron applicator was used for the measurement. The percentage depth doses (PDDs) were measured at the Machine CAX and also with respect to cutout centre for 6, 9, 12, 16 and 20 MeV electron beams. The in-line and cross-line profiles were measured at the depth of maximum dose (R100). The relative output factor (ROF) was measured at the reference depth. All the measurements were made at nominal source to surface distance (100 cm SSD) as well as at extended SSDs (100, 102, 106 and 110 cm). When the cutout centre was shifted away from the machine CAX for low energy beams the depth of 100% dose (R(100)), the depth of 90% dose (R(90)) and the depth of 80% dose (R(80)) had no significant change. For higher energies (>9 MeV) there was a reduction in these dosimetric parameters. The isodose coverage of the in-line and cross-line profile was reduced when the cutout centre was shifted away from the machine CAX. At extended SSDs the dosimetric changes are only because of geometric divergence of the beam and not by the positional uncertainty of the cutout. It is important for the radiation oncologist, dosimetrist, therapist and physicist to note such dosimetric changes while using the electron beam to the patients. PMID:22335408

  12. Dosimetric Effects of Setup Uncertainties on Breast Treatment Delivery

    SciTech Connect

    Harron, Elizabeth Christine McCallum, Hazel Mhairi; Lambert, Elizabeth Lyn; Lee, Daniela; Lambert, Geoffrey David

    2008-01-01

    This study aimed to assess the dosimetric impact of setup errors during the delivery of radiotherapy to the breast, and use this information to make recommendations on intervention tolerances for portal imaging of breast treatments. Translational and rotational setup errors were simulated for 10 recent breast patients using an Oncentra MasterPlan treatment planning system. The effect of these errors on the breast and tumor bed target volumes receiving 95% and 107% of the prescribed dose were assessed. For the majority of patients, shifts of up to 10 mm or a 4 deg. patient rotation about the cranio-caudal axis had no significant effect on the dose distribution. Changes in dosimetry were more likely if the reference plan contained large hot or cold spots. For a typical patient, it is estimated that a shift of 5 mm in any one direction, or a 2 deg. patient rotation would not cause more than a 5% change in the target volume receiving between 95% and 107% of the prescribed dose. If combinations of errors occur, greater dosimetric changes would be expected. It is concluded that individual patient shifts of up to 5 mm or rotations about the cranio-caudal axis of 2 deg. or less are unlikely to affect dose-volume histogram parameters by an amount judged as clinically significant. Setup errors exceeding these values may cause large dosimetric changes for some patients, particularly those with larger hot or cold regions in the dose distribution, and intervention is therefore recommended.

  13. Proton Radiotherapy for Liver Tumors: Dosimetric Advantages Over Photon Plans

    SciTech Connect

    Wang Xiaochun Krishnan, Sunil; Zhang Xiaodong; Dong Lei; Briere, Tina; Crane, Christopher H.; Martel, Mary; Gillin, Michael; Mohan, Radhe; Beddar, Sam

    2008-01-01

    The purpose of the study is to dosimetrically investigate the advantages of proton radiotherapy over photon radiotherapy for liver tumors. The proton plan and the photon plan were designed using commercial treatment planning systems. The treatment target dose conformity and heterogeneity and dose-volume analyses of normal structures were compared between proton and photon radiotherapy for 9 patients with liver tumors. Proton radiotherapy delivered a more conformal target dose with slightly less homogeneity when compared with photon radiotherapy. Protons significantly reduced the fractional volume of liver receiving dose greater or equal to 30 Gy (V{sub 30}) and the mean liver dose. The stomach and duodenal V{sub 45} were significantly lower with the use of proton radiotherapy. The V{sub 40} and V{sub 50} of the heart and the maximum spinal cord dose were also significantly lower with the use of proton radiotherapy. Protons were better able to spare one kidney completely and deliver less dose to one (generally the left) kidney than photons. The mean dose to the total body and most critical structures was significantly decreased using protons when compared to corresponding photon plans. In conclusion, our study suggests the dosimetric benefits of proton radiotherapy over photon radiotherapy. These dosimetric advantages of proton plans may permit further dose escalation with lower risk of complications.

  14. SU-E-J-52: Dosimetric Benefit of Adaptive Re-Planning in Lung Cancer Stereotactic Body Radiotherapy (SBRT)

    SciTech Connect

    Jia, J; Tian, Z; Gu, X; Yan, H; Jiang, S; Jia, X

    2014-06-01

    Purpose: To investigate the dosimetric benefit of adaptive re-planning for lung stereotactic body radiotherapy(SBRT). Methods: Five lung cancer patients with SBRT treatment were retrospectively investigated. Our in-house supercomputing online re-planning environment (SCORE) was used to realize the re-planning process. First a deformable image registration was carried out to transfer contours from treatment planning CT to each treatment CBCT. Then an automatic re-planning using original plan DVH guided fluence-map optimization is performed to get a new plan for the up-to-date patient geometry. We compared the re-optimized plan to the original plan projected on the up-to-date patient geometry in critical dosimetric parameters, such as PTV coverage, spinal cord maximum and volumetric constraint dose, esophagus maximum and volumetric constraint dose. Results: The average volume of PTV covered by prescription dose for all patients was improved by 7.56% after the adaptive re-planning. The volume of the spinal cord receiving 14.5Gy and 23Gy (V14.5, V23) decreased by 1.48% and 0.68%, respectively. For the esophagus, the volume receiving 19.5Gy (V19.5) reduced by 1.37%. Meanwhile, the maximum dose dropped off by 2.87% for spinal cord and 4.80% for esophagus. Conclusion: Our experimental results demonstrate that adaptive re-planning for lung SBRT has the potential to minimize the dosimetric effect of inter-fraction deformation and thus improve target coverage while reducing the risk of toxicity to nearby normal tissues.

  15. CURRENT STATUS OF INDIVIDUAL DOSIMETRIC MONITORING IN UKRAINE.

    PubMed

    Chumak, V; Deniachenko, N; Makarovska, O; Mihailescu, L-C; Prykhodko, A; Voloskyi, V; Vanhavere, F

    2016-09-01

    About 50 000 workers are being occupationally exposed to radiation in Ukraine. Individual dosimetric monitoring (IDM) is provided by 77 dosimetry services and laboratories of very different scale with a number of monitored workers ranging from several persons to ∼9000. In the present work, the current status of personal dosimetry in Ukraine was studied. The First National Intercomparison (FNI) of the IDM labs was accompanied by a survey of the laboratory operation in terms of coverage, types of dosimetry provided, instrumentation and methodologies used, metrological support, data recording, etc. Totally, 34 laboratories responded to the FNI call, and 18 services with 19 different personal dosimetry systems took part in the intercomparison exercise providing 24 dosimeters each for blind irradiation to photons of 6 different qualities (ISO N-series X-rays, S-Cs and S-Co sources) in a dose range of 5-60 mSv. Performance of the dosimetry labs was evaluated according to ISO 14146 criteria of matching trumpet curves with H0 = 0.2 mSv. The test revealed that 8 of the 19 systems meet ISO 14146 criteria in full, 5 other labs show marginal performance and 6 laboratories demonstrated catastrophic quality of dosimetric results. Altogether, 18 participating labs provide dosimetric monitoring to 37 477 workers (about three-fourths of all occupationally exposed workers), usually on monthly (nuclear industry) or quarterly (rest of applications) basis. Of this number, 20 664 persons (55 %) receive completely adequate individual monitoring, and the number of personnel receiving IDM of inadequate quality counts 3054 persons. PMID:26979804

  16. Patient doses and dosimetric evaluations in interventional cardiology.

    PubMed

    Bor, Dogan; Olğar, Turan; Toklu, Türkay; Cağlan, Ayça; Onal, Elif; Padovani, Renato

    2009-03-01

    Interventional cardiological examinations may be associated with excessive radiation exposures which may cause skin injuries and higher probabilities of stochastic effects. Dose-area product (DAP) and skin doses of 325 patients were measured using alternative dosimetric techniques for different cardiological examinations. Data were collected from five different systems with the involvement of 11 cardiologists. All these dosimetric information has been collected separately for each of 10 projections together with the exposure parameters of X-ray systems. Mean DAP values measured with a transparent ion chamber were 49.1 Gy cm(2), 66.8 Gy cm(2), 106.9 Gy cm(2) and 124.7 Gy cm(2), respectively, for coronary angiography (CA), percutaneous transluminal coronary angioplasty (PTCA) or stent (PT-SI), coronary angiography and/or PTCA and/or stent (CA-PT-SI), and ablation examinations. Radiochromic films, thermoluminescent dosimeters (TLD) and point measurement of air kerma (AK) were carried out for skin dose assessments. Skin doses of 23 patients measured with radiochromic films were found to be between 2 Gy and 6 Gy. Although the complexity of the procedures was the major reason for these excessive doses, considerable contributions of high X-ray output of some fluoroscopy units were also noticed. In addition to the direct measurement of DAP, alternative DAP values were also determined from the skin dose measurement techniques; exposed areas were summed on digitized radiochromic films in one technique, The product of AK reading with X-ray field size measured at the patient entrance using slow X-ray films was taken as another DAP. Good correlations were found among the DAP results and also between the entrance skin doses calculated from AK measurements and direct DAP readings (R(2)=0.91). A trigger DAP value of 130 Gy cm(2) for the 2 Gy of skin doses was derived from this relationship. Collection of dosimetric data for each projection was also investigated regarding a

  17. Biologic data, models, and dosimetric methods for internal emitters

    SciTech Connect

    Weber, D.A.

    1990-01-01

    The absorbed radiation dose from internal emitters has been and will remain a pivotal factor in assessing risk and therapeutic utility in selecting radiopharmaceuticals for diagnosis and treatment. Although direct measurements of absorbed dose and dose distributions in vivo have been and will continue to be made in limited situations, the measurement of the biodistribution and clearance of radiopharmaceuticals in human subjects and the use of this data is likely to remain the primary means to approach the calculation and estimation of absorbed dose from internal emitters over the next decade. Since several approximations are used in these schema to calculate dose, attention must be given to inspecting and improving the application of this dosimetric method as better techniques are developed to assay body activity and as more experience is gained in applying these schema to calculating absorbed dose. Discussion of the need for considering small scale dosimetry to calculate absorbed dose at the cellular level will be presented in this paper. Other topics include dose estimates for internal emitters, biologic data mathematical models and dosimetric methods employed. 44 refs.

  18. Dosimetric evaluation of a three-dimensional treatment planning system

    PubMed Central

    Murugan, Appasamy; Valas, Xavier Sidonia; Thayalan, Kuppusamy; Ramasubramanian, Velayudham

    2011-01-01

    The computerized treatment planning system plays a major role in radiation therapy in delivering correct radiation dose to the patients within ±5% as recommended by the ICRU. To evaluate the dosimetric performance of the Treatment Planning system (TPS) with three-dimensional dose calculation algorithm using the basic beam data measured for 6 MV X-rays. Eleven numbers of test cases were created according to the Technical Report Series-430 (TRS 430) and are used to evaluate the TPS in a homogeneous water phantom. These cases involve simple field arrangements as well as the presence of a low-density material in the beam to resemble an air in-homogeneity. Absolute dose measurements were performed for the each case with the MU calculation given by the TPS, and the measured dose is compared with the corresponding TPS calculated dose values. The result yields a percentage difference maximum of 2.38% for all simple test cases. For complex test cases in the presence of in-homogeneity, beam modifiers or beam modifiers with asymmetric fields a maximum percentage difference of 5.94% was observed. This study ensures that the dosimetric calculations performed by the TPS are within the accuracy of ±5% which is very much warranted in patient dose delivery. The test procedures are simple, not only during the installation of TPS, but also repeated at periodic intervals. PMID:21430854

  19. 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

  20. Dosimetric precision of an ion beam tracking system

    PubMed Central

    2010-01-01

    Background Scanned ion beam therapy of intra-fractionally moving tumors requires motion mitigation. GSI proposed beam tracking and performed several experimental studies to analyse the dosimetric precision of the system for scanned carbon beams. Methods A beam tracking system has been developed and integrated in the scanned carbon ion beam therapy unit at GSI. The system adapts pencil beam positions and beam energy according to target motion. Motion compensation performance of the beam tracking system was assessed by measurements with radiographic films, a range telescope, a 3D array of 24 ionization chambers, and cell samples for biological dosimetry. Measurements were performed for stationary detectors and moving detectors using the beam tracking system. Results All detector systems showed comparable data for a moving setup when using beam tracking and the corresponding stationary setup. Within the target volume the mean relative differences of ionization chamber measurements were 0.3% (1.5% standard deviation, 3.7% maximum). Film responses demonstrated preserved lateral dose gradients. Measurements with the range telescope showed agreement of Bragg peak depth under motion induced range variations. Cell survival experiments showed a mean relative difference of -5% (-3%) between measurements and calculations within the target volume for beam tracking (stationary) measurements. Conclusions The beam tracking system has been successfully integrated. Full functionality has been validated dosimetrically in experiments with several detector types including biological cell systems. PMID:20591160

  1. Dosimetric algorithm to reproduce isodose curves obtained from a LINAC.

    PubMed

    Estrada Espinosa, Julio Cesar; Martínez Ovalle, Segundo Agustín; Pereira Benavides, Cinthia Kotzian

    2014-01-01

    In this work isodose curves are obtained by the use of a new dosimetric algorithm using numerical data from percentage depth dose (PDD) and the maximum absorbed dose profile, calculated by Monte Carlo in a 18 MV LINAC. The software allows reproducing the absorbed dose percentage in the whole irradiated volume quickly and with a good approximation. To validate results an 18 MV LINAC with a whole geometry and a water phantom were constructed. On this construction, the distinct simulations were processed by the MCNPX code and then obtained the PDD and profiles for the whole depths of the radiation beam. The results data were used by the code to produce the dose percentages in any point of the irradiated volume. The absorbed dose for any voxel's size was also reproduced at any point of the irradiated volume, even when the voxels are considered to be of a pixel's size. The dosimetric algorithm is able to reproduce the absorbed dose induced by a radiation beam over a water phantom, considering PDD and profiles, whose maximum percent value is in the build-up region. Calculation time for the algorithm is only a few seconds, compared with the days taken when it is carried out by Monte Carlo. PMID:25045398

  2. Dosimetric Algorithm to Reproduce Isodose Curves Obtained from a LINAC

    PubMed Central

    Estrada Espinosa, Julio Cesar; Martínez Ovalle, Segundo Agustín; Pereira Benavides, Cinthia Kotzian

    2014-01-01

    In this work isodose curves are obtained by the use of a new dosimetric algorithm using numerical data from percentage depth dose (PDD) and the maximum absorbed dose profile, calculated by Monte Carlo in a 18 MV LINAC. The software allows reproducing the absorbed dose percentage in the whole irradiated volume quickly and with a good approximation. To validate results an 18 MV LINAC with a whole geometry and a water phantom were constructed. On this construction, the distinct simulations were processed by the MCNPX code and then obtained the PDD and profiles for the whole depths of the radiation beam. The results data were used by the code to produce the dose percentages in any point of the irradiated volume. The absorbed dose for any voxel's size was also reproduced at any point of the irradiated volume, even when the voxels are considered to be of a pixel's size. The dosimetric algorithm is able to reproduce the absorbed dose induced by a radiation beam over a water phantom, considering PDD and profiles, whose maximum percent value is in the build-up region. Calculation time for the algorithm is only a few seconds, compared with the days taken when it is carried out by Monte Carlo. PMID:25045398

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

    SciTech Connect

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

    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% 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.

  4. Analysis of superficial fluorescence patterns in nonmelanoma skin cancer during photodynamic therapy by a dosimetric model

    NASA Astrophysics Data System (ADS)

    Salas-García, I.; Fanjul-Vélez, F.; Arce-Diego, J. L.

    2016-03-01

    In this work the superficial fluorescence patterns in different nonmelanoma skin cancers and their photodynamic treatment response are analysed by a fluorescence based dosimetric model. Results show differences of even more than 50% in the fluorescence patterns as photodynamic therapy progresses depending on the malignant tissue type. They demonstrate the great relevance of the biological media as an additional dosimetric factor and contribute to the development of a future customized therapy with the assistance of dosimetric tools to interpret the fluorescence images obtained during the treatment monitoring and the differential photodiagnosis.

  5. Dosimetric Effect of Online Image-Guided Anatomical Interventions for Postprostatectomy Cancer Patients

    SciTech Connect

    Diot, Quentin; Olsen, Christine; Kavanagh, Brian; Raben, David; Miften, Moyed

    2011-02-01

    Purpose: To assess daily variations in delivered doses in postprostatectomy patients, using kilovoltage cone-beam CT (CBCT) datasets acquired before and after interventions to correct for observed distortions in volume/shape of rectum and bladder. Methods and Materials: Seventeen consecutive patients treated with intensity-modulated radiotherapy to the prostate bed were studied. For patients with large anatomical variations, quantified by either a rectal wall displacement of >5 mm or bladder volume change of >50% on the CBCT compared with the planning CT, an intervention was performed to adjust the rectum and/or bladder filling. Cumulative doses over the pre- and post-intervention fractions were calculated by tracking the position of the planning CT voxels on different CBCTs using a deformable surface-mapping algorithm. Dose and displacements vectors were projected on two-dimensional maps, the minimal dose received by the highest 95% of the planing target volume (PTV D95) and the highest 10% of the rectum volume (D10) as well as the bladder volume receiving >2 Gy (V2) were evaluated. Results: Of 544 fractions, 96 required intervention. Median (range) number of interventions per patient was 5 (2-12). Compared with the planning values, the mean (SD) pre- vs. postintervention value for PTV D95 was -2% (2%) vs. -1% (2%) (p < 0.12), for rectum D10 was -1% (4%) vs. +1% (4%) (p < 0.24), and for bladder V2 was +6% vs. +20% (p < 0.84). Conclusions: Interventions to reduce treatment volume deformations due to bladder and rectum fillings are not necessary when patients receive daily accurate CBCT localization, and the frequency of those potential interventions is low. However, for hypofractionated treatments, the relative frequency can significantly increase, and interventions can become more dosimetrically beneficial.

  6. Dosimetric effects of a high-density spinal implant

    NASA Astrophysics Data System (ADS)

    Kairn, T.; Crowe, S. B.; Kenny, J.; Mitchell, J.; Burke, M.; Schlect, D.; Trapp, J. V.

    2013-06-01

    In this study, a treatment plan for a spinal lesion, with all beams transmitted though a titanium vertebral reconstruction implant, was used to investigate the potential effect of a high-density implant on a three-dimensional dose distribution for a radiotherapy treatment. The BEAMnrc/DOSXYZnrc and MCDTK Monte Carlo codes were used to simulate the treatment using both a simplified, recltilinear model and a detailed model incorporating the full complexity of the patient anatomy and treatment plan. The resulting Monte Carlo dose distributions showed that the commercial treatment planning system failed to accurately predict both the depletion of dose downstream of the implant and the increase in scattered dose adjacent to the implant. Overall, the dosimetric effect of the implant was underestimated by the commercial treatment planning system and overestimated by the simplified Monte Carlo model. The value of performing detailed Monte Carlo calculations, using the full patient and treatment geometry, was demonstrated.

  7. EFFECTIVE DOSIMETRIC HALF LIFE OF CESIUM 137 SOIL CONTAMINATION

    SciTech Connect

    Jannik, T; P Fledderman, P; Michael Paller, M

    2008-01-09

    In the early 1960s, an area of privately-owned swamp adjacent to the US Department of Energy's Savannah River Site (SRS), known as Creek Plantation, was contaminated by site operations. Studies conducted in 1974 estimated that approximately 925 GBq of {sup 137}Cs was deposited in the swamp. Subsequently, a series of surveys--composed of 52 monitoring locations--was initiated to characterize and trend the contaminated environment. The annual, potential, maximum doses to a hypothetical hunter were estimated by conservatively using the maximum {sup 137}Cs concentrations measured in the soil. The purpose of this report is to calculate an 'effective dosimetric' half-life for {sup 137}Cs in soil (based on the maximum concentrations) and compare it to the effective environmental half-life (based on the geometric mean concentrations).

  8. Bremsstrahlung dosimetric parameters of beta-emitting therapeutic radionuclides

    NASA Astrophysics Data System (ADS)

    Manjunatha, H. C.

    2016-03-01

    Dosimetric parameters such as efficiency of bremsstrahlung, probability of energy loss of beta during bremsstrahlung production, intensity and dose rate of high, medium and low-energy beta-emitting therapeutic radionuclides in different tissues of human organs are computed. These parameters are lower in adipose tissue than all other studied tissues. The efficiency, intensity and dose rate of bremsstrahlung increases with maximum energy of the beta nuclide (Emax) and modified atomic number (Zmod) of the target tissue. The estimated bremsstrahlung efficiency, intensity and dose rate are useful in the calculations of photon track-length distributions. These parameters are useful to determine the quality and quantity of the bremsstrahlung radiation (known as the source term). Precise estimation of this source term is very important in planning for radiotherapy and diagnosis.

  9. Adaptive radiotherapy in lung cancer: dosimetric benefits and clinical outcome

    PubMed Central

    Kataria, T; Bisht, S S; Goyal, S; Pushpan, L; Abhishek, A; Govardhan, HB; Kumar, V; Sharma, K; Jain, S; Basu, T; Srivastava, A

    2014-01-01

    Objective: Anatomical changes during radiotherapy (RT) might introduce discrepancies between planned and delivered doses. This study evaluates the need for adaptive treatment in lung cancer RT. Methods: 15 patients with non-small-cell lung cancer, undergoing radical RT with or without concurrent chemotherapy, consecutively underwent planning CT scans at baseline and after 44–46 Gy. Target volumes were delineated on both scans. Phase I delivered 44–46 Gy to the initial planning target volume (PTV). Two Phase II plans for 16–20 Gy were developed on initial and mid-treatment scans, the treatment being delivered with the mid-treatment plan. The second CT structure set was fused with the initial scan data set using dose wash. Volumetric and dosimetric changes in target volumes and critical structures were assessed. Results: There was significant reduction in primary gross tumour volume (34.00%; p = 0.02) and PTV (34.70%; p < 0.01) in the second scan. In Plan 2, delivering the same dose to the initial PTV would have resulted in a significantly higher dose to the lung PTV (V20, 52.18%; V5, 21.76%; mean, 23.93%), contralateral lung (mean, 29.43%), heart (V10, 81.47%; V5, 56.62%; mean, 35.21%) and spinal cord (maximum dose, 37.53%). Conclusion: Treatment replanning can account for anatomical changes during RT and thereby enable better normal tissue sparing, while allowing radical target doses with the possibility of maximizing local control. Advances in knowledge: This study supports the sparse dosimetric data regarding the quantitative tumour volume reduction, re-emphasizing the need for adaptive replanning for minimizing normal tissue toxicity without compromising local control, and adds to the existing body of literature. PMID:24628269

  10. Dosimetric Analysis of Respiratory-Gated Radiotherapy for Hepatocellular Carcinoma

    SciTech Connect

    Xi Mian; Zhang Li; Liu Mengzhong; Deng Xiaowu; Huang Xiaoyan; Liu Hui

    2011-07-01

    The purpose of this study was to define individualized internal target volume (ITV) for hepatocellular carcinoma (HCC) using 4D computed tomography (4DCT), and to determine the geometric and dosimetric benefits of respiratory gating. Gross tumor volumes (GTVs) were contoured on 10 respiratory phases of 4DCT images for 12 patients with HCC. Three treatment plans were prepared using different planning target volumes (PTVs): (1) PTV{sub 3D}, derived from a single helical clinical target volume (CTV) plus conventional margins; (2) PTV{sub 10phases}, derived from ITV{sub 10phases}, which encompassed all 10 CTVs plus an isotropic margin of 0.8 cm; (3) PTV{sub gating}, derived from ITV{sub gating}, which encompassed three CTVs within gating-window at end-expiration plus an isotropic margin of 0.8 cm. The PTV{sub 3D} was the largest volume for all patients. The ITV-based plans and gating plans spared more normal tissues than 3D plans, especially the liver. Without increasing normal tissue complication probability of the 3D plans, the ITV-based plans allowed for increasing the calculated dose from 50.8 Gy to 54.7 Gy on average, and the gating plans could further escalate the dose to 58.5 Gy. Compared with ITV-based plans, the dosimetric gains with gating plan strongly correlated with GTV mobility in the craniocaudal direction. The ITV-based plans can ensure target coverage with less irradiation of normal tissues compared with 3D plans. Respiratory-gated radiotherapy can further reduce the target volumes to spare more surrounding tissues and allow dose escalation, especially for patients with tumor mobility >1 cm.

  11. SU-E-T-134: Dosimetric Implications From Organ Segmentation

    SciTech Connect

    Wu, Z; Turian, J; Chu, J

    2014-06-01

    Purpose: To evaluate the dosimetric implications resulting from organ segmentation performed by different clinical experts Methods: Twelve patients received SBRT treatment to thoracic region within the past year were selected for this study. Three physicians contoured a set of organs following RTOG guideline. DVHs of all contours were generated from the approved plans used for treatment, and were compared to those produced during planning. Most OARs were evaluated on their max dose, some, such as heart and chest wall, were also evaluated on metrics such as max dose to 4cc of volume, or 30Gy volume dose. Results: In general, there is a greater dosimetric difference between the RTOG contour sets and clinical contour sets than among the three RTOG contour sets themselves for each patient. For example, there was no difference in esophagus max dose between the RTOG contour sets for ten patients. However, they showed an average of 2.3% higher max dose than the clinical contour set, with a standard deviation of 6.6%. The proximal bronchial tree (PBT) showed a similar behavior. The average difference of PBT max dose for seven patients is 0% between the three RTOG contour sets, with standard deviation of 1%. They showed an average of 16.1% higher max dose than the clinical contour set, with a standard deviation of 126%. Conclusion: This study shows that using RTOG contouring standards improves segmentation consistency between different physicians; most of the contours examined showed less than 1% dose difference. When RTOG contour sets were compared to the clinical contour set, the differences are much more significant. Thus it is important to standardize contouring guidelines in radiation therapy treatment planning. This will reduce uncertainties in clinical outcome analysis and research studies.

  12. A revised dosimetric model of the head and brain

    SciTech Connect

    Bolch, W.E.; Poston, J.W. Sr.

    1995-05-01

    The use of PET and SPECT radiopharmaceuticals in brain imaging has greatly expanded over the past several years. Many of these agents localize within particular subregions of the brain, thus allowing for detailed physiologic and metabolic imaging. Dosimetric models to support these advances in nuclear medicine have been lacking. For example, the brain within the phantom of MIRD Pamphlet No. 5 Revised is modeled simply as a single ellipsoid of tissue with no differentiation of its internal structures. To address this need, the MIRD Committee established a Task Group in 1992 to construct a revised dosimetric model of the brain to include the following subregions: the cerebral cortex, the white matter, the cerebellum, the thalamus, the caudate nucleus, the lentiform nucleus (putamen and globus pallidus), the cerebral spinal fluid (within the subarachnoid space of the brain), the lateral ventricles, and the third ventricle. Estimates of both electron and photon absorbed fractions (AF) were subsequently calculated using the EGS4 radiation transport code. For most of the internal brain structures, electron AFs are shown to fall fellow unity for all regions within the energy range of {approximately}200 keV to 4 MeV. For example, AFs for the caudate nucleus as both a source and target region and estimated as 0.98, 0.84, 0.39 for 200-keV, 1-MeV, and 4-MeV electron sources, respectively. Corresponding AFs within the white matter as a source and target region are estimated as 1.0, 0.95, and 0.79 for these same electron energies. Revised S values were subsequently calculated for a variety of beta-particle and positron emitters used in brain imaging.

  13. Dosimetrically determined doses of radioiodine for the treatment of metastatic thyroid carcinoma.

    PubMed

    Van Nostrand, Douglas; Atkins, Frank; Yeganeh, Fred; Acio, Elmo; Bursaw, Randy; Wartofsky, Leonard

    2002-02-01

    In the absence of definitive studies relating radioiodine dose to outcomes, selection of a dose of radioiodine to treat metastatic thyroid carcinoma is problematic, and several approaches have been used. These include empiric fixed doses and doses used on dosimetric approaches specific for each patient. This paper is a review of the rationale and technique for dosimetrically-determined doses of radioiodine for the treatment of metastatic thyroid carcinoma. This review (1) discusses the alternatives for selection of a dose, (2) discusses the two major approaches for determining radioiodine doses dosimetrically, (3) briefly reviews several modifications of these approaches, (4) reviews the literature regarding the results, (5) discusses the side effects of these different approaches, and (6) concludes with recommendations for patient management and future research. This review does not address use of dosimetrically-determined doses of radioiodine for the initial ablation of thyroid tissue postoperatively.

  14. Effects of Dosimetrically Guided I-131 Therapy on Hematopoiesis in Patients With Differentiated Thyroid Cancer.

    PubMed

    Bikas, Athanasios; Schneider, Mark; Desale, Sameer; Atkins, Frank; Mete, Mihriye; Burman, Kenneth D; Wartofsky, Leonard; Van Nostrand, Douglas

    2016-04-01

    A retrospective analysis was performed to evaluate the effects of dosimetrically-guided I-131 treatment on hematopoiesis. Statistically significant decreases in CBC parameters following a specific time-pattern were shown.

  15. IPIP: A new approach to inverse planning for HDR brachytherapy by directly optimizing dosimetric indices

    SciTech Connect

    Siauw, Timmy; Cunha, Adam; Atamtuerk, Alper; Hsu, I-Chow; Pouliot, Jean; Goldberg, Ken

    2011-07-15

    Purpose: Many planning methods for high dose rate (HDR) brachytherapy require an iterative approach. A set of computational parameters are hypothesized that will give a dose plan that meets dosimetric criteria. A dose plan is computed using these parameters, and if any dosimetric criteria are not met, the process is iterated until a suitable dose plan is found. In this way, the dose distribution is controlled by abstract parameters. The purpose of this study is to develop a new approach for HDR brachytherapy by directly optimizing the dose distribution based on dosimetric criteria. Methods: The authors developed inverse planning by integer program (IPIP), an optimization model for computing HDR brachytherapy dose plans and a fast heuristic for it. They used their heuristic to compute dose plans for 20 anonymized prostate cancer image data sets from patients previously treated at their clinic database. Dosimetry was evaluated and compared to dosimetric criteria. Results: Dose plans computed from IPIP satisfied all given dosimetric criteria for the target and healthy tissue after a single iteration. The average target coverage was 95%. The average computation time for IPIP was 30.1 s on an Intel(R) Core{sup TM}2 Duo CPU 1.67 GHz processor with 3 Gib RAM. Conclusions: IPIP is an HDR brachytherapy planning system that directly incorporates dosimetric criteria. The authors have demonstrated that IPIP has clinically acceptable performance for the prostate cases and dosimetric criteria used in this study, in both dosimetry and runtime. Further study is required to determine if IPIP performs well for a more general group of patients and dosimetric criteria, including other cancer sites such as GYN.

  16. Error Analysis of non-TLD HDR Brachytherapy Dosimetric Techniques

    NASA Astrophysics Data System (ADS)

    Amoush, Ahmad

    The American Association of Physicists in Medicine Task Group Report43 (AAPM-TG43) and its updated version TG-43U1 rely on the LiF TLD detector to determine the experimental absolute dose rate for brachytherapy. The recommended uncertainty estimates associated with TLD experimental dosimetry include 5% for statistical errors (Type A) and 7% for systematic errors (Type B). TG-43U1 protocol does not include recommendation for other experimental dosimetric techniques to calculate the absolute dose for brachytherapy. This research used two independent experimental methods and Monte Carlo simulations to investigate and analyze uncertainties and errors associated with absolute dosimetry of HDR brachytherapy for a Tandem applicator. An A16 MicroChamber* and one dose MOSFET detectors† were selected to meet the TG-43U1 recommendations for experimental dosimetry. Statistical and systematic uncertainty analyses associated with each experimental technique were analyzed quantitatively using MCNPX 2.6‡ to evaluate source positional error, Tandem positional error, the source spectrum, phantom size effect, reproducibility, temperature and pressure effects, volume averaging, stem and wall effects, and Tandem effect. Absolute dose calculations for clinical use are based on Treatment Planning System (TPS) with no corrections for the above uncertainties. Absolute dose and uncertainties along the transverse plane were predicted for the A16 microchamber. The generated overall uncertainties are 22%, 17%, 15%, 15%, 16%, 17%, and 19% at 1cm, 2cm, 3cm, 4cm, and 5cm, respectively. Predicting the dose beyond 5cm is complicated due to low signal-to-noise ratio, cable effect, and stem effect for the A16 microchamber. Since dose beyond 5cm adds no clinical information, it has been ignored in this study. The absolute dose was predicted for the MOSFET detector from 1cm to 7cm along the transverse plane. The generated overall uncertainties are 23%, 11%, 8%, 7%, 7%, 9%, and 8% at 1cm, 2cm, 3cm

  17. Dosimetric characterization of two radium sources for retrospective dosimetry studies

    SciTech Connect

    Candela-Juan, C.; Karlsson, M.; Lundell, M.; Ballester, F.; Tedgren, Å. Carlsson

    2015-05-15

    Purpose: During the first part of the 20th century, {sup 226}Ra was the most used radionuclide for brachytherapy. Retrospective accurate dosimetry, coupled with patient follow up, is important for advancing knowledge on long-term radiation effects. The purpose of this work was to dosimetrically characterize two {sup 226}Ra sources, commonly used in Sweden during the first half of the 20th century, for retrospective dose–effect studies. Methods: An 8 mg {sup 226}Ra tube and a 10 mg {sup 226}Ra needle, used at Radiumhemmet (Karolinska University Hospital, Stockholm, Sweden), from 1925 to the 1960s, were modeled in two independent Monte Carlo (MC) radiation transport codes: GEANT4 and MCNP5. Absorbed dose and collision kerma around the two sources were obtained, from which the TG-43 parameters were derived for the secular equilibrium state. Furthermore, results from this dosimetric formalism were compared with results from a MC simulation with a superficial mould constituted by five needles inside a glass casing, placed over a water phantom, trying to mimic a typical clinical setup. Calculated absorbed doses using the TG-43 formalism were also compared with previously reported measurements and calculations based on the Sievert integral. Finally, the dose rate at large distances from a {sup 226}Ra point-like-source placed in the center of 1 m radius water sphere was calculated with GEANT4. Results: TG-43 parameters [including g{sub L}(r), F(r, θ), Λ, and s{sub K}] have been uploaded in spreadsheets as additional material, and the fitting parameters of a mathematical curve that provides the dose rate between 10 and 60 cm from the source have been provided. Results from TG-43 formalism are consistent within the treatment volume with those of a MC simulation of a typical clinical scenario. Comparisons with reported measurements made with thermoluminescent dosimeters show differences up to 13% along the transverse axis of the radium needle. It has been estimated that

  18. SU-E-J-200: A Dosimetric Analysis of 3D Versus 4D Image-Based Dose Calculation for Stereotactic Body Radiation Therapy in Lung Tumors

    SciTech Connect

    Ma, M; Rouabhi, O; Flynn, R; Xia, J; Bayouth, J

    2014-06-01

    Purpose: To evaluate the dosimetric difference between 3D and 4Dweighted dose calculation using patient specific respiratory trace and deformable image registration for stereotactic body radiation therapy in lung tumors. Methods: Two dose calculation techniques, 3D and 4D-weighed dose calculation, were used for dosimetric comparison for 9 lung cancer patients. The magnitude of the tumor motion varied from 3 mm to 23 mm. Breath-hold exhale CT was used for 3D dose calculation with ITV generated from the motion observed from 4D-CT. For 4D-weighted calculation, dose of each binned CT image from the ten breathing amplitudes was first recomputed using the same planning parameters as those used in the 3D calculation. The dose distribution of each binned CT was mapped to the breath-hold CT using deformable image registration. The 4D-weighted dose was computed by summing the deformed doses with the temporal probabilities calculated from their corresponding respiratory traces. Dosimetric evaluation criteria includes lung V20, mean lung dose, and mean tumor dose. Results: Comparing with 3D calculation, lung V20, mean lung dose, and mean tumor dose using 4D-weighted dose calculation were changed by −0.67% ± 2.13%, −4.11% ± 6.94% (−0.36 Gy ± 0.87 Gy), −1.16% ± 1.36%(−0.73 Gy ± 0.85 Gy) accordingly. Conclusion: This work demonstrates that conventional 3D dose calculation method may overestimate the lung V20, MLD, and MTD. The absolute difference between 3D and 4D-weighted dose calculation in lung tumor may not be clinically significant. This research is supported by Siemens Medical Solutions USA, Inc and Iowa Center for Research By Undergraduates.

  19. Dosimetrical evaluation of Leksell Gamma Knife 4C radiosurgery unit

    NASA Astrophysics Data System (ADS)

    Sajeev, Thomas; Mustafa, Mohamed M.; Supe, Sanjay S.

    2011-01-01

    A number of experiments was performed using standard protocols, in order to evaluate the dosimetric accuracy of Leksell Gamma Knife 4C unit. Verification of the beam alignment has been performed for all collimators using solid plastic head phantom and Gafchromic™ type MD-55 films. The study showed a good agreement of Leksell Gammaplan calculated dose profiles with experimentally determined profiles in all three axes. Isocentric accuracy is verified using a specially machined cylindrical aluminium film holder tool made with very narrow geometric tolerances aligned between trunnions of 4 mm collimator. Considering all uncertainties in all three dimensions, the estimated accuracy of the unit was 0.1 mm. Dose rate at the centre point of the unit has been determined according to the IAEA, TRS-398 protocol, using Unidose-E (PTW-Freiburg, Germany) with a 0.125 cc ion chamber, over a period of 6 years. The study showed that the Leksell Gamma Knife 4C unit is excellent radiosurgical equipment with high accuracy and precision, which makes it possible to deliver larger doses of radiation, within the limits defined by national and international guidelines, applicable for stereotactic radiosurgery procedures.

  20. A comprehensive approach to age-dependent dosimetric modeling

    SciTech Connect

    Leggett, R.W.; Cristy, M.; Eckerman, K.F.

    1986-01-01

    In the absence of age-specific biokinetic models, current retention models of the International Commission on Radiological Protection (ICRP) frequently are used as a point of departure for evaluation of exposures to the general population. These models were designed and intended for estimation of long-term integrated doses to the adult worker. Their format and empirical basis preclude incorporation of much valuable physiological information and physiologically reasonable assumptions that could be used in characterizing the age-specific behavior of radioelements in humans. In this paper we discuss a comprehensive approach to age-dependent dosimetric modeling in which consideration is given not only to changes with age in masses and relative geometries of body organs and tissues but also to best available physiological and radiobiological information relating to the age-specific biobehavior of radionuclides. This approach is useful in obtaining more accurate estimates of long-term dose commitments as a function of age at intake, but it may be particularly valuable in establishing more accurate estimates of dose rate as a function of age. Age-specific dose rates are needed for a proper analysis of the potential effects on estimates or risk of elevated dose rates per unit intake in certain stages of life, elevated response per unit dose received during some stages of life, and age-specific non-radiogenic competing risks.

  1. A dosimetric comparison of two multileaf collimator designs.

    PubMed

    Killoran, J H; Giraud, J Y; Chin, L

    2002-08-01

    We present the results of measurements designed to compare two different multileaf collimator (MLC) designs using a novel evaluation technique. The MLC designs evaluated were: a "single-focused" MLC (SF-MLC) mounted below the jaws, and a "double-focused" MLC, which is a complete replacement for the lower jaws. The ability of each MLC to conform isodose lines to a prescribed field edge (PFE) was evaluated using film dosimetry. Circular fields, centered on axis and off axis, were used because they produce a range of "angles of approach" between the MLC leaves and the PFE. They also have the advantage that for an ideal field shaping system the resulting isodoses are concentric perfect circles, a well-defined basis for evaluation. The amplitude of the oscillations of the 50% isodose line about the PFE and the penumbra width as determined by the 20%, 80%, and 90% isodose lines was examined. We observe that the 50% isodose line oscillates around the PFE with greater amplitude for SF-MLC. We attribute this, at least in part, to the rounded ends of the SF-MLC leaves. However, the SF-MLC has a noticeably sharper penumbra, which we attribute to its position further from the source. We conclude that these results are relevant for accurate dosimetric modeling of these devices. PMID:12201422

  2. Dosimetric Study of a Low-Dose-Rate Brachytherapy Source

    NASA Astrophysics Data System (ADS)

    Rodríguez-Villafuerte, M.; Arzamendi, S.; Díaz-Perches, R.

    Carcinoma of the cervix is the most common malignancy - in terms of both incidence and mortality - in Mexican women. Low dose rate (LDR) intracavitary brachytherapy is normally prescribed for the treatment of this disease to the vast majority of patients attending public hospitals in our country. However, most treatment planning systems being used in these hospitals still rely on Sievert integral dose calculations. Moreover, experimental verification of dose distributions are hardly ever done. In this work we present a dosimetric characterisation of the Amersham CDCS-J 137Cs source, an LDR brachytherapy source commonly used in Mexican hospitals. To this end a Monte Carlo simulation was developed, that includes a realistic description of the internal structure of the source embedded in a scattering medium. The Monte Carlo results were compared to experimental measurements of dose distributions. A lucite phantom with the same geometric characteristics as the one used in the simulation was built. Dose measurements were performed using thermoluminescent dosimeters together with commercial RadioChromic dye film. A comparison between our Monte Carlo simulation, the experimental data, and results reported in the literature is presented.

  3. Optically stimulated luminescence: Searching for new dosimetric materials

    NASA Astrophysics Data System (ADS)

    Yoshimura, E. M.; Yukihara, E. G.

    2006-09-01

    Optically stimulated luminescence (OSL) is increasingly being used as a dosimetric technique in various fields such as medical, environmental and space dosimetry, and sediment and archaeological dating. Nevertheless few compounds are suitable as OSL materials. In this work, a survey was made of various insulators, searching for candidates for new OSL dosimeters. Natural and synthetic crystals and glasses from numerous sources are included. Luminescence was stimulated with blue LEDs (470 nm) and with IR laser (830 nm) provided by an automatic reader. Irradiation was performed with a 90Sr/ 90Y beta source, and the emitted light was measured with a photomultiplier tube, protected with suitable optical filters. Thermoluminescence (TL) of the samples was also measured, with the same equipment, to evaluate the thermal and optical stability of the defects related to OSL and TL. Among the various investigated materials, Al 2O 3:Cr, Mg, Fe, MgAl 2O 4 spinels, Mg 2SiO 4:Tb, and natural fluorite show potential as OSL dosimeters. Some materials, as barium aluminoborate glasses, although showing intense OSL signals, present a high fading at room temperature. In that situation the OSL signal is related to low temperature TL peaks that also fade at room temperature. None of the investigated materials was specially prepared to be used as an OSL dosimeter, which means that work can be done, mainly in the impurity nature and content, in order to improve OSL signals and to overcome some of the shortcomings that were noticed.

  4. Dosimetric implications of new compounds for neutron capture therapy (NCT)

    SciTech Connect

    Fairchild, R.G.

    1982-01-01

    Systemic application of radiolabeled or cytotoxic agents should allow targeting of primary and metastatic neoplasms on a cellular level. In fact, drug uptake in non-target cell pools often exceeds toxic levels before sufficient amounts are delivered to tumor. In addition, at the large concentration of molecules necessary for therapy, effects of saturation are often found. Application of NCT can circumvent problems associated with high uptake in competing non-target cell pools, as the /sup 10/B(n,..cap alpha..)/sup 7/Li reaction is activated only within the radiation field. A comparison with other modes of particle therapy indicated that NCT provides significant advantages. It is however, difficult to obtain vehicles for boron transport which demonstrate both the tumor specificity and concentration requisite for NCT. A number of biomolecules have been investigated which show both the necessary concentration and specificity. These include chlorpromazine, thiouracil, porphyrins, amino acids, and nucleosides. However, these analogs have yet to be made available for NCT. Dosimetric implications of binding sites are considered, as well as alternate neutron sources. (ERB)

  5. Monte Carlo simulations and dosimetric studies of an irradiation facility

    NASA Astrophysics Data System (ADS)

    Belchior, A.; Botelho, M. L.; Vaz, P.

    2007-09-01

    There is an increasing utilization of ionizing radiation for industrial applications. Additionally, the radiation technology offers a variety of advantages in areas, such as sterilization and food preservation. For these applications, dosimetric tests are of crucial importance in order to assess the dose distribution throughout the sample being irradiated. The use of Monte Carlo methods and computational tools in support of the assessment of the dose distributions in irradiation facilities can prove to be economically effective, representing savings in the utilization of dosemeters, among other benefits. One of the purposes of this study is the development of a Monte Carlo simulation, using a state-of-the-art computational tool—MCNPX—in order to determine the dose distribution inside an irradiation facility of Cobalt 60. This irradiation facility is currently in operation at the ITN campus and will feature an automation and robotics component, which will allow its remote utilization by an external user, under REEQ/996/BIO/2005 project. The detailed geometrical description of the irradiation facility has been implemented in MCNPX, which features an accurate and full simulation of the electron-photon processes involved. The validation of the simulation results obtained was performed by chemical dosimetry methods, namely a Fricke solution. The Fricke dosimeter is a standard dosimeter and is widely used in radiation processing for calibration purposes.

  6. Dosimetric implications of age related glandular changes in screening mammography

    NASA Astrophysics Data System (ADS)

    Beckett, J. R.; Kotre, C. J.

    2000-03-01

    The UK National Health Service Breast Screening Programme is currently organized to routinely screen women between the ages of 50 and 64, with screening for older women available on request. The lower end of this age range closely matches the median age for the menopause (51 years), during which significant changes in the composition of the breast are known to occur. In order to quantify the dosimetric effect of these changes, radiographic factors and compressed breast thickness data for a cohort of 1258 women aged between 35 and 79 undergoing breast screening mammography have been used to derive estimates of breast glandularity and mean glandular dose (MGD), and examine their variation with age. The variation of mean radiographic exposure factors with age is also investigated. The presence of a significant number of age trial women within the cohort allowed an extended age range to be studied. Estimates of MGD including corrections for breast glandularity based on compressed breast thickness only, compressed breast thickness and age and for each individual woman are compared with the MGD based on the conventional assumption of a 50:50 adipose/glandular composition. It has been found that the use of the conventional 50:50 assumption leads to overestimates of MGD of up to 13% over the age range considered. By using compressed breast thickness to estimate breast glandularity, this error range can be reduced to 8%, whilst age and compressed breast thickness based glandularity estimates result in an error range of 1%.

  7. Dosimetric variability of the rats' exposure to electromagnetic pulses.

    PubMed

    Li, Congsheng; Yang, Lei; Li, Chung-huan; Xie, Yi; Wu, Tongning

    2015-01-01

    Rats' exposure to electromagnetic pulses (EMPs) has been conducted using an EMP simulator for various biological endpoints. In contrast, information about the EMP energy distribution and its variability in rats is lacking. EMPs are signals with spectrum concentrating in several hundred MHz, leading to EM absorption patterns different from those obtained at high frequencies. In this study, two anatomical models of rats (a male and a female) were reconstructed from magnetic resonance imaging. The models had the same posture as in the exposure experiments. Realistic EMPs were acquired directly from the EMP simulator and applied to the simulations. The interaction of the EMP with the rat was analyzed through the finite-difference time-domain method. Two approaches were utilized to calculate the energy absorption at the tissue and whole-body levels. Dosimetric variability due to incident directions, polarizations, exposure signals simplification, and rat separation was evaluated in this study. The variability result differed substantially from that of the non-constrained rats' exposure experiments. The result sensitivity to frequency and amplitude was discussed as well. The work can be used as a basis to determine the uncertainty and to formulate a standard experimental protocol for this type of experiment.

  8. Planetary maps

    USGS Publications Warehouse

    ,

    1992-01-01

    An important goal of the USGS planetary mapping program is to systematically map the geology of the Moon, Mars, Venus, and Mercury, and the satellites of the outer planets. These geologic maps are published in the USGS Miscellaneous Investigations (I) Series. Planetary maps on sale at the USGS include shaded-relief maps, topographic maps, geologic maps, and controlled photomosaics. Controlled photomosaics are assembled from two or more photographs or images using a network of points of known latitude and longitude. The images used for most of these planetary maps are electronic images, obtained from orbiting television cameras, various optical-mechanical systems. Photographic film was only used to map Earth's Moon.

  9. Toward optimizing patient-specific IMRT QA techniques in the accurate detection of dosimetrically acceptable and unacceptable patient plans

    SciTech Connect

    McKenzie, Elizabeth M.; Balter, Peter A.; Stingo, Francesco C.; Jones, Jimmy; Followill, David S.; Kry, Stephen F.

    2014-12-15

    was no significant difference in the performance of any device between gamma criteria of 2%/2 mm, 3%/3 mm, and 5%/3 mm. Finally, optimal cutoffs (e.g., percent of pixels passing gamma) were determined for each device and while clinical practice commonly uses a threshold of 90% of pixels passing for most cases, these results showed variability in the optimal cutoff among devices. Conclusions: IMRT QA devices have differences in their ability to accurately detect dosimetrically acceptable and unacceptable plans. Field-by-field analysis with a MapCheck device and use of the MapCheck with a MapPhan phantom while delivering at planned rotational gantry angles resulted in a significantly poorer ability to accurately sort acceptable and unacceptable plans compared with the other techniques examined. Patient-specific IMRT QA techniques in general should be thoroughly evaluated for their ability to correctly differentiate acceptable and unacceptable plans. Additionally, optimal agreement thresholds should be identified and used as common clinical thresholds typically worked very poorly to identify unacceptable plans.

  10. 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.

  11. Comparing the dosimetric characteristics of the electron beam from dedicated intraoperative and conventional radiotherapy accelerators.

    PubMed

    Baghani, Hamid Reza; Aghamiri, Seyed Mahmoud Reza; Mahdavi, Seyed Rabi; Akbari, Mohammad Esmail; Mirzaei, Hamid Reza

    2015-01-01

    The specific design of the mobile dedicated intraoperative radiotherapy (IORT) accelerators and different electron beam collimation system can change the dosimetric characteristics of electron beam with respect to the conventional accelerators. The aim of this study is to measure and compare the dosimetric characteristics of electron beam produced by intraoperative and conventional radiotherapy accelerators. To this end, percentage depth dose along clinical axis (PDD), transverse dose profile (TDP), and output factor of LIAC IORT and Varian 2100C/D conventional radiotherapy accelerators were measured and compared. TDPs were recorded at depth of maximum dose. The results of this work showed that depths of maximum dose, R90, R50, and RP for LIAC beam are lower than those of Varian beam. Furthermore, for all energies, surface doses related to the LIAC beam are substantially higher than those of Varian beam. The symmetry and flatness of LIAC beam profiles are more desirable compared to the Varian ones. Contrary to Varian accelerator, output factor of LIAC beam substantially increases with a decrease in the size of the applicator. Dosimetric characteristics of beveled IORT applicators along clinical axis were different from those of the flat ones. From these results, it can be concluded that dosimetric characteristics of intraoperative electron beam are substantially different from those of conventional clinical electron beam. The dosimetric characteristics of the LIAC electron beam make it a useful tool for intraoperative radiotherapy purposes.

  12. Spatial variation of dosimetric leaf gap and its impact on dose delivery

    SciTech Connect

    Kumaraswamy, Lalith K.; Schmitt, Jonathan D.; Bailey, Daniel W.; Xu, Zheng Zheng; Podgorsak, Matthew B.

    2014-11-01

    Purpose: During dose calculation, the Eclipse treatment planning system (TPS) retracts the multileaf collimator (MLC) leaf positions by half of the dosimetric leaf gap (DLG) value (measured at central axis) for all leaf positions in a dynamic MLC plan to accurately model the rounded leaf ends. The aim of this study is to map the variation of DLG along the travel path of each MLC leaf pair and quantify how this variation impacts delivered dose. Methods: 6 MV DLG values were measured for all MLC leaf pairs in increments of 1.0 cm (from the line intersecting the CAX and perpendicular to MLC motion) to 13.0 cm off axis distance at dmax. The measurements were performed on two Varian linear accelerators, both employing the Millennium 120-leaf MLCs. The measurements were performed at several locations in the beam with both a Sun Nuclear MapCHECK device and a PTW pinpoint ion chamber. Results: The measured DLGs for the middle 40 MLC leaf pairs (each 0.5 cm width) at positions along a line through the CAX and perpendicular to MLC leaf travel direction were very similar, varying maximally by only 0.2 mm. The outer 20 MLC leaf pairs (each 1.0 cm width) have much lower DLG values, about 0.3–0.5 mm lower than the central MLC leaf pair, at their respective central line position. Overall, the mean and the maximum variation between the 0.5 cm width leaves and the 1.0 cm width leaf pairs are 0.32 and 0.65 mm, respectively. Conclusions: The spatial variation in DLG is caused by the variation of intraleaf transmission through MLC leaves. Fluences centered on the CAX would not be affected since DLG does not vary; but any fluences residing significantly off axis with narrow sweeping leaves may exhibit significant dose differences. This is due to the fact that there are differences in DLG between the true DLG exhibited by the 1.0 cm width outer leaves and the constant DLG value utilized by the TPS for dose calculation. Since there are large differences in DLG between the 0.5 cm width

  13. Map accuracy

    USGS Publications Warehouse

    ,

    1981-01-01

    An inaccurate map is not a reliable map. "X" may mark the spot where the treasure is buried, but unless the seeker can locate "X" in relation to known landmarks or positions, the map is not very useful.

  14. SU-E-J-228: MRI-Based Planning: Dosimetric Feasibility of Dose Painting for ADCDefined Intra-Prostatic Tumor

    SciTech Connect

    Chen, X; Dalah, E; Prior, P; Lawton, C; Li, X

    2015-06-15

    Purpose: Apparent diffusion coefficient (ADC) map may help to delineate the gross tumor volume (GTV) in prostate gland. Dose painting with external beam radiotherapy for GTV might increase the local tumor control. The purpose of this study is to explore the maximum boosting dose on GTV using VMAT without sacrificing sparing of organs at risk (OARs) in MRI based planning. Methods: VMAT plans for 5 prostate patients were generated following the commonly used dose volume (DV) criteria based on structures contoured on T2 weighted MRI with bulk electron density assignment using electron densities derived from ICRU46. GTV for each patient was manually delineated based on ADC maps and fused to T2-weighted image set for planning study. A research planning system with Monte Carlo dose engine (Monaco, Elekta) was used to generate the VMAT plans with boosting dose on GTV gradually increased from 85Gy to 100Gy. DV parameters, including V(boosting-dose) (volume covered by boosting dose) for GTV, V75.6Gy for PTV, V45Gy, V70Gy, V72Gy and D1cc (Maximum dose to 1cc volume) for rectum and bladder, were used to measure plan quality. Results: All cases achieve at least 99.0% coverage of V(boosting-dose) on GTV and 95% coverage of V75.6Gy to the PTV. All the DV criteria, V45Gy≤50% and V70Gy≤15% for bladder and rectum, D1cc ≤77Gy (Rectum) and ≤80Gy (Bladder), V72Gy≤5% (rectum and bladder) were maintained when boosting GTV to 95Gy for all cases studied. Except for two patients, all the criteria were also met when the boosting dose goes to 100Gy. Conclusion: It is dosimetrically feasible safe to boost the dose to at least 95Gy to ADC defined GTV in prostate cancer using MRI guided VMAT delivery. Conclusion: It is dosimetrically feasible safe to boost the dose to at least 95Gy to ADC defined GTV in prostate cancer using MRI guided VMAT delivery. This research is partially supported by Elekta Inc.

  15. A computational method for estimating the dosimetric effect of intra-fraction motion on step-and-shoot IMRT and compensator plans.

    PubMed

    Waghorn, Ben J; Shah, Amish P; Ngwa, Wilfred; Meeks, Sanford L; Moore, Joseph A; Siebers, Jeffrey V; Langen, Katja M

    2010-07-21

    Intra-fraction organ motion during intensity-modulated radiation therapy (IMRT) treatment can cause differences between the planned and the delivered dose distribution. To investigate the extent of these dosimetric changes, a computational model was developed and validated. The computational method allows for calculation of the rigid motion perturbed three-dimensional dose distribution in the CT volume and therefore a dose volume histogram-based assessment of the dosimetric impact of intra-fraction motion on a rigidly moving body. The method was developed and validated for both step-and-shoot IMRT and solid compensator IMRT treatment plans. For each segment (or beam), fluence maps were exported from the treatment planning system. Fluence maps were shifted according to the target position deduced from a motion track. These shifted, motion-encoded fluence maps were then re-imported into the treatment planning system and were used to calculate the motion-encoded dose distribution. To validate the accuracy of the motion-encoded dose distribution the treatment plan was delivered to a moving cylindrical phantom using a programmed four-dimensional motion phantom. Extended dose response (EDR-2) film was used to measure a planar dose distribution for comparison with the calculated motion-encoded distribution using a gamma index analysis (3% dose difference, 3 mm distance-to-agreement). A series of motion tracks incorporating both inter-beam step-function shifts and continuous sinusoidal motion were tested. The method was shown to accurately predict the film's dose distribution for all of the tested motion tracks, both for the step-and-shoot IMRT and compensator plans. The average gamma analysis pass rate for the measured dose distribution with respect to the calculated motion-encoded distribution was 98.3 +/- 0.7%. For static delivery the average film-to-calculation pass rate was 98.7 +/- 0.2%. In summary, a computational technique has been developed to calculate the

  16. Transport and dosimetric solutions for the ELIMED laser-driven beam line

    NASA Astrophysics Data System (ADS)

    Cirrone, G. A. P.; Romano, F.; Scuderi, V.; Amato, A.; Candiano, G.; Cuttone, G.; Giove, D.; Korn, G.; Krasa, J.; Leanza, R.; Manna, R.; Maggiore, M.; Marchese, V.; Margarone, D.; Milluzzo, G.; Petringa, G.; Sabini, M. G.; Schillaci, F.; Tramontana, A.; Valastro, L.; Velyhan, A.

    2015-10-01

    Within 2017, the ELIMED (ELI-Beamlines MEDical applications) transport beam-line and dosimetric systems for laser-generated beams will be installed at the ELI-Beamlines facility in Prague (CZ), inside the ELIMAIA (ELI Multidisciplinary Applications of laser-Ion Acceleration) interaction room. The beam-line will be composed of two sections: one in vacuum, devoted to the collecting, focusing and energy selection of the primary beam and the second in air, where the ELIMED beam-line dosimetric devices will be located. This paper briefly describes the transport solutions that will be adopted together with the main dosimetric approaches. In particular, the description of an innovative Faraday Cup detector with its preliminary experimental tests will be reported.

  17. Optimisation of internal radiation dose assessment on uncertain dosimetric parameters in interpretation of bioassay results.

    PubMed

    Lee, Jongil; Lee, Jaiki; Chang, Siyoung; Kim, Janglyul

    2013-07-01

    Estimates of the committed effective dose (E50) from an intake of a radionuclide strongly depends on several dosimetric parameters such as the intake pathway, f1 value, the absorption type, activity median aerodynamic diameter and the time after an intake. A misuse of the dosimetric parameters can result in a significant error in the evaluated value of a committed effective dose. In order to reduce the potential error and to get optimised values of E50, better bioassay methods and better (or worse) bioassay measurement times due to the uncertain dosimetric parameters were suggested for the various radionuclides, including (57)Co, (58)Co, (60)Co, (131)I, (134)Cs, (137)Cs, (89)Sr, (90)Sr, (32)P and (235)U. This strategy was applied for the case of multiple unknown parameters as well as a single unknown parameter and provided the committed effective doses with the least potential error.

  18. Dosimetric monitoring in Ukraine--present status and path to the future.

    PubMed

    Chumak, V; Boguslavskaya, A

    2007-01-01

    Despite wide use of nuclear energy and radiation sources in industry and medicine, there is no centralised dose accounting system in Ukraine; existing dosimetry services operate obsolete manual thermoluminescence dosemeter (TLD) readers and do not meet modern proficiency standards. Currently, dosimetric monitoring is required for approximately 42,000 occupationally exposed workers, including 9100 in medicine, 17,000 employees of nuclear power plants and approximately 16,000 workers dealing with other sources of occupational exposure. This article presents the plan of elaboration of the United System for monitoring and registration of individual doses which has the aim of harmonisation of individual monitoring in Ukraine through securing methodical unity; scientific and methodological guidance of individual dosimetric control; procurement of common technical policy regarding nomenclature and operation of instrumentation; implementation of quality assurance programmes; development and support of information infrastructure, in particular operation of the national registry of individual doses; training and certification of personnel engaged in the system of individual dosimetric monitoring.

  19. 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.

  20. Dosimetric Parameters in Partial Breast Irradiation Through Brachytherapy

    SciTech Connect

    Gloi, Aime McCourt, Steve; Buchanan, Robert; Goetller, Andrea; Zuge, Corrie; Balzoa, Paula; Cooley, Greg

    2009-10-01

    The objective of this work is to evaluate biological models and dose homogeneity in a new partial breast irradiation method, the MammoSite RTS. The study is based on 11 patients who received the therapy. For each patient, we determined the dose volume distribution delivered to the breast. Based on these data, we estimate some important biological parameters. Eleven patients with early-stage, invasive, ductal breast cancer were treated using MammoSite RTS brachytherapy, which delivers radiation through a balloon placed in the lumpectomy bed. The radiation was provided by an Iridium-192 source, and 340 cGy were delivered per fraction twice daily. We calculated some commonly used dosimetric parameters, and evaluated the biological parameters tumor control probability (TCP) and normal tissue complication probability (NTCP). We also looked for correlations among these parameters. The average equivalent uniform dose (EUD), NTCP, and TCP were 43.66 Gy, 47.95%, and 91.78%, respectively. The coefficient of variation (CV) among the patients was very low for all 3 parameters. Two dose homogeneity indices (DHI and the S-index) are strongly correlated (r = -0.815). The area under the dose-volume histogram (DVH) and the treatment volume (TXV) also showed a strong correlation (r = 0.995, p < 0.0001). A simplified logit Poisson-EUD model is suitable for determining NTCP and TCP. Other factors such as the area under the DVH and dose homogeneity indices are also useful in planning radiotherapy treatments for early breast cancer.

  1. Dosimetric properties of the Theraview fluoroscopic electronic portal imaging device.

    PubMed

    Glendinning, A G; Bonnett, D E

    2000-05-01

    Electronic portal imaging devices (EPIDs) can be used for non-imaging applications in radiotherapy such as patient dosimetry. Of the systems available, the fluoroscopic camera-based EPID Theraview (InfiMed Inc.) has not been studied to date, and a review of the dosimetric properties of the system is presented here. In the "single set-up" mode of image acquisition, pixel intensity increases sublinearly with applied dose. The response was dependent on the system's video signal gain and showed a threshold dose to the detector in the range 0.05-0.35 cGy, and pixel saturation at detector doses in the range 1.2-1.6 cGy. Repeated exposures of the EPID were observed to be extremely reproducible (standard deviation 0.5%). The sensitivity of the system showed a linear decline of 0.04% day-1 over a 68-day period, during which time the relative off-axis response within 10 x 10 cm2 field was constant to within a standard deviation of 0.56%. The system shows spatial non-uniformity, which requires correction for application to dose measurements in two-dimensions. Warm-up of the camera control unit required a period of at least 40 min and was associated with an enhancement in pixel intensity of up to 12%. A radiation dose history effect was observed at doses as low as 0.2 Gy. Camera dark current was shown to be negligible at normal accelerator operation. No discernible image distortion was found. Mechanical stability on gantry rotation was also assessed and image displacement of up to 5 mm at the isocentre was observed. It was concluded that the device could be used for dosimetry provided necessary precautions were observed and corrections made. PMID:10884749

  2. System for integrated interstitial photodynamic therapy and dosimetric monitoring

    NASA Astrophysics Data System (ADS)

    Johansson, Ann; Soto Thompson, Marcelo; Johansson, Thomas; Bendsoe, Niels; Svanberg, Katarina; Svanberg, Sune; Andersson-Engels, Stefan

    2005-04-01

    Photodynamic therapy for the treatment of cancer relies on the presence of light, sensitizer and oxygen. By monitoring these three parameters during the treatment a better understanding and treatment control could possibly be achieved. Here we present data from in vivo treatments of solid skin tumors using an instrument for interstitial photodynamic therapy with integrated dosimetric monitoring. By using intra-tumoral ALA-administration and interstitial light delivery solid tumors are targeted. The same fibers are used for measuring the fluence rate at the treatment wavelength, the sensitizer fluorescence and the local blood oxygen saturation during the treatment. The data presented is based on 10 treatments in 8 patients with thick basal cell carcinomas. The fluence rate measurements at 635 nm indicate a major treatment induced absorption increase, leading to a limited light penetration at the treatment wavelength. This leads to a far from optimal treatment since the absorption increase prevents peripheral tumor regions from being fully treated. An interactive treatment has been implemented assisting the physician in delivering the correct light dose. The absorption increase can be compensated for by either prolonging the treatment time or increasing the output power of each individual treatment fiber. The other parameters of importance, i.e. the sensitizer fluorescence at 705 nm and the local blood oxygen saturation, are monitored in order to get an estimate of the amount of photobleaching and oxygen consumption. Based on the oxygen saturation signal, a fractionized irradiation can be introduced in order to allow for a re-oxygenation of the tissue.

  3. Dosimetric Analysis of Radiation-Induced Gastric Bleeding

    PubMed Central

    Feng, Mary; Normolle, Daniel; Pan, Charlie C.; Dawson, Laura A.; Amarnath, Sudha; Ensminger, William D.; Lawrence, Theodore S.; Ten Haken, Randall K.

    2012-01-01

    Purpose Radiation-induced gastric bleeding has been poorly understood. In this study, we describe dosimetric predictors for gastric bleeding after fractionated radiotherapy and compare several predictive models. Materials & Methods The records of 139 sequential patients treated with 3-dimensional conformal radiotherapy (3D-CRT) for intrahepatic malignancies between January 1999 and April 2002 were reviewed. Median follow-up was 7.4 months. Logistic regression and Lyman normal tissue complication probability (NTCP) models for the occurrence of ≥ grade 3 gastric bleed were fit to the data. The principle of maximum likelihood was used to estimate parameters for all models. Results Sixteen of 116 evaluable patients (14%) developed gastric bleeds, at a median time of 4.0 months (mean 6.5 months, range 2.1–28.3 months) following completion of RT. The median and mean of the maximum doses to the stomach were 61 and 63 Gy (range 46 Gy–86 Gy), respectively, after bio-correction to equivalent 2 Gy daily fractions. The Lyman NTCP model with parameters adjusted for cirrhosis was most predictive of gastric bleed (AUROC=0.92). Best fit Lyman NTCP model parameters were n =0.10, and m =0.21, with TD50(normal) =56 Gy and TD50(cirrhosis) = 22 Gy. The low n value is consistent with the importance of maximum dose; a lower TD50 value for the cirrhosis patients points out their greater sensitivity. Conclusion This study demonstrates that the Lyman NTCP model has utility for predicting gastric bleeding, and that the presence of cirrhosis greatly increases this risk. These findings should facilitate the design of future clinical trials involving high-dose upper abdominal radiation. PMID:22541965

  4. Dosimetric Analysis of Radiation-induced Gastric Bleeding

    SciTech Connect

    Feng, Mary; Normolle, Daniel; Pan, Charlie C.; Dawson, Laura A.; Amarnath, Sudha; Ensminger, William D.; Lawrence, Theodore S.; Ten Haken, Randall K.

    2012-09-01

    Purpose: Radiation-induced gastric bleeding has been poorly understood. In this study, we described dosimetric predictors for gastric bleeding after fractionated radiation therapy. Methods and Materials: The records of 139 sequential patients treated with 3-dimensional conformal radiation therapy (3D-CRT) for intrahepatic malignancies were reviewed. Median follow-up was 7.4 months. The parameters of a Lyman normal tissue complication probability (NTCP) model for the occurrence of {>=}grade 3 gastric bleed, adjusted for cirrhosis, were fitted to the data. The principle of maximum likelihood was used to estimate parameters for NTCP models. Results: Sixteen of 116 evaluable patients (14%) developed gastric bleeds at a median time of 4.0 months (mean, 6.5 months; range, 2.1-28.3 months) following completion of RT. The median and mean maximum doses to the stomach were 61 and 63 Gy (range, 46-86 Gy), respectively, after biocorrection of each part of the 3D dose distributions to equivalent 2-Gy daily fractions. The Lyman NTCP model with parameters adjusted for cirrhosis predicted gastric bleed. Best-fit Lyman NTCP model parameters were n=0.10 and m=0.21 and with TD{sub 50} (normal) = 56 Gy and TD{sub 50} (cirrhosis) = 22 Gy. The low n value is consistent with the importance of maximum dose; a lower TD{sub 50} value for the cirrhosis patients points out their greater sensitivity. Conclusions: This study demonstrates that the Lyman NTCP model has utility for predicting gastric bleeding and that the presence of cirrhosis greatly increases this risk. These findings should facilitate the design of future clinical trials involving high-dose upper abdominal radiation.

  5. A revised dosimetric model of the adult head and brain

    SciTech Connect

    Bouchet, L.G.; Bolch, W.E.; Weber, D.A.

    1996-06-01

    During the last decade, new radiopharmaceutical have been introduced for brain imaging. The marked differences of these tracers in tissue specificity within the brain and their increasing use for diagnostic studies support the need for a more anthropomorphic model of the human brain and head. Brain and head models developed in the past have been only simplistic representations of this anatomic region. For example, the brain within the phantom of MIRD Pamphlet No. 5 Revised is modeled simply as a single ellipsoid of tissue With no differentiation of its internal structures. To address this need, the MIRD Committee established a Task Group in 1992 to construct a more detailed brain model to include the cerebral cortex, the white matter, the cerebellum, the thalamus, the caudate nucleus, the lentiform nucleus, the cerebral spinal fluid, the lateral ventricles, and the third ventricle. This brain model has been included within a slightly modified version of the head model developed by Poston et al. in 1984. This model has been incorporated into the radiation transport code EGS4 so as to calculate photon and electron absorbed fractions in the energy range 10 keV to 4 MeV for each of thirteen sources in the brain. Furthermore, explicit positron transport have been considered, separating the contribution by the positron itself and its associated annihilations photons. No differences are found between the electron and positron absorbed fractions; however, for initial energies of positrons greater than {approximately}0.5 MeV, significant differences are found between absorbed fractions from explicit transport of annihilation photons and those from an assumed uniform distribution of 0.511-MeV photons. Subsequently, S values were calculated for a variety of beta-particle and positron emitters brain imaging agents. Moreover, pediatric head and brain dosimetric models are currently being developed based on this adult head model.

  6. A new fully integrated X-ray irradiator system for dosimetric research.

    PubMed

    Richter, D; Mittelstraß, D; Kreutzer, S; Pintaske, R; Dornich, K; Fuchs, M

    2016-06-01

    A fully housed X-ray irradiator was developed for use within lexsyg or Magnettech desktop equipment. The importance of hardening of the low energy photon radiation is discussed, its performance and feasibility is empirically shown and sustained by basic numerical simulations. Results of the latter for various materials are given for different X-ray source settings in order to provide estimates on the required setup for the irradiation of different geometries and materials. A Si-photodiode provides real-time monitoring of the X-ray-irradiator designed for use in dosimetric dating and other dosimetric application where irradiation of small samples or dosemeters is required. PMID:27041090

  7. Exploring maps

    USGS Publications Warehouse

    ,

    1993-01-01

    Exploring Maps is an interdisciplinary set of materials on mapping for grades 7-12. Students will learn basic mapmaking and map reading skills and will see how maps can answer fundamental geographic questions: "Where am I?" "What else is here?" "Where am I going?"

  8. Contour Mapping

    NASA Technical Reports Server (NTRS)

    1995-01-01

    In the early 1990s, the Ohio State University Center for Mapping, a NASA Center for the Commercial Development of Space (CCDS), developed a system for mobile mapping called the GPSVan. While driving, the users can map an area from the sophisticated mapping van equipped with satellite signal receivers, video cameras and computer systems for collecting and storing mapping data. George J. Igel and Company and the Ohio State University Center for Mapping advanced the technology for use in determining the contours of a construction site. The new system reduces the time required for mapping and staking, and can monitor the amount of soil moved.

  9. Dosimetric characteristics of a PIN diode for radiotherapy application.

    PubMed

    Kumar, R; Sharma, S D; Philomina, A; Topkar, A

    2014-08-01

    The PIN diode developed by Bhabha Atomic Research Centre (BARC) was modified for its use as a dosimeter in radiation therapy. For this purpose the diode was mounted on a printed circuit board (PCB) and provided with necessary connections so that its response against irradiation can be recorded by a standard radiotherapy electrometer. The dosimetric characteristics of the diode were studied in Co-60 gamma rays as well as high energy X-rays. The measured sensitivity of this PIN diode is 4 nC/cGy which is about ten times higher than some commercial diode dosimeters. The leakage current from the diode is 0.04 nA. The response of the PIN diode is linear in the range of 20-1000 cGy which covers the full range of radiation dose encountered in radiotherapy treatments. The non-linearity of the diode response is 3.5% at 20 cGy and it is less than 1.5% at higher dose values. Its repeatability is within 0.5%. The angular response variation is about 5.6% within 6608 with respect to normal beam incidence. The response of the PIN diode at 6 and 18 MV X-rays varies within 2% with respect to its response at Co-60 gamma rays. The source to surface distance (SSD) dependence of the PIN diode was studied for Co-60 beam. It was found that the response of the diode decreases almost linearly relative to given dose for beams with constant collimator setting but increasing SSD (decreasing dose-rate). Within this study the diode response varied by about 2.5% between the maximum and minimum SSD. The dose-rate dependence of the PIN diode for 6 and 15 MV-rays was studied. The variation in response of diode for both energies in the studied dose range is less than 1%. The field size dependence of the PIN diode response is within 1% with respect to the response of ionisation chamber. These studies indicate that the characteristics of the PIN diode are suitable for use in radiotherapy dosimetry.

  10. Dosimetric measurements of Onyx embolization material for stereotactic radiosurgery

    SciTech Connect

    Roberts, Donald A.; Balter, James M.; Chaudhary, Neeraj; Gemmete, Joseph J.; Pandey, Aditya S.

