Partial volume correction of brain perfusion estimates using the inherent signal data of time-resolved arterial spin labeling.

PubMed

Ahlgren, André; Wirestam, Ronnie; Petersen, Esben Thade; Ståhlberg, Freddy; Knutsson, Linda

2014-09-01

Quantitative perfusion MRI based on arterial spin labeling (ASL) is hampered by partial volume effects (PVEs), arising due to voxel signal cross-contamination between different compartments. To address this issue, several partial volume correction (PVC) methods have been presented. Most previous methods rely on segmentation of a high-resolution T1 -weighted morphological image volume that is coregistered to the low-resolution ASL data, making the result sensitive to errors in the segmentation and coregistration. In this work, we present a methodology for partial volume estimation and correction, using only low-resolution ASL data acquired with the QUASAR sequence. The methodology consists of a T1 -based segmentation method, with no spatial priors, and a modified PVC method based on linear regression. The presented approach thus avoids prior assumptions about the spatial distribution of brain compartments, while also avoiding coregistration between different image volumes. Simulations based on a digital phantom as well as in vivo measurements in 10 volunteers were used to assess the performance of the proposed segmentation approach. The simulation results indicated that QUASAR data can be used for robust partial volume estimation, and this was confirmed by the in vivo experiments. The proposed PVC method yielded probable perfusion maps, comparable to a reference method based on segmentation of a high-resolution morphological scan. Corrected gray matter (GM) perfusion was 47% higher than uncorrected values, suggesting a significant amount of PVEs in the data. Whereas the reference method failed to completely eliminate the dependence of perfusion estimates on the volume fraction, the novel approach produced GM perfusion values independent of GM volume fraction. The intra-subject coefficient of variation of corrected perfusion values was lowest for the proposed PVC method. As shown in this work, low-resolution partial volume estimation in connection with ASL perfusion estimation is feasible, and provides a promising tool for decoupling perfusion and tissue volume. Copyright © 2014 John Wiley & Sons, Ltd.

Impact of reconstruction parameters on quantitative I-131 SPECT

NASA Astrophysics Data System (ADS)

van Gils, C. A. J.; Beijst, C.; van Rooij, R.; de Jong, H. W. A. M.

2016-07-01

Radioiodine therapy using I-131 is widely used for treatment of thyroid disease or neuroendocrine tumors. Monitoring treatment by accurate dosimetry requires quantitative imaging. The high energy photons however render quantitative SPECT reconstruction challenging, potentially requiring accurate correction for scatter and collimator effects. The goal of this work is to assess the effectiveness of various correction methods on these effects using phantom studies. A SPECT/CT acquisition of the NEMA IEC body phantom was performed. Images were reconstructed using the following parameters: (1) without scatter correction, (2) with triple energy window (TEW) scatter correction and (3) with Monte Carlo-based scatter correction. For modelling the collimator-detector response (CDR), both (a) geometric Gaussian CDRs as well as (b) Monte Carlo simulated CDRs were compared. Quantitative accuracy, contrast to noise ratios and recovery coefficients were calculated, as well as the background variability and the residual count error in the lung insert. The Monte Carlo scatter corrected reconstruction method was shown to be intrinsically quantitative, requiring no experimentally acquired calibration factor. It resulted in a more accurate quantification of the background compartment activity density compared with TEW or no scatter correction. The quantification error relative to a dose calibrator derived measurement was found to be  <1%,-26% and 33%, respectively. The adverse effects of partial volume were significantly smaller with the Monte Carlo simulated CDR correction compared with geometric Gaussian or no CDR modelling. Scatter correction showed a small effect on quantification of small volumes. When using a weighting factor, TEW correction was comparable to Monte Carlo reconstruction in all measured parameters, although this approach is clinically impractical since this factor may be patient dependent. Monte Carlo based scatter correction including accurately simulated CDR modelling is the most robust and reliable method to reconstruct accurate quantitative iodine-131 SPECT images.

A 4-Week Preoperative Ketogenic Micronutrient-Enriched Diet Is Effective in Reducing Body Weight, Left Hepatic Lobe Volume, and Micronutrient Deficiencies in Patients Undergoing Bariatric Surgery: a Prospective Pilot Study.

PubMed

Schiavo, Luigi; Pilone, Vincenzo; Rossetti, Gianluca; Barbarisi, Alfonso; Cesaretti, Manuela; Iannelli, Antonio

2018-03-03

Before bariatric surgery (BS), moderate weight loss, left hepatic lobe volume reduction, and micronutrient deficiency (MD) identification and correction are desirable. The objective of this study was to assess the safety and the effectiveness of a 4-week preoperative ketogenic micronutrient-enriched diet (KMED) in reducing body weight (BW), left hepatic lobe volume, and correcting MD in patients scheduled for BS. In this prospective pilot study, a cohort of morbidly obese patients (n = 27, 17 females, 10 males) with a mean body mass index (BMI) of 45.2 kg/m 2 scheduled for BS underwent a 4-week preoperative KMED. Their BW, BMI, fat mass (FM), fat-free mass (FFM), resting metabolic rate (RMR), left hepatic lobe volume, micronutrient status, and biochemical and metabolic patterns were measured before and after the 4-week KMED. Patient compliance was assessed by validated questionnaires (3-day estimated food records and 72-h recall). Qualitative methods (5-point Likert questionnaire) were used to measure diet acceptability and side effects. All patients completed the study. We observed highly significant decreases in BW (- 10.3%, p < 0.001, in males; - 8.2%, p < 0.001, in females), left hepatic lobe volume (- 19.8%, p < 0.001), and an amelioration of patient micronutrient status. All patients showed a high frequency of acceptability and compliance in following the diet. No adverse side effect was reported. This study demonstrates that a 4-week preoperative KMED is safe and effective in reducing BW, left hepatic lobe volume, and correcting MD in obese patients scheduled for BS.

Onboard utilization of ground control points for image correction. Volume 2: Analysis and simulation results

NASA Technical Reports Server (NTRS)

1981-01-01

An approach to remote sensing that meets future mission requirements was investigated. The deterministic acquisition of data and the rapid correction of data for radiometric effects and image distortions are the most critical limitations of remote sensing. The following topics are discussed: onboard image correction systems, GCP navigation system simulation, GCP analysis, and image correction analysis measurement.

Comparison of T1-weighted 2D TSE, 3D SPGR, and two-point 3D Dixon MRI for automated segmentation of visceral adipose tissue at 3 Tesla.

PubMed

Fallah, Faezeh; Machann, Jürgen; Martirosian, Petros; Bamberg, Fabian; Schick, Fritz; Yang, Bin

2017-04-01

To evaluate and compare conventional T1-weighted 2D turbo spin echo (TSE), T1-weighted 3D volumetric interpolated breath-hold examination (VIBE), and two-point 3D Dixon-VIBE sequences for automatic segmentation of visceral adipose tissue (VAT) volume at 3 Tesla by measuring and compensating for errors arising from intensity nonuniformity (INU) and partial volume effects (PVE). The body trunks of 28 volunteers with body mass index values ranging from 18 to 41.2 kg/m 2 (30.02 ± 6.63 kg/m 2 ) were scanned at 3 Tesla using three imaging techniques. Automatic methods were applied to reduce INU and PVE and to segment VAT. The automatically segmented VAT volumes obtained from all acquisitions were then statistically and objectively evaluated against the manually segmented (reference) VAT volumes. Comparing the reference volumes with the VAT volumes automatically segmented over the uncorrected images showed that INU led to an average relative volume difference of -59.22 ± 11.59, 2.21 ± 47.04, and -43.05 ± 5.01 % for the TSE, VIBE, and Dixon images, respectively, while PVE led to average differences of -34.85 ± 19.85, -15.13 ± 11.04, and -33.79 ± 20.38 %. After signal correction, differences of -2.72 ± 6.60, 34.02 ± 36.99, and -2.23 ± 7.58 % were obtained between the reference and the automatically segmented volumes. A paired-sample two-tailed t test revealed no significant difference between the reference and automatically segmented VAT volumes of the corrected TSE (p = 0.614) and Dixon (p = 0.969) images, but showed a significant VAT overestimation using the corrected VIBE images. Under similar imaging conditions and spatial resolution, automatically segmented VAT volumes obtained from the corrected TSE and Dixon images agreed with each other and with the reference volumes. These results demonstrate the efficacy of the signal correction methods and the similar accuracy of TSE and Dixon imaging for automatic volumetry of VAT at 3 Tesla.

Infusion volume control and calculation using metronome and drop counter based intravenous infusion therapy helper.

PubMed

Park, Kyungnam; Lee, Jangyoung; Kim, Soo-Young; Kim, Jinwoo; Kim, Insoo; Choi, Seung Pill; Jeong, Sikyung; Hong, Sungyoup

2013-06-01

This study assessed the method of fluid infusion control using an IntraVenous Infusion Controller (IVIC). Four methods of infusion control (dial flow controller, IV set without correction, IV set with correction and IVIC correction) were used to measure the volume of each technique at two infusion rates. The infused fluid volume with a dial flow controller was significantly larger than other methods. The infused fluid volume was significantly smaller with an IV set without correction over time. Regarding the concordance correlation coefficient (CCC) of infused fluid volume in relation to a target volume, IVIC correction was shown to have the highest level of agreement. The flow rate measured in check mode showed a good agreement with the volume of collected fluid after passing through the IV system. Thus, an IVIC could assist in providing an accurate infusion control. © 2013 Wiley Publishing Asia Pty Ltd.

High-quality 3D correction of ring and radiant artifacts in flat panel detector-based cone beam volume CT imaging

NASA Astrophysics Data System (ADS)

Abu Anas, Emran Mohammad; Kim, Jae Gon; Lee, Soo Yeol; Kamrul Hasan, Md

2011-10-01

The use of an x-ray flat panel detector is increasingly becoming popular in 3D cone beam volume CT machines. Due to the deficient semiconductor array manufacturing process, the cone beam projection data are often corrupted by different types of abnormalities, which cause severe ring and radiant artifacts in a cone beam reconstruction image, and as a result, the diagnostic image quality is degraded. In this paper, a novel technique is presented for the correction of error in the 2D cone beam projections due to abnormalities often observed in 2D x-ray flat panel detectors. Template images are derived from the responses of the detector pixels using their statistical properties and then an effective non-causal derivative-based detection algorithm in 2D space is presented for the detection of defective and mis-calibrated detector elements separately. An image inpainting-based 3D correction scheme is proposed for the estimation of responses of defective detector elements, and the responses of the mis-calibrated detector elements are corrected using the normalization technique. For real-time implementation, a simplification of the proposed off-line method is also suggested. Finally, the proposed algorithms are tested using different real cone beam volume CT images and the experimental results demonstrate that the proposed methods can effectively remove ring and radiant artifacts from cone beam volume CT images compared to other reported techniques in the literature.

Late-Onset Alzheimer's Disease Polygenic Risk Profile Score Predicts Hippocampal Function.

PubMed

Xiao, Ena; Chen, Qiang; Goldman, Aaron L; Tan, Hao Yang; Healy, Kaitlin; Zoltick, Brad; Das, Saumitra; Kolachana, Bhaskar; Callicott, Joseph H; Dickinson, Dwight; Berman, Karen F; Weinberger, Daniel R; Mattay, Venkata S

2017-11-01

We explored the cumulative effect of several late-onset Alzheimer's disease (LOAD) risk loci using a polygenic risk profile score (RPS) approach on measures of hippocampal function, cognition, and brain morphometry. In a sample of 231 healthy control subjects (19-55 years of age), we used an RPS to study the effect of several LOAD risk loci reported in a recent meta-analysis on hippocampal function (determined by its engagement with blood oxygen level-dependent functional magnetic resonance imaging during episodic memory) and several cognitive metrics. We also studied effects on brain morphometry in an overlapping sample of 280 subjects. There was almost no significant association of LOAD-RPS with cognitive or morphometric measures. However, there was a significant negative relationship between LOAD-RPS and hippocampal function (familywise error [small volume correction-hippocampal region of interest] p < .05). There were also similar associations for risk score based on APOE haplotype, and for a combined LOAD-RPS + APOE haplotype risk profile score (p < .05 familywise error [small volume correction-hippocampal region of interest]). Of the 29 individual single nucleotide polymorphisms used in calculating LOAD-RPS, variants in CLU, PICALM, BCL3, PVRL2, and RELB showed strong effects (p < .05 familywise error [small volume correction-hippocampal region of interest]) on hippocampal function, though none survived further correction for the number of single nucleotide polymorphisms tested. There is a cumulative deleterious effect of LOAD risk genes on hippocampal function even in healthy volunteers. The effect of LOAD-RPS on hippocampal function in the relative absence of any effect on cognitive and morphometric measures is consistent with the reported temporal characteristics of LOAD biomarkers with the earlier manifestation of synaptic dysfunction before morphometric and cognitive changes. Copyright © 2017 Society of Biological Psychiatry. All rights reserved.

Tropical forest tree stands characterization with L-band polarimetric radar

NASA Technical Reports Server (NTRS)

Wu, Shih-Tseng

1990-01-01

The effectiveness of using L-band polarimetric data to determine tropical tree-stand parameters is discussed with specific attention given to the correction of the radar data. Tree-parameter data from ground studies is compared to L-band polarimetric data (in both uncorrected and topographically corrected forms) for two test areas. The test sites are at two different elevations but both include 81 test plots with topographic data and tree-characteristic data given. Synthetic-aperture radar (SAR) data are found to be related to bole volume and tree volume, and the topographically corrected data show results similar to the uncorrected data. Similar r-values are given for both data sets because the data with incidence-angle values below 35 and above 55 are removed. Topographical correction is important when local incidence angles exceed the limits.

Upgraded Analytical Model of the Cylinder Test

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

Souers, P. Clark; Lauderbach, Lisa; Garza, Raul

2013-03-15

A Gurney-type equation was previously corrected for wall thinning and angle of tilt, and now we have added shock wave attenuation in the copper wall and air gap energy loss. Extensive calculations were undertaken to calibrate the two new energy loss mechanisms across all explosives. The corrected Gurney equation is recommended for cylinder use over the original 1943 form. The effect of these corrections is to add more energy to the adiabat values from a relative volume of 2 to 7, with low energy explosives having the largest correction. The data was pushed up to a relative volume of aboutmore » 15 and the JWL parameter ω was obtained directly. The total detonation energy density was locked to the v=7 adiabat energy density, so that the Cylinder test gives all necessary values needed to make a JWL.« less

Upgraded Analytical Model of the Cylinder Test

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

Souers, P. Clark; Lauderbach, Lisa; Garza, Raul

2013-03-15

A Gurney-type equation was previously corrected for wall thinning and angle of tilt, and now we have added shock wave attenuation in the copper wall and air gap energy loss. Extensive calculations were undertaken to calibrate the two new energy loss mechanisms across all explosives. The corrected Gurney equation is recommended for cylinder use over the original 1943 form. The effect of these corrections is to add more energy to the adiabat values from a relative volume of 2 to 7, with low energy explosives having the largest correction. The data was pushed up to a relative volume of aboutmore » 15 and the JWL parameter ω was obtained directly. Finally, the total detonation energy density was locked to the v = 7 adiabat energy density, so that the Cylinder test gives all necessary values needed to make a JWL.« less

Does early tetralogy of Fallot total correction give better final lung volumes?

PubMed

Sadeghi, Hasan Allah; Miri, Seyed Reza; Bakhshandeh, Hooman; Mirmesdagh, Yalda; Paziraee, Nazita

2013-06-01

Pulmonary blood flow may affect lung development in adulthood. Early total correction of tetralogy of Fallot may affect development of final lung volumes. We evaluated the effect of age at total correction on lung volumes years after the operation. In a retrospective cohort study on patients with totally corrected tetralogy of Fallot (mean age, 13.40 years at the time of follow-up), forced vital capacity, slow vital capacity, forced expiratory volume in 1 s, and other parameters were measured 154.8 ± 46.25 months after the operation. Comparison were made of 3 groups: ≤2-, 2-8-, and >8-years old at the time of total correction surgery. Among 322 enrolled patients, the mean values of the follow-up spirometry results in ≤2-, 2-8-, >8-year-olds and the percentage of predicted values were respectively: vital capacity: 4.46 ± 0.57 L (107% ± 10.96%), 3.89 ± 0.58 L (91.10% ± 12.25%), 3.25 ± 0.48 L (82.35% ± 10.62%), p < 0.001; forced vital capacity: 4.28 ± 0.63 L (95.90% ± 18.77%), 3.76 ± 0.58 L (90.83% ± 12.52%), 3.14 ± 0.49 L (83.26% ± 11.71%), p < 0.001; forced expiratory volume in 1 s: 4.22 ± 0.63 L (104.84% ± 13.64%), 3.66 ± 0.58 L (90.61% ± 12.59%), 3.02 ± 0.48 L (84.31% ± 12%), p < 0.001. Early correction of defects or reestablishments of perfusion of tetralogy of Fallot before completion of lung development might improve final adulthood lung volumes and capacities. It is better to consider total correction for all tetralogy of Fallot patients below 2-years old, or at least below 8-years old, if it is technically possible.

Superficial Enhanced Fluid Fat Injection (SEFFI) to Correct Volume Defects and Skin Aging of the Face and Periocular Region.

PubMed

Bernardini, Francesco P; Gennai, Alessandro; Izzo, Luigi; Zambelli, Alessandra; Repaci, Erica; Baldelli, Ilaria; Fraternali-Orcioni, G; Hartstein, Morris E; Santi, Pier Luigi; Quarto, Rodolfo

2015-07-01

Although recent research on micro fat has shown the potential advantages of superficial implantation and high stem cell content, clinical applications thus far have been limited. The authors report their experience with superficial enhanced fluid fat injection (SEFFI) for the correction of volume loss and skin aging of the face in general and in the periocular region. The finer SEFFI preparation (0.5 mL) was injected into the orbicularis in the periorbital and perioral areas, and the 0.8-mL preparation was injected subdermally elsewhere in the face. The records of 98 consecutive patients were reviewed. Average follow-up time was 6 months, and average volume of implanted fat was 20 mL and 51.4 mL for the 0.5-mL and 0.8-mL preparations, respectively. Good or excellent results were achieved for volume restoration and skin improvement in all patients. Complications were minor and included an oil cyst in 3 patients. The smaller SEFFI quantity (0.5 mL) was well suited to correct volume loss in the eyelids, especially the deep upper sulcus and tear trough, whereas the larger SEFFI content was effective for larger volume deficits in other areas of the face, including the brow, temporal fossa, zygomatic-malar region, nasolabial folds, marionette lines, chin, and lips. The fat administered by SEFFI is easily harvested via small side-port cannulae, yielding micro fat that is rich in viable adipocytes and stem cells. Both volumes of fat (0.5 mL and 0.8 mL) were effective for treating age-related lipoatrophy, reducing facial rhytids, and improving skin quality. 4 Therapeutic. © 2015 The American Society for Aesthetic Plastic Surgery, Inc. Reprints and permission: journals.permissions@oup.com.

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

Endres, Michael G.; Shindler, Andrea; Tiburzi, Brian C.

The commonly adopted approach for including electromagnetic interactions in lattice QCD simulations relies on using finite volume as the infrared regularization for QED. The long-range nature of the electromagnetic interaction, however, implies that physical quantities are susceptible to power-law finite volume corrections, which must be removed by performing costly simulations at multiple lattice volumes, followed by an extrapolation to the infinite volume limit. In this work, we introduce a photon mass as an alternative means for gaining control over infrared effects associated with electromagnetic interactions. We present findings for hadron mass shifts due to electromagnetic interactions (i.e., for the proton,more » neutron, charged and neutral kaon) and corresponding mass splittings, and compare the results with those obtained from conventional QCD+QED calculations. Results are reported for numerical studies of three flavor electroquenched QCD using ensembles corresponding to 800 MeV pions, ensuring that the only appreciable volume corrections arise from QED effects. The calculations are performed with three lattice volumes with spatial extents ranging from 3.4 - 6.7 fm. As a result, we find that for equal computing time (not including the generation of the lattice configurations), the electromagnetic mass shifts can be extracted from computations on a single (our smallest) lattice volume with comparable or better precision than the conventional approach.« less

Massive photons: An infrared regularization scheme for lattice QCD + QED

DOE PAGES

Endres, Michael G.; Shindler, Andrea; Tiburzi, Brian C.; ...

2016-08-10

The commonly adopted approach for including electromagnetic interactions in lattice QCD simulations relies on using finite volume as the infrared regularization for QED. The long-range nature of the electromagnetic interaction, however, implies that physical quantities are susceptible to power-law finite volume corrections, which must be removed by performing costly simulations at multiple lattice volumes, followed by an extrapolation to the infinite volume limit. In this work, we introduce a photon mass as an alternative means for gaining control over infrared effects associated with electromagnetic interactions. We present findings for hadron mass shifts due to electromagnetic interactions (i.e., for the proton,more » neutron, charged and neutral kaon) and corresponding mass splittings, and compare the results with those obtained from conventional QCD+QED calculations. Results are reported for numerical studies of three flavor electroquenched QCD using ensembles corresponding to 800 MeV pions, ensuring that the only appreciable volume corrections arise from QED effects. The calculations are performed with three lattice volumes with spatial extents ranging from 3.4 - 6.7 fm. As a result, we find that for equal computing time (not including the generation of the lattice configurations), the electromagnetic mass shifts can be extracted from computations on a single (our smallest) lattice volume with comparable or better precision than the conventional approach.« less

Better Assessment of Operational Suitability. Volume 2. Case Studies

DTIC Science & Technology

1992-01-01

August to 25 October 1988. Although declared operationally effective and suitable by OTEA, a Corrective Action Plan (CAP) was instituted on 5 December 1988...to correct performance deficiencies encountered in FOT&E. The option year 3 procureiaent was exercised on 8 December 1988. An OTEA assessment of the...Hughes developed and tested airframe design modifications to correct deficiencies noted in DT POT I, to improve flight handling characteristics, and to

Finite volume effects on the electric polarizability of neutral hadrons in lattice QCD

NASA Astrophysics Data System (ADS)

Lujan, M.; Alexandru, A.; Freeman, W.; Lee, F. X.

2016-10-01

We study the finite volume effects on the electric polarizability for the neutron, neutral pion, and neutral kaon using eight dynamically generated two-flavor nHYP-clover ensembles at two different pion masses: 306(1) and 227(2) MeV. An infinite volume extrapolation is performed for each hadron at both pion masses. For the neutral kaon, finite volume effects are relatively mild. The dependence on the quark mass is also mild, and a reliable chiral extrapolation can be performed along with the infinite volume extrapolation. Our result is αK0 phys=0.356 (74 )(46 )×10-4 fm3 . In contrast, for neutron, the electric polarizability depends strongly on the volume. After removing the finite volume corrections, our neutron polarizability results are in good agreement with chiral perturbation theory. For the connected part of the neutral pion polarizability, the negative trend persists, and it is not due to finite volume effects but likely sea quark charging effects.

Segmentation-free empirical beam hardening correction for CT.

PubMed

Schüller, Sören; Sawall, Stefan; Stannigel, Kai; Hülsbusch, Markus; Ulrici, Johannes; Hell, Erich; Kachelrieß, Marc

2015-02-01

The polychromatic nature of the x-ray beams and their effects on the reconstructed image are often disregarded during standard image reconstruction. This leads to cupping and beam hardening artifacts inside the reconstructed volume. To correct for a general cupping, methods like water precorrection exist. They correct the hardening of the spectrum during the penetration of the measured object only for the major tissue class. In contrast, more complex artifacts like streaks between dense objects need other techniques of correction. If using only the information of one single energy scan, there are two types of corrections. The first one is a physical approach. Thereby, artifacts can be reproduced and corrected within the original reconstruction by using assumptions in a polychromatic forward projector. These assumptions could be the used spectrum, the detector response, the physical attenuation and scatter properties of the intersected materials. A second method is an empirical approach, which does not rely on much prior knowledge. This so-called empirical beam hardening correction (EBHC) and the previously mentioned physical-based technique are both relying on a segmentation of the present tissues inside the patient. The difficulty thereby is that beam hardening by itself, scatter, and other effects, which diminish the image quality also disturb the correct tissue classification and thereby reduce the accuracy of the two known classes of correction techniques. The herein proposed method works similar to the empirical beam hardening correction but does not require a tissue segmentation and therefore shows improvements on image data, which are highly degraded by noise and artifacts. Furthermore, the new algorithm is designed in a way that no additional calibration or parameter fitting is needed. To overcome the segmentation of tissues, the authors propose a histogram deformation of their primary reconstructed CT image. This step is essential for the proposed algorithm to be segmentation-free (sf). This deformation leads to a nonlinear accentuation of higher CT-values. The original volume and the gray value deformed volume are monochromatically forward projected. The two projection sets are then monomially combined and reconstructed to generate sets of basis volumes which are used for correction. This is done by maximization of the image flatness due to adding additionally a weighted sum of these basis images. sfEBHC is evaluated on polychromatic simulations, phantom measurements, and patient data. The raw data sets were acquired by a dual source spiral CT scanner, a digital volume tomograph, and a dual source micro CT. Different phantom and patient data were used to illustrate the performance and wide range of usability of sfEBHC across different scanning scenarios. The artifact correction capabilities are compared to EBHC. All investigated cases show equal or improved image quality compared to the standard EBHC approach. The artifact correction is capable of correcting beam hardening artifacts for different scan parameters and scan scenarios. sfEBHC generates beam hardening-reduced images and is furthermore capable of dealing with images which are affected by high noise and strong artifacts. The algorithm can be used to recover structures which are hardly visible inside the beam hardening-affected regions.

Segmentation-free empirical beam hardening correction for CT

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

Schüller, Sören; Sawall, Stefan; Stannigel, Kai

2015-02-15

Purpose: The polychromatic nature of the x-ray beams and their effects on the reconstructed image are often disregarded during standard image reconstruction. This leads to cupping and beam hardening artifacts inside the reconstructed volume. To correct for a general cupping, methods like water precorrection exist. They correct the hardening of the spectrum during the penetration of the measured object only for the major tissue class. In contrast, more complex artifacts like streaks between dense objects need other techniques of correction. If using only the information of one single energy scan, there are two types of corrections. The first one ismore » a physical approach. Thereby, artifacts can be reproduced and corrected within the original reconstruction by using assumptions in a polychromatic forward projector. These assumptions could be the used spectrum, the detector response, the physical attenuation and scatter properties of the intersected materials. A second method is an empirical approach, which does not rely on much prior knowledge. This so-called empirical beam hardening correction (EBHC) and the previously mentioned physical-based technique are both relying on a segmentation of the present tissues inside the patient. The difficulty thereby is that beam hardening by itself, scatter, and other effects, which diminish the image quality also disturb the correct tissue classification and thereby reduce the accuracy of the two known classes of correction techniques. The herein proposed method works similar to the empirical beam hardening correction but does not require a tissue segmentation and therefore shows improvements on image data, which are highly degraded by noise and artifacts. Furthermore, the new algorithm is designed in a way that no additional calibration or parameter fitting is needed. Methods: To overcome the segmentation of tissues, the authors propose a histogram deformation of their primary reconstructed CT image. This step is essential for the proposed algorithm to be segmentation-free (sf). This deformation leads to a nonlinear accentuation of higher CT-values. The original volume and the gray value deformed volume are monochromatically forward projected. The two projection sets are then monomially combined and reconstructed to generate sets of basis volumes which are used for correction. This is done by maximization of the image flatness due to adding additionally a weighted sum of these basis images. sfEBHC is evaluated on polychromatic simulations, phantom measurements, and patient data. The raw data sets were acquired by a dual source spiral CT scanner, a digital volume tomograph, and a dual source micro CT. Different phantom and patient data were used to illustrate the performance and wide range of usability of sfEBHC across different scanning scenarios. The artifact correction capabilities are compared to EBHC. Results: All investigated cases show equal or improved image quality compared to the standard EBHC approach. The artifact correction is capable of correcting beam hardening artifacts for different scan parameters and scan scenarios. Conclusions: sfEBHC generates beam hardening-reduced images and is furthermore capable of dealing with images which are affected by high noise and strong artifacts. The algorithm can be used to recover structures which are hardly visible inside the beam hardening-affected regions.« less

Buccal Fat Pad: An Effective Option for Facial Reconstruction and Aesthetic Augmentation.

PubMed

Kim, Jeong Tae; Sasidaran, Ramesh

2017-12-01

Autogenous grafting with lipoaspirate and dermo-fat grafting are popular techniques employed by plastic surgeons for correcting small volume facial defects and contour deformities. These techniques however present certain disadvantages. In this article, we present the use of the buccal fat pad graft as an alternative method of correcting such facial deformities. Free buccal fat pad grafting was carried out in 15 patients in our institution. All were harvested using an intraoral approach. The buccal fat pad graft was used to correct periorbital contour depressions, nasal tip deformities, as a camouflage graft over exposed silicon nasal implants and as a filler in the depression deformity after mass excision. All 15 patients demonstrated good contour deformity correction without a significant graft resorption up to 3 years of follow-up. There were no donor site complications. The amount used ranged from 1 to 5 cc in volume as a spacer or barrier for the moderate-sized volume defect or depression, even though more than 5 cc of fat graft could be harvested if required. In conclusion, the buccal fat pad graft represents an easy, expedient and exceptional tool for the correction of contour deformities, volume replacement or for aesthetic augmentation. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Expanding Lorentz and spectrum corrections to large volumes of reciprocal space for single-crystal time-of-flight neutron diffraction

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

Michels-Clark, Tara M.; Savici, Andrei T.; Lynch, Vickie E.