    2012-11-15

    Purpose: Arteriovenous malformations are often treated with a combination of embolization and stereotactic radiosurgery. Concern has been expressed in the past regarding the dosimetric properties of materials used in embolization and the effects that the introduction of these materials into the brain may have on the quality of the radiosurgery plan. To quantify these effects, the authors have taken large volumes of Onyx 34 and Onyx 18 (ethylene-vinyl alcohol copolymer doped with tantalum) and measured the attenuation and interface effects of these embolization materials. Methods: The manufacturer provided large cured volumes ({approx}28 cc) of both Onyx materials. These samples were 8.5 cm in diameter with a nominal thickness of 5 mm. The samples were placed on a block tray above a stack of solid water with an Attix chamber at a depth of 5 cm within the stack. The Attix chamber was used to measure the attenuation. These measurements were made for both 6 and 16 MV beams. Placing the sample directly on the solid water stack and varying the thickness of solid water between the sample and the Attix chamber measured the interface effects. The computed tomography (CT) numbers for bulk material were measured in a phantom using a wide bore CT scanner. Results: The transmission through the Onyx materials relative to solid water was approximately 98% and 97% for 16 and 6 MV beams, respectively. The interface effect shows an enhancement of approximately 2% and 1% downstream for 16 and 6 MV beams. CT numbers of approximately 2600-3000 were measured for both materials, which corresponded to an apparent relative electron density (RED) {rho}{sub e}{sup w} to water of approximately 2.7-2.9 if calculated from the commissioning data of the CT scanner. Conclusions: We performed direct measurements of attenuation and interface effects of Onyx 34 and Onyx 18 embolization materials with large samples. The introduction of embolization materials affects the dose distribution of a MV

  11. Dosimetric characteristics of a new unit for electronic skin brachytherapy

    PubMed Central

    Garcia-Martinez, Teresa; Chan, Jan-Pieter; Perez-Calatayud, Jose

    2014-01-01

    Purpose Brachytherapy with radioactive high dose rate (HDR) 192Ir source is applied to small skin cancer lesions, using surface applicators, i.e. Leipzig or Valencia type. New developments in the field of radiotherapy for skin cancer include electronic brachytherapy. This technique involves the placement of an HDR X-ray source close to the skin, therefore combining the benefits of brachytherapy with the reduced shielding requirements and targeted energy of low energy X-rays. Recently, the Esteya® Electronic Brachytherapy System (Esteya EBS, Elekta AB-Nucletron, Stockholm, Sweden) has been developed specifically for HDR brachytherapy treatment of surface lesions. The system provides radionuclide free HDR brachytherapy by means of a small 69.5 kV X-ray source. The purpose of this study is to obtain the dosimetric characterization required for clinical implementation, providing the detailed methodology to perform the commissioning. Material and methods Flatness, symmetry and penumbra, percentage of depth dose (PDD), kV stability, HVL, output, spectrum, linearity, and leakage have been evaluated for a set of applicators (from 10 mm to 30 mm in diameter). Results Flatness and symmetry resulted better than 5% with around 1 mm of penumbra. The depth dose gradient is about 7%/mm. A kV value of 68.4 ± 1.0 kV (k = 1) was obtained, in good agreement with manufacturer data (69.5 kV). HVL was 1.85 mm Al. Dose rate for a typical 6 Gy to 7 Gy prescription resulted about 3.3 Gy/min and the leakage value was < 100 µGy/min. Conclusions The new Esteya® Electronic Brachytherapy System presents excellent flatness and penumbra as with the Valencia applicator case, combined with an improved PDD, allowing treatment of lesions of up to a depth of 5 mm in combination with reduced treatment duration. The Esteya unit allows HDR brachytherapy superficial treatment within a minimally shielded environment due its low energy. PMID:24790622

  12. Dosimetric characteristics of a PIN diode for radiotherapy application.

    PubMed

    Kumar, R; Sharma, S D; Philomina, A; Topkar, A

    2014-08-01

    The PIN diode developed by Bhabha Atomic Research Centre (BARC) was modified for its use as a dosimeter in radiation therapy. For this purpose the diode was mounted on a printed circuit board (PCB) and provided with necessary connections so that its response against irradiation can be recorded by a standard radiotherapy electrometer. The dosimetric characteristics of the diode were studied in Co-60 gamma rays as well as high energy X-rays. The measured sensitivity of this PIN diode is 4 nC/cGy which is about ten times higher than some commercial diode dosimeters. The leakage current from the diode is 0.04 nA. The response of the PIN diode is linear in the range of 20-1000 cGy which covers the full range of radiation dose encountered in radiotherapy treatments. The non-linearity of the diode response is 3.5% at 20 cGy and it is less than 1.5% at higher dose values. Its repeatability is within 0.5%. The angular response variation is about 5.6% within 6608 with respect to normal beam incidence. The response of the PIN diode at 6 and 18 MV X-rays varies within 2% with respect to its response at Co-60 gamma rays. The source to surface distance (SSD) dependence of the PIN diode was studied for Co-60 beam. It was found that the response of the diode decreases almost linearly relative to given dose for beams with constant collimator setting but increasing SSD (decreasing dose-rate). Within this study the diode response varied by about 2.5% between the maximum and minimum SSD. The dose-rate dependence of the PIN diode for 6 and 15 MV-rays was studied. The variation in response of diode for both energies in the studied dose range is less than 1%. The field size dependence of the PIN diode response is within 1% with respect to the response of ionisation chamber. These studies indicate that the characteristics of the PIN diode are suitable for use in radiotherapy dosimetry. PMID:24325130

  13. Evaluation of the applicability of pinpoint ion chambers for SRS dosimetric quality assurance

    NASA Astrophysics Data System (ADS)

    Baek, Jong Geun; Jang, Hyun Soo; Kim, Eng Chan; Lee, Yong Hee; Oh, Young Kee; Kim, Sung Kyu

    2015-06-01

    The aim of the present study was to evaluate the applicability of a Pinpoint ion chamber for the measurement of the absolute dose for dosimetric quality assurance (QA) under the same conditions as are used for actual stereotactic radiosurgery (SRS). A PTW 31014 Pinpoint chamber with a active volume of 0.015 cm3 was used to measure the absolute doses of small beams. The PTW 60003 natural diamond detector was used as a reference dosimeter. A custom-made cylindrical acrylic phantom (15 cm diameter, 15 cm long) was produced to obtain measurements, and a noncoplanar arc plan was devised to deliver a prescription dose (15-25 Gy) to 80% of the maximum dose to the target in a single fraction by using the BrainLAB planning system. All irradiations were performed by using a Varian Clinac IX 6 MV equipped with a micro-multileaf-collimators (m3) designed by BrainLAB. The acceptability criterion used was a dose difference of less than 3%. The diameter of the target volume was considered the standard parameter in the present study and was used to divide the cases into two groups, that is, a ≤ 10 mm target diameter group (10 cases) and a > 10 mm target diameter group (13 cases). For the Pinpoint chamber and target diameters of ≤ 10 mm, dosimetric uncertainties of > 3% were seen in 4 of the 10 cases, and differences ranged widely from 0.7% to 4.85%. On the other hand, for the Pinpoint chamber and target diameters of > 10 mm all dose differences were less than 1.6%, and the mean discrepancy was 0.81%. A highly significant, but moderate, correlation between dosimetric uncertainties and all target diameters was observed for the Pinpoint chamber (R2 = 0.483, p 0.001). This result indicates that Pinpoint chambers exhibit a field-size dependency when used for SRS dosimetric QA. Based on the results of the present study, we conclude that the use of a Pinpoint chamber for verification of SRS dosimetric QA is unsuitable for all field sizes, but that it can be used to verify the

  14. 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.

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

    SciTech Connect

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

    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 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. 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.

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

    SciTech Connect

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

    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.

  17. RICH MAPS

    EPA Science Inventory

    Michael Goodchild recently gave eight reasons why traditional maps are limited as communication devices, and how interactive internet mapping can overcome these limitations. In the past, many authorities in cartography, from Jenks to Bertin, have emphasized the importance of sim...

  18. Map adventures

    USGS Publications Warehouse

    1994-01-01

    Map Adventures, with seven accompanying lessons, is appropriate for grades K-3. Students will learn basic concepts for visualizing objects from different perspectives and how to understand /and use maps.

  19. Historical Mapping

    USGS Publications Warehouse

    ,

    1999-01-01

    Maps become out of date over time. Maps that are out of date, however, can be useful to historians, attorneys, environmentalists, genealogists, and others interested in researching the background of a particular area. Local historians can compare a series of maps of the same area compiled over a long period of time to learn how the area developed. A succession of such maps can provide a vivid picture of how a place changed over time.

  20. A dosimetric comparison of copper and Cerrobend electron inserts.

    PubMed

    Rusk, Benjamin D; Carver, Robert L; Gibbons, John P; Hogstrom, Kenneth R

    2016-01-01

    differences decreased as the SSD increased, with no gamma failures at 110 cm SSD. Inserts for field sizes ≥ 6 × 6 cm2 at any energy, or for small fields (≤ 4 × 4 cm2) at energies < 20 MeV, showed dosimetric differences less than 2%/1 mm for more than 99% of points. All areas of comparison criteria failures were from lower out-of-field dose under copper inserts due to a reduction in bremsstrahlung production, which is clinically beneficial in reducing dose to healthy tissue outside of the planned treatment volume. All field size-applicator size-energy combinations passed 3%/1 mm criteria for 100% of points. Therefore, it should be clinically acceptable to utilize copper insets with dose distributions measured with Cerrobend inserts for treatment planning dose calculations and monitor unit calculations. PMID:27685126

  1. A dosimetric characterization of a novel linear accelerator collimator

    SciTech Connect

    Thompson, C. M.; Weston, S. J. Cosgrove, V. C.; Thwaites, D. I.

    2014-03-15

    Purpose: The aim of this work is to characterize a new linear accelerator collimator which contains a single pair of sculpted diaphragms mounted orthogonally to a 160 leaf multileaf collimator (MLC). The diaphragms have “thick” regions providing full attenuation and “thin” regions where attenuation is provided by both the leaves and the diaphragm. The leaves are mounted on a dynamic leaf guide allowing rapid leaf motion and leaf travel over 350 mm. Methods: Dosimetric characterization, including assessment of leaf transmission, leaf tip transmission, penumbral width, was performed in a plotting tank. Head scatter factor was measured using a mini-phantom and the effect of leaf guide position on output was assessed using a water phantom. The tongue and groove effect was assessed using multiple exposures on radiochromic film. Leaf reproducibility was assessed from portal images of multiple abutting fields. Results: The maximum transmission through the multileaf collimator is 0.44% at 6 MV and 0.52% at 10 MV. This reduced to 0.22% and 0.27%, respectively, when the beam passes through the dynamic leaf guide in addition to the MLC. The maximum transmission through the thick part of the diaphragm is 0.32% and 0.36% at 6 and 10 MV. The combination of leaf and diaphragm transmission ranges from 0.08% to 0.010% at 6 MV and 0.10% to 0.14% depending on whether the shielding is through the thick or thin part of the diaphragm. The off-axis intertip transmission for a zero leaf gap is 2.2% at 6 and 10 MV. The leaf tip penumbra for a 100 × 100 mm field ranges from 5.4 to 4.3 mm at 6 and 10 MV across the full range of leaf motion when measured in the AB direction, which reduces to 4.0–3.4 mm at 6 MV and 4.5–3.8 mm at 10 MV when measured in the GT direction. For a 50 × 50 mm field, the diaphragm penumbra ranges from 4.3 to 3.7 mm at 6 MV and 4.5 to 4.1 mm at 10 MV in the AB direction and 3.7 to 3.2 mm at 6 MV and 4.2 to 3.7 mm when measured in the GT direction. The

  2. Surface and superficial dose dosimetric verification for postmastectomy radiotherapy

    SciTech Connect

    Shiau, An-Cheng; Chiu, Min-Chi; Chen, Tung-Ho; Chiou, Jeng-Fong; Shueng, Pei-Wei; Chen, Shang-Wen; Chen, Wei-Li; Kuan, Wei-Peng

    2012-01-01

    In patients given postmastectomy radiotherapy (PMRT), the chest wall is a very thin layer of soft tissue with a low-density lung tissue behind. Chest wall treated in this situation with a high-energy photon beam presents a high dosimetric uncertainty region for both calculation and measurement. The purpose of this study was to measure and to evaluate the surface and superficial doses for patients requiring PMRT with different treatment techniques. An elliptic cylinder cork and superflab boluses were used to simulate the lung and the chest wall, respectively. Sets of computed tomography (CT) images with different chest wall thicknesses were acquired for the study phantom. Hypothetical clinical target volumes (CTVs) were outlined and modified to fit a margin of 1-3 mm, depending on the chest wall thickness, away from the surface for the sets of CT images. The planning target volume (PTV) was initially created by expanding an isotropic 3-mm margin from the CTV, and then a margin of 3 mm was shrunk from the phantom surface to avoid artifact-driven results in the beam-let intensity. Treatment techniques using a pair of tangential wedged fields (TWFs) and 4-field intensity-modulated radiation therapy (IMRT) were designed with a prescribed fraction dose (D{sub p}) of 180 cGy. Superficial dose profiles around the phantom circumference at depths of 0, 1, 2, 3, and 5 mm were obtained for each treatment technique using radiochromic external beam therapy (EBT) films. EBT film exhibits good characteristics for dose measurements in the buildup region. Underdoses at the median and lateral regions of the TWF plans were shown. The dose profiles at shallow depths for the TWF plans show a dose buildup about 3 mm at the median and lateral tangential incident regions with a surface dose of about 52% of D{sub p}. The dose was gradually increased toward the most obliquely tangential angle with a maximum dose of about 118% of D{sub p.} Dose profiles were more uniform in the PTV region for

  3. Topographic mapping

    USGS Publications Warehouse

    ,

    2008-01-01

    The U.S. Geological Survey (USGS) produced its first topographic map in 1879, the same year it was established. Today, more than 100 years and millions of map copies later, topographic mapping is still a central activity for the USGS. The topographic map remains an indispensable tool for government, science, industry, and leisure. Much has changed since early topographers traveled the unsettled West and carefully plotted the first USGS maps by hand. Advances in survey techniques, instrumentation, and design and printing technologies, as well as the use of aerial photography and satellite data, have dramatically improved mapping coverage, accuracy, and efficiency. Yet cartography, the art and science of mapping, may never before have undergone change more profound than today.

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

    SciTech Connect

    Yang, Yun; Catalano, Suzanne; Kelsey, Chris R.; Yoo, David S.; Yin, Fang-Fang; Cai, Jing

    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} {sub 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.

  5. Will weight loss cause significant dosimetric changes of target volumes and organs at risk in nasopharyngeal carcinoma treated with intensity-modulated radiation therapy?

    SciTech Connect

    Chen, Chuanben; Fei, Zhaodong; Chen, Lisha; Bai, Penggang; Lin, Xiang; Pan, Jianji

    2014-04-01

    This study aimed to quantify dosimetric effects of weight loss for nasopharyngeal carcinoma (NPC) treated with intensity-modulated radiation therapy (IMRT). Overall, 25 patients with NPC treated with IMRT were enrolled. We simulated weight loss during IMRT on the computer. Weight loss model was based on the planning computed tomography (CT) images. The original external contour of head and neck was labeled plan 0, and its volume was regarded as pretreatment normal weight. We shrank the external contour with different margins (2, 3, and 5 mm) and generated new external contours of head and neck. The volumes of reconstructed external contours were regarded as weight during radiotherapy. After recontouring outlines, the initial treatment plan was mapped to the redefined CT scans with the same beam configurations, yielding new plans. The computer model represented a theoretical proportional weight loss of 3.4% to 13.7% during the course of IMRT. The dose delivered to the planning target volume (PTV) of primary gross tumor volume and clinical target volume significantly increased by 1.9% to 2.9% and 1.8% to 2.9% because of weight loss, respectively. The dose to the PTV of gross tumor volume of lymph nodes fluctuated from −2.0% to 1.0%. The dose to the brain stem and the spinal cord was increased (p < 0.001), whereas the dose to the parotid gland was decreased (p < 0.001). Weight loss may lead to significant dosimetric change during IMRT. Repeated scanning and replanning for patients with NPC with an obvious weight loss may be necessary.

  6. Dosimetric properties and stability of thermoluminescent foils made from LiF:Mg,Cu,P or CaSO4:Dy during long-term use

    NASA Astrophysics Data System (ADS)

    Kłosowski, M.; Liszka, M.; Kopeć, R.; Bilski, P.; Kędzierska, D.

    2014-11-01

    A few dosimetric systems based on thermoluminescence [TL] foils were developed in recent years (Nariyama et al. 2006, Radiat. Prot. Dosim. 120, 213-218; Olko et al. 2006 Radiat. Prot. Dosim. 118, 213-218) (Czopyk et al. 2008, Radiat. Meas., 43, 977-980; Kłosowski et al. 2010, Radiat. Meas., 45, 719-721; Kopeć et al. 2013, Radiat.Meas., 56, 380-383). Major application of these systems is mapping of 2D dose distribution for medical treatment plan verification, similarly to photochromic or radiochromic films. The advantage of TL foils compared to other films is their re-usability. In this work we present dosimetric properties as dose linearity and fadding of the foils made from LiF:Mg,Cu,P or CaSO4:Dy phosphors and high temperature polymers. Both types of the foils have good linearity in the range 1-20 Gy for LiF:Mg,Cu,P and 0.1-2 Gy for CaSO4:Dy. Their long term fading does not exceed 3.7% and 9% respectively. We additionally investigated effects of sensitivity loss and emission spectra for both types of the foils. One shortcoming of TL foils is that every heat process may have negative influence on their properties, causing changes of their sensitivity. Register signal of the foils after 15 readouts may be reduced by 16% of the initial. We consider that the main reason of these changes is oxidation of organic contamination on the surface and degradation of a polymer which is one of the components of the foils. Effect of sensitivity decreasing may be slowed down by proper use and cleaning detectors by solvent.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    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.

  8. Dosimetric characterization of a {sup 131}Cs brachytherapy source by thermoluminescence dosimetry in liquid water

    SciTech Connect

    Tailor, Ramesh; Ibbott, Geoffrey; Lampe, Stephanie; Bivens Warren, Whitney; Tolani, Naresh

    2008-12-15

    Dosimetry measurements of a {sup 131}Cs brachytherapy source have been performed in liquid water employing thermoluminescence dosimeters. A search of the literature reveals that this is the first time a complete set of dosimetric parameters for a brachytherapy ''seed'' source has been measured in liquid water. This method avoids the medium correction uncertainties introduced by the use of water-equivalent plastic phantoms. To assure confidence in the results, four different sources were employed for each parameter measured, and measurements were performed multiple times. The measured dosimetric parameters presented here are based on the AAPM Task Group 43 formalism. The dose-rate constant measured in liquid water was (1.063{+-}0.023) cGy h{sup -1} U{sup -1} and was based on the air-kerma strength standard for this source established by the National Institute of Standards and Technology. Measured values for the 2D anisotropy function and the radial dose function are presented.

  9. Dosimetric data on radiation workers in Switzerland: availability and limitations for epidemiological research.

    PubMed

    Moser, M

    1991-01-01

    In 1990 the Swiss National Dose Registry started a test phase of data collection and processing. The question has been raised whether this new, centralised database with its computerized, easily obtainable data on occupational radiation exposure in Switzerland can be used for radioepidemiological studies. This paper sketches the organisation of personal dosimetry in Switzerland, describes the dose registry and other dosimetric data sources and discusses their suitability and limitations for radio-epidemiological studies.

  10. 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.

  11. Investigating the dosimetric and tumor control consequences of prostate seed loss and migration

    SciTech Connect

    Knaup, Courtney; Mavroidis, Panayiotis; Esquivel, Carlos; Stathakis, Sotirios; Swanson, Gregory; Baltas, Dimos; Papanikolaou, Nikos

    2012-06-15

    Purpose: Low dose-rate brachytherapy is commonly used to treat prostate cancer. However, once implanted, the seeds are vulnerable to loss and movement. The goal of this work is to investigate the dosimetric and radiobiological effects of the types of seed loss and migration commonly seen in prostate brachytherapy. Methods: Five patients were used in this study. For each patient three treatment plans were created using Iodine-125, Palladium-103, and Cesium-131 seeds. The three seeds that were closest to the urethra were identified and modeled as the seeds lost through the urethra. The three seeds closest to the exterior of prostatic capsule were identified and modeled as those lost from the prostate periphery. The seed locations and organ contours were exported from Prowess and used by in-house software to perform the dosimetric and radiobiological evaluation. Seed loss was simulated by simultaneously removing 1, 2, or 3 seeds near the urethra 0, 2, or 4 days after the implant or removing seeds near the exterior of the prostate 14, 21, or 28 days after the implant. Results: Loss of one, two or three seeds through the urethra results in a D{sub 90} reduction of 2%, 5%, and 7% loss, respectively. Due to delayed loss of peripheral seeds, the dosimetric effects are less severe than for loss through the urethra. However, while the dose reduction is modest for multiple lost seeds, the reduction in tumor control probability was minimal. Conclusions: The goal of this work was to investigate the dosimetric and radiobiological effects of the types of seed loss and migration commonly seen in prostate brachytherapy. The results presented show that loss of multiple seeds can cause a substantial reduction of D{sub 90} coverage. However, for the patients in this study the dose reduction was not seen to reduce tumor control probability.

  12. Respiratory Organ Motion and Dosimetric Impact on Breast and Nodal Irradiation

    SciTech Connect

    Qi, X. Sharon; White, Julia; Rabinovitch, Rachel; Merrell, Kenneth; Sood, Amit; Bauer, Anderson; Wilson, J. Frank; Miften, Moyed; Li, X. Allen

    2010-10-01

    Purpose: To examine the respiratory motion for target and normal structures during whole breast and nodal irradiation and the resulting dosimetric impact. Methods and Materials: Four-dimensional CT data sets of 18 patients with early-stage breast cancer were analyzed retrospectively. A three-dimensional conformal dosimetric plan designed to irradiate the breast was generated on the basis of CT images at 20% respiratory phase (reference phase). The reference plans were copied to other respiratory phases at 0% (end of inspiration) and 50% (end of expiration) to simulate the effects of breathing motion on whole breast irradiation. Dose-volume histograms, equivalent uniform dose, and normal tissue complication probability were evaluated and compared. Results: Organ motion of up to 8.8 mm was observed during free breathing. A large lung centroid movement was typically associated with a large shift of other organs. The variation of planning target volume coverage during a free breathing cycle is generally within 1%-5% (17 of 18 patients) compared with the reference plan. However, up to 28% of V{sub 45} variation for the internal mammary nodes was observed. Interphase mean dose variations of 2.2%, 1.2%, and 1.4% were observed for planning target volume, ipsilateral lung, and heart, respectively. Dose variations for the axillary nodes and brachial plexus were minimal. Conclusions: The doses delivered to the target and normal structures are different from the planned dose based on the reference phase. During normal breathing, the dosimetric impact of respiratory motion is clinically insignificant with the exception of internal mammary nodes. However, noticeable degradation in dosimetric plan quality may be expected for the patients with large respiratory motion.

  13. Mapping Van

    NASA Technical Reports Server (NTRS)

    1994-01-01

    A NASA Center for the Commercial Development of Space (CCDS) - developed system for satellite mapping has been commercialized for the first time. Global Visions, Inc. maps an area while driving along a road in a sophisticated mapping van equipped with satellite signal receivers, video cameras and computer systems for collecting and storing mapping data. Data is fed into a computerized geographic information system (GIS). The resulting amps can be used for tax assessment purposes, emergency dispatch vehicles and fleet delivery companies as well as other applications.

  14. [Use of the EC 1010 computer to calculate dosimetric parameters for irradiation procedures in gamma teletherapy].

    PubMed

    Likhovetskaia, R B; Dvorova, E V

    1983-05-01

    An ever growing flow of patients requires a good deal of time for the planning of irradiation procedures of patients and causes errors during manual calculations. A small-size computer EC 1010 is proposed for the calculation of dosimetric parameters of irradiation procedures on gamma-beam therapeutic units. A specially designed program is intended for the calculation of dosimetric parameters for different methods of moving and static irradiation taking into account tissue heterogeneity: multifield static irradiation, multizone rotation irradiation, irradiation using dose field forming devices (V-shaped filters, edge blocks, a grid diaphragm). In addition to the main calculated values, the listing contains in a suitable form all necessary information: the patient's name, date of calculation, a unit type for irradiation, irradiation procedure parameters. The computation of output parameters according to each preset program of irradiation takes no more than 1 min. The use of the computer EC 1010 for the calculation of dosimetric parameters of irradiation procedures gives an opportunity to considerably reduce calculation time, to avoid possible errors and to simplify the drawing up of documents.

  15. Patient-specific dosimetric endpoints based treatment plan quality control in radiotherapy

    NASA Astrophysics Data System (ADS)

    Song, Ting; Staub, David; Chen, Mingli; Lu, Weiguo; Tian, Zhen; Jia, Xun; Li, Yongbao; Zhou, Linghong; Jiang, Steve B.; Gu, Xuejun

    2015-11-01

    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.

  16. 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

    2015-11-01

    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.

  17. TH-C-18A-04: Validation of Dosimetric Measurement of CT Radiation Profile Width

    SciTech Connect

    Gauntt, D; Al-Senan, R

    2014-06-15

    Purpose: The ACR now requires that the CT radiation profile width be measured at all clinically used collimations. We developed a method for measuring the profile width using dosimetry alone to allow a faster and simpler measurement of beam widths. Methods: A pencil ionization chamber is used to take two dose-length product measurements in air for a wide collimation. One of these is taken with a 1cm tungsten mask on the pencil chamber. The difference between these measurements is the calibration factor, or the DLP in air per unit length. By dividing the doselength product for any given collimation by this factor, we can rapidly determine the beam profile width.We measured the beam width for all available detector configurations and focal spot sizes on three different CT scanners from two different manufacturers. The measurements were done using film, CR cassette, and the present dosimetric method. Results: The beam widths measured dosimetrically are approximately 2% wider than those measured using film or computed radiography; this difference is believed due to off-focus or scattered radiation. After correcting for this, the dosimetric beam widths match the film and CR widths with an RMS difference of approximately 0.2mm. The measured beam widths are largely insensitive to errors in positioning of the mask, or to tilt errors in the pencil chamber. Conclusion: Using the present method, radiation profile widths can be measured quickly, with an accuracy better than 1mm.

  18. 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

  19. 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

  20. Dosimetric property of mineral extracted from calamari and exposed to gamma rays

    SciTech Connect

    Cruz-Zaragoza, E.; Roman-Lopez, J.; Cruz, L. Perez; Furetta, C.; Chiaravalle, E.; Mangiacotti, M.; Marchesani, G.

    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 128-138 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.

  1. 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.

  2. Dosimetric verification of gated delivery of electron beams using a 2D ion chamber array.

    PubMed

    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.

  3. Medical linear accelerator mounted mini-beam collimator: design, fabrication and dosimetric characterization.

    PubMed

    Cranmer-Sargison, G; Crewson, C; Davis, W M; Sidhu, N P; Kundapur, V

    2015-09-01

    The goal of this work was to design, build and experimentally characterize a linear accelerator mounted mini-beam collimator for use at a nominal 6 MV beam energy. Monte Carlo simulation was used in the design and dosimetric characterization of a compact mini-beam collimator assembly mounted to a medical linear accelerator. After fabrication, experimental mini-beam dose profiles and central axis relative output were measured and the results used to validate the simulation data. The simulation data was then used to establish traceability back to an established dosimetric code of practice. The Monte Carlo simulation work revealed that changes in collimator blade width have a greater influence on the valley-to-peak dose ratio than do changes in blade height. There was good agreement between the modeled and measured profile data, with the exception of small differences on either side of the central peak dose. These differences were found to be systematic across all depths and result from limitations associated with the collimator fabrication. Experimental mini-beam relative output and simulation data agreed to better than ± 2.0%, which is well within the level of uncertainty required for dosimetric traceability of non-standard field geometries. A mini-beam collimator has now been designed, built and experimentally characterized for use with a commercial linear accelerator operated at a nominal 6 MV beam energy.

  4. Medical linear accelerator mounted mini-beam collimator: design, fabrication and dosimetric characterization.

    PubMed

    Cranmer-Sargison, G; Crewson, C; Davis, W M; Sidhu, N P; Kundapur, V

    2015-09-01

    The goal of this work was to design, build and experimentally characterize a linear accelerator mounted mini-beam collimator for use at a nominal 6 MV beam energy. Monte Carlo simulation was used in the design and dosimetric characterization of a compact mini-beam collimator assembly mounted to a medical linear accelerator. After fabrication, experimental mini-beam dose profiles and central axis relative output were measured and the results used to validate the simulation data. The simulation data was then used to establish traceability back to an established dosimetric code of practice. The Monte Carlo simulation work revealed that changes in collimator blade width have a greater influence on the valley-to-peak dose ratio than do changes in blade height. There was good agreement between the modeled and measured profile data, with the exception of small differences on either side of the central peak dose. These differences were found to be systematic across all depths and result from limitations associated with the collimator fabrication. Experimental mini-beam relative output and simulation data agreed to better than ± 2.0%, which is well within the level of uncertainty required for dosimetric traceability of non-standard field geometries. A mini-beam collimator has now been designed, built and experimentally characterized for use with a commercial linear accelerator operated at a nominal 6 MV beam energy. PMID:26305166

  5. Question Mapping

    ERIC Educational Resources Information Center

    Martin, Josh

    2012-01-01

    After accepting the principal position at Farmersville (TX) Junior High, the author decided to increase instructional rigor through question mapping because of the success he saw using this instructional practice at his prior campus. Teachers are the number one influence on student achievement (Marzano, 2003), so question mapping provides a…

  6. Concept Mapping

    ERIC Educational Resources Information Center

    Technology & Learning, 2005

    2005-01-01

    Concept maps are graphical ways of working with ideas and presenting information. They reveal patterns and relationships and help students to clarify their thinking, and to process, organize and prioritize. Displaying information visually--in concept maps, word webs, or diagrams--stimulates creativity. Being able to think logically teaches…

  7. Map Adventures.

    ERIC Educational Resources Information Center

    Geological Survey (Dept. of Interior), Reston, VA.

    This curriculum packet about maps, with seven accompanying lessons, is appropriate for students in grades K-3. Students learn basic concepts for visualizing objects from different perspectives and how to understand and use maps. Lessons in the packet center on a story about a little girl, Nikki, who rides in a hot-air balloon that gives her, and…

  8. Dosimetric Comparison of Helical Tomotherapy and Dynamic Conformal Arc Therapy in Stereotactic Radiosurgery for Vestibular Schwannomas

    SciTech Connect

    Lee, Tsair-Fwu; Chao, Pei-Ju; Wang, Chang-Yu; Lan, Jen-Hong; Huang, Yu-Je; Hsu, Hsuan-Chih; Sung, Chieh-Cheng; Su, Te-Jen; Lian, Shi-Long; Fang, Fu-Min

    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 index (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

  9. Dosimetric comparison of helical tomotherapy and dynamic conformal arc therapy in stereotactic radiosurgery for vestibular schwannomas.

    PubMed

    Lee, Tsair-Fwu; Chao, Pei-Ju; Wang, Chang-Yu; Lan, Jen-Hong; Huang, Yu-Je; Hsu, Hsuan-Chih; Sung, Chieh-Cheng; Su, Te-Jen; Lian, Shi-Long; Fang, Fu-Min

    2011-01-01

    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 index (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(3) (median 3.39 cm(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

  10. Dosimetric Consequences of Interobserver Variability in Delineating the Organs at Risk in Gynecologic Interstitial Brachytherapy

    SciTech Connect

    Damato, Antonio L.; Bair, Ryan J.; Cormack, Robert A.; Kovacs, Arpad; Lee, Larissa J.; Lewis, John H.; Viswanathan, Akila N.

    2014-07-01

    Purpose: To investigate the dosimetric variability associated with interobserver organ-at-risk delineation differences on computed tomography in patients undergoing gynecologic interstitial brachytherapy. Methods and Materials: The rectum, bladder, and sigmoid of 14 patients treated with gynecologic interstitial brachytherapy were retrospectively contoured by 13 physicians. Geometric variability was calculated using κ statistics, conformity index (CI{sub gen}), and coefficient of variation (CV) of volumes contoured across physicians. Dosimetric variability of the single-fraction D{sub 0.1cc} and D{sub 2cc} was assessed through CV across physicians, and the standard deviation of the total EQD2 (equivalent dose in 2 Gy per fraction) brachytherapy dose (SD{sup TOT}) was calculated. Results: The population mean ± 1 standard deviation of κ, CI{sub gen}, and volume CV were, respectively: 0.77 ± 0.06, 0.70 ± 0.08, and 20% ± 6% for bladder; 0.74 ± 06, 0.67 ± 0.08, and 20% ± 5% for rectum; and 0.33 ± 0.20, 0.26 ± 0.17, and 82% ± 42% for sigmoid. Dosimetric variability was as follows: for bladder, CV = 31% ± 19% (SD{sup TOT} = 72 ± 64 Gy) for D{sub 0.1cc} and CV = 16% ± 10% (SD{sup TOT} = 9 ± 6 Gy) for D{sub 2cc}; for rectum, CV = 11% ± 5% (SD{sup TOT} = 16 ± 17 Gy) for D{sub 0.1cc} and CV = 7% ± 2% (SD{sup TOT} = 4 ± 3 Gy) for D{sub 2cc}; for sigmoid, CV = 39% ± 28% (SD{sup TOT} = 12 ± 18 Gy) for D{sub 0.1cc} and CV = 34% ± 19% (SD{sup TOT} = 4 ± 4 Gy) for D{sub 2cc.} Conclusions: Delineation of bladder and rectum by 13 physicians demonstrated substantial geometric agreement and resulted in good dosimetric agreement for all dose-volume histogram parameters except bladder D{sub 0.1cc.} Small delineation differences in high-dose regions by the posterior bladder wall may explain these results. The delineation of sigmoid showed fair geometric agreement. The higher dosimetric variability for sigmoid compared with rectum and bladder did not correlate with

  11. TU-D-9A-01: TG176: Dosimetric Effects of Couch Tops and Immobilization Devices

    SciTech Connect

    Olch, A

    2014-06-15

    The dosimetric impact from devices external to the patient is a complex combination of increased skin dose, reduced tumor dose, and altered dose distribution. Although small monitor unit or dose corrections are routinely made for blocking trays, ion chamber correction factors, or tissue inhomogeneities, the dose perturbation of the treatment couch top or immobilization devices are often overlooked. These devices also increase surface dose, an effect which is also often ignored or underestimated. These concerns have grown recently due to the increased use of monolithic carbon fiber couch tops which are optimal for imaging for patient position verification but cause attenuation and increased surface dose compared to the ‘tennis racket’ style couch top they often replace. Also, arc delivery techniques have replaced stationary gantry techniques which cause a greater fraction of the dose to be delivered from posterior angles. A host of immobilization devices are available and used to increase patient positioning reproducibility, and these also have attenuation and skin dose implications which are often ignored. This report of Task Group 176 serves to present a survey of published data that illustrates the magnitude of the dosimetric effects of a wide range of devices external to the patient. The report also provides methods for modeling couch tops in treatment planning systems so the physicist can accurately compute the dosimetric effects for indexed patient treatments. Both photon and proton beams are considered. A discussion on avoidance of high density structures during beam planning is also provided. An important aspect of this report are the recommendations we make to clinical physicists, treatment planning system vendors, and device vendors on how to make measurements of skin dose and attenuation, how to report these values, and for the vendors, an appeal is made to work together to provide accurate couch top models in planning systems. Learning Objectives

  12. Design and dosimetric considerations of a modified COMS plaque: The reusable 'seed-guide' insert

    SciTech Connect

    Astrahan, Melvin A.; Szechter, Andrzej; Finger, Paul T.

    2005-08-15

    The Collaborative Ocular Melanoma Study (COMS) developed a standardized set of eye plaques that consist of a 0.5 mm thick bowl-like gold alloy backing with a cylindrical collimating lip. A Silastic seed carrier into which {sup 125}I seeds are loaded was designed to fit within the backing. The carrier provides a standardized seed pattern and functions to offset the seeds by 1.0 mm from the concave (front) surface of the carrier. These Silastic carriers have been found to be difficult to load, preclude flash sterilization, and are a source of dosimetric uncertainty because the effective atomic number of Silastic is significantly higher than that of water. The main dosimetric effect of the Silastic carrier is a dose-reduction (compared to homogeneous water) of approximately 10%-15% for {sup 125}I radiation. The dose reduction is expected to be even greater for {sup 103}Pd radiation. In an attempt to improve upon, yet retain as much of the familiar COMS design as possible, we have developed a thin 'seed-guide' insert made of gold alloy. This new insert has cutouts which match the seed pattern of the Silastic carrier, but allows the seeds to be glued directly to the inner surface of the gold backing using either dental acrylic or a cyanoacrylate adhesive. When glued directly to the gold backing the seeds are offset a few tenths of a millimeter further away from the scleral surface compared to using the Silastic carrier. From a dosimetric perspective, the space formerly occupied by the Silastic carrier is now assumed to be water equivalent. Water equivalency is a desirable attribute for this space because it eliminates the dosimetric uncertainties related to the atomic composition of Silastic and thereby facilitates the use of either {sup 125}I and/or {sup 103}Pd seeds. The caveat is that a new source of dosimetric uncertainty would be introduced were an air bubble to become trapped in this space during or after the surgical insertion. The presence of air in this space

  13. Mapping racism.

    PubMed

    Moss, Donald B

    2006-01-01

    The author uses the metaphor of mapping to illuminate a structural feature of racist thought, locating the degraded object along vertical and horizontal axes. These axes establish coordinates of hierarchy and of distance. With the coordinates in place, racist thought begins to seem grounded in natural processes. The other's identity becomes consolidated, and parochialism results. The use of this kind of mapping is illustrated via two patient vignettes. The author presents Freud's (1905, 1927) views in relation to such a "mapping" process, as well as Adorno's (1951) and Baldwin's (1965). Finally, the author conceptualizes the crucial status of primitivity in the workings of racist thought.

  14. Dosimetric Verification Using Monte Carlo Calculations for Tissue Heterogeneity-Corrected Conformal Treatment Plans Following RTOG 0813 Dosimetric Criteria for Lung Cancer Stereotactic Body Radiotherapy

    SciTech Connect

    Li Jun; Galvin, James; Harrison, Amy; Timmerman, Robert; Yu Yan; Xiao Ying

    2012-10-01

    Purpose: The recently activated Radiation Therapy Oncology Group (RTOG) studies of stereotactic body radiation therapy (SBRT) for non-small-cell lung cancer (NSCLC) require tissue density heterogeneity correction, where the high and intermediate dose compliance criteria were established based on superposition algorithm dose calculations. The study was aimed at comparing superposition algorithm dose calculations with Monte Carlo (MC) dose calculations for SBRT for NSCLC and to evaluate whether compliance criteria need to be adjusted for MC dose calculations. Methods and Materials: Fifteen RTOG 0236 study sets were used. The planning tumor volumes (PTV) ranged from 10.7 to 117.1 cm{sup 3}. SBRT conformal treatment plans were generated using XiO (CMS Inc.) treatment planning software with superposition algorithm to meet the dosimetric high and intermediate compliance criteria recommended by the RTOG 0813 protocol. Plans were recalculated using the MC algorithm of a Monaco (CMS, Inc.) treatment planning system. Tissue density heterogeneity correction was applied in both calculations. Results: Overall, the dosimetric quantities of the MC calculations have larger magnitudes than those of the superposition calculations. On average, R{sub 100%} (ratio of prescription isodose volume to PTV), R{sub 50%} (ratio of 50% prescription isodose volume to PTV), D{sub 2cm} (maximal dose 2 cm from PTV in any direction as a percentage of prescription dose), and V{sub 20} (percentage of lung receiving dose equal to or larger than 20 Gy) increased by 9%, 12%, 7%, and 18%, respectively. In the superposition plans, 3 cases did not meet criteria for R{sub 50%} or D{sub 2cm}. In the MC-recalculated plans, 8 cases did not meet criteria for R{sub 100%}, R{sub 50%}, or D{sub 2cm}. After reoptimization with MC calculations, 5 cases did not meet the criteria for R{sub 50%} or D{sub 2cm}. Conclusions: Results indicate that the dosimetric criteria, e.g., the criteria for R{sub 50%} recommended by

  15. Mapping Biodiversity.

    ERIC Educational Resources Information Center

    World Wildlife Fund, Washington, DC.

    This document features a lesson plan that examines how maps help scientists protect biodiversity and how plants and animals are adapted to specific ecoregions by comparing biome, ecoregion, and habitat. Samples of instruction and assessment are included. (KHR)

  16. Planetary Mapping

    NASA Astrophysics Data System (ADS)

    Greeley, Ronald; Batson, Raymond M.

    2007-02-01

    Preface; List of contributors; 1. Introduction R. Greeley and R. M. Batson; 2. History of planetary cartography R. M. Batson, E. A. Whitaker and D. E. Wilhelms; 3. Cartography R. M. Batson; 4. Planetary nomenclature M. E. Strobell and H. Masursky; 5. Geodetic control M. E. Davies; 6. Topographic mapping S. S. C. Wu and F. J. Doyle; 7. Geologic mapping D. E. Wilhelms; Appendices R. M. Batson and J. L. Inge; Index.

  17. Map Separates

    USGS Publications Warehouse

    ,

    2001-01-01

    U.S. Geological Survey (USGS) topographic maps are printed using up to six colors (black, blue, green, red, brown, and purple). To prepare your own maps or artwork based on maps, you can order separate black-and-white film positives or negatives for any color printed on a USGS topographic map, or for one or more of the groups of related features printed in the same color on the map (such as drainage and drainage names from the blue plate.) In this document, examples are shown with appropriate ink color to illustrate the various separates. When purchased, separates are black-and-white film negatives or positives. After you receive a film separate or composite from the USGS, you can crop, enlarge or reduce, and edit to add or remove details to suit your special needs. For example, you can adapt the separates for making regional and local planning maps or for doing many kinds of studies or promotions by using the features you select and then printing them in colors of your choice.

  18. Venus mapping

    NASA Technical Reports Server (NTRS)

    Batson, R. M.; Morgan, H. F.; Sucharski, Robert

    1991-01-01

    Semicontrolled image mosaics of Venus, based on Magellan data, are being compiled at 1:50,000,000, 1:10,000,000, 1:5,000,000, and 1:1,000,000 scales to support the Magellan Radar Investigator (RADIG) team. The mosaics are semicontrolled in the sense that data gaps were not filled and significant cosmetic inconsistencies exist. Contours are based on preliminary radar altimetry data that is subjected to revision and improvement. Final maps to support geologic mapping and other scientific investigations, to be compiled as the dataset becomes complete, will be sponsored by the Planetary Geology and Geophysics Program and/or the Venus Data Analysis Program. All maps, both semicontrolled and final, will be published as I-maps by the United States Geological Survey. All of the mapping is based on existing knowledge of the spacecraft orbit; photogrammetric triangulation, a traditional basis for geodetic control on planets where framing cameras were used, is not feasible with the radar images of Venus, although an eventual shift of coordinate system to a revised spin-axis location is anticipated. This is expected to be small enough that it will affect only large-scale maps.

  19. SU-E-J-94: Geometric and Dosimetric Evaluation of Deformation Image Registration Algorithms Using Virtual Phantoms Generated From Patients with Lung Cancer

    SciTech Connect

    Shen, Z; Greskovich, J; Xia, P; Bzdusek, K

    2015-06-15

    Purpose: To generate virtual phantoms with clinically relevant deformation and use them to objectively evaluate geometric and dosimetric uncertainties of deformable image registration (DIR) algorithms. Methods: Ten lung cancer patients undergoing adaptive 3DCRT planning were selected. For each patient, a pair of planning CT (pCT) and replanning CT (rCT) were used as the basis for virtual phantom generation. Manually adjusted meshes were created for selected ROIs (e.g. PTV, lungs, spinal cord, esophagus, and heart) on pCT and rCT. The mesh vertices were input into a thin-plate spline algorithm to generate a reference displacement vector field (DVF). The reference DVF was used to deform pCT to generate a simulated replanning CT (srCT) that was closely matched to rCT. Three DIR algorithms (Demons, B-Spline, and intensity-based) were applied to these ten virtual phantoms. The images, ROIs, and doses were mapped from pCT to srCT using the DVFs computed by these three DIRs and compared to those mapped using the reference DVF. Results: The average Dice coefficients for selected ROIs were from 0.85 to 0.96 for Demons, from 0.86 to 0.97 for intensity-based, and from 0.76 to 0.95 for B-Spline. The average Hausdorff distances for selected ROIs were from 2.2 to 5.4 mm for Demons, from 2.3 to 6.8 mm for intensity-based, and from 2.4 to 11.4 mm for B-Spline. The average absolute dose errors for selected ROIs were from 0.2 to 0.6 Gy for Demons, from 0.1 to 0.5 Gy for intensity-based, and from 0.5 to 1.5 Gy for B-Spline. Conclusion: Virtual phantoms were modeled after patients with lung cancer and were clinically relevant for adaptive radiotherapy treatment replanning. Virtual phantoms with known DVFs serve as references and can provide a fair comparison when evaluating different DIRs. Demons and intensity-based DIRs were shown to have smaller geometric and dosimetric uncertainties than B-Spline. Z Shen: None; K Bzdusek: an employee of Philips Healthcare; J Greskovich: None; P Xia

  20. SU-E-J-119: Head-And-Neck Digital Phantoms for Geometric and Dosimetric Uncertainty Evaluation of CT-CBCT Deformable Image Registration

    SciTech Connect

    Shen, Z; Koyfman, S; Xia, P; Bzdusek, K

    2015-06-15

    Purpose: To evaluate geometric and dosimetric uncertainties of CT-CBCT deformable image registration (DIR) algorithms using digital phantoms generated from real patients. Methods: We selected ten H&N cancer patients with adaptive IMRT. For each patient, a planning CT (CT1), a replanning CT (CT2), and a pretreatment CBCT (CBCT1) were used as the basis for digital phantom creation. Manually adjusted meshes were created for selected ROIs (e.g. PTVs, brainstem, spinal cord, mandible, and parotids) on CT1 and CT2. The mesh vertices were input into a thin-plate spline algorithm to generate a reference displacement vector field (DVF). The reference DVF was applied to CBCT1 to create a simulated mid-treatment CBCT (CBCT2). The CT-CBCT digital phantom consisted of CT1 and CBCT2, which were linked by the reference DVF. Three DIR algorithms (Demons, B-Spline, and intensity-based) were applied to these ten digital phantoms. The images, ROIs, and volumetric doses were mapped from CT1 to CBCT2 using the DVFs computed by these three DIRs and compared to those mapped using the reference DVF. Results: The average Dice coefficients for selected ROIs were from 0.83 to 0.94 for Demons, from 0.82 to 0.95 for B-Spline, and from 0.67 to 0.89 for intensity-based DIR. The average Hausdorff distances for selected ROIs were from 2.4 to 6.2 mm for Demons, from 1.8 to 5.9 mm for B-Spline, and from 2.8 to 11.2 mm for intensity-based DIR. The average absolute dose errors for selected ROIs were from 0.7 to 2.1 Gy for Demons, from 0.7 to 2.9 Gy for B- Spline, and from 1.3 to 4.5 Gy for intensity-based DIR. Conclusion: Using clinically realistic CT-CBCT digital phantoms, Demons and B-Spline were shown to have similar geometric and dosimetric uncertainties while intensity-based DIR had the worst uncertainties. CT-CBCT DIR has the potential to provide accurate CBCT-based dose verification for H&N adaptive radiotherapy. Z Shen: None; K Bzdusek: an employee of Philips Healthcare; S Koyfman: None; P Xia

  1. Dosimetric and mechanical characteristics of a commercial dynamic {mu}MLC used in SRS

    SciTech Connect

    Galal, Mohamed M.; Keogh, Sinead; Khalil, Sultan

    2011-07-15

    Purpose: The aim of this work is to carry out mechanical and dosimetric assessments on a commercial dynamic micromulti leaf collimator system to be used for stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT). Mechanical parameters such as leaf position accuracy with different gantry angles and leaf position reproducibility were measured. Also dosimetric measurements of the interleaf leakage, intraleaf transmission, penumbra width, and light field alignment were carried out. Furthermore, measurements of output factors (S{sub cp}) and in-air factors (S{sub c}) for the {mu}MLC system will be reported. Methods: EBT2 films were used to assess the leaf position error with gantry angle and after stress test, penumbra width and light field alignment. Leaf leakage was quantified using both EBT2 film and a pinpoint ion chamber. With regard to output factors, the pinpoint chamber was placed in a water phantom at 10 cm depth and 100 cm SSD. For in-air output factor measurements, 0.2 cm of brass was placed above the photon diode as build-up. Results: Measurements of mechanical parameters gave values of 0.05 cm (SD 0.035) for the average leaf position accuracy for different gantry angles and after stress test. Dosimetric measurements, yielded values of 0.22 {+-} 0.01 and 0.24 {+-} 0.01 cm, respectively, for side and head leaf penumbras. Also, average leaf abutting, leakage and transmission were found to be 0.65, 0.91, and 0.20%, respectively. Conclusions: (a) The add-on {mu}MLC system in combination with our LINAC has been commissioned to be used for clinical purposes and showed good agreement with published results for different {mu}MLC types. (b) This work has lead to the recommendation that leaves should be recalibrated after ten static beams or after each dynamic arc.

  2. Dosimetric comparison of four target alignment methods for prostate cancer radiotherapy

    SciTech Connect

    O'Daniel, Jennifer C.; Dong Lei . E-mail: ldong@mdanderson.org; Zhang Lifei; Crevoisier, Renaud de; Wang He; Lee, Andrew K.; Cheung, Rex; Tucker, Susan L.; Kudchadker, Rajat J.; Bonnen, Mark D.; Cox, James D.; Mohan, Radhe; Kuban, Deborah A.

    2006-11-01

    Purpose: The aim of this study was to compare the dosimetric consequences of 4 treatment delivery techniques for prostate cancer patients treated with intensity-modulated radiotherapy (IMRT). Methods and Materials: During an 8-week course of radiotherapy, 10 patients underwent computed tomography (CT) scans 3 times per week (243 total) before daily treatment with a CT-linear accelerator. Treatment delivery was simulated by realigning a fixed-margin treatment plan on each CT scan and calculating doses. The alignment methods were those based on the following: skin marks, bony registration, ultrasonography (United States), and in-room CT. For the last two methods, prostate was the alignment target. The dosimetric effects of these alignment methods on the prostate, seminal vesicles, rectum, and bladder were compared. The average daily minimum dose to 0.1 cm{sup 3} was used as the metric for target coverage. Results: Skin and bone alignments provided acceptable prostate coverage for only 70% of patients, US alignment for 90%, and CT alignment for 100%. CT-based alignment of the prostate provided seminal vesicle (SV) coverage of {>=}69 Gy for all patients; US and bone alignments provided SV coverage of {>=}60 Gy. This SV coverage may be acceptable for early-stage cancer (equivalent SV dose = 55.8 Gy at 1.8 Gy per fraction), but unacceptable for late-stage cancer (SV dose = 75.6 Gy). At 75.6 Gy, the acceptable rate for SV coverage was 40% for skin and bone alignments, 70% for US, and 80% for CT. Conclusions: Direct target alignment methods (US and CT) provided better target coverage. CT-guided alignment provided the best and most consistent dosimetric coverage. A larger planning target volume margin is needed for SV coverage when the alignment target is the prostate.

  3. Dosimetric optimization of a conical breast brachytherapy applicator for improved skin dose sparing

    SciTech Connect

    Yang Yun; Rivard, Mark J.

    2010-11-15

    Purpose: Both the AccuBoost D-shaped and round applicators have been dosimetrically characterized and clinically used to treat patients with breast cancer. While the round applicators provide conformal dose coverage, under certain clinical circumstances the breast skin dose may be higher than preferred. The purpose of this study was to modify the round applicators to minimize skin dose while not substantially affecting dose uniformity within the target volume and reducing the treatment time. Methods: In order to irradiate the intended volume while sparing critical structures such as the skin, the current round applicator design has been augmented through the addition of an internal truncated cone (i.e., frustum) shield. Monte Carlo methods and clinical constraints were used to design the optimal cone applicator. With the cone applicator now defined as the entire assembly including the surrounding tungsten-alloy shell holding the HDR {sup 192}Ir source catheter, the applicator height was reduced to diminish the treatment time while minimizing skin dose. Monte Carlo simulation results were validated using both radiochromic film and ionization chamber measurements based on established techniques. Results: The optimal cone applicators diminished the maximum skin dose by 15%-32% (based on the applicator diameter and breast separation) with the tumor dose reduced by less than 3% for a constant exposure time. Furthermore, reduction in applicator height diminished the treatment time by up to 30%. Radiochromic film and ionization chamber dosimetric results in phantom agreed with Monte Carlo simulation results typically within 3%. Larger differences were outside the treatment volume in low dose regions or associated with differences between the measurement and Monte Carlo simulation environments. Conclusions: A new radiotherapy treatment device was developed and dosimetrically characterized. This set of applicators significantly reduces the skin dose and treatment time while

  4. Dosimetric comparison of volumetric modulated arc therapy with robotic stereotactic radiation therapy in hepatocellular carcinoma

    PubMed Central

    Paik, Eun Kyung; Choi, Chul Won; Jang, Won Il; Lee, Sung Hyun; Choi, Sang Hyoun; Kim, Kum Bae; Lee, Dong Han

    2015-01-01

    Purpose To compare volumetric modulated arc therapy of RapidArc with robotic stereotactic body radiation therapy (SBRT) of CyberKnife in the planning and delivery of SBRT for hepatocellular carcinoma (HCC) treatment by analyzing dosimetric parameters. Materials and Methods Two radiation treatment plans were generated for 29 HCC patients, one using Eclipse for the RapidArc plan and the other using Multiplan for the CyberKnife plan. The prescription dose was 60 Gy in 3 fractions. The dosimetric parameters of planning target volume (PTV) coverage and normal tissue sparing in the RapidArc and the CyberKnife plans were analyzed. Results The conformity index was 1.05 ± 0.02 for the CyberKnife plan, and 1.13 ± 0.10 for the RapidArc plan. The homogeneity index was 1.23 ± 0.01 for the CyberKnife plan, and 1.10 ± 0.03 for the RapidArc plan. For the normal liver, there were significant differences between the two plans in the low-dose regions of V1 and V3. The normalized volumes of V60 for the normal liver in the RapidArc plan were drastically increased when the mean dose of the PTVs in RapidArc plan is equivalent to the mean dose of the PTVs in the CyberKnife plan. Conclusion CyberKnife plans show greater dose conformity, especially in small-sized tumors, while RapidArc plans show good dosimetric distribution of low dose sparing in the normal liver and body. PMID:26484307

  5. Dosimetric effects of an air cavity for the SAVI partial breast irradiation applicator

    SciTech Connect

    Richardson, Susan L.; Pino, Ramiro

    2010-08-15

    Purpose: To investigate the dosimetric effect of the air inside the SAVI partial breast irradiation device. Methods: The authors have investigated how the air inside the SAVI partial breast irradiation device changes the delivered dose from the homogeneously calculated dose. Measurements were made with the device filled with air and water to allow comparison to a homogenous dose calculation done by the treatment planning system. Measurements were made with an ion chamber, TLDs, and film. Monte Carlo (MC) simulations of the experiment were done using the EGSnrc suite. The MC model was validated by comparing the water-filled calculations to those from a commercial treatment planning system. Results: The magnitude of the dosimetric effect depends on the size of the cavity, the arrangement of sources, and the relative dwell times. For a simple case using only the central catheter of the largest device, MC results indicate that the dose at the prescription point 1 cm away from the air-water boundary is about 9% higher than the homogeneous calculation. Independent measurements in a water phantom with a similar air cavity gave comparable results. MC simulation of a realistic multidwell position plan showed discrepancies of about 5% on average at the prescription point for the largest device. Conclusions: The dosimetric effect of the air cavity is in the range of 3%-9%. Unless a heterogeneous dose calculation algorithm is used, users should be aware of the possibility of small treatment planning dose errors for this device and make modifications to the treatment delivery, if necessary.

  6. SU-E-T-123: Dosimetric Comparison Between Portrait and Landscape Orientations in Radiochromic Film Dosimetry

    SciTech Connect

    Kakinohana, Y; Toita, T; Kasuya, G; Ariga, T; Heianna, J; Murayama, S

    2014-06-01

    Purpose: To compare the dosimetric properties of radiochromic films with different orientation. Methods: A sheet of EBT3 film was cut into eight pieces with the following sizes: 15×15 cm2 (one piece), 5x15 cm{sup 2} (two) and 4×5 cm{sup 2} (five). A set of two EBT3 sheets was used at each dose level. Two sets were used changing the delivered doses (1 and 2 Gy). The 5×15 cm{sup 2} pieces were rotated by 90 degrees in relation to each other, such that one had landscape orientation and the other had portrait orientation. All 5×15 cm2 pieces were irradiated with their long side aligned with the x-axis of the radiation field. The 15×15 cm{sup 2} pieces were irradiated rotated at 90 degrees to each other. Five pieces, (a total of ten from two sheets) were used to obtain a calibration curve. The irradiated films were scanned using an Epson ES-2200 scanner and were analyzed using ImageJ software. In this study, no correction was applied for the nonuniform scanner signal that is evident in the direction of the scanner lamp. Each film piece was scanned both in portrait and landscape orientations. Dosimetric comparisons of the beam profiles were made in terms of the film orientations (portrait and landscape) and scanner bed directions (perpendicular and parallel to the scanner movement). Results: In general, portrait orientation exhibited higher noise than landscape and was adversely affected to a great extent by the nonuniformity in the direction of the scanner lamp. A significant difference in the measured field widths between the perpendicular and parallel directions was found for both orientations. Conclusion: Without correction for the nonuniform scanner signal in the direction of the scanner lamp, a landscape orientation is preferable. A more detailed investigation is planned to evaluate quantitatively the effect of orientation on the dosimetric properties of a film.

  7. Dosimetric characterization of an 192Ir brachytherapy source with the Monte Carlo code PENELOPE.

    PubMed

    Casado, Francisco Javier; García-Pareja, Salvador; Cenizo, Elena; Mateo, Beatriz; Bodineau, Coral; Galán, Pedro

    2010-01-01

    Monte Carlo calculations are highly spread and settled practice to calculate brachytherapy sources dosimetric parameters. In this study, recommendations of the AAPM TG-43U1 report have been followed to characterize the Varisource VS2000 (192)Ir high dose rate source, provided by Varian Oncology Systems. In order to obtain dosimetric parameters for this source, Monte Carlo calculations with PENELOPE code have been carried out. TG-43 formalism parameters have been presented, i.e., air kerma strength, dose rate constant, radial dose function and anisotropy function. Besides, a 2D Cartesian coordinates dose rate in water table has been calculated. These quantities are compared to this source reference data, finding results in good agreement with them. The data in the present study complement published data in the next aspects: (i) TG-43U1 recommendations are followed regarding to phantom ambient conditions and to uncertainty analysis, including statistical (type A) and systematic (type B) contributions; (ii) PENELOPE code is benchmarked for this source; (iii) Monte Carlo calculation methodology differs from that usually published in the way to estimate absorbed dose, leaving out the track-length estimator; (iv) the results of the present work comply with the most recent AAPM and ESTRO physics committee recommendations about Monte Carlo techniques, in regards to dose rate uncertainty values and established differences between our results and reference data. The results stated in this paper provide a complete parameter collection, which can be used for dosimetric calculations as well as a means of comparison with other datasets from this source.

  8. The impact of emphysema on dosimetric parameters for stereotactic body radiotherapy of the lung

    PubMed Central

    Ochiai, Satoru; Nomoto, Yoshihito; Yamashita, Yasufumi; Inoue, Tomoki; Murashima, Shuuichi; Hasegawa, Daisuke; Kurita, Yoshie; Watanabe, Yui; Toyomasu, Yutaka; Kawamura, Tomoko; Takada, Akinori; Noriko; Kobayashi, Shigeki; Sakuma, Hajime

    2016-01-01

    The purpose of this study was to evaluate the impact of emphysematous changes in lung on dosimetric parameters in stereotactic body radiation therapy (SBRT) for lung tumor. A total of 72 treatment plans were reviewed, and dosimetric factors [including homogeneity index (HI) and conformity index (CI)] were evaluated. Emphysematous changes in lung were observed in 43 patients (60%). Patients were divided into three groups according to the severity of emphysema: no emphysema (n = 29), mild emphysema (n = 22) and moderate to severe emphysema groups (n = 21). The HI (P < 0.001) and the CI (P = 0.029) were significantly different in accordance with the severity of emphysema in one-way analysis of variance (ANOVA). The HI value was significantly higher in the moderate to severe emphysema group compared with in the no emphysema (Tukey, P < 0.001) and mild emphysema groups (P = 0.002). The CI value was significantly higher in the moderate to severe emphysema group compared with in the no emphysema group (P = 0.044). In multiple linear regression analysis, the severity of emphysema (P < 0.001) and the mean material density of the lung within the PTV (P < 0.001) were significant factors for HI, and the mean density of the lung within the PTV (P = 0.005) was the only significant factor for CI. The mean density of the lung within the PTV was significantly different in accordance with the severity of emphysema (one-way ANOVA, P = 0.008) and the severity of emphysema (P < 0.001) was one of the significant factors for the density of the lung within the PTV in multiple linear regression analysis. Our results suggest that emphysematous changes in the lung significantly impact on several dosimetric parameters in SBRT, and they should be carefully evaluated before treatment planning. PMID:27380802

  9. Craniospinal Irradiation Techniques: A Dosimetric Comparison of Proton Beams With Standard and Advanced Photon Radiotherapy

    SciTech Connect

    Yoon, Myonggeun; Shin, Dong Ho; Kim, Jinsung; Kim, Jong Won; Kim, Dae Woong; Park, Sung Yong; Lee, Se Byeong; Kim, Joo Young; Park, Hyeon-Jin; Park, Byung Kiu; Shin, Sang Hoon

    2011-11-01

    Purpose: To evaluate the dosimetric benefits of advanced radiotherapy techniques for craniospinal irradiation in cancer in children. Methods and Materials: Craniospinal irradiation (CSI) using three-dimensional conformal radiotherapy (3D-CRT), tomotherapy (TOMO), and proton beam treatment (PBT) in the scattering mode was planned for each of 10 patients at our institution. Dosimetric benefits and organ-specific radiation-induced cancer risks were based on comparisons of dose-volume histograms (DVHs) and on the application of organ equivalent doses (OEDs), respectively. Results: When we analyzed the organ-at-risk volumes that received 30%, 60%, and 90% of the prescribed dose (PD), we found that PBT was superior to TOMO and 3D-CRT. On average, the doses delivered by PBT to the esophagus, stomach, liver, lung, pancreas, and kidney were 19.4 Gy, 0.6 Gy, 0.3 Gy, 2.5 Gy, 0.2 Gy, and 2.2 Gy for the PD of 36 Gy, respectively, which were significantly lower than the doses delivered by TOMO (22.9 Gy, 4.5 Gy, 6.1 Gy, 4.0 Gy, 13.3 Gy, and 4.9 Gy, respectively) and 3D-CRT (34.6 Gy, 3.6 Gy, 8.0 Gy, 4.6 Gy, 22.9 Gy, and 4.3 Gy, respectively). Although the average doses delivered by PBT to the chest and abdomen were significantly lower than those of 3D-CRT or TOMO, these differences were reduced in the head-and-neck region. OED calculations showed that the risk of secondary cancers in organs such as the stomach, lungs, thyroid, and pancreas was much higher when 3D-CRT or TOMO was used than when PBT was used. Conclusions: Compared with photon techniques, PBT showed improvements in most dosimetric parameters for CSI patients, with lower OEDs to organs at risk.

  10. Dosimetric effects caused by couch tops and immobilization devices: Report of AAPM Task Group 176

    SciTech Connect

    Olch, Arthur J.; Gerig, Lee; Li, Heng; Mihaylov, Ivaylo; Morgan, Andrew

    2014-06-15

    The dosimetric impact from devices external to the patient is a complex combination of increased skin dose, reduced tumor dose, and altered dose distribution. Although small monitor unit or dose corrections are routinely made for blocking trays, ion chamber correction factors, e.g., accounting for temperature and pressure, or tissue inhomogeneities, the dose perturbation of the treatment couch top or immobilization devices is often overlooked. These devices also increase skin dose, an effect which is also often ignored or underestimated. These concerns have grown recently due to the increased use of monolithic carbon fiber couch tops which are optimal for imaging for patient position verification but cause attenuation and increased skin dose compared to the “tennis racket” style couch top they often replace. Also, arc delivery techniques have replaced stationary gantry techniques which cause a greater fraction of the dose to be delivered from posterior angles. A host of immobilization devices are available and used to increase patient positioning reproducibility, and these also have attenuation and skin dose implications which are often ignored. This report of Task Group 176 serves to present a survey of published data that illustrates the magnitude of the dosimetric effects of a wide range of devices external to the patient. The report also provides methods for modeling couch tops in treatment planning systems so the physicist can accurately compute the dosimetric effects for indexed patient treatments. Both photon and proton beams are considered. A discussion on avoidance of high density structures during beam planning is also provided. An important aspect of this report are the recommendations the authors make to clinical physicists, treatment planning system vendors, and device vendors on how to make measurements of surface dose and attenuation and how to report these values. For the vendors, an appeal is made to work together to provide accurate couch top

  11. Assessment of dosimetrical performance in 11 Varian a-Si500 electronic portal imaging devices

    NASA Astrophysics Data System (ADS)

    Kavuma, Awusi; Glegg, Martin; Currie, Garry; Elliott, Alex

    2008-12-01

    Dosimetrical characteristics of 11 Varian a-Si-500 electronic portal imaging devices (EPIDs) in clinical use for periods ranging between 10 and 86 months were investigated for consistency of performance and portal dosimetry implications. Properties studied include short-term reproducibility, signal linearity with monitor units, response to reference beam, signal uniformity across the detector panel, signal dependence on field size, dose-rate influence, memory effects and image profiles as a function of monitor units. The EPID measurements were also compared with those of the ionization chambers' to ensure stability of the linear accelerators. Depending on their clinical installation date, the EPIDs were interfaced with one of the two different acquisition control software packages, IAS2/IDU-II or IAS3/IDU-20. Both the EPID age and image acquisition system influenced the dosimetric characteristics with the newer version (IAS3 with IDU-20) giving better data reproducibility and linearity fit than the older version (IAS2 with IDU-II). The relative signal response (uniformity) after 50 MU was better than 95% of the central value and independent of detector. Sensitivity for all EPIDs reduced continuously with increasing dose rates for the newer image acquisition software. In the dose-rate range 100-600 MU min-1, the maximum variation in sensitivity ranged between 1 and 1.8% for different EPIDs. For memory effects, the increase in the measured signal at the centre of the irradiated field for successive images was within 1.8% and 1.0% for the older and newer acquisition systems, respectively. Image profiles acquired at a lower MU in the radial plane (gun-target) had gradients in measured pixel values of up to 25% for the older system. Detectors with software/hardware versions IAS3/IDU-20 have a high degree of accuracy and are more suitable for routine quantitative IMRT dosimetrical verification.

  12. Dosimetric Evaluation of Automatic Segmentation for Adaptive IMRT for Head-and-Neck Cancer

    SciTech Connect

    Tsuji, Stuart Y.; Hwang, Andrew; Weinberg, Vivian; Yom, Sue S.; Quivey, Jeanne M.; Xia Ping

    2010-07-01

    Purpose: Adaptive planning to accommodate anatomic changes during treatment requires repeat segmentation. This study uses dosimetric endpoints to assess automatically deformed contours. Methods and Materials: Sixteen patients with head-and-neck cancer had adaptive plans because of anatomic change during radiotherapy. Contours from the initial planning computed tomography (CT) were deformed to the mid-treatment CT using an intensity-based free-form registration algorithm then compared with the manually drawn contours for the same CT using the Dice similarity coefficient and an overlap index. The automatic contours were used to create new adaptive plans. The original and automatic adaptive plans were compared based on dosimetric outcomes of the manual contours and on plan conformality. Results: Volumes from the manual and automatic segmentation were similar; only the gross tumor volume (GTV) was significantly different. Automatic plans achieved lower mean coverage for the GTV: V95: 98.6 {+-} 1.9% vs. 89.9 {+-} 10.1% (p = 0.004) and clinical target volume: V95: 98.4 {+-} 0.8% vs. 89.8 {+-} 6.2% (p < 0.001) and a higher mean maximum dose to 1 cm{sup 3} of the spinal cord 39.9 {+-} 3.7 Gy vs. 42.8 {+-} 5.4 Gy (p = 0.034), but no difference for the remaining structures. Conclusions: Automatic segmentation is not robust enough to substitute for physician-drawn volumes, particularly for the GTV. However, it generates normal structure contours of sufficient accuracy when assessed by dosimetric end points.

  13. Dosimetric effects caused by couch tops and immobilization devices: report of AAPM Task Group 176.

    PubMed

    Olch, Arthur J; Gerig, Lee; Li, Heng; Mihaylov, Ivaylo; Morgan, Andrew

    2014-06-01

    The dosimetric impact from devices external to the patient is a complex combination of increased skin dose, reduced tumor dose, and altered dose distribution. Although small monitor unit or dose corrections are routinely made for blocking trays, ion chamber correction factors, e.g., accounting for temperature and pressure, or tissue inhomogeneities, the dose perturbation of the treatment couch top or immobilization devices is often overlooked. These devices also increase skin dose, an effect which is also often ignored or underestimated. These concerns have grown recently due to the increased use of monolithic carbon fiber couch tops which are optimal for imaging for patient position verification but cause attenuation and increased skin dose compared to the "tennis racket" style couch top they often replace. Also, arc delivery techniques have replaced stationary gantry techniques which cause a greater fraction of the dose to be delivered from posterior angles. A host of immobilization devices are available and used to increase patient positioning reproducibility, and these also have attenuation and skin dose implications which are often ignored. This report of Task Group 176 serves to present a survey of published data that illustrates the magnitude of the dosimetric effects of a wide range of devices external to the patient. The report also provides methods for modeling couch tops in treatment planning systems so the physicist can accurately compute the dosimetric effects for indexed patient treatments. Both photon and proton beams are considered. A discussion on avoidance of high density structures during beam planning is also provided. An important aspect of this report are the recommendations the authors make to clinical physicists, treatment planning system vendors, and device vendors on how to make measurements of surface dose and attenuation and how to report these values. For the vendors, an appeal is made to work together to provide accurate couch top

  14. Prospective assessment of dosimetric/physiologic-based models for predicting radiation pneumonitis

    SciTech Connect

    Kocak, Zafer; Borst, Gerben R.; Zeng Jing; Zhou Sumin; Hollis, Donna R.; Zhang Junan; Evans, Elizabeth S.; Folz, Rodney J.; Wong, Terrence; Kahn, Daniel; Belderbos, Jose S.A.; Lebesque, Joos V.; Marks, Lawrence B. . E-mail: marks@radonc.duke.edu

    2007-01-01

    Purpose: Clinical and 3D dosimetric parameters are associated with symptomatic radiation pneumonitis rates in retrospective studies. Such parameters include: mean lung dose (MLD), radiation (RT) dose to perfused lung (via SPECT), and pre-RT lung function. Based on prior publications, we defined pre-RT criteria hypothesized to be predictive for later development of pneumonitis. We herein prospectively test the predictive abilities of these dosimetric/functional parameters on 2 cohorts of patients from Duke and Netherlands Cancer Institute (NKI). Methods and Materials: For the Duke cohort, 55 eligible patients treated between 1999 and 2005 on a prospective IRB-approved study to monitor RT-induced lung injury were analyzed. A similar group of patients treated at the NKI between 1996 and 2002 were identified. Patients believed to be at high and low risk for pneumonitis were defined based on: (1) MLD; (2) OpRP (sum of predicted perfusion reduction based on regional dose-response curve); and (3) pre-RT DLCO. All doses reflected tissue density heterogeneity. The rates of grade {>=}2 pneumonitis in the 'presumed' high and low risk groups were compared using Fisher's exact test. Results: In the Duke group, pneumonitis rates in patients prospectively deemed to be at 'high' vs. 'low' risk are 7 of 20 and 9 of 35, respectively; p = 0.33 one-tailed Fisher's. Similarly, comparable rates for the NKI group are 4 of 21 and 6 of 44, respectively, p = 0.41 one-tailed Fisher's. Conclusion: The prospective model appears unable to accurately segregate patients into high vs. low risk groups. However, considered retrospectively, these data are consistent with prior studies suggesting that dosimetric (e.g., MLD) and functional (e.g., PFTs or SPECT) parameters are predictive for RT-induced pneumonitis. Additional work is needed to better identify, and prospectively assess, predictors of RT-induced lung injury.

  15. The spectral applications of Beer-Lambert law for some biological and dosimetric materials

    NASA Astrophysics Data System (ADS)

    Içelli, Orhan; Yalçin, Zeynel; Karakaya, Vatan; Ilgaz, Işıl P.

    2014-08-01

    The aim of this study is to conduct quantitative and qualitative analysis of biological and dosimetric materials which contain organic and inorganic materials and to make the determination by using the spectral theorem Beer-Lambert law. Beer-Lambert law is a system of linear equations for the spectral theory. It is possible to solve linear equations with a non-zero coefficient matrix determinant forming linear equations. Characteristic matrix of the linear equation with zero determinant is called point spectrum at the spectral theory.

  16. EPR dosimetric properties of 2-methylalanine pellet for radiation processing application

    NASA Astrophysics Data System (ADS)

    Soliman, Y. S.; Ali, Laila I.; Moustafa, H.; Tadros, Soad M.

    2014-09-01

    The dosimetric characteristics of γ-radiation induced free radicals in 2-methylalanine (2MA) pellet dosimeter are investigated using electron paramagnetic resonance (EPR) in the high-dose range of 1-100 kGy. The EPR spectrum of γ-irradiated 2MA exhibits an isotropic EPR signal with seven lines. The dosimeter response is humidity independent in the range of 33-76% relative humidity. The manufactured dosimeter is typically adipose tissue equivalent in the energy level of 0.1-15 MeV. The overall uncertainty (2σ) of the dosimeter is less than 6.9%.

  17. The revised International Commission on Radiological Protection (ICRP) dosimetric model for the human respiratory tract

    SciTech Connect

    Bair, W.J.

    1992-05-01

    A task group has revised the dosimetric model of the respiratory tract used to calculate annual limits on intake of radionuclides. The revised model can be used to project respiratory tract doses for workers and members of the public from airborne radionuclides and to assess past exposures. Doses calculated for specific extrathoracic and thoracic tissues can be adjusted to account for differences in radiosensitivity and summed to yield two values of dose for the respiratory tract that are applicable to the ICRP tissue weighted dosimetry system.

  18. Dosimetric and kinetic investigations of γ-irradiated sodium tartrate dihydrate.

    PubMed

    Tuner, H; Kayikçi, M A

    2012-03-01

    Effects of gamma radiation on solid sodium tartrate dihydrate (NaTA) were studied using electron spin resonance (ESR) spectroscopy. One main singlet located at g = 2.0034 and many weak lines located at low and high magnetic field sides were found in the irradiated samples. Dosimetric and kinetic features of the radical species responsible for the experimental ESR spectra were explored through the variations in the signal intensities with respect to applied microwave power, temperature and storage time. Activation energies of the involved radical species were also determined using data derived from annealing studies.

  19. Monte Carlo dosimetric study of the Flexisource Co-60 high dose rate source

    PubMed Central

    Granero, Domingo; Perez-Calatayud, Jose; Ballester, Facundo

    2012-01-01

    Purpose Recently, a new HDR 60Co brachytherapy source, Flexisource Co-60, has been developed (Nucletron B.V. Veenendaal, The Netherlands). This study aims to obtain dosimetric data for this source for its use in clinical practice as required by AAPM and ESTRO. Material and methods Two Monte Carlo radiation transport codes were used: Penelope2008 and GEANT4. The source was centrally-positioned in a 100 cm radius water phantom. Absorbed dose and collisional kerma were obtained using 0.01 cm (close) and 0.1 cm (far) sized voxels to provide high-resolution dosimetry near (far from) the source. Dose rate distributions obtained with the two Monte Carlo codes were compared. Results and Discussion Simulations performed with those two radiation transport codes showed an agreement typically within 0.2% for r > 0.8 cm and up to 2% closer to the source. Detailed results of dose distributions are being made available. Conclusions Dosimetric data are provided for the new Flexisource Co-60 source. These data are meant to be used in treatment planning systems in clinical practice. PMID:23346138

  20. A Dosimetric Comparison of Proton and Intensity-Modulated Photon Radiotherapy for Pediatric Parameningeal Rhabdomyosarcomas

    SciTech Connect

    Kozak, Kevin R.; Adams, Judith; Krejcarek, Stephanie J.; Tarbell, Nancy J.; Yock, Torunn I.

    2009-05-01

    Purpose: We compared tumor and normal tissue dosimetry of proton radiation therapy with intensity-modulated radiation therapy (IMRT) for pediatric parameningeal rhabdomyosarcomas (PRMS). Methods and Materials: To quantify dosimetric differences between contemporary proton and photon treatment for pediatric PRMS, proton beam plans were compared with IMRT plans. Ten patients treated with proton radiation therapy at Massachusetts General Hospital had IMRT plans generated. To facilitate dosimetric comparisons, clinical target volumes and normal tissue volumes were held constant. Plans were optimized for target volume coverage and normal tissue sparing. Results: Proton and IMRT plans provided acceptable and comparable target volume coverage, with at least 99% of the CTV receiving 95% of the prescribed dose in all cases. Improved dose conformality provided by proton therapy resulted in significant sparing of all examined normal tissues except for ipsilateral cochlea and mastoid; ipsilateral parotid gland sparing was of borderline statistical significance (p = 0.05). More profound sparing of contralateral structures by protons resulted in greater dose asymmetry between ipsilateral and contralateral retina, optic nerves, cochlea, and mastoids; dose asymmetry between ipsilateral and contralateral parotids was of borderline statistical significance (p = 0.05). Conclusions: For pediatric PRMS, superior normal tissue sparing is achieved with proton radiation therapy compared with IMRT. Because of enhanced conformality, proton plans also demonstrate greater normal tissue dose distribution asymmetry. Longitudinal studies assessing the impact of proton radiotherapy and IMRT on normal tissue function and growth symmetry are necessary to define the clinical consequences of these differences.