Evidence is mounting that potentially exploitable properties of technologically and chemically interesting crystalline materials are often attributable to local structure effects, which can be observed as modulated diffuse scattering (mDS) next to Bragg diffraction (BD). BD forms a regular sparse grid of intense discrete points in reciprocal space. Traditionally, the intensity of each Bragg peak is extracted by integration of each individual reflection first, followed by application of the required corrections. In contrast, mDS is weak and covers expansive volumes of reciprocal space close to, or between, Bragg reflections. For a representative measurement of the diffuse scattering, multiple sample orientationsmore » are generally required, where many points in reciprocal space are measured multiple times and the resulting data are combined. The common post-integration data reduction method is not optimal with regard to counting statistics. A general and inclusive data processing method is needed. In this contribution, a comprehensive data analysis approach is introduced to correct and merge the full volume of scattering data in a single step, while correctly accounting for the statistical weight of the individual measurements. Lastly, development of this new approach required the exploration of a data treatment and correction protocol that includes the entire collected reciprocal space volume, using neutron time-of-flight or wavelength-resolved data collected at TOPAZ at the Spallation Neutron Source at Oak Ridge National Laboratory.« less

Expanding Lorentz and spectrum corrections to large volumes of reciprocal space for single-crystal time-of-flight neutron diffraction

DOE PAGES

Michels-Clark, Tara M.; Savici, Andrei T.; Lynch, Vickie E.; ...

2016-03-01

Evidence is mounting that potentially exploitable properties of technologically and chemically interesting crystalline materials are often attributable to local structure effects, which can be observed as modulated diffuse scattering (mDS) next to Bragg diffraction (BD). BD forms a regular sparse grid of intense discrete points in reciprocal space. Traditionally, the intensity of each Bragg peak is extracted by integration of each individual reflection first, followed by application of the required corrections. In contrast, mDS is weak and covers expansive volumes of reciprocal space close to, or between, Bragg reflections. For a representative measurement of the diffuse scattering, multiple sample orientationsmore » are generally required, where many points in reciprocal space are measured multiple times and the resulting data are combined. The common post-integration data reduction method is not optimal with regard to counting statistics. A general and inclusive data processing method is needed. In this contribution, a comprehensive data analysis approach is introduced to correct and merge the full volume of scattering data in a single step, while correctly accounting for the statistical weight of the individual measurements. Lastly, development of this new approach required the exploration of a data treatment and correction protocol that includes the entire collected reciprocal space volume, using neutron time-of-flight or wavelength-resolved data collected at TOPAZ at the Spallation Neutron Source at Oak Ridge National Laboratory.« less

SU-E-T-623: Polarity Effects for Small Volume Ionization Chambers in Cobalt-60 Beams

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

Xu, Y; Bhatnagar, J; Huq, M Saiful

2015-06-15

Purpose: To investigate the polarity effects for small volume ionization chambers in {sup 60}Co gamma-ray beams using the Leksell Gamma Knife Perfexion. Methods: Measurements were made for 7 small volume ionization chambers (a PTW 31016, an Exradin A14, 2 Capintec PR0-5P, and 3 Exradin A16) using a PTW UNIDOSwebline Universal Dosemeter and an ELEKTA solid water phantom with proper inserts. For each ion chamber, the temperature/pressure corrected electric charge readings were obtained for 16 voltage values (±50V, ±100V, ±200V, ±300V, ±400V, ±500V, ±600V, ±700V). For each voltage, a five-minute leakage charge reading and a series of 2-minute readings were continuouslymore » taken during irradiation until 5 stable signals (less than 0.05% variation) were obtained. The average of the 5 reading was then used for the calculation of the polarity corrections at the voltage and for generating the saturation curves. Results: The polarity effects are more pronounced at high or low voltages than at the medium voltages for all chambers studied. The voltage dependence of the 3 Exradin A16 chambers is similar in shape. The polarity corrections for the Exradin A16 chambers changes rapidly from about 1 at 500V to about 0.98 at 700V. The polarity corrections for the 7 ion chambers at 300V are in the range from 0.9925 (for the PTW31016) to 1.0035 (for an Exradin A16). Conclusion: The polarity corrections for certain micro-chambers are large even at normal operating voltage.« less

Effect of Malmquist bias on correlation studies with IRAS data base

NASA Technical Reports Server (NTRS)

Verter, Frances

1993-01-01

The relationships between galaxy properties in the sample of Trinchieri et al. (1989) are reexamined with corrections for Malmquist bias. The linear correlations are tested and linear regressions are fit for log-log plots of L(FIR), L(H-alpha), and L(B) as well as ratios of these quantities. The linear correlations for Malmquist bias are corrected using the method of Verter (1988), in which each galaxy observation is weighted by the inverse of its sampling volume. The linear regressions are corrected for Malmquist bias by a new method invented here in which each galaxy observation is weighted by its sampling volume. The results of correlation and regressions among the sample are significantly changed in the anticipated sense that the corrected correlation confidences are lower and the corrected slopes of the linear regressions are lower. The elimination of Malmquist bias eliminates the nonlinear rise in luminosity that has caused some authors to hypothesize additional components of FIR emission.

Analytical-Based Partial Volume Recovery in Mouse Heart Imaging

NASA Astrophysics Data System (ADS)

Dumouchel, Tyler; deKemp, Robert A.

2011-02-01

Positron emission tomography (PET) is a powerful imaging modality that has the ability to yield quantitative images of tracer activity. Physical phenomena such as photon scatter, photon attenuation, random coincidences and spatial resolution limit quantification potential and must be corrected to preserve the accuracy of reconstructed images. This study focuses on correcting the partial volume effects that arise in mouse heart imaging when resolution is insufficient to resolve the true tracer distribution in the myocardium. The correction algorithm is based on fitting 1D profiles through the myocardium in gated PET images to derive myocardial contours along with blood, background and myocardial activity. This information is interpolated onto a 2D grid and convolved with the tomograph's point spread function to derive regional recovery coefficients enabling partial volume correction. The point spread function was measured by placing a line source inside a small animal PET scanner. PET simulations were created based on noise properties measured from a reconstructed PET image and on the digital MOBY phantom. The algorithm can estimate the myocardial activity to within 5% of the truth when different wall thicknesses, backgrounds and noise properties are encountered that are typical of healthy FDG mouse scans. The method also significantly improves partial volume recovery in simulated infarcted tissue. The algorithm offers a practical solution to the partial volume problem without the need for co-registered anatomic images and offers a basis for improved quantitative 3D heart imaging.

Optimization-based mesh correction with volume and convexity constraints

DOE PAGES

D'Elia, Marta; Ridzal, Denis; Peterson, Kara J.; ...

2016-02-24

In this study, we consider the problem of finding a mesh such that 1) it is the closest, with respect to a suitable metric, to a given source mesh having the same connectivity, and 2) the volumes of its cells match a set of prescribed positive values that are not necessarily equal to the cell volumes in the source mesh. This volume correction problem arises in important simulation contexts, such as satisfying a discrete geometric conservation law and solving transport equations by incremental remapping or similar semi-Lagrangian transport schemes. In this paper we formulate volume correction as a constrained optimizationmore » problem in which the distance to the source mesh defines an optimization objective, while the prescribed cell volumes, mesh validity and/or cell convexity specify the constraints. We solve this problem numerically using a sequential quadratic programming (SQP) method whose performance scales with the mesh size. To achieve scalable performance we develop a specialized multigrid-based preconditioner for optimality systems that arise in the application of the SQP method to the volume correction problem. Numerical examples illustrate the importance of volume correction, and showcase the accuracy, robustness and scalability of our approach.« less

Effects of posture on exercise performance - Measurement by systolic time intervals.

NASA Technical Reports Server (NTRS)

Spodick, D. H.; Quarry-Pigott, V. M.

1973-01-01

Because posture significantly influences cardiac performance, the effects of moderate supine and upright ergometer exercise were compared on the basis of proportional (+37%) rate increments over resting control. Supine exercise produced significant decreases in left ventricular ejection time (LVET), pre-ejection period (PEP), and isovolumic contraction time (IVCT). Ejection time index (ETI) and corrected ejection time (LVETc) did not change significantly. Upright exercise produced greater decreases in PEP and LVET, but despite the rate increase there was no change in LVET, which resulted in sharp increases in ETI and LVETc. The discordant directional effects on LVET and its rate-correcting indices between the two postures were consistent with hemodynamic studies demonstrating lack of stroke volume change during supine exercise and increased stroke volume over control during light to moderate upright exercise.

Intrafraction Prostate Translations and Rotations During Hypofractionated Robotic Radiation Surgery: Dosimetric Impact of Correction Strategies and Margins

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

Water, Steven van de, E-mail: s.vandewater@erasmusmc.nl; Valli, Lorella; Alma Mater Studiorum, Department of Physics and Astronomy, Bologna University, Bologna

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 alsomore » 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-mm margin but resulted in lower doses to rectum and bladder.« less

TH-A-9A-03: Dosimetric Effect of Rotational Errors for Lung Stereotactic Body Radiotherapy

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

Lee, J; Kim, H; Park, J

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 originalmore » 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 tissues than the translational correction.« less

The Blood Volume of the Guinea Pig: Effects of Epinephrine and Isoproterenol upon the Red Cell and Plasma Volumes, Heart Rate, and Mean Arterial Pressure,

DTIC Science & Technology

1987-09-01

capillaries (4), blood volumes calculated from plasma volume measures must correct for label that has left the system between the time of the injected dose...Splenic sequestration and contraction are mediated by the autonomic nervous system and blood-borne agents (10). Sympathetic nerve fibers from the truncus...sympathlcus and parasympathetic neurons of the nervus vagus (cranial nerve X) innervate the celiac plexus (8, 11). A subdivision of the celiac plexus

A mass-balanced definition of corrected retention volume in gas chromatography.

PubMed

Kurganov, A

2007-05-25

The mass balance equation of a chromatographic system using a compressible moving phase has been compiled for mass flow of the mobile phase instead of traditional volumetric flow allowing solution of the equation in an analytical form. The relation obtained correlates retention volume measured under ambient conditions with the partition coefficient of the solute. Compared to the relation in the ideal chromatographic system the equation derived contains an additional correction term accounting for the compressibility of the moving phase. When the retention volume is measured under the mean column pressure and column temperature the correction term is reduced to unit and the relation is simplified to those known for the ideal system. This volume according to International Union of Pure and Applied Chemistry (IUPAC) is called the corrected retention volume.

Genetic and environmental influence on thyroid gland volume and thickness of thyroid isthmus: a twin study.

PubMed

Tarnoki, Adam Domonkos; Tarnoki, David Laszlo; Speer, Gabor; Littvay, Levente; Bata, Pal; Garami, Zsolt; Berczi, Viktor; Karlinger, Kinga

2015-12-01

Decreased thyroid volume has been related to increased prevalence of thyroid cancer. One hundred and fourteen Hungarian adult twin pairs (69 monozygotic, 45 dizygotic) with or without known thyroid disorders underwent thyroid ultrasound. Thickness of the thyroid isthmus was measured at the thickest portion of the gland in the midline using electronic calipers at the time of scanning. Volume of the thyroid lobe was computed according to the following formula: thyroid height*width*depth*correction factor (0.63). Age-, sex-, body mass index- and smoking-adjusted heritability of the thickness of thyroid isthmus was 50% (95% confidence interval [CI], 35 to 66%). Neither left nor right thyroid volume showed additive genetic effects, but shared environments were 68% (95% CI, 48 to 80%) and 79% (95% CI, 72 to 87%), respectively. Magnitudes of monozygotic and dizygotic co-twin correlations were not substantially impacted by the correction of covariates of body mass index and smoking. Unshared environmental effects showed a moderate influence on dependent parameters (24-50%). Our analysis support that familial factors are important for thyroid measures in a general twin population. A larger sample size is needed to show whether this is because of common environmental (e.g. intrauterine effects, regional nutrition habits, iodine supply) or genetic effects.

Different partial volume correction methods lead to different conclusions: An (18)F-FDG-PET study of aging.

PubMed

Greve, Douglas N; Salat, David H; Bowen, Spencer L; Izquierdo-Garcia, David; Schultz, Aaron P; Catana, Ciprian; Becker, J Alex; Svarer, Claus; Knudsen, Gitte M; Sperling, Reisa A; Johnson, Keith A

2016-05-15

A cross-sectional group study of the effects of aging on brain metabolism as measured with (18)F-FDG-PET was performed using several different partial volume correction (PVC) methods: no correction (NoPVC), Meltzer (MZ), Müller-Gärtner (MG), and the symmetric geometric transfer matrix (SGTM) using 99 subjects aged 65-87years from the Harvard Aging Brain study. Sensitivity to parameter selection was tested for MZ and MG. The various methods and parameter settings resulted in an extremely wide range of conclusions as to the effects of age on metabolism, from almost no changes to virtually all of cortical regions showing a decrease with age. Simulations showed that NoPVC had significant bias that made the age effect on metabolism appear to be much larger and more significant than it is. MZ was found to be the same as NoPVC for liberal brain masks; for conservative brain masks, MZ showed few areas correlated with age. MG and SGTM were found to be similar; however, MG was sensitive to a thresholding parameter that can result in data loss. CSF uptake was surprisingly high at about 15% of that in gray matter. The exclusion of CSF from SGTM and MG models, which is almost universally done, caused a substantial loss in the power to detect age-related changes. This diversity of results reflects the literature on the metabolism of aging and suggests that extreme care should be taken when applying PVC or interpreting results that have been corrected for partial volume effects. Using the SGTM, significant age-related changes of about 7% per decade were found in frontal and cingulate cortices as well as primary visual and insular cortices. Copyright © 2016 Elsevier Inc. All rights reserved.

Different Partial Volume Correction Methods Lead to Different Conclusions: an 18F-FDG PET Study of Aging

PubMed Central

Greve, Douglas N.; Salat, David H.; Bowen, Spencer L.; Izquierdo-Garcia, David; Schultz, Aaron P.; Catana, Ciprian; Becker, J. Alex; Svarer, Claus; Knudsen, Gitte; Sperling, Reisa A.; Johnson, Keith A.