  1. Three dimensional dose verification of VMAT plans using the Octavius 4D dosimetric system

    NASA Astrophysics Data System (ADS)

    Arumugam, Sankar; Xing, Aitang; Young, Tony; Thwaites, David; Holloway, Lois

    2015-01-01

    The Octavius 4D dosimetric system generates a 3D dose matrix based on a measured planar dose and user supplied Percentage Depth Dose (PDD) data. The accuracy of 3D dose matrices reconstructed by the Octavius 4D dosimetric system was systematically studied for an open static field, an open arc field and clinical VMAT plans. The Octavius reconstructed 3D dose matrices were compared with the Treatment Planning System (TPS) calculated 3D dose matrices using 3D gamma (γ) analysis with 2%/2mm and 3%/3mm tolerance criteria. The larger detector size in the 2D detector array of the Octavius system resulted in failed voxels in the high dose gradient regions. For the open arc fields mean (1σ) γ pass rates of 84.5(8.9) % and 94.2(4.5) % were observed with 2%/2mm and 3%/3mm tolerance criteria respectively and for clinical VMAT plans mean (1σ) γ pass rates of 86.8(3.5) % and 96.7(1.4) % were observed.

  2. Dosimetric analysis of isocentrically shielded volumetric modulated arc therapy for locally recurrent nasopharyngeal cancer

    PubMed Central

    Lu, Jia-Yang; Huang, Bao-Tian; Xing, Lei; Chang, Daniel T.; Peng, Xun; Xie, Liang-Xi; Lin, Zhi-Xiong; Li, Mei

    2016-01-01

    This study aimed to investigate the dosimetric characteristics of an isocentrically shielded RapidArc (IS-RA) technique for treatment of locally recurrent nasopharyngeal cancer (lrNPC). In IS-RA, the isocenter was placed at the center of the pre-irradiated brainstem (BS)/spinal cord (SC) and the jaws were set to shield the BS/SC while ensuring the target coverage during the whole gantry rotation. For fifteen patients, the IS-RA plans were compared with the conventional RapidArc (C-RA) regarding target coverage, organ-at-risk (OAR) sparing and monitor units (MUs). The relationship between the dose reduction of BS/SC and some geometric parameters including the angle extended by the target with respect to the axis of BS/SC (Ang_BSSC), the minimum distance between the target and BS/SC (Dist_Min) and the target volume were evaluated. The IS-RA reduced the BS/SC doses by approximately 1–4 Gy on average over the C-RA, with more MUs. The IS-RA demonstrated similar target coverage and sparing of other OARs except for slightly improved sparing of optic structures. More dose reduction in the isocentric region was observed in the cases with larger Ang_BSSC or smaller Dist_Min. Our results indicated that the IS-RA significantly improves the sparing of BS/SC without compromising dosimetric requirements of other involved structures for lrNPC. PMID:27173670

  3. Poster — Thur Eve — 74: Distributed, asynchronous, reactive dosimetric and outcomes analysis using DICOMautomaton

    SciTech Connect

    Clark, Haley; Wu, Jonn; Moiseenko, Vitali; Thomas, Steven

    2014-08-15

    Many have speculated about the future of computational technology in clinical radiation oncology. It has been advocated that the next generation of computational infrastructure will improve on the current generation by incorporating richer aspects of automation, more heavily and seamlessly featuring distributed and parallel computation, and providing more flexibility toward aggregate data analysis. In this report we describe how a recently created — but currently existing — analysis framework (DICOMautomaton) incorporates these aspects. DICOMautomaton supports a variety of use cases but is especially suited for dosimetric outcomes correlation analysis, investigation and comparison of radiotherapy treatment efficacy, and dose-volume computation. We describe: how it overcomes computational bottlenecks by distributing workload across a network of machines; how modern, asynchronous computational techniques are used to reduce blocking and avoid unnecessary computation; and how issues of out-of-date data are addressed using reactive programming techniques and data dependency chains. We describe internal architecture of the software and give a detailed demonstration of how DICOMautomaton could be used to search for correlations between dosimetric and outcomes data.

  4. First biological and dosimetric results of the free flyer biostack experiment AO015 on LDEF

    NASA Technical Reports Server (NTRS)

    Reitz, G.; Buecker, H.; Facius, R.; Horneck, G.; Schaeffer, M.; Schott, J. U.; Bayonove, J.; Beaujean, R.; Benton, E. V.; Delpoux, M.

    1991-01-01

    The main objectives of the Biostack Experiment are to study the effectiveness of the structured components of the cosmic radiation to bacterial spores, plant seeds, and animal cysts for a long duration spaceflight and to get dosimetric data such as particle fluences and spectra and total doses for the Long Duration Exposure Facility orbit. The configuration of the experiment packages allows the localization of the trajectory of the particles in each biological layer and to correlate the potential biological impairment or injury with the physical characteristics of the responsible particle. Although the Biostack Experiment was designed for a long duration flight of only nine months, most of the biological systems show a high hatching or germination rate. Some of the first observations are an increase of the mutation rate of embryonic lethals in the second generation of Arabidopsis seeds, somatic mutations, and a reduction of growth rates of corn plants and a reduction of life span of Artemia salina shrimps. The different passive detector systems are also in a good shape and give access to a proper dosimetric analysis. The results are summarized, and some aspects of future analysis are shown.

  5. Technical note: evaluation of dosimetric performance in a commercial 3D treatment planning system.

    PubMed

    Sandilos, P; Seferlis, S; Antypas, C; Karaiskos, P; Dardoufas, C; Vlahos, L

    2005-10-01

    The aim of this work was to evaluate the dosimetric performance of a commercial treatment planning system (TPS) which employs a three-dimensional calculation algorithm (Nucletron Plato version 2.2.3), following the guidelines of the AAPM Task Group 23 (TG23). Seven test cases were used to test the TPS dosimetric performance in homogeneous water. These cases involved absolute dose measurements on central as well as off-axis points situated at various depths, using simple field arrangements, and comparison with corresponding TPS calculations. This comparison yielded differences within +/-2% at all points, for all test cases. To test the ability of the TPS to account for tissue inhomogeneities, corresponding comparisons were performed with the presence of a low-density material in the beam to resemble an air inhomogeneity. Absolute dose measurements and corresponding TPS calculations showed a mean deviation of the order of +/-3.5%, reaching a maximum of 11.5% for small field sizes (5 cm x 5 cm). In summary, observed deviations are well within the set tolerance levels while comparison with previous TPS versions showed that Plato version 2.2.3 is significantly improved, especially in dose calculations in the presence of low density inhomogeneities. PMID:16177012

  6. Breast Conserving Treatment for Breast Cancer: Dosimetric Comparison of Sequential versus Simultaneous Integrated Photon Boost

    PubMed Central

    Reynders, Truus; Heuninckx, Karina; Verellen, Dirk; Storme, Guy; De Ridder, Mark

    2014-01-01

    Background. Breast conserving surgery followed by whole breast irradiation is widely accepted as standard of care for early breast cancer. Addition of a boost dose to the initial tumor area further reduces local recurrences. We investigated the dosimetric benefits of a simultaneously integrated boost (SIB) compared to a sequential boost to hypofractionate the boost volume, while maintaining normofractionation on the breast. Methods. For 10 patients 4 treatment plans were deployed, 1 with a sequential photon boost, and 3 with different SIB techniques: on a conventional linear accelerator, helical TomoTherapy, and static TomoDirect. Dosimetric comparison was performed. Results. PTV-coverage was good in all techniques. Conformity was better with all SIB techniques compared to sequential boost (P = 0.0001). There was less dose spilling to the ipsilateral breast outside the PTVboost (P = 0.04). The dose to the organs at risk (OAR) was not influenced by SIB compared to sequential boost. Helical TomoTherapy showed a higher mean dose to the contralateral breast, but less than 5 Gy for each patient. Conclusions. SIB showed less dose spilling within the breast and equal dose to OAR compared to sequential boost. Both helical TomoTherapy and the conventional technique delivered acceptable dosimetry. SIB seems a safe alternative and can be implemented in clinical routine. PMID:25162031

  7. A simulation study of irregular respiratory motion and its dosimetric impact on lung tumors

    NASA Astrophysics Data System (ADS)

    Mutaf, Y. D.; Scicutella, C. J.; Michalski, D.; Fallon, K.; Brandner, E. D.; Bednarz, G.; Huq, M. S.

    2011-02-01

    This study is aimed at providing a dosimetric evaluation of the irregular motion of lung tumors due to variations in patients' respiration. Twenty-three lung cancer patients are retrospectively enrolled in this study. The motion of the patient clinical target volume is simulated and two types of irregularities are defined: characteristic and uncharacteristic motions. Characteristic irregularities are representative of random fluctuations in the observed target motion. Uncharacteristic irregular motion is classified as systematic errors in determination of the target motion during the planning session. Respiratory traces from measurement of patient abdominal motion are also used for the target motion simulations. Characteristic irregular motion was observed to cause minimal changes in target dosimetry with the largest effect of 2.5% ± 0.9% (1σ) reduction in the minimum target dose (Dmin) observed for targets that move 2 cm on average and exhibiting 50% amplitude variations within a session. However, uncharacteristic irregular motion introduced more drastic changes in the clinical target volume (CTV) dose; 4.1% ± 1.7% reduction for 1 cm motion and 9.6% ± 1.7% drop for 2 cm. In simulations with patients' abdominal motion, corresponding changes in target dosimetry were observed to be negligible (<0.1%). Only uncharacteristic irregular motion was identified as a clinically significant source of dosimetric uncertainty.

  8. Dosimetric comparison of helical tomothearpy and linac-based IMRT in whole abdomen radiotherapy

    NASA Astrophysics Data System (ADS)

    Kang, Young-nam; Kim, Dae-Hyun; Jang, Hong Seok; Song, Jin Ho; Choi, Byung Ock; Cho, Seok Goo; Jung, Ji-Young; Kay, Chul Seung

    2012-10-01

    Recent advances in radiotherapy techniques have allowed a significant improvement in the therapeutic ratio of whole abdominal irradiation (WAI) through linear-accelerator (Linac) based intensity-modulated radiotherapy (IMRT) and helical tomotherapy (HT). IMRT has been shown to reduce the dose to organs at risk (OAR) while adequately treating the tumor volume. HT operates by adjusting 51 beam directions, couch speed, pitch and shapes of a binary multileaf collimator (MLC), with the purpose of clinically increasing the befit to the patient. We incorporated helical tomotherapy as a new modality for WAI for the treatment of non-Hodgkin's lymphoma patients whose disease involved the intestine and the mesenteric lymph nodes. Excellent tumor coverage with effective sparing of normal organ sparings, and homogeneous dose distribution could be achieved. This study dosimetrically compared HT and linac-based IMRT by using several indices, including the conformity index (CI) and the homogeneity index (HI) for the planning target volume (PTV), as well as the, max dose and the mean dose and the quality index (QI) for five organs at risk (OARs). The HI and the CI were used to compare the quality of target coverage while the QI was used compare the dosimetric performans for OAR systems. The target coverages between the two systems were similar, but the most QIs were lower than 1, what means that HT is batter at sparing OARs than IMRT. Tomotherapy enabled excellent target coverage, effective sparing of normal tissues, and homogeneous dose distribution without severe acute toxicity.

  9. [Mathematical simulation support to the dosimetric monitoring on the Russian segment of the International Space Station].

    PubMed

    Mitrikas, V G

    2014-01-01

    To ensure radiation safety of cosmonauts, it is necessary not only to predict, but also to reconstruct absorbed dose dynamics with the knowledge of how long cosmonauts stay in specific space vehicle compartments with different shielding properties and lacking equipment for dosimetric monitoring. In this situation, calculating is one and only way to make a correct estimate of radiation exposure of cosmonaut's organism as a whole (tissue-average dose) and of separate systems and organs. The paper addresses the issues of mathematical simulation of epy radiation environment of standard dosimetric instruments in the Russian segments of the International Space Station (ISS RS). Results of comparing the simulation and experimental data for the complement of dosimeters including ionization chamber-based radiometer R-16, DB8 dosimeters composed of semiconductor detectors, and Pille dosimeters composed of thermoluminescent detectors evidence that the current methods of simulation in support of the ISS RS radiation monitoring provide a sufficiently good agreement between the calculated and experimental data. PMID:25163341

  10. A Combined Tissue Kinetics and Dosimetric Model of Respiratory Tissue Exposed to Radiation

    SciTech Connect

    John R. Ford

    2005-11-01

    Existing dosimetric models of the radiation response of tissues are essentially static. Consideration of changes in the cell populations over time has not been addressed realistically. For a single acute dose this is not a concern, but for modeling chronic exposures or fractionated acute exposures, the natural turnover and progression of cells could have a significant impact on a variety of endpoints. This proposal addresses the shortcomings of current methods by combining current dose-based calculation techniques with information on the cell turnover for a model tissue. The proposed model will examine effects at the single-cell level for an exposure of a section of human bronchiole. The cell model will be combined with Monte Carlo calculations of doses to cells and cell nuclei due to varying dose-rates of different radiation qualities. Predictions from the model of effects on survival, apoptosis rates, and changes in the number of cycling and differentiating cells will be tested experimentally. The availability of dynamic dosimetric models of tissues at the single-cell level will be useful for analysis of low-level radiation exposures and in the development of new radiotherapy protocols.

  11. The Dosimetric Impact of Prostate Rotations During Electromagnetically Guided External-Beam Radiation Therapy

    SciTech Connect

    Amro, Hanan; Hamstra, Daniel A.; Mcshan, Daniel L.; Sandler, Howard; Vineberg, Karen; Hadley, Scott; Litzenberg, Dale

    2013-01-01

    Purpose: To study the impact of daily rotations and translations of the prostate on dosimetric coverage during radiation therapy (RT). Methods and Materials: Real-time tracking data for 26 patients were obtained during RT. Intensity modulated radiation therapy plans meeting RTOG 0126 dosimetric criteria were created with 0-, 2-, 3-, and 5-mm planning target volume (PTV) margins. Daily translations and rotations were used to reconstruct prostate delivered dose from the planned dose. D{sub 95} and V{sub 79} were computed from the delivered dose to evaluate target coverage and the adequacy of PTV margins. Prostate equivalent rotation is a new metric introduced in this study to quantify prostate rotations by accounting for prostate shape and length of rotational lever arm. Results: Large variations in prostate delivered dose were seen among patients. Adequate target coverage was met in 39%, 65%, and 84% of the patients for plans with 2-, 3-, and 5-mm PTV margins, respectively. Although no correlations between prostate delivered dose and daily rotations were seen, the data showed a clear correlation with prostate equivalent rotation. Conclusions: Prostate rotations during RT could cause significant underdosing even if daily translations were managed. These rotations should be managed with rotational tolerances based on prostate equivalent rotations.

  12. Role of intracanalicular volumetric and dosimetric parameters on hearing preservation after vestibular schwannoma radiosurgery

    SciTech Connect

    Massager, Nicolas . E-mail: nmassage@ulb.ac.be; Nissim, Ouzi; Delbrouck, Carine; Devriendt, Daniel; David, Philippe; Desmedt, Francoise; Wikler, David; Hassid, Sergio; Brotchi, Jacques; Levivier, Marc

    2006-04-01

    Purpose: To analyze the relationship between hearing preservation after gamma knife radiosurgery (GKR) for vestibular schwannoma (VS) and some volumetric and dosimetric parameters of the intracanalicular components of VS. Methods and Materials: This study included 82 patients with a VS treated by GKR; all patients had no NF2 disease, a Gardner-Robertson hearing class 1-4 before treatment, a marginal dose of 12 Gy, and a radiologic and audiologic follow-up {>=}1 year post-GKR. The volume of both the entire tumor and the intracanalicular part of the tumor and the mean and integrated dose of these two volumes were correlated to the auditory outcomes of patients. Results: At last hearing follow-up, 52 patients had no hearing worsening, and 30 patients had an increase of {>=}1 class on Gardner-Robertson classification. We found that hearing preservation after GKR is significantly correlated with the intracanalicular tumor volume, as well as with the integrated dose delivered to the intracanalicular tumor volume. Conclusions: Some volumetric and dosimetric parameters of the intracanalicular part of the tumor influence hearing preservation after GKR of VS. Consequently, we advise the direct treatment of patients with preserved functional hearing and a VS including a small intracanalicular volume.

  13. Revision of the ICRP dosimetric model for the human respiratory tract

    SciTech Connect

    Bair, W.J.

    1990-12-01

    Although the dosimetric model of the respiratory tract used in ICRP Publication 30 had not been shown to be seriously deficient for the purpose of calculating Annual Limits on Intake (ALIs) for workers, the availability of new information led the ICRP in 1984 to create a special Task Group to review the dosimetric model of the respiratory tract and, if justified, propose revisions or a new model. The Task Group directed its efforts toward improving the model used in Publication 30 rather than developing a completely new model. The objective was a model that would facilitate calculation of biologically meaningful doses; be consistent with morphological, physiological, and radiobiological characteristics of the respiratory tract; incorporate current knowledge; meet all radiation protection needs; be user friendly by not being unnecessarily sophisticated; be adaptable to development of computer software for calculation of relevant radiation doses from knowledge of a few readily measured exposure parameters; be equally useful for assessment purposes as for calculating ALIs; be applicable to all members of the world population; and consider the influence of smoking, air pollutants, and diseases of the inhalation, deposition, and clearance of radioactive particles from the respiratory tract. The model provides for calculation of a committed dose equivalent for each region, adjusted for the relative cancer sensitivity of that region, and for the summing of these to yield a committed dose equivalent for the entire respiratory tract. 3 figs.

  14. A Dosimetric Analysis of IMRT and Multistatic Fields Techniques for Left Breast Radiotherapy

    SciTech Connect

    Moon, Seong Kwon; Kim, Yeon Sil; Kim, Soo Young; Lee, Mi Jo; Keum, Hyun Sup; Kim, Seung Jin; Youn, Seon Min

    2011-10-01

    The purpose of this study was to analyze the dosimetric difference between intensity-modulated radiation therapy (IMRT) using 3 or 5 beams and multistatic field technique (MSF) in radiotherapy of the left breast. We made comparative analysis of two kinds of radiotherapy that can achieve improved dose homogeneity. First is a MSF that uses both major and small irradiation fields at the same time. The other is IMRT using 3 or 5 beams with an inverse planning system using multiple static multileaf collimators. We made treatment plans for 16 early left breast cancer patients who were randomly selected and had undergone breast conserving surgery and radiotherapy, and analyzed them in the dosimetric aspect. For the mean values of V{sub 95} and dose homogeneity index, no statistically significant difference was observed among the three therapies. Extreme hot spots receiving >110% of prescribed dose were not found in any of the three methods. Using Tukey's test, IMRT showed a significantly larger increase in exposure dose to the ipsilateral lung and the heart than MSF in the low-dose area, but in the high-dose area, MSF showed a slight increase. To improve dose homogeneity, the application of MSF, which can be easily planned and applied more widely, is considered optimal as an alternative to IMRT for radiotherapy of early left breast cancer.

  15. Basics of particle therapy II biologic and dosimetric aspects of clinical hadron therapy.

    PubMed

    Rong, Yi; Welsh, James

    2010-12-01

    Besides photons and electrons, high-energy particles like protons, neutrons, ⁴He ions or heavier ions (C, Ne, etc) have been finding increasing applications in the treatment of radioresistant tumors and tumors located near critical structures. The main difference between photons and hadrons is their different biologic effect and depth-dose distribution. Generally speaking, protons are superior in dosimetric aspects whereas neutrons have advantages in biologic effectiveness because of the high linear energy transfer. In 1946 Robert Wilson first published the physical advantages in dose distribution of ion particles for cancer therapy. Since that time hadronic radiotherapy has been intensively studied in physics laboratories worldwide and clinical application have gradually come to fruition. Hadron therapy was made possible by the advances in accelerator technology, which increases the particles' energy high enough to place them at any depth within the patient's body. As a follow-up to the previous article Introduction to Hadrons, this review discusses certain biologic and dosimetric aspects of using protons, neutrons, and heavy charged particles for radiation therapy. PMID:20395789

  16. Synthesis and characterization of CaF{sub 2}:Dy nanophosphor for dosimetric application

    SciTech Connect

    Bhadane, Mahesh S.; Dahiwale, S. S.; Bhoraskar, V. N.; Dhole, S. D.; Patil, B. J.; Kulkarni, M. S.; Bhatt, B. C.

    2015-06-24

    In this work, nanoparticles (NPs) of dysprosium doped calcium fluoride (CaF{sub 2}: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 CaF{sub 2}: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 CaF{sub 2}: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 CaF{sub 2}:Dy nanophosphor as a function of gamma dose is very useful from radiation dosimetric point of view.

  17. Thermoluminescent dosimetric properties of CaF2:Tm produced by combustion synthesis

    NASA Astrophysics Data System (ADS)

    de Vasconcelos, D. A. A.; Barros, V. S. M.; Khoury, H. J.; Asfora, V. K.; Oliveira, R. A. P.

    2016-04-01

    Calcium Fluoride is one of the oldest known thermoluminescent materials and is considered to be one of the most sensitive. This work presents the dosimetric properties results of CaF2:Tm produced by combustion synthesis. The X-ray diffraction confirmed that CaF2 was successfully produced. TL emission spectra, obtained using a Hammamatsu optical spectrometer, have the same lines of commercial CaF2:Tm, although transitions 3P0→3F4 (455 nm) and 1G4→3H6 (482 nm) are shown to be proportionally more intense. The deconvolution technique was employed and seven glow peaks were found similar to the commercial CaF2:Tm. A linear dose response curve was obtained for the range 0.1 mGy to 100 Gy, with the onset of a supralinear behavior at 50 Gy up to 100 Gy. The minimum measurable dose for gamma was around 100 μGy for a 6.0 mm diameter by 1.0 mm in thickness pellet. No significant fading was observed in 60 days of storage, within experimental uncertainties, showing that the main dosimetric peak is stable.

  18. Dosimetric characteristics of fabricated silica fibre for postal radiotherapy dose audits

    NASA Astrophysics Data System (ADS)

    Fadzil, M. S. Ahmad; Ramli, N. N. H.; Jusoh, M. A.; Kadni, T.; Bradley, D. A.; Ung, N. M.; Suhairul, H.; Mohd Noor, N.

    2014-11-01

    Present investigation aims to establish the dosimetric characteristics of a novel fabricated flat fibre TLD system for postal radiotherapy dose audits. Various thermoluminescence (TL) properties have been investigated for five sizes of 6 mol% Ge-doped optical fibres. Key dosimetric characteristics including reproducibility, linearity, fading and energy dependence have been established. Irradiations were carried out using a linear accelerator (linac) and a Cobalt-60 machine. For doses from 0.5 Gy up to 10 Gy, Ge-doped flat fibres exhibit linearity between TL yield and dose, reproducible to better than 8% standard deviation (SD) following repeat measurements (n = 3). For photons generated at potentials from 1.25 MeV to 10 MV an energy-dependent response is noted, with a coefficient of variation (CV) of less than 40% over the range of energies investigated. For 6.0 mm length flat fibres 100 μm thick × 350 pm wide, the TL fading loss following 30 days of storage at room temperature was < 8%. The Ge-doped flat fibre system represents a viable basis for use in postal radiotherapy dose audits, corrections being made for the various factors influencing the TL yield.

  19. [Mathematical simulation support to the dosimetric monitoring on the Russian segment of the International Space Station].

    PubMed

    Mitrikas, V G

    2014-01-01

    To ensure radiation safety of cosmonauts, it is necessary not only to predict, but also to reconstruct absorbed dose dynamics with the knowledge of how long cosmonauts stay in specific space vehicle compartments with different shielding properties and lacking equipment for dosimetric monitoring. In this situation, calculating is one and only way to make a correct estimate of radiation exposure of cosmonaut's organism as a whole (tissue-average dose) and of separate systems and organs. The paper addresses the issues of mathematical simulation of epy radiation environment of standard dosimetric instruments in the Russian segments of the International Space Station (ISS RS). Results of comparing the simulation and experimental data for the complement of dosimeters including ionization chamber-based radiometer R-16, DB8 dosimeters composed of semiconductor detectors, and Pille dosimeters composed of thermoluminescent detectors evidence that the current methods of simulation in support of the ISS RS radiation monitoring provide a sufficiently good agreement between the calculated and experimental data.

  20. Dosimetric validation of a commercial Monte Carlo based IMRT planning system

    SciTech Connect

    Grofsmid, Dennis; Dirkx, Maarten; Marijnissen, Hans; Woudstra, Evert; Heijmen, Ben

    2010-02-15

    Purpose: Recently a commercial Monte Carlo based IMRT planning system (Monaco version 1.0.0) was released. In this study the dosimetric accuracy of this new planning system was validated. Methods: Absolute dose profiles, depth dose curves, and output factors calculated by Monaco were compared with measurements in a water phantom. Different static on-axis and off-axis fields were tested at various source-skin distances for 6, 10, and 18 MV photon beams. Four clinical IMRT plans were evaluated in a water phantom using a linear diode detector array and another six IMRT plans for different tumor sites in solid water using a 2D detector array. In order to evaluate the accuracy of the dose engine near tissue inhomogeneities absolute dose distributions were measured with Gafchromic EBT film in an inhomogeneous slab phantom. For an end-to-end test a four-field IMRT plan was applied to an anthropomorphic lung phantom with a simulated tumor peripherally located in the right lung. Gafchromic EBT film, placed in and around the tumor area, was used to evaluate the dose distribution. Results: Generally, the measured and the calculated dose distributions agreed within 2% dose difference or 2 mm distance-to-agreement. But mainly at interfaces with bone, some larger dose differences could be observed. Conclusions: Based on the results of this study, the authors concluded that the dosimetric accuracy of Monaco is adequate for clinical introduction.

  1. Dosimetric characterisation of aqueous solution of brilliant green for low-dose food irradiation dosimetry

    NASA Astrophysics Data System (ADS)

    Khan, Hasan M.; Anwer, Mohammad; Chaudhry, Zahid S.

    2002-03-01

    Dosimetric characterisation of aqueous solution of brilliant green has been studied spectrophotometrically for possible applications in low-dose food irradiation dosimetry. Absorption spectra of unirradiated and irradiated solutions were determined which showed two absorption bands with peaks at 427 and 626 nm and a decrease in absorption as the radiation dose is increased. Radiation-induced bleaching of the dye was measured at wavelengths of maximum absorbance (427 and 626 nm) as well as at 550 and 570 nm. At all these wavelengths, the decrease in absorbance of the dosimeter was linear with respect to the absorbed dose from 20 to 120 Gy. However, the upper dose limit was increased to 200 Gy when the negative logarithm of the absorbance ( - log A ) was plotted versus absorbed dose. The stability of dosimetric solution during post-irradiation storage in dark at room temperature showed that after some initial bleaching within the first 5 h of irradiation the response was stable for about 18 days. The effect of different light and temperature conditions to which a dosimeter may be exposed during commercial irradiation has been discussed.

  2. TL dosimetric properties of Li2O-B2O3 glasses for gamma dosimetry.

    PubMed

    El-Adawy, A; Khaled, N E; El-Sersy, A R; Hussein, A; Donya, H

    2010-06-01

    In this work, the thermoluminescence (TL) dosimetric characteristics of lithium borate glasses have been studied in detail before and after doping with silver. The glass specimens were prepared using a conventional melt-quenching method and checked using X-ray diffraction (XRD) pattern. The resultant glow curve of the undoped gamma-irradiated samples showed one strong peak at about 178 degrees C and at a constant heating-rate (beta) of 5 degrees C/s. While, the Ag-doped samples showed two TL glow peaks around 220 and 320 degrees C, which were mainly attributed to the Ag(+) ions. Trap parameters of glow peaks of the present glass systems were extracted. The dosimetric characteristics of glass specimens were read from the TL gamma-dose response curve, which showed a reasonably good linearity behavior between glow peak areas and gamma-dose values. The present results revealed the importance of using such current selective glass structures as gamma-radiation detectors within the studied dose-range where an acceptably good fading response was observed. PMID:20122841

  3. Mole Mapping.

    ERIC Educational Resources Information Center

    Crippen, Kent J.; Curtright, Robert D.; Brooks, David W.

    2000-01-01

    The abstract nature of the mole and its applications to problem solving make learning the concept difficult for students, and teaching the concept challenging for teachers. Presents activities that use concept maps and graphing calculators as tools for solving mole problems. (ASK)

  4. Memphis Maps.

    ERIC Educational Resources Information Center

    Hyland, Stanley; Cox, David; Martin, Cindy

    1998-01-01

    The Memphis Maps program, a collaborative effort of Memphis (Tennessee) educational institutions, public agencies, a bank, and community programs, trains local students in Geographic Information Systems technology and provides the community with valuable demographic and assessment information. The program is described, and factors contributing to…

  5. 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

  6. Monte Carlo radiation dose simulations and dosimetric comparison of the model 6711 and 9011 {sup 125}I brachytherapy sources

    SciTech Connect

    Rivard, Mark J.

    2009-02-15

    Smaller diameter brachytherapy seeds for permanent interstitial implantation allow for use of smaller diameter implant needles. The use of smaller diameter needles may provide a lower incidence of healthy-tissue complications. This study determines the brachytherapy dosimetry parameters for the smaller diameter source (model 9011) and comments on the dosimetric comparison between this new source and the conventional brachytherapy seed (model 6711).

  7. Dosimetric effects of multileaf collimator leaf width on intensity-modulated radiotherapy for head and neck cancer

    SciTech Connect

    Hong, Chae-Seon; Ju, Sang Gyu Kim, Minkyu; Kim, Jin Man; Han, Youngyih; Ahn, Yong Chan; Choi, Doo Ho; Park, Hee Chul; Kim, Jung-in; Nam, Heerim; Suh, Tae-Suk

    2014-02-15

    Purpose: The authors evaluated the effects of multileaf collimator (MLC) leaf width (2.5 vs. 5 mm) on dosimetric parameters and delivery efficiencies of intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) for head and neck (H and N) cancers. Methods: The authors employed two types of mock phantoms: large-sized head and neck (LH and N) and small-sized C-shape (C-shape) phantoms. Step-and-shoot IMRT (S and S-IMRT) and VMAT treatment plans were designed with 2.5- and 5.0-mm MLC for both C-shape and LH and N phantoms. Their dosimetric characteristics were compared in terms of the conformity index (CI) and homogeneity index (HI) for the planning target volume (PTV), the dose to organs at risk (OARs), and the dose-spillage volume. To analyze the effects of the field and arc numbers, 9-field IMRT (9F-IMRT) and 13-field IMRT (13F-IMRT) plans were established for S and S-IMRT. For VMAT, single arc (VMAT{sub 1}) and double arc (VMAT{sub 2}) plans were established. For all plans, dosimetric verification was performed using the phantom to examine the relationship between dosimetric errors and the two leaf widths. Delivery efficiency of the two MLCs was compared in terms of beam delivery times, monitor units (MUs) per fraction, and the number of segments for each plan. Results: 2.5-mm MLC showed better dosimetric characteristics in S and S-IMRT and VMAT for C-shape, providing better CI for PTV and lower spinal cord dose and high and intermediate dose-spillage volume as compared with the 5-mm MLC (p < 0.05). However, no significant dosimetric benefits were provided by the 2.5-mm MLC for LH and N (p > 0.05). Further, beam delivery efficiency was not observed to be significantly associated with leaf width for either C-shape or LH and N. However, MUs per fraction were significantly reduced for the 2.5-mm MLC for the LH and N. In dosimetric error analysis, absolute dose evaluations had errors of less than 3%, while the Gamma passing rate was

  8. Map projections

    USGS Publications Warehouse

    ,

    1993-01-01

    A map projection is used to portray all or part of the round Earth on a flat surface. This cannot be done without some distortion. Every projection has its own set of advantages and disadvantages. There is no "best" projection. The mapmaker must select the one best suited to the needs, reducing distortion of the most important features. Mapmakers and mathematicians have devised almost limitless ways to project the image of the globe onto paper. Scientists at the U. S. Geological Survey have designed projections for their specific needs—such as the Space Oblique Mercator, which allows mapping from satellites with little or no distortion. This document gives the key properties, characteristics, and preferred uses of many historically important projections and of those frequently used by mapmakers today.

  9. Adaptive optimization by 6 DOF robotic couch in prostate volumetric IMRT treatment: rototranslational shift and dosimetric consequences.

    PubMed

    Chiesa, Silvia; 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 < 5 mm 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.

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

    SciTech Connect

    Wang, J; Zhao, K; Peng, J; Hu, W; Jin, X

    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) was 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.

  11. Multi-institutional dosimetric and geometric commissioning of image-guided small animal irradiators

    SciTech Connect

    Lindsay, P. E.; Granton, P. V.; Hoof, S. van; Hermans, J.; Gasparini, A.; Jelveh, S.; Clarkson, R.; Kaas, J.; Wittkamper, F.; Sonke, J.-J.; Verhaegen, F.; Jaffray, D. A.

    2014-03-15

    Purpose: To compare the dosimetric and geometric properties of a commercial x-ray based image-guided small animal irradiation system, installed at three institutions and to establish a complete and broadly accessible commissioning procedure. Methods: The system consists of a 225 kVp x-ray tube with fixed field size collimators ranging from 1 to 44 mm equivalent diameter. The x-ray tube is mounted opposite a flat-panel imaging detector, on a C-arm gantry with 360° coplanar rotation. Each institution performed a full commissioning of their system, including half-value layer, absolute dosimetry, relative dosimetry (profiles, percent depth dose, and relative output factors), and characterization of the system geometry and mechanical flex of the x-ray tube and detector. Dosimetric measurements were made using Farmer-type ionization chambers, small volume air and liquid ionization chambers, and radiochromic film. The results between the three institutions were compared. Results: At 225 kVp, with 0.3 mm Cu added filtration, the first half value layer ranged from 0.9 to 1.0 mm Cu. The dose-rate in-air for a 40 × 40 mm{sup 2} field size, at a source-to-axis distance of 30 cm, ranged from 3.5 to 3.9 Gy/min between the three institutions. For field sizes between 2.5 mm diameter and 40 × 40 mm{sup 2}, the differences between percent depth dose curves up to depths of 3.5 cm were between 1% and 4% on average, with the maximum difference being 7%. The profiles agreed very well for fields >5 mm diameter. The relative output factors differed by up to 6% for fields larger than 10 mm diameter, but differed by up to 49% for fields ≤5 mm diameter. The mechanical characteristics of the system (source-to-axis and source-to-detector distances) were consistent between all three institutions. There were substantial differences in the flex of each system. Conclusions: With the exception of the half-value layer, and mechanical properties, there were significant differences between the

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

    SciTech Connect

    Park, J; Xu, Q; Xue, J; Zhai, Y; An, L; Chen, Y

    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 with 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.

  13. Dosimetric Evaluation of Different Intensity-Modulated Radiotherapy Techniques for Breast Cancer After Conservative Surgery.

    PubMed

    Zhang, Fuli; Wang, Yadi; Xu, Weidong; Jiang, Huayong; Liu, Qingzhi; Gao, Junmao; Yao, Bo; Hou, Jun; He, Heliang

    2015-10-01

    Intensity-modulated radiotherapy (IMRT) potentially leads to a more favorite dose distribution compared to 3-dimensional or conventional tangential radiotherapy (RT) for breast cancer after conservative surgery or mastectomy. The aim of this study was to compare dosimetric parameters of the planning target volume (PTV) and organs at risk (OARs) among helical tomotherapy (HT), inverse-planned IMRT (IP-IMRT), and forward-planned field in field (FP-FIF) IMRT techniques after breast-conserving surgery. Computed tomography scans from 20 patients (12 left sided and 8 right sided) previously treated with T1N0 carcinoma were selected for this dosimetric planning study. We designed HT, IP-IMRT, and FP-FIF plans for each patient. Plans were compared according to dose-volume histogram analysis in terms of PTV homogeneity and conformity indices (HI and CI) as well as OARs dose and volume parameters. Both HI and CI of the PTV showed statistically significant difference among IP-IMRT, FP-FIF, and HT with those of HT were best (P < .05). Compared to FP-FIF, IP-IMRT showed smaller exposed volumes of ipsilateral lung, heart, contralateral lung, and breast, while HT indicated smaller exposed volumes of ipsilateral lung but larger exposed volumes of contralateral lung and breast as well as heart. In addition, HT demonstrated an increase in exposed volume of ipsilateral lung (except for fraction of lung volume receiving >30 Gy and 20 Gy), heart, contralateral lung, and breast compared with IP-IMRT. For breast cancer radiotherapy (RT) after conservative surgery, HT provides better dose homogeneity and conformity of PTV compared to IP-IMRT and FP-FIF techniques, especially for patients with supraclavicular lymph nodes involved. Meanwhile, HT decreases the OAR volumes receiving higher doses with an increase in the volumes receiving low doses, which is known to lead to an increased rate of radiation-induced secondary malignancies. Hence, composite factors including dosimetric advantage

  14. A dosimetric evaluation of VMAT for the treatment of non-small cell lung cancer.

    PubMed

    Merrow, Caitlin E; Wang, Iris Z; Podgorsak, Matthew B

    2012-09-01

    The purpose of this study was to demonstrate the dosimetric potential of volumetric-modulated arc therapy (VMAT) for the treatment of patients with medically inoperable stage I/II non-small cell lung cancer (NSCLC) with stereotactic body radiation therapy (SBRT). Fourteen patients treated with 3D CRT with varying tumor locations, tumor sizes, and dose fractionation schemes were chosen for study. The prescription doses were 48 Gy in 4 fractions, 52.5 Gy in 5 fractions, 57.5 Gy in 5 fractions, and 60 Gy in 3 fractions for 2, 5, 1, and 6 patients, respectively. VMAT treatment plans with a mix of two to three full and partial noncoplanar arcs with 5°-25° separations were retrospectively generated using Eclipse version 10.0. The 3D CRT and VMAT plans were then evaluated by comparing their target dose, critical structure dose, high dose spillage, and low dose spillage as defined according to RTOG 0813 and RTOG 0236 protocols. In the most dosimetrically improved case, VMAT was able to decrease the dose from 17.35 Gy to 1.54 Gy to the heart. The D(2cm) decreased in 11 of 14 cases when using VMAT. The three that worsened were still within the acceptance criteria. Of the 14 3D CRT plans, seven had a D(2cm) minor deviation, while only one of the 14 VMAT plans had a D(2cm) minor deviation. The R(50%) improved in 13 of the 14 VMAT cases. The one case that worsened was still within the acceptance criteria of the RTOG protocol. Of the 14 3D CRT plans, seven had an R(50%) deviation. Only one of the 14 VMAT plans had an R(50%) deviation, but it was still improved compared to the 3D CRT plan. In this cohort of patients, no evident dosimetric compromises resulted from planning SBRT treatments with VMAT relative to the 3D CRT treatment plans actually used in their treatment.

  15. Dosimetric advantages of IMPT over IMRT for laser-accelerated proton beams

    NASA Astrophysics Data System (ADS)

    Luo, W.; Li, J.; Fourkal, E.; Fan, J.; Xu, X.; Chen, Z.; Jin, L.; Price, R.; Ma, C.-M.

    2008-12-01

    As a clinical application of an exciting scientific breakthrough, a compact and cost-efficient proton therapy unit using high-power laser acceleration is being developed at Fox Chase Cancer Center. The significance of this application depends on whether or not it can yield dosimetric superiority over intensity-modulated radiation therapy (IMRT). The goal of this study is to show how laser-accelerated proton beams with broad energy spreads can be optimally used for proton therapy including intensity-modulated proton therapy (IMPT) and achieve dosimetric superiority over IMRT for prostate cancer. Desired energies and spreads with a varying δE/E were selected with the particle selection device and used to generate spread-out Bragg peaks (SOBPs). Proton plans were generated on an in-house Monte Carlo-based inverse-planning system. Fifteen prostate IMRT plans previously used for patient treatment have been included for comparison. Identical dose prescriptions, beam arrangement and consistent dose constrains were used for IMRT and IMPT plans to show the dosimetric differences that were caused only by the different physical characteristics of proton and photon beams. Different optimization constrains and beam arrangements were also used to find optimal IMPT. The results show that conventional proton therapy (CPT) plans without intensity modulation were not superior to IMRT, but IMPT can generate better proton plans if appropriate beam setup and optimization are used. Compared to IMRT, IMPT can reduce the target dose heterogeneity ((D5-D95)/D95) by up to 56%. The volume receiving 65 Gy and higher (V65) for the bladder and the rectum can be reduced by up to 45% and 88%, respectively, while the volume receiving 40 Gy and higher (V40) for the bladder and the rectum can be reduced by up to 49% and 68%, respectively. IMPT can also reduce the whole body non-target tissue dose by up to 61% or a factor 2.5. This study has shown that the laser accelerator under development has a

  16. Dosimetric properties of an amorphous silicon EPID for verification of modulated electron radiotherapy

    SciTech Connect

    Chatelain, Cecile; Vetterli, Daniel; Henzen, Dominik; Favre, Pascal; Fix, Michael K.; Manser, Peter; Morf, Daniel; Scheib, Stefan

    2013-06-15

    Purpose: To investigate the dosimetric properties of an electronic portal imaging device (EPID) for electron beam detection and to evaluate its potential for quality assurance (QA) of modulated electron radiotherapy (MERT). Methods: A commercially available EPID was used to detect electron beams shaped by a photon multileaf collimator (MLC) at a source-surface distance of 70 cm. The fundamental dosimetric properties such as reproducibility, dose linearity, field size response, energy response, and saturation were investigated for electron beams. A new method to acquire the flood-field for the EPID calibration was tested. For validation purpose, profiles of open fields and various MLC fields (square and irregular) were measured with a diode in water and compared to the EPID measurements. Finally, in order to use the EPID for QA of MERT delivery, a method was developed to reconstruct EPID two-dimensional (2D) dose distributions in a water-equivalent depth of 1.5 cm. Comparisons were performed with film measurement for static and dynamic monoenergy fields as well as for multienergy fields composed by several segments of different electron energies. Results: The advantageous EPID dosimetric properties already known for photons as reproducibility, linearity with dose, and dose rate were found to be identical for electron detection. The flood-field calibration method was proven to be effective and the EPID was capable to accurately reproduce the dose measured in water at 1.0 cm depth for 6 MeV, 1.3 cm for 9 MeV, and 1.5 cm for 12, 15, and 18 MeV. The deviations between the output factors measured with EPID and in water at these depths were within {+-}1.2% for all the energies with a mean deviation of 0.1%. The average gamma pass rate (criteria: 1.5%, 1.5 mm) for profile comparison between EPID and measurements in water was better than 99% for all the energies considered in this study. When comparing the reconstructed EPID 2D dose distributions at 1.5 cm depth to film

  17. Dosimetric comparison between model 9011 and 6711 sources in prostate implants

    SciTech Connect

    Zhang, Hualin; Beyer, David

    2013-07-01

    The purpose of this work is to evaluate the model 9011 iodine-125 ({sup 125}I) in prostate implants by comparing dosimetric coverage provided by the 6711 vs 9011 source implants. Postimplant dosimetry was performed in 18 consecutively implanted patients with prostate cancer. Two were implanted with the 9011 source and 16 with the 6711 source. For purposes of comparison, each implant was then recalculated assuming use of the other source. The same commercially available planning system was used and the specific source data for both 6711 and 9011 products were entered. The results of these calculations are compared side by side in the terms of the isodose values covering 100% (D100) and 90% (D90) of prostate volume, and the percentages of volumes of prostate, bladder, rectum, and urethra covered by 200% (V200), 150% (V150), 100% (V100), 50% (V50), and 20% (V20) of the prescribed dose as well. The 6711 source data overestimate coverage by 6.4% (ranging from 4.9% to 6.9%; median 6.6%) at D100 and by 6.6% (ranging from 6.2% to 6.8%; median 6.6%) at D90 compared with actual 9011 data. Greater discrepancies of up to 67% are seen at higher dose levels: average reduction for V100 is 2.7% (ranging from 0.6% to 7.7%; median 2.3%), for V150 is 14.6% (ranging from 6.1% to 20.5%; median 15.3%), for V200 is 14.9% (ranging from 4.8% to 19.1%; median 16%); similarly seen in bladder, rectal, and urethral coverage. This work demonstrates a clear difference in dosimetric behavior between the 9011 and 6711 sources. Using the 6711 source data for 9011 source implants would create a pronounced error in dose calculation. This study provides evidence that the 9011 source can provide the same dosimetric quality as the 6711 source, if properly used; however, the 6711 source data should not be considered as a surrogate for the 9011 source implants.

  18. Dosimetric evaluation of a three-phase adaptive radiotherapy for nasopharyngeal carcinoma using helical tomotherapy

    SciTech Connect

    Fung, Winky Wing Ki; Wu, Vincent Wing Cheung; Teo, Peter Man Lung

    2012-04-01

    Adaptive radiotherapy (ART) has been introduced to correct the radiation-induced anatomic changes in head and neck cases during a treatment course. This study evaluated the potential dosimetric benefits of applying a 3-phase adaptive radiotherapy protocol in nasopharyngeal carcinoma (NPC) patients compared with the nonadaptive single-phase treatment protocol. Ten NPC patients previously treated with this 3-phase radiation protocol using Hi-Art Tomotherapy were recruited. Two new plans, PII-ART and PIII-ART, were generated based on the up-to-date computed tomography (CT) images and contours and were used for treatment in phase two (PII; after 25th fraction) and phase three (PIII; after 35th fraction), respectively. To simulate the situation of no replanning, 2 hybrid plans denoted as PII-NART and PIII-NART were generated using the original contours pasted on the PII- and PIII-CT sets by CT-CT fusion. Dosimetric comparisons were made between the NART plans and the corresponding ART plans. In both PII- and PIII-NART plans, the doses to 95% of all the target volumes (D{sub 95}) were increased with better dose uniformity, whereas the organs at risk (OARs) received higher doses compared with the corresponding ART plans. Without replanning, the total dose to 1% of brainstem and spinal cord (D{sub 1}) significantly increased 7.87 {+-} 7.26% and 10.69 {+-} 6.72%, respectively (P = 0.011 and 0.001, respectively), in which 3 patients would have these structures overdosed when compared with those with two replannings. The total maximum doses to the optic chiasm and pituitary gland and the mean doses to the left and right parotid glands were increased by 10.50 {+-} 10.51%, 8.59 {+-} 6.10%, 3.03 {+-} 4.48%, and 2.24 {+-} 3.11%, respectively (P = 0.014, 0.003, 0.053, and 0.046, respectively). The 3-phase radiotherapy protocol showed improved dosimetric results to the critical structures while keeping satisfactory target dose coverage, which demonstrated the advantages of ART in

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

    SciTech Connect

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

    2014-01-15

    Purpose: 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. Methods: 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. Results: 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 Rapid

  20. Dosimetric investigation of the solar erythemal UV radiation protection provided by beards and moustaches.

    PubMed

    Parisi, A V; Turnbull, D J; Downs, N; Smith, D

    2012-07-01

    A dosimetric technique has been employed to establish the amount of erythemal ultraviolet radiation (UVR) protection provided by facial hair considering the influence of solar zenith angle (SZA) and beard-moustache length. The facial hair reduced the exposure ratios (ERs) to approximately one-third of those to the sites with no hair. The variation in the ERs over the different sites was reduced compared with the cases with no beard. The ultraviolet protection factor (UPF) provided by the facial hair ranged from 2 to 21. The UPF decreases with increasing SZA. The minimum UPF was in the 53-62° range. The longer hair provides a higher UPF at the smaller SZA, but the difference between the protection provided by the longer hair compared with the shorter hair reduces with increasing SZA. Protection from UVR is provided by the facial hair; however, it is not very high, particularly at the higher SZA.

  1. The Dosimetric Parameters Investigation of the Pulsed X-ray and Gamma Radiation Sources

    NASA Astrophysics Data System (ADS)

    Stuchebrov, S. G.; Miloichikova, I. A.; Shilova, X. O.

    2016-01-01

    The most common type of radiation used for diagnostic purposes are X-rays. However, X-rays methods have limitations related to the radiation dose for the biological objects. It is known that the use of the pulsed emitting source synchronized with the detection equipment for internal density visualization of objects significant reduces the radiation dose to the object. In the article the analysis of the suitability of the different dosimetric equipment for the radiation dose estimation of the pulsed emitting sources is carried out. The approbation results on the pulsed X-ray generator RAP-160-5 of the dosimetry systems workability with the pulse radiation and its operation range are presented. The results of the dose field investigation of the portable betatron OB-4 are demonstrated. The depth dose distribution in the air, lead and water of the pulsed bremsstrahlung generated by betatron are shown.

  2. Dosimetric verification of modulated photon fields by means of compensators for a kernel model.

    PubMed

    Weber, Lars; Laursen, Finn

    2002-01-01

    The approach in treatment planning of applying beam quality correction factors to model compensator-induced depth-hardening effects is investigated and the present work comprises a dosimetric verification of the model for a common compensator material. Lead sheet modulators for four different phantom shapes were designed using a treatment planning system based on the model. The modulators were designed to yield homogeneous dose in a plane. The calculated modulation created by the lead sheets was re-imported into the treatment planning system and applied to a water phantom geometry for verification purposes. Comparing measurements, a total of 31 different geometries were measured, with calculations in this geometry showing good agreement for depth doses, dose profiles and output data with a maximum deviation of 4% except locally in the penumbra region and close to the edges of the cut lead sheets.

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

    PubMed

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

    2013-11-21

    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

  4. Verification of the agreement of two dosimetric methods with radioiodine therapy in hyperthyroid patients

    SciTech Connect

    Canzi, Cristina; Zito, Felicia; Voltini, Franco; Reschini, Eugenio; Gerundini, Paolo

    2006-08-15

    The aim of this study was to verify the capability of an MIRD formula-based dosimetric method to predict radioiodine kinetics (fraction of administered iodine transferred to the thyroid, U{sub 0}, and effective clearance rate, {lambda}{sub eff}) and absorbed dose after oral therapeutic {sup 131}I administration. The method is based on {sup 123}I intravenous administration and five subsequent gamma camera measured uptake values determined separately on different structures within the thyroid. Another dosimetric method based on only the {sup 123}I 24-h uptake and a fixed {lambda}{sub eff} value was also considered. Eighty-nine hyperthyroid patients (10 with Graves' disease and 79 with autonomously functioning nodules) were studied and 132 thyroidal structures were evaluated. The mean time interval between dosimetry and therapy was 20{+-}10d. Uptake values were measured at 2, 4, 24, 48, and 120 h during dosimetry and at 2, 4, 24, 48, 96, and 168 h during therapy. The value 0.125d{sup -1} was chosen in the fixed-{lambda}{sub eff} method. The planned doses to the target ranged from 120 to 250 Gy depending on the type and severity of hyperthyroidism. The following significant correlations between therapeutic and dosimetric parameters were found: U{sub 0}ther=0.88U{sub 0}dos (r=0.97,p<0.01), {lambda}{sub eff}ther=1.01{lambda}{sub eff}dos (r=0.85,p<0.01), and D{sub estimated}=0.85D{sub planned} (r=0.88,p<0.01). The percent difference between U{sub 0}ther and U{sub 0}dos ranged from -44 to 32% and between {lambda}{sub eff}ther and {lambda}{sub eff}dos from -32 to 48%. U{sub 0}ther was lower than U{sub 0}dos in 74% of cases: this can be explained by the self-stunning effect of {sup 131}I therapeutic activity that produced a dose of about 20 Gy with a maximum dose rate of 0.6 Gy/h over the initial 24-48 h. The differences, {delta}D, between the estimated and the planned doses ranged from -42% (-87 Gy) to 32% (59 Gy); in 73% of cases the difference was within {+-}35 Gy

  5. Dosimetric and clinical experience in eye proton treatment at INFN-LNS

    SciTech Connect

    Cirrone, G. A. P.; Cuttone, G.; Di Rosa, F.; Lojacono, P.; Mongelli, V.; Patti, I. V.; Pittera, S.; Russo, G.; Valastro, L. M.; Lo Nigro, S.; Ott, J.; Reibaldi, A.; Privitera, G.; Raffaele, L.; Salamone, V.; Spatola, C.; Sabini, M. G.

    2009-05-04

    After six years of activity 155 patients have been treated inside the CATANA (Centro di AdroTerapia ed Applicazioni Nucleari Avanzate) facility. CATANA is the first and unique proton therapy facility in which the 62 MeV proton beams, accelerated by a Superconducting Cyclotron, are used for the radio-therapeutic treatments of choroidal and iris melanomas. Inside CATANA new absolute and relative dosimetric techniques have been developed in order to achieve the best results in terms of treatment precision and dose release accuracy. The follow-up results for 42 patients demonstrated the efficacy of high energy protons in the radiotherapeutic field and encouraged us in our activity in the battle against cancer.

  6. Dosimetric differences in flattened and flattening filter-free beam treatment plans

    PubMed Central

    Yan, Yue; Yadav, Poonam; Bassetti, Michael; Du, Kaifang; Saenz, Daniel; Harari, Paul; Paliwal, Bhudatt R.

    2016-01-01

    This study investigated the dosimetric differences in treatment plans from flattened and flattening filter-free (FFF) beams from the TrueBeam System. A total of 104 treatment plans with static (sliding window) intensity-modulated radiotherapy beams and volumetric-modulated arc therapy (VMAT) beams were generated for 15 patients involving three cancer sites. In general, the FFF beam provides similar target coverage as the flattened beam with improved dose sparing to organ-at-risk (OAR). Among all three cancer sites, the head and neck showed more important differences between the flattened beam and FFF beam. The maximum reduction of the FFF beam in the mean dose reached up to 2.82 Gy for larynx in head and neck case. Compared to the 6 MV flattened beam, the 10 MV FFF beam provided improved dose sparing to certain OARs, especially for VMAT cases. Thus, 10 MV FFF beam could be used to improve the treatment plan. PMID:27217620

  7. The ESR dosimetric features of strontium sulfate and temperature effects on radiation-induced signals

    NASA Astrophysics Data System (ADS)

    Acar, Ali Osman; Polat, Mustafa; Aydin, Talat; Aydaş, Canan

    2016-06-01

    In the present work, the ESR dosimetric potential of strontium sulfate has been investigated in the radiation dose range of 1-100 Gy. It does not exhibit any ESR signal before irradiation. However, irradiation produced three intensive resonance signals (A, B and C) which increase linearly in the studied dose range. Variable temperature study showed that all ESR signals were found to decrease significantly at temperatures higher than 340 K. Kinetic studies performed at high temperatures showed that at least two distinct radical species with the activation energy values of 42.8±3.6 and 88.2±5.8 kJ/mol, respectively, contributed to the ESR signal B.

  8. Case Report and Dosimetric Analysis of an Axillary Recurrence After Partial Breast Irradiation with Mammosite Catheter

    SciTech Connect

    Shah, Anand P. Dickler, Adam; Kirk, Michael C.; Chen, Sea S.; Strauss, Jonathan B.; Coon, Alan B.; Turian, Julius V.; Siziopikou, Kalliopi; Dowlat, Kambiz; Griem, Katherine L.

    2008-10-01

    Partial breast irradiation (PBI) was designed in part to decrease overall treatment times associated with whole breast radiation therapy (WBRT). WBRT treats the entire breast and usually portions of the axilla. The goal of PBI is to treat a smaller volume of breast tissue in less time, focusing the dose around the lumpectomy cavity. The following is a case of a 64-year-old woman with early-stage breast cancer treated with PBI who failed regionally in the ipsilateral axilla. With our dosimetric analysis, we found that the entire area of this axillary failure would have likely received at least 45 Gy if WBRT had been used, enough to sterilize microscopic disease. With PBI, this area received a mean dose of only 2.8 Gy, which raises the possibility that this regional failure may have been prevented had WBRT been used instead of PBI.

  9. 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

  10. The role of deep centers in formation of dosimetric properties of wide-gap materials

    NASA Astrophysics Data System (ADS)

    Nikiforov, S. V.; Kortov, V. S.

    2014-11-01

    The direct and indirect methods of experimental detection of deep traps in wide-gap insulators are described. The experimentally observed effects of influence of deep traps with different nature on luminescent and dosimetric properties of materials are analyzed. It is established that the most wide-spread and well-studied effects are the sensitization and superlinearity of dose response. They are interpreted in terms of the kinetic model of competitive electron traps. Taking into account the temperature dependence of capture probability by deep traps in this model allows one to explain some new effects associated with luminescence thermal quenching. The luminescence model of Al2O3:C single crystal is described. In this model the temperature dependence of competitive interaction between the main and deep traps is caused by thermal ionization of excited states of F-centers.

  11. Dosimetric Characteristics of 6 MV Modified Beams by Physical Wedges of a Siemens Linear Accelerator.

    PubMed

    Zabihzadeh, Mansour; Birgani, Mohammad Javad Tahmasebi; Hoseini-Ghahfarokhi, Mojtaba; Arvandi, Sholeh; Hoseini, Seyed Mohammad; Fadaei, Mahbube

    2016-01-01

    Physical wedges still can be used as missing tissue compensators or filters to alter the shape of isodose curves in a target volume to reach an optimal radiotherapy plan without creating a hotspot. The aim of this study was to investigate the dosimetric properties of physical wedges filters such as off-axis photon fluence, photon spectrum, output factor and half value layer. The photon beam quality of a 6 MV Primus Siemens modified by 150 and 450 physical wedges was studied with BEAMnrc Monte Carlo (MC) code. The calculated present depth dose and dose profile curves for open and wedged photon beam were in good agreement with the measurements. Increase of wedge angle increased the beam hardening and this effect was more pronounced at the heal region. Using such an accurate MC model to determine of wedge factors and implementation of it as a calculation algorithm in the future treatment planning systems is recommended. PMID:27221838

  12. Dosimetric characteristics of LiF:Mg,Cu,Si thermoluminescent materials

    NASA Astrophysics Data System (ADS)

    Lee, J. I.; Yang, J. S.; Kim, J. L.; Pradhan, A. S.; Lee, J. D.; Chung, K. S.; Choe, H. S.

    2006-08-01

    Dosimetric characteristics of LiF:Mg,Cu,Si thermoluminescent (TL) material developed at KAERI have been investigated and compared with those of commercially available LiF:Mg,Cu,P (GR-200A). LiF:Mg,Cu,Si thermoluminescence dosimeter (TLD) can be heated up to 573K without any loss of TL sensitivity or any change in the glow curve structure. High-temperature glow peak in LiF:Mg,Cu,Si is significantly lower than that in GR-200A, consequently the residual signal is only 0.025%, which is about 35 times less than that of GR-200A. The TL sensitivity of the LiF:Mg,Cu,Si TLD is about 55 and 1.1 times higher than those of the LiF:Mg,Ti (TLD-100) and GR-200A, respectively.

  13. Dosimetric effect by shallow air cavities in high energy electron beams.

    PubMed

    Zarza-Moreno, M; Carreira, P; Madureira, L; Miras Del Rio, H; Salguero, F J; Leal, A; Teixeira, N; Jesus, A P; Mora, G

    2014-03-01

    This study evaluates the dosimetric impact caused by an air cavity located at 2 mm depth from the top surface in a PMMA phantom irradiated by electron beams produced by a Siemens Primus linear accelerator. A systematic evaluation of the effect related to the cavity area and thickness as well as to the electron beam energy was performed by using Monte Carlo simulations (EGSnrc code), Pencil Beam algorithm and Gafchromic EBT2 films. A home-PMMA phantom with the same geometry as the simulated one was specifically constructed for the measurements. Our results indicate that the presence of the cavity causes an increase (up to 70%) of the dose maximum value as well as a shift forward of the position of the depth-dose curve, compared to the homogeneous one. Pronounced dose discontinuities in the regions close to the lateral cavity edges are observed. The shape and magnitude of these discontinuities change with the dimension of the cavity. It is also found that the cavity effect is more pronounced (6%) for the 12 MeV electron beam and the presence of cavities with large thickness and small area introduces more significant variations (up to 70%) on the depth-dose curves. Overall, the Gafchromic EBT2 film measurements were found in agreement within 3% with Monte Carlo calculations and predict well the fine details of the dosimetric change near the cavity interface. The Pencil Beam calculations underestimate the dose up to 40% compared to Monte Carlo simulations; in particular for the largest cavity thickness (2.8 cm).

  14. Treatment and dosimetric advantages between VMAT, IMRT, and helical tomotherapy in prostate cancer.

    PubMed

    Tsai, Chiao-Ling; Wu, Jian-Kuen; Chao, Hsiao-Ling; Tsai, Yi-Chun; Cheng, Jason Chia-Hsien

    2011-01-01

    We investigated the possible treatment and dosimetric advantage of volumetric modulated arc therapy (VMAT) over step-and-shoot intensity-modulated radiation therapy (step-and-hhoot IMRT) and helical tomotherapy (HT). Twelve prostate cancer patients undergoing VMAT to the prostate were included. Three treatment plans (VMAT, step-and-shoot IMRT, HT) were generated for each patient. The doses to clinical target volume and 95% of planning target volume were both ≥ 78 Gy. Target coverage, conformity index, dose to rectum/bladder, monitor units (MU), treatment time, equivalent uniform dose (EUD), normal tissue complication probability (NTCP) of targets, and rectum/bladder were compared between techniques. HT provided superior conformity and significantly less rectal volume exposed to 65 Gy and 40 Gy, as well as EUD/NTCP of rectum than step-and-shoot IMRT, whereas VMAT had a slight dosimetric advantage over step-and-shoot IMRT. Notably, significantly lower MUs were needed for VMAT (309.7 ± 35.4) and step-and-shoot IMRT (336.1 ± 16.8) than for HT (3368 ± 638.7) (p < 0.001). The treatment time (minutes) was significantly shorter for VMAT (2.6 ± 0.5) than step-and-shoot IMRT (3.8 ± 0.3) and HT (3.8 ± 0.6) (p < 0.001). Dose verification of VMAT using point dose and film dosimetry met the accepted criteria. VMAT and step-and-shoot IMRT have comparable dosimetry, but treatment efficiency is significantly higher for VMAT than for step-and-shoot IMRT and HT.

  15. Treatment and Dosimetric Advantages Between VMAT, IMRT, and Helical TomoTherapy in Prostate Cancer

    SciTech Connect

    Tsai, Chiao-Ling; Wu, Jian-Kuen; Chao, Hsiao-Ling; Tsai, Yi-Chun; Cheng, Jason Chia-Hsien

    2011-10-01

    We investigated the possible treatment and dosimetric advantage of volumetric modulated arc therapy (VMAT) over step-and-shoot intensity-modulated radiation therapy (step-and-hhoot IMRT) and helical tomotherapy (HT). Twelve prostate cancer patients undergoing VMAT to the prostate were included. Three treatment plans (VMAT, step-and-shoot IMRT, HT) were generated for each patient. The doses to clinical target volume and 95% of planning target volume were both {>=}78 Gy. Target coverage, conformity index, dose to rectum/bladder, monitor units (MU), treatment time, equivalent uniform dose (EUD), normal tissue complication probability (NTCP) of targets, and rectum/bladder were compared between techniques. HT provided superior conformity and significantly less rectal volume exposed to 65 Gy and 40 Gy, as well as EUD/NTCP of rectum than step-and-shoot IMRT, whereas VMAT had a slight dosimetric advantage over step-and-shoot IMRT. Notably, significantly lower MUs were needed for VMAT (309.7 {+-} 35.4) and step-and-shoot IMRT (336.1 {+-} 16.8) than for HT (3368 {+-} 638.7) (p < 0.001). The treatment time (minutes) was significantly shorter for VMAT (2.6 {+-} 0.5) than step-and-shoot IMRT (3.8 {+-} 0.3) and HT (3.8 {+-} 0.6) (p < 0.001). Dose verification of VMAT using point dose and film dosimetry met the accepted criteria. VMAT and step-and-shoot IMRT have comparable dosimetry, but treatment efficiency is significantly higher for VMAT than for step-and-shoot IMRT and HT.

  16. Bolus-dependent dosimetric effect of positioning errors for tangential scalp radiotherapy with helical tomotherapy

    SciTech Connect

    Lobb, Eric

    2014-04-01

    The dosimetric effect of errors in patient position is studied on-phantom as a function of simulated bolus thickness to assess the need for bolus utilization in scalp radiotherapy with tomotherapy. A treatment plan is generated on a cylindrical phantom, mimicking a radiotherapy technique for the scalp utilizing primarily tangential beamlets. A planning target volume with embedded scalplike clinical target volumes (CTVs) is planned to a uniform dose of 200 cGy. Translational errors in phantom position are introduced in 1-mm increments and dose is recomputed from the original sinogram. For each error the maximum dose, minimum dose, clinical target dose homogeneity index (HI), and dose-volume histogram (DVH) are presented for simulated bolus thicknesses from 0 to 10 mm. Baseline HI values for all bolus thicknesses were in the 5.5 to 7.0 range, increasing to a maximum of 18.0 to 30.5 for the largest positioning errors when 0 to 2 mm of bolus is used. Utilizing 5 mm of bolus resulted in a maximum HI value of 9.5 for the largest positioning errors. Using 0 to 2 mm of bolus resulted in minimum and maximum dose values of 85% to 94% and 118% to 125% of the prescription dose, respectively. When using 5 mm of bolus these values were 98.5% and 109.5%. DVHs showed minimal changes in CTV dose coverage when using 5 mm of bolus, even for the largest positioning errors. CTV dose homogeneity becomes increasingly sensitive to errors in patient position as bolus thickness decreases when treating the scalp with primarily tangential beamlets. Performing a radial expansion of the scalp CTV into 5 mm of bolus material minimizes dosimetric sensitivity to errors in patient position as large as 5 mm and is therefore recommended.

  17. Characterizing Interfraction Variations and Their Dosimetric Effects in Prostate Cancer Radiotherapy

    SciTech Connect

    Peng Cheng; Ahunbay, Ergun; Chen Guangpei; Anderson, Savannah; Lawton, Colleen; Li, X. Allen

    2011-03-01

    Purpose: To quantitatively characterize the interfraction variations and their dosimetric effects in radiotherapy for prostate cancer. Methods and Materials: A total of 486 daily computed tomography (CT) sets acquired for 20 prostate cancer patients treated with daily CT-guided repositioning using a linear accelerator and CT-on-rail combination were analyzed. The prostate, rectum, and bladder, delineated on each daily CT data set, were compared with those from the planning CT scan. Several quantities, including Dice's coefficient and the maximal overlapping rate, were used to characterize the interfraction variations. The delivered dose was reconstructed by applying the original plan to the daily CT scan with consideration of proper repositioning. Results: The mean prostate Dice's coefficient and maximal overlapping rate after bony registration was 69.7% {+-} 13.8% (standard deviation) and 85.6% {+-} 7.8% (standard deviation), respectively. The daily delivered dose distributions were generally inferior to the planned dose distribution for target coverage and/or normal structure sparing. For example, for approximately 5% of the treatment fractions, the prostate volume receiving 100% of the prescription dose decreased dramatically (15-20%) compared with its planned value. The magnitudes of the interfraction variations and their dosimetric effects indicated that, statistically, current standard repositioning using prostate alignment might be adequate for two-thirds of the fractions, but for the rest of the fractions, better on-line correction strategies, such as on-line replanning, are needed. Conclusion: Different adaptive correction schemes for prostatic interfraction changes can be used according to the anatomic changes, as quantified by the organ displacement and deformation parameters. On-line replanning is needed for approximately one-third of the treatment fractions.

  18. Neovascular Glaucoma After Stereotactic Radiotherapy for Juxtapapillary Choroidal Melanoma: Histopathologic and Dosimetric Findings

    SciTech Connect

    Fernandes, Bruno F.; Weisbrod, Daniel; Yuecel, Yeni H.; Follwell, Matthew; Krema, Hatem; Heydarian, Mostafa; Xu Wei; Payne, David; McGowan, Hugh; Simpson, Ernest R.; Laperriere, Normand; Sahgal, Arjun

    2011-06-01

    Purpose: Enucleation after stereotactic radiotherapy (SRT) for juxtapapillary choroidal melanoma may be required because of tumor progression (TP) or the development of intractable radiation-induced neovascular glaucoma (NVG). We compare pathologic changes and dosimetric findings in those eyes enucleated secondary to NVG as opposed to TP to better understand potential mechanisms. Methods and Materials: Patients with juxtapapillary choroidal melanoma treated with SRT (70 Gy in 5 fractions, alternate days over a total of 10 days) at the Princess Margaret Hospital, Toronto, Ontario, Canada, who underwent enucleation between 1998 and 2006 were selected. We correlated dosimetric data based on the patient's original SRT treatment plan with histopathologic findings in the retina, optic nerve head, and anterior chamber. A dedicated ocular pathologist reviewed each case in a blinded fashion. Results: Ten eyes in ten patients were enucleated after SRT. Six were enucleated secondary to NVG and four secondary to because of TP. Aggressive tumor features such as invasion of the sclera and epithelioid cell type were observed predominantly in the TP group. Retinal damage was more predominant in the NVG group, as were findings of radiation-related retinal vascular changes of fibrinoid necrosis and hyalinization. No conclusive radiation-related effects were found in the anterior chamber. The maximum point dose and dose to 0.1 cc were lower for the anterior chamber as compared with the dose to the tumor, retina, and optic nerve head. The mean 0.1-cc doses to the retina were 69.4 Gy and 73.5 Gy and to the anterior chamber were 4.9 Gy and 17.3 Gy for the NVG group and tumor progression group, respectively. Conclusions: Our findings suggest that NVG is due to radiation damage to the posterior chamber of the eye rather than primary radiation damage to the anterior segment.

  19. SU-E-T-09: A Dosimetric Analysis of Various Clinically Used Bolus Materials

    SciTech Connect

    Stowe, M; Yeager, C; Zhou, F; Hand, C

    2014-06-01

    Purpose: To evaluate the dosimetric effect of various clinically used bolus materials. Methods: Materials investigated include solid water, superflab, wet gauze, wet sheets, Play-Doh{sup ™}, and gauze embedded with petroleum jelly. Each bolusing material was scanned in a Philips CT to determine the Hounsfield unit (HU) and to verify uniformity throughout the material. Using the corresponding HU, boluses of 0.5 cm and 1.0 cm thicknesses were created in the Eclipse treatment planning system (TPS) on a solid water phantom. Dose was calculated at various depths for beam energies 6 MV, 6 MeV, 9 MeV, and 12 MeV to determine the effects of each material on deposition of dose. In addition, linac-based measurements at these energies were made using a farmer chamber in solid water. Wet sheets and wet gauze were measured with various water content to quantify the effects on dose. Results: Preliminary CT scans find a range in HU of bolus materials from −120 to almost 300. There is a trend in the dose at depth based on the HU of the material; however inconsistencies are found when the bolus materials have a negative HU value. The measured data indicates that there is a linear relationship between the mass of water in a material and the dose reading, the slope of which is material dependent. Conclusion: Due to the variation in HU of the bolus materials studied, it is recommended that any new bolus be evaluated before clinical use to determine physical and dosimetric properties. If possible, patients should have bolus included in their CT scans; or if the bolus is created in the TPS, the HU should correspond to the material used. For water-soaked materials, once the bolus material is selected (gauze or sheet), the bolusing effect is only dependent on the amount of water applied to the material.

  20. Predicting Nonauditory Adverse Radiation Effects Following Radiosurgery for Vestibular Schwannoma: A Volume and Dosimetric Analysis

    SciTech Connect

    Hayhurst, Caroline; Monsalves, Eric; Bernstein, Mark; Gentili, Fred; Heydarian, Mostafa; Tsao, May; Schwartz, Michael; Prooijen, Monique van; Millar, Barbara-Ann; Menard, Cynthia; Kulkarni, Abhaya V.; Laperriere, Norm; Zadeh, Gelareh

    2012-04-01

    Purpose: To define clinical and dosimetric predictors of nonauditory adverse radiation effects after radiosurgery for vestibular schwannoma treated with a 12 Gy prescription dose. Methods: We retrospectively reviewed our experience of vestibular schwannoma patients treated between September 2005 and December 2009. Two hundred patients were treated at a 12 Gy prescription dose; 80 had complete clinical and radiological follow-up for at least 24 months (median, 28.5 months). All treatment plans were reviewed for target volume and dosimetry characteristics; gradient index; homogeneity index, defined as the maximum dose in the treatment volume divided by the prescription dose; conformity index; brainstem; and trigeminal nerve dose. All adverse radiation effects (ARE) were recorded. Because the intent of our study was to focus on the nonauditory adverse effects, hearing outcome was not evaluated in this study. Results: Twenty-seven (33.8%) patients developed ARE, 5 (6%) developed hydrocephalus, 10 (12.5%) reported new ataxia, 17 (21%) developed trigeminal dysfunction, 3 (3.75%) had facial weakness, and 1 patient developed hemifacial spasm. The development of edema within the pons was significantly associated with ARE (p = 0.001). On multivariate analysis, only target volume is a significant predictor of ARE (p = 0.001). There is a target volume threshold of 5 cm3, above which ARE are more likely. The treatment plan dosimetric characteristics are not associated with ARE, although the maximum dose to the 5th nerve is a significant predictor of trigeminal dysfunction, with a threshold of 9 Gy. The overall 2-year tumor control rate was 96%. Conclusions: Target volume is the most important predictor of adverse radiation effects, and we identified the significant treatment volume threshold to be 5 cm3. We also established through our series that the maximum tolerable dose to the 5th nerve is 9 Gy.

  1. Dosimetric Quantities for Computed Tomography Examinations of Paediatric Patients on the Thoracic and Abdominal Regions

    SciTech Connect

    Flores-M, E.; Gamboa de Buen, I.; Buenfil, A. E.; Ruiz-Trejo, C.; Dies, P.

    2010-12-07

    Computed Tomography (CT) is a high dose X ray imaging procedure and its use has rapidly increased in the last two decades fueled by the development of helical CT. The aim of this study is to present values of the dosimetric quantities for CT paediatric examinations of thoracic and abdominal regions. The protocols studied were those of chest, lung-mediastine, chest-abdomen, pulmonary high resolution and mediastine-abdomen, which are the more common examinations performed at ''Hospital Infantil de Mexico Federico Gomez'' in the thoracic-abdominal region. The measurements were performed on a Siemens SOMATOM Sensation 16 CT Scanner and the equipment used was a CT pencil ionization chamber, connected to an electrometer. This system was calibrated for RQT9 CT beam quality. A PMMA head phantom with diameter of 16 cm and length of 15 cm was also used. The dosimetric quantities measured were the weighted air kerma index (C{sub w}), the volumetric dose index (C{sub vol}) and the CT air kerma-length product. It was found that the pulmonary high resolution examination presented the highest values for the C{sub w}(31.1 mGy) and C{sub vol}(11.1 mGy). The examination with the lowest values of these two quantities was the chest-abdomen protocol with 10.5 mGy for C{sub w} and 5.5 mGy for C{sub vol}. However, this protocol presented the highest value for P{sub KL,CT}(282.2 mGy cm) when considering the average clinical length of the examinations.