2016-01-01

A cross-sectional group study of the effects of aging on brain metabolism as measured with 18F-FDG PET was performed using several different partial volume correction (PVC) methods: no correction (NoPVC), Meltzer (MZ), Müller-Gärtner (MG), and the symmetric geometric transfer matrix (SGTM) using 99 subjects aged 65-87 from the Harvard Aging Brain study. Sensitivity to parameter selection was tested for MZ and MG. The various methods and parameter settings resulted in an extremely wide range of conclusions as to the effects of age on metabolism, from almost no changes to virtually all of cortical regions showing a decrease with age. Simulations showed that NoPVC had significant bias that made the age effect on metabolism appear to be much larger and more significant than it is. MZ was found to be the same as NoPVC for liberal brain masks; for conservative brain masks, MZ showed few areas correlated with age. MG and SGTM were found to be similar; however, MG was sensitive to a thresholding parameter that can result in data loss. CSF uptake was surprisingly high at about 15% of that in gray matter. Exclusion of CSF from SGTM and MG models, which is almost universally done, caused a substantial loss in the power to detect age-related changes. This diversity of results reflects the literature on the metabolism of aging and suggests that extreme care should be taken when applying PVC or interpreting results that have been corrected for partial volume effects. Using the SGTM, significant age-related changes of about 7% per decade were found in frontal and cingulate cortices as well as primary visual and insular cortices. PMID:26915497

Stochastic theory of large-scale enzyme-reaction networks: Finite copy number corrections to rate equation models

NASA Astrophysics Data System (ADS)

Thomas, Philipp; Straube, Arthur V.; Grima, Ramon

2010-11-01

Chemical reactions inside cells occur in compartment volumes in the range of atto- to femtoliters. Physiological concentrations realized in such small volumes imply low copy numbers of interacting molecules with the consequence of considerable fluctuations in the concentrations. In contrast, rate equation models are based on the implicit assumption of infinitely large numbers of interacting molecules, or equivalently, that reactions occur in infinite volumes at constant macroscopic concentrations. In this article we compute the finite-volume corrections (or equivalently the finite copy number corrections) to the solutions of the rate equations for chemical reaction networks composed of arbitrarily large numbers of enzyme-catalyzed reactions which are confined inside a small subcellular compartment. This is achieved by applying a mesoscopic version of the quasisteady-state assumption to the exact Fokker-Planck equation associated with the Poisson representation of the chemical master equation. The procedure yields impressively simple and compact expressions for the finite-volume corrections. We prove that the predictions of the rate equations will always underestimate the actual steady-state substrate concentrations for an enzyme-reaction network confined in a small volume. In particular we show that the finite-volume corrections increase with decreasing subcellular volume, decreasing Michaelis-Menten constants, and increasing enzyme saturation. The magnitude of the corrections depends sensitively on the topology of the network. The predictions of the theory are shown to be in excellent agreement with stochastic simulations for two types of networks typically associated with protein methylation and metabolism.

40 CFR 63.1203 - What are the standards for hazardous waste incinerators that are effective until compliance with...

Code of Federal Regulations, 2013 CFR

2013-07-01

... as propane; (6) Hydrochloric acid and chlorine gas in excess of 77 parts per million by volume, combined emissions, expressed as hydrochloric acid equivalents, dry basis and corrected to 7 percent oxygen... basis, corrected to 7 percent oxygen, and reported as propane; (6) Hydrochloric acid and chlorine gas in...

40 CFR 63.1203 - What are the standards for hazardous waste incinerators that are effective until compliance with...

Code of Federal Regulations, 2014 CFR

2014-07-01

... as propane; (6) Hydrochloric acid and chlorine gas in excess of 77 parts per million by volume, combined emissions, expressed as hydrochloric acid equivalents, dry basis and corrected to 7 percent oxygen... basis, corrected to 7 percent oxygen, and reported as propane; (6) Hydrochloric acid and chlorine gas in...

Anatomical-based partial volume correction for low-dose dedicated cardiac SPECT/CT

NASA Astrophysics Data System (ADS)

Liu, Hui; Chan, Chung; Grobshtein, Yariv; Ma, Tianyu; Liu, Yaqiang; Wang, Shi; Stacy, Mitchel R.; Sinusas, Albert J.; Liu, Chi

2015-09-01

Due to the limited spatial resolution, partial volume effect has been a major degrading factor on quantitative accuracy in emission tomography systems. This study aims to investigate the performance of several anatomical-based partial volume correction (PVC) methods for a dedicated cardiac SPECT/CT system (GE Discovery NM/CT 570c) with focused field-of-view over a clinically relevant range of high and low count levels for two different radiotracer distributions. These PVC methods include perturbation geometry transfer matrix (pGTM), pGTM followed by multi-target correction (MTC), pGTM with known concentration in blood pool, the former followed by MTC and our newly proposed methods, which perform the MTC method iteratively, where the mean values in all regions are estimated and updated by the MTC-corrected images each time in the iterative process. The NCAT phantom was simulated for cardiovascular imaging with 99mTc-tetrofosmin, a myocardial perfusion agent, and 99mTc-red blood cell (RBC), a pure intravascular imaging agent. Images were acquired at six different count levels to investigate the performance of PVC methods in both high and low count levels for low-dose applications. We performed two large animal in vivo cardiac imaging experiments following injection of 99mTc-RBC for evaluation of intramyocardial blood volume (IMBV). The simulation results showed our proposed iterative methods provide superior performance than other existing PVC methods in terms of image quality, quantitative accuracy, and reproducibility (standard deviation), particularly for low-count data. The iterative approaches are robust for both 99mTc-tetrofosmin perfusion imaging and 99mTc-RBC imaging of IMBV and blood pool activity even at low count levels. The animal study results indicated the effectiveness of PVC to correct the overestimation of IMBV due to blood pool contamination. In conclusion, the iterative PVC methods can achieve more accurate quantification, particularly for low count cardiac SPECT studies, typically obtained from low-dose protocols, gated studies, and dynamic applications.

Accurate Measurement of Small Airways on Low-Dose Thoracic CT Scans in Smokers

PubMed Central

Conradi, Susan H.; Atkinson, Jeffrey J.; Zheng, Jie; Schechtman, Kenneth B.; Senior, Robert M.; Gierada, David S.

2013-01-01

Background: Partial volume averaging and tilt relative to the scan plane on transverse images limit the accuracy of airway wall thickness measurements on CT scan, confounding assessment of the relationship between airway remodeling and clinical status in COPD. The purpose of this study was to assess the effect of partial volume averaging and tilt corrections on airway wall thickness measurement accuracy and on relationships between airway wall thickening and clinical status in COPD. Methods: Airway wall thickness measurements in 80 heavy smokers were obtained on transverse images from low-dose CT scan using the open-source program Airway Inspector. Measurements were corrected for partial volume averaging and tilt effects using an attenuation- and geometry-based algorithm and compared with functional status. Results: The algorithm reduced wall thickness measurements of smaller airways to a greater degree than larger airways, increasing the overall range. When restricted to analyses of airways with an inner diameter < 3.0 mm, for a theoretical airway of 2.0 mm inner diameter, the wall thickness decreased from 1.07 ± 0.07 to 0.29 ± 0.10 mm, and the square root of the wall area decreased from 3.34 ± 0.15 to 1.58 ± 0.29 mm, comparable to histologic measurement studies. Corrected measurements had higher correlation with FEV1, differed more between BMI, airflow obstruction, dyspnea, and exercise capacity (BODE) index scores, and explained a greater proportion of FEV1 variability in multivariate models. Conclusions: Correcting for partial volume averaging improves accuracy of airway wall thickness estimation, allowing direct measurement of the small airways to better define their role in COPD. PMID:23172175

Scalar and tensor perturbations in loop quantum cosmology: high-order corrections

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

Zhu, Tao; Wang, Anzhong; Wu, Qiang

2015-10-01

Loop quantum cosmology (LQC) provides promising resolutions to the trans-Planckian issue and initial singularity arising in the inflationary models of general relativity. In general, due to different quantization approaches, LQC involves two types of quantum corrections, the holonomy and inverse-volume, to both of the cosmological background evolution and perturbations. In this paper, using the third-order uniform asymptotic approximations, we derive explicitly the observational quantities of the slow-roll inflation in the framework of LQC with these quantum corrections. We calculate the power spectra, spectral indices, and running of the spectral indices for both scalar and tensor perturbations, whereby the tensor-to-scalar ratiomore » is obtained. We expand all the observables at the time when the inflationary mode crosses the Hubble horizon. As the upper error bounds for the uniform asymptotic approximation at the third-order are ∼< 0.15%, these results represent the most accurate results obtained so far in the literature. It is also shown that with the inverse-volume corrections, both scalar and tensor spectra exhibit a deviation from the usual shape at large scales. Then, using the Planck, BAO and SN data we obtain new constraints on quantum gravitational effects from LQC corrections, and find that such effects could be within the detection of the forthcoming experiments.« less

Effect of provider volume on the accuracy of hospital report cards: a Monte Carlo study.

PubMed

Austin, Peter C; Reeves, Mathew J

2014-03-01

Hospital report cards, in which outcomes after the provision of medical or surgical care are compared across healthcare providers, are being published with increasing frequency. However, the accuracy of such comparisons is controversial, especially when case volumes are small. The objective was to determine the relationship between hospital case volume and the accuracy of hospital report cards. Monte Carlo simulations were used to examine the influence of hospital case volume on the accuracy of hospital report cards in a setting in which true hospital performance was known with certainty, and perfect risk-adjustment was feasible. The parameters used to generate the simulated data sets were obtained from empirical analyses of data on patients hospitalized with acute myocardial infarction in Ontario, Canada, in which the overall 30-day mortality rate was 11.1%. We found that provider volume had a strong effect on the accuracy of hospital report cards. However, provider volume had to be >300 before ≥70% of hospitals were correctly classified. Furthermore, hospital volume had to be >1000 before ≥80% of hospitals were correctly classified. Producers and users of hospital report cards need to be aware that, even when perfect risk adjustment is possible, the accuracy of hospital report cards is, at best, modest for small to medium-sized case loads (i.e., 100-300). Hospital report cards displayed high degrees of accuracy only when provider volumes exceeded the typical annual hospital case load for many cardiovascular conditions and procedures.

[Continuous low volume infusion of hydroxyethyl starch as an option of water balance correction in patients with gestosis].

PubMed

Zhurova, A A; Ekstrem, A V; Popov, A S

2010-01-01

The method of long-term continuous low-volume infusion of hydroxyethyl starch (low-flow low volume correction HES) is administrated for correction of fluid balance disorders. The method is aimed to improve the outcomes in preeclamsia patients with multiple organ dysfunction and failure, as the most severe manifestation of system inflammatory response syndrome. After 4 days of the intensive care with application of the developed method in patients with preeclamsia the total body water level is decreased to the normal physiological level, the oedemas are significantly reduced or ceased, the haemodynamics stabilizes, which leads to the reduce of neurologic symptoms. The suggested method of low-flow low volume correction HES, in dose of 15 ml/kg/day is a significant addition to the existing methods of homeostasis and preeclampsia correction.

Issues in quantification of registered respiratory gated PET/CT in the lung.

PubMed

Cuplov, Vesna; Holman, Beverley F; McClelland, Jamie; Modat, Marc; Hutton, Brian F; Thielemans, Kris

2017-12-14

PET/CT quantification of lung tissue is limited by several difficulties: the lung density and local volume changes during respiration, the anatomical mismatch between PET and CT and the relative contributions of tissue, air and blood to the PET signal (the tissue fraction effect). Air fraction correction (AFC) has been shown to improve PET image quantification in the lungs. Methods to correct for the movement and anatomical mismatch involve respiratory gating and image registration techniques. While conventional registration methods only account for spatial mismatch, the Jacobian determinant of the deformable registration transformation field can be used to estimate local volume changes and could therefore potentially be used to correct (i.e. Jacobian Correction, JC) the PET signal for changes in concentration due to local volume changes. This work aims to investigate the relationship between variations in the lung due to respiration, specifically density, tracer concentration and local volume changes. In particular, we study the effect of AFC and JC on PET quantitation after registration of respiratory gated PET/CT patient data. Six patients suffering from lung cancer with solitary pulmonary nodules underwent [Formula: see text]F-FDG PET/cine-CT. The PET data were gated into six respiratory gates using displacement gating based on a real-time position management (RPM) signal and reconstructed with matched gated CT. The PET tracer concentration and tissue density were extracted from registered gated PET and CT images before and after corrections (AFC or JC) and compared to the values from the reference images. Before correction, we observed a linear correlation between the PET tracer concentration values and density. Across all gates and patients, the maximum relative change in PET tracer concentration before (after) AFC was found to be 16.2% (4.1%) and the maximum relative change in tissue density and PET tracer concentration before (after) JC was found to be 17.1% (5.5%) and 16.2% (6.8%) respectively. Overall our results show that both AFC or JC largely explain the observed changes in PET tracer activity over the respiratory cycle. We also speculate that a second order effect is related to change in fluid content but this needs further investigation. Consequently, either AFC or JC is recommended when combining lung PET images from different gates to reduce noise.

Issues in quantification of registered respiratory gated PET/CT in the lung

NASA Astrophysics Data System (ADS)

Cuplov, Vesna; Holman, Beverley F.; McClelland, Jamie; Modat, Marc; Hutton, Brian F.; Thielemans, Kris

2018-01-01

PET/CT quantification of lung tissue is limited by several difficulties: the lung density and local volume changes during respiration, the anatomical mismatch between PET and CT and the relative contributions of tissue, air and blood to the PET signal (the tissue fraction effect). Air fraction correction (AFC) has been shown to improve PET image quantification in the lungs. Methods to correct for the movement and anatomical mismatch involve respiratory gating and image registration techniques. While conventional registration methods only account for spatial mismatch, the Jacobian determinant of the deformable registration transformation field can be used to estimate local volume changes and could therefore potentially be used to correct (i.e. Jacobian Correction, JC) the PET signal for changes in concentration due to local volume changes. This work aims to investigate the relationship between variations in the lung due to respiration, specifically density, tracer concentration and local volume changes. In particular, we study the effect of AFC and JC on PET quantitation after registration of respiratory gated PET/CT patient data. Six patients suffering from lung cancer with solitary pulmonary nodules underwent 18 F-FDG PET/cine-CT. The PET data were gated into six respiratory gates using displacement gating based on a real-time position management (RPM) signal and reconstructed with matched gated CT. The PET tracer concentration and tissue density were extracted from registered gated PET and CT images before and after corrections (AFC or JC) and compared to the values from the reference images. Before correction, we observed a linear correlation between the PET tracer concentration values and density. Across all gates and patients, the maximum relative change in PET tracer concentration before (after) AFC was found to be 16.2% (4.1%) and the maximum relative change in tissue density and PET tracer concentration before (after) JC was found to be 17.1% (5.5%) and 16.2% (6.8%) respectively. Overall our results show that both AFC or JC largely explain the observed changes in PET tracer activity over the respiratory cycle. We also speculate that a second order effect is related to change in fluid content but this needs further investigation. Consequently, either AFC or JC is recommended when combining lung PET images from different gates to reduce noise.