  2. Correlation of Clinical and Dosimetric Factors With Adverse Pulmonary Outcomes in Children After Lung Irradiation

    SciTech Connect

    Venkatramani, Rajkumar; Kamath, Sunil; Wong, Kenneth; Malvar, Jemily; Sposto, Richard; Goodarzian, Fariba; Freyer, David R.; Keens, Thomas G.; and others

    2013-08-01

    Purpose: To identify the incidence and the risk factors for pulmonary toxicity in children treated for cancer with contemporary lung irradiation. Methods and Materials: We analyzed clinical features, radiographic findings, pulmonary function tests, and dosimetric parameters of children receiving irradiation to the lung fields over a 10-year period. Results: We identified 109 patients (75 male patients). The median age at irradiation was 13.8 years (range, 0.04-20.9 years). The median follow-up period was 3.4 years. The median prescribed radiation dose was 21 Gy (range, 0.4-64.8 Gy). Pulmonary toxic chemotherapy included bleomycin in 58.7% of patients and cyclophosphamide in 83.5%. The following pulmonary outcomes were identified and the 5-year cumulative incidence after irradiation was determined: pneumonitis, 6%; chronic cough, 10%; pneumonia, 35%; dyspnea, 11%; supplemental oxygen requirement, 2%; radiographic interstitial lung disease, 40%; and chest wall deformity, 12%. One patient died of progressive respiratory failure. Post-irradiation pulmonary function tests available from 44 patients showed evidence of obstructive lung disease (25%), restrictive disease (11%), hyperinflation (32%), and abnormal diffusion capacity (12%). Thoracic surgery, bleomycin, age, mean lung irradiation dose (MLD), maximum lung dose, prescribed dose, and dosimetric parameters between V{sub 22} (volume of lung exposed to a radiation dose ≥22 Gy) and V{sub 30} (volume of lung exposed to a radiation dose ≥30 Gy) were significant for the development of adverse pulmonary outcomes on univariate analysis. MLD, maximum lung dose, and V{sub dose} (percentage of volume of lung receiving the threshold dose or greater) were highly correlated. On multivariate analysis, MLD was the sole significant predictor of adverse pulmonary outcome (P=.01). Conclusions: Significant pulmonary dysfunction occurs in children receiving lung irradiation by contemporary techniques. MLD rather than prescribed

  3. SU-C-213-06: Dosimetric Verification of 3D Printed Electron Bolus

    SciTech Connect

    Rasmussen, K; Corbett, M; Pelletier, C; Huang, Z; Feng, Y; Jung, J

    2015-06-15

    Purpose: To determine the dosimetric effect of 3D printed bolus in an anthropomorphic phantom. Methods: Conformable bolus material was generated for an anthropomorphic phantom from a DICOM volume. The bolus generated was a uniform expansion of 5mm applied to the nose region of the phantom, as this is a difficult area to uniformly apply bolus clinically. A Printrbot metal 3D Printer using PLA plastic generated the bolus. A 9MeV anterior beam with a 5cm cone was used to deliver dose to the nose of the phantom. TLD measurements were compared to predicted values at the phantom surface. Film planes were analyzed for the printed bolus, a standard 5mm bolus sheet placed on the phantom, and the phantom with no bolus applied to determine depth and dose distributions. Results: TLDs measured within 2.5% of predicted value for the 3D bolus. Film demonstrated a more uniform dose distribution in the nostril region for the 3d printed bolus than the standard bolus. This difference is caused by the air gap created around the nostrils by the standard bolus, creating a secondary build-up region. Both demonstrated a 50% central axis dose shift of 5mm relative to the no bolus film. HU for the bolus calculated the PLA electron density to be ∼1.1g/cc. Physical density was measured to be 1.3g/cc overall. Conclusion: 3D printed PLA bolus demonstrates improved dosimetric performance to standard bolus for electron beams with complex phantom geometry.

  4. Monte Carlo investigation of the dosimetric effect of the Autoscan ultrasound probe for guidance in radiotherapy

    NASA Astrophysics Data System (ADS)

    Martyn, Michael; O'Shea, Tuathan; Harris, Emma; Bamber, Jeffrey; Gilroy, Stephen; Foley, Mark J.

    2016-04-01

    The aim of this study was to quantify the dosimetric effect of the Autoscan™ ultrasound probe, which is a 3D transperineal probe used for real-time tissue tracking during the delivery of radiotherapy. CT images of an anthropomorphic phantom, with and without the probe placed in contact with its surface, were obtained (0.75 mm slice width, 140 kVp). CT datasets were used for relative dose calculation in Monte Carlo simulations of a 7-field plan delivered to the phantom. The Monte Carlo software packages BEAMnrc and DOSXYZnrc were used for this purpose. A number of simulations, which varied the distance of the radiation field edge from the probe face (0 mm to 5 mm), were performed. Perineal surface doses as a function of distance from the radiation field edge, with and without the probe in place, were compared. The presence of the probe was found to result in an increase in perineal surface dose, relative to the maximum dose. The maximum increase in surface dose was 18.15%, at a probe face to field edge distance of 0 mm. However increases in surface dose fall-off rapidly as this distance increases, agreeing within Monte Carlo simulation uncertainty at distances >= 5 mm. Using data from three patient volunteers, a typical probe face to field edge distance was calculated to be ≍20 mm. Our results therefore indicate that the presence of the probe is unlikely to adversely affect a typical patient treatment, since the dosimetric effect of the probe is minimal at these distances.

  5. Evaluation of Specific Absorption Rate as a Dosimetric Quantity for Electromagnetic Fields Bioeffects

    PubMed Central

    Panagopoulos, Dimitris J.; Johansson, Olle; Carlo, George L.

    2013-01-01

    Purpose To evaluate SAR as a dosimetric quantity for EMF bioeffects, and identify ways for increasing the precision in EMF dosimetry and bioactivity assessment. Methods We discuss the interaction of man-made electromagnetic waves with biological matter and calculate the energy transferred to a single free ion within a cell. We analyze the physics and biology of SAR and evaluate the methods of its estimation. We discuss the experimentally observed non-linearity between electromagnetic exposure and biological effect. Results We find that: a) The energy absorbed by living matter during exposure to environmentally accounted EMFs is normally well below the thermal level. b) All existing methods for SAR estimation, especially those based upon tissue conductivity and internal electric field, have serious deficiencies. c) The only method to estimate SAR without large error is by measuring temperature increases within biological tissue, which normally are negligible for environmental EMF intensities, and thus cannot be measured. Conclusions SAR actually refers to thermal effects, while the vast majority of the recorded biological effects from man-made non-ionizing environmental radiation are non-thermal. Even if SAR could be accurately estimated for a whole tissue, organ, or body, the biological/health effect is determined by tiny amounts of energy/power absorbed by specific biomolecules, which cannot be calculated. Moreover, it depends upon field parameters not taken into account in SAR calculation. Thus, SAR should not be used as the primary dosimetric quantity, but used only as a complementary measure, always reporting the estimating method and the corresponding error. Radiation/field intensity along with additional physical parameters (such as frequency, modulation etc) which can be directly and in any case more accurately measured on the surface of biological tissues, should constitute the primary measure for EMF exposures, in spite of similar uncertainty to predict

  6. Dosimetric Feasibility of Hypofractionated Proton Radiotherapy for Neoadjuvant Pancreatic Cancer Treatment

    SciTech Connect

    Kozak, Kevin R.; Kachnic, Lisa A.; Adams, Judith C; Crowley, Elizabeth M.; Alexander, Brian M.; Mamon, Harvey J.; Ryan, David P.; DeLaney, Thomas F.; Hong, Theodore S. . E-mail: tshong1@partners.org

    2007-08-01

    Purpose: To evaluate tumor and normal tissue dosimetry of a 5 cobalt gray equivalent (CGE) x 5 fraction proton radiotherapy schedule, before initiating a clinical trial of neoadjuvant, short-course proton radiotherapy for pancreatic adenocarcinoma. Methods and Materials: The first 9 pancreatic cancer patients treated with neoadjuvant intensity-modulated radiotherapy (1.8 Gy x 28) at the Massachusetts General Hospital had treatment plans generated using a 5 CGE x 5 fraction proton regimen. To facilitate dosimetric comparisons, clinical target volumes and normal tissue volumes were held constant. Plans were optimized for target volume coverage and normal tissue sparing. Results: Hypofractionated proton and conventionally fractionated intensity-modulated radiotherapy plans both provided acceptable target volume coverage and dose homogeneity. Improved dose conformality provided by the hypofractionated proton regimen resulted in significant sparing of kidneys, liver, and small bowel, evidenced by significant reductions in the mean doses, expressed as percentage prescribed dose, to these structures. Kidney and liver sparing was most evident in low-dose regions ({<=}20% prescribed dose for both kidneys and {<=}60% prescribed dose for liver). Improvements in small-bowel dosimetry were observed in high- and low-dose regions. Mean stomach and duodenum doses, expressed as percentage prescribed dose, were similar for the two techniques. Conclusions: A proton radiotherapy schedule consisting of 5 fractions of 5 CGE as part of neoadjuvant therapy for adenocarcinoma of the pancreas seems dosimetrically feasible, providing excellent target volume coverage, dose homogeneity, and normal tissue sparing. Hypofractionated proton radiotherapy in this setting merits Phase I clinical trial investigation.

  7. Gamma Knife irradiation method based on dosimetric controls to target small areas in rat brains

    SciTech Connect

    Constanzo, Julie; Paquette, Benoit; Charest, Gabriel; Masson-Côté, Laurence; Guillot, Mathieu

    2015-05-15

    Purpose: Targeted and whole-brain irradiation in humans can result in significant side effects causing decreased patient quality of life. To adequately investigate structural and functional alterations after stereotactic radiosurgery, preclinical studies are needed. The purpose of this work is to establish a robust standardized method of targeted irradiation on small regions of the rat brain. Methods: Euthanized male Fischer rats were imaged in a stereotactic bed, by computed tomography (CT), to estimate positioning variations relative to the bregma skull reference point. Using a rat brain atlas and the stereotactic bregma coordinates obtained from CT images, different regions of the brain were delimited and a treatment plan was generated. A single isocenter treatment plan delivering ≥100 Gy in 100% of the target volume was produced by Leksell GammaPlan using the 4 mm diameter collimator of sectors 4, 5, 7, and 8 of the Gamma Knife unit. Impact of positioning deviations of the rat brain on dose deposition was simulated by GammaPlan and validated with dosimetric measurements. Results: The authors’ results showed that 90% of the target volume received 100 ± 8 Gy and the maximum of deposited dose was 125 ± 0.7 Gy, which corresponds to an excellent relative standard deviation of 0.6%. This dose deposition calculated with GammaPlan was validated with dosimetric films resulting in a dose-profile agreement within 5%, both in X- and Z-axes. Conclusions: The authors’ results demonstrate the feasibility of standardizing the irradiation procedure of a small volume in the rat brain using a Gamma Knife.

  8. SU-E-J-167: Dosimetric Consequences From Minimal Displacements in APBI with SAVI Applicators

    SciTech Connect

    Chandrasekara, S; Dumitru, N; Hyvarinen, M; Pella, S

    2015-06-15

    Purpose: To determine the importance of providing proper solid immobilization in every fraction of treatment in APBI with brachytherapy. Methods: 125 patients treated with APBI brachytherapy with SAVI applicators at SFRO Boca Raton, from 2013–2015 were considered for this retrospective study. The CT scans of each patient, which were taken before each treatment, were imported in to the Oncentra treatment planning system. Then they were compared with the initial CT scan which was used for the initial plan. Deviation in displacements in reference to ribs and skin surface was measured and dosimetric evaluations respective to the initial image were performed. Results: Small deviations in displacements were observed from the SAVI applicator to the ribs and the skin surface. Dosimetric evaluations revealed, very small changes in the inter-fractionation position make significant differences in the maximum dose to critical organs. Additionally, the volume of the cavity also changed between fractions. As a Result, the maximum dose manifested variance between 10% and 32% in ribs and skin surface respectively. Conclusion: It appears that taking a CT scan before each treatment is necessary to minimize the risk of delivering undesired high doses to the critical organs. This study indicates, in 30% of the cases re-planning was necessary between treatments. We conclude that, treatment planning teams should evaluate the placement of the device by analyzing the CT images before each treatment and they must be prepared for re-planning if needed. This study also reveals the urgent need of improving the immobilization methods with APBI when treating with the SAVI applicator.

  9. Design, manufacture, and evaluation of an anthropomorphic pelvic phantom purpose-built for radiotherapy dosimetric intercomparison

    SciTech Connect

    Harrison, K. M.; Ebert, M. A.; Kron, T.; Howlett, S. J.; Cornes, D.; Hamilton, C. S.; Denham, J. W.

    2011-10-15

    Purpose: An anthropomorphic pelvic phantom was designed and constructed to meet specific criteria for multicenter radiotherapy dosimetric intercomparison. Methods: Three dimensional external and organ outlines were generated from a computed tomography image set of a male pelvis, forming the basis of design for an anatomically realistic phantom. Clinically relevant points of interest were selected throughout the dataset where point-dose values could be measured with thermoluminescence dosimeters and a small-volume ionization chamber. Following testing, three materials were selected and the phantom was manufactured using modern prototyping techniques into five separate coronal slices. Time lines and resource requirements for the phantom design and manufacture were recorded. The ability of the phantom to mimic the entire treatment chain was tested. Results: The phantom CT images indicated that organ densities and geometries were comparable to those of the original patient. The phantom proved simple to load for dosimetry and rapid to assemble. Due to heat release during manufacture, small air gaps and density heterogeneities were present throughout the phantom. The overall cost for production of the prototype phantom was comparable to other commercial anthropomorphic phantoms. The phantom was shown to be suitable for use as a ''patient'' to mimic the entire treatment chain for typical external beam radiotherapy for prostate and rectal cancer. Conclusions: The phantom constructed for the present study incorporates all characteristics necessary for accurate Level III intercomparison studies. Following use in an extensive Level III dosimetric comparison over a large time scale and geographic area, the phantom retained mechanical stability and did not show signs of radiation-induced degradation.

  10. Conventional Versus Automated Implantation of Loose Seeds in Prostate Brachytherapy: Analysis of Dosimetric and Clinical Results

    SciTech Connect

    Genebes, Caroline; Filleron, Thomas; Graff, Pierre; Jonca, Frédéric; Huyghe, Eric; Thoulouzan, Matthieu; Soulie, Michel; Malavaud, Bernard; Aziza, Richard; Brun, Thomas; Delannes, Martine; Bachaud, Jean-Marc

    2013-11-15

    Purpose: To review the clinical outcome of I-125 permanent prostate brachytherapy (PPB) for low-risk and intermediate-risk prostate cancer and to compare 2 techniques of loose-seed implantation. Methods and Materials: 574 consecutive patients underwent I-125 PPB for low-risk and intermediate-risk prostate cancer between 2000 and 2008. Two successive techniques were used: conventional implantation from 2000 to 2004 and automated implantation (Nucletron, FIRST system) from 2004 to 2008. Dosimetric and biochemical recurrence-free (bNED) survival results were reported and compared for the 2 techniques. Univariate and multivariate analysis researched independent predictors for bNED survival. Results: 419 (73%) and 155 (27%) patients with low-risk and intermediate-risk disease, respectively, were treated (median follow-up time, 69.3 months). The 60-month bNED survival rates were 95.2% and 85.7%, respectively, for patients with low-risk and intermediate-risk disease (P=.04). In univariate analysis, patients treated with automated implantation had worse bNED survival rates than did those treated with conventional implantation (P<.0001). By day 30, patients treated with automated implantation showed lower values of dose delivered to 90% of prostate volume (D90) and volume of prostate receiving 100% of prescribed dose (V100). In multivariate analysis, implantation technique, Gleason score, and V100 on day 30 were independent predictors of recurrence-free status. Grade 3 urethritis and urinary incontinence were observed in 2.6% and 1.6% of the cohort, respectively, with no significant differences between the 2 techniques. No grade 3 proctitis was observed. Conclusion: Satisfactory 60-month bNED survival rates (93.1%) and acceptable toxicity (grade 3 urethritis <3%) were achieved by loose-seed implantation. Automated implantation was associated with worse dosimetric and bNED survival outcomes.

  11. Dosimetric accuracy of proton therapy for chordoma patients with titanium implants

    PubMed Central

    Verburg, Joost M.; Seco, Joao

    2013-01-01

    Purpose: To investigate dosimetric errors in proton therapy treatment planning due to titanium implants, and to determine how these affect postoperative passively scattered proton therapy for chordoma patients with orthopedic hardware. Methods: The presence of titanium hardware near the tumor may affect the dosimetric accuracy of proton therapy. Artifacts in the computed tomography (CT) scan can cause errors in the proton stopping powers used for dose calculation, which are derived from CT numbers. Also, clinical dose calculation algorithms may not accurately simulate proton beam transport through the implants, which have very different properties as compared to human tissue. The authors first evaluated the impact of these two main issues. Dose errors introduced by metal artifacts were studied using phantoms with and without titanium inserts, and patient scans on which a metal artifact reduction method was applied. Pencil-beam dose calculations were compared to models of nuclear interactions in titanium and Monte Carlo simulations. Then, to assess the overall impact on treatment plans for chordoma, the authors compared the original clinical treatment plans to recalculated dose distributions employing both metal artifact reduction and Monte Carlo methods. Results: Dose recalculations of clinical proton fields showed that metal artifacts cause range errors up to 6 mm distal to regions affected by CT artifacts. Monte Carlo simulations revealed dose differences >10% in the high-dose area, and range differences up to 10 mm. Since these errors are mostly local in nature, the large number of fields limits the impact on target coverage in the chordoma treatment plans to a small decrease of dose homogeneity. Conclusions: In the presence of titanium implants, CT metal artifacts and the approximations of pencil-beam dose calculations cause considerable errors in proton dose calculation. The spatial distribution of the errors however limits the overall impact on passively

  12. Effect of heterogeneity correction on dosimetric parameters of radiotherapy planning for thoracic esophageal cancer

    SciTech Connect

    Nakayama, Masao; Yoshida, Kenji; Nishimura, Hideki; Miyawaki, Daisuke; Uehara, Kazuyuki; Okamoto, Yoshiaki; Okayama, Takanobu; Sasaki, Ryohei

    2014-04-01

    The present study aimed to investigate the effect of heterogeneity correction (HC) on dosimetric parameters in 3-dimensional conformal radiotherapy planning for patients with thoracic esophageal cancer. We retrospectively analyzed 20 patients. Two treatment plans were generated for each patient using a superposition algorithm on the Xio radiotherapy planning system. The first plan was calculated without HC. The second was a new plan calculated with HC, using identical beam geometries and maintaining the same number of monitor units as the first. With regard to the planning target volume (PTV), the overall mean differences in the prescription dose, maximum dose, mean dose, and dose that covers 95% of the PTV between the first and second plans were 1.10 Gy (1.8%), 1.35 Gy (2.2%), 1.10 Gy (1.9%), and 0.56 Gy (1.0%), respectively. With regard to parameters related to the organs at risk (OARs), the mean differences in the absolute percentages of lung volume receiving greater than 5, 10, 20, and 30 Gy (lung V{sub 5}, V{sub 10}, V{sub 20}, and V{sub 30}) between the first and second plans were 7.1%, 2.7%, 0.4%, and 0.5%, respectively. These results suggest that HC might have a more pronounced effect on the percentages of lung volume receiving lower doses (e.g., V{sub 5} and V{sub 10}) than on the dosimetric parameters related to the PTV and other OARs.

  13. Commissioning of a motion system to investigate dosimetric consequences due to variability of respiratory waveforms.

    PubMed

    Cetnar, Ashley J; James, Joshua; Wang, Brain

    2016-01-08

    A commercially available six-dimensional (6D) motion system was assessed for accuracy and clinical use in our department. Positional accuracy and respiratory waveform reproducibility were evaluated for the motion system. The system was then used to investigate the dosimetric consequences of respiratory waveform variation when an internal target volume (ITV) approach is used for motion management. The maximum deviations are 0.3 mm and 0.22° for translation and rotation accuracy, respectively, for the tested clinical ranges. The origin reproducibility is less than±0.1 mm. The average differences are less than 0.1 mm with a maximum standard deviation of 0.8 mm between waveforms of actual patients and replication of those waveforms by HexaMotion for three breath-hold and one free-breathing waveform. A modified gamma analysis shows greater than 98% agreement with a 0.5 mm and 100 ms threshold. The motion system was used to investigate respiratory waveform variation and showed that, as the amplitude of the treatment waveform increases above that of the simulation waveform, the periphery of the target volume receives less dose than expected. However, by using gating limits to terminate the beam outside of the simulation amplitude, the results are as expected dosimetrically. Specifically, the average dose difference in the periphery between treating with the simulation waveform and the larger amplitude waveform could be up to 12% less without gating limits, but only differed 2% or less with the gating limits in place. The general functionality of the system performs within the manufacturer's specifications and can accurately replicate patient specific waveforms. When an ITV approach is used for motion management, we found the use of gating limits that coincide with the amplitude of the patient waveform at simulation helpful to prevent the potential underdosing of the target due to changes in patient respiration.

  14. SU-E-T-456: Development of An EPID-Based Output Measurement and Dosimetric Verification Tool for Electron Beam Therapy

    SciTech Connect

    Ding, A; Han, B; Xing, L

    2014-06-01

    Purpose: To develop an efficient and robust method for output and absolute dosimetric measurements of electron beam therapy by using a high spatialresolution and high frame-rate amorphous silicon flat-panel electronic portal imaging device (EPID). Methods: A previously-established EPID dosimetry system was extended to measure the output factors of electron beams of various sizes and their planar dose distributions at reference depths. Specific EPID responses to different electron energies were derived from Monte Carlo (MC) simulations to de-convolve the EPID raw images to the incident electron fluence map. To reconstruct the 2D water-based dose distribution map at reference depths for different energies, the fluence map was further convolved with a MC simulated pencil beam kernel. Different energies of 6, 9, 12, 16, and 20 MeV from a Varian C-series linac were tested. Standard square fields ranging from 2×2 to 15×15 cm{sup 2} were measured and validated against film/ion chamber measurements. Small fields of different patient cases with irregular cutout shapes were also tested. Results: The EPIDmeasured output factors for 2×2, 3×3, 6×6, and 10×10 cm{sup 2} fields with all electron energies agree with the film/ion chamber data within 2.7%. The average discrepancy between EPID and film/ion chamber measurements was 1.4%. The differences for the three patient cases were 0.1%, 2.1%, and 1.6%. Deliveries with different monitor units were tested and the results exhibited good linearity. Measurements with different dose rate showed that the dose rate dependence was less than 1%. Using the proposed method, 2D absolute dose maps were created from the EPID raw images and the results were consistent with film measurements. Conclusion: The efficient data readout and portability of the newly developed EPID system provides an efficient and accurate solution for electron beam therapy. It addresses an important unmet clinical need for a fast and reliable small field output

  15. 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.

  16. The work of the ICRP dose calculational task group: Issues in implementation of the ICRP dosimetric methodology

    SciTech Connect

    Eckerman, K.F.

    1999-01-01

    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 novel 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.

  17. Dosimetric Correction for a 4D-Computed Tomography Dataset using the Free-Form Deformation Algorithm

    NASA Astrophysics Data System (ADS)

    Markel, Daniel; Alasti, Hamideh; Chow, James C. L.

    2012-10-01

    A Free-Form Deformable (FFD) image registration algorithm in conjunction with 4D Computed Tomography (CT) images was implemented within a graphical user interface, FFD4D, for dosimetric calculations. The algorithm was developed using the cubic-B-spline method with smoothness corrections and registration point assistance to mark fudicials. Validation of the algorithm was performed with manually measured geometric differences using a QUASAR Respiratory Motion Phantom. In this work, we used the FFD algorithm to demonstrate dosimetric corrections amongst 10 breathing phases of a lung cancer patient using the 4D-CT image datasets. Different methods to enhance the image processing speed for high-performance computing were also discussed.

  18. Estimation of a cosmonaut's radiation hazard during long-term space missions on the basis of a generalized dosimetric function.

    PubMed

    Shafirkin, A V; Petrov, V M

    2002-01-01

    This paper presents a new concept of radiation hazard assessment for spacecraft crew members during long term space missions on the basis of a generalized dosimetric function. This new dosimetric function enables a complicated nature of space radiation exposure to be reduced to the conditions of a standard irradiation. It can be obtained on the basis of mean-tissue equivalent dose values calculated for each space radiation source and transmission coefficients describing the influence of the complex spatial and temporal distribution of the absorbed dose in the cosmonaut's body on the radiobiological effects. The combination of cosmic ionizing radiation with other non-radiation nature factors in flight can also be accounted for. In terms of the generalized dose, it is possible to assess the nature and extent of lowering a crew working capacity, as well as radiation risk, both during a flight and post flight period. PMID:12539776

  19. Dosimetric prerequisites for routine clinical use of photon emitting brachytherapy sources with average energy higher than 50 kev

    SciTech Connect

    Li Zuofeng; Das, Rupak K.; De Werd, Larry A.; Ibbott, Geoffrey S.; Meigooni, Ali S.; Perez-Calatayud, Jose; Rivard, Mark J.; Sloboda, Ronald S.; Williamson, Jeffrey F.

    2007-01-15

    This paper presents the recommendations of the American Association of Physicists in Medicine (AAPM) and the European Society for Therapeutic Radiology and Oncology (ESTRO) on the dosimetric parameters to be characterized, and dosimetric studies to be performed to obtain them, for brachytherapy sources with average energy higher than 50 keV that are intended for routine clinical use. In addition, this document makes recommendations on procedures to be used to maintain vendor source strength calibration accuracy. These recommendations reflect the guidance of the AAPM and the ESTRO for its members, and may also be used as guidance to vendors and regulatory agencies in developing good manufacturing practices for sources used in routine clinical treatments.

  20. Influence of Pro-Qura-generated plans on postimplant dosimetric quality: a review of a multi-institutional database.

    PubMed

    Allen, Zachariah; Merrick, Gregory S; Grimm, Peter; Blasko, John; Sylvester, John; Butler, Wayne; Chaudry, Usman-Ul-Haq; Sitter, Michael

    2008-01-01

    The influence of Pro-Qura-generated plans vs. community-generated plans on postprostate brachytherapy dosimetric quality was compared. In the Pro-Qura database, 2933 postplans were evaluated from 57 institutions. A total of 1803 plans were generated by Pro-Qura and 1130 by community institutions. Iodine-125 (125I) plans outnumbered Palladium 103 (103Pd) plans by a ratio of 3:1. Postimplant dosimetry was performed in a standardized fashion by overlapping the preimplant ultrasound and the postimplant computed tomography (CT). In this analysis, adequacy was defined as a V100 > 80% and a D90 of 90% to 140% for both isotopes along with a V150 < 60% for 125I and < 75% for 103Pd. The mean postimplant V100 and D90 were 88.6% and 101.6% vs. 89.3% and 102.3% for Pro-Qura and community plans, respectively. When analyzed in terms of the first 8 sequence groups (10 patients/sequence group) for each institution, Pro-Qura planning resulted in less postimplant variability for V100 (86.2-89.5%) and for D90 (97.4-103.2%) while community-generated plans had greater V100 (85.3-91.2%) and D90 (95.9-105.2%) ranges. In terms of sequence groups, postimplant dosimetry was deemed "too cool" in 11% to 30% of cases and "too hot" in 12% to 27%. On average, no clinically significant postimplant dosimetric differences were discerned between Pro-Qura and community-based planning. However, substantially greater variability was identified in the community-based plan cohort. It is possible that the Pro-Qura plan and/or the routine postimplant dosimetric evaluation may have influenced dosimetric outcomes at community-based centers. PMID:18674685

  1. Influence of Pro-Qura-generated Plans on Postimplant Dosimetric Quality: A Review of a Multi-Institutional Database

    SciTech Connect

    Allen, Zachariah |||; Merrick, Gregory S. ||| Grimm, Peter; Blasko, John; Sylvester, John; Butler, Wayne; Chaudry, Usman-Ul-Haq; Sitter, Michael |||

    2008-10-01

    The influence of Pro-Qura-generated plans vs. community-generated plans on postprostate brachytherapy dosimetric quality was compared. In the Pro-Qura database, 2933 postplans were evaluated from 57 institutions. A total of 1803 plans were generated by Pro-Qura and 1130 by community institutions. Iodine-125 ({sup 125}I) plans outnumbered Palladium 103 ({sup 103}Pd) plans by a ratio of 3:1. Postimplant dosimetry was performed in a standardized fashion by overlapping the preimplant ultrasound and the postimplant computed tomography (CT). In this analysis, adequacy was defined as a V{sub 100} > 80% and a D{sub 90} of 90% to 140% for both isotopes along with a V{sub 150} < 60% for {sup 125}I and < 75% for {sup 103}Pd. The mean postimplant V{sub 100} and D{sub 90} were 88.6% and 101.6% vs. 89.3% and 102.3% for Pro-Qura and community plans, respectively. When analyzed in terms of the first 8 sequence groups (10 patients/sequence group) for each institution, Pro-Qura planning resulted in less postimplant variability for V{sub 100} (86.2-89.5%) and for D{sub 90} (97.4-103.2%) while community-generated plans had greater V{sub 100} (85.3-91.2%) and D{sub 90} (95.9-105.2%) ranges. In terms of sequence groups, postimplant dosimetry was deemed 'too cool' in 11% to 30% of cases and 'too hot' in 12% to 27%. On average, no clinically significant postimplant dosimetric differences were discerned between Pro-Qura and community-based planning. However, substantially greater variability was identified in the community-based plan cohort. It is possible that the Pro-Qura plan and/or the routine postimplant dosimetric evaluation may have influenced dosimetric outcomes at community-based centers.

  2. EchoSeed Model 6733 Iodine-125 brachytherapy source: Improved dosimetric characterization using the MCNP5 Monte Carlo code

    SciTech Connect

    Mosleh-Shirazi, M. A.; Hadad, K.; Faghihi, R.; Baradaran-Ghahfarokhi, M.; Naghshnezhad, Z.; Meigooni, A. S.

    2012-08-15

    This study primarily aimed to obtain the dosimetric characteristics of the Model 6733 {sup 125}I seed (EchoSeed) with improved precision and accuracy using a more up-to-date Monte-Carlo code and data (MCNP5) compared to previously published results, including an uncertainty analysis. Its secondary aim was to compare the results obtained using the MCNP5, MCNP4c2, and PTRAN codes for simulation of this low-energy photon-emitting source. The EchoSeed geometry and chemical compositions together with a published {sup 125}I spectrum were used to perform dosimetric characterization of this source as per the updated AAPM TG-43 protocol. These simulations were performed in liquid water material in order to obtain the clinically applicable dosimetric parameters for this source model. Dose rate constants in liquid water, derived from MCNP4c2 and MCNP5 simulations, were found to be 0.993 cGyh{sup -1} U{sup -1} ({+-}1.73%) and 0.965 cGyh{sup -1} U{sup -1} ({+-}1.68%), respectively. Overall, the MCNP5 derived radial dose and 2D anisotropy functions results were generally closer to the measured data (within {+-}4%) than MCNP4c and the published data for PTRAN code (Version 7.43), while the opposite was seen for dose rate constant. The generally improved MCNP5 Monte Carlo simulation may be attributed to a more recent and accurate cross-section library. However, some of the data points in the results obtained from the above-mentioned Monte Carlo codes showed no statistically significant differences. Derived dosimetric characteristics in liquid water are provided for clinical applications of this source model.

  3. Retrospective evaluation of dosimetric quality for prostate carcinomas treated with 3D conformal, intensity modulated and volumetric modulated arc radiotherapy

    SciTech Connect

    Crowe, Scott B; Kairn, Tanya; Middlebrook, Nigel; Hill, Brendan; Christie, David R H; Knight, Richard T; Kenny, John; Langton, Christian M; Trapp, Jamie V

    2013-12-15

    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). 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. 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. This study indicates that IMRT and VMAT have provided similar dosimetric quality, which is superior to the dosimetric quality achieved with 3DCRT.

  4. Dosimetric Significance of the ICRP's Updated Guidance and Models, 1989-2003, and Implications for U.S. Federal Guidance

    SciTech Connect

    Leggett, R.W.

    2003-09-10

    Over the past two decades the U.S. Environmental Protection Agency (EPA) has issued a series of Federal guidance documents for the purpose of providing the Federal and State agencies with technical information to assist their implementation of radiation protection programs. Currently recommended dose conversion factors, annual limits on intake, and derived air concentrations for intake of radionuclides are tabulated in Federal Guidance Report No. 11 (FGR 11), published in 1988. The tabulations in FGR 11 were based on dosimetric quantities and biokinetic and dosimetric models of the International Commission on Radiological Protection (ICRP) developed for application to occupational exposures. Since the publication of FGR 11 the ICRP has revised some of its dosimetric quantities and its models for workers and has also developed age-specific models and dose conversion factors for intake of radionuclides by members of the public. This report examines the extent of the changes in the inhalation and ingestion dose coefficients of FGR 11 implied by the updated recommendations of the ICRP, both for workers and members of the public.

  5. Matched-pair analysis and dosimetric variations of two types of software for interstitial permanent brachytherapy for prostate cancer

    SciTech Connect

    Ishiyama, Hiromichi; Nakamura, Ryuji; Satoh, Takefumi; Tanji, Susumu; Teh, Bin S.; Uemae, Mineko; Baba, Shiro; Hayakawa, Kazushige

    2012-04-01

    The purpose of this study was to determine whether identical dosimetric results could be achieved using different planning software for permanent interstitial brachytherapy for prostate cancer. Data from 492 patients treated with brachytherapy were used for matched-pair analysis. Interplant and Variseed were used as software for ultrasound-based treatment planning. Institution, neoadjuvant hormonal therapy, prostate volume, and source strength were used for factors to match the 2 groups. The study population comprised of 126 patients with treatment planning using Interplant software and 127 matched patients using Variseed software. Dosimetric results were compared between the 2 groups. The Variseed group showed significantly higher values for dose covering 90% of prostate volume (pD90), prostate volume covered by 150% of prescription dose (pV150), and dose covering 30% of the urethra (uD30) compared with the Interplant group. Our results showed that use of different software could lead to different dosimetric results, which might affect the clinical outcomes.

  6. Study of the dosimetric properties of an unflattened 6-MV photon beam by using the BEAMnrc code

    NASA Astrophysics Data System (ADS)

    Kajaria, Ankit; Sharma, Neeraj; Sharma, Shiru; Pradhan, Satyajit; Mandal, Abhijit; Aggarwal, Lalit. M.

    2016-08-01

    This study investigated the basic dosimetric properties of a Flattening-filter-free 6-MV photon beam based on the unique performance model of the Varian Clinic 600 linac operated with and without a flattening filter. Dosimetric features, including the central-axis absorbed dose, the beam profiles and the photon and electron fluences were calculated for the flattened and unflattened cases separately by using Monte Carlo simulations. We observe that the dosimetric field size and penumbra were slightly smaller for the unflattened beam, but the beam's non-flatness is unlikely to present a problem for treatments with small fields. Absolute depth dose calculations showed an increase in the dose rate by a factor of more than 2.4 for the unflattened 6-MV beam which depended on the depth. These results suggest that the removal of the filter could result in higher central-axis dose rates and hence, shorter beam delivery times for treatments. Surface doses were found to be higher for the unflattened beam due to more contamination electrons and low-energy photons being present in the beam. The total scatter factor, SCP, varies less with the field sizes, indicating that removing the filter from the beam line can reduce significantly the amount of head scatter photons and therefore, doses to normal tissues and organs.

  7. On the implementation of a recently proposed dosimetric formalism to a robotic radiosurgery system

    SciTech Connect

    Pantelis, E.; Moutsatsos, A.; Zourari, K.; Kilby, W.; Antypas, C.; Papagiannis, P.; Karaiskos, P.; Georgiou, E.; Sakelliou, L.

    2010-05-15

    Purpose: The aim of this work is to implement a recently proposed dosimetric formalism for nonstandard fields to the calibration and small field output factor measurement of a robotic stereotactic radiosurgery system. Methods: Reference dosimetry measurements were performed in the nonstandard, 60 mm diameter machine specific reference (msr) field using a Farmer ion chamber, five other cylindrical chambers with cavity lengths ranging from 16.25 down to 2.7 mm, and alanine dosimeters. Output factor measurements were performed for the 5, 7.5, 10, and 15 mm field sizes using microchambers, diode detectors, alanine dosimeters, TLD microcubes, and EBT Gafchromic films. Measurement correction factors as described in the proposed formalism were calculated for the ion chamber and diode detector output factor measurements based on published Monte Carlo data. Corresponding volume averaging correction factors were calculated for the alanine output factor measurements using 3D dose distributions, measured with polymer gel dosimeters. Results: Farmer chamber and alanine reference dosimetry results were found in close agreement, yielding a correction factor of k{sub Q{sub m{sub s{sub r,Q}{sup f{sub m}{sub s}{sub r},f{sub r}{sub e}{sub f}}}}}=0.999{+-}0.016 for the chamber readings. These results were also found to be in agreement within experimental uncertainties with corresponding results obtained using the shorter cavity length ionization chambers. The mean measured dose values of the latter, however, were found to be consistently greater than that of the Farmer chamber. This finding, combined with an observed inverse relationship between the mean measured dose and chamber cavity length that follows the trend predicted by theoretical volume averaging calculations in the msr field, implies that the Farmer k{sub Q{sub m{sub s{sub r,Q}{sup f{sub m}{sub s}{sub r},f{sub r}{sub e}{sub f}}}}} correction is greater than unity. Regarding the output factor results, deviations as large as

  8. Sensitivity of postplanning target and OAR coverage estimates to dosimetric margin distribution sampling parameters

    SciTech Connect

    Xu Huijun; Gordon, J. James; Siebers, Jeffrey V.

    2011-02-15

    Purpose: A dosimetric margin (DM) is the margin in a specified direction between a structure and a specified isodose surface, corresponding to a prescription or tolerance dose. The dosimetric margin distribution (DMD) is the distribution of DMs over all directions. Given a geometric uncertainty model, representing inter- or intrafraction setup uncertainties or internal organ motion, the DMD can be used to calculate coverage Q, which is the probability that a realized target or organ-at-risk (OAR) dose metric D{sub v} exceeds the corresponding prescription or tolerance dose. Postplanning coverage evaluation quantifies the percentage of uncertainties for which target and OAR structures meet their intended dose constraints. The goal of the present work is to evaluate coverage probabilities for 28 prostate treatment plans to determine DMD sampling parameters that ensure adequate accuracy for postplanning coverage estimates. Methods: Normally distributed interfraction setup uncertainties were applied to 28 plans for localized prostate cancer, with prescribed dose of 79.2 Gy and 10 mm clinical target volume to planning target volume (CTV-to-PTV) margins. Using angular or isotropic sampling techniques, dosimetric margins were determined for the CTV, bladder and rectum, assuming shift invariance of the dose distribution. For angular sampling, DMDs were sampled at fixed angular intervals {omega} (e.g., {omega}=1 deg., 2 deg., 5 deg., 10 deg., 20 deg.). Isotropic samples were uniformly distributed on the unit sphere resulting in variable angular increments, but were calculated for the same number of sampling directions as angular DMDs, and accordingly characterized by the effective angular increment {omega}{sub eff}. In each direction, the DM was calculated by moving the structure in radial steps of size {delta}(=0.1,0.2,0.5,1 mm) until the specified isodose was crossed. Coverage estimation accuracy {Delta}Q was quantified as a function of the sampling parameters {omega} or

  9. Human Mind Maps

    ERIC Educational Resources Information Center

    Glass, Tom

    2016-01-01

    When students generate mind maps, or concept maps, the maps are usually on paper, computer screens, or a blackboard. Human Mind Maps require few resources and little preparation. The main requirements are space where students can move around and a little creativity and imagination. Mind maps can be used for a variety of purposes, and Human Mind…

  10. Dosimetric Predictors of Radiation-induced Acute Nausea and Vomiting in IMRT for Nasopharyngeal Cancer

    SciTech Connect

    Lee, Victor H.F.; Ng, Sherry C.Y.; Leung, T.W.; Au, Gordon K.H.; Kwong, Dora L.W.

    2012-09-01

    Purpose: We wanted to investigate dosimetric parameters that would predict radiation-induced acute nausea and vomiting in intensity-modulated radiation therapy (IMRT) for undifferentiated carcinoma of the nasopharynx (NPC). Methods and Materials: Forty-nine consecutive patients with newly diagnosed NPC were treated with IMRT alone in this prospective study. Patients receiving any form of chemotherapy were excluded. The dorsal vagal complex (DVC) as well as the left and right vestibules (VB-L and VB-R, respectively) were contoured on planning computed tomography images. A structure combining both the VB-L and the VB-R, named VB-T, was also generated. All structures were labeled organs at risk (OAR). A 3-mm three-dimensional margin was added to these structures and labeled DVC+3 mm, VB-L+3 mm, VB-R+3 mm, and VB-T+3 mm to account for physiological body motion and setup error. No weightings were given to these structures during optimization in treatment planning. Dosimetric parameters were recorded from dose-volume histograms. Statistical analysis of parameters' association with nausea and vomiting was performed using univariate and multivariate logistic regression. Results: Six patients (12.2%) reported Grade 1 nausea, and 8 patients (16.3%) reported Grade 2 nausea. Also, 4 patients (8.2%) complained of Grade 1 vomiting, and 4 patients (8.2%) experienced Grade 2 vomiting. No patients developed protracted nausea and vomiting after completion of IMRT. For radiation-induced acute nausea, V40 (percentage volume receiving at least 40Gy) to the VB-T and V40>=80% to the VB-T were predictors, using univariate analysis. On multivariate analysis, V40>=80% to the VB-T was the only predictor. There were no predictors of radiation-induced acute vomiting, as the number of events was too small for analysis. Conclusions: This is the first study demonstrating that a V40 to the VB-T is predictive of radiation-induced acute nausea. The vestibules should be labeled as sensitive OARs, and

  11. Dosimetric feasibility of real-time MRI-guided proton therapy

    SciTech Connect

    Moteabbed, M. Schuemann, J.; Paganetti, H.

    2014-11-01

    Purpose: Magnetic resonance imaging (MRI) is a prime candidate for image-guided radiotherapy. This study was designed to assess the feasibility of real-time MRI-guided proton therapy by quantifying the dosimetric effects induced by the magnetic field in patients’ plans and identifying the associated clinical consequences. Methods: Monte Carlo dose calculation was performed for nine patients of various treatment sites (lung, liver, prostate, brain, skull-base, and spine) and tissue homogeneities, in the presence of 0.5 and 1.5 T magnetic fields. Dose volume histogram (DVH) parameters such as D{sub 95}, D{sub 5}, and V{sub 20} as well as equivalent uniform dose were compared for the target and organs at risk, before and after applying the magnetic field. The authors further assessed whether the plans affected by clinically relevant dose distortions could be corrected independent of the planning system. Results: By comparing the resulting dose distributions and analyzing the respective DVHs, it was determined that despite the observed lateral beam deflection, for magnetic fields of up to 0.5 T, neither was the target coverage jeopardized nor was the dose to the nearby organs increased in all cases except for prostate. However, for a 1.5 T magnetic field, the dose distortions were more pronounced and of clinical concern in all cases except for spine. In such circumstances, the target was severely underdosed, as indicated by a decrease in D{sub 95} of up to 41% of the prescribed dose compared to the nominal situation (no magnetic field). Sites such as liver and spine were less affected due to higher tissue homogeneity, typically smaller beam range, and the choice of beam directions. Simulations revealed that small modifications to certain plan parameters such as beam isocenter (up to 19 mm) and gantry angle (up to 10°) are sufficient to compensate for the magnetic field-induced dose disturbances. The authors’ observations indicate that the degree of required

  12. SU-E-T-613: Dosimetric Consequences of Systematic MLC Leaf Positioning Errors

    SciTech Connect

    Kathuria, K; Siebers, J

    2014-06-01

    Purpose: The purpose of this study is to determine the dosimetric consequences of systematic MLC leaf positioning errors for clinical IMRT patient plans so as to establish detection tolerances for quality assurance programs. Materials and Methods: Dosimetric consequences were simulated by extracting mlc delivery instructions from the TPS, altering the file by the specified error, reloading the delivery instructions into the TPS, recomputing dose, and extracting dose-volume metrics for one head-andneck and one prostate patient. Machine error was simulated by offsetting MLC leaves in Pinnacle in a systematic way. Three different algorithms were followed for these systematic offsets, and are as follows: a systematic sequential one-leaf offset (one leaf offset in one segment per beam), a systematic uniform one-leaf offset (same one leaf offset per segment per beam) and a systematic offset of a given number of leaves picked uniformly at random from a given number of segments (5 out of 10 total). Dose to the PTV and normal tissue was simulated. Results: A systematic 5 mm offset of 1 leaf for all delivery segments of all beams resulted in a maximum PTV D98 deviation of 1%. Results showed very low dose error in all reasonably possible machine configurations, rare or otherwise, which could be simulated. Very low error in dose to PTV and OARs was shown in all possible cases of one leaf per beam per segment being offset (<1%), or that of only one leaf per beam being offset (<.2%). The errors resulting from a high number of adjacent leaves (maximum of 5 out of 60 total leaf-pairs) being simultaneously offset in many (5) of the control points (total 10–18 in all beams) per beam, in both the PTV and the OARs analyzed, were similarly low (<2–3%). Conclusions: The above results show that patient shifts and anatomical changes are the main source of errors in dose delivered, not machine delivery. These two sources of error are “visually complementary” and uncorrelated

  13. Dosimetric characteristics of four PTW microDiamond detectors in high-energy proton beams.

    PubMed

    Marsolat, F; De Marzi, L; Patriarca, A; Nauraye, C; Moignier, C; Pomorski, M; Moignau, F; Heinrich, S; Tromson, D; Mazal, A

    2016-09-01

    Small diamond detectors are useful for the dosimetry of high-energy proton beams. However, linear energy transfer (LET) dependence has been observed in the literature with such solid state detectors. A novel synthetic diamond detector has recently become commercially available from the manufacturer PTW-Freiburg (PTW microDiamond type 60019). This study was designed to thoroughly characterize four microDiamond detectors in clinical proton beams, in order to investigate their response and their reproducibility in high LET regions. Very good dosimetric characteristics were observed for two of them, with good stability of their response (deviation less than 0.4% after a pre-irradiation dose of approximately 12 Gy), good repeatability (coefficient of variation of 0.06%) and a sensitivity of approximately 0.85 nC Gy(-1). A negligible dose rate dependence was also observed for these two microDiamonds with a deviation of the sensitivity less than 0.7% with respect to the one measured at the reference dose rate of 2.17 Gy min(-1), in the investigated dose rate range from 1.01 Gy min(-1) to 5.52 Gy min(-1). Lateral dose profile measurements showed the high spatial resolution of the microDiamond oriented with its stem perpendicular to the beam axis and with its small sensitive thickness of about 1 μm in the scanning profile direction. Finally, no significant LET dependence was found with these two diamond dosimeters in comparison to a reference ionization chamber (model IBA PPC05). These good results were in accordance to the literature. However, this study showed also a non reproducibility between the devices in terms of stability, sensitivity and LET dependence, since the two other microDiamonds characterized in this work showed different dosimetric characteristics making them not suitable for proton beam dosimetry with a maximum difference of the peak-to-plateau ratio of 6.7% relative to the reference ionization chamber in a clinical 138 MeV proton beam. PMID:27499356

  14. Dosimetric Comparison Between 3-Dimensional Conformal and Robotic SBRT Treatment Plans for Accelerated Partial Breast Radiotherapy.

    PubMed

    Goggin, L M; Descovich, M; McGuinness, C; Shiao, S; Pouliot, J; Park, C

    2016-06-01

    Accelerated partial breast irradiation is an attractive alternative to conventional whole breast radiotherapy for selected patients. Recently, CyberKnife has emerged as a possible alternative to conventional techniques for accelerated partial breast irradiation. In this retrospective study, we present a dosimetric comparison between 3-dimensional conformal radiotherapy plans and CyberKnife plans using circular (Iris) and multi-leaf collimators. Nine patients who had undergone breast-conserving surgery followed by whole breast radiation were included in this retrospective study. The CyberKnife planning target volume (PTV) was defined as the lumpectomy cavity + 10 mm + 2 mm with prescription dose of 30 Gy in 5 fractions. Two sets of 3-dimensional conformal radiotherapy plans were created, one used the same definitions as described for CyberKnife and the second used the RTOG-0413 definition of the PTV: lumpectomy cavity + 15 mm + 10 mm with prescription dose of 38.5 Gy in 10 fractions. Using both PTV definitions allowed us to compare the dose delivery capabilities of each technology and to evaluate the advantage of CyberKnife tracking. For the dosimetric comparison using the same PTV margins, CyberKnife and 3-dimensional plans resulted in similar tumor coverage and dose to critical structures, with the exception of the lung V5%, which was significantly smaller for 3-dimensional conformal radiotherapy, 6.2% when compared to 39.4% for CyberKnife-Iris and 17.9% for CyberKnife-multi-leaf collimator. When the inability of 3-dimensional conformal radiotherapy to track motion is considered, the result increased to 25.6%. Both CyberKnife-Iris and CyberKnife-multi-leaf collimator plans demonstrated significantly lower average ipsilateral breast V50% (25.5% and 24.2%, respectively) than 3-dimensional conformal radiotherapy (56.2%). The CyberKnife plans were more conformal but less homogeneous than the 3-dimensional conformal radiotherapy plans. Approximately 50% shorter

  15. Predictive dosimetric parameters for gastrointestinal toxicity with hypofractioned radiotherapy in pancreatic adenocarcinoma

    PubMed Central

    Liu, Xian; Ren, Gang; Li, Liqin; Xia, Tingyi

    2016-01-01

    To better guide the development and optimization of radiotherapy planning, to reduce the incidence of radiation reactions, and to improve the quality of life of the patients with pancreatic cancer using radiotherapy, we conducted this study to explore the dosimetric parameters that predict the risk of gastrointestinal (GI) toxicity with hypofractioned radiotherapy for pancreatic cancer. Between January 2014 and January 2015, the medical records of 68 patients with pancreatic cancer who underwent helical tomotherapy at the Air Force General Hospital were analyzed. The doses delivered to the planning target volume, clinical target volume, and gross tumor volume–internal gross tumor volume of the primary pancreatic lesions were 50, 60, and 70–80 Gy in 15–20 fractions, respectively. GI toxicity was scored according to version 4.0 of the National Cancer Institute Common Terminology Criteria for Adverse Events. The stomach and duodenum were contoured separately to determine the dose–volume histogram parameters. Univariate and multivariate analyses were adopted to identify clinical and physical risk factors associated with GI toxicity. The median follow-up was 9 months (range: 4–16 months). Eighteen patients had grade II acute GI toxicity, one patient had grade III acute GI toxicity, 17 patients had grade II late GI toxicity, and one patient had grade III late GI toxicity. On univariate analysis, the volume, the average dose Dmean, the maximum dose to 1, 3, 5, and 10 cm3 of the stomach and duodenum (D1, D3, D5, and D10), and the relative volumes receiving 5–40 Gy (V5–V40), and the absolute volumes receiving 5–45 Gy (aV5–aV45) of the duodenum were significantly associated with grade II or higher GI toxicity (P<0.05). On multivariate analysis, aV45 of the duodenum was an independent predictor for grade II or higher GI toxicity (P=0.031). The receiver operating characteristic analysis also showed that an aV45 of 0.5 cm3 was the optimal threshold to predict

  16. The dosimetric impact of dental implants on head-and-neck volumetric modulated arc therapy

    NASA Astrophysics Data System (ADS)

    Lin, Mu-Han; Li, Jinsheng; Price, Robert A., Jr.; Wang, Lu; Lee, Chung-Chi; Ma, C.-M.

    2013-02-01

    This work aims to investigate the dosimetric impact of dental implants on volumetric modulated arc therapy (VMAT) for head-and-neck patients and to evaluate the effectiveness of using the material's electron-density ratio for the correction. An in-house Monte Carlo (MC) code was utilized for the dose calculation to account for the scattering and attenuation caused by the high-Z implant material. Three different dental implant materials were studied in this work: titanium, Degubond®4 and gold. The dose perturbations caused by the dental implant materials were first investigated in a water phantom with a 1 cm3 insert. The per cent depth dose distributions of a 3 × 3 cm2 photon field were compared with the insert material as water and the three selected dental implant materials. To evaluate the impact of the dental implant on VMAT patient dose calculation, four head-and-neck cases were selected. For each case, the VMAT plan was designed based on the artifact-corrected patient geometry using a treatment planning system (TPS) that was typically utilized for routine patient treatment. The plans were re-calculated using the MC code for five situations: uncorrected geometry, artifact-corrected geometry and artifact-corrected geometry with one of the three different implant materials. The isodose distributions and the dose-volume histograms were cross-compared with each other. To evaluate the effectiveness of using the material's electron-density ratio for dental implant correction, the implant region was set as water with the material's electron-density ratio and the calculated dose was compared with the MC simulation with the real material. The main effect of the dental implant was the severe attenuation in the downstream. The 1 cm3 dental implant can lower the downstream dose by 10% (Ti) to 51% (Au) for a 3 × 3 cm2 field. The TPS failed to account for the dose perturbation if the dental implant material was not precisely defined. For the VMAT patient dose calculation

  17. Dosimetric effects on small-field beam-modeling for stereotactic body radiation therapy

    NASA Astrophysics Data System (ADS)

    Cho, Woong; Kim, Suzy; Kim, Jung-In; Wu, Hong-Gyun; Jung, Joo-Young; Kim, Min-Joo; Suh, Tae-Suk; Kim, Jin-Young; Kim, Jong Won

    2015-02-01

    The treatment planning of stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT) requires high accuracy of dosimetric data for small radiation fields. The dosimetric effects on the beam-modeling process of a treatment planning system (TPS) were investigated using different measured small-field data sets. We performed small-field dosimetry with three detectors: a CC13 ion chamber, a CC01 ion chamber, and an edge detector. Percentage depth doses (PDDs) and dose profiles for field sizes given by 3 × 3 cm2, 2 × 2 cm2, and 1 × 1 cm2 were obtained for 6 MV and 15 MV photon beams. Each measured data set was used as data input for a TPS, in which a beam-modeling process was implemented using the collapsed cone convolution (CCC) algorithm for dose calculation. The measured data were used to generate six beam-models based on each combination of detector type and photon energy, which were then used to calculate the corresponding PDDs and dose profiles for various depths and field sizes. Root mean square differences (RMSDs) between the calculated and the measured doses were evaluated for the PDDs and the dose profiles. The RMSDs of PDDs beyond the maximum dose depth were within an accuracy of 0.2-0.6%, being clinically acceptable. The RMSDs of the dose profiles corresponding to the CC13, the CC01, and the edge detector were 2.80%, 1.49%, and 1.46% for a beam energy of 6 MV and 2.34%, 1.15%, and 1.44% for a beam energy of 15 MV, respectively. The calculated results for the CC13 ion chamber showed the most discrepancy compared to the measured data, due to the relatively large sensitive volume of this detector. However, the calculated dose profiles for the detectors were not significantly different from another. The physical algorithm used in the beam-modeling process did not seem to be sensitive to blurred data measured with detectors with large sensitive volumes. Each beam-model was used to clinically evaluate lung and lymphatic node SBRT plans

  18. Characterization of optically stimulated luminescent dosimeters, OSLDs, for clinical dosimetric measurements

    SciTech Connect

    Jursinic, Paul A.

    2007-12-15

    Optically stimulated luminescent dosimeters, OSLDs, are plastic disks infused with aluminum oxide doped with carbon (Al{sub 2}O{sub 3}:C). These disks are encased in a light-tight plastic holder. Crystals of Al{sub 2}O{sub 3}:C when exposed to ionizing radiation store energy that is released as luminescence (420 nm) when the OSLD is illuminated with stimulation light (540 nm). The intensity of the luminescence depends on the dose absorbed by the OSLD and the intensity of the stimulation light. OSLDs used in this work were InLight/OSL Dot dosimeters, which were read with a MicroStar reader (Landauer, Inc., Glenwood, IL). The following are dosimetric properties of the OSLD that were determined: After a single irradiation, repeated readings cause the signal to decrease by 0.05% per reading; the signal could be discharged by greater than 98% by illuminating them for more than 45 s with a 150 W tungsten-halogen light; after irradiation there was a transient signal that decayed with a 0.8 min halftime; after the transient signal decay the signal was stable for days; repeated irradiations and readings of an individual OSLD gave a signal with a coefficient of variation of 0.6%; the dose sensitivity of OSLDs from a batch of detectors has a coefficient of variation of 0.9%, response was linear with absorbed dose over a test range of 1-300 cGy; above 300 cGy a small supra-linear behavior occurs; there was no dose-per-pulse dependence over a 388-fold range; there was no dependence on radiation energy or mode for 6 and 15 MV x rays and 6-20 MeV electrons; for Ir-192 gamma rays OSLD had 6% higher sensitivity; the dose sensitivity was unchanged up to an accumulated dose of 20 Gy and thereafter decreased by 4% per 10 Gy of additional accumulated dose; dose sensitivity was not dependent on the angle of incidence of radiation; the OSLD in its light-tight case has an intrinsic buildup of 0.04 g/cm{sup 2}; dose sensitivity of the OSLD was not dependent on temperature at the time of

  19. Characterization of optically stimulated luminescent dosimeters, OSLDs, for clinical dosimetric measurements.

    PubMed

    Jursinic, Paul A

    2007-12-01

    Optically stimulated luminescent dosimeters, OSLDs, are plastic disks infused with aluminum oxide doped with carbon (Al2O3 : C). These disks are encased in a light-tight plastic holder. Crystals of Al2O3 : C when exposed to ionizing radiation store energy that is released as luminescence (420 nm) when the OSLD is illuminated with stimulation light (540 nm). The intensity of the luminescence depends on the dose absorbed by the OSLD and the intensity of the stimulation light. OSLDs used in this work were InLight/OSL Dot dosimeters, which were read with a MicroStar reader (Landauer, Inc., Glenwood, IL). The following are dosimetric properties of the OSLD that were determined: After a single irradiation, repeated readings cause the signal to decrease by 0.05% per reading; the signal could be discharged by greater than 98% by illuminating them for more than 45 s with a 150 W tungsten-halogen light; after irradiation there was a transient signal that decayed with a 0.8 min halftime; after the transient signal decay the signal was stable for days; repeated irradiations and readings of an individual OSLD gave a signal with a coefficient of variation of 0.6%; the dose sensitivity of OSLDs from a batch of detectors has a coefficient of variation of 0.9%, response was linear with absorbed dose over a test range of 1-300 cGy; above 300 cGy a small supra-linear behavior occurs; there was no dose-per-pulse dependence over a 388-fold range; there was no dependence on radiation energy or mode for 6 and 15 MV x rays and 6-20 MeV electrons; for Ir-192 gamma rays OSLD had 6% higher sensitivity; the dose sensitivity was unchanged up to an accumulated dose of 20 Gy and thereafter decreased by 4% per 10 Gy of additional accumulated dose; dose sensitivity was not dependent on the angle of incidence of radiation; the OSLD in its light-tight case has an intrinsic buildup of 0.04 g/cm2; dose sensitivity of the OSLD was not dependent on temperature at the time of irradiation in the range of

  20. Dosimetric characteristics of four PTW microDiamond detectors in high-energy proton beams

    NASA Astrophysics Data System (ADS)

    Marsolat, F.; De Marzi, L.; Patriarca, A.; Nauraye, C.; Moignier, C.; Pomorski, M.; Moignau, F.; Heinrich, S.; Tromson, D.; Mazal, A.

    2016-09-01

    Small diamond detectors are useful for the dosimetry of high-energy proton beams. However, linear energy transfer (LET) dependence has been observed in the literature with such solid state detectors. A novel synthetic diamond detector has recently become commercially available from the manufacturer PTW-Freiburg (PTW microDiamond type 60019). This study was designed to thoroughly characterize four microDiamond detectors in clinical proton beams, in order to investigate their response and their reproducibility in high LET regions. Very good dosimetric characteristics were observed for two of them, with good stability of their response (deviation less than 0.4% after a pre-irradiation dose of approximately 12 Gy), good repeatability (coefficient of variation of 0.06%) and a sensitivity of approximately 0.85 nC Gy‑1. A negligible dose rate dependence was also observed for these two microDiamonds with a deviation of the sensitivity less than 0.7% with respect to the one measured at the reference dose rate of 2.17 Gy min‑1, in the investigated dose rate range from 1.01 Gy min‑1 to 5.52 Gy min‑1. Lateral dose profile measurements showed the high spatial resolution of the microDiamond oriented with its stem perpendicular to the beam axis and with its small sensitive thickness of about 1 μm in the scanning profile direction. Finally, no significant LET dependence was found with these two diamond dosimeters in comparison to a reference ionization chamber (model IBA PPC05). These good results were in accordance to the literature. However, this study showed also a non reproducibility between the devices in terms of stability, sensitivity and LET dependence, since the two other microDiamonds characterized in this work showed different dosimetric characteristics making them not suitable for proton beam dosimetry with a maximum difference of the peak-to-plateau ratio of 6.7% relative to the reference ionization chamber in a clinical 138 MeV proton beam.

  1. Dosimetric comparison of volumetric modulated arc therapy and intensity-modulated radiation therapy for pancreatic malignancies

    SciTech Connect

    Ali, Arif N.; Dhabaan, Anees H.; Jarrio, Christie S.; Siddiqi, Arsalan K.; Landry, Jerome C.

    2012-10-01

    Volumetric-modulated arc therapy (VMAT) has been previously evaluated for several tumor sites and has been shown to provide significant dosimetric and delivery benefits when compared with intensity-modulated radiation therapy (IMRT). To date, there have been no published full reports on the benefits of VMAT use in pancreatic patients compared with IMRT. Ten patients with pancreatic malignancies treated with either IMRT or VMAT were retrospectively identified. Both a double-arc VMAT and a 7-field IMRT plan were generated for each of the 10 patients using the same defined tumor volumes, organs at risk (OAR) volumes, dose, fractionation, and optimization constraints. The planning tumor volume (PTV) maximum dose (55.8 Gy vs. 54.4 Gy), PTV mean dose (53.9 Gy vs. 52.1 Gy), and conformality index (1.11 vs. 0.99) were statistically similar between the IMRT and VMAT plans, respectively. The VMAT plans had a statistically significant reduction in monitor units compared with the IMRT plans (1109 vs. 498, p < 0.001). In addition, the doses to the liver, small bowel, and spinal cord were comparable between the IMRT and VMAT plans. However, the VMAT plans demonstrated a statistically significant reduction in the mean left kidney V{sub 25} (9.4 Gy vs. 2.3 Gy, p = 0.018), mean right kidney V{sub 15} (53.4 Gy vs. 45.9 Gy, p = 0.035), V{sub 20} (32.2 Gy vs. 25.5 Gy, p = 0.016), and V{sub 25} (21.7 Gy vs. 14.9 Gy, p = 0.001). VMAT was investigated in patients with pancreatic malignancies and compared with the current standard of IMRT. VMAT was found to have similar or improved dosimetric parameters for all endpoints considered. Specifically, VMAT provided reduced monitor units and improved bilateral kidney normal tissue dose. The clinical relevance of these benefits in the context of pancreatic cancer patients, however, is currently unclear and requires further investigation.

  2. SU-E-J-165: Dosimetric Impact of Liver Rotations in Stereotactic Body Radiation Therapy

    SciTech Connect

    Pinnaduwage, D; Paulsson, A; Sudhyadhom, A; Chen, J; Chang, A; Anwar, M; Gottschalk, A; Yom, S S.; Descovich, M

    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. Translational 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

  3. Dosimetric characterization of a microDiamond detector in clinical scanned carbon ion beams

    SciTech Connect

    Marinelli, Marco; Prestopino, G. Verona, C.; Verona-Rinati, G.; Ciocca, M.; Mirandola, A.; Mairani, A.; Raffaele, L.; Magro, G.

    2015-04-15

    Purpose: To investigate for the first time the dosimetric properties of a new commercial synthetic diamond detector (PTW microDiamond) in high-energy scanned clinical carbon ion beams generated by a synchrotron at the CNAO facility. Methods: The detector response was evaluated in a water phantom with actively scanned carbon ion beams ranging from 115 to 380 MeV/u (30–250 mm Bragg peak depth in water). Homogeneous square fields of 3 × 3 and 6 × 6 cm{sup 2} were used. Short- and medium-term (2 months) detector response stability, dependence on beam energy as well as ion type (carbon ions and protons), linearity with dose, and directional and dose-rate dependence were investigated. The depth dose curve of a 280 MeV/u carbon ion beam, scanned over a 3 × 3 cm{sup 2} area, was measured with the microDiamond detector and compared to that measured using a PTW Advanced Markus ionization chamber, and also simulated using FLUKA Monte Carlo code. The detector response in two spread-out-Bragg-peaks (SOBPs), respectively, centered at 9 and 21 cm depths in water and calculated using the treatment planning system (TPS) used at CNAO, was measured. Results: A negligible drift of detector sensitivity within the experimental session was seen, indicating that no detector preirradiation was needed. Short-term response reproducibility around 1% (1 standard deviation) was found. Only 2% maximum variation of microDiamond sensitivity was observed among all the evaluated proton and carbon ion beam energies. The detector response showed a good linear behavior. Detector sensitivity was found to be dose-rate independent, with a variation below 1.3% in the evaluated dose-rate range. A very good agreement between measured and simulated Bragg curves with both microDiamond and Advanced Markus chamber was found, showing a negligible LET dependence of the tested detector. A depth dose curve was also measured by positioning the microDiamond with its main axis oriented orthogonally to the beam

  4. Dosimetric feasibility of real-time MRI-guided proton therapy

    PubMed Central

    Moteabbed, M.; Schuemann, J.; Paganetti, H.

    2014-01-01

    Purpose: Magnetic resonance imaging (MRI) is a prime candidate for image-guided radiotherapy. This study was designed to assess the feasibility of real-time MRI-guided proton therapy by quantifying the dosimetric effects induced by the magnetic field in patients’ plans and identifying the associated clinical consequences. Methods: Monte Carlo dose calculation was performed for nine patients of various treatment sites (lung, liver, prostate, brain, skull-base, and spine) and tissue homogeneities, in the presence of 0.5 and 1.5 T magnetic fields. Dose volume histogram (DVH) parameters such as D95, D5, and V20 as well as equivalent uniform dose were compared for the target and organs at risk, before and after applying the magnetic field. The authors further assessed whether the plans affected by clinically relevant dose distortions could be corrected independent of the planning system. Results: By comparing the resulting dose distributions and analyzing the respective DVHs, it was determined that despite the observed lateral beam deflection, for magnetic fields of up to 0.5 T, neither was the target coverage jeopardized nor was the dose to the nearby organs increased in all cases except for prostate. However, for a 1.5 T magnetic field, the dose distortions were more pronounced and of clinical concern in all cases except for spine. In such circumstances, the target was severely underdosed, as indicated by a decrease in D95 of up to 41% of the prescribed dose compared to the nominal situation (no magnetic field). Sites such as liver and spine were less affected due to higher tissue homogeneity, typically smaller beam range, and the choice of beam directions. Simulations revealed that small modifications to certain plan parameters such as beam isocenter (up to 19 mm) and gantry angle (up to 10°) are sufficient to compensate for the magnetic field-induced dose disturbances. The authors’ observations indicate that the degree of required corrections strongly depends

  5. Effect of endorectal balloon positioning errors on target deformation and dosimetric quality during prostate SBRT

    NASA Astrophysics Data System (ADS)

    Jones, Bernard L.; Gan, Gregory; Kavanagh, Brian; Miften, Moyed

    2013-11-01

    An inflatable endorectal balloon (ERB) is often used during stereotactic body radiation therapy (SBRT) for treatment of prostate cancer in order to reduce both intrafraction motion of the target and risk of rectal toxicity. However, the ERB can exert significant force on the prostate, and this work assessed the impact of ERB position errors on deformation of the prostate and treatment dose metrics. Seventy-one cone-beam computed tomography (CBCT) image datasets of nine patients with clinical stage T1cN0M0 prostate cancer were studied. An ERB (Flexi-Cuff, EZ-EM, Westbury, NY) inflated with 60 cm3 of air was used during simulation and treatment, and daily kilovoltage (kV) CBCT imaging was performed to localize the prostate. The shape of the ERB in each CBCT was analyzed to determine errors in position, size, and shape. A deformable registration algorithm was used to track the dose received by (and deformation of) the prostate, and dosimetric values such as D95, PTV coverage, and Dice coefficient for the prostate were calculated. The average balloon position error was 0.5 cm in the inferior direction, with errors ranging from 2 cm inferiorly to 1 cm superiorly. The prostate was deformed primarily in the AP direction, and tilted primarily in the anterior-posterior/superior-inferior plane. A significant correlation was seen between errors in depth of ERB insertion (DOI) and mean voxel-wise deformation, prostate tilt, Dice coefficient, and planning-to-treatment prostate inter-surface distance (p < 0.001). Dosimetrically, DOI is negatively correlated with prostate D95 and PTV coverage (p < 0.001). For the model of ERB studied, error in ERB position can cause deformations in the prostate that negatively affect treatment, and this additional aspect of setup error should be considered when ERBs are used for prostate SBRT. Before treatment, the ERB position should be verified, and the ERB should be adjusted if the error is observed to exceed tolerable values.

  6. An evaluation of a novel synthetic diamond probe for dosimetric applications

    NASA Astrophysics Data System (ADS)

    Ade, N.; Nam, T. L.

    2015-10-01

    A study is presented that characterises the dosimetric performances of two synthetic diamond sensors (HP1 and HP2) when either one or both detectors are subjected to clinical beams of various types under large as well as small-field conditions. Detector performances were evaluated using a prototype probe housing constructed of tissue-equivalent materials. The probe can accommodate diamond sensors of various sizes and is configured for radiation detection in different exposure orientations without having first to re-orient the sensor plate within its body. Also, the diamond sensor is aligned in the same configuration as its rectangular housing and the probe is designed to be compatible with commercially available electrometer systems. Dosimetric measurements were conducted using mammography X-rays (25-32 kVp) and megavoltage electron (6-21 MeV) and photon (60Co γ-ray, 6-18 MV X-ray) beams. Whereas HP1 was evaluated using all beam types under large-flied conditions and small-photon-beam fields down to 0.7×0.7 cm2, HP2 was evaluated using small-electron and photon-beam conditions down to 0.3×0.3 cm2 6 MV photon field. Using HP1 sensor, the synthetic diamond probe was found not to require daily pre-irradiation as long as it is properly shielded from ambient light and its response stabilised. Furthermore, the diamond probe exhibited linear response characteristics with absorbed dose and on exposure parameters to various beam types, negligible energy dependence and almost no variation in angular response. Exposing the sensor HP2 under a 0.4×0.4 cm2 6 MV photon radiation field, a sensitivity value of 197.3 nC Gy-1 mm-3 was established compared to a value of 136.1 nC Gy-1 mm-3 obtained with a small-field diode detector. Also, a figure of 5.5×103 for the SNR was established for the sensor in the same radiation field. Relative beam data measured with the diamond sensors were found to agree within 1-2% with data obtained with reference detectors. The presentation

  7. Quantitative dosimetric assessment for effect of gold nanoparticles as contrast media on radiotherapy planning

    NASA Astrophysics Data System (ADS)

    Tu, Shu-Ju; Yang, Pei-Ying; Hong, Ji-Hong; Lo, Ching-Jung

    2013-07-01

    In CT planning for radiation therapy, patients may be asked to have a medical procedure of contrast agent (CA) administration as required by their physicians. CA media improve quality of CT images and assist radiation oncologists in delineation of the target or organs with accuracy. However, dosimetric discrepancy may occur between scenarios in which CA media are present in CT planning and absent in treatment delivery. In recent preclinical experiments of small animals, gold nanoparticles (AuNPs) have been identified as an excellent contrast material of x-ray imaging. In this work, we quantitatively evaluate the effect of AuNPs to be used as a potential material of contrast enhancement in radiotherapy planning with an analytical phantom and clinical case. Conray 60, an iodine-based product for contrast enhancement in clinical uses, is included as a comparison. Other additional variables such as different concentrations of CA media, radiation delivery techniques and dose calculation algorithms are included. We consider 1-field AP, 4-field box, 7-field intensity modulated radiation therapy (IMRT) and a recent technique of volumetric modulated arc therapy (VMAT). CA media of AuNPs (Conray 60) with concentrations of 10%, 20%, 30%, 40% and 50% containing 28.2, 56.4, 84.6, 112.8 and 141.0 mg of gold (iodine) per mL were prepared prior to CT scanning. A virtual phantom with a target where nanoparticle media are loaded and clinical case of gastric lymphoma in which the Conray 60 media were given to the patient prior to the CT planning are included for the study. Compared to Conray 60 media with concentration of 10%/50%, Hounsfield units for AuNP media of 10%/50% are 322/1608 higher due to the fact that atomic number of Au (Z=79) is larger than I (Z=53). In consequence, dosimetric discrepancy of AuNPs is magnified between presence and absence of contrast media. It was found in the phantom study that percent dose differences between presence and absence of CA media may be

  8. Dosimetric characteristics of four PTW microDiamond detectors in high-energy proton beams

    NASA Astrophysics Data System (ADS)

    Marsolat, F.; De Marzi, L.; Patriarca, A.; Nauraye, C.; Moignier, C.; Pomorski, M.; Moignau, F.; Heinrich, S.; Tromson, D.; Mazal, A.

    2016-09-01

    Small diamond detectors are useful for the dosimetry of high-energy proton beams. However, linear energy transfer (LET) dependence has been observed in the literature with such solid state detectors. A novel synthetic diamond detector has recently become commercially available from the manufacturer PTW-Freiburg (PTW microDiamond type 60019). This study was designed to thoroughly characterize four microDiamond detectors in clinical proton beams, in order to investigate their response and their reproducibility in high LET regions. Very good dosimetric characteristics were observed for two of them, with good stability of their response (deviation less than 0.4% after a pre-irradiation dose of approximately 12 Gy), good repeatability (coefficient of variation of 0.06%) and a sensitivity of approximately 0.85 nC Gy-1. A negligible dose rate dependence was also observed for these two microDiamonds with a deviation of the sensitivity less than 0.7% with respect to the one measured at the reference dose rate of 2.17 Gy min-1, in the investigated dose rate range from 1.01 Gy min-1 to 5.52 Gy min-1. Lateral dose profile measurements showed the high spatial resolution of the microDiamond oriented with its stem perpendicular to the beam axis and with its small sensitive thickness of about 1 μm in the scanning profile direction. Finally, no significant LET dependence was found with these two diamond dosimeters in comparison to a reference ionization chamber (model IBA PPC05). These good results were in accordance to the literature. However, this study showed also a non reproducibility between the devices in terms of stability, sensitivity and LET dependence, since the two other microDiamonds characterized in this work showed different dosimetric characteristics making them not suitable for proton beam dosimetry with a maximum difference of the peak-to-plateau ratio of 6.7% relative to the reference ionization chamber in a clinical 138 MeV proton beam.

  9. MO-G-17A-04: Internal Dosimetric Calculations for Pediatric Nuclear Imaging Applications, Using Monte Carlo Simulations and High-Resolution Pediatric Computational Models

    SciTech Connect

    Papadimitroulas, P; Kagadis, GC; Loudos, G

    2014-06-15

    Purpose: Our purpose is to evaluate the administered absorbed dose in pediatric, nuclear imaging studies. Monte Carlo simulations with the incorporation of pediatric computational models can serve as reference for the accurate determination of absorbed dose. The procedure of the calculated dosimetric factors is described, while a dataset of reference doses is created. Methods: Realistic simulations were executed using the GATE toolkit and a series of pediatric computational models, developed by the “IT'IS Foundation”. The series of the phantoms used in our work includes 6 models in the range of 5–14 years old (3 boys and 3 girls). Pre-processing techniques were applied to the images, to incorporate the phantoms in GATE simulations. The resolution of the phantoms was set to 2 mm3. The most important organ densities were simulated according to the GATE “Materials Database”. Several used radiopharmaceuticals in SPECT and PET applications are being tested, following the EANM pediatric dosage protocol. The biodistributions of the several isotopes used as activity maps in the simulations, were derived by the literature. Results: Initial results of absorbed dose per organ (mGy) are presented in a 5 years old girl from the whole body exposure to 99mTc - SestaMIBI, 30 minutes after administration. Heart, kidney, liver, ovary, pancreas and brain are the most critical organs, in which the S-factors are calculated. The statistical uncertainty in the simulation procedure was kept lower than 5%. The Sfactors for each target organ are calculated in Gy/(MBq*sec) with highest dose being absorbed in kidneys and pancreas (9.29*10{sup 10} and 0.15*10{sup 10} respectively). Conclusion: An approach for the accurate dosimetry on pediatric models is presented, creating a reference dosage dataset for several radionuclides in children computational models with the advantages of MC techniques. Our study is ongoing, extending our investigation to other reference models and

  10. Concept Mapping

    PubMed Central

    Brennan, Laura K.; Brownson, Ross C.; Kelly, Cheryl; Ivey, Melissa K.; Leviton, Laura C.