Improving the accuracy of CT dimensional metrology by a novel beam hardening correction method

NASA Astrophysics Data System (ADS)

Zhang, Xiang; Li, Lei; Zhang, Feng; Xi, Xiaoqi; Deng, Lin; Yan, Bin

2015-01-01

Its powerful nondestructive characteristics are attracting more and more research into the study of computed tomography (CT) for dimensional metrology, which offers a practical alternative to the common measurement methods. However, the inaccuracy and uncertainty severely limit the further utilization of CT for dimensional metrology due to many factors, among which the beam hardening (BH) effect plays a vital role. This paper mainly focuses on eliminating the influence of the BH effect in the accuracy of CT dimensional metrology. To correct the BH effect, a novel exponential correction model is proposed. The parameters of the model are determined by minimizing the gray entropy of the reconstructed volume. In order to maintain the consistency and contrast of the corrected volume, a punishment term is added to the cost function, enabling more accurate measurement results to be obtained by the simple global threshold method. The proposed method is efficient, and especially suited to the case where there is a large difference in gray value between material and background. Different spheres with known diameters are used to verify the accuracy of dimensional measurement. Both simulation and real experimental results demonstrate the improvement in measurement precision. Moreover, a more complex workpiece is also tested to show that the proposed method is of general feasibility.

Experimental investigation of factors affecting the absolute recovery coefficients in iodine-124 PET lesion imaging

NASA Astrophysics Data System (ADS)

Jentzen, Walter

2010-04-01

The use of recovery coefficients (RCs) in 124I PET lesion imaging is a simple method to correct the imaged activity concentration (AC) primarily for the partial-volume effect and, to a minor extent, for the prompt gamma coincidence effect. The aim of this phantom study was to experimentally investigate a number of various factors affecting the 124I RCs. Three RC-based correction approaches were considered. These approaches differ with respect to the volume of interest (VOI) drawn, which determines the imaged AC and the RCs: a single voxel VOI containing the maximum value (maximum RC), a spherical VOI with a diameter of the scanner resolution (resolution RC) and a VOI equaling the physical object volume (isovolume RC). Measurements were performed using mainly a stand-alone PET scanner (EXACT HR+) and a latest-generation PET/CT scanner (BIOGRAPH mCT). The RCs were determined using a cylindrical phantom containing spheres or rotational ellipsoids and were derived from images acquired with a reference acquisition protocol. For each type of RC, the influence of the following factors on the RC was assessed: object shape, background activity spill in and iterative image reconstruction parameters. To evaluate the robustness of the RC-based correction approaches, the percentage deviation between RC-corrected and true ACs was determined from images acquired with a clinical acquisition protocol of different AC regimes. The observed results of the shape and spill-in effects were compared with simulation data derived from a convolution-based model. The study demonstrated that the shape effect was negligible and, therefore, was in agreement with theoretical expectations. In contradiction to the simulation results, the observed spill-in effect was unexpectedly small. To avoid variations in the determination of RCs due to reconstruction parameter changes, image reconstruction with a pixel length of about one-third or less of the scanner resolution and an OSEM 1 × 32 algorithm or one with somewhat higher number of effective iterations are recommended. Using the clinical acquisition protocol, the phantom study indicated that the resolution- or isovolume-based recovery-correction approaches appeared to be more appropriate to recover the ACs from patient data; however, the application of the three RC-based correction approaches to small lesions containing low ACs was, in particular, associated with large underestimations. The phantom study had several limitations, which were discussed in detail.

40 CFR 63.1205 - What are the standards for hazardous waste burning lightweight aggregate kilns that are effective...

Code of Federal Regulations, 2013 CFR

2013-07-01

... as propane; (6) Hydrochloric acid and chlorine gas in excess of 600 parts per million by volume, combined emissions, expressed as hydrochloric acid equivalents, dry basis and corrected to 7 percent oxygen...) Hydrochloric acid and chlorine gas in excess of 600 parts per million by volume, combined emissions, expressed...

40 CFR 63.1205 - What are the standards for hazardous waste burning lightweight aggregate kilns that are effective...

Code of Federal Regulations, 2014 CFR

2014-07-01

... as propane; (6) Hydrochloric acid and chlorine gas in excess of 600 parts per million by volume, combined emissions, expressed as hydrochloric acid equivalents, dry basis and corrected to 7 percent oxygen...) Hydrochloric acid and chlorine gas in excess of 600 parts per million by volume, combined emissions, expressed...

A potential means of improving the evaluation of deformity corrections with Taylor spatial frames over time by using volumetric imaging: preliminary results.

PubMed

Starr, Vanessa; Olivecrona, H; Noz, M E; Maguire, G Q; Zeleznik, M P; Jannsson, Karl-åke

2009-01-01

In this study we explore the possibility of accurately and cost-effectively monitoring tibial deformation induced by Taylor Spatial Frames (TSFs), using time-separated computed tomography (CT) scans and a volume fusion technique to determine tibial rotation and translation. Serial CT examinations (designated CT-A and CT-B, separated by a time interval of several months) of two patients were investigated using a previously described and validated volume fusion technique, in which user-defined landmarks drive the 3D registration of the two CT volumes. Both patients had undergone dual osteotomies to correct for tibial length and rotational deformity. For each registration, 10 or more landmarks were selected, and the quality of the fused volume was assessed both quantitatively and via 2D and 3D visualization tools. First, the proximal frame segment and tibia in CT-A and CT-B were brought into alignment (registered) by selecting landmarks on the frame and/or tibia. In the resulting "fused" volume, the proximal frame segment and tibia from CT-A and CT-B were aligned, while the distal frame segment and tibia from CT-A and CT-B were likely not aligned as a result of tibial deformation or frame adjustment having occurred between the CT scans. Using the proximal fused volume, the distal frame segment and tibia were then registered by selecting landmarks on the frame and/or tibia. The difference between the centroids of the final distal landmarks was used to evaluate the lengthening of the tibia, and the Euler angles from the registration were used to evaluate the rotation. Both the frame and bone could be effectively registered (based on visual interpretation). Movement between the proximal frame and proximal bone could be visualized in both cases. The spatial effect on the tibia could be both visually assessed and measured: 34 mm, 10 degrees in one case; 5 mm, 1 degrees in the other. This retrospective analysis of spatial correction of the tibia using Taylor Spatial Frames shows that CT offers an interesting potential means of quantitatively monitoring the patient's treatment. Compared with traditional techniques, modern CT scans in conjunction with image processing provide a high-resolution, spatially correct, and three-dimensional measurement system which can be used to quickly and easily assess the patient's treatment at low cost to the patient and hospital.

Spectral-Based Volume Sensor Prototype, Post-VS4 Test Series Algorithm Development

DTIC Science & Technology

2009-04-30

Computer Pcorr Probabilty / Percentage of Correct Classification (# Correct / # Total) PD PhotoDiode Pd Probabilty / Percentage of Detection (# Correct...Detections / Total of Sources) Pfa Probabilty / Percentage of False Alarm (# FAs / Total # of Sources) SBVS Spectral-Based Volume Sensor SFA Smoke and

The National Shipbuilding Research Program. 1985 Ship Production Symposium. Volume 1, Paper No. 13: Engineering Management for Zone Construction of Ships.

DTIC Science & Technology

1985-09-01

steadily developed along with the better understanding of human relations, moti- vation and worklife sciences. That this is so, is clear from a review of...accomplish its goals effectively and efficiently if it is not staffed with the correct number of people with the correct balance of education, training and

Correction of Motion Artifacts From Shuttle Mode Computed Tomography Acquisitions for Body Perfusion Imaging Applications.

PubMed

Ghosh, Payel; Chandler, Adam G; Altinmakas, Emre; Rong, John; Ng, Chaan S

2016-01-01

The aim of this study was to investigate the feasibility of shuttle-mode computed tomography (CT) technology for body perfusion applications by quantitatively assessing and correcting motion artifacts. Noncontrast shuttle-mode CT scans (10 phases, 2 nonoverlapping bed locations) were acquired from 4 patients on a GE 750HD CT scanner. Shuttling effects were quantified using Euclidean distances (between-phase and between-bed locations) of corresponding fiducial points on the shuttle and reference phase scans (prior to shuttle mode). Motion correction with nonrigid registration was evaluated using sum-of-squares differences and distances between centers of segmented volumes of interest on shuttle and references images. Fiducial point analysis showed an average shuttling motion of 0.85 ± 1.05 mm (between-bed) and 1.18 ± 1.46 mm (between-phase), respectively. The volume-of-interest analysis of the nonrigid registration results showed improved sum-of-squares differences from 2950 to 597, between-bed distance from 1.64 to 1.20 mm, and between-phase distance from 2.64 to 1.33 mm, respectively, averaged over all cases. Shuttling effects introduced during shuttle-mode CT acquisitions can be computationally corrected for body perfusion applications.

An analysis of the nucleon spectrum from lattice partially-quenched QCD

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

W. Armour; Allton, C. R.; Leinweber, Derek B.

2010-09-01

The chiral extrapolation of the nucleon mass, Mn, is investigated using data coming from 2-flavour partially-quenched lattice simulations. The leading one-loop corrections to the nucleon mass are derived for partially-quenched QCD. A large sample of lattice results from the CP-PACS Collaboration is analysed, with explicit corrections for finite lattice spacing artifacts. The extrapolation is studied using finite range regularised chiral perturbation theory. The analysis also provides a quantitative estimate of the leading finite volume corrections. It is found that the discretisation, finite-volume and partial quenching effects can all be very well described in this framework, producing an extrapolated value ofmore » Mn in agreement with experiment. This procedure is also compared with extrapolations based on polynomial forms, where the results are less encouraging.« less

Effect of extra-column volume on practical chromatographic parameters of sub-2-μm particle-packed columns in ultra-high pressure liquid chromatography.

PubMed

Wu, Naijun; Bradley, Ashley C; Welch, Christopher J; Zhang, Li

2012-08-01

Effects of extra-column volume on apparent separation parameters were studied in ultra-high pressure liquid chromatography with columns and inlet connection tubings of various internal diameters (id) using 50-mm long columns packed with 1.8-μm particles under isocratic conditions. The results showed that apparent retention factors were on average 5, 11, 18, and 41% lower than those corrected with extra-column volumes for 4.6-, 3.0-, 2.1-, and 1.0-mm id columns, respectively, when the extra-column volume (11.3 μL) was kept constant. Also, apparent pressures were 31, 16, 12, and 10% higher than those corrected with pressures from extra-column volumes for 4.6-, 3.0-, 2.1-, and 1.0-mm id columns at the respective optimum flow rate for a typical ultra-high pressure liquid chromatography system. The loss in apparent efficiency increased dramatically from 4.6- to 3.0- to 2.1- to 1.0-mm id columns, less significantly as retention factors increased. The column efficiency was significantly improved as the inlet tubing id was decreased for a given column. The results suggest that maximum ratio of extra-column volume to column void volume should be approximately 1:10 for column porosity more than 0.6 and a retention factor more than 5, where 80% or higher of theoretically predicted efficiency could be achieved. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fibre inflation and α-attractors

NASA Astrophysics Data System (ADS)

Kallosh, Renata; Linde, Andrei; Roest, Diederik; Westphal, Alexander; Yamada, Yusuke

2018-02-01

Fibre inflation is a specific string theory construction based on the Large Volume Scenario that produces an inflationary plateau. We outline its relation to α-attractor models for inflation, with the cosmological sector originating from certain string theory corrections leading to α = 2 and α = 1/2. Above a certain field range, the steepening effect of higher-order corrections leads first to the breakdown of single-field slow-roll and after that to the onset of 2-field dynamics: the overall volume of the extra dimensions starts to participate in the effective dynamics. Finally, we propose effective supergravity models of fibre inflation based on an \\overline{D3} uplift term with a nilpotent superfield. Specific moduli dependent \\overline{D3} induced geometries lead to cosmological fibre models but have in addition a de Sitter minimum exit. These supergravity models motivated by fibre inflation are relatively simple, stabilize the axions and disentangle the Hubble parameter from supersymmetry breaking.

Validation of a T1 and T2* leakage correction method based on multi-echo DSC-MRI using MION as a reference standard

PubMed Central

Stokes, Ashley M.; Semmineh, Natenael; Quarles, C. Chad

2015-01-01

Purpose A combined biophysical- and pharmacokinetic-based method is proposed to separate, quantify, and correct for both T1 and T2* leakage effects using dual-echo DSC acquisitions to provide more accurate hemodynamic measures, as validated by a reference intravascular contrast agent (CA). Methods Dual-echo DSC-MRI data were acquired in two rodent glioma models. The T1 leakage effects were removed and also quantified in order to subsequently correct for the remaining T2* leakage effects. Pharmacokinetic, biophysical, and combined biophysical and pharmacokinetic models were used to obtain corrected cerebral blood volume (CBV) and cerebral blood flow (CBF), and these were compared with CBV and CBF from an intravascular CA. Results T1-corrected CBV was significantly overestimated compared to MION CBV, while T1+T2*-correction yielded CBV values closer to the reference values. The pharmacokinetic and simplified biophysical methods showed similar results and underestimated CBV in tumors exhibiting strong T2* leakage effects. The combined method was effective for correcting T1 and T2* leakage effects across tumor types. Conclusions Correcting for both T1 and T2* leakage effects yielded more accurate measures of CBV. The combined correction method yields more reliable CBV measures than either correction method alone, but for certain brain tumor types (e.g., gliomas) the simplified biophysical method may provide a robust and computationally efficient alternative. PMID:26362714

40 CFR 60.54a - Standard for municipal waste combustor acid gases.

Code of Federal Regulations, 2010 CFR

2010-07-01

... for Municipal Waste Combustors for Which Construction is Commenced After December 20, 1989 and on or... weight or volume) or 30 parts per million by volume, corrected to 7 percent oxygen (dry basis), whichever... by volume, corrected to 7 percent oxygen (dry basis), whichever is less stringent. ...

SU-E-T-762: Toward Volume-Based Independent Dose Verification as Secondary Check

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

Tachibana, H; Tachibana, R

2015-06-15

Purpose: Lung SBRT plan has been shifted to volume prescription technique. However, point dose agreement is still verified using independent dose verification at the secondary check. The volume dose verification is more affected by inhomogeneous correction rather than point dose verification currently used as the check. A feasibility study for volume dose verification was conducted in lung SBRT plan. Methods: Six SBRT plans were collected in our institute. Two dose distributions with / without inhomogeneous correction were generated using Adaptive Convolve (AC) in Pinnacle3. Simple MU Analysis (SMU, Triangle Product, Ishikawa, JP) was used as the independent dose verification softwaremore » program, in which a modified Clarkson-based algorithm was implemented and radiological path length was computed using CT images independently to the treatment planning system. The agreement in point dose and mean dose between the AC with / without the correction and the SMU were assessed. Results: In the point dose evaluation for the center of the GTV, the difference shows the systematic shift (4.5% ± 1.9 %) in comparison of the AC with the inhomogeneous correction, on the other hands, there was good agreement of 0.2 ± 0.9% between the SMU and the AC without the correction. In the volume evaluation, there were significant differences in mean dose for not only PTV (14.2 ± 5.1 %) but also GTV (8.0 ± 5.1 %) compared to the AC with the correction. Without the correction, the SMU showed good agreement for GTV (1.5 ± 0.9%) as well as PTV (0.9% ± 1.0%). Conclusion: The volume evaluation for secondary check may be possible in homogenous region. However, the volume including the inhomogeneous media would make larger discrepancy. Dose calculation algorithm for independent verification needs to be modified to take into account the inhomogeneous correction.« less

The performance of the progressive resolution optimizer (PRO) for RapidArc planning in targets with low-density media.

PubMed

Kan, Monica W K; Leung, Lucullus H T; Yu, Peter K N

2013-11-04

A new version of progressive resolution optimizer (PRO) with an option of air cavity correction has been implemented for RapidArc volumetric-modulated arc therapy (RA). The purpose of this study was to compare the performance of this new PRO with the use of air cavity correction option (PRO10_air) against the one without the use of the air cavity correction option (PRO10_no-air) for RapidArc planning in targets with low-density media of different sizes and complexities. The performance of PRO10_no-air and PRO10_air was initially compared using single-arc plans created for four different simple heterogeneous phantoms with virtual targets and organs at risk. Multiple-arc planning of 12 real patients having nasopharyngeal carcinomas (NPC) and ten patients having non-small cell lung cancer (NSCLC) were then performed using the above two options for further comparison. Dose calculations were performed using both the Acuros XB (AXB) algorithm with the dose to medium option and the analytical anisotropic algorithm (AAA). The effect of using intermediate dose option after the first optimization cycle in PRO10_air and PRO10_no-air was also investigated and compared. Plans were evaluated and compared using target dose coverage, critical organ sparing, conformity index, and dose homogeneity index. For NSCLC cases or cases for which large volumes of low-density media were present in or adjacent to the target volume, the use of the air cavity correction option in PRO10 was shown to be beneficial. For NPC cases or cases for which small volumes of both low- and high-density media existed in the target volume, the use of air cavity correction in PRO10 did not improve the plan quality. Based on the AXB dose calculation results, the use of PRO10_air could produce up to 18% less coverage to the bony structures of the planning target volumes for NPC cases. When the intermediate dose option in PRO10 was used, there was negligible difference observed in plan quality between optimizations with and without using the air cavity correction option.

The human hippocampus is not sexually-dimorphic: Meta-analysis of structural MRI volumes.

PubMed

Tan, Anh; Ma, Wenli; Vira, Amit; Marwha, Dhruv; Eliot, Lise

2016-01-01

Hippocampal atrophy is found in many psychiatric disorders that are more prevalent in women. Sex differences in memory and spatial skills further suggest that males and females differ in hippocampal structure and function. We conducted the first meta-analysis of male-female difference in hippocampal volume (HCV) based on published MRI studies of healthy participants of all ages, to test whether the structure is reliably sexually dimorphic. Using four search strategies, we collected 68 matched samples of males' and females' uncorrected HCVs (in 4418 total participants), and 36 samples of male and female HCVs (2183 participants) that were corrected for individual differences in total brain volume (TBV) or intracranial volume (ICV). Pooled effect sizes were calculated using a random-effects model for left, right, and bilateral uncorrected HCVs and for left and right HCVs corrected for TBV or ICV. We found that uncorrected HCV was reliably larger in males, with Hedges' g values of 0.545 for left hippocampus, 0.526 for right hippocampus, and 0.557 for bilateral hippocampus. Meta-regression revealed no effect of age on the sex difference in left, right, or bilateral HCV. In the subset of studies that reported it, both TBV (g=1.085) and ICV (g=1.272) were considerably larger in males. Accordingly, studies reporting HCVs corrected for individual differences in TBV or ICV revealed no significant sex differences in left and right HCVs (Hedges' g ranging from +0.011 to -0.206). In summary, we found that human males of all ages exhibit a larger HCV than females, but adjusting for individual differences in TBV or ICV results in no reliable sex difference. The frequent claim that women have a disproportionately larger hippocampus than men was not supported. Copyright © 2015 Elsevier Inc. All rights reserved.

Improvement of the Correlative AFM and ToF-SIMS Approach Using an Empirical Sputter Model for 3D Chemical Characterization.

PubMed

Terlier, T; Lee, J; Lee, K; Lee, Y

2018-02-06

Technological progress has spurred the development of increasingly sophisticated analytical devices. The full characterization of structures in terms of sample volume and composition is now highly complex. Here, a highly improved solution for 3D characterization of samples, based on an advanced method for 3D data correction, is proposed. Traditionally, secondary ion mass spectrometry (SIMS) provides the chemical distribution of sample surfaces. Combining successive sputtering with 2D surface projections enables a 3D volume rendering to be generated. However, surface topography can distort the volume rendering by necessitating the projection of a nonflat surface onto a planar image. Moreover, the sputtering is highly dependent on the probed material. Local variation of composition affects the sputter yield and the beam-induced roughness, which in turn alters the 3D render. To circumvent these drawbacks, the correlation of atomic force microscopy (AFM) with SIMS has been proposed in previous studies as a solution for the 3D chemical characterization. To extend the applicability of this approach, we have developed a methodology using AFM-time-of-flight (ToF)-SIMS combined with an empirical sputter model, "dynamic-model-based volume correction", to universally correct 3D structures. First, the simulation of 3D structures highlighted the great advantages of this new approach compared with classical methods. Then, we explored the applicability of this new correction to two types of samples, a patterned metallic multilayer and a diblock copolymer film presenting surface asperities. In both cases, the dynamic-model-based volume correction produced an accurate 3D reconstruction of the sample volume and composition. The combination of AFM-SIMS with the dynamic-model-based volume correction improves the understanding of the surface characteristics. Beyond the useful 3D chemical information provided by dynamic-model-based volume correction, the approach permits us to enhance the correlation of chemical information from spectroscopic techniques with the physical properties obtained by AFM.

SU-E-T-223: Computed Radiography Dose Measurements of External Radiotherapy Beams

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

Aberle, C; Kapsch, R

2015-06-15

Purpose: To obtain quantitative, two-dimensional dose measurements of external radiotherapy beams with a computed radiography (CR) system and to derive volume correction factors for ionization chambers in small fields. Methods: A commercial Kodak ACR2000i CR system with Kodak Flexible Phosphor Screen HR storage foils was used. Suitable measurement conditions and procedures were established. Several corrections were derived, including image fading, length-scale corrections and long-term stability corrections. Dose calibration curves were obtained for cobalt, 4 MV, 8 MV and 25 MV photons, and for 10 MeV, 15 MeV and 18 MeV electrons in a water phantom. Inherent measurement inhomogeneities were studiedmore » as well as directional dependence of the response. Finally, 2D scans with ionization chambers were directly compared to CR measurements, and volume correction factors were derived. Results: Dose calibration curves (0.01 Gy to 7 Gy) were obtained for multiple photon and electron beam qualities. For each beam quality, the calibration curves can be described by a single fit equation over the whole dose range. The energy dependence of the dose response was determined. The length scale on the images was adjusted scan-by-scan, typically by 2 percent horizontally and by 3 percent vertically. The remaining inhomogeneities after the system’s standard calibration procedure were corrected for. After correction, the homogeneity is on the order of a few percent. The storage foils can be rotated by up to 30 degrees without a significant effect on the measured signal. First results on the determination of volume correction factors were obtained. Conclusion: With CR, quantitative, two-dimensional dose measurements with a high spatial resolution (sub-mm) can be obtained over a large dose range. In order to make use of these advantages, several calibrations, corrections and supporting measurements are needed. This work was funded by the European Metrology Research Programme (EMRP) project HLT09 MetrExtRT Metrology for Radiotherapy using Complex Radiation Fields.« less

An Allometric Analysis of Sex and Sex Chromosome Dosage Effects on Subcortical Anatomy in Humans.

PubMed

Reardon, Paul Kirkpatrick; Clasen, Liv; Giedd, Jay N; Blumenthal, Jonathan; Lerch, Jason P; Chakravarty, M Mallar; Raznahan, Armin

2016-02-24

Structural neuroimaging of humans with typical and atypical sex-chromosome complements has established the marked influence of both Yand X-/Y-chromosome dosage on total brain volume (TBV) and identified potential cortical substrates for the psychiatric phenotypes associated with sex-chromosome aneuploidy (SCA). Here, in a cohort of 354 humans with varying karyotypes (XX, XY, XXX, XXY, XYY, XXYY, XXXXY), we investigate sex and SCA effects on subcortical size and shape; focusing on the striatum, pallidum and thalamus. We find large effect-size differences in the volume and shape of all three structures as a function of sex and SCA. We correct for TBV effects with a novel allometric method harnessing normative scaling rules for subcortical size and shape in humans, which we derive here for the first time. We show that all three subcortical volumes scale sublinearly with TBV among healthy humans, mirroring known relationships between subcortical volume and TBV among species. Traditional TBV correction methods assume linear scaling and can therefore invert or exaggerate sex and SCA effects on subcortical anatomy. Allometric analysis restricts sex-differences to: (1) greater pallidal volume (PV) in males, and (2) relative caudate head expansion and ventral striatum contraction in females. Allometric analysis of SCA reveals that supernumerary X- and Y-chromosomes both cause disproportionate reductions in PV, and coordinated deformations of striatopallidal shape. Our study provides a novel understanding of sex and sex-chromosome dosage effects on subcortical organization, using an allometric approach that can be generalized to other basic and clinical structural neuroimaging settings. Copyright © 2016 the authors 0270-6474/16/362438-11$15.00/0.

Use of body plethysmography to measure effect of bimaxillary orthognathic surgery on airway resistance and lung volumes.

PubMed

Rezaeetalab, Fariba; Kazemian, Mozhgan; Vaezi, Touraj; Shaban, Barratollah

2015-12-01

Bimaxillary orthognathic surgery can cause changes to respiration and the airways. We used body plethysmography to evaluate its effect on airway resistance and lung volumes in 20 patients with class III malocclusions (8 men and 12 women, aged 17 - 32 years). Lung volumes (forced vital capacity; forced inspiratory volume/one second; forced expiratory volume/one second: forced vital capacity; peak expiratory flow; maximum expiratory flow 25-75; maximum inspiratory flow; total lung capacity; residual volume; residual volume:total lung capacity), and airway resistance were evaluated one week before, and six months after, operation. Bimaxillary operations to correct class III malocclusions significantly increased airway resistance, residual volume, total lung capacity, and residual volume:total lung capacity. Other variables also changed after operation but not significantly so. Orthognathic operations should be done with caution in patients who have pre-existing respiratory diseases. Copyright © 2015 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

Long space missions, gene therapy, and the vital role of magnesium: a three-pronged plan for the next 50 years

PubMed Central

Rowe, William J

2010-01-01

Since pharmaceuticals cannot be used in space until liver and kidney dysfunctions are corrected, and with invariable malabsorption, it appears there is no alternative other than to use subcutaneous magnesium (Mg) replacements in the presence of deficiencies and use of gene therapy. I suggest beginning with the correction of as many as four gene deficiencies: atrial natriuretic peptide (ANP), nitric oxide (NO), vascular endothelial growth factor (VEGF), and erythropoietin (EPO), all as well as Mg related to perfusion and angiogenesis. There is no evidence of significant lunar radiation levels in the absence of a solar storm. It could then be determined whether this has resulted in correction of liver and kidney dysfunction. If this persists, serial additions of gene therapy will be required determining the effect of each individual gene trial on organ function. Microgravity and endothelial gaps with leaks trigger reduced plasma volume. Partial correction by use of a plasma volume substitute and development of a delivery device may reduce complexity of gene therapy. Research would be conducted both on Earth and in microgravity, with the development of subcutaneous pharmaceuticals and Mg, and a space walk-reliable subcutaneous silicon device, given that no replenishable subcutaneous device is presently available. A three-pronged approach provides a plan for the next 50 years: A. complete correction of a Mg deficit; B. partial replacement with plasma volume substitutes, and C. multiple gene factor strategy. PMID:21694938

Long space missions, gene therapy, and the vital role of magnesium: a three-pronged plan for the next 50 years.

PubMed

Rowe, William J

2010-01-01

Since pharmaceuticals cannot be used in space until liver and kidney dysfunctions are corrected, and with invariable malabsorption, it appears there is no alternative other than to use subcutaneous magnesium (Mg) replacements in the presence of deficiencies and use of gene therapy. I suggest beginning with the correction of as many as four gene deficiencies: atrial natriuretic peptide (ANP), nitric oxide (NO), vascular endothelial growth factor (VEGF), and erythropoietin (EPO), all as well as Mg related to perfusion and angiogenesis. There is no evidence of significant lunar radiation levels in the absence of a solar storm. It could then be determined whether this has resulted in correction of liver and kidney dysfunction. If this persists, serial additions of gene therapy will be required determining the effect of each individual gene trial on organ function. Microgravity and endothelial gaps with leaks trigger reduced plasma volume. Partial correction by use of a plasma volume substitute and development of a delivery device may reduce complexity of gene therapy. Research would be conducted both on Earth and in microgravity, with the development of subcutaneous pharmaceuticals and Mg, and a space walk-reliable subcutaneous silicon device, given that no replenishable subcutaneous device is presently available. A three-pronged approach provides a plan for the next 50 years: A. complete correction of a Mg deficit; B. partial replacement with plasma volume substitutes, and C. multiple gene factor strategy. 2010 Halvorson et al, publisher and licensee Dove Medical Press Ltd.

A comparison of five partial volume correction methods for Tau and Amyloid PET imaging with [18F]THK5351 and [11C]PIB.

PubMed

Shidahara, Miho; Thomas, Benjamin A; Okamura, Nobuyuki; Ibaraki, Masanobu; Matsubara, Keisuke; Oyama, Senri; Ishikawa, Yoichi; Watanuki, Shoichi; Iwata, Ren; Furumoto, Shozo; Tashiro, Manabu; Yanai, Kazuhiko; Gonda, Kohsuke; Watabe, Hiroshi

2017-08-01

To suppress partial volume effect (PVE) in brain PET, there have been many algorithms proposed. However, each methodology has different property due to its assumption and algorithms. Our aim of this study was to investigate the difference among partial volume correction (PVC) method for tau and amyloid PET study. We investigated two of the most commonly used PVC methods, Müller-Gärtner (MG) and geometric transfer matrix (GTM) and also other three methods for clinical tau and amyloid PET imaging. One healthy control (HC) and one Alzheimer's disease (AD) PET studies of both [ 18 F]THK5351 and [ 11 C]PIB were performed using a Eminence STARGATE scanner (Shimadzu Inc., Kyoto, Japan). All PET images were corrected for PVE by MG, GTM, Labbé (LABBE), Regional voxel-based (RBV), and Iterative Yang (IY) methods, with segmented or parcellated anatomical information processed by FreeSurfer, derived from individual MR images. PVC results of 5 algorithms were compared with the uncorrected data. In regions of high uptake of [ 18 F]THK5351 and [ 11 C]PIB, different PVCs demonstrated different SUVRs. The degree of difference between PVE uncorrected and corrected depends on not only PVC algorithm but also type of tracer and subject condition. Presented PVC methods are straight-forward to implement but the corrected images require careful interpretation as different methods result in different levels of recovery.