    2016-01-01

    Background From 2003 to 2008, 25 cross-sector, multidisciplinary community partnerships funded through the Active Living by Design (ALbD) national program designed, planned, and implemented policy and environmental changes, with complementary programs and promotions. This paper describes the use of concept-mapping methods to gain insights into promising active living intervention strategies based on the collective experience of community representatives implementing ALbD initiatives. Methods Using Concept Systems software, community representatives (n=43) anonymously generated actions and changes in their communities to support active living (183 original statements, 79 condensed statements). Next, respondents (n=26, from 23 partnerships) sorted the 79 statements into self-created categories, or active living intervention approaches. Respondents then rated statements based on their perceptions of the most important strategies for creating community changes (n=25, from 22 partnerships) and increasing community rates of physical activity (n=23, from 20 partnerships). Cluster analysis and multidimensional scaling were used to describe data patterns. Results ALbD community partnerships identified three active living intervention approaches with the greatest perceived importance to create community change and increase population levels of physical activity: changes to the built and natural environment, partnership and collaboration efforts, and land-use and transportation policies. The relative importance of intervention approaches varied according to subgroups of partnerships working with different populations. Conclusions Decision makers, practitioners, and community residents can incorporate what has been learned from the 25 community partnerships to prioritize active living policy, physical project, promotional, and programmatic strategies for work in different populations and settings. PMID:23079266

  11. Maps & minds : mapping through the ages

    USGS Publications Warehouse

    ,

    1984-01-01

    Throughout time, maps have expressed our understanding of our world. Human affairs have been influenced strongly by the quality of maps available to us at the major turning points in our history. "Maps & Minds" traces the ebb and flow of a few central ideas in the mainstream of mapping. Our expanding knowledge of our cosmic neighborhood stems largely from a small number of simple but grand ideas, vigorously pursued.

  12. Mapping: A Course.

    ERIC Educational Resources Information Center

    Whitmore, Paul M.

    1988-01-01

    Reviews the history of cartography. Describes the contributions of Strabo and Ptolemy in early maps. Identifies the work of Gerhard Mercator as the most important advancement in mapping. Discusses present mapping standards from history. (CW)

  13. Mapping with the Masses: Google Map Maker

    NASA Astrophysics Data System (ADS)

    Pfund, J.

    2008-12-01

    After some 15,000 years of map making, which saw the innovations of cardinal directions, map projections for a spherical earth, and GIS analysis, many parts of the world still appear as the "Dark Continent" on modern maps. Google Map Maker intends to shine a light on these areas by tapping into the power of the GeoWeb. Google Map Maker is a website which allows you to collaborate with others on one unified map to add, edit, locate, describe, and moderate map features, such as roads, cities, businesses, parks, schools and more, for certain regions of the world using Google Maps imagery. In this session, we will show some examples of how people are mapping with this powerful tool as well as what they are doing with the data. With Google Map Maker, you can become a citizen cartographer and join the global network of users helping to improve the quality of maps and local information in your region of interest. You are invited to map the world with us!

  14. Dosimetric impact of a CT metal artefact suppression algorithm for proton, electron and photon therapies.

    PubMed

    Wei, Jikun; Sandison, George A; Hsi, Wen-Chien; Ringor, Michael; Lu, Xiaoyi

    2006-10-21

    Accurate dose calculation is essential to precision radiation treatment planning and this accuracy depends upon anatomic and tissue electron density information. Modern treatment planning inhomogeneity corrections use x-ray CT images and calibrated scales of tissue CT number to electron density to provide this information. The presence of metal in the volume scanned by an x-ray CT scanner causes metal induced image artefacts that influence CT numbers and thereby introduce errors in the radiation dose distribution calculated. This paper investigates the dosimetric improvement achieved by a previously proposed x-ray CT metal artefact suppression technique when the suppressed images of a patient with bilateral hip prostheses are used in commercial treatment planning systems for proton, electron or photon therapies. For all these beam types, this clinical image and treatment planning study reveals that the target may be severely underdosed if a metal artefact-contaminated image is used for dose calculations instead of the artefact suppressed one. Of the three beam types studied, the metal artefact suppression is most important for proton therapy dose calculations, intermediate for electron therapy and least important for x-ray therapy but still significant. The study of a water phantom having a metal rod simulating a hip prosthesis indicates that CT numbers generated after image processing for metal artefact suppression are accurate and thus dose calculations based on the metal artefact suppressed images will be of high fidelity.

  15. Dosimetric consequences of pencil beam width variations in scanned beam particle therapy

    NASA Astrophysics Data System (ADS)

    Chanrion, M. A.; Ammazzalorso, F.; Wittig, A.; Engenhart-Cabillic, R.; Jelen, U.

    2013-06-01

    Scanned ion beam delivery enables the highest degree of target dose conformation attainable in external beam radiotherapy. Nominal pencil beam widths (spot sizes) are recorded during treatment planning system commissioning. Due to changes in the beam-line optics, the actual spot sizes may differ from these commissioning values, leading to differences between planned and delivered dose. The purpose of this study was to analyse the dosimetric consequences of spot size variations in particle therapy treatment plans. For 12 patients with skull base tumours and 12 patients with prostate carcinoma, scanned-beam carbon ion and proton treatment plans were prepared and recomputed simulating spot size changes of (1) ±10% to simulate the typical magnitude of fluctuations, (2) ±25% representing the worst-case scenario and (3) ±50% as a part of a risk analysis in case of fault conditions. The primary effect of the spot size variation was a dose deterioration affecting the target edge: loss of target coverage and broadening of the lateral penumbra (increased spot size) or overdosage and contraction of the lateral penumbra (reduced spot size). For changes ⩽25%, the resulting planning target volume mean 95%-isodose line coverage (CI-95%) deterioration was ranging from negligible to moderate. In some cases changes in the dose to adjoining critical structures were observed.

  16. Effect of the collimator angle on dosimetric verification of volumetric modulated arc therapy

    NASA Astrophysics Data System (ADS)

    Kim, Yong Ho; Park, Ha Ryung; Kim, Won Taek; Kim, Dong Won; Ki, Yongkan; Lee, Juhye; Bae, Jinsuk; Park, Dahl; Jeon, Hosang; Nam, Ji Ho

    2015-07-01

    The collimator is usually rotated when planning volumetric modulated arc therapy (VMAT) due to the leakage of radiation between the multi-leaf collimator (MLC) leaves. We studied the effect of the collimator angle on the results of dosimetric verification of VMAT plans for head and neck patients. We studied VMAT plans for 10 head and neck patients. We made two sets of VMAT plans for each patient. Each set was composed of 10 plans with collimator angles of 0, 5, 10, 15, 20, 25, 30, 35, 40, 45 degrees. Plans in the first set were optimized individually, and plans in the second set shared the 30-degree collimator-angle optimization. The two sets of plans were verified by using the 2-dimensional ion chamber array MatriXX (IBA Dosimetry, Germany). The comparisons between the calculation and the measurements were made by using a γ-index analysis. The γ-index (2%/2 mm) and (3%/3 mm) passing rates had negative correlations with the collimator angle. The maximum difference between γ-index (3%/3 mm) passing rates of different collimator angles for each patient ranged from 1.46% to 5.60% with an average of 3.67%. There were significant differences (maximum 5.6%) in the passing rates for different collimator angles. The results suggested that the accuracy of the delivered dose depended on the collimator angle. These findings are informative when choosing a collimator angle for VMAT plans.

  17. The Application of Elliptic Cylindrical Phantom in Brachytherapy Dosimetric Study of HDR 192Ir Source

    NASA Astrophysics Data System (ADS)

    Ahn, Woo Sang; Park, Sung Ho; Jung, Sang Hoon; Choi, Wonsik; Do Ahn, Seung; Shin, Seong Soo

    2014-06-01

    The purpose of this study is to determine the radial dose function of HDR 192Ir source based on Monte Carlo simulation using elliptic cylindrical phantom, similar to realistic shape of pelvis, in brachytherapy dosimetric study. The elliptic phantom size and shape was determined by analysis of dimensions of pelvis on CT images of 20 patients treated with brachytherapy for cervical cancer. The radial dose function obtained using the elliptic cylindrical water phantom was compared with radial dose functions for different spherical phantom sizes, including the Williamsion's data loaded into conventional planning system. The differences in the radial dose function for the different spherical water phantoms increase with radial distance, r, and the largest differences in the radial dose function appear for the smallest phantom size. The radial dose function of the elliptic cylindrical phantom significantly decreased with radial distance in the vertical direction due to different scatter condition in comparison with the Williamson's data. Considering doses to ICRU rectum and bladder points, doses to reference points can be underestimated up to 1-2% at the distance from 3 to 6 cm. The radial dose function in this study could be used as realistic data for calculating the brachytherapy dosimetry for cervical cancer.

  18. Monte Carlo modelling the dosimetric effects of electrode material on diamond detectors.

    PubMed

    Baluti, Florentina; Deloar, Hossain M; Lansley, Stuart P; Meyer, Juergen

    2015-03-01

    Diamond detectors for radiation dosimetry were modelled using the EGSnrc Monte Carlo code to investigate the influence of electrode material and detector orientation on the absorbed dose. The small dimensions of the electrode/diamond/electrode detector structure required very thin voxels and the use of non-standard DOSXYZnrc Monte Carlo model parameters. The interface phenomena was investigated by simulating a 6 MV beam and detectors with different electrode materials, namely Al, Ag, Cu and Au, with thickens of 0.1 µm for the electrodes and 0.1 mm for the diamond, in both perpendicular and parallel detector orientation with regards to the incident beam. The smallest perturbations were observed for the parallel detector orientation and Al electrodes (Z = 13). In summary, EGSnrc Monte Carlo code is well suited for modelling small detector geometries. The Monte Carlo model developed is a useful tool to investigate the dosimetric effects caused by different electrode materials. To minimise perturbations cause by the detector electrodes, it is recommended that the electrodes should be made from a low-atomic number material and placed parallel to the beam direction.

  19. Radiation sensitivity and EPR dosimetric potential of gallic acid and its esters

    NASA Astrophysics Data System (ADS)

    Tuner, Hasan; Oktay Bal, M.; Polat, Mustafa

    2015-02-01

    In the preset work the radiation sensitivities of Gallic Acid anhydrous and monohydrate, Octyl, Lauryl, and Ethyl Gallate (GA, GAm, OG, LG, and EG) were investigated in the intermediate (0.5-20 kGy) and low radiation (<10 Gy) dose range using Electron Paramagnetic Resonance (EPR) spectroscopy. While OG, LG, and EG are presented a singlet EPR spectra, their radiation sensitivity found to be very different in the intermediate dose range. At low radiation dose range (<10 Gy) only LG is found to be present a signal that easily distinguished from the noise signals. The intermediate and low dose range radiation sensitivities are compared using well known EPR dosimeter alanine. The radiation yields (G) of the interested material were found to be 1.34×10-2, 1.48×10-2, 4.14×10-2, and 6.03×10-2, 9.44×10-2 for EG, GA, GAm, OG, and LG, respectively at the intermediate dose range. It is found that the simple EPR spectra and the noticeable EPR signal of LG make it a promising dosimetric material to be used below 10 Gy of radiation dose.

  20. Dosimetric analysis of the use of CBCT in diagnostic radiology: sinus and middle ear.

    PubMed

    Dierckx, D; Saldarriaga Vargas, C; Rogge, F; Lichtherte, S; Struelens, L

    2015-01-01

    The use of cone beam computed tomography (CBCT) in diagnostic radiology departments is increasing. Several discussions arise whether with the CBCT application, some multi-slice CT (MSCT) examinations can be replaced by it. High hopes are set regarding the dosimetric aspects of CBCT: are patient doses in between those of conventional X-rays and MSCT? In this study, effective dose and organ doses were evaluated for two non-dental CBCT examinations: sinus and middle ear. A comparison with the dose obtained with a MSCT protocol was performed. Moreover, the sinus examination was also compared with the dose obtained by projection radiography (RX). Effective doses were estimated from thermoluminescent detector dose measurements in an anthropomorphic phantom and were compared against Monte Carlo simulations. Results show that the effective dose for the sinus examination is more than three times higher with MSCT than with CBCT and about five times lower with RX compared with CBCT, whereas for the middle ear examination, the effective dose obtained with MSCT is almost six times higher than that of CBCT. Finally, a sensitivity study on the size and position of the CBCT field of view showed the influence of these two factors on the dose received by the patient.

  1. Optimization of Internal Margin to Account for Dosimetric Effects of Respiratory Motion

    SciTech Connect

    Mutaf, Yildirim D. Brinkmann, Debra H.

    2008-04-01

    Purpose: Use of internal margins to account for respiratory motion of the target volumes is a common strategy in radiotherapy of mobile tumors. Although efficient for tumor coverage, this expansion also risks increased toxicity to nearby healthy organs and therefore requires a careful selection of appropriate margins. In this study, we demonstrate an optimization of the internal margin used to account for respiration motion. Methods and Materials: Three-dimensional conformal treatment plans for phantom spherical target volumes as well as clinical treatment plans of 11 patients were evaluated retrospectively for optimum internal margin selection. A software-based simulation of respiration motion was performed for all cases. Moreover, the interplay with treatment setup uncertainties and corresponding margins was investigated in the phantom study. Results: Optimum internal margins in both phantom and patient studies were found to be substantially smaller than the actual target displacement due to respiration. The optimal internal margin was also observed to be approximately independent of the setup margins. Furthermore, no statistically significant dependence on target size and shape was observed in the group of 11 patients. Conclusions: These findings present significant implications for treatment planning of mobile targets, such as tumors found in the lung and upper abdomen. We conclude that the full motion amplitude for the internal margin is overly conservative, and optimization of the internal margin provides improved sparing of nearby organs at risk without sacrificing dosimetric coverage for the target.

  2. Potential application of metal nanoparticles for dosimetric systems: Concepts and perspectives

    SciTech Connect

    Guidelli, Eder José Baffa, Oswaldo

    2014-11-07

    Metallic nanoparticles increase the delivered dose and consequently enhance tissue radio sensitization during radiation therapy of cancer. The Dose Enhancement Factor (DEF) corresponds to the ratio between the dose deposited on a tissue containing nanoparticles, and the dose deposited on a tissue without nanoparticles. In this sense, we have used electron spin resonance spectroscopy (ESR) to investigate how silver and gold nanoparticles affect the dose deposition in alanine dosimeters, which act as a surrogate of soft tissue. Besides optimizing radiation absorption by the dosimeter, the optical properties of these metal nanoparticles could also improve light emission from materials employed as radiation detectors. Therefore, we have also examined how the plasmonic properties of noble metal nanoparticles could enhance radiation detection using optically stimulated luminescence (OSL) dosimetry. This work will show results on how the use of gold and silver nanoparticles are beneficial for the ESR and OSL dosimetric techniques, and will describe the difficulties we have been facing, the challenges to overcome, and the perspectives.

  3. The Use of 4DCT to Reduce Lung Dose: A Dosimetric Analysis

    SciTech Connect

    Khan, Fazal; Bell, Glenn; Antony, Jacob; Palmer, Matt; Balter, Peter; Bucci, Kara; Chapman, Melissa Jane

    2009-01-01

    Dosimetric studies on respiratory movement suggest several advantages toward the use of 4-dimensional computed tomography (4DCT) in radiation treatment planning. 4DCT is a method to obtain a series of CT scans each representing a different respiratory phase. The use of 4DCT has provided substantial information on tumor movement in the lung, allowing for the creation of custom planning margins explicitly including respiratory motion. These custom motion margins may result in an increase in the amount of normal lung in the field; however, it is believed less normal lung is irradiated than if generic motion margins were used. Clinical data regarding dose to normal lung by using 4DCT remain rather limited. Thus, a study presenting figures on the change in normal lung dose between planned free breathing CT and 4DCT cases would be useful to the dosimetry community. We have generated plans comparing fast spiral CT and 4DCT in regard to tumor coverage and the resulting dose to normal lung for the clinical target volume (CTV) and planning target volume (PTV) expansions used at our institution. These data were analyzed for free breathing and 4D plans of 6 lung cancer patients using intensity modulated radiation therapy (IMRT). We compared doses to normal lung tissue between free breathing and 4DCT plans.

  4. Dosimetric evaluations of the interplay effect in respiratory-gated intensity-modulated radiation therapy

    SciTech Connect

    Chen Hungcheng; Wu, Andrew; Brandner, Edward D.; Heron, Dwight E.; Huq, M. Saiful; Yue, Ning J.; Chen Wencheng

    2009-03-15

    The interplay between a mobile target and a dynamic multileaf collimator can compromise the accuracy of intensity-modulated radiation therapy (IMRT). Our goal in this study is to investigate the dosimetric effects caused by the respiratory motion during IMRT. A moving phantom was built to simulate the typical breathing motion. Different sizes of the gating windows were selected for gated deliveries. The residual motions during the beam-on period ranged from 0.5 to 3 cm. An IMRT plan with five treatment fields from different gantry angles were delivered to the moving phantom for three irradiation conditions: Stationary condition, moving with the use of gating system, and moving without the use of gating system. When the residual motion was 3 cm, the results showed significant differences in dose distributions between the stationary condition and the moving phantom without gating beam control. The overdosed or underdosed areas enclosed about 33% of the treatment area. In contrast, the dose distribution on the moving phantom with gating window set to 0.5 cm showed no significant differences from the stationary phantom. With the appropriate setting of the gating window, the deviation of dose from the respiratory motion can be minimized. It appeals that limiting the residual motion to less than 0.5 cm is critical for the treatments of mobile structures.

  5. Dosimetric shield evaluation with tungsten sheet in 4, 6, and 9MeV electron beams.

    PubMed

    Fujimoto, Takahiro; Monzen, Hajime; Nakata, Manabu; Okada, Takashi; Yano, Shinsuke; Takakura, Toru; Kuwahara, Junichi; Sasaki, Makoto; Higashimura, Kyoji; Hiraoka, Masahiro

    2014-11-01

    In electron radiotherapy, shielding material is required to attenuate beam and scatter. A newly introduced shielding material, tungsten functional paper (TFP), has been anticipated to become a very useful device that is lead-free, light, flexible, and easily processed, containing very fine tungsten powder at as much as 80% by weight. The purpose of this study was to investigate the dosimetric changes due to TFP shielding for electron beams. TFP (thickness 0-15mm) was placed on water or a water-equivalent phantom. Percentage depth ionization and transmission were measured for 4, 6, and 9MeV electron beams. Off-center ratio was also measured using film dosimetry at depth of dose maximum under similar conditions. Then, beam profiles and transmission with two shielding materials, TFP and lead, were evaluated. Reductions of 95% by using TFP at 0.5cm depth occurred at 4, 9, and 15mm with 4, 6, and 9MeV electron beams, respectively. It is found that the dose tend to increase at the field edge shaped with TFP, which might be influenced by the thickness. TFP has several unique features and is very promising as a useful tool for radiation protection for electron beams, among others.

  6. Study of the dosimetric characteristics of cosmic radiation at civil aviation altitudes.

    PubMed

    Ferrari, A; Pellicioni, M; Rancati, T

    2002-01-01

    The dependence of the doses on solar activity for intermediate levels of the solar modulation parameter has been studied by means of simulations carried out by the Monte Carlo transport code FLUKA. The vertical cut-off rigidities investigated lie between 0.4 and 6.1 GV. The calculated results show that the linear dependence proposed in a previous work, for the effective dose rate as a function of the solar modulation parameter, can be considered as an acceptable approximation. In addition, some dosimetric characteristics of cosmic radiation and some properties of the dosemeters in use for monitoring in the cosmic ray environment have been analysed with a view to simplifying measurements. The depth-dose curves in the ICRU sphere and the response of a tissue-equivalent ionisation chamber have been determined by the FLUKA code for a number of cosmic ray spectra On the basis of the calculated results, it is concluded that a value of the depth. d, which would make the ambient dose equivalent a conservative predictor of the effective dose, cannot be specified for cosmic radiation. However, the operational quantity can be useful in order to verify the predictions of Monte Carlo calculations. It is demonstrated that a crude approximation of the ambient dose equivalent could be obtained by multiplying by 2 the absorbed dose measured by a tissue-equivalent ionisation chamber with wall thickness of 10 mm.

  7. Potential application of metal nanoparticles for dosimetric systems: Concepts and perspectives

    NASA Astrophysics Data System (ADS)

    Guidelli, Eder José; Baffa, Oswaldo

    2014-11-01

    Metallic nanoparticles increase the delivered dose and consequently enhance tissue radio sensitization during radiation therapy of cancer. The Dose Enhancement Factor (DEF) corresponds to the ratio between the dose deposited on a tissue containing nanoparticles, and the dose deposited on a tissue without nanoparticles. In this sense, we have used electron spin resonance spectroscopy (ESR) to investigate how silver and gold nanoparticles affect the dose deposition in alanine dosimeters, which act as a surrogate of soft tissue. Besides optimizing radiation absorption by the dosimeter, the optical properties of these metal nanoparticles could also improve light emission from materials employed as radiation detectors. Therefore, we have also examined how the plasmonic properties of noble metal nanoparticles could enhance radiation detection using optically stimulated luminescence (OSL) dosimetry. This work will show results on how the use of gold and silver nanoparticles are beneficial for the ESR and OSL dosimetric techniques, and will describe the difficulties we have been facing, the challenges to overcome, and the perspectives.

  8. SU-E-T-237: Monte Carlo Dosimetric Characterization of the Mobetron Mobile Linac

    SciTech Connect

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

    2014-06-01

    Purpose: The aim of this work is to characterize dosimetrically a clinical intraoperative electron beam accelerator, Mobetron (IntraOp Medical, Inc.) in clinical use in our Hospital. Once this first step is completed our purpose is to evaluate shielding requirements for such a device by preparing adequate phase space files. Methods: It is known that electron beam simulation parameters required for state-of-the-art Monte Carlo codes to obtain a good match with measured data, like the mean energy or the FWHM, may not be code-independent due to the different set of process simulated and formalisms involved. Then, to cross-check our results against any issue in the simulation we have compared experimental data (PDD and profiles for electrons in the range 4 to 12 MeV) with simulations performed independently using both Penelope2011 and Geant4 codes. To do so, the geometry and materials of the head of the accelerator have been fully characterized following information provided by the manufacturer. Results: Both simulations agree with experimental data within experimental uncertainties (±1 mm displacement), although small variations (less than 10%) in the mean energy and FWHM are required to match measured values depending on the code used. Conclusion: Independent Monte Carlo simulations were used to obtain an excellent match to measured electron dose distributions. This opens the road to use such data for evaluating shielding requirements which is the main objective of this project.

  9. Dosimetric effect on pediatric conformal treatment plans using dynamic jaw with Tomotherapy HDA

    SciTech Connect

    Han, Eun Young; Kim, Dong-Wook; Zhang, Xin; Penagaricano, Jose; Liang, Xiaoying; Hardee, Matthew; Morrill, Steve; Ratanatharathorn, Vaneerat

    2015-10-01

    It is important to minimize the radiation dose delivered to healthy tissues in pediatric cancer treatment because of the risk of secondary malignancies. Tomotherapy HDA provides a dynamic jaw (DJ) delivery mode that creates a sharper penumbra at the craniocaudal ends of a target in addition to a fixed jaw (FJ) delivery mode. The purpose of this study was to evaluate its dosimetric effect on the pediatric cancer cases. We included 6 pediatric cases in this study. The dose profiles and plan statistics—target dose conformity, uniformity, organ-at-risk (OAR) mean dose, beam-on time, and integral dose—were compared for each case. Consequently, the target dose coverage and uniformity were similar for different jaw settings. The OAR dose sparing depended on its relative location to the target and disease sites. For example, in the head and neck cancer cases, the brain stem dose using DJ 2.5 was reduced by more than two-fold (2.4 Gy vs. 6.3 Gy) than that obtained with FJ 2.5. The integral dose with DJ 2.5 decreased by more than 9% compared with that with FJ 2.5. Thus, using dynamic jaw in pediatric cases could be critical to reduce a probability of a secondary malignancy.

  10. A comparison of VMAT dosimetric verifications between fixed and rotating gantry positions

    NASA Astrophysics Data System (ADS)

    Zhu, Jinhan; Chen, Lixin; Jin, Guanghua; Luo, Guangwen; Cao, Wufei; Liu, Xiaowei

    2013-03-01

    This study comparatively analysed dose distributions between the fixed and rotating gantry positions of volumetric-modulated arc therapy (VMAT) plans measured using different dosimetric techniques with the intent to provide pre-treatment quality assurance (QA). A total of 12 VMAT plans for the treatment of anatomical sites of various complexities were chosen. An ion chamber was used to measure the absolute central point doses, while EPID, Seven29, Matrixx and Delta4 were used to measure the dose distributions. With the exception of Delta4, all detectors were used in one of two different settings: the gantry was either fixed at 0°, or the gantry was rotating. The results were analysed using the γ-evaluation method. Regarding absolute central point doses, the ion chamber results were within 3% of the treatment planning system (TPS) calculated results. For the dose distributions measured by detectors and calculated by TPS, the γ pass rates, with 3% maximum dose and 3 mm γ criteria, were above 96% when the gantry was fixed at 0°. When the gantry was rotating, the pass rates decreased slightly but were still above 90%. The results obtained from the comparison between the measured and calculated doses demonstrated the reliability of four detectors associated with VMAT. However, the treatment delivery and detector response may impact the results when the gantry is rotating.

  11. Dosimetric study of mandible examinations performed with three cone-beam computed tomography scanners.

    PubMed

    Khoury, Helen J; Andrade, Marcos E; Araujo, Max Well; Brasileiro, Izabela V; Kramer, Richard; Huda, Amir

    2015-07-01

    The objective of this work was to evaluate the air kerma-area product (PKA) and the skin absorbed dose in the region of the eyes, salivary glands and thyroid of the patient from mandible examinations performed with three cone-beam computed tomography (CBCT) scanners, i.e. i-CAT classic, Gendex CB-500 and PreXion 3D. For the dosimetric evaluation, an anthropomorphic head phantom (model RS-250) was used to simulate an adult patient. The CBCT examinations were performed using standard and high-resolution protocols for mandible acquisitions for adult patients. During the phantom's exposure, the PKA was measured using an ionising chamber and the absorbed doses to the skin in the region of the eyes, thyroid and salivary glands were estimated using thermoluminescence dosemeters (TLDs) positioned on the phantom's surface. The PKA values estimated with the CBCT scanners varied from 26 to 138 µGy m(2). Skin absorbed doses in the region of the eyes varied from 0.07 to 0.34 mGy; at the parotid glands, from 1.31 to 5.93 mGy; at the submandibular glands, from 1.41 to 6.86 mGy; and at the thyroid, from 0.18 to 2.45 mGy. PKA and absorbed doses showed the highest values for the PreXion 3D scanner due to the use of the continuous exposure mode and a high current-time product.

  12. Helical Tomotherapy in Children and Adolescents: Dosimetric Comparisons, Opportunities and Issues

    PubMed Central

    Mascarin, Maurizio; Giugliano, Francesca Maria; Coassin, Elisa; Drigo, Annalisa; Chiovati, Paola; Dassie, Andrea; Franchin, Giovanni; Minatel, Emilio; Trovò, Mauro Gaetano

    2011-01-01

    Helical Tomotherapy (HT) is a highly conformal image-guided radiation technique, introduced into clinical routine in 2006 at the Centro di Riferimento Oncologico Aviano (Italy). With this new technology, intensity-modulated radiotherapy (IMRT) is delivered using a helicoidal method. Here we present our dosimetric experiences using HT in 100 children, adolescents and young adults treated from May 2006 to February 2011. The median age of the patients was 13 years (range 1–24). The most common treated site was the central nervous system (50; of these, 24 were craniospinal irradiations), followed by thorax (22), head and neck (10), abdomen and pelvis (11), and limbs (7). The use of HT was calculated in accordance to the target dose conformation, the target size and shape, the dose to critical organs adjacent to the target, simultaneous treatment of multiple targets, and re-irradiation. HT has demonstrated to improve target volume dose homogeneity and the sparing of critical structures, when compared to 3D Linac-based radiotherapy (RT). In standard cases this technique represented a comparable alternative to IMRT delivered with conventional linear accelerator. In certain cases (e.g., craniospinal and pleural treatments) only HT generated adequate treatment plans with good target volume coverage. However, the gain in target conformality should be balanced with the spread of low-doses to distant areas. This remains an open issue for the potential risk of secondary malignancies (SMNs) and longer follow-up is mandatory. PMID:24213120

  13. [131I]-metaiodobenzylguanidine in the treatment of metastatic neuroblastoma. Clinical, pharmacological and dosimetric aspects.

    PubMed

    Klingebiel, T; Treuner, J; Ehninger, G; Keller, K D; Dopfer, R; Feine, U; Niethammer, D

    1989-01-01

    Ten children with stage III or IV neuroblastoma that had either relapsed or was refractory were treated with [131I]-metaiodobenzylguanidine (MIBG) from 1984 to 1986. The total dose ranged from 4,365 to 21,900 MBq and was given in one to five courses. Two patients achieved a complete remission (CR), two, a partial remission (PR), and three, an arrest of the disease. Pharmacological studies showed that 93% of detectable radioactivity was attributable to MIBG at the beginning of the infusion. However, by the end of the infusion this had decreased to 88%. The terminal half-life of MIBG was 37.0 h, whereas that of non-MIBG-bound iodine was 71.6 h. Therefore, the radioactivity-time product of non-MIBG-bound 131I was much higher than that of MIBG. Dosimetric studies showed a mean level of absorbed radiation for the total body of 160 microGy/MBq, a liver irradiation of 540 microGy/MBq and a mean tumour radiation of 10,500 microGy/MBq.

  14. Evaluation of the deformation and corresponding dosimetric implications in prostate cancer treatment

    PubMed Central

    Glide-Hurst, Carri; Nurushev, Teamour; Xing, Lei; Kim, Jinkoo; Zhong, Hualiang; Liu, Dezhi; Liu, Manju; Burmeister, Jay; Movsas, Benjamin; Chetty, Indrin J

    2013-01-01

    The cone-beam computed tomography (CBCT) imaging modality is an integral component of image-guided adaptive radiation therapy (IGART), which uses patient-specific dynamic/temporal information for potential treatment plan modification. In this study, an offline process for the integral component IGART framework has been implemented that consists of deformable image registration (DIR) and its validation, dose reconstruction, dose accumulation and dose verification. This study compares the differences between planned and estimated delivered doses under an IGART framework of five patients undergoing prostate cancer radiation therapy. The dose calculation accuracy on CBCT was verified by measurements made in a Rando pelvic phantom. The accuracy of DIR on patient image sets was evaluated in three ways: landmark matching with fiducial markers, visual image evaluation and unbalanced energy (UE); UE has been previously demonstrated to be a feasible method for the validation of DIR accuracy at a voxel level. The dose calculated on each CBCT image set was reconstructed and accumulated over all fractions to reflect the ‘actual dose’ delivered to the patient. The deformably accumulated (delivered) plans were then compared to the original (static) plans to evaluate tumor and normal tissue dose discrepancies. The results support the utility of adaptive planning, which can be used to fully elucidate the dosimetric impact based on the simulated delivered dose to achieve the desired tumor control and normal tissue sparing, which may be of particular importance in the context of hypofractionated radiotherapy regimens. PMID:22863976

  15. Evaluation of the deformation and corresponding dosimetric implications in prostate cancer treatment

    NASA Astrophysics Data System (ADS)

    Wen, Ning; Glide-Hurst, Carri; Nurushev, Teamour; Xing, Lei; Kim, Jinkoo; Zhong, Hualiang; Liu, Dezhi; Liu, Manju; Burmeister, Jay; Movsas, Benjamin; Chetty, Indrin J.

    2012-09-01

    The cone-beam computed tomography (CBCT) imaging modality is an integral component of image-guided adaptive radiation therapy (IGART), which uses patient-specific dynamic/temporal information for potential treatment plan modification. In this study, an offline process for the integral component IGART framework has been implemented that consists of deformable image registration (DIR) and its validation, dose reconstruction, dose accumulation and dose verification. This study compares the differences between planned and estimated delivered doses under an IGART framework of five patients undergoing prostate cancer radiation therapy. The dose calculation accuracy on CBCT was verified by measurements made in a Rando pelvic phantom. The accuracy of DIR on patient image sets was evaluated in three ways: landmark matching with fiducial markers, visual image evaluation and unbalanced energy (UE); UE has been previously demonstrated to be a feasible method for the validation of DIR accuracy at a voxel level. The dose calculated on each CBCT image set was reconstructed and accumulated over all fractions to reflect the ‘actual dose’ delivered to the patient. The deformably accumulated (delivered) plans were then compared to the original (static) plans to evaluate tumor and normal tissue dose discrepancies. The results support the utility of adaptive planning, which can be used to fully elucidate the dosimetric impact based on the simulated delivered dose to achieve the desired tumor control and normal tissue sparing, which may be of particular importance in the context of hypofractionated radiotherapy regimens.

  16. Dosimetric shield evaluation with tungsten sheet in 4, 6, and 9MeV electron beams.

    PubMed

    Fujimoto, Takahiro; Monzen, Hajime; Nakata, Manabu; Okada, Takashi; Yano, Shinsuke; Takakura, Toru; Kuwahara, Junichi; Sasaki, Makoto; Higashimura, Kyoji; Hiraoka, Masahiro

    2014-11-01

    In electron radiotherapy, shielding material is required to attenuate beam and scatter. A newly introduced shielding material, tungsten functional paper (TFP), has been anticipated to become a very useful device that is lead-free, light, flexible, and easily processed, containing very fine tungsten powder at as much as 80% by weight. The purpose of this study was to investigate the dosimetric changes due to TFP shielding for electron beams. TFP (thickness 0-15mm) was placed on water or a water-equivalent phantom. Percentage depth ionization and transmission were measured for 4, 6, and 9MeV electron beams. Off-center ratio was also measured using film dosimetry at depth of dose maximum under similar conditions. Then, beam profiles and transmission with two shielding materials, TFP and lead, were evaluated. Reductions of 95% by using TFP at 0.5cm depth occurred at 4, 9, and 15mm with 4, 6, and 9MeV electron beams, respectively. It is found that the dose tend to increase at the field edge shaped with TFP, which might be influenced by the thickness. TFP has several unique features and is very promising as a useful tool for radiation protection for electron beams, among others. PMID:24953537

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    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.

  18. Cellular uptake of {sup 212}BiOCl by Ehrlich ascites cells: A dosimetric analysis

    SciTech Connect

    Roeske, J.C.; Whitlock, J.L.; Harper, P.V.; Rotmensch, J.; Stinchcomb, T.G.; Schwartz, J.L.; Hines, J.J.

    1999-01-01

    Bi-212 is an alpha-emitting radionuclide being investigated as a therapeutic agent in the intraperitoneal treatment of micrometastatic ovarian carcinoma. In evaluating a new therapeutic modality, cell-survival studies are often used as a means of quantifying the biological effects of radiation. In this analysis, Ehrlich ascites cells were irradiated under conditions similar to therapy in various concentrations of Bi-212. Immediately following irradiation, a cell survival assay was performed in which cells were plated and colonies were counted after 10--14 days. Both a macrodosimetric and a microdosimetric approach were used in analyzing these data. These models used as input the fraction of activity within the cell and in solution, the distribution of cell sizes, and the variation of LET along individual alpha-particle tracks. The results indicate that the energy deposited within the nucleus varies significantly among individual cells. There is a small fraction of cell nuclei which receive no hits, while the remaining cells receive energy depositions which can differ significantly from the mean value. These dosimetric parameters are correlated with measured cell survival and will be a useful predictor of outcome for therapeutic doses.

  19. Dosimetric benefit of adaptive re-planning in pancreatic cancer stereotactic body radiotherapy.

    PubMed

    Li, Yongbao; Hoisak, Jeremy D P; Li, Nan; Jiang, Carrie; Tian, Zhen; Gautier, Quentin; Zarepisheh, Masoud; Wu, Zhaoxia; Liu, Yaqiang; Jia, Xun; Hattangadi-Gluth, Jona; Mell, Loren K; Jiang, Steve; Murphy, James D

    2015-01-01

    Stereotactic body radiotherapy (SBRT) shows promise in unresectable pancreatic cancer, though this treatment modality has high rates of normal tissue toxicity. This study explores the dosimetric utility of daily adaptive re-planning with pancreas SBRT. We used a previously developed supercomputing online re-planning environment (SCORE) to re-plan 10 patients with pancreas SBRT. Tumor and normal tissue contours were deformed from treatment planning computed tomographies (CTs) and transferred to daily cone-beam CT (CBCT) scans before re-optimizing each daily treatment plan. We compared the intended radiation dose, the actual radiation dose, and the optimized radiation dose for the pancreas tumor planning target volume (PTV) and the duodenum. Treatment re-optimization improved coverage of the PTV and reduced dose to the duodenum. Within the PTV, the actual hot spot (volume receiving 110% of the prescription dose) decreased from 4.5% to 0.5% after daily adaptive re-planning. Within the duodenum, the volume receiving the prescription dose decreased from 0.9% to 0.3% after re-planning. It is noteworthy that variation in the amount of air within a patient׳s stomach substantially changed dose to the PTV. Adaptive re-planning with pancreas SBRT has the ability to improve dose to the tumor and decrease dose to the nearby duodenum, thereby reducing the risk of toxicity. PMID:26002122

  20. Beam’s-eye-view dosimetrics (BEVD) guided rotational station parameter optimized radiation therapy (SPORT) planning based on reweighted total-variation minimization

    NASA Astrophysics Data System (ADS)

    Kim, Hojin; Li, Ruijiang; Lee, Rena; Xing, Lei

    2015-03-01

    Conventional VMAT optimizes aperture shapes and weights at uniformly sampled stations, which is a generalization of the concept of a control point. Recently, rotational station parameter optimized radiation therapy (SPORT) has been proposed to improve the plan quality by inserting beams to the regions that demand additional intensity modulations, thus formulating non-uniform beam sampling. This work presents a new rotational SPORT planning strategy based on reweighted total-variation (TV) minimization (min.), using beam’s-eye-view dosimetrics (BEVD) guided beam selection. The convex programming based reweighted TV min. assures the simplified fluence-map, which facilitates single-aperture selection at each station for single-arc delivery. For the rotational arc treatment planning and non-uniform beam angle setting, the mathematical model needs to be modified by additional penalty term describing the fluence-map similarity and by determination of appropriate angular weighting factors. The proposed algorithm with additional penalty term is capable of achieving more efficient and deliverable plans adaptive to the conventional VMAT and SPORT planning schemes by reducing the dose delivery time about 5 to 10 s in three clinical cases (one prostate and two head-and-neck (HN) cases with a single and multiple targets). The BEVD guided beam selection provides effective and yet easy calculating methodology to select angles for denser, non-uniform angular sampling in SPORT planning. Our BEVD guided SPORT treatment schemes improve the dose sparing to femoral heads in the prostate and brainstem, parotid glands and oral cavity in the two HN cases, where the mean dose reduction of those organs ranges from 0.5 to 2.5 Gy. Also, it increases the conformation number assessing the dose conformity to the target from 0.84, 0.75 and 0.74 to 0.86, 0.79 and 0.80 in the prostate and two HN cases, while preserving the delivery efficiency, relative to conventional single-arc VMAT plans.

  1. Mapping the Heart

    ERIC Educational Resources Information Center

    Hulse, Grace

    2012-01-01

    In this article, the author describes how her fourth graders made ceramic heart maps. The impetus for this project came from reading "My Map Book" by Sara Fanelli. This book is a collection of quirky, hand-drawn and collaged maps that diagram a child's world. There are maps of her stomach, her day, her family, and her heart, among others. The…

  2. Dosimetric characterization of the M-15 high-dose-rate Iridium-192 brachytherapy source using the AAPM and ESTRO formalism.

    PubMed

    Ho Than, Minh-Tri; Munro Iii, John J; Medich, David C

    2015-05-08

    The Source Production & Equipment Co. (SPEC) model M-15 is a new Iridium-192 brachytherapy source model intended for use as a temporary high-dose-rate (HDR) brachytherapy source for the Nucletron microSelectron Classic afterloading system. The purpose of this study is to characterize this HDR source for clinical application by obtaining a complete set of Monte Carlo calculated dosimetric parameters for the M-15, as recommended by AAPM and ESTRO, for isotopes with average energies greater than 50 keV. This was accomplished by using the MCNP6 Monte Carlo code to simulate the resulting source dosimetry at various points within a pseudoinfinite water phantom. These dosimetric values next were converted into the AAPM and ESTRO dosimetry parameters and the respective statistical uncertainty in each parameter also calculated and presented. The M-15 source was modeled in an MCNP6 Monte Carlo environment using the physical source specifications provided by the manufacturer. Iridium-192 photons were uniformly generated inside the iridium core of the model M-15 with photon and secondary electron transport replicated using photoatomic cross-sectional tables supplied with MCNP6. Simulations were performed for both water and air/vacuum computer models with a total of 4 × 109 sources photon history for each simulation and the in-air photon spectrum filtered to remove low-energy photons belowδ = 10 keV. Dosimetric data, including D·(r,θ), gL(r), F(r,θ), φan(r), and φ-an, and their statistical uncertainty were calculated from the output of an MCNP model consisting of an M-15 source placed at the center of a spherical water phantom of 100 cm diameter. The air kerma strength in free space, SK, and dose rate constant, Λ, also was computed from a MCNP model with M-15 Iridium-192 source, was centered at the origin of an evacuated phantom in which a critical volume containing air at STP was added 100 cm from the source center. The reference dose rate, D·(r0,θ0) ≡ D· (1cm

  3. National Atlas maps

    USGS Publications Warehouse

    ,

    1991-01-01

    The National Atlas of the United States of America was published by the U.S. Geological Survey in 1970. Its 765 maps and charts are on 335 14- by 19-inch pages. Many of the maps span facing pages. It's worth a quick trip to the library just to leaf through all 335 pages of this book. Rapid scanning of its thematic maps yields rich insights to the geography of issues of continuing national interest. On most maps, the geographic patterns are still valid, though the data are not current. The atlas is out of print, but many of its maps can be purchased separately. Maps that span facing pages in the atlas are printed on one sheet. The maps dated after 1970 are either revisions of original atlas maps, or new maps published in atlas format. The titles of the separate maps are listed here.

  4. Dosimetric characteristics of the novel 2D ionization chamber array OCTAVIUS Detector 1500

    SciTech Connect

    Stelljes, T. S. Looe, H. K.; Chofor, N.; Poppe, B.; Harmeyer, A.; Reuter, J.; Harder, D.

    2015-04-15

    Purpose: The dosimetric properties of the OCTAVIUS Detector 1500 (OD1500) ionization chamber array (PTW-Freiburg, Freiburg, Germany) have been investigated. A comparative study was carried out with the OCTAVIUS Detector 729 and OCTAVIUS Detector 1000 SRS arrays. Methods: The OD1500 array is an air vented ionization chamber array with 1405 detectors in a 27 × 27 cm{sup 2} measurement area arranged in a checkerboard pattern with a chamber-to-chamber distance of 10 mm in each row. A sampling step width of 5 mm can be achieved by merging two measurements shifted by 5 mm, thus fulfilling the Nyquist theorem for intensity modulated dose distributions. The stability, linearity, and dose per pulse dependence were investigated using a Semiflex 31013 chamber (PTW-Freiburg, Freiburg, Germany) as a reference detector. The effective depth of measurement was determined by measuring TPR curves with the array and a Roos chamber type 31004 (PTW-Freiburg, Freiburg, Germany). Comparative output factor measurements were performed with the array, the Semiflex 31010 ionization chamber and the Diode 60012 (both PTW-Freiburg, Freiburg, Germany). The energy dependence of the OD1500 was measured by comparing the array’s readings to those of a Semiflex 31010 ionization chamber for varying mean photon energies at the depth of measurement, applying to the Semiflex chamber readings the correction factor k{sub NR} for nonreference conditions. The Gaussian lateral dose response function of a single array detector was determined by searching the convolution kernel suitable to convert the slit beam profiles measured with a Diode 60012 into those measured with the array’s central chamber. An intensity modulated dose distribution measured with the array was verified by comparing a OD1500 measurement to TPS calculations and film measurements. Results: The stability and interchamber sensitivity variation of the OD1500 array were within ±0.2% and ±0.58%, respectively. Dose linearity was within 1

  5. Biokinetic and dosimetric modelling in the estimation of radiation risks from internal emitters.

    PubMed

    Harrison, John

    2009-06-01

    The International Commission on Radiological Protection (ICRP) has developed biokinetic and dosimetric models that enable the calculation of organ and tissue doses for a wide range of radionuclides. These are used to calculate equivalent and effective dose coefficients (dose in Sv Bq(-1) intake), considering occupational and environmental exposures. Dose coefficients have also been given for a range of radiopharmaceuticals used in diagnostic medicine. Using equivalent and effective dose, exposures from external sources and from different radionuclides can be summed for comparison with dose limits, constraints and reference levels that relate to risks from whole-body radiation exposure. Risk estimates are derived largely from follow-up studies of the survivors of the atomic bombings at Hiroshima and Nagasaki in 1945. New dose coefficients will be required following the publication in 2007 of new ICRP recommendations. ICRP biokinetic and dosimetric models are subject to continuing review and improvement, although it is arguable that the degree of sophistication of some of the most recent models is greater than required for the calculation of effective dose to a reference person for the purposes of regulatory control. However, the models are also used in the calculation of best estimates of doses and risks to individuals, in epidemiological studies and to determine probability of cancer causation. Models are then adjusted to best fit the characteristics of the individuals and population under consideration. For example, doses resulting from massive discharges of strontium-90 and other radionuclides to the Techa River from the Russian Mayak plutonium plant in the early years of its operation are being estimated using models adapted to take account of measurements on local residents and other population-specific data. Best estimates of doses to haemopoietic bone marrow, in utero and postnatally, are being used in epidemiological studies of radiation-induced leukaemia

  6. Dosimetric impact of intrafraction motion for compensator-based proton therapy of lung cancer

    NASA Astrophysics Data System (ADS)

    Zhao, Li; Sandison, George A.; Farr, Jonathan B.; Chien Hsi, Wen; Li, X. Allen

    2008-06-01

    Compensator-based proton therapy of lung cancer using an un-gated treatment while allowing the patient to breathe freely requires a compensator design that ensures tumor coverage throughout respiration. Our investigation had two purposes: one is to investigate the dosimetric impact when a composite compensator correction is applied, or is not, and the other one is to evaluate the significance of using different respiratory phases as the reference computed tomography (CT) for treatment planning dose calculations. A 4D-CT-based phantom study and a real patient treatment planning study were performed. A 3D MIP dataset generated over all phases of the acquired 4D-CT scans was adopted to design the field-specific composite aperture and compensator. In the phantom study, the MIP-based compensator design plan named plan D was compared to the other three plans, in which average intensity projection (AIP) images in conjunction with the composite target volume contour copied from the MIP images were used. Relative electron densities within the target envelope were assigned either to original values from the AIP image dataset (plan A) or to predetermined values, 0.8 (plan B) and 0.9 (plan C). In the patient study, the dosimetric impact of a compensator design based on the MIP images (plan ITVMIP) was compared to designs based on end-of-inhale (EOI) (plan ITVEOI) and middle-of-exhale (MOE) CT images (plan ITVMOE). The dose distributions were recalculated for each phase. Throughout the ten phases, it shows that DGTVmin changed slightly from 86% to 89% (SD = 0.9%) of prescribed dose (PD) in the MIP plan, while varying greatly from 10% to 79% (SD = 26.7%) in plan A, 17% to 73% (SD = 22.5%) in plan B and 53% to 73% (SD = 6.8%) in plan C. The same trend was observed for DGTVmean and V95 with less amplitude. In the MIP-based plan ITVMIP, DGTVmean was almost identically equal to 95% in each phase (SD = 0.5%). The patient study verified that the MIP approach increased the minimum

  7. Dosimetric impact of intrafraction motion for compensator-based proton therapy of lung cancer.

    PubMed

    Zhao, Li; Sandison, George A; Farr, Jonathan B; Hsi, Wen Chien; Li, X Allen

    2008-06-21

    Compensator-based proton therapy of lung cancer using an un-gated treatment while allowing the patient to breathe freely requires a compensator design that ensures tumor coverage throughout respiration. Our investigation had two purposes: one is to investigate the dosimetric impact when a composite compensator correction is applied, or is not, and the other one is to evaluate the significance of using different respiratory phases as the reference computed tomography (CT) for treatment planning dose calculations. A 4D-CT-based phantom study and a real patient treatment planning study were performed. A 3D MIP dataset generated over all phases of the acquired 4D-CT scans was adopted to design the field-specific composite aperture and compensator. In the phantom study, the MIP-based compensator design plan named plan D was compared to the other three plans, in which average intensity projection (AIP) images in conjunction with the composite target volume contour copied from the MIP images were used. Relative electron densities within the target envelope were assigned either to original values from the AIP image dataset (plan A) or to predetermined values, 0.8 (plan B) and 0.9 (plan C). In the patient study, the dosimetric impact of a compensator design based on the MIP images (plan ITV(MIP)) was compared to designs based on end-of-inhale (EOI) (plan ITV(EOI)) and middle-of-exhale (MOE) CT images (plan ITV(MOE)). The dose distributions were recalculated for each phase. Throughout the ten phases, it shows that D(GTV)(min) changed slightly from 86% to 89% (SD = 0.9%) of prescribed dose (PD) in the MIP plan, while varying greatly from 10% to 79% (SD = 26.7%) in plan A, 17% to 73% (SD = 22.5%) in plan B and 53% to 73% (SD = 6.8%) in plan C. The same trend was observed for D(GTV)(mean) and V95 with less amplitude. In the MIP-based plan ITV(MIP), D(GTV)(mean) was almost identically equal to 95% in each phase (SD = 0.5%). The patient study verified that the MIP approach

  8. Dosimetric comparison of Acuros XB, AAA, and XVMC in stereotactic body radiotherapy for lung cancer

    SciTech Connect

    Tsuruta, Yusuke; Nakata, Manabu; Higashimura, Kyoji; Nakamura, Mitsuhiro Matsuo, Yukinori; Monzen, Hajime; Mizowaki, Takashi; Hiraoka, Masahiro

    2014-08-15

    Purpose: To compare the dosimetric performance of Acuros XB (AXB), anisotropic analytical algorithm (AAA), and x-ray voxel Monte Carlo (XVMC) in heterogeneous phantoms and lung stereotactic body radiotherapy (SBRT) plans. Methods: Water- and lung-equivalent phantoms were combined to evaluate the percentage depth dose and dose profile. The radiation treatment machine Novalis (BrainLab AG, Feldkirchen, Germany) with an x-ray beam energy of 6 MV was used to calculate the doses in the composite phantom at a source-to-surface distance of 100 cm with a gantry angle of 0°. Subsequently, the clinical lung SBRT plans for the 26 consecutive patients were transferred from the iPlan (ver. 4.1; BrainLab AG) to the Eclipse treatment planning systems (ver. 11.0.3; Varian Medical Systems, Palo Alto, CA). The doses were then recalculated with AXB and AAA while maintaining the XVMC-calculated monitor units and beam arrangement. Then the dose-volumetric data obtained using the three different radiation dose calculation algorithms were compared. Results: The results from AXB and XVMC agreed with measurements within ±3.0% for the lung-equivalent phantom with a 6 × 6 cm{sup 2} field size, whereas AAA values were higher than measurements in the heterogeneous zone and near the boundary, with the greatest difference being 4.1%. AXB and XVMC agreed well with measurements in terms of the profile shape at the boundary of the heterogeneous zone. For the lung SBRT plans, AXB yielded lower values than XVMC in terms of the maximum doses of ITV and PTV; however, the differences were within ±3.0%. In addition to the dose-volumetric data, the dose distribution analysis showed that AXB yielded dose distribution calculations that were closer to those with XVMC than did AAA. Means ± standard deviation of the computation time was 221.6 ± 53.1 s (range, 124–358 s), 66.1 ± 16.0 s (range, 42–94 s), and 6.7 ± 1.1 s (range, 5–9 s) for XVMC, AXB, and AAA, respectively. Conclusions: In the

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

    NASA Astrophysics Data System (ADS)

    Gökçe, M.; Uslu, D. Koçyiǧit; Ertunç, C.; Karalı, T.

    2016-03-01

    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 %3 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.

  10. Dosimetric evaluation of MRI-based treatment planning for prostate cancer

    NASA Astrophysics Data System (ADS)

    Chen, L.; Price, R. A., Jr.; Nguyen, T.-B.; Wang, L.; Li, J. S.; Qin, L.; Ding, M.; Palacio, E.; Ma, C.-M.; Pollack, A.

    2004-11-01

    The purpose of this study is to evaluate the dosimetric accuracy of MRI-based treatment planning for prostate cancer using a commercial radiotherapy treatment planning system. Three-dimensional conformal plans for 15 prostate patients were generated using the AcQPlan system. For each patient, dose distributions were calculated using patient CT data with and without heterogeneity correction, and using patient MRI data without heterogeneity correction. MR images were post-processed using the gradient distortion correction (GDC) software. The distortion corrected MR images were fused to the corresponding CT for each patient for target and structure delineation. The femoral heads were delineated based on CT. Other anatomic structures relevant to the treatment (i.e., prostate, seminal vesicles, lymph notes, rectum and bladder) were delineated based on MRI. The external contours were drawn separately on CT and MRI. The same internal contours were used in the dose calculation using CT- and MRI-based geometries by directly transferring them between MRI and CT as needed. Treatment plans were evaluated based on maximum dose, isodose distributions and dose-volume histograms. The results confirm previous investigations that there is no clinically significant dose difference between CT-based prostate plans with and without heterogeneity correction. The difference in the target dose between CT- and MRI-based plans using homogeneous geometry was within 2.5%. Our results suggest that MRI-based treatment planning is suitable for radiotherapy of prostate cancer. The materials in this paper have been presented in part at the San Diego 2003 AAPM.

  11. Dosimetric analysis and comparison of IMRT and HDR brachytherapy in treatment of localized prostate cancer.

    PubMed

    Murali, V; Kurup, P G G; Mahadev, P; Mahalakshmi, S

    2010-04-01

    Radical radiotherapy is one of the options for the management of prostate cancer. In external beam therapy, 3D conformal radiotherapy (3DCRT) and intensity modulated radiotherapy (IMRT) are the options for delivery of increased radiation dose, as vital organs are very close to the prostate and a higher dose to these structures leads to an increased toxicity. In brachytherapy, low dose rate brachytherapy with permanent implant of radioactive seeds and high dose rate brachytherapy (HDR) with remote after loaders are available. A dosimetric analysis has been made on IMRT and HDR brachytherapy plans. Ten cases from each IMRT and HDR brachytherapy have been taken for the study. The analysis includes comparison of conformity and homogeneity indices, D100, D95, D90, D80, D50, D10 and D5 of the target. For the organs at risk (OAR), namely rectum and bladder, V100, V90 and V50 are compared. In HDR brachytherapy, the doses to 1 cc and 0.1 cc of urethra have also been studied. Since a very high dose surrounds the source, the 300% dose volumes in the target and within the catheters are also studied in two plans, to estimate the actual volume of target receiving dose over 300%. This study shows that the prescribed dose covers 93 and 92% of the target volume in IMRT and HDR brachytherapy respectively. HDR brachytherapy delivers a much lesser dose to OAR, compared to the IMRT. For rectum, the V50 in IMRT is 34.0cc whilst it is 7.5cc in HDR brachytherapy. With the graphic optimization tool in HDR brachytherapy planning, the dose to urethra could be kept within 120% of the target dose. Hence it is concluded that HDR brachytherapy may be the choice of treatment for cancer of prostate in the early stage.

  12. Dosimetric evaluation of sucrose and granulated cane sugar in the therapeutic dose range

    SciTech Connect

    Davidson, Melanie T. M.; Jordan, Kevin J.

    2009-04-15

    Granulated cane sugar has been used as a dosimetric material to report dose in high dose accidental irradiations. The purpose of this study was to assess whether clinical dosimetry is also plausible with such a commonly available material. The behavior of cane sugar was explored with respect to therapeutically relevant radiation quantities (dose, dose rate) and qualities (energy, radiation type) as well as under different temperature conditions. The stability of the signal postirradiation was also measured. Absorbed dose was measured by spectrophotometric readout of a ferrous ammonium sulfate xylenol orange (FX)-sugar solution in 10 cm path length cells. A visible color change was produced as a function of dose when the irradiated sugar samples were dissolved in FX solution (10% dilution by mass). A comparison of the optical absorbance spectra and dose response of cane sugar with analytical grade sucrose was done to establish a benchmark standard from which subsequent dosimetry measurements can be validated. The response of the sugar dosimeter read at 590 nm was found to be linear over the dose range of 100-2000 cGy, independent of energy (6-18 MV) and of the average dose rate (100-500 cGy/min). The readout of sugar samples irradiated with mixed photon and electron fields was also shown to be independent of radiation type (photons and electrons). Sugar temperature (20-40 degree sign C) during irradiation did not affect dose estimates, making it a promising dosimeter for in vivo dosimetry, particularly in cases where the dosimeter must remain in contact with the patient for an extended period of time. Sugar can be used as an integrating dosimeter, since it exhibits no fractionation effects. Granulated cane sugar is cost effective, safe, soft tissue equivalent, and can be used under various experimental conditions, making it a suitable dosimeter for some radiotherapy applications.

  13. Dosimetric impact of number of treatment fields in uniform scanning proton therapy planning of lung cancer.

    PubMed

    Rana, Suresh; Simpson, Hilarie; Larson, Gary; Zheng, Yuanshui

    2014-10-01

    The main purpose of this study was to perform a treatment planning study for lung cancer comparing 2-field (2F) versus 3-field (3F) techniques in uniform scanning proton therapy (USPT). Ten clinically approved lung cancer treatment plans delivered using USPT at our proton center were included in this retrospective study. All 10 lung cases included 4D computed tomography (CT) simulation. The delineation of target volumes was done based on the maximum intensity projection (MIP) images. Both the 3F and 2F treatment plans were generated for the total dose of 74 cobalt-gray-equivalent (CGE) with a daily dose of 2 CGE. 3F plan was generated by adding an extra beam in the 2F plan. Various dosimetric parameters between 2F and 3F plans were evaluated. 3F plans produced better target coverage and conformality as well as lower mean dose to the lung, with absolute difference between 3F and 2F plans within 2%. In contrast, the addition of third beam led to increase of low-dose regions (V20 and V5) in the lung in 3F plans compared to the ones in 2F plans with absolute difference within 2%. Maximum dose to the spinal cord was lower in 2F plans. Mean dose to the heart and esophagus were comparable in both 3F and 2F plans. In conclusion, the 3F technique in USPT produced better target coverage and conformality, but increased the low-dose regions in the lung when compared to 2F technique.

  14. Strategies for reducing intra-fraction motion induced dosimetric effects in proton therapy

    NASA Astrophysics Data System (ADS)

    Zhao, Li

    Intra-fraction respiration motion during radiation delivery presents a major challenge to radiation therapy. There has been a growing effort to characterize and manage internal organ motion in radiation therapy, however very few studies focus on tackling this issue in proton therapy. Current practice for treating lung tumors in proton therapy is still to apply population-based margins to account for internal tumor motion, which can lead to target underdosage and normal tissue overdosage. This thesis explores the intra-fraction motion induced dosimetric effects from both computational treatment planning and experimental studies. Four-dimensional CT scans are used to analyze the patient-specific tumor motion characteristics. A feasible method to design the range compensator by using the maximum intensity projection (MIP) images is proposed. Results demonstrate that this MIP approach ensures adequate tumor coverage throughout the entire respiratory cycle whilst maintaining normal tissue dose under clinical constraints. Based on 4D-CT scans, dose convolution is used for assessing the accuracy of Gaussian probability density function for modeling the patient-specific respiratory motion on dose distribution. Non-negligible dose discrepancy is observed in comparisons of convolved dose distributions, and patient-specific respiration PDF is advocated. In addition, an experimental phantom study primarily focusing on the interplay effect between target motion and the scanning beam motion is implemented in two proton beam delivery systems: double scattering and uniform scanning. Measurement results suggest that dose blurring effect is dominant, and interplay effect is trivial in the uniform scanning system due to dose repainting.

  15. Dosimetric quality control of Eclipse treatment planning system using pelvic digital test object

    NASA Astrophysics Data System (ADS)

    Benhdech, Yassine; Beaumont, Stéphane; Guédon, Jeanpierre; Crespin, Sylvain

    2011-03-01

    Last year, we demonstrated the feasibility of a new method to perform dosimetric quality control of Treatment Planning Systems in radiotherapy, this method is based on Monte-Carlo simulations and uses anatomical Digital Test Objects (DTOs). The pelvic DTO was used in order to assess this new method on an ECLIPSE VARIAN Treatment Planning System. Large dose variations were observed particularly in air and bone equivalent material. In this current work, we discuss the results of the previous paper and provide an explanation for observed dose differences, the VARIAN Eclipse (Anisotropic Analytical) algorithm was investigated. Monte Carlo simulations (MC) were performed with a PENELOPE code version 2003. To increase efficiency of MC simulations, we have used our parallelized version based on the standard MPI (Message Passing Interface). The parallel code has been run on a 32- processor SGI cluster. The study was carried out using pelvic DTOs and was performed for low- and high-energy photon beams (6 and 18MV) on 2100CD VARIAN linear accelerator. A square field (10x10 cm2) was used. Assuming the MC data as reference, χ index analyze was carried out. For this study, a distance to agreement (DTA) was set to 7mm while the dose difference was set to 5% as recommended in the TRS-430 and TG-53 (on the beam axis in 3-D inhomogeneities). When using Monte Carlo PENELOPE, the absorbed dose is computed to the medium, however the TPS computes dose to water. We have used the method described by Siebers et al. based on Bragg-Gray cavity theory to convert MC simulated dose to medium to dose to water. Results show a strong consistency between ECLIPSE and MC calculations on the beam axis.

  16. Dosimetric verification of stereotactic radiosurgery/stereotactic radiotherapy dose distributions using Gafchromic EBT3

    SciTech Connect

    Cusumano, Davide; Fumagalli, Maria L.; Marchetti, Marcello; Fariselli, Laura; De Martin, Elena

    2015-10-01

    Aim of this study is to examine the feasibility of using the new Gafchromic EBT3 film in a high-dose stereotactic radiosurgery and radiotherapy quality assurance procedure. Owing to the reduced dimensions of the involved lesions, the feasibility of scanning plan verification films on the scanner plate area with the best uniformity rather than using a correction mask was evaluated. For this purpose, signal values dispersion and reproducibility of film scans were investigated. Uniformity was then quantified in the selected area and was found to be within 1.5% for doses up to 8 Gy. A high-dose threshold level for analyses using this procedure was established evaluating the sensitivity of the irradiated films. Sensitivity was found to be of the order of centiGray for doses up to 6.2 Gy and decreasing for higher doses. The obtained results were used to implement a procedure comparing dose distributions delivered with a CyberKnife system to planned ones. The procedure was validated through single beam irradiation on a Gafchromic film. The agreement between dose distributions was then evaluated for 13 patients (brain lesions, 5 Gy/die prescription isodose ~80%) using gamma analysis. Results obtained using Gamma test criteria of 5%/1 mm show a pass rate of 94.3%. Gamma frequency parameters calculation for EBT3 films showed to strongly depend on subtraction of unexposed film pixel values from irradiated ones. In the framework of the described dosimetric procedure, EBT3 films proved to be effective in the verification of high doses delivered to lesions with complex shapes and adjacent to organs at risk.

  17. In vivo real-time dosimetric verification in high dose rate prostate brachytherapy

    SciTech Connect

    Seymour, Erin L.; Downes, Simon J.; Fogarty, Gerald B.; Izard, Michael A.; Metcalfe, Peter

    2011-08-15

    Purpose: To evaluate the performance of a diode array in the routine verification of planned dose to points inside the rectum from prostate high dose rate (HDR) brachytherapy using a real-time planning system. Methods: A dosimetric study involving 28 patients was undertaken where measured doses received during treatment were compared to those calculated by the treatment planning system (TPS). After the ultrasound imaging required for treatment planning had been recorded, the ultrasound probe was replaced with a geometric replica that contained an 8 mm diameter cylindrical cavity in which a PTW diode array type 9112 was placed. The replica probe was then positioned inside the rectum with the individual diode positions determined using fluoroscopy. Dose was then recorded during the patients' treatment and compared to associated coordinates in the planning system. Results: Factors influencing diode response and experimental uncertainty were initially investigated to estimate the overall uncertainty involved in dose measurements, which was determined to be {+-}10%. Data was acquired for 28 patients' first fractions, 11 patients' second fractions, and 13 patients' third fractions with collection dependent upon circumstances. Deviations between the diode measurements and predicted values ranged from -42% to +35% with 71% of measurements experiencing less than a 10% deviation from the predicted values. If the {+-}10% measurement uncertainty was combined with a tolerated dose discrepancy of {+-}10% then over 95% of the diode results exhibited agreement with the calculated data to within {+-}20%. It must also be noted that when large dose discrepancies were apparent they did not necessarily occur for all five diodes in the one measurement. Conclusions: This technique provided a method that could be utilized to detect gross errors in dose delivery of a real-time prostate HDR plan. Limitations in the detection system used must be well understood if meaningful results are to

  18. SU-F-BRD-11: Prediction of Dosimetric Endpoints From Patient Geometry Using Neural Nets

    SciTech Connect

    O'Connell, D; Chow, P; Agazaryan, N; Jani, S; Low, D; Lamb, J

    2014-06-15

    Purpose: The previously-published overlap volume histogram (OVH) technique lends itself naturally to prediction of the dose received by a given volume of tissue (e.g. D90) in intensity-modulated radiotherapy (IMRT) treatment plans. Here we extend the OVH technique using artificial neural networks in order to predict the volume of tissue receiving a given dose (e.g. V90) in both prostate IMRT and conventional breast radiotherapy. Methods: Twenty-nine prostate treatment plans and forty-three breast treatment plans were analyzed. The spatial relationships between the prostate and rectum and between the breast and ipsilateral lung were characterized using OVHs. The OVH is a cumulative histogram representing the fractional volume of the risk organ overlapped by a series of isotropic expansions of the planning target volume (PTV). Seven cases were identified as outliers and replanned. OVH points were used as inputs to a one hidden layer feed forward artificial neural network with quality parameters of the corresponding plan, such as the rectum V50, as targets. A 3-fold cross-validation was used to estimate the prediction error. Results: The root mean square (RMS) error between the predicted rectum V50s and the planned values was 2.3, which was 35% of the standard deviation of V50 for the twenty-nine plans. The RMS error of prediction of V20 of the ipsilateral lung in breast cases was 3.9, which was 90% of the standard deviation of the V20 values in the breast plan database. Conclusion: This study demonstrates that artificial neural nets can be used to extend the OVH technique to predict dosimetric endpoints taking the form of a volume receiving a given dose, rather than the minimum dose received by a given volume. Prediction of ipsilateral lung dose in breast radiotherapy using the OVH technique remains a work in progress.

  19. 3D-Conformal Versus Intensity-Modulated Postoperative Radiotherapy of Vaginal Vault: A Dosimetric Comparison

    SciTech Connect

    Cilla, Savino; Macchia, Gabriella Digesu, Cinzia; Deodato, Francesco; Romanella, Michele; Ferrandina, Gabriella; Padula, Gilbert; Picardi, Vincenzo; Scambia, Giovanni; Morganti, Alessio Giuseppe

    2010-07-01

    We evaluated a step-and-shoot IMRT plan in the postoperative irradiation of the vaginal vault compared with equispaced beam arrangements (3-5) 3D-radiotherapy (RT) optimized plans. Twelve patients were included in this analysis. Four plans for each patient were compared in terms of dose-volume histograms, homogeneity index (HI), and conformity index (CI): (1) 3 equispaced beam arrangement 3D-RT; (2) 4 equispaced beam arrangement 3D-RT; (3) 5 equispaced beam arrangement 3D-RT; (4) step-and-shoot IMRT technique. CI showed a good discrimination between the four plans. The mean scores of CI were 0.58 (range: 0.38-0.67) for the 3F-CRT plan, 0.58 (range: 0.41-0.66) for 4F-CRT, 0.62 (range: 0.43-0.68) for 5F-CRT and 0.69 (range: 0.58-0.78) for the IMRT plan. A significant improvement of the conformity was reached by the IMRT plan (p < 0.001 for all comparisons). As expected, the increment of 3D-CRT fields was associated with an improvement of target dose conformity and homogeneity; on the contrary, in the IMRT plans, a better conformity was associated to a worse target dose homogeneity. A significant reduction in terms of D{sub mean}, V90%, V95%, V100% was recorded for rectal and bladder irradiation with the IMRT plan. Surprisingly, IMRT supplied a significant dose reduction also for rectum and bladder V30% and V50%. A significant dosimetric advantage of IMRT over 3D-RT in the adjuvant treatment of vaginal vault alone in terms of treatment conformity and rectum and bladder sparing is shown.

  20. Dosimetric effects of jaw tracking in step-and-shoot intensity-modulated radiation therapy.

    PubMed

    Joy, Sarah; Starkschall, George; Kry, Stephen; Salehpour, Mohammed; White, R Allen; Lin, Steven H; Balter, Peter

    2012-03-08

    The purpose of this work was to determine the dosimetric benefit to normal tissues by tracking the multi-leaf collimator (MLC) apertures with the photon jaws in step-and-shoot intensity-modulated radiation therapy (IMRT) on the Varian 2100 platform. Radiation treatment plans for ten thoracic, three pediatric, and three head and neck cancer patients were converted to plans with the jaws tracking each segment's MLC apertures, and compared to the original plans in a commercial radiation treatment planning system (TPS). The change in normal tissue dose was evaluated in the new plan by using the parameters V5, V10, and V20 (volumes receiving 5, 10 and 20 Gy, respectively) in the cumulative dose-volume histogram for the following structures: total lung minus gross target volume, heart, esophagus, spinal cord, liver, parotids, and brainstem. To validate the accuracy of our beam model, MLC transmission was measured and compared to that predicted by the TPS. The greatest changes between the original and new plans occurred at lower dose levels. In all patients, the reduction in V20 was never more than 6.3% and was typically less than 1%; the maximum reduction in V5 was 16.7% and was typically less than 3%. The variation in normal tissue dose reduction was not predictable, and we found no clear parameters that indicated which patients would benefit most from jaw tracking. Our TPS model of MLC transmission agreed with measurements with absolute transmission differences of less than 0.1% and, thus, uncertainties in the model did not contribute significantly to the uncertainty in the dose determination. We conclude that the amount of dose reduction achieved by collimating the jaws around each MLC aperture in step-and-shoot IMRT is probably not clinically significant.

  1. Dosimetric evaluation of two treatment planning systems for high dose rate brachytherapy applications.

    PubMed

    Shwetha, Bondel; Ravikumar, Manickam; Supe, Sanjay S; Sathiyan, Saminathan; Lokesh, Vishwanath; Keshava, Subbarao L

    2012-01-01

    Various treatment planning systems are used to design plans for the treatment of cervical cancer using high-dose-rate brachytherapy. The purpose of this study was to make a dosimetric comparison of the 2 treatment planning systems from Varian medical systems, namely ABACUS and BrachyVision. The dose distribution of Ir-192 source generated with a single dwell position was compared using ABACUS (version 3.1) and BrachyVision (version 6.5) planning systems. Ten patients with intracavitary applications were planned on both systems using orthogonal radiographs. Doses were calculated at the prescription points (point A, right and left) and reference points RU, LU, RM, LM, bladder, and rectum. For single dwell position, little difference was observed in the doses to points along the perpendicular bisector. The mean difference between ABACUS and BrachyVision for these points was 1.88%. The mean difference in the dose calculated toward the distal end of the cable by ABACUS and BrachyVision was 3.78%, whereas along the proximal end the difference was 19.82%. For the patient case there was approximately 2% difference between ABACUS and BrachyVision planning for dose to the prescription points. The dose difference for the reference points ranged from 0.4-1.5%. For bladder and rectum, the differences were 5.2% and 13.5%, respectively. The dose difference between the rectum points was statistically significant. There is considerable difference between the dose calculations performed by the 2 treatment planning systems. It is seen that these discrepancies are caused by the differences in the calculation methodology adopted by the 2 systems.

  2. Dosimetric and toxicity comparison between prone and supine position IMRT for endometrial cancer

    SciTech Connect

    Beriwal, Sushil . E-mail: beriwals@upmc.edu; Jain, Sheena K.; Heron, Dwight E.; De Andrade, Regiane S.; Lin, Chyonghiou J.; Kim, Hayeon

    2007-02-01

    Purpose: To determine the dosimetric and toxicity differences between prone and supine position intensity-modulate radiotherapy in endometrial cancer patients treated with adjuvant radiotherapy. Methods: Forty-seven consecutive endometrial cancer patients treated with adjuvant RT were analyzed. Of these, 21 were treated in prone position and 26 in the supine position. Dose-volume histograms for normal tissue structures and targets were compared between the two groups. Acute and chronic toxicity were also compared between the cohorts. Results: The percentage of volume receiving 10, 20, 30, 40, 45, and 50 Gy for small bowel was 89.5%, 69%, 33%, 12.2%, 5%, and 0% in the prone group and 87.5%, 62.7%, 26.4%, 8%, 4.3%, and 0% in the supine group, respectively. The difference was not statistically significant. The dose-volume histograms for bladder and rectum were also comparable, except for a slightly greater percentage of volume receiving 10 Gy (1.5%) and 20 Gy (5%) for the rectum in the prone group. Acute small bowel toxicities were Grade 1 in 7 patients and Grade 2 in 14 patients in the prone group vs. Grade 1 in 6 patients and Grade 2 in 19 patients in the supine group. Chronic toxicity was Grade 1 in 7 patients and Grade 3 in 1 patient in the prone group and Grade 1 in 5 patients in the supine group. Conclusion: These preliminary results suggest that no difference exists in the dose to the normal tissue and toxicity between prone and supine intensity-modulated radiotherapy for endometrial cancer. Longer follow-up and more outcome studies are needed to determine whether any differences exist between the two approaches.

  3. Fractionated stereotactic radiotherapy: A method to evaluate geometric and dosimetric uncertainties using radiochromic films

    SciTech Connect

    Coscia, Gianluca; Vaccara, Elena; Corvisiero, Roberta; Cavazzani, Paolo; Ruggieri, Filippo Grillo; Taccini, Gianni

    2009-07-15

    In the authors' hospital, stereotactic radiotherapy treatments are performed with a Varian Clinac 600C equipped with a BrainLAB m3 micro-multileaf-collimator generally using the dynamic conformal arc technique. Patient immobilization during the treatment is achieved with a fixation mask supplied by BrainLAB, made with two reinforced thermoplastic sheets fitting the patient's head. With this work the authors propose a method to evaluate treatment geometric accuracy and, consequently, to determine the amount of the margin to keep in the CTV-PTV expansion during the treatment planning. The reproducibility of the isocenter position was tested by simulating a complete treatment on the anthropomorphic phantom Alderson Rando, inserting in between two phantom slices a high sensitivity Gafchromic EBT film, properly prepared and calibrated, and repeating several treatment sessions, each time removing the fixing mask and replacing the film inside the phantom. The comparison between the dose distributions measured on films and computed by TPS, after a precise image registration procedure performed by a commercial piece of software (FILMQA, 3cognition LLC (Division of ISP), Wayne, NJ), allowed the authors to measure the repositioning errors, obtaining about 0.5 mm in case of central spherical PTV and about 1.5 mm in case of peripheral irregular PTV. Moreover, an evaluation of the errors in the registration procedure was performed, giving negligible values with respect to the quantities to be measured. The above intrinsic two-dimensional estimate of treatment accuracy has to be increased for the error in the third dimension, but the 2 mm margin the authors generally use for the CTV-PTV expansion seems adequate anyway. Using the same EBT films, a dosimetric verification of the treatment planning system was done. Measured dose values are larger or smaller than the nominal ones depending on geometric irradiation conditions, but, in the authors' experimental conditions, always

  4. Stereotactic body radiation therapy (SBRT) and respiratory gating in lung cancer: dosimetric and radiobiological considerations.

    PubMed

    De La Fuente Herman, Tania; Vlachaki, Maria T; Herman, Terence S; Hibbitts, Kerry; Stoner, Julie A; Ahmad, Salahuddin

    2010-01-29

    The purpose of this study was to assess the impact of respiratory gating on tumor and normal tissue dosimetry in patients treated with SBRT for early stage non-small cell lung cancer (NSCLC). Twenty patients with stage I NSCLC were studied. Treatment planning was performed using four-dimensional computed tomography (4D CT) with free breathing (Plan I), near-end inhalation (Plan II), and near-end exhalation (Plan III). The prescription dose was 60 Gy in three fractions. The tumor displacement was most pronounced for lower peripheral lesions (average 7.0 mm, range 4.1-14.3 mm) when compared to upper peripheral (average 2.4mm, range 1.0-5.1 mm) or central lesions (average 2.9 mm, range 1.0-4.1 mm). In this study, the pencil beam convolution (PBC) algorithm with modified Batho power law for tissue heterogeneity was used for dose calculation. There were no significant differences in tumor and normal tissue dosimetry among the three gated plans. Tumor location however, significantly influenced tumor doses because of the necessity of respecting normal tissue constraints of centrally located structures. For plans I, II and III, average doses to central lesions were lower as compared with peripheral lesions by 4.88 Gy, 8.24 Gy and 6.93 Gy for minimum PTV and 0.98, 1.65 and 0.87 Gy for mean PTV dose, respectively. As a result, the mean single fraction equivalent dose (SFED) values were also lower for central compared to peripheral lesions. In addition, central lesions resulted in higher mean doses for lung, esophagus, and ipsilateral bronchus by 1.24, 1.93 and 7.75 Gy, respectively. These results indicate that the tumor location is the most important determinant of dosimetric optimization of SBRT plans. Respiratory gating proved unhelpful in the planning of these patients with severe COPD.

  5. Dosimetric comparison of IMRT rectal and anal canal plans generated using an anterior dose avoidance structure

    SciTech Connect

    Leicher, Brian; Day, Ellen; Colonias, Athanasios; Gayou, Olivier

    2014-10-01

    To describe a dosimetric method using an anterior dose avoidance structure (ADAS) during the treatment planning process for intensity-modulated radiation therapy (IMRT) for patients with anal canal and rectal carcinomas. A total of 20 patients were planned on the Elekta/CMS XiO treatment planning system, version 4.5.1 (Maryland Heights MO) with a superposition algorithm. For each patient, 2 plans were created: one employing an ADAS (ADAS plan) and the other replanned without an ADAS (non-ADAS plan). The ADAS was defined to occupy the volume between the inguinal nodes and primary target providing a single organ at risk that is completely outside of the target volume. Each plan used the same beam parameters and was analyzed by comparing target coverage, overall plan dose conformity using a conformity number (CN) equation, bowel dose-volume histograms, and the number of segments, daily treatment duration, and global maximum dose. The ADAS and non-ADAS plans were equivalent in target coverage, mean global maximum dose, and sparing of small bowel in low-dose regions (5, 10, 15, and 20 Gy). The mean difference between the CN value for the non-ADAS plans and ADAS plans was 0.04 ± 0.03 (p < 0.001). The mean difference in the number of segments was 15.7 ± 12.7 (p < 0.001) in favor of ADAS plans. The ADAS plan delivery time was shorter by 2.0 ± 1.5 minutes (p < 0.001) than the non-ADAS one. The ADAS has proven to be a powerful tool when planning rectal and anal canal IMRT cases with critical structures partially contained inside the target volume.

  6. Dosimetric Comparison of Tandem and Ovoids vs. Tandem and Ring for Intracavitary Gynecologic Applications

    SciTech Connect

    Levin, Daphne Menhel, Janna; Rabin, Tanya; Pfeffer, M. Raphael; Symon, Zvi

    2008-01-01

    We evaluated dosimetric differences in tandem and ovoid (TO) and tandem and ring (TR) gynecologic brachytherapy applicators. Seventeen patients with cervical cancer (Stages II-IV) receiving 3 high-dose-rate (HDR) brachytherapy applications (both TO and TR) were studied. Patients underwent computed tomography (CT) scans with contrast in bladder, and were prescribed 8 Gy to ICRU points A, with additional optimization goals of maintaining the pear-shaped dose distribution and minimizing bladder and rectum doses. Bladder and rectum point doses, mean, and maximum doses were calculated. Total treatment time and volumes treated to 95%, 85%, 50%, and 20% or the prescription dose were compared. There were no significant differences between TO and TR applicators in doses to prescription points or critical organs. However, there were significant differences (p < 0.001) between the applicators in treated volumes and total treatment time. The TO treated larger volumes over a longer time. Within each patient, when the applicators were compared, treated volumes were also found to be significantly different (p < 0.01, {chi}{sup 2}). Our results demonstrate that the 2 applicators, while delivering the prescribed dose to points A and keeping critical organ doses below tolerance, treat significantly different volumes. It is unclear if this difference is clinically meaningful. TO applicators may be treating surrounding healthy tissue unnecessarily, or TR applicators may be underdosing tumor tissue. Further investigation with appropriate imaging modalities is required for accurate delineation of target volumes. Clearly, the TO and TR are not identical, and should not be used interchangeably without further study.

  7. Dosimetric Advantages of Midventilation Compared With Internal Target Volume for Radiation Therapy of Pancreatic Cancer

    SciTech Connect

    Lens, Eelco Horst, Astrid van der; Versteijne, Eva; Tienhoven, Geertjan van; Bel, Arjan

    2015-07-01

    Purpose: The midventilation (midV) approach can be used to take respiratory-induced pancreatic tumor motion into account during radiation therapy. In this study, the dosimetric consequences for organs at risk and tumor coverage of using a midV approach compared with using an internal target volume (ITV) were investigated. Methods and Materials: For each of the 18 patients, 2 treatment plans (25 × 2.0 Gy) were created, 1 using an ITV and 1 using a midV approach. The midV dose distribution was blurred using the respiratory-induced motion from 4-dimensional computed tomography. The resulting planning target volume (PTV) coverage for this blurred dose distribution was analyzed; PTV coverage was required to be at least V{sub 95%} >98%. In addition, the change in PTV size and the changes in V{sub 10Gy}, V{sub 20Gy}, V{sub 30Gy}, V{sub 40Gy}, D{sub mean} and D{sub 2cc} for the stomach and for the duodenum were analyzed; differences were tested for significance using the Wilcoxon signed-rank test. Results: Using a midV approach resulted in sufficient target coverage. A highly significant PTV size reduction of 13.9% (P<.001) was observed. Also, all dose parameters for the stomach and duodenum, except the D{sub 2cc} of the duodenum, improved significantly (P≤.002). Conclusions: By using the midV approach to account for respiratory-induced tumor motion, a significant PTV reduction and significant dose reductions to the stomach and to the duodenum can be achieved when irradiating pancreatic tumors.

  8. Dosimetric evaluation of simultaneous integrated boost during stereotactic body radiation therapy for pancreatic cancer

    SciTech Connect

    Yang, Wensha; Reznik, Robert; Fraass, Benedick A.; Nissen, Nicholas; Hendifar, Andrew; Wachsman, Ashley; Sandler, Howard; Tuli, Richard

    2015-04-01

    Stereotactic body radiation therapy (SBRT) provides a promising way to treat locally advanced pancreatic cancer and borderline resectable pancreatic cancer. A simultaneous integrated boost (SIB) to the region of vessel abutment or encasement during SBRT has the potential to downstage otherwise likely positive surgical margins. Despite the potential benefit of using SIB-SBRT, the ability to boost is limited by the local geometry of the organs at risk (OARs), such as stomach, duodenum, and bowel (SDB), relative to tumor. In this study, we have retrospectively replanned 20 patients with 25 Gy prescribed to the planning target volume (PTV) and 33~80 Gy to the boost target volume (BTV) using an SIB technique for all patients. The number of plans and patients able to satisfy a set of clinically established constraints is analyzed. The ability to boost vessels (within the gross target volume [GTV]) is shown to correlate with the overlap volume (OLV), defined to be the overlap between the GTV + a 1(OLV1)- or 2(OLV2)-cm margin with the union of SDB. Integral dose, boost dose contrast (BDC), biologically effective BDC, tumor control probability for BTV, and normal tissue complication probabilities are used to analyze the dosimetric results. More than 65% of the cases can deliver a boost to 40 Gy while satisfying all OAR constraints. An OLV2 of 100 cm{sup 3} is identified as the cutoff volume: for cases with OLV2 larger than 100 cm{sup 3}, it is very unlikely the case could achieve 25 Gy to the PTV while successfully meeting all the OAR constraints.

  9. Consequences of the spectral response of an a-Si EPID and implications for dosimetric calibration

    SciTech Connect

    Kirkby, C.; Sloboda, R.

    2005-08-15

    One of the attractive features of amorphous silicon electronic portal imaging devices (a-Si EPIDs) as dosimetric tools is that for open fields they are known to exhibit a generally linear relation between pixel value and incident energy fluence as measured by an ion chamber. It has also been established that a-Si EPIDs incorporating high atomic number phosphors such as Gd{sub 2}O{sub 2}S:Tb exhibit a disproportionately large response to low-energy (<1 MeV) photons. The present work examines the consequences of this hypersensitivity in a commercially available EPID, the Varian aS500, with respect to energy fluence calibration in a 6 MV radiotherapy beam. EPIDs may be deployed in situations where the spectrum of the incident beam is modified by passing through a compensator or through a patient or phantom. By examining the specific case of a beam hardened by passage through compensator material, we show that the discrepancy between open and attenuated beam calibration curves can be as high as 8%. A Monte Carlo study using a comprehensive model of the aS500 shows that this difference can be explained by spectral changes, and further suggests that it can be reduced by the addition of an external copper plate. We consider configurations with the plate placed directly on top of the EPID cassette and 15 cm above the cassette, supported by Styrofoam. In order to reduce the maximum discrepancy to <4%, it was found that a copper thickness of {approx}0.7 cm was required in the elevated configuration. Improvement was minimal with the copper in the contact configuration. Adding 0.7 cm of copper in the elevated configuration reduced the contrast-to-noise ratio by 19% and the modulation transfer for a given spatial frequency by 30%.

  10. Dosimetric impact of number of treatment fields in uniform scanning proton therapy planning of lung cancer

    PubMed Central

    Rana, Suresh; Simpson, Hilarie; Larson, Gary; Zheng, Yuanshui

    2014-01-01

    The main purpose of this study was to perform a treatment planning study for lung cancer comparing 2-field (2F) versus 3-field (3F) techniques in uniform scanning proton therapy (USPT). Ten clinically approved lung cancer treatment plans delivered using USPT at our proton center were included in this retrospective study. All 10 lung cases included 4D computed tomography (CT) simulation. The delineation of target volumes was done based on the maximum intensity projection (MIP) images. Both the 3F and 2F treatment plans were generated for the total dose of 74 cobalt-gray-equivalent (CGE) with a daily dose of 2 CGE. 3F plan was generated by adding an extra beam in the 2F plan. Various dosimetric parameters between 2F and 3F plans were evaluated. 3F plans produced better target coverage and conformality as well as lower mean dose to the lung, with absolute difference between 3F and 2F plans within 2%. In contrast, the addition of third beam led to increase of low-dose regions (V20 and V5) in the lung in 3F plans compared to the ones in 2F plans with absolute difference within 2%. Maximum dose to the spinal cord was lower in 2F plans. Mean dose to the heart and esophagus were comparable in both 3F and 2F plans. In conclusion, the 3F technique in USPT produced better target coverage and conformality, but increased the low-dose regions in the lung when compared to 2F technique. PMID:25525308

  11. Computed Tomography Appearance of Early Radiation Injury to the Lung: Correlation With Clinical and Dosimetric Factors

    SciTech Connect

    Jenkins, Peter; Welsh, Anne

    2011-09-01

    Purpose: To systematically assess the spectrum of radiologic changes in the lung after radiation therapy for non-small-cell lung cancer. Methods and Materials: We reviewed the cases of 146 patients treated with radical radiotherapy at our institution. All patients had computed tomography (CT) scans performed 3 months after completion of therapy. Radiographic appearances were categorized using a standard grading system. The association of these abnormalities with pretreatment factors and clinical radiation pneumonitis (RP) was investigated. Results: New intrapulmonary abnormalities were seen in 92 patients (63%). These were ground-glass opacity in 16 (11%), patchy consolidation in 19 (13%), and diffuse consolidation in 57 (39%). Twenty-five patients (17%) developed clinical symptoms of RP. Although 80% of the patients with RP had areas of consolidation seen on the posttreatment CT scan, the majority (74%) of patients with such radiographic changes were asymptomatic. For patients with lung infiltrates, the minimum isodose encompassing the volume of radiologic abnormality was usually {>=}27 Gy. Traditional dose-volume metrics, pulmonary function tests, and the coadministration of angiotensin converting enzyme inhibitors (ACE-I) were all strongly correlated with the presence of radiologic injury on univariate analysis (p {<=} 0.002). There was also an inverse correlation between prior smoking history and CT scan changes (p = 0.02). On multivariate analysis, dosimetric parameters and the use of ACE-I retained significance (p = 0.005). Conclusions: Our findings suggest that there is substantial interindividual variation in lung radiosensitivity. ACE-I prevented the radiologic changes seen after high-dose radiation therapy, and their role as radioprotectants warrants further investigation.

  12. Evaluation of the dosimetric accuracy for a couch-based tracking system (CBTS)

    NASA Astrophysics Data System (ADS)

    Chang, Kyung Hwan; Lee, Suk; Kim, Kwang Hyeon; Shim, Jang Bo; Yang, Dae Sik; Park, Young Je; Yoon, Won Sup; Kim, Chul Yong; Cao, Yuanjie

    2016-07-01

    In this study, the geometric and dosimetric accuracy of an in-house-developed couch-based tracking system (CBTS) was investigated using both film and in-house-developed polymer gel dosimeters. We evaluated the 1D and the 2D motion accuracies of our couch system by using Gafchromic EBT film. For the 1D test, the couch system was moved 5, 10, and 20 mm in the X, Y, and Z directions, respectively. Meanwhile, for the 2D test, it was moved along the XY, YZ, and ZX directions. We compared the profiles, full widths at half maximum (FWHMs), and penumbras between the static and the tracking fields. For the 3D test, we quantitatively compared the dose distribution between the static and the tracking fields by using the polymer gel dosimeter when it was simultaneously moved in the XYZ directions. We confirmed that the film was moved according to motion amplitudes of 5, 10, and 20 mm in the X, Y, and Z directions, respectively, in the 1D and 2D motion tests. The value of the FWHM of the static field and the three tracking fields were 51.88, 53.28, 57.67, and 64.43 mm, respectively. Two types of penumbras became wider with increasing amplitudes compared to the static field. For the 3D test, the dose distribution of the XYZ tracking field was qualitatively larger than that of the static field. We conclude that this CBTS has the potential for pre-clinical applications in adaptive radiation therapy.

  13. NOTE: Practical and dosimetric implications of a new type of packaging for radiographic film

    NASA Astrophysics Data System (ADS)

    Gillis, S.; DeWagter, C.

    2005-04-01

    Recently, Kodak introduced new light-tight packages (vacuum packaging, aluminium layer under black polyethylene and different paper) for their oncology films (EDR-2, X-Omat V and PPL-2). In order to avoid additional uncertainty and to ensure transferability of previously published results, we assessed in this study the effect of the old and new packages on the dosimetric response of EDR-2 radiographic film. Therefore, sensitometric measurements were performed for different film assemblies (new envelope + new paper, old envelope + old paper, new envelope without paper and old envelope without paper). In addition, to assess possible effects of the package on the film depth dose response, packaged films were irradiated in parallel geometry, and central depth dose curves were retrieved. For the perpendicular geometry, on the other hand, the effect of the package was assessed at large depth for a high intensity-modulated inverse-pyramid beam. The results of the sensitometric measurements reveal no difference between the packages. However, the white colour of the paper in both the packages induces a dose-dependent increase in optical density (0 0.12) of the film. The depth dose curves show better reproducibility for the new package and the new paper improves the accuracy of film dosimetry, but despite the company's effort to evacuate the air out of the new envelope, it remains necessary to clamp the films in the phantom for the parallel irradiation geometry. At 5 cm depth, the films irradiated in parallel geometry show an under-response of 3 5% compared to films irradiated perpendicularly. Finally, even at locations of large photon scatter, no filtration effect from the aluminium layer incorporated in the new envelope has been observed for perpendicular irradiation geometry.

  14. Design and dosimetric characteristics of a new endocavitary contact radiotherapy system using an electronic brachytherapy source

    SciTech Connect

    Richardson, Susan; Garcia-Ramirez, Jose; Lu Wei; Myerson, Robert J.; Parikh, Parag

    2012-11-15

    Purpose: To present design aspects and acceptance tests performed for clinical implementation of electronic brachytherapy treatment of early stage rectal adenocarcinoma. A dosimetric comparison is made between the historically used Philips RT-50 unit and the newly developed Axxent{sup Registered-Sign} Model S700 electronic brachytherapy source manufactured by Xoft (iCad, Inc.). Methods: Two proctoscope cones were manufactured by ElectroSurgical Instruments (ESI). Two custom surface applicators were manufactured by Xoft and were designed to fit and interlock with the proctoscope cones from ESI. Dose rates, half value layers (HVL), and percentage depth dose (PDD) measurements were made with the Xoft system and compared to historical RT-50 data. A description of the patient treatment approach and exposure rates during the procedure is also provided. Results: The electronic brachytherapy system has a lower surface dose rate than the RT-50. The dose rate to water on the surface from the Xoft system is approximately 2.1 Gy/min while the RT-50 is 10-12 Gy/min. However, treatment times with Xoft are still reasonable. The HVLs and PDDs between the two systems were comparable resulting in similar doses to the target and to regions beyond the target. The exposure rate levels around a patient treatment were acceptable. The standard uncertainty in the dose rate to water on the surface is approximately {+-}5.2%. Conclusions: The Philips RT-50 unit is an out-of-date radiotherapy machine that is no longer manufactured with limited replacement parts. The use of a custom-designed proctoscope and Xoft surface applicators allows delivery of a well-established treatment with the ease of a modern radiotherapy device. While the dose rate is lower with the use of Xoft, the treatment times are still reasonable. Additionally, personnel may stand farther away from the Xoft radiation source, thus potentially reducing radiation exposure to the operator and other personnel.

  15. Stereotactic body radiation therapy for liver tumours using flattening filter free beam: dosimetric and technical considerations

    PubMed Central

    2012-01-01

    Purpose To report the initial institute experience in terms of dosimetric and technical aspects in stereotactic body radiation therapy (SBRT) delivered using flattening filter free (FFF) beam in patients with liver lesions. Methods and Materials From October 2010 to September 2011, 55 consecutive patients with 73 primary or metastatic hepatic lesions were treated with SBRT on TrueBeam using FFF beam and RapidArc technique. Clinical target volume (CTV) was defined on multi-phase CT scans, PET/CT, MRI, and 4D-CT. Dose prescription was 75 Gy in 3 fractions to planning target volume (PTV). Constraints for organs at risk were: 700 cc of liver free from the 15 Gy isodose, Dmax < 21 Gy for stomach and duodenum, Dmax < 30 Gy for heart, D0.1 cc < 18 Gy for spinal cord, V15 Gy < 35% for kidneys. The dose was downscaled in cases of not full achievement of dose constraints. Daily cone beam CT (CBCT) was performed. Results Forty-three patients with a single lesion, nine with two lesions and three with three lesions were treated with this protocol. Target and organs at risk objectives were met for all patients. Mean delivery time was 2.8 ± 1.0 min. Pre-treatment plan verification resulted in a Gamma Agreement Index of 98.6 ± 0.8%. Mean on-line co-registration shift of the daily CBCT to the simulation CT were: -0.08, 0.05 and -0.02 cm with standard deviations of 0.33, 0.39 and 0.55 cm in, vertical, longitudinal and lateral directions respectively. Conclusions SBRT for liver targets delivered by means of FFF resulted to be feasible with short beam on time. PMID:22296849

  16. Radioiodine therapy in patients with hyperthyroid disorder: standard versus dosimetric activity application.

    PubMed

    Reinartz, P; Zimny, M; Schaefer, W; Mueller, B; Buell, U; Sabri, O

    2003-12-01

    Due to its high success rate and non-invasive character, an increasing demand for radioiodine therapy can be seen. This study was conducted to determine whether standardized 131I activities can be used to facilitate management of patients with hyperthyroid disorder or whether a pre-therapeutic radioiodine test is advisable to determine an adequate therapeutic activity. The therapeutic uptake of 218 patients with benign thyroid disorders were determined and compared with 24 h and 48 h test uptake measurements as well as with calculated standard uptake values. Since there is a linear relationship between iodine uptake and delivered radiation dose, the effect of the different therapeutic approaches on the latter parameter was analysed. Special care was taken to assess possible differences between the various thyroid disorders. A mean deviation between pre-therapeutic test uptake and actual therapeutic uptake of 14.7% was observed in contrast to one of 29.1% when using disease specific standard values per millilitre of thyroid tissue. Furthermore, the proportion of patients with large deviations of more than 40% increased drastically when using standard uptake values (with radioiodine test, 4.1%; with standard values, 18.8%). In conclusion, the dosimetric approach with a pre-therapeutic radioiodine test proved to be the most accurate therapeutic procedure. Both the 24 h and 48 h test uptake measurements gave analogous results and yielded a correlation coefficient of 0.91 when compared with the therapeutic uptake. While it may be tempting to use standard activities to facilitate patient management, the findings of this study confirm that, for precise therapy planning, a pre-therapeutic radioiodine test is advised. Since no significant difference could be found between the 24 h and 48 h test uptake values, an early measurement 24 h after administration of the test activity is recommended. PMID:14627852

  17. Postoperative radiotherapy following mastectomy for patients with left-sided breast cancer: A comparative dosimetric study

    SciTech Connect

    Wang, Jiahao; Li, Xiadong; Deng, Qinghua; Xia, Bing; Wu, Shixiu; Liu, Jian; Ma, Shenglin

    2015-10-01

    The purposes of this article were to compare the biophysical dosimetry for postmastectomy left-sided breast cancer using 4 different radiotherapy (RT) techniques. In total, 30 patients with left-sided breast cancer were randomly selected for this treatment planning study. They were planned using 4 RT techniques, including the following: (1) 3-dimensional conventional tangential fields (TFs), (2) tangential intensity-modulated therapy (T-IMRT), (3) 4 fields IMRT (4F-IMRT), and (4) single arc volumetric-modulated arc therapy (S-VMAT). The planning target volume (PTV) dose was prescribed 50 Gy, the comparison of target dose distribution, conformity index, homogeneity index, dose to organs at risk (OARs), tumor control probability (TCP), normal tissue complication probability (NTCP), and number of monitor units (MUs) between 4 plans were investigated for their biophysical dosimetric difference. The target conformity and homogeneity of S-VMAT were better than the other 3 kinds of plans, but increased the volume of OARs receiving low dose (V{sub 5}). TCP of PTV and NTCP of the left lung showed no statistically significant difference in 4 plans. 4F-IMRT plan was superior in terms of target coverage and protection of OARs and demonstrated significant advantages in decreasing the NTCP of heart by 0.07, 0.03, and 0.05 compared with TFs, T-IMRT, and S-VMAT plan. Compared with other 3 plans, TFs reduced the average number of MUs. Of the 4 techniques studied, this analysis supports 4F-IMRT as the most appropriate balance of target coverage and normal tissue sparing.

  18. Dosimetric analysis and comparison of IMRT and HDR brachytherapy in treatment of localized prostate cancer

    PubMed Central

    Murali, V.; Kurup, P. G. G.; Mahadev, P.; Mahalakshmi, S.

    2010-01-01

    Radical radiotherapy is one of the options for the management of prostate cancer. In external beam therapy, 3D conformal radiotherapy (3DCRT) and intensity modulated radiotherapy (IMRT) are the options for delivery of increased radiation dose, as vital organs are very close to the prostate and a higher dose to these structures leads to an increased toxicity. In brachytherapy, low dose rate brachytherapy with permanent implant of radioactive seeds and high dose rate brachytherapy (HDR) with remote after loaders are available. A dosimetric analysis has been made on IMRT and HDR brachytherapy plans. Ten cases from each IMRT and HDR brachytherapy have been taken for the study. The analysis includes comparison of conformity and homogeneity indices, D100, D95, D90, D80, D50, D10 and D5 of the target. For the organs at risk (OAR), namely rectum and bladder, V100, V90 and V50 are compared. In HDR brachytherapy, the doses to 1 cc and 0.1 cc of urethra have also been studied. Since a very high dose surrounds the source, the 300% dose volumes in the target and within the catheters are also studied in two plans, to estimate the actual volume of target receiving dose over 300%. This study shows that the prescribed dose covers 93 and 92% of the target volume in IMRT and HDR brachytherapy respectively. HDR brachytherapy delivers a much lesser dose to OAR, compared to the IMRT. For rectum, the V50 in IMRT is 34.0cc whilst it is 7.5cc in HDR brachytherapy. With the graphic optimization tool in HDR brachytherapy planning, the dose to urethra could be kept within 120% of the target dose. Hence it is concluded that HDR brachytherapy may be the choice of treatment for cancer of prostate in the early stage. PMID:20589121

  19. Dosimetric perturbation from cloth and paper gowns for total skin electron irradiation.

    PubMed

    Steinman, James P; Hopkins, Shane L; Wang, Iris Z

    2013-01-01

    Traditionally, total skin electron patients remove all clothing for treatment. It is generally assumed that this is best for the treatment of superficial skin lesions out of concern clothing may significantly perturb dose. We investigate the dosimetric effect of patient gowns and determine the necessity of treating patients naked. Using GAFCHROMIC EBT2 film, dose to a cylindrical phantom was measured with cloth, paper, and tri-layer cloth gowns, compared to no covering. A 6 MeV electron beam with spoiler accessory was used at ~ 4 meters source-to-skin distance. The gantry was angled at 248° and 292°. The phantom was rotated at -60°, 0°, and 60° relative to the beam's central axis, simulating the Stanford technique. This was also repeated for films sandwiched between the phantom's discs. Using a Markus chamber, the effect of air gaps of 0 to 5 cm in cloth and paper gowns was measured. The water equivalent attenuation of the gowns was determined through transmission studies. Compared to no covering, films placed on the phantom surface revealed an average increase of 0.8% in dose for cloth, 1.8% for tri-layered cloth, and 0.7% for paper. Films sandwiched within the phantom showed only slight shift of the percent depth-dose curves. Markus chamber readings revealed 1.4% for tri-layered cloth, and < 0.2% for single layer cloth or paper. Air gaps appeared to have a minimal effect. Transmission measurements found that one layer of cloth is equal to 0.2mm of solid water. Cloth and paper gowns appear to slightly increase the dose to the skin, but will not introduce any significant dose perturbation (<1%). Gowns having folds and extra layers will have a small additional perturbation (<2%). To minimize perturbation, one should smooth out any folds or remove any pockets that form extra layers on the gown.

  20. TH-E-BRE-05: Analysis of Dosimetric Characteristics in Two Leaf Motion Calculator Algorithms for Sliding Window IMRT

    SciTech Connect

    Wu, L; Huang, B; Rowedder, B; Ma, B; Kuang, Y

    2014-06-15

    Purpose: The Smart leaf motion calculator (SLMC) in Eclipse treatment planning system is an advanced fluence delivery modeling algorithm as it takes into account fine MLC features including inter-leaf leakage, rounded leaf tips, non-uniform leaf thickness, and the spindle cavity etc. In this study, SLMC and traditional Varian LMC (VLMC) algorithms were investigated, for the first time, in dosimetric characteristics and delivery accuracy of sliding window (SW) IMRT. Methods: The SW IMRT plans of 51 cancer cases were included to evaluate dosimetric characteristics and dose delivery accuracy from leaf motion calculated by SLMC and VLMC, respectively. All plans were delivered using a Varian TrueBeam Linac. The DVH and MUs of the plans were analyzed. Three patient specific QA tools - independent dose calculation software IMSure, Delta4 phantom, and EPID portal dosimetry were also used to measure the delivered dose distribution. Results: Significant differences in the MUs were observed between the two LMCs (p≤0.001).Gamma analysis shows an excellent agreement between the planned dose distribution calculated by both LMC algorithms and delivered dose distribution measured by three QA tools in all plans at 3%/3 mm, leading to a mean pass rate exceeding 97%. The mean fraction of pixels with gamma < 1 of SLMC is slightly lower than that of VLMC in the IMSure and Delta4 results, but higher in portal dosimetry (the highest spatial resolution), especially in complex cases such as nasopharynx. Conclusion: The study suggests that the two LMCs generates the similar target coverage and sparing patterns of critical structures. However, SLMC is modestly more accurate than VLMC in modeling advanced MLC features, which may lead to a more accurate dose delivery in SW IMRT. Current clinical QA tools might not be specific enough to differentiate the dosimetric discrepancies at the millimeter level calculated by these two LMC algorithms. NIH/NIGMS grant U54 GM104944, Lincy Endowed

  1. Dosimetric and Late Radiation Toxicity Comparison Between Iodine-125 Brachytherapy and Stereotactic Radiation Therapy for Juxtapapillary Choroidal Melanoma

    SciTech Connect

    Krema, Hatem

    2013-07-01

    Purpose: To compare the dose distributions and late radiation toxicities for {sup 125}I brachytherapy (IBT) and stereotactic radiation therapy (SRT) in the treatment of juxtapapillary choroidal melanoma. Methods: Ninety-four consecutive patients with juxtapapillary melanoma were reviewed: 30 have been treated with IBT and 64 with SRT. Iodine-125 brachytherapy cases were modeled with plaque simulator software for dosimetric analysis. The SRT dosimetric data were obtained from the Radionics XKnife RT3 software. Mean doses at predetermined intraocular points were calculated. Kaplan-Meier estimates determined the actuarial rates of late toxicities, and the log–rank test compared the estimates. Results: The median follow-up was 46 months in both cohorts. The 2 cohorts were balanced with respect to pretreatment clinical and tumor characteristics. Comparisons of radiation toxicity rates between the IBT and SRT cohorts yielded actuarial rates at 50 months for cataracts of 62% and 75% (P=.1), for neovascular glaucoma 8% and 47% (P=.002), for radiation retinopathy 59% and 89% (P=.0001), and for radiation papillopathy 39% and 74% (P=.003), respectively. Dosimetric comparisons between the IBT and SRT cohorts yielded mean doses of 12.8 and 14.1 Gy (P=.56) for the lens center, 17.6 and 19.7 Gy (P=.44) for the lens posterior pole, 13.9 and 10.8 Gy (P=.30) for the ciliary body, 61.9 and 69.7 Gy (P=.03) for optic disc center, and 48.9 and 60.1 Gy (P<.0001) for retina at 5-mm distance from tumor margin, respectively. Conclusions: Late radiation-induced toxicities were greater with SRT, which is secondary to the high-dose exposure inherent to the technique as compared with IBT. When technically feasible, IBT is preferred to treat juxtapapillary choroidal melanoma.

  2. SU-F-BRE-04: Construction of 3D Printed Patient Specific Phantoms for Dosimetric Verification Measurements

    SciTech Connect

    Ehler, E; Higgins, P; Dusenbery, K

    2014-06-15

    Purpose: To validate a method to create per patient phantoms for dosimetric verification measurements. Methods: Using a RANDO phantom as a substitute for an actual patient, a model of the external features of the head and neck region of the phantom was created. A phantom was used instead of a human for two reasons: to allow for dosimetric measurements that would not be possible in-vivo and to avoid patient privacy issues. Using acrylonitrile butadiene styrene thermoplastic as the building material, a hollow replica was created using the 3D printer filled with a custom tissue equivalent mixture of paraffin wax, magnesium oxide, and calcium carbonate. A traditional parallel-opposed head and neck plan was constructed. Measurements were performed with thermoluminescent dosimeters in both the RANDO phantom and in the 3D printed phantom. Calculated and measured dose was compared at 17 points phantoms including regions in high and low dose regions and at the field edges. On-board cone beam CT was used to localize both phantoms within 1mm and 1° prior to radiation. Results: The maximum difference in calculated dose between phantoms was 1.8% of the planned dose (180 cGy). The mean difference between calculated and measured dose in the anthropomorphic phantom and the 3D printed phantom was 1.9% ± 2.8% and −0.1% ± 4.9%, respectively. The difference between measured and calculated dose was determined in the RANDO and 3D printed phantoms. The differences between measured and calculated dose in each respective phantom was within 2% for 12 of 17 points. The overlap of the RANDO and 3D printed phantom was 0.956 (Jaccard Index). Conclusion: A custom phantom was created using a 3D printer. Dosimetric calculations and measurements showed good agreement between the dose in the RANDO phantom (patient substitute) and the 3D printed phantom.

  3. Dosimetric comparison of split field and fixed jaw techniques for large IMRT target volumes in the head and neck.

    PubMed

    Srivastava, Shiv P; Das, Indra J; Kumar, Arvind; Johnstone, Peter A S

    2011-01-01

    Some treatment planning systems (TPSs), when used for large-field (>14 cm) intensity-modulated radiation therapy (IMRT), create split fields that produce excessive multiple-leaf collimator segments, match-line dose inhomogeneity, and higher treatment times than nonsplit fields. A new method using a fixed-jaw technique (FJT) forces the jaw to stay at a fixed position during optimization and is proposed to reduce problems associated with split fields. Dosimetric comparisons between split-field technique (SFT) and FJT used for IMRT treatment is presented. Five patients with head and neck malignancies and regional target volumes were studied and compared with both techniques. Treatment planning was performed on an Eclipse TPS using beam data generated for Varian 2100C linear accelerator. A standard beam arrangement consisting of nine coplanar fields, equally spaced, was used in both techniques. Institutional dose-volume constraints used in head and neck cancer were kept the same for both techniques. The dosimetric coverage for the target volumes between SFT and FJT for head and neck IMRT plan is identical within ± 1% up to 90% dose. Similarly, the organs at risk (OARs) have dose-volume coverage nearly identical for all patients. When the total monitor unit (MU) and segments were analyzed, SFT produces statistically significant higher segments (17.3 ± 6.3%) and higher MU (13.7 ± 4.4%) than the FJT. There is no match line in FJT and hence dose uniformity in the target volume is superior to the SFT. Dosimetrically, SFT and FJT are similar for dose-volume coverage; however, the FJT method provides better logistics, lower MU, shorter treatment time, and better dose uniformity. The number of segments and MU also has been correlated with the whole body radiation dose with long-term complications. Thus, FJT should be the preferred option over SFT for large target volumes.

  4. Dosimetric Comparison of Split Field and Fixed Jaw Techniques for Large IMRT Target Volumes in the Head and Neck

    SciTech Connect

    Srivastava, Shiv P.; Das, Indra J.; Kumar, Arvind; Johnstone, Peter A.S.

    2011-04-01

    Some treatment planning systems (TPSs), when used for large-field (>14 cm) intensity-modulated radiation therapy (IMRT), create split fields that produce excessive multiple-leaf collimator segments, match-line dose inhomogeneity, and higher treatment times than nonsplit fields. A new method using a fixed-jaw technique (FJT) forces the jaw to stay at a fixed position during optimization and is proposed to reduce problems associated with split fields. Dosimetric comparisons between split-field technique (SFT) and FJT used for IMRT treatment is presented. Five patients with head and neck malignancies and regional target volumes were studied and compared with both techniques. Treatment planning was performed on an Eclipse TPS using beam data generated for Varian 2100C linear accelerator. A standard beam arrangement consisting of nine coplanar fields, equally spaced, was used in both techniques. Institutional dose-volume constraints used in head and neck cancer were kept the same for both techniques. The dosimetric coverage for the target volumes between SFT and FJT for head and neck IMRT plan is identical within {+-}1% up to 90% dose. Similarly, the organs at risk (OARs) have dose-volume coverage nearly identical for all patients. When the total monitor unit (MU) and segments were analyzed, SFT produces statistically significant higher segments (17.3 {+-} 6.3%) and higher MU (13.7 {+-} 4.4%) than the FJT. There is no match line in FJT and hence dose uniformity in the target volume is superior to the SFT. Dosimetrically, SFT and FJT are similar for dose-volume coverage; however, the FJT method provides better logistics, lower MU, shorter treatment time, and better dose uniformity. The number of segments and MU also has been correlated with the whole body radiation dose with long-term complications. Thus, FJT should be the preferred option over SFT for large target volumes.

  5. Dosimetric Comparison of Helical Tomotherapy and Linac-IMRT Treatment Plans for Head and Neck Cancer Patients

    SciTech Connect

    Zhang Xin; Penagaricano, Jose; Moros, Eduardo G.; Corry, Peter M.; Yan Yulong; Ratanatharathorn, Vaneerat

    2010-01-01

    The rapid development and clinical implementation of external beam radiation treatment technologies continues. The existence of various commercially available technologies for intensity-modulated radiation therapy (IMRT) has stimulated interest in exploring the differential potential advantage one may have compared with another. Two such technologies, Hi-Art Helical Tomotherapy (HT) and conventional medical linear accelerator-based IMRT (LIMRT) have been shown to be particularly suitable for the treatment of head and neck cancers. In this study, 23 patients who were diagnosed with stages 3 or 4 head and neck cancers, without evidence of distance metastatic disease, were treated in our clinic. Treatment plans were developed for all patients simultaneously on the HT planning station and on the Pinnacle treatment planning system for step-and-shoot IMRT. Patients were treated only on the HT unit, with the LIMRT plan serving as a backup in case the HT system might not be available. All plans were approved for clinical use by a physician. The prescription was that patients receive at least 95% of the planning target volume (PTV), which is 66 Gy at 2.2 Gy per fraction. Several dosimetric parameters were computed: PTV dose coverage; PTV volume conformity index; the normalized total dose (NTD), where doses were converted to 2 Gy per fraction to organs at risk (OAR); and PTV dose homogeneity. Both planning systems satisfied our clinic's PTV prescription requirements. The results suggest that HT plans had, in general, slightly better dosimetric characteristics, especially regarding PTV dose homogeneity and normal tissue sparing. However, for both techniques, doses to OAR were well below the currently accepted normal tissue tolerances. Consequently, factors other than the dosimetric parameters studied here may have to be considered when making a choice between IMRT techniques.

  6. Correlation of dosimetric parameters obtained with the analytical anisotropic algorithm and toxicity of chest chemoradiation in lung carcinoma

    SciTech Connect

    Cartier, Lysian; Auberdiac, Pierre; Khodri, Mustapha; Malkoun, Nadia; Chargari, Cyrus; Thorin, Julie; Melis, Adrien; Talabard, Jean-Noeel; Laroche, Guy de; Fournel, Pierre; Tiffet, Olivier; Schmitt, Thierry; and others

    2012-07-01

    The purpose of this study was to analyze and revisit toxicity related to chest chemoradiotherapy and to correlate these side effects with dosimetric parameters obtained using analytical anisotropic algorithm (AAA) in locally unresectable advanced lung cancer. We retrospectively analyzed data from 47 lung cancer patients between 2005 and 2008. All received conformal 3D radiotherapy using high-energy linear accelerator plus concomitant chemotherapy. All treatment planning data were transferred into Eclipse 8.05 (Varian Medical Systems, Palo Alto, CA) and dosimetric calculations were performed using AAA. Thirty-three patients (70.2%) developed acute pneumopathy after radiotherapy (grades 1 and 2). One patient (2.1%) presented with grade 3 pneumopathy. Thirty-one (66%) presented with grades 1-2 lung fibrosis, and 1 patient presented with grade 3 lung fibrosis. Thirty-four patients (72.3%) developed grade 1-2 acute oesophagic toxicity. Four patients (8.5%) presented with grades 3 and 4 dysphagia, necessitating prolonged parenteral nutrition. Median prescribed dose was 64 Gy (range 50-74) with conventional fractionation (2 Gy per fraction). Dose-volume constraints were respected with a median V20 of 23.5% (maximum 34%) and a median V30 of 17% (maximum 25%). The median dose delivered to healthy contralateral lung was 13.1 Gy (maximum 18.1 Gy). At univariate analysis, larger planning target volume and V20 were significantly associated with the probability of grade {>=}2 radiation-induced pneumopathy (p = 0.022 and p = 0.017, respectively). No relation between oesophagic toxicity and clinical/dosimetric parameters could be established. Using AAA, the present results confirm the predictive value of the V20 for lung toxicity as already demonstrated with the conventional pencil beam convolution approach.

  7. Individualized margins in 3D conformal radiotherapy planning for lung cancer: analysis of physiological movements and their dosimetric impacts.

    PubMed

    Germain, François; Beaulieu, Luc; Fortin, André

    2008-01-01

    In conformal radiotherapy planning for lung cancer, respiratory movements are not taken into account when a single computed tomography (CT) scan is performed. This study examines tumor movements to design individualized margins to account for these movements and evaluates their dosimetric impacts on planning volume. Fifteen patients undergoing CT-based planning for radical radiotherapy for localized lung cancer formed the study cohort. A reference plan was constructed based on reference gross, clinical, and planning target volumes (rGTV, rCTV, and rPTV, respectively). The reference plans were compared with individualized plans using individualized margins obtained by using 5 serial CT scans to generate individualized target volumes (iGTV, iCTV, and iPTV). Three-dimensional conformal radiation therapy was used for plan generation using 6- and 23-MV photon beams. Ten plans for each patient were generated and dose-volume histograms (DVHs) were calculated. Comparisons of volumetric and dosimetric parameters were performed using paired Student t-tests. Relative to the rGTV, the total volume occupied by the superimposed GTVs increased progressively with each additional CT scans. With the use of all 5 scans, the average increase in GTV was 52.1%. For the plans with closest dosimetric coverage, target volume was smaller (iPTV/rPTV ratio 0.808) but lung irradiation was only slightly decreased. Reduction in the proportion of lung tissue that received 20 Gy or more outside the PTV (V20) was observed both for 6-MV plans (-0.73%) and 23-MV plans (-0.65%), with p = 0.02 and p = 0.04, respectively. In conformal RT planning for the treatment of lung cancer, the use of serial CT scans to evaluate respiratory motion and to generate individualized margins to account for these motions produced only a limited lung sparing advantage.

  8. Individualized Margins in 3D Conformal Radiotherapy Planning for Lung Cancer: Analysis of Physiological Movements and Their Dosimetric Impacts

    SciTech Connect

    Germain, Francois Beaulieu, Luc; Fortin, Andre

    2008-04-01

    In conformal radiotherapy planning for lung cancer, respiratory movements are not taken into account when a single computed tomography (CT) scan is performed. This study examines tumor movements to design individualized margins to account for these movements and evaluates their dosimetric impacts on planning volume. Fifteen patients undergoing CT-based planning for radical radiotherapy for localized lung cancer formed the study cohort. A reference plan was constructed based on reference gross, clinical, and planning target volumes (rGTV, rCTV, and rPTV, respectively). The reference plans were compared with individualized plans using individualized margins obtained by using 5 serial CT scans to generate individualized target volumes (iGTV, iCTV, and iPTV). Three-dimensional conformal radiation therapy was used for plan generation using 6- and 23-MV photon beams. Ten plans for each patient were generated and dose-volume histograms (DVHs) were calculated. Comparisons of volumetric and dosimetric parameters were performed using paired Student t-tests. Relative to the rGTV, the total volume occupied by the superimposed GTVs increased progressively with each additional CT scans. With the use of all 5 scans, the average increase in GTV was 52.1%. For the plans with closest dosimetric coverage, target volume was smaller (iPTV/rPTV ratio 0.808) but lung irradiation was only slightly decreased. Reduction in the proportion of lung tissue that received 20 Gy or more outside the PTV (V20) was observed both for 6-MV plans (-0.73%) and 23-MV plans (-0.65%), with p = 0.02 and p = 0.04, respectively. In conformal RT planning for the treatment of lung cancer, the use of serial CT scans to evaluate respiratory motion and to generate individualized margins to account for these motions produced only a limited lung sparing advantage.

  9. Google Maps: You Are Here

    ERIC Educational Resources Information Center

    Jacobsen, Mikael

    2008-01-01

    Librarians use online mapping services such as Google Maps, MapQuest, Yahoo Maps, and others to check traffic conditions, find local businesses, and provide directions. However, few libraries are using one of Google Maps most outstanding applications, My Maps, for the creation of enhanced and interactive multimedia maps. My Maps is a simple and…

  10. Dosimetric experience with 2 commercially available multilumen balloon-based brachytherapy to deliver accelerated partial-breast irradiation

    SciTech Connect

    Fu, Weihua Kim, Jong Oh; Chen, Alex S.J.; Mehta, Kiran; Pucci, Pietro; Huq, M. Saiful

    2015-10-01

    The purpose of this work was to report dosimetric experience with 2 kinds of multilumen balloon (MLB), 5-lumen Contura MLB (C-MLB) and 4-lumen MammoSite MLB (MS-MLB), to deliver accelerated partial-breast irradiation, and compare the ability to achieve target coverage and control skin and rib doses between 2 groups of patients treated with C-MLB and MS-MLB brachytherapy. C-MLB has 5 lumens, the 4 equal-spaced peripheral lumens are 5 mm away from the central lumen. MS-MLB has 4 lumens, the 3 equal-spaced peripheral lumens are 3 mm away from the central lumen. In total, 43 patients were treated, 23 with C-MLB, and 20 with MS-MLB. For C-MLB group, 8 patients were treated with a skin spacing < 7 mm and 12 patients with rib spacing < 7 mm. For MS-MLB group, 2 patients were treated with a skin spacing < 7 mm and 5 patients with rib spacing < 7 mm. The dosimetric goals were (1) ≥ 95% of the prescription dose (PD) covering ≥ 95% of the target volume (V{sub 95%} ≥ 95%), (2) maximum skin dose ≤ 125% of the PD, (3) maximum rib dose ≤ 145% of the PD (if possible), and (4) the V{sub 150%} ≤ 50 cm{sup 3} and V{sub 200%} ≤ 10 cm{sup 3}. All dosimetric criteria were met concurrently in 82.6% of C-MLB patients, in 80.0% of MS-MLB patients, and in 81.4% of all 43 patients. For each dosimetric parameter, t-test of these 2 groups showed p > 0.05. Although the geometric design of C-MLB is different from that of MS-MLB, both applicators have the ability to shape the dose distribution and to provide good target coverage, while limiting the dose to skin and rib. No significant difference was observed between the 2 patient groups in terms of target dose coverage and dose to organs at risk.

  11. Dosimetric characterization of radionuclides for systemic tumor therapy: Influence of particle range, photon emission, and subcellular distribution

    SciTech Connect

    Uusijaervi, Helena; Bernhardt, Peter; Ericsson, Thomas; Forssell-Aronsson, Eva

    2006-09-15

    Various radionuclides have been proposed for systemic tumor therapy. However, in most dosimetric analysis of proposed radionuclides the charged particles are taken into consideration while the potential photons are ignored. The photons will cause undesirable irradiation of normal tissue, and increase the probability of toxicity in, e.g., the bone marrow. The aim of this study was to investigate the dosimetric properties according to particle range, photon emission, and subcellular radionuclide distribution, of a selection of radionuclides used or proposed for radionuclide therapy, and to investigate the possibility of dividing radionuclides into groups according to their dosimetric properties. The absorbed dose rate to the tumors divided by the absorbed dose rate to the normal tissue (TND) was estimated for different tumor sizes in a mathematical model of the human body. The body was simulated as a 70-kg ellipsoid and the tumors as spheres of different sizes (1 ng-100 g). The radionuclides were either assumed to be uniformly distributed throughout the entire tumor and normal tissue, or located in the nucleus or the cytoplasm of the tumor cells and on the cell membrane of the normal cells. Fifty-nine radionuclides were studied together with monoenergetic electrons, positrons, and alpha particles. The tumor and normal tissue were assumed to be of water density. The activity concentration ratio between the tumor and normal tissue was assumed to be 25. The radionuclides emitting low-energy electrons combined with a low photon contribution, and the alpha emitters showed high TND values for most tumor sizes. Electrons with higher energy gave reduced TND values for small tumors, while a higher photon contribution reduced the TND values for large tumors. Radionuclides with high photon contributions showed low TND value for all tumor sizes studied. The radionuclides studied could be divided into four main groups according to their TND values: beta emitters, Auger electron

  12. Dosimetric impact of cylinder size in high-dose rate vaginal cuff brachytherapy (VCBT) for primary endometrial cancer.

    PubMed

    Zhang, Hualin; Gopalakrishnan, Mahesh; Lee, Plato; Kang, Zhuang; Sathiaseelan, Vythialingam

    2016-01-01

    The purpose of this study was to evaluate the dosimetric impact of cylinder size in high-dose-rate (HDR) vaginal cuff brachytherapy (VCBT). Sample plans of HDR VCBT in a list of cylinders ranging from 2.5 to 4 cm in diameter at 0.5 cm incre-ment were created and analyzed. The doses were prescribed either at the 0.5cm depth with 5.5 Gy for 4 fractions or at the cylinder surface with 8.8 Gy for 4 frac-tions, in various treatment lengths. A 0.5 cm shell volume called PTV_Eval was contoured for each plan and served as the target volume for dosimetric evaluation. The cumulative and differential dose volume histograms (c-DVH and d-DVH), mean doses (D-mean) and the doses covering 90% (D90), 10% (D10), and 5% (D5) of PTV_Eval were calculated. In the 0.5 cm depth regimen, the DVH curves were found to have shifted toward the lower dose zone when a larger cylinder was used, but in the surface regimen the DVH curves shifted toward the higher dose zone as the cylinder size increased. The D-means of the both regimens were between 6.9 and 7.8 Gy and dependent on the cylinder size but independent of the treatment length. A 0.5 cm variation of diameter could result in a 4% change of D-mean. Average D90s were 5.7 (ranging from 5.6 to 5.8 Gy) and 6.1 Gy (from 5.7 to 6.4 Gy), respectively, for the 0.5 cm and surface regimens. Average D10 and D5 were 9.2 and 11 Gy, respectively, for the 0.5 cm depth regimen, and 8.9 and 9.7 Gy, respectively, for the surface regimen. D-mean, D90, D10, and D5 for other prescription doses could be calculated from the lookup tables of this study. Results indicated that the cylinder size has moderate dosimetric impact, and that both regimens are comparable in dosimetric quality. PMID:27685113

  13. Dosimetric and biological results from the Bacillus subtilis Biostack experiment with the Apollo-Soyuz Test Project.

    PubMed

    Facius, R; Bucker, H; Horneck, G; Reitz, G; Schafer, M

    1979-01-01

    The evaluation of the Bacillus subtilis experiment has been completed. The biological and the physical results for this part of the Apollo-Soyuz Test Project (ASTP) Biostack experiment are given. This comprises dosimetric data for the cosmic radiation at that orbit as well as biological findings from two types of plastic detectors. Further, the frequency distributions of the physical quantities atomic number, energy and energy loss of the heavy ions within the sample of spores hit are presented. The biological hazard presented by cosmic HZE-particles has been much underestimated.

  14. Evaluation of the dosimetric properties of a synthetic single crystal diamond detector in high energy clinical proton beams

    SciTech Connect

    Mandapaka, A. K.; Ghebremedhin, A.; Patyal, B.; Marinelli, Marco; Prestopino, G.; Verona, C.; Verona-Rinati, G.

    2013-12-15

    Purpose: To investigate the dosimetric properties of a synthetic single crystal diamond Schottky diode for accurate relative dose measurements in large and small field high-energy clinical proton beams.Methods: The dosimetric properties of a synthetic single crystal diamond detector were assessed by comparison with a reference Markus parallel plate ionization chamber, an Exradin A16 microionization chamber, and Exradin T1a ion chamber. The diamond detector was operated at zero bias voltage at all times. Comparative dose distribution measurements were performed by means of Fractional depth dose curves and lateral beam profiles in clinical proton beams of energies 155 and 250 MeV for a 14 cm square cerrobend aperture and 126 MeV for 3, 2, and 1 cm diameter circular brass collimators. ICRU Report No. 78 recommended beam parameters were used to compare fractional depth dose curves and beam profiles obtained using the diamond detector and the reference ionization chamber. Warm-up/stability of the detector response and linearity with dose were evaluated in a 250 MeV proton beam and dose rate dependence was evaluated in a 126 MeV proton beam. Stem effect and the azimuthal angle dependence of the diode response were also evaluated.Results: A maximum deviation in diamond detector signal from the average reading of less than 0.5% was found during the warm-up irradiation procedure. The detector response showed a good linear behavior as a function of dose with observed deviations below 0.5% over a dose range from 50 to 500 cGy. The detector response was dose rate independent, with deviations below 0.5% in the investigated dose rates ranging from 85 to 300 cGy/min. Stem effect and azimuthal angle dependence of the diode signal were within 0.5%. Fractional depth dose curves and lateral beam profiles obtained with the diamond detector were in good agreement with those measured using reference dosimeters.Conclusions: The observed dosimetric properties of the synthetic single

  15. Dosimetric comparison of two arc-based stereotactic body radiotherapy techniques for early-stage lung cancer

    SciTech Connect

    Liu, Huan Ye, Jingjing; Kim, John J.; Deng, Jun; Kaur, Monica S.; Chen, Zhe

    2015-04-01

    To compare the dosimetric and delivery characteristics of two arc-based stereotactic body radiotherapy (SBRT) techniques for early-stage lung cancer treatment. SBRT treatment plans for lung tumors of different sizes and locations were designed using a single-isocenter multisegment dynamic conformal arc technique (SiMs-arc) and a volumetric modulated arc therapy technique (RapidArc) for 5 representative patients treated previously with lung SBRT. The SiMs-arc plans were generated with the isocenter located in the geometric center of patient's axial plane (which allows for collision-free gantry rotation around the patient) and 6 contiguous 60° arc segments spanning from 1° to 359°. 2 RapidArc plans, one using the same arc geometry as the SiMs-arc and the other using typical partial arcs (210°) with the isocenter inside planning target volume (PTV), were generated for each corresponding SiMs-arc plan. All plans were generated using the Varian Eclipse treatment planning system (V10.0) and were normalized with PTV V{sub 100} to 95%. PTV coverage, dose to organs at risk, and total monitor units (MUs) were then compared and analyzed. For PTV coverage, the RapidArc plans generally produced higher PTV D{sub 99} (by 1.0% to 3.3%) and higher minimum dose (by 2.7% to 12.7%), better PTV conformality index (by 1% to 8%), and less volume of 50% dose outside 2 cm from PTV (by 0 to 20.8 cm{sup 3}) than the corresponding SiMs-arc plans. For normal tissues, no significant dose differences were observed for the lungs, trachea, chest wall, and heart; RapidArc using partial arcs produced lowest maximum dose to spinal cord. For dose delivery, the RapidArc plans typically required 50% to 90% more MUs than SiMs-arc plans to deliver the same prescribed dose. The additional intensity modulation afforded by variable gantry speed and dose rate and by overlapping arcs enabled RapidArc plans to produce dosimetrically improved plans for lung SBRT, but required more MUs (by a factor > 1.5) to

  16. Dosimetric experience with 2 commercially available multilumen balloon-based brachytherapy to deliver accelerated partial-breast irradiation.

    PubMed

    Fu, Weihua; Kim, Jong Oh; Chen, Alex S J; Mehta, Kiran; Pucci, Pietro; Huq, M Saiful

    2015-01-01

    The purpose of this work was to report dosimetric experience with 2 kinds of multilumen balloon (MLB), 5-lumen Contura MLB (C-MLB) and 4-lumen MammoSite MLB (MS-MLB), to deliver accelerated partial-breast irradiation, and compare the ability to achieve target coverage and control skin and rib doses between 2 groups of patients treated with C-MLB and MS-MLB brachytherapy. C-MLB has 5 lumens, the 4 equal-spaced peripheral lumens are 5 mm away from the central lumen. MS-MLB has 4 lumens, the 3 equal-spaced peripheral lumens are 3 mm away from the central lumen. In total, 43 patients were treated, 23 with C-MLB, and 20 with MS-MLB. For C-MLB group, 8 patients were treated with a skin spacing < 7 mm and 12 patients with rib spacing < 7 mm. For MS-MLB group, 2 patients were treated with a skin spacing < 7 mm and 5 patients with rib spacing < 7 mm. The dosimetric goals were (1) ≥ 95% of the prescription dose (PD) covering ≥ 95% of the target volume (V(95%) ≥ 95%), (2) maximum skin dose ≤ 125% of the PD, (3) maximum rib dose ≤ 145% of the PD (if possible), and (4) the V(150%) ≤ 50 cm(3) and V(200%) ≤ 10 cm(3). All dosimetric criteria were met concurrently in 82.6% of C-MLB patients, in 80.0% of MS-MLB patients, and in 81.4% of all 43 patients. For each dosimetric parameter, t-test of these 2 groups showed p > 0.05. Although the geometric design of C-MLB is different from that of MS-MLB, both applicators have the ability to shape the dose distribution and to provide good target coverage, while limiting the dose to skin and rib. No significant difference was observed between the 2 patient groups in terms of target dose coverage and dose to organs at risk.

  17. Dosimetric and biological results from the Bacillus subtilis Biostack experiment with the Apollo-Soyuz Test Project.

    PubMed

    Facius, R; Bucker, H; Horneck, G; Reitz, G; Schafer, M

    1979-01-01

    The evaluation of the Bacillus subtilis experiment has been completed. The biological and the physical results for this part of the Apollo-Soyuz Test Project (ASTP) Biostack experiment are given. This comprises dosimetric data for the cosmic radiation at that orbit as well as biological findings from two types of plastic detectors. Further, the frequency distributions of the physical quantities atomic number, energy and energy loss of the heavy ions within the sample of spores hit are presented. The biological hazard presented by cosmic HZE-particles has been much underestimated. PMID:12001965

  18. Map reading tools for map libraries.

    USGS Publications Warehouse

    Greenberg, G.L.

    1982-01-01

    Engineers, navigators and military strategists employ a broad array of mechanical devices to facilitate map use. A larger number of map users such as educators, students, tourists, journalists, historians, politicians, economists and librarians are unaware of the available variety of tools which can be used with maps to increase the speed and efficiency of their application and interpretation. This paper identifies map reading tools such as coordinate readers, protractors, dividers, planimeters, and symbol-templets according to a functional classification. Particularly, arrays of tools are suggested for use in determining position, direction, distance, area and form (perimeter-shape-pattern-relief). -from Author

  19. Mapping the Future of Map Librarianship.

    ERIC Educational Resources Information Center

    Lang, Laura

    1992-01-01

    Discussion of electronic versions of maps focuses on TIGER files (i.e., electronic maps distributed by the U.S. Bureau of the Census) and their manipulation using geographic information system (GIS) technology. Topics addressed include applications of GIS software, projects to improve access to TIGER files, and the role of GIS in libraries. (MES)

  20. Mapping Human Epigenomes

    PubMed Central

    Rivera, Chloe M.; Ren, Bing

    2013-01-01

    As the second dimension to the genome, the epigenome contains key information specific to every type of cells. Thousands of human epigenome maps have been produced in recent years thanks to rapid development of high throughput epigenome mapping technologies. In this review, we discuss the current epigenome mapping toolkit and utilities of epigenome maps. We focus particularly on mapping of DNA methylation, chromatin modification state and chromatin structures, and emphasize the use of epigenome maps to delineate human gene regulatory sequences and developmental programs. We also provide a perspective on the progress of the epigenomics field and challenges ahead. PMID:24074860

  1. Density Equalizing Map Projections

    1995-07-01

    A geographic map is mathematically transformed so that the subareas of the map are proportional to a given quantity such as population. In other words, population density is equalized over the entire map. The transformed map can be used as a display tool, or it can be statistically analyzed. For example, cases of disease plotted on the transformed map should be uniformly distributed at random, if disease rates are everywhere equal. Geographic clusters of diseasemore » can be readily identified, and their statistical significance determined, on a density equalized map.« less

  2. Dosimetric comparison of four new design {sup 103}Pd brachytherapy sources: Optimal design using silver and copper rod cores

    SciTech Connect

    Hosseini, S. Hamed; Sadeghi, Mahdi; Ataeinia, Vahideh

    2009-07-15

    Four new brachytherapy sources, IRA1-{sup 103}Pd, IRA2-{sup 103}Pd, IRA3-{sup 103}Pd, and IRA4-{sup 103}Pd, have been developed at Agricultural, Medical, and Industrial Research School and are designed for permanent implant application. With the goal of determining an optimal design for a {sup 103}Pd source, this article compares the dosimetric properties of these sources with reference to the authors' earlier IRA-{sup 103}Pd source. The four new sources differ in end cap configuration and thickness and in the core material, silver or copper, that carries the adsorbed {sup 103}Pd. Dosimetric data derived from the authors' Monte Carlo simulation results are reported in accordance with the updated AAPM Task Group No. 43 report (TG-43U1). For each source, the authors obtained detailed results for the dose rate constant {Lambda}, the radial dose function g(r), the anisotropy function F(r,{theta}), and the anisotropy factor {phi}{sub an}(r). In this study, the optimal source IRA3-{sup 103}Pd provides the most isotropic dose distribution in water with the dose rate constant of 0.678({+-}0.1%) cGy h{sup -1} U{sup -1}. The IRA3-{sup 103}Pd design has a silver rod core combined with thin-wall, concave end caps. Finally, the authors compared the results for their optimal source with published results for those of other source manufacturers.

  3. Three-dimensional spatial and dosimetric characterization of radiotherapy beams using laser read-out of TLDs

    SciTech Connect

    Grupen-Shemansky, M.E.

    1989-01-01

    A fully automated thermoluminescent detector (TLD) read-out apparatus has been designed and constructed for the express purpose of extracting spatially resolved dosimetric information using localized IR laser phosphor stimulation. A composite TLD plate has been designed that withstands the thermal stresses developed during laser heating. This detector and unique read-out scheme may be used to spatially and dosimetrically characterize ionizing radiation fields. The thermal response of TL materials cannot be fully characterized experimentally due to the inability of modern measuring techniques to accurately record the rapidly changing temperatures. Two-dimensional, time transient models have been derived to determine radial and axial temperature profiles in a TL layer when a 4 W CO{sub 2} focused or unfocused Gaussian laser beam is used to heat a single or multiple spots. Numerically derived temperature profiles were then used in a first-order kinetic model for the thermoluminescent emission. The experimental laser heated TLD read-out apparatus was used to image a {sup 60}Co radiotherapy beam. A 2.2 cm by 3.3 cm LiF detector was used to image the penumbra of a 5 cm by 5 cm collimated field of a Theratron-80. Qualitative and quantitative results agreed well with accepted beam depth dose profiles measured with ionization chambers in water bath phantoms.

  4. Dosimetric comparisons of VMAT, IMRT and 3DCRT for locally advanced rectal cancer with simultaneous integrated boost

    PubMed Central

    Cai, Gang; Wang, Jiazhou; Xie, Jiang; Peng, Jiayuan; Zhang, Zhen

    2016-01-01

    The simultaneous integrated boost radiotherapy for preoperative locally advanced rectal cancer (LARC) can improve the local control and overall survival rates. The purpose of this study is to compare the dosimetric differences among volumetric modulated arc therapy (VMAT), fixed-field intensity modulated radiotherapy (IMRT) and three-dimensional conformal radiotherapy (3DCRT) for the LARC. Ten LARC patients treated in our department using the simultaneous escalate strategy were retrospectively analyzed in this study. All patients had T3 with N+/− and were treated with IMRT. Two additional VMAT and 3DCRT plans were created for each patient. VMAT plans were designed using SmartArc planning module. Both IMRT and SmartArc had similar optimization objectives. The prescription was 50 Gy to the planning clinical target volume (PTV-C) and 56 Gy to the planning gross target volume (PTV-G). The target coverage and organs at risk (OARs) were compared for all the techniques. The paired, two-tailed Wilcoxon signed-rank test was applied for statistical analysis. Results of this study indicate that IMRT and SmartArc were all significantly superior to 3DCRT in most of the relevant values evaluated of target response, OARs and normal tissue sparing. They provided comparable dosimetric parameters for target volume. But IMRT shows better sparing for OARs and normal tissue. PMID:26621840

  5. Dosimetric impact of interplay effect in lung IMRT and VMAT treatment using in-house dynamic thorax phantom

    NASA Astrophysics Data System (ADS)

    Mukhlisin; Pawiro, S. A.

    2016-03-01

    Tumor motion due to patient's respiratory is a significant problem in radiotherapy treatment of lung cancer. The purpose of this project is to study the interplay effect through dosimetry verification between the calculated and delivered dose, as well as the dosimetric impact of leaf interplay with breathing-induced tumor motion in IMRT and VMAT treatment. In this study, a dynamic thorax phantom was designed and constructed for dosimetry measurement. The phantom had a linear sinusoidal tumor motion toward superior-inferior direction with variation of amplitudes and periods. TLD-100 LiF:Mg,Ti and Gafchromic EBT2 film were used to measure dose in the midpoint target and the spinal cord. The IMRT and VMAT treatment had prescription dose of 200 cGy per fraction. The dosimetric impact due to interplay effect during IMRT and VMAT treatment were resulted in the range of 0.5% to -6.6% and 0.9% to -5.3% of target dose reduction, respectively. Meanwhile, mean dose deviation of spinal cord in IMRT and VMAT treatment were around 1.0% to -6.9% and 0.9% to -6.3%, respectively. The results showed that if respiratory management technique were not implemented, the presence of lung tumor motion during dose delivery in IMRT and VMAT treatment causes dose discrepancies inside tumor volume.

  6. Dosimetric comparisons of VMAT, IMRT and 3DCRT for locally advanced rectal cancer with simultaneous integrated boost.

    PubMed

    Zhao, Jun; Hu, Weigang; Cai, Gang; Wang, Jiazhou; Xie, Jiang; Peng, Jiayuan; Zhang, Zhen

    2016-02-01

    The simultaneous integrated boost radiotherapy for preoperative locally advanced rectal cancer (LARC) can improve the local control and overall survival rates. The purpose of this study is to compare the dosimetric differences among volumetric modulated arc therapy (VMAT), fixed-field intensity modulated radiotherapy (IMRT) and three-dimensional conformal radiotherapy (3DCRT) for the LARC. Ten LARC patients treated in our department using the simultaneous escalate strategy were retrospectively analyzed in this study. All patients had T3 with N+/- and were treated with IMRT. Two additional VMAT and 3DCRT plans were created for each patient. VMAT plans were designed using SmartArc planning module. Both IMRT and SmartArc had similar optimization objectives. The prescription was 50 Gy to the planning clinical target volume (PTV-C) and 56 Gy to the planning gross target volume (PTV-G). The target coverage and organs at risk (OARs) were compared for all the techniques. The paired, two-tailed Wilcoxon signed-rank test was applied for statistical analysis. Results of this study indicate that IMRT and SmartArc were all significantly superior to 3DCRT in most of the relevant values evaluated of target response, OARs and normal tissue sparing. They provided comparable dosimetric parameters for target volume. But IMRT shows better sparing for OARs and normal tissue.

  7. Evaluating the effect of various intracavitary applicators on dosimetric parameters of (192)Ir, (137)Cs, and (60)Co sources.

    PubMed

    Ghorbani, Mahdi; Hashempour, Marjan; Azizi, Mona; Meigooni, Ali S

    2016-06-01

    The purpose of this research is to study the effect of various applicator compositions on dosimetric parameters and dose distribution of (192)Ir, (137)Cs, and (60)Co sources, using Monte Carlo simulation techniques. To study the effect of applicators on source dosimetry, the dose rate constant, and radial dose function and isodose curves for the above noted sources were calculated in the presence and absence of plastic, titanium, and a stainless steel applicators. The effects of the applicators on the dosimetric parameters and isodose curves of these sources were dependent of the source type and materials of the applicator. The (192)Ir source with the stainless steel applicator has the maximum difference of dose rate (4.2 %) relative to the without applicator case. The (60)Co source with plastic applicator has the minimum dose variation. Moreover, this effect is higher for lower energy sources. Ignoring the effect of applicator composition and geometry on dose distribution may cause discrepancies in treatment planning. Plastic applicators have the least radiation attenuation compared to the other applicators, therefore, they are recommended for use in brachytherapy. A table of correction factors has been introduced for different sources and applicators with different materials for the clinical applications.

  8. A breathing thorax phantom with independently programmable 6D tumour motion for dosimetric measurements in radiation therapy

    NASA Astrophysics Data System (ADS)

    Steidl, P.; Richter, D.; Schuy, C.; Schubert, E.; Haberer, Th; Durante, M.; Bert, C.

    2012-04-01

    Irradiation of moving targets using a scanned ion beam can cause clinically intolerable under- and overdosages within the target volume due to the interplay effect. Several motion mitigation techniques such as gating, beam tracking and rescanning are currently investigated to overcome this restriction. To enable detailed experimental studies of potential mitigation techniques a complex thorax phantom was developed. The phantom consists of an artificial thorax with ribs to introduce density changes. The contraction of the thorax can be controlled by a stepping motor. A robotic driven detector head positioned inside the thorax mimics e.g. a lung tumour. The detector head comprises 20 ionization chambers and 5 radiographic films for target dose measurements. The phantom’s breathing as well as the 6D tumour motion (3D translation, 3D rotation) can be programmed independently and adjusted online. This flexibility allows studying the dosimetric effects of correlation mismatches between internal and external motions, irregular breathing, or baseline drifts to name a few. Commercial motion detection systems, e.g. VisionRT or Anzai belt, can be mounted as they would be mounted in a patient case. They are used to control the 4D treatment delivery and to generate data for 4D dose calculation. To evaluate the phantom’s properties, measurements addressing reproducibility, stability, temporal behaviour and performance of dedicated breathing manoeuvres were performed. In addition, initial dosimetric tests for treatment with a scanned carbon beam are reported.

  9. Dosimetric differences between intraoperative and postoperative plans using Cs-131 in transrectal ultrasound–guided brachytherapy for prostatic carcinoma

    SciTech Connect

    Jones, Andrew; Treas, Jared; Yavoich, Brian; Dean, Douglas; Danella, John; Yumen, Omar

    2014-01-01

    The aim of the study was to investigate the differences between intraoperative and postoperative dosimetry for transrectal ultrasound–guided transperineal prostate implants using cesium-131 ({sup 131}Cs). Between 2006 and 2010, 166 patients implanted with {sup 131}Cs had both intraoperative and postoperative dosimetry studies. All cases were monotherapy and doses of 115 were prescribed to the prostate. The dosimetric properties (D{sub 90}, V{sub 150}, and V{sub 100} for the prostate) of the studies were compared. Two conformity indices were also calculated and compared. Finally, the prostate was automatically sectioned into 6 sectors (anterior and posterior sectors at the base, midgland, and apex) and the intraoperative and postoperative dosimetry was compared in each individual sector. Postoperative dosimetry showed statistically significant changes (p < 0.01) in every dosimetric value except V{sub 150}. In each significant case, the postoperative plans showed lower dose coverage. The conformity indexes also showed a bimodal frequency distribution with the index indicating poorer dose conformity in the postoperative plans. Sector analysis revealed less dose coverage postoperatively in the base and apex sectors with an increase in dose to the posterior midgland sector. Postoperative dosimetry overall and in specific sectors of the prostate differs significantly from intraoperative planning. Care must be taken during the intraoperative planning stage to ensure complete dose coverage of the prostate with the understanding that the final postoperative dosimetry will show less dose coverage.

  10. Dosimetric impact of applicator displacement during high dose rate (HDR) Cobalt-60 brachytherapy for cervical cancer: A planning study

    NASA Astrophysics Data System (ADS)

    Yong, J. S.; Ung, N. M.; Jamalludin, Z.; Malik, R. A.; Wong, J. H. D.; Liew, Y. M.; Ng, K. H.

    2016-02-01

    We investigated the dosimetric impact of applicator displacement on dose specification during high dose rate (HDR) Cobalt-60 (Co-60) brachytherapy for cervical cancer through a planning study. Eighteen randomly selected HDR full insertion plans were restrospectively studied. The tandem and ovoids were virtually shifted translationally and rotationally in the x-, y- and z-axis directions on the treatment planning system. Doses to reference points and volumes of interest in the plans with shifted applicators were compared with the original plans. The impact of dose displacement on 2D (point-based) and 3D (volume-based) treatment planning techniques was also assessed. A ±2 mm translational y-axis applicator shift and ±4° rotational x-axis applicator shift resulted in dosimetric changes of more than 5% to organs at risk (OAR) reference points. Changes to the maximum doses to 2 cc of the organ (D2cc) in 3D planning were statistically significant and higher than the reference points in 2D planning for both the rectum and bladder (p<0.05). Rectal D2cc was observed to be the most sensitive to applicator displacement among all dose metrics. Applicator displacement that is greater than ±2 mm translational y-axis and ±4° rotational x-axis resulted in significant dose changes to the OAR. Thus, steps must be taken to minimize the possibility of applicator displacement during brachytherapy.

  11. Commissioning and dosimetric characteristics of TrueBeam system: Composite data of three TrueBeam machines

    SciTech Connect

    Chang Zheng; Wu Qiuwen; Adamson, Justus; Ren Lei; Bowsher, James; Yan Hui; Thomas, Andrew; Yin Fangfang

    2012-11-15

    Purpose: A TrueBeam linear accelerator (TB-LINAC) is designed to deliver traditionally flattened and flattening-filter-free (FFF) beams. Although it has been widely adopted in many clinics for patient treatment, limited information is available related to commissioning of this type of machine. In this work, commissioning data of three units were measured, and multiunit comparison was presented to provide valuable insights and reliable evaluations on the characteristics of the new treatment system. Methods: The TB-LINAC is equipped with newly designed waveguide, carousel assembly, monitoring control, and integrated imaging systems. Each machine in this study has 4, 6, 8, 10, 15 MV flattened photon beams, and 6 MV and 10 MV FFF photon beams as well as 6, 9, 12, 16, 20, and 22 MeV electron beams. Dosimetric characteristics of the three new TB-LINAC treatment units are systematically measured for commissioning. High-resolution diode detectors and ion chambers were used to measure dosimetric data for a range of field sizes from 10 Multiplication-Sign 10 to 400 Multiplication-Sign 400 mm{sup 2}. The composite dosimetric data of the three units are presented in this work. The commissioning of intensity modulated radiotherapy (IMRT), volumetric modulated arc therapy (VMAT), image-guided radiation therapy, and gating systems are also illustrated. Critical considerations of P{sub ion} of FFF photon beams and small field dosimetric measurements were investigated. Results: The authors found all PDDs and profiles matched well among the three machines. Beam data were quantitatively compared and combined through average to yield composite beam data. The discrepancies among the machines were quantified using standard deviation (SD). The mean SD of the PDDs among the three units is 0.12%, and the mean SD of the profiles is 0.40% for 10 MV FFF open fields. The variations of P{sub ion} of the chamber CC13 is 1.2 {+-} 0.1% under 6 MV FFF and 2.0 {+-} 0.5% under 10 MV FFF from dmax to

  12. Postoperative intensity modulated radiation therapy in high risk prostate cancer: a dosimetric comparison.

    PubMed

    Digesú, Cinzia; Cilla, Savino; De Gaetano, Andrea; Massaccesi, Mariangela; Macchia, Gabriella; Ippolito, Edy; Deodato, Francesco; Panunzi, Simona; Iapalucci, Chiara; Mattiucci, Gian Carlo; D'Angelo, Elisa; Padula, Gilbert D A; Valentini, Vincenzo; Cellini, Numa; Piermattei, Angelo; Morganti, Alessio G

    2011-01-01

    The aim of this study was to compare intensity-modulated radiation therapy (IMRT) with 3D conformal technique (3D-CRT), with respect to target coverage and irradiation of organs at risk for high dose postoperative radiotherapy (PORT) of the prostate fossa. 3D-CRT and IMRT treatment plans were compared with respect to dose to the rectum and bladder. The dosimetric comparison was carried out in 15 patients considering 2 different scenarios: (1) exclusive prostate fossa irradiation, and (2) pelvic node irradiation followed by a boost on the prostate fossa. In scenario (1), a 3D-CRT plan (box technique) and an IMRT plan were calculated and compared for each patient. In scenario (2), 3 treatment plans were calculated and compared for each patient: (a) 3D-CRT box technique for both pelvic (prophylactic nodal irradiation) and prostate fossa irradiation (3D-CRT only); (b) 3D-CRT box technique for pelvic irradiation followed by an IMRT boost to the prostatic fossa (hybrid 3D-CRT and IMRT); and (c) IMRT for both pelvic and prostate fossa irradiation (IMRT only). For exclusive prostate fossa irradiation, IMRT significantly reduced the dose to the rectum (lower Dmean, V50%, V75%, V90%, V100%, EUD, and NTCP) and the bladder (lower Dmean, V50%, V90%, EUD and NTCP). When prophylactic irradiation of the pelvis was also considered, plan C (IMRT only) performed better than plan B (hybrid 3D-CRT and IMRT) as respect to both rectum and bladder irradiation (reduction of Dmean, V50%, V75%, V90%, equivalent uniform dose [EUD], and normal tissue complication probability [NTCP]). Plan (b) (hybrid 3D-CRT and IMRT) performed better than plan (a) (3D-CRT only) with respect to dose to the rectum (lower Dmean, V75%, V90%, V100%, EUD, and NTCP) and the bladder (Dmean, EUD, and NTCP). Postoperative IMRT in prostate cancer significantly reduces rectum and bladder irradiation compared with 3D-CRT.