Improved correction for the tissue fraction effect in lung PET/CT imaging

NASA Astrophysics Data System (ADS)

Holman, Beverley F.; Cuplov, Vesna; Millner, Lynn; Hutton, Brian F.; Maher, Toby M.; Groves, Ashley M.; Thielemans, Kris

2015-09-01

Recently, there has been an increased interest in imaging different pulmonary disorders using PET techniques. Previous work has shown, for static PET/CT, that air content in the lung influences reconstructed image values and that it is vital to correct for this ‘tissue fraction effect’ (TFE). In this paper, we extend this work to include the blood component and also investigate the TFE in dynamic imaging. CT imaging and PET kinetic modelling are used to determine fractional air and blood voxel volumes in six patients with idiopathic pulmonary fibrosis. These values are used to illustrate best and worst case scenarios when interpreting images without correcting for the TFE. In addition, the fractional volumes were used to determine correction factors for the SUV and the kinetic parameters. These were then applied to the patient images. The kinetic parameters K1 and Ki along with the static parameter SUV were all found to be affected by the TFE with both air and blood providing a significant contribution to the errors. Without corrections, errors range from 34-80% in the best case and 29-96% in the worst case. In the patient data, without correcting for the TFE, regions of high density (fibrosis) appeared to have a higher uptake than lower density (normal appearing tissue), however this was reversed after air and blood correction. The proposed correction methods are vital for quantitative and relative accuracy. Without these corrections, images may be misinterpreted.

Massive Photons: An Infrared Regularization Scheme for Lattice QCD+QED.

PubMed

Endres, Michael G; Shindler, Andrea; Tiburzi, Brian C; Walker-Loud, André

2016-08-12

Standard methods for including electromagnetic interactions in lattice quantum chromodynamics calculations result in power-law finite-volume corrections to physical quantities. Removing these by extrapolation requires costly computations at multiple volumes. We introduce a photon mass to alternatively regulate the infrared, and rely on effective field theory to remove its unphysical effects. Electromagnetic modifications to the hadron spectrum are reliably estimated with a precision and cost comparable to conventional approaches that utilize multiple larger volumes. A significant overall cost advantage emerges when accounting for ensemble generation. The proposed method may benefit lattice calculations involving multiple charged hadrons, as well as quantum many-body computations with long-range Coulomb interactions.

Qualitative and quantitative evaluation of six algorithms for correcting intensity nonuniformity effects.

PubMed

Arnold, J B; Liow, J S; Schaper, K A; Stern, J J; Sled, J G; Shattuck, D W; Worth, A J; Cohen, M S; Leahy, R M; Mazziotta, J C; Rottenberg, D A

2001-05-01

The desire to correct intensity nonuniformity in magnetic resonance images has led to the proliferation of nonuniformity-correction (NUC) algorithms with different theoretical underpinnings. In order to provide end users with a rational basis for selecting a given algorithm for a specific neuroscientific application, we evaluated the performance of six NUC algorithms. We used simulated and real MRI data volumes, including six repeat scans of the same subject, in order to rank the accuracy, precision, and stability of the nonuniformity corrections. We also compared algorithms using data volumes from different subjects and different (1.5T and 3.0T) MRI scanners in order to relate differences in algorithmic performance to intersubject variability and/or differences in scanner performance. In phantom studies, the correlation of the extracted with the applied nonuniformity was highest in the transaxial (left-to-right) direction and lowest in the axial (top-to-bottom) direction. Two of the six algorithms demonstrated a high degree of stability, as measured by the iterative application of the algorithm to its corrected output. While none of the algorithms performed ideally under all circumstances, locally adaptive methods generally outperformed nonadaptive methods. Copyright 2001 Academic Press.

[Determination of ventricular volumes by a non-geometric method using gamma-cineangiography].

PubMed

Faivre, R; Cardot, J C; Baud, M; Verdenet, J; Berthout, P; Bidet, A C; Bassand, J P; Maurat, J P

1985-08-01

The authors suggest a new way of determining ventricular volume by a non-geometric method using gamma-cineangiography. The results obtained by this method were compared with those obtained by a geometric methods and contrast ventriculography in 94 patients. The new non-geometric method supposes that the radioactive tracer is evenly distributed in the cardiovascular system so that blood radioactivity levels can be measured. The ventricular volume is then equal to the ratio of radioactivity in the LV zone to that of 1 ml of blood. Comparison of the radionuclide and angiographic data in the first 60 patients showed systematic values--despite a satisfactory statistical correlation (r = 0.87, y = 0.30 X + 6.3). This underestimation is due to the phenomenon of attenuation related to the depth of the heart in the thoracic cage and to autoabsorption at source, the degree of which depends on the ventricular volume. An empirical method of calculation allows correction for these factors by taking into account absorption in the tissues by relating to body surface area and autoabsorption at source by correcting for the surface of isotopic ventricular projection expressed in pixels. Using the data of this empirical method, the correction formula for radionuclide ventricular volume is obtained by a multiple linear regression: corrected radionuclide volume = K X measured radionuclide volume (Formula: see text). This formula was applied in the following 34 patients. The correlation between the uncorrected and corrected radionuclide volumes and the angiographic volumes was improved (r = 0.65 vs r = 0.94) and the values were more accurate (y = 0.18 X + 26 vs y = 0.96 X + 1.5).(ABSTRACT TRUNCATED AT 250 WORDS)

Vector velocity volume flow estimation: Sources of error and corrections applied for arteriovenous fistulas.

PubMed

Jensen, Jonas; Olesen, Jacob Bjerring; Stuart, Matthias Bo; Hansen, Peter Møller; Nielsen, Michael Bachmann; Jensen, Jørgen Arendt

2016-08-01

A method for vector velocity volume flow estimation is presented, along with an investigation of its sources of error and correction of actual volume flow measurements. Volume flow errors are quantified theoretically by numerical modeling, through flow phantom measurements, and studied in vivo. This paper investigates errors from estimating volumetric flow using a commercial ultrasound scanner and the common assumptions made in the literature. The theoretical model shows, e.g. that volume flow is underestimated by 15%, when the scan plane is off-axis with the vessel center by 28% of the vessel radius. The error sources were also studied in vivo under realistic clinical conditions, and the theoretical results were applied for correcting the volume flow errors. Twenty dialysis patients with arteriovenous fistulas were scanned to obtain vector flow maps of fistulas. When fitting an ellipsis to cross-sectional scans of the fistulas, the major axis was on average 10.2mm, which is 8.6% larger than the minor axis. The ultrasound beam was on average 1.5mm from the vessel center, corresponding to 28% of the semi-major axis in an average fistula. Estimating volume flow with an elliptical, rather than circular, vessel area and correcting the ultrasound beam for being off-axis, gave a significant (p=0.008) reduction in error from 31.2% to 24.3%. The error is relative to the Ultrasound Dilution Technique, which is considered the gold standard for volume flow estimation for dialysis patients. The study shows the importance of correcting for volume flow errors, which are often made in clinical practice. Copyright © 2016 Elsevier B.V. All rights reserved.

The influence of kyphosis correction surgery on pulmonary function and thoracic volume.

PubMed

Zeng, Yan; Chen, Zhongqiang; Ma, Desi; Guo, Zhaoqing; Qi, Qiang; Li, Weishi; Sun, Chuiguo; Liu, Ning; White, Andrew P

2014-10-01

A clinical study. To measure the changes in pulmonary function and thoracic volume associated with surgical correction of kyphotic deformities. No prior study has focused on the pulmonary function and thoracic cavity volume before and after corrective surgery for kyphosis. Thirty-four patients with kyphosis underwent posterior deformity correction with instrumented fusion. Preoperative and postoperative pulmonary function was measured, and pulmonary function grade was evaluated as mild, significant, or severe. The change in preoperative to postoperative pulmonary function was analyzed, using 6 comparative subgroupings of patients on the basis of age, severity of kyphosis, location of kyphosis apex, length of follow-up time after surgery, degree of kyphosis correction, and number of segments fused. A second group of 19 patients also underwent posterior surgical correction of kyphosis, which had thoracic volume measured preoperatively and postoperatively with computed tomographic scanning. All of the pulmonary impairments were found to be restrictive. After surgery, most of the patients had improvement of the pulmonary function. Before surgery, the pulmonary function differences were found to be significant based on both severity of preoperative kyphosis (<60° vs. >60°) and location of the kyphosis apex (above T10 vs. below T10). Younger patients (younger than 35 yr) were more likely to exhibit statistically significant improvements in pulmonary function after surgery. However, thoracic volume was not significantly related to pulmonary function parameters. After surgery, average thoracic volume had no significant change. The major pulmonary impairment caused by kyphosis was found to be restrictive. Patients with kyphosis angle of 60° or greater or with kyphosis apex above T10 had more severe pulmonary dysfunction. Patients' age was significantly related to change in pulmonary function after surgery. However, the average thoracic volume had no significant change after surgery. 3.

Simulating effects of brain atrophy in longitudinal PET imaging with an anthropomorphic brain phantom

NASA Astrophysics Data System (ADS)

Jonasson, L. S.; Axelsson, J.; Riklund, K.; Boraxbekk, C. J.

2017-07-01

In longitudinal positron emission tomography (PET), the presence of volumetric changes over time can lead to an overestimation or underestimation of the true changes in the quantified PET signal due to the partial volume effect (PVE) introduced by the limited spatial resolution of existing PET cameras and reconstruction algorithms. Here, a 3D-printed anthropomorphic brain phantom with attachable striata in three sizes was designed to enable controlled volumetric changes. Using a method to eliminate the non-radioactive plastic wall, and manipulating BP levels by adding different number of events from list-mode acquisitions, we investigated the artificial volume dependence of BP due to PVE, and potential bias arising from varying BP. Comparing multiple reconstruction algorithms we found that a high-resolution ordered-subsets maximization algorithm with spatially variant point-spread function resolution modeling provided the most accurate data. For striatum, the BP changed by 0.08% for every 1% volume change, but for smaller volumes such as the posterior caudate the artificial change in BP was as high as 0.7% per 1% volume change. A simple gross correction for striatal volume is unsatisfactory, as the amplitude of the PVE on the BP differs depending on where in the striatum the change occurred. Therefore, to correctly interpret age-related longitudinal changes in the BP, we must account for volumetric changes also within a structure, rather than across the whole volume. The present 3D-printing technology, combined with the wall removal method, can be implemented to gain knowledge about the predictable bias introduced by the PVE differences in uptake regions of varying shape.

Cosmological perturbation effects on gravitational-wave luminosity distance estimates

NASA Astrophysics Data System (ADS)

Bertacca, Daniele; Raccanelli, Alvise; Bartolo, Nicola; Matarrese, Sabino

2018-06-01

Waveforms of gravitational waves provide information about a variety of parameters for the binary system merging. However, standard calculations have been performed assuming a FLRW universe with no perturbations. In reality this assumption should be dropped: we show that the inclusion of cosmological perturbations translates into corrections to the estimate of astrophysical parameters derived for the merging binary systems. We compute corrections to the estimate of the luminosity distance due to velocity, volume, lensing and gravitational potential effects. Our results show that the amplitude of the corrections will be negligible for current instruments, mildly important for experiments like the planned DECIGO, and very important for future ones such as the Big Bang Observer.

Lattice study of finite volume effect in HVP for muon g-2

NASA Astrophysics Data System (ADS)

Izubuchi, Taku; Kuramashi, Yoshinobu; Lehner, Christoph; Shintani, Eigo

2018-03-01

We study the finite volume effect of the hadronic vacuum polarization contribution to muon g-2, aμhvp, in lattice QCD by comparison with two different volumes, L4 = (5.4)4 and (8.1)4 fm4, at physical pion. We perform the lattice computation of highly precise vector-vector current correlator with optimized AMA technique on Nf = 2 + 1 PACS gauge configurations in Wilson-clover fermion and stout smeared gluon action at one lattice cut-off, a-1 = 2.33 GeV. We compare two integrals of aμhvp, momentum integral and time-slice summation, on the lattice and numerically show that the different size of finite volume effect appears between two methods. We also discuss the effect of backward-state propagation into the result of aμhvp with the different boundary condition. Our model-independent study suggest that the lattice computation at physical pion is important for correct estimate of finite volume and other lattice systematics in aμhvp.

CT-based renal volume and graft function after living-donor kidney transplantation: Is there a volume threshold to avoid?

PubMed

Dias, Jorge; Malheiro, Jorge; Almeida, Manuela; Dias, Leonídio; Silva-Ramos, Miguel; Martins, La Salete; Xambre, Luís; Castro-Henriques, António

2015-05-01

Donated kidney volume influences post-transplant outcomes and graft survival. We evaluated the relationship between living-donor kidney volume and recipient graft function at 12 months post-transplantation, exploring a volume threshold for a suboptimal graft function, and compared two different formulas of volume estimation. A retrospective analysis of 82 pairs of living-donor kidney transplants was conducted. Donor renal volumes were estimated from computerized tomography scans using the ellipsoid formula and the voxel counting technique. Linear and restricted cubic regression spline was used to analyze the association of volume with graft function. Additionally, we determined the correlation between the two volume estimation formulas and established a correction factor for the ellipsoid formula. Renal volume (adjusted to recipient BSA) had the strongest independent effect (B = 1.65 per 10 ml/m(2) increase, p value <0.001) on graft function at 12 months. The eGFR at 12 months was 52.5, 63.6 and 67.6 ml/min/1.73 m(2) for the low, medium and high volume ratio terciles, respectively (p value <0.001). The odds of a GFR <50 ml/min became significantly reduced with volumes above 145 cc/1.73 m(2). A strong positive correlation between the two formulas was identified (R(2) = 0.705), but the optimal correction factor for our cohort was 0.566. In a Caucasian population, higher donor kidney volumes estimated from preoperative CT scans are associated with higher recipient eGFRs at 12 months after live-donor transplantation. Using this criterion, transplant teams can potentially improve selection of living donors if multiple donors are available. However, the need for precise estimation of donor kidney volumes should not be overlooked.

The Coast Artillery Journal. Volume 66, Number 5, May 1927

DTIC Science & Technology

1927-05-01

We are losing our sense of propor- tion and computing to ounces from measurements accurate only to pounds. Pursuing this subject further, it is...assumed. 2. The wind effect is supposedly corrected for through the use of the wind computer . Actually the present wind computer does not fur- nish...unsuited for the application of the correction (the Model 1917 Data Computer ) by operators too busy with principal deflections to occupy themselves

Direct estimation of 17 O MR images (DIESIS) for quantification of oxygen metabolism in the human brain with partial volume correction.