  13. Evaluation of the dosimetric properties of a diode detector for small field proton radiosurgery.

    PubMed

    McAuley, Grant A; Teran, Anthony V; Slater, Jerry D; Slater, James M; Wroe, Andrew J

    2015-11-08

    The small fields and sharp gradients typically encountered in proton radiosurgery require high spatial resolution dosimetric measurements, especially below 1-2 cm diameters. Radiochromic film provides high resolution, but requires postprocessing and special handling. Promising alternatives are diode detectors with small sensitive volumes (SV) that are capable of high resolution and real-time dose acquisition. In this study we evaluated the PTW PR60020 proton dosimetry diode using radiation fields and beam energies relevant to radiosurgery applications. Energies of 127 and 157 MeV (9.7 to 15 cm range) and initial diameters of 8, 10, 12, and 20mm were delivered using single-stage scattering and four modulations (0, 15, 30, and 60mm) to a water tank in our treatment room. Depth dose and beam profile data were compared with PTW Markus N23343 ionization chamber, EBT2 Gafchromic film, and Monte Carlo simulations. Transverse dose profiles were measured using the diode in "edge-on" orientation or EBT2 film. Diode response was linear with respect to dose, uniform with dose rate, and showed an orientation-dependent (i.e., beam parallel to, or perpendicular to, detector axis) response of less than 1%. Diodevs. Markus depth-dose profiles, as well as Markus relative dose ratio vs. simulated dose-weighted average lineal energy plots, suggest that any LET-dependent diode response is negligible from particle entrance up to the very distal portion of the SOBP for the energies tested. Finally, while not possible with the ionization chamber due to partial volume effects, accurate diode depth-dose measurements of 8, 10, and 12 mm diameter beams were obtained compared to Monte Carlo simulations. Because of the small SV that allows measurements without partial volume effects and the capability of submillimeter resolution (in edge-on orientation) that is crucial for small fields and high-dose gradients (e.g., penumbra, distal edge), as well as negligible LET dependence over nearly the

  14. TH-A-9A-03: Dosimetric Effect of Rotational Errors for Lung Stereotactic Body Radiotherapy

    SciTech Connect

    Lee, J; Kim, H; Park, J; Kim, J; Kim, H; Ye, S

    2014-06-15

    Purpose: To evaluate the dosimetric effects on target volume and organs at risk (OARs) due to roll rotational errors in treatment setup of stereotactic body radiation therapy (SBRT) for lung cancer. Methods: There were a total of 23 volumetric modulated arc therapy (VMAT) plans for lung SBRT examined in this retrospective study. Each CT image of VMAT plans was intentionally rotated by ±1°, ±2°, and ±3° to simulate roll rotational setup errors. The axis of rotation was set at the center of T-spine. The target volume and OARs in the rotated CT images were re-defined by deformable registration of original contours. The dose distributions on each set of rotated images were re-calculated to cover the planning target volume (PTV) with the prescription dose before and after the couch translational correction. The dose-volumetric changes of PTVs and spinal cords were analyzed. Results: The differences in D95% of PTVs by −3°, −2°, −1°, 1°, 2°, and 3° roll rotations before the couch translational correction were on average −11.3±11.4%, −5.46±7.24%, −1.11±1.38% −3.34±3.97%, −9.64±10.3%, and −16.3±14.7%, respectively. After the couch translational correction, those values were −0.195±0.544%, −0.159±0.391%, −0.188±0.262%, −0.310±0.270%, −0.407±0.331%, and −0.433±0.401%, respectively. The maximum dose difference of spinal cord among the 23 plans even after the couch translational correction was 25.9% at −3° rotation. Conclusions: Roll rotational setup errors in lung SBRT significantly influenced the coverage of target volume using VMAT technique. This could be in part compensated by the translational couch correction. However, in spite of the translational correction, the delivered doses to the spinal cord could be more than the calculated doses. Therefore if rotational setup errors exist during lung SBRT using VMAT technique, the rotational correction would rather be considered to prevent over-irradiation of normal

  15. SU-E-T-135: Dosimetric Properties of the OCTAVIUS Detector 1500

    SciTech Connect

    Stelljes, T; Looe, H; Chofor, N; Poppe, B; Harmeyer, A; Reuter, J; Harder, D

    2014-06-01

    Purpose: In this study the dosimetric properties of the Octavius Detector 1500 array (PTW-Freiburg-Germany) are investigated. Methods: The chambers of the array, each with an entrance window of 4.4 × 4.4 cm{sup 2}, are arranged in a checkerboard pattern in a measurement area of 27 × 27 cm{sup 2} with a sampling frequency of 0.1 mm{sup −1} along each row which can be doubled by merging two measurements shifted by 5 mm. Linearity, stability and output factors were measured with either a Semiflex 31013 or 31010 as a reference detector. Output factors were additionally measured with a Diode 60012. The effective point of measurement was determined by comparing TPR curves of the array with Roos chamber 34001 measurements. The lateral dose response function of a single chamber was determined by comparison with a high resolution diode. An IMRT field verification was carried out with a merged OD1500 measurement. Results: The OD1500 was stable within ±0.15 %. Deviations in linearity did not exceed 1% from 5 to 1000 MU. The effective point of measurement was 8.2 mm below the surface. Deviations in output factors were below 0.77 % from 5 × 5 to 27 × 27 cm{sup 2}. As expected for the smallest field of 1 × 1 cm{sup 2}, the deviation from the diode was significant. The widths of the lateral dose response functions were σ{sup 6} = (2.07 ± 0.03) mm and σ{sup 15} = (2.09 ± 0.03) mm. Gamma Index passing rates for typical IMRT and VMAT plans were above 90 % compared to film and TPS calculations for a local 3 mm / 3 % criterion. Conclusion: The first measurements with the OD1500 array show the excellent applicability of the array for clinical dosimetry. The response of the array to the mean photon energy and dose per pulse are under investigation.

  16. Model-based versus specific dosimetry in diagnostic context: Comparison of three dosimetric approaches

    SciTech Connect

    Marcatili, S. Villoing, D.; Mauxion, T.; Bardiès, M.; McParland, B. J.

    2015-03-15

    Purpose: The dosimetric assessment of novel radiotracers represents a legal requirement in most countries. While the techniques for the computation of internal absorbed dose in a therapeutic context have made huge progresses in recent years, in a diagnostic scenario the absorbed dose is usually extracted from model-based lookup tables, most often derived from International Commission on Radiological Protection (ICRP) or Medical Internal Radiation Dose (MIRD) Committee models. The level of approximation introduced by these models may impact the resulting dosimetry. The aim of this work is to establish whether a more refined approach to dosimetry can be implemented in nuclear medicine diagnostics, by analyzing a specific case. Methods: The authors calculated absorbed doses to various organs in six healthy volunteers administered with flutemetamol ({sup 18}F) injection. Each patient underwent from 8 to 10 whole body 3D PET/CT scans. This dataset was analyzed using a Monte Carlo (MC) application developed in-house using the toolkit GATE that is capable to take into account patient-specific anatomy and radiotracer distribution at the voxel level. They compared the absorbed doses obtained with GATE to those calculated with two commercially available software: OLINDA/EXM and STRATOS implementing a dose voxel kernel convolution approach. Results: Absorbed doses calculated with GATE were higher than those calculated with OLINDA. The average ratio between GATE absorbed doses and OLINDA’s was 1.38 ± 0.34 σ (from 0.93 to 2.23). The discrepancy was particularly high for the thyroid, with an average GATE/OLINDA ratio of 1.97 ± 0.83 σ for the six patients. Differences between STRATOS and GATE were found to be higher. The average ratio between GATE and STRATOS absorbed doses was 2.51 ± 1.21 σ (from 1.09 to 6.06). Conclusions: This study demonstrates how the choice of the absorbed dose calculation algorithm may introduce a bias when gamma radiations are of importance, as is

  17. SU-E-J-56: Dosimetric Impact of Patient Roll Variability in Peripheral-Lung SBRT

    SciTech Connect

    Casto, B; Ying, J; Ku, L

    2014-06-01

    Purpose: Positional variation about the patient longitudinal axis may introduce deleterious effects to clinical treatment plans, the effects of which are exacerbated by hypo-fractionated treatment regimens. Our goal is to evaluate the dosimetric impact of rotational setup error in stereotactic body radiation therapy (SBRT) for peripherally-located lung lesions. Methods: Six patients who had been treated for peripheral lung lesions using varying SBRT techniques were analyzed. Each patient's planning CT was processed using custom in-house software to simulate 1, 3, and 5 degree roll in both directions about their longitudinal axis. The original plan was fused and re-calculated. Agreement between planned and error-simulated dose distributions was quantified using 3%, 3mm criteria for the 3-dimensional gamma metric, and changes in target coverage and adjacent normal anatomy were also quantified. Results: Increased rotational setup error resulted in reduced target coverage, with changes in equivalent uniform dose ranging from −1.24% to −6.11% for simulated roll greater than or equal to 3 degrees, increasing with magnitude of error and skewed for roll directed toward the involved side. Changes to normal tissue metrics are linearly related to simulated roll, with rib D(1cc) changes ranging from −4.23% to 3.27% relative to the original treatment plan. Error-simulated dose distributions demonstrate agreement by the gamma metric in the planned target of 72.56%, 81.02%, and 99.52% for 5, 3, and 1 degree simulated roll scenarios, respectively. Corresponding agreement for the regional dose in excess of 50% of the maximum were 65.71%,70.77%, and 97.88%. Conclusion: This study suggests that the ability to detect and compensate for rotational positioning variations beyond a threshold level may improve care for patients with peripherally-located lesions beyond that which may be accomplished using only translational axes. Positional error of one degree of roll had little

  18. Dosimetric evaluation of new approaches in GRID therapy using nonconventional radiation sources

    SciTech Connect

    Martínez-Rovira, I. Prezado, Y.; Fois, G.

    2015-02-15

    Purpose: Spatial fractionation of the dose has proven to be a promising approach to increase the tolerance of healthy tissue, which is the main limitation of radiotherapy. A good example of that is GRID therapy, which has been successfully used in the management of large tumors with low toxicity. The aim of this work is to explore new avenues using nonconventional sources: GRID therapy by using kilovoltage (synchrotron) x-rays, the use of very high-energy electrons, and proton GRID therapy. They share in common the use of the smallest possible grid sizes in order to exploit the dose–volume effects. Methods: Monte Carlo simulations (PENELOPE/PENEASY and GEANT4/GATE codes) were used as a method to study dose distributions resulting from irradiations in different configurations of the three proposed techniques. As figure of merit, percentage (peak and valley) depth dose curves, penumbras, and central peak-to-valley dose ratios (PVDR) were evaluated. As shown in previous biological experiments, high PVDR values are requested for healthy tissue sparing. A superior tumor control may benefit from a lower PVDR. Results: High PVDR values were obtained in the healthy tissue for the three cases studied. When low energy photons are used, the treatment of deep-seated tumors can still be performed with submillimetric grid sizes. Superior PVDR values were reached with the other two approaches in the first centimeters along the beam path. The use of protons has the advantage of delivering a uniform dose distribution in the tumor, while healthy tissue benefits from the spatial fractionation of the dose. In the three evaluated techniques, there is a net reduction in penumbra with respect to radiosurgery. Conclusions: The high PVDR values in the healthy tissue and the use of small grid sizes in the three presented approaches might constitute a promising alternative to treat tumors with such spatially fractionated radiotherapy techniques. The dosimetric results presented here

  19. Dosimetric characterization and output verification for conical brachytherapy surface applicators. Part I. Electronic brachytherapy source

    SciTech Connect

    Fulkerson, Regina K. Micka, John A.; DeWerd, Larry A.

    2014-02-15

    Purpose: Historically, treatment of malignant surface lesions has been achieved with linear accelerator based electron beams or superficial x-ray beams. Recent developments in the field of brachytherapy now allow for the treatment of surface lesions with specialized conical applicators placed directly on the lesion. Applicators are available for use with high dose rate (HDR){sup 192}Ir sources, as well as electronic brachytherapy sources. Part I of this paper will discuss the applicators used with electronic brachytherapy sources; Part II will discuss those used with HDR {sup 192}Ir sources. Although the use of these applicators has gained in popularity, the dosimetric characteristics including depth dose and surface dose distributions have not been independently verified. Additionally, there is no recognized method of output verification for quality assurance procedures with applicators like these. Existing dosimetry protocols available from the AAPM bookend the cross-over characteristics of a traditional brachytherapy source (as described by Task Group 43) being implemented as a low-energy superficial x-ray beam (as described by Task Group 61) as observed with the surface applicators of interest. Methods: This work aims to create a cohesive method of output verification that can be used to determine the dose at the treatment surface as part of a quality assurance/commissioning process for surface applicators used with HDR electronic brachytherapy sources (Part I) and{sup 192}Ir sources (Part II). Air-kerma rate measurements for the electronic brachytherapy sources were completed with an Attix Free-Air Chamber, as well as several models of small-volume ionization chambers to obtain an air-kerma rate at the treatment surface for each applicator. Correction factors were calculated using MCNP5 and EGSnrc Monte Carlo codes in order to determine an applicator-specific absorbed dose to water at the treatment surface from the measured air-kerma rate. Additionally

  20. Dosimetric evaluation of three adaptive strategies for prostate cancer treatment including pelvic lymph nodes irradiation

    SciTech Connect

    Cantin, Audrey; Gingras, Luc; Archambault, Louis; Lachance, Bernard; Foster, William; Goudreault, Julie

    2015-12-15

    Purpose: The movements of the prostate relative to the pelvic lymph nodes during intensity-modulated radiation therapy treatment can limit margin reduction and affect the protection of the organs at risk (OAR). In this study, the authors performed an analysis of three adaptive treatment strategies that combine information from both bony and gold marker registrations. The robustness of those treatments against the interfraction prostate movements was evaluated. Methods: A retrospective study was conducted on five prostate cancer patients with 7–13 daily cone-beam CTs (CBCTs). The clinical target volumes (CTVs) consisting of pelvic lymph nodes, prostate, and seminal vesicles as well as the OARs were delineated on each CBCT and the initial CT. Three adaptive strategies were analyzed. Two of these methods relied on a two-step patient positioning at each fraction. First step: a bony registration was used to deliver the nodal CTV prescription. Second step: a gold marker registration was then used either to (1) complete the dose delivered to the prostate (complement); (2) or give almost the entire prescription to the prostate with a weak dose gradient between the targets to compensate for possible motions (gradient). The third method (COR) used a pool of precalculated plans based on images acquired at previous treatment fractions. At each new fraction, a plan is selected from that pool based on the daily position of prostate center-of-mass. The dosimetric comparison was conducted and results are presented with and without the systematic shift in the prostate position on the CT planning. The adaptive strategies were compared to the current clinical standard where all fractions are treated with the initial nonadaptive plan. Results: The minimum daily prostate D{sub 95%} is improved by 2%, 9%, and 6% for the complement, the gradient, and the COR approaches, respectively, compared to the nonadaptive method. The average nodal CTV D{sub 95%} remains constant across the

  1. Dosimetric properties of a proton beamline dedicated to the treatment of ocular disease

    SciTech Connect

    Slopsema, R. L. Mamalui, M.; Yeung, D.; Malyapa, R.; Li, Z.; Zhao, T.

    2014-01-15

    Purpose: A commercial proton eyeline has been developed to treat ocular disease. Radiotherapy of intraocular lesions (e.g., uveal melanoma, age-related macular degeneration) requires sharp dose gradients to avoid critical structures like the macula and optic disc. A high dose rate is needed to limit patient gazing times during delivery of large fractional dose. Dose delivery needs to be accurate and predictable, not in the least because current treatment planning algorithms have limited dose modeling capabilities. The purpose of this paper is to determine the dosimetric properties of a new proton eyeline. These properties are compared to those of existing systems and evaluated in the context of the specific clinical requirements of ocular treatments. Methods: The eyeline is part of a high-energy, cyclotron-based proton therapy system. The energy at the entrance of the eyeline is 105 MeV. A range modulator (RM) wheel generates the spread-out Bragg peak, while a variable range shifter system adjusts the range and spreads the beam laterally. The range can be adjusted from 0.5 up to 3.4 g/cm{sup 2}; the modulation width can be varied in steps of 0.3 g/cm{sup 2} or less. Maximum field diameter is 2.5 cm. All fields can be delivered with a dose rate of 30 Gy/min or more. The eyeline is calibrated according to the IAEA TRS-398 protocol using a cylindrical ionization chamber. Depth dose distributions and dose/MU are measured with a parallel-plate ionization chamber; lateral profiles with radiochromic film. The dose/MU is modeled as a function of range, modulation width, and instantaneous MU rate with fit parameters determined per option (RM wheel). Results: The distal fall-off of the spread-out Bragg peak is 0.3 g/cm{sup 2}, larger than for most existing systems. The lateral penumbra varies between 0.9 and 1.4 mm, except for fully modulated fields that have a larger penumbra at skin. The source-to-axis distance is found to be 169 cm. The dose/MU shows a strong dependence

  2. Assessing the Dosimetric Impact of Real-Time Prostate Motion During Volumetric Modulated Arc Therapy

    SciTech Connect

    Azcona, Juan Diego; Xing, Lei; Chen, Xin; Bush, Karl; Li, Ruijiang

    2014-04-01

    Purpose: To develop a method for dose reconstruction by incorporating the interplay effect between aperture modulation and target motion, and to assess the dosimetric impact of real-time prostate motion during volumetric modulated arc therapy (VMAT). Methods and Materials: Clinical VMAT plans were delivered with the TrueBeam linac for 8 patients with prostate cancer. The real-time target motion during dose delivery was determined based on the 2-dimensional fiducial localization using an onboard electronic portal imaging device. The target shift in each image was correlated with the control point with the same gantry angle in the VMAT plan. An in-house-developed Monte Carlo simulation tool was used to calculate the 3-dimensional dose distribution for each control point individually, taking into account the corresponding real-time target motion (assuming a nondeformable target with no rotation). The delivered target dose was then estimated by accumulating the dose from all control points in the plan. On the basis of this information, dose–volume histograms and 3-dimensional dose distributions were calculated to assess their degradation from the planned dose caused by target motion. Thirty-two prostate motion trajectories were analyzed. Results: The minimum dose to 0.03 cm{sup 3} of the gross tumor volume (D{sub 0.03cc}) was only slightly degraded after taking motion into account, with a minimum value of 94.1% of the planned dose among all patients and fractions. However, the gross tumor volume receiving prescription dose (V{sub 100%}) could be largely affected by motion, dropping below 60% in 1 trajectory. We did not observe a correlation between motion magnitude and dose degradation. Conclusions: Prostate motion degrades the delivered dose to the target in an unpredictable way, although its effect is reduced over multiple fractions, and for most patients the degradation is small. Patients with greater prostate motion or those treated with stereotactic body

  3. Dosimetric Study of Pelvic Proton Radiotherapy for High-Risk Prostate Cancer

    SciTech Connect

    Chera, Bhishamjit S.; Vargas, Carlos; Morris, Christopher G.; Louis, Debbie; Flampouri, Stella; Yeung, Daniel; Duvvuri, Srividya; Li Zuofeng; Mendenhall, Nancy Price

    2009-11-15

    Purpose: To compare dose distributions in targeted tissues (prostate, seminal vesicles, pelvic regional nodes) and nontargeted tissues in the pelvis with intensity-modulated radiotherapy (IMRT) and forward-planned, double-scattered, three-dimensional proton radiotherapy (3D-PRT). Methods and Materials: IMRT, IMRT followed by a prostate 3D-PRT boost (IMRT/3D-PRT), and 3D-PRT plans were created for 5 high-risk prostate cancer patients (n = 15 plans). A 78-CGE/Gy dose was prescribed to the prostate and proximal seminal vesicles and a 46-CGE/Gy was prescribed to the pelvic nodes. Various dosimetric endpoints were compared. Results: Target coverage of the prostate and nodal planning target volumes was adequate for all three plans. Compared with the IMRT and IMRT/3D-PRT plans, the 3D-PRT plans reduced the mean dose to the rectum, rectal wall, bladder, bladder wall, small bowel, and pelvis. The relative benefit of 3D-PRT (vs IMRT) at reducing the rectum and rectal wall V5-V40 was 53% to 71% (p < 0.05). For the bladder and bladder wall, the relative benefit for V5 to V40 CGE/Gy was 40% to 63% (p < 0.05). The relative benefit for reducing the volume of small bowel irradiated from 5 to 30 CGE/Gy in the 3D-PRT ranged from 62% to 69% (p < 0.05). Use of 3D-PRT did not produce the typical low-dose 'bath' of radiation to the pelvis seen with IMRT. Femoral head doses were higher for the 3D-PRT. Conclusions: Use of 3D-PRT significantly reduced the dose to normal tissues in the pelvis while maintaining adequate target coverage compared with IMRT or IMRT/3D-PRT. When treating the prostate, seminal vesicles, and pelvic lymph nodes in prostate cancer, proton therapy may improve the therapeutic ratio beyond what is possible with IMRT.

  4. 6 MV dosimetric characterization of the 160 MLC, the new Siemens multileaf collimator

    SciTech Connect

    Tacke, Martin B.; Nill, Simeon; Haering, Peter; Oelfke, Uwe

    2008-05-15

    New technical developments constantly aim at improving the outcome of radiation therapy. With the use of a computer-controlled multileaf collimator (MLC), the quality of the treatment and the efficiency in patient throughput is significantly increased. New MLC designs aim to further enhance the advantages. In this article, we present the first detailed experimental investigation of the new 160 MLC{sup TM}, Siemens Medical Solutions. The assessment included the experimental investigation of typical MLC characteristics such as leakage, tongue-and-groove effect, penumbra, leaf speed, and leaf positioning accuracy with a 6 MV treatment beam. The leakage is remarkably low with an average of 0.37% due to a new design principle of slightly tilted leaves instead of the common tongue-and-groove design. But due to the tilt, the triangular tongue-and-groove effect occurs. Its magnitude of approximately 19% is similar to the dose defect measured for MLCs with the common tongue-and-groove design. The average longitudinal penumbra measured at depth d{sub max}=15 mm with standard 100x100 mm{sup 2} fields is 4.1{+-}0.5 mm for the central range and increases to 4.9{+-}1.3 mm for the entire field range of 400x400 mm{sup 2}. The increase is partly due to the single-focusing design and the large distance between the MLC and the isocenter enabling a large patient clearance. Regarding the leaf speed, different velocity tests were performed. The positions of the moving leaves were continuously recorded with the kilovoltage-imaging panel. The maximum leaf velocities measured were 42.9{+-}0.6 mm/s. In addition, several typical intensity-modulated radiation therapy treatments were performed and the delivery times compared to the Siemens OPTIFOCUS MLC. An average decrease of 11% in delivery time was observed. The experimental results presented in this article indicate that the dosimetric characteristics of the 160 MLC are capable of improving the quality of dose delivery with respect to

  5. Dosimetric aspects of inverse-planned modulated-arc total-body irradiation

    SciTech Connect

    Held, Mareike; Kirby, Neil; Morin, Olivier; Pouliot, Jean

    2012-08-15

    Purpose: To develop optimal beam parameters and to verify the dosimetric aspects of the recently developed modulated-arc total-body irradiation (MATBI) technique, which delivers an inverse-planned dose to the entire body using gantry rotation. Methods: The patient is positioned prone and supine underneath the gantry at about 2 m source-to-surface distance (SSD). Then, up to 28 beams irradiate the patient from different gantry angles. Based on full-body computed-tomography (CT) images of the patient, the weight of each beam is optimized, using inverse planning, to create a uniform body dose. This study investigates how to best simulate patients and the ideal beam setup parameters, such as field size, number of beams, and beam geometry, for treatment time and dose homogeneity. In addition, three anthropomorphic water phantoms were constructed and utilized to verify the accuracy of dose delivery, with both diode array and ion chamber measurements. Furthermore, to improve the accuracy of the new technique, a beam model is created specifically for the extended-SSD positioning for MATBI. Results: Low dose CT scans can be utilized for dose calculations without affecting the accuracy. The largest field size of 40 Multiplication-Sign 40 cm{sup 2} was found to deliver the most uniform dose in the least amount of time. Moreover, a higher number of beams improves dose homogeneity. The average dose discrepancy between ion chamber measurements and extended-SSD beam model calculations was 1.2%, with the largest discrepancy being 3.2%. This average dose discrepancy was 1.4% with the standard beam model for delivery at isocenter. Conclusions: The optimum beam setup parameters, regarding dose uniformity and treatment duration, are laid out for modulated-arc TBI. In addition, the presented dose measurements show that these treatments can be delivered accurately. These measurements also indicated that a new beam model did not significantly improve the accuracy of dose calculations

  6. 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

    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.

  7. Reliability of Current Biokinetic and Dosimetric Models for Radionuclides: A Pilot Study

    SciTech Connect

    Leggett, Richard Wayne; Eckerman, Keith F; Meck, Robert A.

    2008-10-01

    This report describes the results of a pilot study of the reliability of the biokinetic and dosimetric models currently used by the U.S. Nuclear Regulatory Commission (NRC) as predictors of dose per unit internal or external exposure to radionuclides. The study examines the feasibility of critically evaluating the accuracy of these models for a comprehensive set of radionuclides of concern to the NRC. Each critical evaluation would include: identification of discrepancies between the models and current databases; characterization of uncertainties in model predictions of dose per unit intake or unit external exposure; characterization of variability in dose per unit intake or unit external exposure; and evaluation of prospects for development of more accurate models. Uncertainty refers here to the level of knowledge of a central value for a population, and variability refers to quantitative differences between different members of a population. This pilot study provides a critical assessment of models for selected radionuclides representing different levels of knowledge of dose per unit exposure. The main conclusions of this study are as follows: (1) To optimize the use of available NRC resources, the full study should focus on radionuclides most frequently encountered in the workplace or environment. A list of 50 radionuclides is proposed. (2) The reliability of a dose coefficient for inhalation or ingestion of a radionuclide (i.e., an estimate of dose per unit intake) may depend strongly on the specific application. Multiple characterizations of the uncertainty in a dose coefficient for inhalation or ingestion of a radionuclide may be needed for different forms of the radionuclide and different levels of information of that form available to the dose analyst. (3) A meaningful characterization of variability in dose per unit intake of a radionuclide requires detailed information on the biokinetics of the radionuclide and hence is not feasible for many infrequently

  8. A Dosimetric Model of Duodenal Toxicity After Stereotactic Body Radiotherapy for Pancreatic Cancer

    SciTech Connect

    Murphy, James D.; Christman-Skieller, Claudia; Kim, Jeff; Dieterich, Sonja; Chang, Daniel T.; Koong, Albert C.

    2010-12-01

    Introduction: Dose escalation for pancreas cancer is limited by the tolerance of adjacent normal tissues, especially with stereotactic body radiotherapy (SBRT). The duodenum is generally considered to be the organ at greatest risk. This study reports on the dosimetric determinants of duodenal toxicity with single-fraction SBRT. Methods and Materials: Seventy-three patients with locally advanced unresectable pancreatic adenocarcinoma received 25 Gy in a single fraction. Dose-volume histogram (DVH) endpoints evaluated include V{sub 5} (volume of duodenum that received 5 Gy), V{sub 10}, V{sub 15}, V{sub 20}, V{sub 25}, and D{sub max} (maximum dose to 1 cm{sup 3}). Normal tissue complication probability (NTCP) was evaluated with a Lyman model. Univariate and multivariate analyses were conducted with Kaplan-Meier and Cox regression models. Results: The median time to Grade 2-4 duodenal toxicity was 6.3 months (range, 1.6-11.8 months). The 6- and 12-month actuarial rates of toxicity were 11% and 29%, respectively. V{sub 10}-V{sub 25} and D{sub max} all correlated significantly with duodenal toxicity (p < 0.05). In particular, V{sub 15} {>=} 9.1 cm{sup 3} and V{sub 15} < 9.1 cm{sup 3} yielded duodenal toxicity rates of 52% and 11%, respectively (p = 0.002); V{sub 20} {>=} 3.3 cm{sup 3} and V{sub 20} < 3.3 cm{sup 3} gave toxicity rates of 52% and 11%, respectively (p = 0.002); and D{sub max} {>=} 23 Gy and D{sub max} < 23 Gy gave toxicity rates of 49% and 12%, respectively (p = 0.004). Lyman NTCP model optimization generated the coefficients m = 0.23, n = 0.12, and TD{sub 50} = 24.6 Gy. Only the Lyman NTCP model remained significant in multivariate analysis (p = 0.001). Conclusions: Multiple DVH endpoints and a Lyman NTCP model are strongly predictive of duodenal toxicity after SBRT for pancreatic cancer. These dose constraints will be valuable in future abdominal SBRT studies.

  9. Dosimetric evaluation of the staff working in a PET/CT department

    NASA Astrophysics Data System (ADS)

    Dalianis, K.; Malamitsi, J.; Gogou, L.; Pagou, M.; Efthimiadou, R.; Andreou, J.; Louizï, A.; Georgiou, E.

    2006-12-01

    The dosimetric literature data concerning the medical personnel working in positron emission tomography/computed tomography (PET/CT) departments are limited. Therefore, we measured the radiation dose of the staff working in the first PET/CT department in Greece at the Diagnostic and Therapeutic Center of Athens HYGEIA—Harvard Medical International. As, for the time being, only 2-deoxy-2-[ 18F]fluoro-d-glucose (FDG) PET studies are performed, radiation dose measurements concern those derived from dispensing of the radiopharmaceutical as well as from the patients undergoing FDG-PET imaging. Our aim is to develop more effective protective measures against radionuclide exposure. To estimate the effective dose from external exposure, all seven members of the staff (two nurses, two medical physicists, two technologists, one secretary) had TLD badges worn at the upper pocket of their overall, TLD rings on the right hand and digital dosimeters at their upper side pocket. In addition, isodose curves were measured with thermoluminescence detectors for distances of 20, 50, 70 and 100 cm away from patients who had been injected with 18F-FDG. Dose values of the PET/CT staff were measured with digital detectors, TLD badges and TLD rings over the first 8 months for a total of 160 working days of the department's operation, consisting of a workload of about 10-15 patients/week who received 250-420 MBq of 18F-FDG each. Whole - body collective doses and hand doses for the staff were the following: Nurse #1 received 1.6 mSv as a whole body dose and 2,1 as a hand dose, Nurse #2 received 1.9 and 2.4 mSv respectively. For medical physicist #1 the dose values were 1.45 mSv whole body and 1.7 mSv hand dose, for medical physicist #2 1.67 mSv wholebody dose and 1.55 mSv hand dose and for technologists #1 & #2 the whole body doses were 0.7 and 0.64 mSv respectively. Lastly, the secretary received 0.1 mSv whole body dose. These preliminary data have shown that the dose levels of our PET

  10. A feasibility study of using couch-based real time dosimetric device in external beam radiotherapy

    SciTech Connect

    Prabhakar, Ramachandran; Cramb, Jim; Kron, Tomas

    2011-12-15

    Purpose: Measurement of actual dose delivered during radiotherapy treatment aids in checking the accuracy of dose delivered to the patient. In this study, a couch-based real time dosimetric device has been proposed to measure the exit or entrance dose to a patient during external beam radiotherapy. The utility and feasibility of such a device using a 2D array of diodes has been demonstrated. Methods: Two MAPCHECK devices: MAPCHECK (1175) and MAPCHECK 2 (both SunNuclear) were embedded in a foam block in the treatment couch of a Varian 21iX linear accelerator. The angular dependence of the detector response for both devices was studied before implementing the MAPCHECKs for experimental purposes. An Alderson Rando head phantom was scanned with the MAPCHECK and MAPCHECK 2 devices separately and four different treatment plans were generated with target volumes at three different positions simulating typical clinical situations. The analytical anisotropic algorithm (AAA) was used to compute the doses in an Eclipse treatment planning system (Varian Medical Systems). The Rando phantom with the MAPCHECK device was exposed in Clinac 21iX linear accelerator. The measured dose distribution was compared with the calculated dose distribution to check for the accuracy in dose delivery. Results: Measured and computed dose distribution were found to agree with more than 93% of pixels passing at 3% and 3 mm gamma criteria for all the treatment plans. The couch-based real time dosimetry system may also be applied for noncoplanar beams where electronic portal imaging device (EPID) is not practical to measure the dose. Other advantages include checking the beam stability during the patient treatment, performing routine morning quality assurance (QA) tests in the linear accelerator, and to perform pretreatment verification of intensity modulated radiation therapy (IMRT). One of the drawbacks of this system is that it cannot be used for measuring the dose at 90 deg. or 270 deg. gantry

  11. Dosimetric characterization of GafChromic EBT film and its implication on film dosimetry quality assurance

    NASA Astrophysics Data System (ADS)

    Fuss, Martina; Sturtewagen, Eva; DeWagter, Carlos; Georg, Dietmar

    2007-07-01

    , presents a versatile system for high-precision dosimetry in two dimensions, provided that the intrinsic behaviour of the film reading device is taken into account. EBT film itself presents substantial improvements on formerly available models of radiographic and a radiochromic film and its dosimetric characteristics allow us to measure absorbed dose levels in a large variety of situations with a single calibration curve.

  12. An evaluation of some pertinent parameters that influence the dosimetric performance of synthetic diamond detectors

    NASA Astrophysics Data System (ADS)

    Ade, N.; Nam, T. L.; Mhlanga, S. H.

    2013-05-01

    correction using the Δ values obtained seemed to worsen the performance of the HPHT sample (up to about 3.3%) but it had a marginal effect on the performance of the CVD sample. In addition, the angular response of the CVD diamond detector was shown to be comparable with that of a cylindrical chamber. This study concludes that once the responses of the diamond detectors have been stabilised and they are properly shielded from ambient light, pre-irradiation prior to each measurement is not required. Also, the relative dose measured with the diamond detectors do not require dose rate dependence corrections as the required correction is only marginal and could have no dosimetric significance.

  13. Spine Radiosurgery: A Dosimetric Analysis in 124 Patients Who Received 18 Gy

    SciTech Connect

    Schipani, Stefano; Wen, Winston; Jin, Jain-Yue; Kim, Jin Koo; Ryu, Samuel

    2012-12-01

    Purpose: To define the safely tolerated doses to organs at risk (OARs) adjacent to the target volume (TV) of spine radiosurgery (SRS) with 18-Gy in a single fraction. Methods and Materials: A total of 124 patient cases with 165 spine metastases were reviewed. An 18-Gy single-fraction regimen was prescribed to the 90% isodose line encompassing the TV. A constraint of 10 Gy to 10% of the spinal cord outlined 6 mm above and below the TV was used. Dosimetric data to OARs were analyzed. Results: A total of 124 patients (100%) were followed-up, and median follow-up time was 7 months (1-50 months). Symptoms and local control were achieved in 114 patients (92%). Acute Radiation Therapy Oncology Group (RTOG) grade 1 oral mucositis occurred in 11 of 11 (100%) patients at risk for oropharyngeal toxicity after cervical spine treatment. There were no RTOG grade 2-4 acute or late complications. Median TV was 43.2 cc (5.3-175.4 cc) and 90% of the TV received median dose of 19 Gy (17-19.8 Gy). Median (range) of spinal cord maximum dose (Dmax), dose to spinal cord 0.35 cc (Dsc0.35), and cord volume receiving 10 Gy (Vsc10) were 13.8 Gy (5.4-21 Gy), 8.9 Gy (2.6-11.4 Gy) and 0.33 cc (0-1.6 cc), respectively. Other OARs were evaluated when in proximity to the TV. Esophagus (n=58), trachea (n=28), oropharynx (n=11), and kidneys (n=34) received median (range) V10 and V15 of 3.1 cc (0-5.8 cc) and 1.2 cc (0-2.9 cc), 2.8 cc (0-4.9 cc), and 0.8 cc (0-2.1 cc), 3.4 cc (0-6.2 cc) and 1.6 cc (0-3.2 cc), 0.3 cc (0-0.8 cc) and 0.08 cc (0-0.1 cc), respectively. Conclusions: Cord Dmax of 14 Gy and D0.35 of 10 Gy are safe dose constraints for 18-Gy single-fraction SRS. Esophagus V10 of 3 cc and V15 of 1 cc, trachea V10 of 3 cc, and V15 of 1 cc, oropharynx V10 of 3.5 cc and V15 of 1.5 cc, kidney V10 of 0.3 cc, and V15 of 0.1 cc are planning guidelines when these OARs are in proximity to the TV.

  14. New map data catalog

    NASA Astrophysics Data System (ADS)

    Map byproducts, including aerial photographs, color separations, map data in computer form, and other materials used in or produced during mapmaking, are described in a new catalog published by the U.S. Geological Survey.The 48-page hardcover catalog is the first listing of the unpublished USGS civilian cartographic holdings. It covers such items as mapping photographs, computer-enhanced LANDSAT pictures of Earth, cartographic data in computer form, microfilm and microfiche records, and a variety of features, including color separations, made in compiling and printing maps. The catalog also describes out-of-print maps available from USGS, along with land-use and land-cover maps, and other unusual items, such as slope maps and orthophotoquads. The catalog explains how to order advance copies of maps before they are published.

  15. Riparian Wetlands: Mapping

    EPA Science Inventory

    Riparian wetlands are critical systems that perform functions and provide services disproportionate to their extent in the landscape. Mapping wetlands allows for better planning, management, and modeling, but riparian wetlands present several challenges to effective mapping due t...

  16. Active Fire Mapping Program

    MedlinePlus

    ... Incidents (Home) New Large Incidents Fire Detection Maps MODIS Satellite Imagery VIIRS Satellite Imagery Fire Detection GIS ... Data Web Services Latest Detected Fire Activity Other MODIS Products Frequently Asked Questions About Active Fire Maps ...

  17. Creative Concept Mapping.

    ERIC Educational Resources Information Center

    Brown, David S.

    2002-01-01

    Recommends the use of concept mapping in science teaching and proposes that it be presented as a creative activity. Includes a sample lesson plan of a potato stamp concept mapping activity for astronomy. (DDR)

  18. Using maps in genealogy

    USGS Publications Warehouse

    ,

    1994-01-01

    In genealogy, maps are most often used as clues to where public or other records about an ancestor are likely to be found. Searching for maps seldom begins until a newcomer to genealogy has mastered basic genealogical routines

  19. Linkage map integration

    SciTech Connect

    Collins, A.; Teague, J.; Morton, N.E.; Keats, B.J.

    1996-08-15

    The algorithms that drive the map+ program for locus-oriented linkage mapping are presented. They depend on the enhanced location database program ldb+ to specify an initial comprehensive map that includes all loci in the summary lod file. Subsequently the map may be edited or order constrained and is automatically improved by estimating the location of each locus conditional on the remainder, beginning with the most discrepant loci. Operating characteristics permit rapid and accurate construction of linkage maps with several hundred loci. The map+ program also performs nondisjunction mapping with tests of nonstandard recombination. We have released map+ on Internet as a source program in the C language together with the location database that now includes the LODSOURCE database. 28 refs., 5 tabs.

  20. What Do Maps Show?

    ERIC Educational Resources Information Center

    Geological Survey (Dept. of Interior), Reston, VA.

    This curriculum packet, appropriate for grades 4-8, features a teaching poster which shows different types of maps (different views of Salt Lake City, Utah), as well as three reproducible maps and reproducible activity sheets which complement the maps. The poster provides teacher background, including step-by-step lesson plans for four geography…

  1. Quantitative DNA fiber mapping

    DOEpatents

    Gray, Joe W.; Weier, Heinz-Ulrich G.

    1998-01-01

    The present invention relates generally to the DNA mapping and sequencing technologies. In particular, the present invention provides enhanced methods and compositions for the physical mapping and positional cloning of genomic DNA. The present invention also provides a useful analytical technique to directly map cloned DNA sequences onto individual stretched DNA molecules.

  2. Oil Exploration Mapping

    NASA Technical Reports Server (NTRS)

    1994-01-01

    After concluding an oil exploration agreement with the Republic of Yemen, Chevron International needed detailed geologic and topographic maps of the area. Chevron's remote sensing team used imagery from Landsat and SPOT, combining images into composite views. The project was successfully concluded and resulted in greatly improved base maps and unique topographic maps.

  3. Applications of Concept Mapping

    ERIC Educational Resources Information Center

    De Simone, Christina

    2007-01-01

    This article reviews three major uses of the concept-mapping strategies for postsecondary learning: the external representation of concept maps as an external scratch pad to represent major ideas and their organization, the mental construction of concept maps when students are seeking a time-efficient tool, and the electronic construction and…

  4. Reading Angles in Maps

    ERIC Educational Resources Information Center

    Izard, Véronique; O'Donnell, Evan; Spelke, Elizabeth S.

    2014-01-01

    Preschool children can navigate by simple geometric maps of the environment, but the nature of the geometric relations they use in map reading remains unclear. Here, children were tested specifically on their sensitivity to angle. Forty-eight children (age 47:15-53:30 months) were presented with fragments of geometric maps, in which angle sections…

  5. Mapping with Young Children.

    ERIC Educational Resources Information Center

    Sunal, Cynthia Szymanski; Warash, Bobbi Gibson

    Techniques for encouraging young children to discover the purpose and use of maps are discussed. Motor activity and topological studies form a base from which the teacher and children can build a mapping program of progressive sophistication. Concepts important to mapping include boundaries, regions, exteriors, interiors, holes, order, point of…

  6. Using maps in genealogy

    USGS Publications Warehouse

    ,

    1999-01-01

    Maps are one of many sources you may need to complete a family tree. In genealogical research, maps can provide clues to where our ancestors may have lived and where to look for written records about them. Beginners should master basic genealogical research techniques before starting to use topographic maps.

  7. SU-E-J-72: Dosimetric Study of Cone-Beam CT-Based Radiation Treatment Planning Using a Patient-Specific Stepwise CT-Density Table

    SciTech Connect

    Chen, S; Le, Q; Mutaf, Y; Yi, B; D’Souza, W

    2015-06-15

    Purpose: To assess dose calculation accuracy of cone-beam CT (CBCT) based treatment plans using a patient-specific stepwise CT-density conversion table in comparison to conventional CT-based treatment plans. Methods: Unlike CT-based treatment planning which use fixed CT-density table, this study used patient-specific CT-density table to minimize the errors in reconstructed mass densities due to the effects of CBCT Hounsfield unit (HU) uncertainties. The patient-specific CT-density table was a stepwise function which maps HUs to only 6 classes of materials with different mass densities: air (0.00121g/cm3), lung (0.26g/cm3), adipose (0.95g/cm3), tissue (1.05 g/cm3), cartilage/bone (1.6g/cm3), and other (3g/cm3). HU thresholds to define different materials were adjusted for each CBCT via best match with the known tissue types in these images. Dose distributions were compared between CT-based plans and CBCT-based plans (IMRT/VMAT) for four types of treatment sites: head and neck (HN), lung, pancreas, and pelvis. For dosimetric comparison, PTV mean dose in both plans were compared. A gamma analysis was also performed to directly compare dosimetry in the two plans. Results: Compared to CT-based plans, the differences for PTV mean dose were 0.1% for pelvis, 1.1% for pancreas, 1.8% for lung, and −2.5% for HN in CBCT-based plans. The gamma passing rate was 99.8% for pelvis, 99.6% for pancreas, and 99.3% for lung with 3%/3mm criteria, and 80.5% for head and neck with 5%/3mm criteria. Different dosimetry accuracy level was observed: 1% for pelvis, 3% for lung and pancreas, and 5% for head and neck. Conclusion: By converting CBCT data to 6 classes of materials for dose calculation, 3% of dose calculation accuracy can be achieved for anatomical sites studied here, except HN which had a 5% accuracy. CBCT-based treatment planning using a patient-specific stepwise CT-density table can facilitate the evaluation of dosimetry changes resulting from variation in patient anatomy.

  8. Development of radiochromic film for spatially quantitative dosimetric analysis of indirect ionizing radiation fields

    NASA Astrophysics Data System (ADS)

    Brady, Samuel Loren

    sensors measured < 2% and < 7% deviation in pixel light intensities for 50 consecutive scans, respectively. Both scanner light sources were shown to be uniform in transmission and reflection scan modes along the center axis of light source translation. Additionally, RCFs demonstrated a larger dynamic range in pixel light intensities, and to be less sensitive to off axis light inhomogeneity, when scanned in landscape mode (long axis of film parallel with axis of light source translation). The EPSON 10000XL demonstrated slightly better light source/CCD temporal stability and provided a capacity to scan larger film formats at the center of the scanner in landscape mode. However, the EPSON V700 only measured an overall difference in accuracy and precision by 2%, and though smaller in size, at the time of this work, was one sixth the cost of the 10000XL. A scan protocol was developed to maximize RCF digitization accuracy and precision, and a calibration fitting function was developed for RCF absolute dosimetry. The fitting function demonstrated a superior goodness of fit for both RCF types over a large range of absorbed dose levels as compared to the currently accepted function found in literature. The RCF dosimetry system was applied to three novel areas from which a benefit could be derived for 2D or 3D dosimetric information. The first area was for a 3D dosimetry of a pendant breast in 3D-CT mammography. The novel method of developing a volumetric image of the breast from a CT acquisition technique was empirically measured for its dosimetry and compared to standard dual field digital mammography. The second area was dose reduction in CT for pediatric and adult scan protocols. In this application, novel methodologies were developed to measure 3D organ dosimetry and characterize a dose reduction scan protocol for pediatric and adult body habitus. The third area was in the field of small animal irradiation for radiobiology purposes and cancer patient treatment verification. In

  9. SU-E-J-66: Significant Anatomical and Dosimetric Changes Observed with the Pharyngeal Constrictor During Head and Neck Radiotherapy Elicited From Daily Deformable Image Registration and Dose Accumulation

    SciTech Connect

    Kumarasiri, A; Siddiqui, F; Liu, C; Kamal, M; Fraser, C; Chetty, I; Kim, J

    2015-06-15

    Purpose: To evaluate the anatomical changes and associated dosimetric consequences to the pharyngeal constrictor (PC) that occurs during head and neck radiotherapy (H&N RT). Methods: A cohort of 13 oro-pharyngeal cancer patients, who had daily CBCT’s for localization, was retrospectively studied. On every 5th CBCT, PC was manually delineated by a radiation oncologist. The anterior-posterior PC thickness was measured at the C3 level. Delivered dose to PC was estimated by calculating daily doses on CBCT’s, and accumulating to corresponding planning CT images. For accumulation, a parameter-optimized B- spline-based deformable image registration algorithm (Elastix) was used, in conjunction with an energy-mass mapping dose transfer algorithm. Mean and maximum dose (Dmean, Dmax) to PC was determined and compared with corresponding planned quantities. Results: The mean (±standard deviation) volume increase (ΔV) and thickness increase (Δt) over the course of 35 total fractions were 54±33% (11.9±7.6 cc), and 63±39% (2.9±1.9 mm), respectively. The resultant cumulative mean dose increase from planned dose to PC (ΔDmean) was 1.4±1.3% (0.9±0.8 Gy), while the maximum dose increase (ΔDmax) was 0.0±1.6% (0.0±1.1 Gy). Patients with adaptive replanning (n=6) showed a smaller mean dose increase than those without (n=7); 0.5±0.2% (0.3±0.1 Gy) vs. 2.2±1.4% (1.4±0.9 Gy). There was a statistically significant (p<0.0001) strong correlation between ΔDmean and Δt (Pearson coefficient r=0.78), and a moderate-to-strong correlation (r=0.52) between ΔDmean and ΔV. Correlation between ΔDmean and weight loss ΔW (r=0.1), as well as ΔV and ΔW (r=0.2) were negligible. Conclusion: Patients were found to undergo considerable anatomical changes to pharyngeal constrictor during H&N RT, resulting in non-negligible dose deviations from intended dose. Results are indicative that pharyngeal constrictor thickness, measured at C3 level, is a good predictor for the dose change to

  10. Map projections for larger-scale mapping

    NASA Technical Reports Server (NTRS)

    Snyder, J. P.

    1982-01-01

    For the U.S. Geological Survey maps at 1:1,000,000-scale and larger, the most common projections are conformal, such as the Transverse Mercator and Lambert Conformal Conic. Projections for these scales should treat the Earth as an ellipsoid. In addition, the USGS has conceived and designed some new projections, including the Space Oblique Mercator, the first map projection designed to permit low-distortion mapping of the Earth from satellite imagery, continuously following the groundtrack. The USGS has programmed nearly all pertinent projection equations for inverse and forward calculations. These are used to plot maps or to transform coordinates from one projection to another. The projections in current use are described.

  11. Cartographic mapping study

    NASA Technical Reports Server (NTRS)

    Wilson, C.; Dye, R.; Reed, L.

    1982-01-01

    The errors associated with planimetric mapping of the United States using satellite remote sensing techniques are analyzed. Assumptions concerning the state of the art achievable for satellite mapping systems and platforms in the 1995 time frame are made. An analysis of these performance parameters is made using an interactive cartographic satellite computer model, after first validating the model using LANDSAT 1 through 3 performance parameters. An investigation of current large scale (1:24,000) US National mapping techniques is made. Using the results of this investigation, and current national mapping accuracy standards, the 1995 satellite mapping system is evaluated for its ability to meet US mapping standards for planimetric and topographic mapping at scales of 1:24,000 and smaller.

  12. On genetic map functions

    SciTech Connect

    Zhao, Hongyu; Speed, T.P.

    1996-04-01

    Various genetic map functions have been proposed to infer the unobservable genetic distance between two loci from the observable recombination fraction between them. Some map functions were found to fit data better than others. When there are more than three markers, multilocus recombination probabilities cannot be uniquely determined by the defining property of map functions, and different methods have been proposed to permit the use of map functions to analyze multilocus data. If for a given map function, there is a probability model for recombination that can give rise to it, then joint recombination probabilities can be deduced from this model. This provides another way to use map functions in multilocus analysis. In this paper we show that stationary renewal processes give rise to most of the map functions in the literature. Furthermore, we show that the interevent distributions of these renewal processes can all be approximated quite well by gamma distributions. 43 refs., 4 figs.

  13. Evaluation of Dosimetric Parameters and Disease Response After {sup 125}Iodine Transperineal Brachytherapy for Low- and Intermediate-Risk Prostate Cancer

    SciTech Connect

    Morris, W. James Keyes, Mira M.D.; Palma, David M.D.; McKenzie, Michael; Spadinger, Ingrid; Agranovich, Alex; Pickles, Tom; Liu, Mitchell; Kwan, Winkle; Wu, Jonn; Lapointe, Vince; Berthelet, Eric; Pai, Howard; Harrison, Robert; Kwa, William; Bucci, Joe; Racz, Violet; Woods, Ryan

    2009-04-01

    Purpose: To analyze dosimetric outcomes after permanent brachytherapy for men with low-risk and 'low-tier' intermediate-risk prostate cancer and explore the relationship between the traditional dosimetric values, V100 (volume of prostate receiving 100% of the prescribed dose) and D90 (minimum dose to 90% of the prostate), and risk of biochemical failure. Methods and Materials: A total of 1,006 consecutive patients underwent implantation between July 20, 1998, and Oct 23, 2003. Most (58%) had low-risk disease; the remaining 42% comprised a selected low-tier subgroup of intermediate-risk patients. The prescribed minimum peripheral dose (MPD) was 144 Gy. All implants used 0.33 mCi {sup 125}I sources using a preplan technique featuring right-left symmetry and a strong posterior-peripheral dose bias. Sixty-five percent of patients had 6 months of androgen deprivation therapy. Postimplantation dosimetry was calculated using day-28 CT scans. Results: With a median follow-up of 54 months, the actuarial 5-year rate of freedom from biochemical recurrence (bNED) was 95.6% {+-} 1.6%. Median D90 was 105% of MPD, median V100 was 92%, median V150 was 58%, and median V200 was 9%. Dosimetric values were not predictive of biochemical recurrence on univariate or multivariate analysis. Analysis of dosimetric values by implantation number showed statistically significant increases in all values with time (D90, V100, V150, and V200; p < 0.001), but this did not translate into improved bNED. Conclusions: In contrast to some previous studies, dosimetric outcomes did not correlate with biochemical recurrence in the first 1,006 patients treated with {sup 125}I prostate brachytherapy at the British Columbia Cancer Agency. Despite a median D90 of only 105% of MPD, our bNED rates are indistinguishable from series that reported higher D90 values.

  14. The intrafraction motion induced dosimetric impacts in breast 3D radiation treatment: A 4DCT based study

    SciTech Connect

    Yue, Ning J.; Li Xiang; Beriwal, Sushil; Heron, Dwight E.; Sontag, Marc R.; Huq, M. Saiful

    2007-07-15

    The question remains regarding the dosimetric impact of intrafraction motion in 3D breast treatment. This study was conducted to investigate this issue utilizing the 4DCT scan. The 4D and helical CT scan sets were acquired for 12 breast cancer patients. For each of these patients, based on the helical CT scan, a conventional 3D conformal plan was generated. The breast treatment was then simulated based on the 4DCT scan. In each phase of the 4DCT scan, dose distribution was generated with the same beam parameters as the conventional plan. A software package was developed to compute the cumulative dose distribution from all the phases. Since the intrafraction organ motion is reflected by the 4DCT images, the cumulative dose computed based on the 4DCT images should be closer to what the patient received during treatment. Various dosimetric parameters were obtained from the plan and 4D cumulative dose distribution for the target volume and heart, and were compared to deduce the motion-induced impacts. The studies were performed for both whole breast and partial breast treatment. In the whole breast treatment, the average intrafraction motion induced changes in D{sub 95}, D{sub 90}, V{sub 100}, V{sub 95}, and V{sub 90} of the target volume were -5.4%, -3.1%, -13.4%, -5.1%, and -3.2%, respectively, with the largest values at -26.2%, -14.1%, -91.0%, -15.1%, and -9.0%, respectively. Motion had little impact on the D{sub max} of the target volume, but its impact on the D{sub min} of the target volume was significant. For left breast treatment, the motion-induced D{sub max} change to the heart could be negative or positive, with the largest increase at about 6 Gy. In partial breast treatment, the only non-insignificant impact was in the D{sub min} of the CTV (ranging from -15.2% to 11.7%). The results showed that the intrafraction motion may compromise target dose coverage in breast treatments and the degree of that compromise was correlated with motion magnitude. However

  15. Dosimetric impact of source-positioning uncertainty in high-dose-rate balloon brachytherapy of breast cancer

    PubMed Central

    2015-01-01

    Purpose To evaluate the dosimetric impact of source-positioning uncertainty in high-dose-rate (HDR) balloon brachytherapy of breast cancer. Material and methods For 49 HDR balloon patients, each dwell position of catheter(s) was manually shifted distally (+) and proximally (–) with a magnitude from 1 to 4 mm. Total 392 plans were retrospectively generated and compared to corresponding clinical plans using 7 dosimetric parameters: dose (D95) to 95% of planning target volume for evaluation (PTV_EVAL), and volume covered by 100% and 90% of the prescribed dose (PD) (V100 and V90); skin and rib maximum point dose (Dmax); normal breast tissue volume receiving 150% and 200% of PD (V150 and V200). Results PTV_EVAL dosimetry deteriorated with larger average/maximum reduction (from ± 1 mm to ± 4 mm) for larger source position uncertainty (p value < 0.0001): from 1.0%/2.5%, 3.3%/5.9%, 6.3%/10.0% to 9.8%/14.5% for D95; from 1.0%/2.6%, 3.1%/5.7%, 5.8%/8.9% to 8.7%/12.3% for V100; from 0.2%/1.5%, 1.0%/4.0%, 2.7%/6.8% to 5.1%/10.3% for V90. ≥ ± 3 mm shift reduced average D95 to < 95% and average V100 to < 90%. While skin and rib Dmax change was case-specific, its absolute change (∣Δ(Value)∣) showed that larger shift and high dose group had larger variation compared to smaller and lower dose group (p value < 0.0001), respectively. Normal breast tissue V150 variation was case-specific and small. Average ∣Δ(V150)∣ was 0.2 cc for the largest shift (± 4 mm) with maximum < 1.7 cc. V200 was increased with higher elevation for larger shift: from 6.4 cc/9.8 cc, 7.0 cc/10.1 cc, 8.0 cc/11.3 cc to 9.2 cc/ 13.0 cc. Conclusions The tolerance of ± 2 mm recommended by AAPM TG 56 is clinically acceptable in most clinical cases. However, special attention should be paid to a case where both skin and rib are located proximally to balloon, and the orientation of balloon catheter(s) is vertical to these critical structures. In this case, sufficient dosimetric planning margins are

  16. SU-F-BRD-06: Dosimetric Cost of a GTV Margin for Simultaneous Integrated Intra- Prostatic Boost Treatments

    SciTech Connect

    Studenski, M; Abramowitz, M; Dogan, N; Pollack, A

    2014-06-15

    Purpose: Quantify the dosimetric cost for a margin around the MRI-defined high risk GTV for simultaneous integrated intra-prostatic boosts (SIIB) treated with RapidArc. Methods: For external beam radiotherapy of the prostate, a 3-7 mm PTV margin is typically used to account for setup and intra-fraction uncertainties after adjusting for inter-fraction motion. On the other hand, our current paradigm is to treat the MRI-defined high risk GTV with no margin. In this work, 11 patients treated SIIB (7 post-prostatectomy, 4 intact prostate) with RapidArc were re-planned with 1-5 mm margins around the GTV to quantify dosimetric effects. Two 358 degree, 10 MV RapidArcs were used to deliver 68 Gy (76.5 Gy boost) to the post-prostatectomy patients and 80 Gy (86 Gy boost) to the intact prostates. Paired, two tail t-tests were used to determine if there were any significant differences (p<0.05) in the total MUs and dosimetric parameters used to evaluate rectum, bladder, and PTV dose with and without margin. Results: The average GTV volume without margin was 8.1cc (2.8% of the PTV volume) while the average GTV volume with a 5 mm margin was 20.1cc (9.0% of the PTV volume). GTV volumes ranged from 0.2% of the PTV volume up to 33.0%. Despite these changes in volume, the only statistical difference was found for the rectal V65 Gy with a 5 mm margin (18.6% vs. 19.4%; p-value = 0.026) when all patients were considered as a single group. No difference was found when analyzed as two groups. The rectum V40Gy, bladder V40Gy and V65Gy, PTV Dmax and D95% or the total MUs did not show any significant difference for any margin. Conclusion: A 4 mm margin on the high risk GTV is possible with no statistically significant change in dosimetry or total MUs. Further work will assess the appropriate margin required for intra-prostatic boosts.

  17. New method to perform dosimetric quality control of treatment planning system using PENELOPE Monte Carlo and anatomical digital test objects

    NASA Astrophysics Data System (ADS)

    Benhdech, Yassine; Beaumont, Stéphane; Guédon, Jean-Pierre; Torfeh, Tarraf

    2010-04-01

    In this paper, we deepen the R&D program named DTO-DC (Digital Object Test and Dosimetric Console), which goal is to develop an efficient, accurate and full method to achieve dosimetric quality control (QC) of radiotherapy treatment planning system (TPS). This method is mainly based on Digital Test Objects (DTOs) and on Monte Carlo (MC) simulation using the PENELOPE code [1]. These benchmark simulations can advantageously replace experimental measures typically used as reference for comparison with TPS calculated dose. Indeed, the MC simulations rather than dosimetric measurements allow contemplating QC without tying treatment devices and offer in many situations (i.p. heterogeneous medium, lack of scattering volume...) better accuracy compared to dose measurements with classical dosimetry equipment of a radiation therapy department. Furthermore using MC simulations and DTOs, i.e. a totally numerical QC tools, will also simplify QC implementation, and enable process automation; this allows radiotherapy centers to have a more complete and thorough QC. The program DTO-DC was established primarily on ELEKTA accelerator (photons mode) using non-anatomical DTOs [2]. Today our aim is to complete and apply this program on VARIAN accelerator (photons and electrons mode) using anatomical DTOs. First, we developed, modeled and created three anatomical DTOs in DICOM format: 'Head and Neck', Thorax and Pelvis. We parallelized the PENELOPE code using MPI libraries to accelerate their calculation, we have modeled in PENELOPE geometry Clinac head of Varian Clinac 2100CD (photons mode). Then, to implement this method, we calculated the dose distributions in Pelvis DTO using PENELOPE and ECLIPSE TPS. Finally we compared simulated and calculated dose distributions employing the relative difference proposed by Venselaar [3]. The results of this work demonstrate the feasibility of this method that provides a more accurate and easily achievable QC. Nonetheless, this method, implemented

  18. SU-E-J-39: Dosimetric Benefit of Implanted Marker-Based CBCT Setup for Definitive Prostatic Radiotherapy

    SciTech Connect

    Zhen, H; Wu, Z; Bluemenfeld, P; Chu, J; Wang, D

    2015-06-15

    Purpose Daily setup for definitive prostatic radiotherapy is challenged by suboptimal visibility of the prostate boundary and daily variation of rectum shape and position. For patients with improved bowel preparation, we conducted a dosimetric comparison between prostate implanted marker (IM)-based daily setup and anterior rectal wall (ARW)-based setup, with the hypothesis that the former leads to adequate target coverage with better rectal sparing. Methods Five IMRT/VMAT prostate cases with implanted markers were selected for analysis. Daily CBCT showed improvement of the rectal volume compared to planning CT. For each patient, the prostate and rectum were contoured on three CBCT images (fraction 5/15/25) with subsequent physician review. The CBCTs were then registered to a planning CT using IM-based registration. The deviation of ARW positions from planning CT to CBCT were analyzed at various sup-inf levels (−1.8 cm to 1.8 cm from level of prostate center). To estimate the potential dosimetric impact from ARW-based setup, the treatment plans were recalculated using A-P shifts ranging from −1mm to +6mm. Clinically important rectum DVH values including Dmax, D3cc and Dmean were computed. Results For the studied patients, we observed on average 32% rectum volume reduction from planning CT to CBCT. As a Results, the ARW on average shifts posteriorly by −1mm to +5mm, depending on the sup-inf level of observation, with larger shifts observed at more superior levels. Recalculation shows that when ARW shifts 1mm posteriorly, ARW-based CBCT setup leads to a 1.0%, 4.2%, and 3.2% increase in rectum Dmax, D3cc, and Dmean, respectively, compared to IM-based setup. The dosimetric deviations increase to 4.7%, 25.8% and 24.7% when ARW shifts 6mm posteriorly. No significant prostate-only dose difference was observed. Conclusion For patients with improved bowel preparation, IM-based CBCT setup leads to accurate prostate coverage along with significantly lower rectal dose

  19. Dosimetric comparison of partial and whole breast external beam irradiation in the treatment of early stage breast cancer.

    PubMed

    Kim, Yongbok; Parda, David S; Trombetta, Mark G; Colonias, Athanasios; Werts, E Day; Miller, Linda; Miften, Moyed

    2007-12-01

    A dosimetric comparison was performed on external-beam three-dimensional conformal partial breast irradiation (PBI) and whole breast irradiation (WBI) plans for patients enrolled in the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-39/Radiation Therapy Oncology Group (RTOG) 0413 protocol at our institution. Twenty-four consecutive patients were treated with either PBI (12 patients) or WBI (12 patients). In the PBI arm, the lumpectomy cavity was treated to a total dose of 38.5 Gy at 3.85 Gy per fraction twice daily using a four-field noncoplanar beam setup. A minimum 6 h interval was required between fractions. In the WBI arm, the whole breast including the entirety of the lumpectomy cavity was treated to a total dose of 50.4 Gy at 1.8 Gy per fraction daily using opposed tangential beams. The lumpectomy cavity volume, planning target volume for evaluation (PTV_EVAL), and critical structure volumes were contoured for both the PBI and WBI patients. Dosimetric parameters, dose volume histograms (DVHs), and generalized equivalent uniform dose (gEUD) for target and critical structures were compared. Dosimetric results show the PBI plans, compared to the WBI plans, have smaller hot spots in the PTV_EVAL (maximum dose: 104.2% versus 110.9%) and reduced dose to the ipsilateral breast (V50: 48.6% versus 92.1% and V100: 10.2% versus 50.5%), contralateral breast (V3: 0.16% versus 2.04%), ipsilateral lung (V30: 5.8% versus 12.7%), and thyroid (maximum dose: 0.5% versus 2.0%) with p values < or = 0.01. However, similar dose coverage of the PTV_EVAL (98% for PBI and 99% for WBI, on average) was observed and the dose difference for other critical structures was clinically insignificant in both arms. The gEUD data analysis showed the reduction of dose to the ipsilateral breast and lung, contralateral breast and thyroid. In addition, preliminary dermatologic adverse event assessment data suggested reduced skin toxicity for patients treated with the PBI technique.

  20. Dosimetric characterization and application of an imaging beam line with a carbon electron target for megavoltage cone beam computed tomography.

    PubMed

    Flynn, Ryan T; Hartmann, Julia; Bani-Hashemi, Ali; Nixon, Earl; Alfredo, R; Siochi, C; Pennington, Edward C; Bayouth, John E

    2009-06-01

    Imaging dose from megavoltage cone beam computed tomography (MVCBCT) can be significantly reduced without loss of image quality by using an imaging beam line (IBL), with no flattening filter and a carbon, rather than tungsten, electron target. The IBL produces a greater keV-range x-ray fluence than the treatment beam line (TBL), which results in a more optimal detector response. The IBL imaging dose is not necessarily negligible, however. In this work an IBL was dosimetrically modeled with the Philips Pinnacle3 treatment planning system (TPS), verified experimentally, and applied to clinical cases. The IBL acquisition dose for a 200 degrees gantry rotation was verified in a customized acrylic cylindrical phantom at multiple imaging field sizes with 196 ion chamber measurements. Agreement between the measured and calculated IBL dose was quantified with the 3D gamma index. Representative IBL and TBL imaging dose distributions were calculated for head and neck and prostate patients and included in treatment plans using the imaging dose incorporation (IDI) method. Surface dose was measured for the TBL and IBL for four head and neck cancer patients with MOSFETs. The IBL model, when compared to the percentage depth dose and profile measurements, had 97% passing gamma indices for dosimetric and distance acceptance criteria of 3%, 3 mm, and 100% passed for 5.2%, 5.2 mm. For the ion chamber measurements of phantom image acquisition dose, the IBL model had 93% passing gamma indices for acceptance criteria of 3%, 3 mm, and 100% passed for 4%, 4 mm. Differences between the IBL- and TBL-based IMRT treatment plans created with the IDI method were dosimetrically insignificant for both the prostate and head and neck cases. For IBL and TBL beams with monitor unit values that would result in the delivery of the same dose to the depth of maximum dose under standard calibration conditions, the IBL imaging surface dose was higher than the TBL imaging surface dose by an average of 18

  1. Dosimetric comparison of 3D conformal, IMRT, and V-MAT techniques for accelerated partial-breast irradiation (APBI)

    SciTech Connect

    Qiu, Jian-Jian; Chang, Zheng; Horton, Janet K.; Wu, Qing-Rong Jackie; Yoo, Sua; Yin, Fang-Fang

    2014-07-01

    The purpose is to dosimetrically compare the following 3 delivery techniques: 3-dimensional conformal radiation therapy (3D-CRT), intensity-modulated arc therapy (IMRT), and volumetric-modulated arc therapy (V-MAT) in the treatment of accelerated partial-breast irradiation (APBI). Overall, 16 patients with T1/2N0 breast cancer were treated with 3D-CRT (multiple, noncoplanar photon fields) on the RTOG 0413 partial-breast trial. These cases were subsequently replanned using static gantry IMRT and V-MAT technology to understand dosimetric differences among these 3 techniques. Several dosimetric parameters were used in plan quality evaluation, including dose conformity index (CI) and dose-volume histogram analysis of normal tissue coverage. Quality assurance studies including gamma analysis were performed to compare the measured and calculated dose distributions. The IMRT and V-MAT plans gave more conformal target dose distributions than the 3D-CRT plans (p < 0.05 in CI). The volume of ipsilateral breast receiving 5 and 10 Gy was significantly less using the V-MAT technique than with either 3D-CRT or IMRT (p < 0.05). The maximum lung dose and the ipsilateral lung volume receiving 10 (V{sub 10}) or 20 Gy (V{sub 20}) were significantly less with both V-MAT and IMRT (p < 0.05). The IMRT technique was superior to 3D-CRT and V-MAT of low dose distributions in ipsilateral lung (p < 0.05 in V{sub 5} and D{sub 5}). The total mean monitor units (MUs) for V-MAT (621.0 ± 111.9) were 12.2% less than those for 3D-CRT (707.3 ± 130.9) and 46.5% less than those for IMRT (1161.4 ± 315.6) (p < 0.05). The average machine delivery time was 1.5 ± 0.2 minutes for the V-MAT plans, 7.0 ± 1.6 minutes for the 3D-CRT plans, and 11.5 ± 1.9 minutes for the IMRT plans, demonstrating much less delivery time for V-MAT. Based on this preliminary study, V-MAT and IMRT techniques offer improved dose conformity as compared with 3D-CRT techniques without increasing dose to the ipsilateral lung. In

  2. Dosimetric comparison of treatment plans based on free breathing, maximum, and average intensity projection CTs for lung cancer SBRT

    SciTech Connect

    Tian Yuan; Wang Zhiheng; Ge Hong; Zhang Tian; Cai Jing; Kelsey, Christopher; Yoo, David; Yin Fangfang

    2012-05-15

    Purpose: To determine whether there is a CT dataset may be more favorable for planning and dose calculation by comparing dosimetric characteristics between treatment plans calculated using free breathing (FB), maximum and average intensity projection (MIP and AIP, respectively) CTs for lung cancer patients receiving stereotactic body radiation therapy (SBRT). Methods: Twenty lung cancer SBRT patients, treated on a linac with 2.5 mm width multileaf-collimator (MLC), were analyzed retrospectively. Both FB helical and four-dimensional CT scans were acquired for each patient. Internal target volume (ITV) was delineated based on MIP CTs and modified based on both ten-phase datasets and FB CTs. Planning target volume (PTV) was then determined by adding additional setup margin to ITV. The PTVs and beams in the optimized treatment plan based on FB CTs were copied to MIP and AIP CTs, with the same isocenters, MLC patterns and monitor units. Mean effective depth (MED) of beams, and some dosimetric parameters for both PTVs and most important organ at risk (OAR), lung minus PTV, were compared between any two datasets using two-tail paired t test. Results: The MEDs in FB and AIP plans were similar but significantly smaller (Ps < 0.001) than that in MIP plans. Minimum dose, mean dose, dose covering at least 90% and 95% of PTVs in MIP plans were slightly higher than two other plans (Ps < 0.008). The absolute volume of lung minus PTV receiving greater than 5, 10, and 20 Gy in MIP plans were significantly smaller than those in both FB and AIP plans (Ps < 0.008). Conformity index for FB plans showed a small but statistically significantly higher. Conclusions: Dosimetric characteristics of AIP plans are similar to those of FB plans. Slightly better target volume coverage and significantly lower low-dose region ({<=}30 Gy) in lung was observed in MIP plans. The decrease in low-dose region in lung was mainly caused by the change of lung volume contoured on two datasets rather than the

  3. Verification of dosimetric accuracy on the TrueBeam STx: Rounded leaf effect of the high definition MLC

    SciTech Connect

    Kielar, Kayla N.; Mok, Ed; Hsu, Annie; Wang Lei; Luxton, Gary

    2012-10-15

    Purpose: The dosimetric leaf gap (DLG) in the Varian Eclipse treatment planning system is determined during commissioning and is used to model the effect of the rounded leaf-end of the multileaf collimator (MLC). This parameter attempts to model the physical difference between the radiation and light field and account for inherent leakage between leaf tips. With the increased use of single fraction high dose treatments requiring larger monitor units comes an enhanced concern in the accuracy of leakage calculations, as it accounts for much of the patient dose. This study serves to verify the dosimetric accuracy of the algorithm used to model the rounded leaf effect for the TrueBeam STx, and describes a methodology for determining best-practice parameter values, given the novel capabilities of the linear accelerator such as flattening filter free (FFF) treatments and a high definition MLC (HDMLC). Methods: During commissioning, the nominal MLC position was verified and the DLG parameter was determined using MLC-defined field sizes and moving gap tests, as is common in clinical testing. Treatment plans were created, and the DLG was optimized to achieve less than 1% difference between measured and calculated dose. The DLG value found was tested on treatment plans for all energies (6 MV, 10 MV, 15 MV, 6 MV FFF, 10 MV FFF) and modalities (3D conventional, IMRT, conformal arc, VMAT) available on the TrueBeam STx. Results: The DLG parameter found during the initial MLC testing did not match the leaf gap modeling parameter that provided the most accurate dose delivery in clinical treatment plans. Using the physical leaf gap size as the DLG for the HDMLC can lead to 5% differences in measured and calculated doses. Conclusions: Separate optimization of the DLG parameter using end-to-end tests must be performed to ensure dosimetric accuracy in the modeling of the rounded leaf ends for the Eclipse treatment planning system. The difference in leaf gap modeling versus physical

  4. Evaluating dosimetric accuracy of flattening filter free compensator-based IMRT: Measurements with diode arrays

    SciTech Connect

    Robinson, Joshua; Opp, Daniel; Zhang, Geoffrey; Cashon, Ken; Kozelka, Jakub; Hunt, Dylan; Walker, Luke; Hoffe, Sarah; Shridhar, Ravi; Feygelman, Vladimir

    2012-01-15

    Purpose: Compensator-based IMRT coupled with the high dose rate flattening filter free (FFF) beams offers an intriguing possibility of delivering an intensity modulated radiation field in just a few seconds. As a first step, the authors evaluate the dosimetric accuracy of the treatment planning system (TPS) FFF beam model with compensators. Methods: A 6 MV FFF beam from a TrueBeam accelerator (Varian Medical Systems, Palo Alto CA) was modeled in PINNACLE TPS (v. 9.0, Philips Radiation Oncology, Fitchburg WI). Flat brass slabs from 0.3 to 7 cm thick and an 18 deg. brass wedge were used to adjust the beam model. A 2D (MAPCHECK) and 3D (ARCCHECK) diode arrays (Sun Nuclear Corp, Melbourne FL), were investigated for use with the compensator FFF beams. Corrections for diode sensitivity caused by the spectral changes in the beam were introduced. Four compensator plans based on the AAPM TG-119 report were developed. A composite ion chamber measurement, beam by beam MAPCHECK measurements, and a composite ARCCHECK measurement were performed. The array results were analyzed with the same thresholds as in TG-119 report--3%/3 mm with global dose normalization--as well as with the more stringent combinations of the gamma analysis criteria. Results: The FFF beam shows a greater variation of the effective attenuation coefficient with brass thickness due to the prevalence of the low energy photons compared to the conventional 6X beam. As a result, a compromise had to be made while trying to achieve dose agreement for a combination of field sizes, brass thicknesses, and measurement depths ({>=}5 cm in water). An agreement of measured and calculated dose to within 1% was observed for brass thicknesses up to 2 cm. For the 3 cm slab, an error of up to 2.8% was noted for the field sizes above 10 x 10 cm{sup 2}, and up to 3.8% for the 5 x 5 cm{sup 2} field. Both diode arrays exhibit a substantial sensitivity drop as the compensator thickness increases, reaching 10% for a 7 cm brass slab

  5. Dosimetric characterization of the iBEAM evo carbon fiber couch for radiotherapy

    SciTech Connect

    Smith, David W.; Christophides, Damianos; Dean, Christopher; Naisbit, Mitchell; Mason, Joshua; Morgan, Andrew

    2010-07-15

    Purpose: This study characterizes the dosimetric properties of the iBEAM evo carbon fiber couch manufactured by Medical Intelligence and examines the accuracy of the CMS XiO and Nucletron Oncentra Masterplan (OMP) treatment planning systems for calculating beam attenuation due to the presence of the couch. Methods: To assess the homogeneity of the couch, it was CT scanned at isocentric height and a number of signal intensity profiles were generated and analyzed. To simplify experimental procedures, surface dose and central axis depth dose measurements were performed in a solid water slab phantom using Gafchromic film for 6 and 10 MV photon beams at gantry angles of 0 deg. (normal incidence), 30 deg., and 60 deg. with an inverted iBEAM couch placed on top of the phantom. Attenuation measurements were performed in a cylindrical solid water phantom with an ionization chamber positioned at the isocenter. Measurements were taken for gantry angles from 0 deg. to 90 deg. in 10 deg. increments for both 6 and 10 MV photon beams. This setup was replicated in the XiO and OMP treatment planning systems. Dose was calculated using the pencil beam, collapsed cone, convolution, and superposition algorithms. Results: The CT scan of the couch showed that it was uniformly constructed. Surface dose increased by (510{+-}30)% for a 6 MV beam and (600{+-}20)% for a 10 MV beam passing through the couch at normal incidence. Obliquely incident beams resulted in a higher surface dose compared to normally incident beams for both open fields and fields with the couch present. Depth dose curves showed that the presence of the couch resulted in an increase in dose in the build up region. For 6 and 10 MV beams incident at 60 deg., nearly all skin sparing was lost. Attenuation measurements derived using the ionization chamber varied from 2.7% (0 deg.) to a maximum of 4.6% (50 deg.) for a 6 MV beam and from 1.9% (0 deg.) to a maximum of 4.0% (50 deg.) for a 10 MV beam. The pencil beam and

  6. Prostate brachytherapy postimplant dosimetry: Seed orientation and the impact of dosimetric anisotropy in stranded implants

    SciTech Connect

    Chng, Nicholas; Spadinger, Ingrid; Rasoda, Rosey; Morris, W. James; Salcudean, Septimiu

    2012-02-15

    Purpose: In postimplant dosimetry for prostate brachytherapy, dose is commonly calculated using the TG-43 1D formalism, because seed orientations are difficult to determine from CT images, the current standard for the procedure. However, the orientation of stranded seeds soon after implantation is predictable, as these seeds tend to maintain their relative spacing, and orient themselves along the implant trajectory. The aim of this study was to develop a method for determining seed orientations from reconstructed strand trajectories, and to use this information to investigate the dosimetric impact of applying the TG-43 2D formalism to clinical postimplant analysis. Methods: Using in-house software, the preplan to postimplant seed correspondence was determined for a cohort of 30 patients during routine day-0 CT-based postimplant dosimetry. All patients were implanted with stranded-seed trains. Spline curves were fit to each set of seeds composing a strand, with the requirement that the distance along the spline between seeds be equal to the seed spacing within the strand. The orientations of the seeds were estimated by the tangents to the spline at each seed centroid. Dose distributions were then determined using the 1D and 2D TG-43 formalisms. These were compared using the TG-137 recommended dose metrics for the prostate, prostatic urethra, and rectum. Results: Seven hundred and sixty one strands were analyzed in total. Defining the z-axis to be cranial-positive and the x-axis to be left-lateral positive in the CT coordinate system, the average seed had an inclination of 21 deg. {+-} 10 deg. and an azimuth of -81 deg. {+-} 57 deg. These values correspond to the average strand rising anteriorly from apex to base, approximately parallel to the midsagittal plane. Clinically minor but statistically significant differences in dose metrics were noted. Compared to the 2D calculation, the 1D calculation underestimated prostate V100 by 1.1% and D90 by 2.3 Gy, while

  7. Dosimetric impact of image artifact from a wide-bore CT scanner in radiotherapy treatment planning

    SciTech Connect

    Wu, Vincent; Podgorsak, Matthew B.; Tran, Tuan-Anh; Malhotra, Harish K.; Wang, Iris Z.

    2011-07-15

    Purpose: Traditional computed tomography (CT) units provide a maximum scan field-of-view (sFOV) diameter of 50 cm and a limited bore size, which cannot accommodate a large patient habitus or an extended simulation setup in radiation therapy (RT). Wide-bore CT scanners with increased bore size were developed to address these needs. Some scanners have the capacity to reconstruct the CT images at an extended FOV (eFOV), through data interpolation or extrapolation, using projection data acquired with a conventional sFOV. Objects that extend past the sFOV for eFOV reconstruction may generate image artifacts resulting from truncated projection data; this may distort CT numbers and structure contours in the region beyond the sFOV. The purpose of this study was to evaluate the dosimetric impact of image artifacts from eFOV reconstruction with a wide-bore CT scanner in radiotherapy (RT) treatment planning. Methods: Testing phantoms (i.e., a mini CT phantom with equivalent tissue inserts, a set of CT normal phantoms and anthropomorphic phantoms of the thorax and the pelvis) were used to evaluate eFOV artifacts. Reference baseline images of these phantoms were acquired with the phantom centrally positioned within the sFOV. For comparison, the phantoms were then shifted laterally and scanned partially outside the sFOV, but still within the eFOV. Treatment plans were generated for the thoracic and pelvic anthropomorphic phantoms utilizing the Eclipse treatment planning system (TPS) to study the potential effects of eFOV artifacts on dose calculations. All dose calculations of baseline and test treatment plans were carried out using the same MU. Results: Results show that both body contour and CT numbers are altered by image artifacts in eFOV reconstruction. CT number distortions of up to -356 HU for bone tissue and up to 323 HU for lung tissue were observed in the mini CT phantom. Results from the large body normal phantom, which is close to a clinical patient size, show

  8. Principles of electroanatomic mapping.

    PubMed

    Bhakta, Deepak; Miller, John M

    2008-01-01

    Electrophysiologic testing and radiofrequency ablation have evolved as curative measures for a variety of rhythm disturbances. As experience in this field has grown, ablation is progressively being used to address more complex rhythm disturbances. Paralleling this trend are technological advancements to facilitate these efforts, including electroanatomic mapping (EAM). At present, several different EAM systems utilizing various technologies are available to facilitate mapping and ablation. Use of these systems has been shown to reduce fluoroscopic exposure and radiation dose, with less significant effects on procedural duration and success rates. Among the data provided by EAM are chamber reconstruction, tagging of important anatomic landmarks and ablation lesions, display of diagnostic and mapping catheters without using fluoroscopy, activation mapping, and voltage (or scar) mapping. Several EAM systems have specialized features, such as enhanced ability to map non-sustained or hemodynamically unstable arrhythmias, ability to display diagnostic as well as mapping catheter positions, and wide compatibility with a variety of catheters. Each EAM system has its strengths and weaknesses, and the system chosen must depend upon what data is required for procedural success (activation mapping, substrate mapping, cardiac geometry), the anticipated arrhythmia, the compatibility of the system with adjunctive tools (i.e. diagnostic and ablation catheters), and the operator's familiarity with the selected system. While EAM can offer significant assistance during an EP procedure, their incorrect or inappropriate application can substantially hamper mapping efforts and procedural success, and should not replace careful interpretation of data and strict adherence to electrophysiologic principles.

  9. Estimation of electromagnetic dosimetric values from non-ionizing radiofrequency fields in an indoor commercial airplane environment.

    PubMed

    Aguirre, Erik; Arpón, Javier; Azpilicueta, Leire; López, Peio; de Miguel, Silvia; Ramos, Victoria; Falcone, Francisco

    2014-12-01

    In this article, the impact of topology as well as morphology of a complex indoor environment such as a commercial aircraft in the estimation of dosimetric assessment is presented. By means of an in-house developed deterministic 3D ray-launching code, estimation of electric field amplitude as a function of position for the complete volume of a commercial passenger airplane is obtained. Estimation of electromagnetic field exposure in this environment is challenging, due to the complexity and size of the scenario, as well as to the large metallic content, giving rise to strong multipath components. By performing the calculation with a deterministic technique, the complete scenario can be considered with an optimized balance between accuracy and computational cost. The proposed method can aid in the assessment of electromagnetic dosimetry in the future deployment of embarked wireless systems in commercial aircraft.

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

    SciTech Connect

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

    2012-03-15

    Purpose: 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. Methods: Inversely optimized arc radiotherapy plans were created on CT-data of three lung cancer patients. For each case, five plans with a single 358 deg. 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 x 30, used 6 MV, a maximum dose rate of 600 MU/min and a collimator angle of 45 deg. or 315 deg. 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

  11. Dosimetric quality assurance of highly conformal external beam treatments: from 2D phantom comparisons to 4D patient dose reconstruction

    NASA Astrophysics Data System (ADS)

    Feygelman, V.; Nelms, B.

    2013-06-01

    As IMRT technology continues to evolve, so do the dosimetric QA methods. A historical review of those is presented, starting with longstanding techniques such as film and ion chamber in a phantom and progressing towards 3D and 4D dose reconstruction in the patient. Regarding patient-specific QA, we envision that the currently prevalent limited comparison of dose distributions in the phantom by γ-analysis will be eventually replaced by clinically meaningful patient dose analyses with improved sensitivity and specificity. In a larger sense, we envision a future of QA built upon lessons from the rich history of "quality" as a science and philosophy. This future will aim to improve quality (and ultimately reduce cost) via advanced commissioning processes that succeed in detecting and rooting out systematic errors upstream of patient treatment, thus reducing our reliance on, and the resource burden associated with, per-beam/per-plan inspection.

  12. [The method based on generalized dosimetric function for estimation of cosmonauts' radiation hazard during long-term space missions].

    PubMed

    Shafirkin, A V; Grigor'ev, Iu G

    2002-01-01

    This paper presents a method of assessment of radiation hazard for cosmonauts. The method is based on a new dosimetric function, which enables a complicated nature of space radiation exposure to be reduced to the condition of a standard irradiation on Earth. It can be obtained on the basis of mean-tissue absorbed dose values calculated for each space radiation source, and transmission coefficients. The transmission coefficients define relative biological effectiveness of radiation and assess the influence on the radiobiological effects of the complex spatial and temporal distribution of the absorbed dose in the cosmonaut's body. The combination of cosmic ionizing radiation with other non-radiation nature factors in flight can be accounted. PMID:12449821

  13. An accelerator-based epithermal neutron beam design for BNCT and dosimetric evaluation using a voxel head phantom.

    PubMed

    Lee, Deok-jae; Han, Chi Young; Park, Sung Ho; Kim, Jong Kyung

    2004-01-01

    The beam shaping assembly design has been investigated in order to improve the epithermal neutron beam for accelerator-based boron neutron capture therapy in intensity and quality, and dosimetric evaluation for the beams has been performed using both mathematical and voxel head phantoms with MCNP runs. The neutron source was assumed to be produced from a conventional 2.5 MeV proton accelerator with a thick (7)Li target. The results indicate that it is possible to enhance epithermal neutron flux remarkably as well as to embody a good spectrum shaping to epithermal neutrons only with the proper combination of moderator and reflector. It is also found that a larger number of thermal neutrons can reach deeply into the brain and, therefore, can reduce considerably the treatment time for brain tumours. Consequently, the epithermal neutron beams designed in this study can treat more effectively deep-seated brain tumours.

  14. Determination of dosimetric perturbations caused by aneurysm clip in stereotactic radiosurgery using gel phantoms and EBT-Gafchromic films

    SciTech Connect

    Geso, M.; Ackerly, T.; Brown, S.; Chua, Z.; He, C.; Wong, C. J.; Powell, C. E.; Ho, A.; Qiao, G.; Solomon, D. H.; Patterson, W.; Droege, J. M.

    2008-02-15

    Some radiotherapy patients are treated with titanium surgical aneurysm clips in the radiation field. This is of particular importance for stereotactic radiosurgery brain treatments, where the length of the blade of the clip may be comparable to the size of the radiation field. This study seeks to determine the extent of the dosimetric effects caused by surgical clips in stereotactic radiosurgery, using polyacrylamide gel phantoms and EBT type Gafchromic films. Using gel phantoms scanned with magnetic resonance imaging scanner, dose enhancement of around 20% was noted at distances less than 2 mm away from the clip surface. Gafchromic films showed about 6% variations in the dose up to few millimeters from the clip. These experimental results confirmed results predicted by Monte Carlo simulation techniques for higher density material surgical clips such as lead and platinum. Moreover, these experimental measurements clearly indicate dose reduction due to radiation attenuation behind the clip of about 4%.

  15. Dosimetric evaluation of integrated IMRT treatment of the chest wall and supraclavicular region for breast cancer after modified radical mastectomy

    SciTech Connect

    Yang, Bo; Wei, Xian-ding; Zhao, Yu-tian; Ma, Chang-Ming

    2014-07-01

    To investigate the dosimetric characteristics of irradiation of the chest wall and supraclavicular region as an integrated volume with intensity-modulated radiation therapy (IMRT) after modified radical mastectomy. This study included 246 patients who received modified radical mastectomy. The patients were scanned with computed tomography, and the chest wall (with or without the internal mammary lymph nodes) and supraclavicular region were delineated. For 143 patients, the chest wall and supraclavicular region were combined as an integrated planning volume and treated with IMRT. For 103 patients, conventional treatments were employed with 2 tangential fields for the chest wall, abutting a mixed field of 6-MV x-rays (16 Gy) and 9-MeV electrons (34 Gy) for the upper supraclavicular region. The common prescription dose was 50 Gy/25 Fx/5 W to 90% of the target volume. The dosimetric characteristics of the chest wall, the supraclavicular region, and normal organs were compared. For the chest wall target, compared with conventional treatments, the integrated IMRT plans lowered the maximum dose, increased the minimum dose, and resulted in better conformity and uniformity of the target volume. There was an increase in minimum, average, and 95% prescription dose for the integrated IMRT plans in the supraclavicular region, and conformity and uniformity were improved. The V{sub 30} of the ipsilateral lung and V{sub 10}, V{sub 30}, and mean dose of the heart on the integrated IMRT plans were lower than those of the conventional plans. The V{sub 5} and V{sub 10} of the ipsilateral lung and V{sub 5} of the heart were higher on the integrated IMRT plans (p < 0.05) than on conventional plans. Without an increase in the radiation dose to organs at risk, the integrated IMRT treatment plans improved the dose distribution of the supraclavicular region and showed better dose conformity and uniformity of the integrated target volume of the chest wall and supraclavicular region.

  16. SU-E-T-138: Dosimetric Verification For Volumetric Modulated Arc Therapy Cranio-Spinal Irradiation Technique

    SciTech Connect

    Goksel, E; Bilge, H; Yildiz, Yarar

    2014-06-01

    Purpose: Dosimetric feasibility of cranio-spinal irradiation with volumetric modulated arc therapy (VMAT-CSI) technique in terms of dose distribution accuracy was investigated using a humanlike phantom. Methods: The OARs and PTV volumes for the Rando phantom were generated on supine CT images. Eclipse (version 8.6) TPS with AAA algorithm was used to create the treatment plan with VMAT-CSI technique. RapidArc plan consisted of cranial, upper spinal (US) and lower spinal (LS) regions that were optimized in the same plan. US field was overlapped by 3cm with cranial and LS fields. Three partial arcs for cranium and 1 full arc for each US and LS region were used. The VMAT-CSI dose distribution inside the Rando phantom was measured with thermoluminescent detectors (TLD) and film dosimetry, and was compared to the calculated doses of field junctions, target and OARs. TLDs were placed at 24 positions throughout the phantom. The measured TLD doses were compared to the calculated point doses. Planar doses for field junctions were verified with Gafchromic films. Films were analyzed in PTW Verisoft application software using gamma analysis method with the 4 mm distance to agreement (DTA) and 4% dose agreement criteria. Results: TLD readings demonstrated accurate dose delivery, with a median dose difference of -0.3% (range: -8% and 12%) when compared with calculated doses for the areas inside the treatment portal. The maximum dose difference was 12% higher in testicals that are outside the treatment region and 8% lower in lungs where the heterogeinity was higher. All planar dose verifications for field junctions passed the gamma analysis and measured planar dose distributions demonstrated average 97% agreement with calculated doses. Conclusion: The dosimetric data verified with TLD and film dosimetry shows that VMAT-CSI technique provides accurate dose distribution and can be delivered safely.

  17. Is there room for combined modality treatments? Dosimetric comparison of boost strategies for advanced head and neck and prostate cancer.

    PubMed

    Góra, Joanna; Hopfgartner, Johannes; Kuess, Peter; Paskeviciute, Brigita; Georg, Dietmar

    2013-07-01

    The purpose of the study was to determine the dosimetric difference between three emerging treatment modalities--volumetric-modulated arc therapy (VMAT), intensity-modulated proton beam therapy (IMPT) and intensity-modulated carbon ion beam therapy (IMIT)--for two tumour sites where selective boosting of the tumour is applied. For 10 patients with locally advanced head and neck (H&N) cancer and 10 with high-risk prostate cancer (PC) a VMAT plan was generated for PTV initial that included lymph node regions, delivering 50 Gy (IsoE) for H&N and 50.4 Gy (IsoE) for PC patients. Furthermore, separate boost plans (VMAT, IMPT and IMIT) were created to boost PTV boost up to 70 Gy (IsoE) and 78 Gy (IsoE) for H&N and PC cases, respectively. Doses to brainstem, myelon, larynx and parotid glands were assessed for H&N cases. Additionally, various OARs (e.g. cochlea, middle ear, masticator space) were evaluated that are currently discussed with respect to quality of life after treatment. For PC cases, bladder, rectum and femoral heads were considered as OARs. For both tumour sites target goals were easily met. Looking at OAR sparing, generally VMAT + VMAT was worst. VMAT + IMIT had the potential to spare some structures in very close target vicinity (such as cochlea, middle ear, masticator space ) significantly better than VMAT + IMPT. Mean doses for rectal and bladder wall were on average 4 Gy (IsoE) and 1.5 Gy (IsoE) higher, respectively, compared to photons plus particles scenarios. Similar results were found for parotid glands and larynx. Concerning target coverage, no significant differences were observed between the three treatment concepts. Clear dosimetric benefits were observed for particle beam therapy as boost modality. However, the clinical benefit of combined modality treatments remains to be demonstrated.

  18. The dosimetric impact of different photon beam energy on RapidArc radiotherapy planning for cervix carcinoma

    PubMed Central

    Kumar, Lalit; Yadav, Girigesh; Raman, Kothanda; Bhushan, Manindra; Pal, Manoj

    2015-01-01

    The main purpose of this study is to know the effect of three different photon energies viz., 6, 10, and 15 mega voltage (MV) on RapidArc (RA) planning for deep-seated cervix tumor and to develop clinically acceptable RA plans with suitable photon energy. RA plans were generated for 6, 10, and 15 MV photon energies for twenty patients reported with cervix carcinoma. RA plans were evaluated in terms of planning target volume (PTV) coverage, dose to organs at risk (OARs), conformity index (CI), homogeneity index (HI), gradient measure, external volume index of dose distribution produced, total number of monitor units (MUs), nontumor integral dose (ID), and low dose volume of normal tissue. A two-sample paired t-test was performed to compare the dosimetric parameters of RA plans. Irrespective of photon energy used for RA planning, plans were dosimetrically similar in terms of PTV coverage, OARs sparing, CI and HI. The numbers of MUs were 13.4 ± 1.4% and 18.2 ± 1.5% higher and IDs were 2.7 ± 0.8% and 3.7 ± 0.9% higher in 6 MV plans in comparison to that in the 10 and 15 MV plans, respectively. V1Gy, V2Gy, V3Gy, and V4Gy were higher in 6 MV plans in comparison to that in 10 and 15 MV plans. Based on this study, 6 MV photon beam is a good choice for RA planning in case of cervix carcinoma, as it does not deliver additional exposure to patients caused by photoneutrons produced in high energy beams. PMID:26865756

  19. Dosimetric comparison of proton and photon three-dimensional, conformal, external beam accelerated partial breast irradiation techniques

    SciTech Connect

    Kozak, Kevin R.; Katz, Angela; Adams, Judith C.; Crowley, Elizabeth M.; Nyamwanda, Jacqueline A.C.; Feng, Jennifer K.C.; Doppke, Karen P.; DeLaney, Thomas F.; Taghian, Alphonse G. . E-mail: ataghian@partners.org

    2006-08-01

    Purpose: To compare the dosimetry of proton and photon-electron three-dimensional, conformal, external beam accelerated partial breast irradiation (3D-CPBI). Methods and Materials: Twenty-four patients with fully excised, Stage I breast cancer treated with adjuvant proton 3D-CPBI had treatment plans generated using the mixed-modality, photon-electron 3D-CPBI technique. To facilitate dosimetric comparisons, planning target volumes (PTVs; lumpectomy site plus 1.5-2.0 cm margin) and prescribed dose (32 Gy) were held constant. Plans were optimized for PTV coverage and normal tissue sparing. Results: Proton and mixed-modality plans both provided acceptable PTV coverage with 95% of the PTV receiving 90% of the prescribed dose in all cases. Both techniques also provided excellent dose homogeneity with a dose maximum exceeding 110% of the prescribed dose in only one case. Proton 3D-CPBI reduced the volume of nontarget breast tissue receiving 50% of the prescribed dose by an average of 36%. Statistically significant reductions in the volume of total ipsilateral breast receiving 100%, 75%, 50%, and 25% of the prescribed dose were also observed. The use of protons resulted in small, but statistically significant, reductions in the radiation dose delivered to 5%, 10%, and 20% of ipsilateral and contralateral lung and heart. The nontarget breast tissue dosimetric advantages of proton 3D-CPBI were not dependent on tumor location, breast size, PTV size, or the ratio of PTV to breast volume. Conclusions: Compared to photon-electron 3D-CPBI, proton 3D-CPBI significantly reduces the volume of irradiated nontarget breast tissue. Both approaches to accelerated partial breast irradiation offer exceptional lung and heart sparing.

  20. Dosimetric comparisons of carbon ion treatment plans for 1D and 2D ripple filters with variable thicknesses

    NASA Astrophysics Data System (ADS)

    Printz Ringbæk, Toke; Weber, Uli; Santiago, Alina; Simeonov, Yuri; Fritz, Peter; Krämer, Michael; Wittig, Andrea; Bassler, Niels; Engenhart-Cabillic, Rita; Zink, Klemens

    2016-06-01

    A ripple filter (RiFi)—also called mini-ridge filter—is a passive energy modulator used in particle beam treatments that broadens the Bragg peak (BP) as a function of its maximum thickness. The number of different energies requested from the accelerator can thus be reduced, which significantly reduces the treatment time. A new second generation RiFi with 2D groove shapes was developed using rapid prototyping, which optimizes the beam-modulating material and enables RiFi thicknesses of up to 6 mm. Carbon ion treatment plans were calculated using the standard 1D 3 mm thick RiFi and the new 4 and 6 mm 2D RiFis for spherical planning target volumes (PTVs) in water, eight stage I non-small cell lung cancer cases, four skull base chordoma cases and three prostate cancer cases. TRiP98 was used for treatment planning with facility-specific base data calculated with the Monte Carlo code SHIELD-HIT12A. Dose-volume-histograms, spatial dose distributions and dosimetric indexes were used for plan evaluation. Plan homogeneity and conformity of thinner RiFis were slightly superior to thicker RiFis but satisfactory results were obtained for all RiFis investigated. For the 6 mm RiFi, fine structures in the dose distribution caused by the larger energy steps were observed at the PTV edges, in particular for superficial and/or very small PTVs but performances for all RiFis increased with penetration depth due to straggling and scattering effects. Plans with the new RiFi design yielded for the studied cases comparable dosimetric results to the standard RiFi while the 4 and 6 mm RiFis lowered the irradiation time by 25–30% and 45–49%, respectively.

  1. Dosimetric Comparison of Intensity-Modulated Stereotactic Radiotherapy With Other Stereotactic Techniques for Locally Recurrent Nasopharyngeal Carcinoma

    SciTech Connect

    Kung, Shiris Wai Sum; Wu, Vincent Wing Cheung; Kam, Michael Koon Ming; Leung, Sing Fai; Yu, Brian Kwok Hung; Ngai, Dennis Yuen Kan; Wong, Simon Chun Fai; Chan, Anthony Tak Cheung

    2011-01-01

    Purpose: Locally recurrent nasopharyngeal carcinoma (NPC) patients can be salvaged by reirradiation with a substantial degree of radiation-related complications. Stereotactic radiotherapy (SRT) is widely used in this regard because of its rapid dose falloff and high geometric precision. The aim of this study was to examine whether the newly developed intensity-modulated stereotactic radiotherapy (IMSRT) has any dosimetric advantages over three other stereotactic techniques, including circular arc (CARC), static conformal beam (SmMLC), and dynamic conformal arc (mARC), in treating locally recurrent NPC. Methods and Materials: Computed tomography images of 32 patients with locally recurrent NPC, previously treated with SRT, were retrieved from the stereotactic planning system for contouring and computing treatment plans. Treatment planning of each patient was performed for the four treatment techniques: CARC, SmMLC, mARC, and IMSRT. The conformity index (CI) and homogeneity index (HI) of the planning target volume (PTV) and doses to the organs at risk (OARs) and normal tissue were compared. Results: All four techniques delivered adequate doses to the PTV. IMSRT, SmMLC, and mARC delivered reasonably conformal and homogenous dose to the PTV (CI <1.47, HI <0.53), but not for CARC (p < 0.05). IMSRT presented with the smallest CI (1.37) and HI (0.40). Among the four techniques, IMSRT spared the greatest number of OARs, namely brainstem, temporal lobes, optic chiasm, and optic nerve, and had the smallest normal tissue volume in the low-dose region. Conclusion: Based on the dosimetric comparison, IMSRT was optimal for locally recurrent NPC by delivering a conformal and homogenous dose to the PTV while sparing OARs.

  2. Dosimetric evaluation of integrated IMRT treatment of the chest wall and supraclavicular region for breast cancer after modified radical mastectomy.

    PubMed

    Yang, Bo; Wei, Xian-Ding; Zhao, Yu-Tian; Ma, Chang-Ming

    2014-01-01

    To investigate the dosimetric characteristics of irradiation of the chest wall and supraclavicular region as an integrated volume with intensity-modulated radiation therapy (IMRT) after modified radical mastectomy. This study included 246 patients who received modified radical mastectomy. The patients were scanned with computed tomography, and the chest wall (with or without the internal mammary lymph nodes) and supraclavicular region were delineated. For 143 patients, the chest wall and supraclavicular region were combined as an integrated planning volume and treated with IMRT. For 103 patients, conventional treatments were employed with 2 tangential fields for the chest wall, abutting a mixed field of 6-MV x-rays (16Gy) and 9-MeV electrons (34Gy) for the upper supraclavicular region. The common prescription dose was 50Gy/25Fx/5W to 90% of the target volume. The dosimetric characteristics of the chest wall, the supraclavicular region, and normal organs were compared. For the chest wall target, compared with conventional treatments, the integrated IMRT plans lowered the maximum dose, increased the minimum dose, and resulted in better conformity and uniformity of the target volume. There was an increase in minimum, average, and 95% prescription dose for the integrated IMRT plans in the supraclavicular region, and conformity and uniformity were improved. The V30 of the ipsilateral lung and V10, V30, and mean dose of the heart on the integrated IMRT plans were lower than those of the conventional plans. The V5 and V10 of the ipsilateral lung and V5 of the heart were higher on the integrated IMRT plans (p < 0.05) than on conventional plans. Without an increase in the radiation dose to organs at risk, the integrated IMRT treatment plans improved the dose distribution of the supraclavicular region and showed better dose conformity and uniformity of the integrated target volume of the chest wall and supraclavicular region.

  3. Dosimetric modeling of the microselectron high-dose rate 192Ir source by the multigroup discrete ordinates method.

    PubMed

    Daskalov, G M; Baker, R S; Rogers, D W; Williamson, J F

    2000-10-01

    The DANTSYS multigroup discrete ordinates computer code is applied to quantitatively estimate the absorbed dose rate distributions in the vicinity of a microSelectron 192Ir high-dose-rate (HDR) source in two-dimensional cylindrical R-Z geometry. The source is modeled in a cylindrical water phantom of diameter 20 cm and height 20 cm. The results are also used for evaluation of the Task Group 43 (TG-43) dosimetric quantities. The DANTSYS accuracy is estimated by direct comparisons with corresponding Monte Carlo results. Our 210-group photon cross section library developed previously, together with angular quadratures consisting of 36 (S16) to 210 (S40) directions and associated weights per octant, are used in the DANTSYS simulations. Strong ray effects are observed but are significantly mitigated through the use of DANTSYS's stochastic ray-tracing first collision source algorithm. The DANTSYS simulations closely approximate Monte Carlo estimates of both direct dose calculations and TG-43 dosimetric quantities. The discrepancies with S20 angular quadrature (55 directions and weights per octant) or higher are shown to be less than +/- 5% (about 2.5 standard deviations of Monte Carlo calculations) everywhere except for limited regions along the Z axis of rotational symmetry, where technical limitations in the DANTSYS first collision source implementation makes adequate suppression of ray effects difficult to achieve. The efficiency of DANTSYS simulations is compared with that of the EGS4 Monte Carlo code. It is demonstrated that even with the 210-group cross section library, DANTSYS achieves two-fold efficiency gains using the the S20 quadrature set. The potential of discrete ordinates method for further efficiency improvements is also discussed. PMID:11099199

  4. Internal radiotherapy and dosimetric study for 111In/ 177Lu-pegylated liposomes conjugates in tumor-bearing mice

    NASA Astrophysics Data System (ADS)

    Wang, Hsin-Ell; Yu, Hung-Man; Lu, Yi-Ching; Heish, Ning-Ning; Tseng, Yun-Long; Huang, Kuang-Liang; Chuang, Kuo-Tang; Chen, Chin-Hsiung; Hwang, Jeng-Jong; Lin, Wuu-Jyh; Wang, Shyh-Jen; Ting, Gann; Whang-Peng, Jacqueline; Deng, Win-Ping

    2006-12-01

    In vivo characterization and dosimetric analysis has been performed to evaluate the potential of pegylated liposomes as carriers of radionuclides in tumor internal radiotherapy. MethodsThe DTPA/PEG-liposomes were synthesized with a medium size of 110 nm, conjugated with 111In/ 177Lu-(oxine) 3 to afford 111In/ 177Lu-liposome. The stability of 111In/ 177Lu-liposome in serum was investigated. The biodistribution, scintigraphic imaging and pharmacokinetics of 111In/ 177Lu-liposomes after intravenous(i.v.) injection into C-26 tumor-bearing BALB/cByJ mice were studied. Radiation dose was estimated by MIRD-III program. ResultsThe incorporation efficiency of 111In/ 177Lu into liposomes was 95%. After incubation at 37 °C for 72 h in serum, more than 83% of radioactivity was still retained in the intact 111In/ 177Lu-liposomes. The biodistribution of 111In-liposomes showed that the radioactivity in the blood decreased from 23.14±8.16%ID/g at 1 h to 0.02±0.00%ID/g at 72 h post-injection (p.i.), while reaching its maximum accumulation in tumors at 48 h p.i., with half-life in blood of 10.2 h. The results were supported by that of 177Lu-liposomes. Scintigraphic imaging with 111In-liposomes showed unambiguous tumor images at 48 h p.i. Dose estimation showed that the absorbed dose in tumor from 177Lu-liposomes was 5.74×10 -5 Gy/MBq. ConclusionsThis study provides an in vivo characterization and dosimetric evaluation for the use of liposome systems as carriers in targeted radionuclide therapy. The results suggest that adequate tumor targeting as well as dose delivered to tumors could be achieved by the use of radionuclide targeted liposomes.

  5. Dosimetric and technical aspects of intraoperative I-125 brachytherapy for stage I non-small cell lung cancer.

    PubMed

    Johnson, Mark; Colonias, Athanasios; Parda, David; Trombetta, Mark; Gayou, Olivier; Reitz, Bodo; Miften, Moyed

    2007-03-01

    Initial treatment outcome data from our institution for stage I non-small cell lung cancer (NSCLC) patients have shown that sublobar resection in combination with iodine-125 (I-125) brachytherapy is associated with recurrence rates of 2.0%, compared to 18.6% with sublobar resection alone. In this work, the technical and dosimetric aspects required to execute this procedure from the radiation oncology perspective as well as an analysis of the dose distributions of patients treated with this technique are presented. In this treatment technique, I-125 seeds in vicryl suture are embedded into vicryl mesh and surgically inserted providing a 2.0 cm margin on each side of the resection staple line. A nomogram is developed to determine the suture spacing in the vicryl mesh, as a function of seed activity in order to deliver 120 Gy at a distance of 0.5 cm above and below the seed array. Post-operative dosimetry consists of a CT-based planning and dose volume analysis. Dose distributions, dose volume histograms and mean dose data for lung are analysed in a group of patients. Dosimetric results show significant lung sparing with only a small volume of lung irradiated for all patients with mean lung dose values ranging from 1.5 Gy to 5.4 Gy. Lung brachytherapy with I-125 at the time of sublobar resection is a highly conformal option of dose delivery for stage I NSCLC patients with compromised physiologic reserve. Patient-related toxicity clinically measured by loss of pulmonary function and radiation-induced pneumonitis have not been linked to this procedure.

  6. Dosimetric and technical aspects of intraoperative I-125 brachytherapy for stage I non-small cell lung cancer

    NASA Astrophysics Data System (ADS)

    Johnson, Mark; Colonias, Athanasios; Parda, David; Trombetta, Mark; Gayou, Olivier; Reitz, Bodo; Miften, Moyed

    2007-03-01

    Initial treatment outcome data from our institution for stage I non-small cell lung cancer (NSCLC) patients have shown that sublobar resection in combination with iodine-125 (I-125) brachytherapy is associated with recurrence rates of 2.0%, compared to 18.6% with sublobar resection alone. In this work, the technical and dosimetric aspects required to execute this procedure from the radiation oncology perspective as well as an analysis of the dose distributions of patients treated with this technique are presented. In this treatment technique, I-125 seeds in vicryl suture are embedded into vicryl mesh and surgically inserted providing a 2.0 cm margin on each side of the resection staple line. A nomogram is developed to determine the suture spacing in the vicryl mesh, as a function of seed activity in order to deliver 120 Gy at a distance of 0.5 cm above and below the seed array. Post-operative dosimetry consists of a CT-based planning and dose volume analysis. Dose distributions, dose volume histograms and mean dose data for lung are analysed in a group of patients. Dosimetric results show significant lung sparing with only a small volume of lung irradiated for all patients with mean lung dose values ranging from 1.5 Gy to 5.4 Gy. Lung brachytherapy with I-125 at the time of sublobar resection is a highly conformal option of dose delivery for stage I NSCLC patients with compromised physiologic reserve. Patient-related toxicity clinically measured by loss of pulmonary function and radiation-induced pneumonitis have not been linked to this procedure.

  7. Improved Dosimetric and Clinical Outcomes With Intensity-Modulated Radiotherapy for Head-and-Neck Cancer of Unknown Primary Origin

    SciTech Connect

    Chen, Allen M.; Li Baoqing; Farwell, D. Gregory; Marsano, Joseph; Vijayakumar, Srinivasan; Purdy, James A.

    2011-03-01

    Purpose: To compare differences in dosimetric, clinical, and quality-of-life endpoints among a cohort of patients treated by intensity-modulated radiotherapy (IMRT) and conventional radiotherapy (CRT) for head-and-neck cancer of unknown primary origin. Methods and Materials: The medical records of 51 patients treated by radiation therapy for squamous cell carcinoma of the head and neck presenting as cervical lymph node metastasis of occult primary origin were reviewed. Twenty-four patients (47%) were treated using CRT, and 27 (53%) were treated using IMRT. The proportions of patients receiving concurrent chemotherapy were 54% and 63%, respectively. Results: The 2-year estimates of overall survival, local-regional control, and disease-specific survival for the entire patient population were 86%, 89%, and84%, respectively. There were no significant differences in any of these endpoints with respect to radiation therapy technique (p > 0.05 for all). Dosimetric analysis revealed that the use of IMRT resulted in significant improvements with respect to mean dose and V30 to the contralateral (spared) parotid gland. In addition, mean doses to the ipsilateral inner and middle ear structures were significantly reduced with IMRT (p < 0.05 for all). The incidence of severe xerostomia in the late setting was 58% and 11% among patients treated by CRT and IMRT, respectively (p < 0.001). The percentages of patients who were G-tube dependent at 6 months after treatment were 42% and 11%, respectively (p < 0.001). Conclusions: IMRT results in significant improvements in the therapeutic ratio among patients treated by radiation therapy for head-and-neck cancer of unknown primary origin.

  8. SU-D-19A-07: Dosimetric Comparison of HDR Plesiotherapy and Electron Beam Therapy for Superficial Lesions

    SciTech Connect

    Mitchell, A; Jacob, D; Andreou, K; Raben, A; Chen, H; Koprowski, C; Mourtada, F

    2014-06-01

    Purpose: Large superficial (skin, soft tissue sarcoma) lesions located on curved areas are hard to treat with electrons. The Freiburg Flap (Nucletron, Netherlands) is a flexible mesh style surface which can be easily shaped to fit curved surfaces for reproducible HDR fraction delivery. To understand the fundamental dosimetric differences, a dosimetric comparison was made between HDR plesiotherapy (Freiburg applicator for lesions over 4cm) and external electron beam radiotherapy over cases with varying target curvature (both stylized and clinical cases). Methods: Four stylized cases with variable complexity were created using artificial DICOM axial CT slices and RT structures (a square and three curved structures on a 4.5cm radius cylinder). They were planned using Oncentra v4.3 and exported to Pinnacle v9.6 for electrons planning. The HDR source dwell positions were optimized for the best coverage of the targets using graphical optimization. Electron treatment plans were created in Pinnacle using the same CT and RT structures of three HDR cases with surface lesions previously treated with the Freiburg flap. The En face electron plans used 6-12 MeV electrons and 0.5–1 cm bolus was added to increase surface dose. The electron plans were prescribed to an isodose line to conform to the target. Results: For all lesions, the average target dose coverage was similar (D90ave of 100% for HDR vs 101% for electrons). For lesions with high curvature, the HDR coverage was better (D90 102% vs D90 97% for electron). For all cases, adjacent structures high dose region was lower for HDR than electrons (D1cc 100% for HDR vs D1cc 111% for electrons). Conclusion: HDR plesiotherapy offers excellent target conformity for superficial targets similar to electrons. However, for lesions with complex curved surfaces, HDR has the advantage to achieve better dose distributions using graphical optimization to spare adjacent normal tissue while maximizing target coverage.

  9. Dosimetric comparisons of carbon ion treatment plans for 1D and 2D ripple filters with variable thicknesses.

    PubMed

    Ringbæk, Toke Printz; Weber, Uli; Santiago, Alina; Simeonov, Yuri; Fritz, Peter; Krämer, Michael; Wittig, Andrea; Bassler, Niels; Engenhart-Cabillic, Rita; Zink, Klemens

    2016-06-01

    A ripple filter (RiFi)-also called mini-ridge filter-is a passive energy modulator used in particle beam treatments that broadens the Bragg peak (BP) as a function of its maximum thickness. The number of different energies requested from the accelerator can thus be reduced, which significantly reduces the treatment time. A new second generation RiFi with 2D groove shapes was developed using rapid prototyping, which optimizes the beam-modulating material and enables RiFi thicknesses of up to 6 mm. Carbon ion treatment plans were calculated using the standard 1D 3 mm thick RiFi and the new 4 and 6 mm 2D RiFis for spherical planning target volumes (PTVs) in water, eight stage I non-small cell lung cancer cases, four skull base chordoma cases and three prostate cancer cases. TRiP98 was used for treatment planning with facility-specific base data calculated with the Monte Carlo code SHIELD-HIT12A. Dose-volume-histograms, spatial dose distributions and dosimetric indexes were used for plan evaluation. Plan homogeneity and conformity of thinner RiFis were slightly superior to thicker RiFis but satisfactory results were obtained for all RiFis investigated. For the 6 mm RiFi, fine structures in the dose distribution caused by the larger energy steps were observed at the PTV edges, in particular for superficial and/or very small PTVs but performances for all RiFis increased with penetration depth due to straggling and scattering effects. Plans with the new RiFi design yielded for the studied cases comparable dosimetric results to the standard RiFi while the 4 and 6 mm RiFis lowered the irradiation time by 25-30% and 45-49%, respectively. PMID:27203127

  10. Dosimetric accuracy of the cone-beam CT-based treatment planning of the Vero system: a phantom study.

    PubMed

    Yohannes, Indra; Prasetio, Heru; Kallis, Karoline; Bert, Christoph

    2016-01-01

    We report an investigation on the accuracy of dose calculation based on the cone-beam computed tomography (CBCT) images of the nonbowtie filter kV imaging system of the Vero linear accelerator. Different sets of materials and tube voltages were employed to generate the Hounsfield unit lookup tables (HLUTs) for both CBCT and fan-beam CT (FBCT) systems. The HLUTs were then implemented for the dose calculation in a treatment planning system (TPS). Dosimetric evaluation was carried out on an in-house-developed cube phantom that consists of water-equivalent slabs and inhomogeneity inserts. Two independent dosimeters positioned in the cube phantom were used in this study for point-dose and two-dimensional (2D) dose distribution measurements. The differences of HLUTs from various materials and tube voltages in both CT systems resulted in differences in dose calculation accuracy. We found that the higher the tube voltage used to obtain CT images, the better the point-dose calculation and the gamma passing rate of the 2D dose distribution agree to the values determined in the TPS. Moreover, the insert materials that are not tissue-equivalent led to higher dose-calculation inaccuracy. There were negligible differences in dosimetric evaluation between the CBCT- and FBCT-based treatment planning if the HLUTs were generated using the tissue-equivalent materials. In this study, the CBCT images of the Vero system from a complex inhomogeneity phantom can be applied for the TPS dose calculation if the system is calibrated using tissue-equivalent materials scanned at high tube voltage (i.e., 120 kV). PMID:27455496

  11. Portal imaging practice patterns of children's oncology group institutions: Dosimetric assessment and recommendations for minimizing unnecessary exposure

    SciTech Connect

    Olch, Arthur J. . E-mail: aolch@chla.usc.edu; Geurts, Mark; Thomadsen, Bruce; Famiglietti, Robin; Chang, Eric L.

    2007-02-01

    Purpose: To determine and analyze the dosimetric consequences of current portal imaging practices for pediatric patients, and make specific recommendations for reducing exposure from portal imaging procedures. Methods and Materials: A survey was sent to approximately 250 Children's Oncology Group (COG) member institutions asking a series of questions about their portal imaging practices. Three case studies are presented with dosimetric analysis to illustrate the magnitude of unintended dose received by nontarget tissues using the most common techniques from the survey. Results: The vast majority of centers use double-exposure portal image techniques with a variety of open field margins. Only 17% of portal images were obtained during treatment, and for other imaging methods, few centers subtract monitor units from the treatment delivery. The number of monitor units used was nearly the same regardless of imager type, including electronic portal imaging devices. Eighty-six percent imaged all fields the first week and 17% imaged all fields every week. An additional 1,112 cm{sup 3} of nontarget tissue received 1 Gy in one of the example cases. Eight new recommendations are made, which will lower nontarget radiation doses with minimal impact on treatment verification accuracy. Conclusion: Based on the survey, changes can be made in portal imaging practices that will lower nontarget doses. It is anticipated that treatment verification accuracy will be minimally affected. Specific recommendations made to decrease the imaging dose and help lower the rate of radiation-induced secondary cancers in children are proposed for inclusion in future COG protocols using radiation therapy.

  12. Evaluation of Dosimetric Consequences of Seroma Contour Variability in Accelerated Partial Breast Irradiation Using a Constructed Representative Seroma Contour

    SciTech Connect

    Kosztyla, Robert; Olson, Robert; Carolan, Hannah; Balkwill, Susan; Moiseenko, Vitali; Kwan, Winkle

    2012-10-01

    Purpose: Contouring variability of the seroma can have important implications in the planning and delivery of accelerated partial breast irradiation (APBI). This study aimed to quantify the dosimetric impact of these interobserver and intraobserver contouring variations by construction of a representative seroma contour (RSC). Methods and Materials: Twenty-one patients with a seroma suitable for APBI underwent four computed tomography (CT) scans: one planning CT and three additional CTs on the first, third, and fifth days of treatment. Three radiation oncologists contoured the seroma on each CT scan. For 3 patients, oncologists repeated contouring twice to assess intraobserver variations. Seroma contour variability was quantified by construction of an RSC. In addition, the percent volume overlap (PVO) was calculated. Root-mean-square (RMS) differences in seroma volume, size, and center of mass position compared to those of the RSC were calculated. Treatment fields from the original plan were applied to the repeated CTs by using the same isocenter shifts as the original plan. The dosimetric impact of the contour variations was assessed using V{sub 95} (volume receiving at least 95% of the prescribed dose) and equivalent uniform dose (EUD). Results: Interobserver RMS volume differences were, on average, 5.6 times larger than intraobserver differences. The median interobserver RMS seroma volume difference was 1.48 cm{sup 3}. The median PVO was 51.6%. V{sub 95} and EUD of the seroma contours were similar for all patients. The median RMS differences of the seroma V{sub 95} and EUD were 0.01% (range, 0%-3.99%) and 0.05 Gy (range, 0-0.98 Gy). Conclusions: Construction of the RSC showed that interobserver variations were most responsible for contour variations of the seroma. Current planning margins provided adequate dose coverage of the seroma despite these contour variations.

  13. Dosimetric Feasibility of Dose Escalation Using SBRT Boost for Stage III Non-Small Cell Lung Cancer

    PubMed Central

    Hepel, Jaroslaw T.; Peter, Justin; Hiatt, Jessica R.; Patel, Salil; Osibanjo, Oluwademilade; Safran, Howard; Curran, Bruce; DiPetrillo, Thomas

    2012-01-01

    Purpose: Standard chemoradiation therapy for stage III non-small cell lung cancer (NSCLCa) results in suboptimal outcomes with a high rate of local failure and poor overall survival. We hypothesize that dose escalation using stereotactic body radiotherapy (SBRT) boost could improve upon these results. We present here a study evaluating the dosimetric feasibility of such an approach. Methods: Anonymized CT data sets from five randomly selected patients with stage III NSCLCa undergoing definitive chemoradiation therapy in our department with disease volumes appropriate for SBRT boost were selected. Three-dimensional conformal radiation therapy (3D-CRT) plans to 50.4 Gy in 28 fractions were generated follow by SBRT plans to two dose levels, 16 Gy in two fractions and 28 Gy in two fractions. SBRT plans and total composite (3D-CRT and SBRT) were optimized and evaluated for target coverage and dose to critical structures; lung, esophagus, cord, and heart. Results: All five plans met predetermined target coverage and normal tissue dose constraints. PTV V95 was equal to or greater than 95% in all cases. The cumulative lung V20 and V5 of the combined 3D-CRT and SBRT plans were less than or equal to 30 and 55%, respectively. The 5 cc esophageal dose was less than 12 Gy for all low and high dose SBRT plans. The cumulative dose to the esophagus was also acceptable with less than 10% of the esophagus receiving doses in excess of 50 Gy. The cumulative spinal cord dose was less than 33 Gy and heart V25 was less than 5%. Conclusion: The combination of chemoradiation to 50.4 Gy followed by SBRT boost to gross disease at the primary tumor and involved regional lymph nodes is feasible with respect to normal tissue dose constraints in this dosimetric pilot study. A phase I/II trial to evaluate the clinical safety and efficacy of this approach is being undertaken. PMID:23057009

  14. Intrafraction Prostate Translations and Rotations During Hypofractionated Robotic Radiation Surgery: Dosimetric Impact of Correction Strategies and Margins

    SciTech Connect

    Water, Steven van de; Valli, Lorella; Aluwini, Shafak; Lanconelli, Nico; Heijmen, Ben; Hoogeman, Mischa

    2014-04-01

    Purpose: To investigate the dosimetric impact of intrafraction prostate motion and the effect of robot correction strategies for hypofractionated CyberKnife treatments with a simultaneously integrated boost. Methods and Materials: A total of 548 real-time prostate motion tracks from 17 patients were available for dosimetric simulations of CyberKnife treatments, in which various correction strategies were included. Fixed time intervals between imaging/correction (15, 60, 180, and 360 seconds) were simulated, as well as adaptive timing (ie, the time interval reduced from 60 to 15 seconds in case prostate motion exceeded 3 mm or 2° in consecutive images). The simulated extent of robot corrections was also varied: no corrections, translational corrections only, and translational corrections combined with rotational corrections up to 5°, 10°, and perfect rotational correction. The correction strategies were evaluated for treatment plans with a 0-mm or 3-mm margin around the clinical target volume (CTV). We recorded CTV coverage (V{sub 100%}) and dose-volume parameters of the peripheral zone (boost), rectum, bladder, and urethra. Results: Planned dose parameters were increasingly preserved with larger extents of robot corrections. A time interval between corrections of 60 to 180 seconds provided optimal preservation of CTV coverage. To achieve 98% CTV coverage in 98% of the treatments, translational and rotational corrections up to 10° were required for the 0-mm margin plans, whereas translational and rotational corrections up to 5° were required for the 3-mm margin plans. Rectum and bladder were spared considerably better in the 0-mm margin plans. Adaptive timing did not improve delivered dose. Conclusions: Intrafraction prostate motion substantially affected the delivered dose but was compensated for effectively by robot corrections using a time interval of 60 to 180 seconds. A 0-mm margin required larger extents of additional rotational corrections than a 3

  15. Dosimetric comparisons of carbon ion treatment plans for 1D and 2D ripple filters with variable thicknesses

    NASA Astrophysics Data System (ADS)

    Printz Ringbæk, Toke; Weber, Uli; Santiago, Alina; Simeonov, Yuri; Fritz, Peter; Krämer, Michael; Wittig, Andrea; Bassler, Niels; Engenhart-Cabillic, Rita; Zink, Klemens

    2016-06-01

    A ripple filter (RiFi)—also called mini-ridge filter—is a passive energy modulator used in particle beam treatments that broadens the Bragg peak (BP) as a function of its maximum thickness. The number of different energies requested from the accelerator can thus be reduced, which significantly reduces the treatment time. A new second generation RiFi with 2D groove shapes was developed using rapid prototyping, which optimizes the beam-modulating material and enables RiFi thicknesses of up to 6 mm. Carbon ion treatment plans were calculated using the standard 1D 3 mm thick RiFi and the new 4 and 6 mm 2D RiFis for spherical planning target volumes (PTVs) in water, eight stage I non-small cell lung cancer cases, four skull base chordoma cases and three prostate cancer cases. TRiP98 was used for treatment planning with facility-specific base data calculated with the Monte Carlo code SHIELD-HIT12A. Dose-volume-histograms, spatial dose distributions and dosimetric indexes were used for plan evaluation. Plan homogeneity and conformity of thinner RiFis were slightly superior to thicker RiFis but satisfactory results were obtained for all RiFis investigated. For the 6 mm RiFi, fine structures in the dose distribution caused by the larger energy steps were observed at the PTV edges, in particular for superficial and/or very small PTVs but performances for all RiFis increased with penetration depth due to straggling and scattering effects. Plans with the new RiFi design yielded for the studied cases comparable dosimetric results to the standard RiFi while the 4 and 6 mm RiFis lowered the irradiation time by 25-30% and 45-49%, respectively.

  16. SU-E-T-538: Lung SBRT Dosimetric Comparison of 3D Conformal and RapidArc Planning

    SciTech Connect

    Jiang, R; Zhan, L; Osei, E

    2015-06-15

    Purpose: Dose distributions of RapidArc Plan can be quite different from standard 3D conformal radiation therapy. SBRT plans can be optimized with high conformity or mimic the 3D conformal treatment planning with very high dose in the center of the tumor. This study quantifies the dosimetric differences among 3D conformal plan; flattened beam and FFF beam RapidArc Plans for lung SBRT. Methods: Five lung cancer patients treated with 3D non-coplanar SBRT were randomly selected. All the patients were CT scanned with 4DCT to determine the internal target volume. Abdominal compression was applied to minimize respiratory motion for SBRT patients. The prescription dose was 48 Gy in 4 fractions. The PTV coverage was optimized by two groups of objective function: one with high conformity, another mimicking 3D conformal dose distribution with high dose in the center of PTV. Optimization constraints were set to meet the criteria of the RTOG-0915 protocol. All VMAT plans were optimized with the RapidArc technique using four full arcs in Eclipse treatment planning system. The RapidArc SBRT plans with flattened 6MV beam and 6MV FFF beam were generated and dosimetric results were compared with the previous treated 3D non-coplanar plans. Results: All the RapidArc plans with flattened beam and FFF beam had similar results for the PTV and OARs. For the high conformity optimization group, The DVH of PTV exhibited a steep dose fall-off outside the PTV compared to the 3D non-coplanar plan. However, for the group mimicking the 3D conformal target dose distribution, although the PTV is very similar to the 3D conformal plan, the ITV coverage is better than 3D conformal plan. Conclusion: Due to excellent clinical experiences of 3D conformal SBRT treatment, the Rapid Arc optimization mimicking 3D conformal planning may be suggested for clinical use.

  17. SU-F-BRF-12: Investigating Dosimetric Effects of Inter-Fraction Deformation in Lung Cancer Stereotactic Body Radiotherapy (SBRT)

    SciTech Connect

    Jia, J; Tian, Z; Gu, X; Yan, H; Jia, X; Jiang, S

    2014-06-15

    Purpose: We studied dosimetric effects of inter-fraction deformation in lung stereotactic body radiotherapy (SBRT), in order to investigate the necessity of adaptive re-planning for lung SBRT treatments. Methods: Six lung cancer patients with different treatment fractions were retrospectively investigated. All the patients were immobilized and localized with a stereotactic body frame and were treated under cone-beam CT (CBCT) image guidance at each fraction. We calculated the actual delivered dose of the treatment plan using the up-to-date patient geometry of each fraction, and compared the dose with the intended plan dose to investigate the dosimetric effects of the inter-fraction deformation. Deformable registration was carried out between the treatment planning CT and the CBCT of each fraction to obtain deformed planning CT for more accurate dose calculations of the delivered dose. The extent of the inter-fraction deformation was also evaluated by calculating the dice similarity coefficient between the delineated structures on the planning CT and those on the deformed planning CT. Results: The average dice coefficients for PTV, spinal cord, esophagus were 0.87, 0.83 and 0.69, respectively. The volume of PTV covered by prescription dose was decreased by 23.78% on average for all fractions and all patients. For spinal cord and esophagus, the volumes covered by the constraint dose were increased by 4.57% and 3.83%. The maximum dose was also increased by 4.11% for spinal cord and 4.29% for esophagus. Conclusion: Due to inter-fraction deformation, large deterioration was found in both PTV coverage and OAR sparing, which demonstrated the needs for adaptive re-planning of lung SBRT cases to improve target coverage while reducing radiation dose to nearby normal tissues.

  18. A dosimetric comparison of two-phase adaptive intensity-modulated radiotherapy for locally advanced nasopharyngeal cancer

    PubMed Central

    Chitapanarux, Imjai; Chomprasert, Kittisak; Nobnaop, Wannapa; Wanwilairat, Somsak; Tharavichitkul, Ekasit; Jakrabhandu, Somvilai; Onchan, Wimrak; Traisathit, Patrinee; Van Gestel, Dirk

    2015-01-01

    The purpose of this investigation was to evaluate the potential dosimetric benefits of a two-phase adaptive intensity-modulated radiotherapy (IMRT) protocol for patients with locally advanced nasopharyngeal cancer (NPC). A total of 17 patients with locally advanced NPC treated with IMRT had a second computed tomography (CT) scan after 17 fractions in order to apply and continue the treatment with an adapted plan after 20 fractions. To simulate the situation without adaptation, a hybrid plan was generated by applying the optimization parameters of the original treatment plan to the anatomy of the second CT scan. The dose–volume histograms (DVHs) and dose statistics of the hybrid plan and the adapted plan were compared. The mean volume of the ipsilateral and contralateral parotid gland decreased by 6.1 cm3 (30.5%) and 5.4 cm3 (24.3%), respectively. Compared with the hybrid plan, the adapted plan provided a higher dose to the target volumes with better homogeneity, and a lower dose to the organs at risk (OARs). The Dmin of all planning target volumes (PTVs) increased. The Dmax of the spinal cord and brainstem were lower in 94% of the patients (1.6–5.9 Gy, P < 0.001 and 2.1–9.9 Gy, P < 0.001, respectively). The Dmean of the contralateral parotid decreased in 70% of the patients (range, 0.2–4.4 Gy). We could not find a relationship between dose variability and weight loss. Our two-phase adaptive IMRT protocol improves dosimetric results in terms of target volumes and OARs in patients with locally advanced NPC. PMID:25666189

  19. Dosimetric Factors Associated With Long-Term Dysphagia After Definitive Radiotherapy for Squamous Cell Carcinoma of the Head and Neck

    SciTech Connect

    Caudell, Jimmy J.; Schaner, Philip E.; Desmond, Renee A.; Meredith, Ruby F.; Spencer, Sharon A.; Bonner, James A.

    2010-02-01

    Purpose: Intensification of radiotherapy and chemotherapy for head-and-neck cancer may lead to increased rates of dysphagia. Dosimetric predictors of objective findings of long-term dysphagia were sought. Methods and Materials: From an institutional database, 83 patients were identified who underwent definitive intensity-modulated radiotherapy for squamous cell carcinoma of the head and neck, after exclusion of those who were treated for a second or recurrent head-and-neck primary lesion, had locoregional recurrence at any time, had less than 12 months of follow-up, or had postoperative radiotherapy. Dosimetric parameters were analyzed relative to three objective endpoints as a surrogate for severe long-term dysphagia: percutaneous endoscopic gastrostomy (PEG) tube dependence at 12 months, aspiration on modified barium swallow, or pharyngoesophageal stricture requiring dilation. Results: Mean dose greater than 41 Gy and volume receiving 60 Gy (V{sub 60}) greater than 24% to the larynx were significantly associated with PEG tube dependence and aspiration. V{sub 60} greater than 12% to the inferior pharyngeal constrictor was also significantly associated with increased PEG tube dependence and aspiration. V{sub 65} greater than 33% to the superior pharyngeal constrictor or greater than 75% to the middle pharyngeal constrictor was associated with pharyngoesophageal stricture requiring dilation. Conclusions: Doses to the larynx and pharyngeal constrictors predicted long-term swallowing complications, even when controlled for other clinical factors. The addition of these structures to intensity-modulated radiotherapy optimization may reduce the incidence of dysphagia, although cautious clinical validation is necessary.

  20. Brachial Plexopathy in Apical Non-Small Cell Lung Cancer Treated With Definitive Radiation: Dosimetric Analysis and Clinical Implications

    SciTech Connect

    Eblan, Michael J.; Corradetti, Michael N.; Lukens, J. Nicholas; Xanthopoulos, Eric; Mitra, Nandita; Christodouleas, John P.; Grover, Surbhi; Fernandes, Annemarie T.; Langer, Corey J.; Evans, Tracey L.; Stevenson, James; Rengan, Ramesh; Apisarnthanarax, Smith

    2013-01-01

    Purpose: Data are limited on the clinical significance of brachial plexopathy in patients with apical non-small cell lung cancers (NSCLC) treated with definitive radiation therapy. We report the rates of radiation-induced brachial plexopathy (RIBP) and tumor-related brachial plexopathy (TRBP) and associated dosimetric parameters in apical NSCLC patients. Methods and Materials: Charts of NSCLC patients with primary upper lobe or superiorly located nodal disease who received {>=}50 Gy of definitive conventionally fractionated radiation or chemoradiation were retrospectively reviewed for evidence of brachial plexopathy and categorized as RIBP, TRBP, or trauma-related. Dosimetric data were gathered on ipsilateral brachial plexuses (IBP) contoured according to Radiation Therapy Oncology Group atlas guidelines. Results: Eighty patients were identified with a median follow-up and survival time of 17.2 and 17.7 months, respectively. The median prescribed dose was 66.6 Gy (range, 50.4-84.0), and 71% of patients received concurrent chemotherapy. RIBP occurred in 5 patients with an estimated 3-year rate of 12% when accounting for competing risk of death. Seven patients developed TRBP (estimated 3-year rate of 13%), comprising 24% of patients who developed locoregional failures. Grade 3 brachial plexopathy was more common in patients who experienced TRBP than RIBP (57% vs 20%). No patient who received {<=}78 Gy to the IBP developed RIBP. On multivariable competing risk analysis, IBP V76 receiving {>=}1 cc, and primary tumor failure had the highest hazard ratios for developing RIBP and TRBP, respectively. Conclusions: RIBP is a relatively uncommon complication in patients with apical NSCLC tumors receiving definitive doses of radiation, while patients who develop primary tumor failures are at high risk for developing morbid TRBP. These findings suggest that the importance of primary tumor control with adequate doses of radiation outweigh the risk of RIBP in this population of

  1. Comparison of TG-43 dosimetric parameters of brachytherapy sources obtained by three different versions of MCNP codes.

    PubMed

    Zaker, Neda; Zehtabian, Mehdi; Sina, Sedigheh; Koontz, Craig; Meigooni, Ali S

    2016-01-01

    Monte Carlo simulations are widely used for calculation of the dosimetric parameters of brachytherapy sources. MCNP4C2, MCNP5, MCNPX, EGS4, EGSnrc, PTRAN, and GEANT4 are among the most commonly used codes in this field. Each of these codes utilizes a cross-sectional library for the purpose of simulating different elements and materials with complex chemical compositions. The accuracies of the final outcomes of these simulations are very sensitive to the accuracies of the cross-sectional libraries. Several investigators have shown that inaccuracies of some of the cross section files have led to errors in 125I and 103Pd parameters. The purpose of this study is to compare the dosimetric parameters of sample brachytherapy sources, calculated with three different versions of the MCNP code - MCNP4C, MCNP5, and MCNPX. In these simulations for each source type, the source and phantom geometries, as well as the number of the photons, were kept identical, thus eliminating the possible uncertainties. The results of these investigations indicate that for low-energy sources such as 125I and 103Pd there are discrepancies in gL(r) values. Discrepancies up to 21.7% and 28% are observed between MCNP4C and other codes at a distance of 6 cm for 103Pd and 10 cm for 125I from the source, respectively. However, for higher energy sources, the discrepancies in gL(r) values are less than 1.1% for 192Ir and less than 1.2% for 137Cs between the three codes. PMID:27074460

  2. Investigation of the dosimetric accuracy of the isocenter shifting method in prostate cancer patients with and without hip prostheses

    SciTech Connect

    Hwang, Andrew B.; Kinsey, Erica; Xia Ping

    2009-11-15

    Purpose: The use of image guided radiation therapy (IGRT) enables compensation for prostate movement by shifting the treatment isocenter to track the prostate on a daily basis. Although shifting the isocenter can alter the source to skin distances (SSDs) and the effective depth of the target volume, it is commonly assumed that these changes have a negligible dosimetric effect, and therefore, the number of monitor units delivered is usually not adjusted. However, it is unknown whether or not this assumption is valid for patient with hip prostheses, which frequently contain high density materials. Methods: The authors conducted a retrospective study to investigate dosimetric effect of the isocenter shifting method for prostate patients with and without hip prostheses. For each patient, copies of the prostate volume were shifted by up to 1.5 cm from the original position to simulate prostate movement in 0.5 cm increments. Subsequently, 12 plans were created for each patient by creating a copy of the original plan for each prostate position with the isocenter shifted to track the position of the shifted prostate. The dose to the prostate was then recalculated for each plan. For patients with hip prostheses, plans were created both with and without lateral beam angles entering through the prostheses. Results: Without isocenter shifting to compensate for prostate motion of 1.5 cm, the dose to the 95% of the prostate (D-95%) changed by an average of 30% and by up to 64%. This was reduced to less than 3% with the isocenter shifting method. It was found that for patients with hip prostheses, this technique worked best for treatment plans that avoided beam angles passing through the prostheses. Conclusions: The results demonstrated that the isocenter shifting method can accurately deliver dose to the prostate even in patients with hip prostheses.

  3. Dosimetric comparisons of carbon ion treatment plans for 1D and 2D ripple filters with variable thicknesses.

    PubMed

    Ringbæk, Toke Printz; Weber, Uli; Santiago, Alina; Simeonov, Yuri; Fritz, Peter; Krämer, Michael; Wittig, Andrea; Bassler, Niels; Engenhart-Cabillic, Rita; Zink, Klemens

    2016-06-01

    A ripple filter (RiFi)-also called mini-ridge filter-is a passive energy modulator used in particle beam treatments that broadens the Bragg peak (BP) as a function of its maximum thickness. The number of different energies requested from the accelerator can thus be reduced, which significantly reduces the treatment time. A new second generation RiFi with 2D groove shapes was developed using rapid prototyping, which optimizes the beam-modulating material and enables RiFi thicknesses of up to 6 mm. Carbon ion treatment plans were calculated using the standard 1D 3 mm thick RiFi and the new 4 and 6 mm 2D RiFis for spherical planning target volumes (PTVs) in water, eight stage I non-small cell lung cancer cases, four skull base chordoma cases and three prostate cancer cases. TRiP98 was used for treatment planning with facility-specific base data calculated with the Monte Carlo code SHIELD-HIT12A. Dose-volume-histograms, spatial dose distributions and dosimetric indexes were used for plan evaluation. Plan homogeneity and conformity of thinner RiFis were slightly superior to thicker RiFis but satisfactory results were obtained for all RiFis investigated. For the 6 mm RiFi, fine structures in the dose distribution caused by the larger energy steps were observed at the PTV edges, in particular for superficial and/or very small PTVs but performances for all RiFis increased with penetration depth due to straggling and scattering effects. Plans with the new RiFi design yielded for the studied cases comparable dosimetric results to the standard RiFi while the 4 and 6 mm RiFis lowered the irradiation time by 25-30% and 45-49%, respectively.

  4. Evaluating the dosimetric effect of treatment-induced changes in virally mediated head and neck cancer patients

    SciTech Connect

    Brown, Elizabeth; Owen, Rebecca; Mengersen, Kerrie; Harden, Fiona; Porceddu, Sandro

    2013-12-15

    Patients with virally mediated head and neck cancer (VMHNC) often present with advanced nodal disease that is highly radioresponsive as demonstrated by tumour and nodal regression during treatment. The resultant changes may impact on the planned dose distribution and so adversely affect the therapeutic ratio. The aim of this study was to evaluate the dosimetric effect of treatment-induced anatomical changes in VMHNC patients who had undergone a replan. Thirteen patients with virally mediated oropharyngeal or nasopharyngeal cancer who presented for definitive radiotherapy between 2005 and 2010 and who had a replan generated were investigated. The dosimetric effect of anatomical changes was quantified by comparing dose–volume histograms (DVH) of primary and nodal gross target volumes and organs at risk (OAR), including spinal cord and parotid glands, from the original plan and a comparison plan. Eleven three-dimensional conformal radiation therapy (3DCRT) and two intensity modulated radiation therapy (IMRT) plans were evaluated. Dose to the spinal cord and brainstem increased by 4.1% and 2.6%, respectively. Mean dose to the parotid glands also increased by 3.5%. In contrast, the dose received by 98% of the primary and nodal gross tumour volumes decreased by 0.15% and 0.3%, respectively, when comparing the initial treatment plan to the comparison plan. In this study, treatment-induced anatomical changes had the greatest impact on OAR dose with negligible effect on the dose to nodal gross tumour volumes. In the era of IMRT, accounting for treatment-induced anatomical changes is important as focus is placed on minimizing the acute and long-term side effects of treatment.

  5. Heat Capacity Mapping Mission

    NASA Technical Reports Server (NTRS)

    Nilsson, C. S.; Andrews, J. C.; Scully-Power, P.; Ball, S.; Speechley, G.; Latham, A. R. (Principal Investigator)

    1980-01-01

    The Tasman Front was delineated by airborne expendable bathythermograph survey; and an Heat Capacity Mapping Mission (HCMM) IR image on the same day shows the same principal features as determined from ground-truth. It is clear that digital enhancement of HCMM images is necessary to map ocean surface temperatures and when done, the Tasman Front and other oceanographic features can be mapped by this method, even through considerable scattered cloud cover.

  6. Regularity of mappings inverse to Sobolev mappings

    SciTech Connect

    Vodop'yanov, Sergei K

    2012-10-31

    For homeomorphisms {phi}:{Omega}{yields}{Omega}' on Euclidean domains in R{sup n}, n{>=}2, necessary and sufficient conditions ensuring that the inverse mapping belongs to a Sobolev class are investigated. The result obtained is used to describe a new two-index scale of homeomorphisms in some Sobolev class such that their inverses also form a two-index scale of mappings, in another Sobolev class. This scale involves quasiconformal mappings and also homeomorphisms in the Sobolev class W{sup 1}{sub n-1} such that rankD{phi}(x){<=}n-2 almost everywhere on the zero set of the Jacobian det D{phi}(x). Bibliography: 65 titles.

  7. Chaotic Polynomial Maps

    NASA Astrophysics Data System (ADS)

    Zhang, Xu

    This paper introduces a class of polynomial maps in Euclidean spaces, investigates the conditions under which there exist Smale horseshoes and uniformly hyperbolic invariant sets, studies the chaotic dynamical behavior and strange attractors, and shows that some maps are chaotic in the sense of Li-Yorke or Devaney. This type of maps includes both the Logistic map and the Hénon map. For some diffeomorphisms with the expansion dimension equal to one or two in three-dimensional spaces, the conditions under which there exist Smale horseshoes and uniformly hyperbolic invariant sets on which the systems are topologically conjugate to the two-sided fullshift on finite alphabet are obtained; for some expanding maps, the chaotic region is analyzed by using the coupled-expansion theory and the Brouwer degree theory. For three types of higher-dimensional polynomial maps with degree two, the conditions under which there are Smale horseshoes and uniformly hyperbolic invariant sets are given, and the topological conjugacy between the maps on the invariant sets and the two-sided fullshift on finite alphabet is obtained. Some interesting maps with chaotic attractors and positive Lyapunov exponents in three-dimensional spaces are found by using computer simulations. In the end, two examples are provided to illustrate the theoretical results.

  8. BOREAS Hardcopy Maps

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Nelson, Elizabeth; Newcomer, Jeffrey A.

    2000-01-01

    Boreal Ecosystem-Atmospheric Study (BOREAS) hardcopy maps are a collection of approximately 1,000 hardcopy maps representing the physical, climatological, and historical attributes of areas covering primarily the Manitoba and Saskatchewan provinces of Canada. These maps were collected by BOREAS Information System (BORIS) and Canada for Remote Sensing (CCRS) staff to provide basic information about site positions, manmade features, topography, geology, hydrology, land cover types, fire history, climate, and soils of the BOREAS study region. These maps are not available for distribution through the BOREAS project but may be used as an on-site resource. Information is provided within this document for individuals who want to order copies of these maps from the original map source. Note that the maps are not contained on the BOREAS CD-ROM set. An inventory listing file is supplied on the CD-ROM to inform users of the maps that are available. This inventory listing is available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). For hardcopies of the individual maps, contact the sources provided.

  9. Maps and Map Learning in Social Studies

    ERIC Educational Resources Information Center

    Bednarz, Sarah Witham; Acheson, Gillian; Bednarz, Robert S.

    2006-01-01

    The importance of maps and other graphic representations has become more important to geography and geographers. This is due to the development and widespread diffusion of geographic (spatial) technologies. As computers and silicon chips have become more capable and less expensive, geographic information systems (GIS), global positioning satellite…

  10. Lyman Alpha Mapping Project (LAMP) Brightness Maps

    NASA Astrophysics Data System (ADS)

    Retherford, Kurt D.; Gladstone, G.; Stern, S.; Egan, A. F.; Miles, P. F.; Parker, J. W.; Greathouse, T. K.; Davis, M. W.; Slater, D. C.; Kaufmann, D. E.; Versteeg, M. H.; Feldman, P. D.; Hurley, D. M.; Pryor, W. R.; Hendrix, A. R.

    2010-10-01

    The Lyman Alpha Mapping Project (LAMP) is an ultraviolet (UV) spectrograph on the Lunar Reconnaissance Orbiter (LRO) that is designed to map the lunar albedo at far-UV wavelengths. LAMP primarily measures interplanetary Hydrogen Lyman-alpha sky-glow and far-UV starlight reflected from the night-side lunar surface, including permanently shadowed regions (PSRs) near the poles. Dayside observations are also obtained. Brightness maps sorted by wavelength (including the Lyman-alpha wavelength of 121.6 nm) are reported for the polar regions, with a few regions of interest reported in more detail. LAMP's spectral range of 58 nm to 196 nm includes a water ice spectral feature near 160 nm, which provides a diagnostic tool for detecting water on the lunar surface that is complementary to recent discoveries using infrared and radio frequency techniques. Progress towards producing far-UV albedo maps and searching for water ice signatures will be reported. We'll discuss how LAMP data may address questions regarding how water is formed on the moon, transported through the lunar atmosphere, and deposited in the PSRs.

  11. Maps--Map Reading and Aerial Photography. [2 Units].

    ERIC Educational Resources Information Center

    Haakonsen, Harry O., Ed.

    Included in this set of materials are two units: (1) Maps and Map Reading and (2) Aerial Photography. Each unit includes student guide sheets, reference material, and tape script. A set of 35mm slides and audiotapes are usually used with the materials. The unit on Maps and Map Reading is designed to develop map reading skills and the use of these…

  12. Mapping Symbolic Development.

    ERIC Educational Resources Information Center

    Perry, Martha Davis; Wolf, Dennie Palmer

    In an investigation of the development of mapping as distinct from drawing, 39 middle and lower class Cambridge, Massachusetts children in kindergarten and first- and second-grades were shown a small three-dimensional model town, asked to make a smaller, three-dimensional copy of the model, and then asked to make a map showing each item in the…

  13. Mapping Microbial Biodiversity

    SciTech Connect

    Stoner, Daphne Lisabet; Micah C. Geary; White, Luke James; Lee, Randy Dean; Brizzee, Julie Ann; Rodman, A. C.; Rope, Ronald C

    2001-09-01

    We report the development of a prototype database that "maps" microbial diversity in the context of the geochemical and geological environment and geographic location. When it is fully implemented, scientists will be able to conduct database searches, construct maps containing the information of interest, download files, and enter data over the Internet.

  14. Chizu Task Mapping Tool

    SciTech Connect

    2014-07-01

    Chizu is a tool for Mapping MPI processes or tasks to physical processors or nodes for optimizing communication performance. It takes the communication graph of a High Performance Computing (HPC) application and the interconnection topology of a supercomputer as input. It outputs a new MPI rand to processor mapping, which can be used when launching the HPC application.

  15. Map Skills with Meaning.

    ERIC Educational Resources Information Center

    Hamilton, Paula; And Others

    1993-01-01

    Presents hands-on activities to help teach elementary students map skills during Geography Awareness Week. The map skills are made fun by being incorporated into meaningful activities like learning about global resources, tracking the progress of sports teams, and conducting climate experiments in faraway places. (SM)

  16. MAP3K1

    PubMed Central

    Pham, Trang T.; Angus, Steven P.

    2013-01-01

    MAP3K1 is a member of the mitogen-activated protein kinase kinase kinase (MAP3K) family of serine/threonine kinases. MAP3K1 regulates JNK activation and is unique among human kinases in that it also encodes an E3 ligase domain that ubiquitylates c-Jun and ERK1/2. Full length MAP3K1 regulates cell migration and contributes to pro-survival signaling while its caspase 3-mediated cleavage generates a C-terminal kinase domain that promotes apoptosis. The critical function of MAP3K1 in cell fate decisions suggests that it may be a target for deregulation in cancer. Recent large-scale genomic studies have revealed that MAP3K1 copy number loss and somatic missense or nonsense mutations are observed in a significant number of different cancers, being most prominent in luminal breast cancer. The alteration of MAP3K1 in diverse cancer types demonstrates the importance of defining phenotypes for possible therapeutic targeting of tumor cell vulnerabilities created when MAP3K1 function is lost or gained. PMID:24386504

  17. Site and Watershed Mapping.

    ERIC Educational Resources Information Center

    Institute for Environmental Education, Cleveland, OH.

    Presented as part of a larger unit on watershed investigations are a slideshow script and a map and compass unit intended to help high school students better visualize the relationship between a water sampling site, the entire stream, community, and watershed. The script discusses features of a topographical map, shows how to read one, and…

  18. Temporal mapping and analysis

    NASA Technical Reports Server (NTRS)

    O'Hara, Charles G. (Inventor); Shrestha, Bijay (Inventor); Vijayaraj, Veeraraghavan (Inventor); Mali, Preeti (Inventor)

    2011-01-01

    A compositing process for selecting spatial data collected over a period of time, creating temporal data cubes from the spatial data, and processing and/or analyzing the data using temporal mapping algebra functions. In some embodiments, the temporal data cube is creating a masked cube using the data cubes, and computing a composite from the masked cube by using temporal mapping algebra.

  19. Acoustic mapping velocimetry

    NASA Astrophysics Data System (ADS)

    Muste, M.; Baranya, S.; Tsubaki, R.; Kim, D.; Ho, H.; Tsai, H.; Law, D.

    2016-05-01

    Knowledge of sediment dynamics in rivers is of great importance for various practical purposes. Despite its high relevance in riverine environment processes, the monitoring of sediment rates remains a major and challenging task for both suspended and bed load estimation. While the measurement