PubMed

Kurzhunov, Dmitry; Borowiak, Robert; Reisert, Marco; Özen, Ali Caglar; Bock, Michael

2018-05-16

To provide a data post-processing method that corrects for partial volume effects (PVE) and fast T2* decay in dynamic 17 O MRI for the mapping of cerebral metabolic rates of oxygen consumption (CMRO 2 ). CMRO 2 is altered in neurodegenerative diseases and tumors and can be measured after 17 O gas inhalation using dynamic 17 O MRI. CMRO 2 quantification is difficult because of PVE. To correct for PVE, a direct estimation of the MR images (DIESIS) method is proposed and used in 4 dynamic 17 O MRI data sets of a healthy volunteer acquired on a 3T MRI system. With DIESIS, 17 O MR signal time curves in selected regions were directly estimated based on parcellation of a coregistered 1 H MPRAGE image. Profile likelihood analysis of the DIESIS method showed identifiability of CMRO 2 . In white matter (WM), DIESES reduced CMRO 2 from 0.97 ± 0.25 µmol/g tissue /min with Kaiser-Bessel gridding reconstruction to 0.85 ± 0.21 µmol/g tissue /min, whereas in gray matter (GM) it increases from 1.3 ± 0.31 µmol/g tissue /min to 1.86 ± 0.36 µmol/g tissue /min; both values are closer to the literature values from the 15 O-PET studies. DIESIS provided an increased separation of CMRO 2 values in GM and WM brain regions and corrected for partial volume effects in 17 O-MRI inhalation experiments. DIESIS could also be applied to more heterogeneous tissues such as glioblastomas if subregions of the tumor can be represented as additional parcels. © 2018 International Society for Magnetic Resonance in Medicine.

Doctors' confusion over ratios and percentages in drug solutions: the case for standard labelling

PubMed Central

Wheeler, Daniel Wren; Remoundos, Dionysios Dennis; Whittlestone, Kim David; Palmer, Michael Ian; Wheeler, Sarah Jane; Ringrose, Timothy Richard; Menon, David Krishna

2004-01-01

The different ways of expressing concentrations of drugs in solution, as ratios or percentages or mass per unit volume, are a potential cause of confusion that may contribute to dose errors. To assess doctors' understanding of what they signify, all active subscribers to doctors.net.uk, an online community exclusively for UK doctors, were invited to complete a brief web-based multiple-choice questionnaire that explored their familiarity with solutions of adrenaline (expressed as a ratio), lidocaine (expressed as a percentage) and atropine (expressed in mg per mL), and their ability to calculate the correct volume to administer in clinical scenarios relevant to all specialties. 2974 (24.6%) replied. The mean score achieved was 4.80 out of 6 (SD 1.38). Only 85.2% and 65.8% correctly identified the mass of drug in the adrenaline and lidocaine solutions, respectively, whilst 93.1% identified the correct concentration of atropine. More would have administered the correct volume of adrenaline and lidocaine in clinical scenarios (89.4% and 81.0%, respectively) but only 65.5% identified the correct volume of atropine. The labelling of drug solutions as ratios or percentages is antiquated and confusing. Labelling should be standardized to mass per unit volume. PMID:15286190

The performance of the progressive resolution optimizer (PRO) for RapidArc planning in targets with low‐density media

PubMed Central

Leung, Lucullus H.T.; Yu, Peter K.N.

2013-01-01

A new version of progressive resolution optimizer (PRO) with an option of air cavity correction has been implemented for RapidArc volumetric‐modulated arc therapy (RA). The purpose of this study was to compare the performance of this new PRO with the use of air cavity correction option (PRO10_air) against the one without the use of the air cavity correction option (PRO10_no‐air) for RapidArc planning in targets with low‐density media of different sizes and complexities. The performance of PRO10_no‐air and PRO10_air was initially compared using single‐arc plans created for four different simple heterogeneous phantoms with virtual targets and organs at risk. Multiple‐arc planning of 12 real patients having nasopharyngeal carcinomas (NPC) and ten patients having non‐small cell lung cancer (NSCLC) were then performed using the above two options for further comparison. Dose calculations were performed using both the Acuros XB (AXB) algorithm with the dose to medium option and the analytical anisotropic algorithm (AAA). The effect of using intermediate dose option after the first optimization cycle in PRO10_air and PRO10_no‐air was also investigated and compared. Plans were evaluated and compared using target dose coverage, critical organ sparing, conformity index, and dose homogeneity index. For NSCLC cases or cases for which large volumes of low‐density media were present in or adjacent to the target volume, the use of the air cavity correction option in PROIO was shown to be beneficial. For NPC cases or cases for which small volumes of both low‐ and high‐density media existed in the target volume, the use of air cavity correction in PRO10 did not improve the plan quality. Based on the AXB dose calculation results, the use of PRO10_air could produce up to 18% less coverage to the bony structures of the planning target volumes for NPC cases. When the intermediate dose option in PRO10 was used, there was negligible difference observed in plan quality between optimizations with and without using the air cavity correction option. PACS number: 87.55.D‐, 87.55.de, 87.56.N‐

SU-C-304-06: Determination of Intermediate Correction Factors for Three Dosimeters in Small Composite Photon Fields Used in Robotic Radiosurgery

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

Christiansen, E; Belec, J; Vandervoort, E

2015-06-15

Purpose: To calculate using Monte-Carlo the intermediate and total correction factors (CFs) for two microchambers and a plastic scintillator for composite fields delivered by the CyberKnife system. Methods: A linac model was created in BEAMnrc by matching percentage depth dose (PDD) curves and output factors (OFs) measured using an A16 microchamber with Monte Carlo calculations performed in egs-chamber to explicitly model detector response. Intermediate CFs were determined for the A16 and A26 microchambers and the W1 plastic scintillator in fourteen different composite fields inside a solid water phantom. Seven of these fields used a 5 mm diameter collimator; the remainingmore » fields employed a 7.5 mm collimator but were otherwise identical to the first seven. Intermediate CFs are reported relative to the respective CF for a 60 mm collimator (800 mm source to detector distance and 100 mm depth in water). Results: For microchambers in composite fields, the intermediate CFs that account for detector density and volume were the largest contributors to total CFs. The total CFs for the A26 were larger than those for the A16, especially for the 5 mm cone (1.227±0.003 to 1.144±0.004 versus 1.142±0.003 to 1.099±0.004), due to the A26’s larger active volume (0.015 cc) relative to the A16 (0.007 cc), despite the A26 using similar wall and electrode material. The W1 total and intermediate CFs are closer to unity, due to its smaller active volume and near water-equivalent composition, however, 3–4% detector volume corrections are required for 5 mm collimator fields. In fields using the 7.5 mm collimator, the correction is nearly eliminated for the W1 except for a non-isocentric field. Conclusion: Large and variable CFs are required for microchambers in small composite fields primarily due to density and volume effects. Corrections are reduced but not eliminated for a plastic scintillator in the same fields.« less

Simultaneous multi-slice combined with PROPELLER.

PubMed

Norbeck, Ola; Avventi, Enrico; Engström, Mathias; Rydén, Henric; Skare, Stefan

2018-08-01

Simultaneous multi-slice (SMS) imaging is an advantageous method for accelerating MRI scans, allowing reduced scan time, increased slice coverage, or high temporal resolution with limited image quality penalties. In this work we combine the advantages of SMS acceleration with the motion correction and artifact reduction capabilities of the PROPELLER technique. A PROPELLER sequence was developed with support for CAIPIRINHA and phase optimized multiband radio frequency pulses. To minimize the time spent on acquiring calibration data, both in-plane-generalized autocalibrating partial parallel acquisition (GRAPPA) and slice-GRAPPA weights for all PROPELLER blade angles were calibrated on a single fully sampled PROPELLER blade volume. Therefore, the proposed acquisition included a single fully sampled blade volume, with the remaining blades accelerated in both the phase and slice encoding directions without additional auto calibrating signal lines. Comparison to 3D RARE was performed as well as demonstration of 3D motion correction performance on the SMS PROPELLER data. We show that PROPELLER acquisitions can be efficiently accelerated with SMS using a short embedded calibration. The potential in combining these two techniques was demonstrated with a high quality 1.0 × 1.0 × 1.0 mm 3 resolution T 2 -weighted volume, free from banding artifacts, and capable of 3D retrospective motion correction, with higher effective resolution compared to 3D RARE. With the combination of SMS acceleration and PROPELLER imaging, thin-sliced reformattable T 2 -weighted image volumes with 3D retrospective motion correction capabilities can be rapidly acquired with low sensitivity to flow and head motion. Magn Reson Med 80:496-506, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

A step towards removing plasma volume variance from the Athlete's Biological Passport: The use of biomarkers to describe vascular volumes from a simple blood test.

PubMed

Lobigs, Louisa M; Sottas, Pierre-Edouard; Bourdon, Pitre C; Nikolovski, Zoran; El-Gingo, Mohamed; Varamenti, Evdokia; Peeling, Peter; Dawson, Brian; Schumacher, Yorck O

2018-02-01

The haematological module of the Athlete's Biological Passport (ABP) has significantly impacted the prevalence of blood manipulations in elite sports. However, the ABP relies on a number of concentration-based markers of erythropoiesis, such as haemoglobin concentration ([Hb]), which are influenced by shifts in plasma volume (PV). Fluctuations in PV contribute to the majority of biological variance associated with volumetric ABP markers. Our laboratory recently identified a panel of common chemistry markers (from a simple blood test) capable of describing ca 67% of PV variance, presenting an applicable method to account for volume shifts within anti-doping practices. Here, this novel PV marker was included into the ABP adaptive model. Over a six-month period (one test per month), 33 healthy, active males provided blood samples and performed the CO-rebreathing method to record PV (control). In the final month participants performed a single maximal exercise effort to promote a PV shift (mean PV decrease -17%, 95% CI -9.75 to -18.13%). Applying the ABP adaptive model, individualized reference limits for [Hb] and the OFF-score were created, with and without the PV correction. With the PV correction, an average of 66% of [Hb] within-subject variance is explained, narrowing the predicted reference limits, and reducing the number of atypical ABP findings post-exercise. Despite an increase in sensitivity there was no observed loss of specificity with the addition of the PV correction. The novel PV marker presented here has the potential to improve the ABP's rate of correct doping detection by removing the confounding effects of PV variance. Copyright © 2017 John Wiley & Sons, Ltd.

Quantitative Amyloid Imaging in Autosomal Dominant Alzheimer's Disease: Results from the DIAN Study Group.

PubMed

Su, Yi; Blazey, Tyler M; Owen, Christopher J; Christensen, Jon J; Friedrichsen, Karl; Joseph-Mathurin, Nelly; Wang, Qing; Hornbeck, Russ C; Ances, Beau M; Snyder, Abraham Z; Cash, Lisa A; Koeppe, Robert A; Klunk, William E; Galasko, Douglas; Brickman, Adam M; McDade, Eric; Ringman, John M; Thompson, Paul M; Saykin, Andrew J; Ghetti, Bernardino; Sperling, Reisa A; Johnson, Keith A; Salloway, Stephen P; Schofield, Peter R; Masters, Colin L; Villemagne, Victor L; Fox, Nick C; Förster, Stefan; Chen, Kewei; Reiman, Eric M; Xiong, Chengjie; Marcus, Daniel S; Weiner, Michael W; Morris, John C; Bateman, Randall J; Benzinger, Tammie L S

2016-01-01

Amyloid imaging plays an important role in the research and diagnosis of dementing disorders. Substantial variation in quantitative methods to measure brain amyloid burden exists in the field. The aim of this work is to investigate the impact of methodological variations to the quantification of amyloid burden using data from the Dominantly Inherited Alzheimer's Network (DIAN), an autosomal dominant Alzheimer's disease population. Cross-sectional and longitudinal [11C]-Pittsburgh Compound B (PiB) PET imaging data from the DIAN study were analyzed. Four candidate reference regions were investigated for estimation of brain amyloid burden. A regional spread function based technique was also investigated for the correction of partial volume effects. Cerebellar cortex, brain-stem, and white matter regions all had stable tracer retention during the course of disease. Partial volume correction consistently improves sensitivity to group differences and longitudinal changes over time. White matter referencing improved statistical power in the detecting longitudinal changes in relative tracer retention; however, the reason for this improvement is unclear and requires further investigation. Full dynamic acquisition and kinetic modeling improved statistical power although it may add cost and time. Several technical variations to amyloid burden quantification were examined in this study. Partial volume correction emerged as the strategy that most consistently improved statistical power for the detection of both longitudinal changes and across-group differences. For the autosomal dominant Alzheimer's disease population with PiB imaging, utilizing brainstem as a reference region with partial volume correction may be optimal for current interventional trials. Further investigation of technical issues in quantitative amyloid imaging in different study populations using different amyloid imaging tracers is warranted.

Quantitative Amyloid Imaging in Autosomal Dominant Alzheimer’s Disease: Results from the DIAN Study Group

PubMed Central

Su, Yi; Blazey, Tyler M.; Owen, Christopher J.; Christensen, Jon J.; Friedrichsen, Karl; Joseph-Mathurin, Nelly; Wang, Qing; Hornbeck, Russ C.; Ances, Beau M.; Snyder, Abraham Z.; Cash, Lisa A.; Koeppe, Robert A.; Klunk, William E.; Galasko, Douglas; Brickman, Adam M.; McDade, Eric; Ringman, John M.; Thompson, Paul M.; Saykin, Andrew J.; Ghetti, Bernardino; Sperling, Reisa A.; Johnson, Keith A.; Salloway, Stephen P.; Schofield, Peter R.; Masters, Colin L.; Villemagne, Victor L.; Fox, Nick C.; Förster, Stefan; Chen, Kewei; Reiman, Eric M.; Xiong, Chengjie; Marcus, Daniel S.; Weiner, Michael W.; Morris, John C.; Bateman, Randall J.; Benzinger, Tammie L. S.

2016-01-01

Amyloid imaging plays an important role in the research and diagnosis of dementing disorders. Substantial variation in quantitative methods to measure brain amyloid burden exists in the field. The aim of this work is to investigate the impact of methodological variations to the quantification of amyloid burden using data from the Dominantly Inherited Alzheimer’s Network (DIAN), an autosomal dominant Alzheimer’s disease population. Cross-sectional and longitudinal [11C]-Pittsburgh Compound B (PiB) PET imaging data from the DIAN study were analyzed. Four candidate reference regions were investigated for estimation of brain amyloid burden. A regional spread function based technique was also investigated for the correction of partial volume effects. Cerebellar cortex, brain-stem, and white matter regions all had stable tracer retention during the course of disease. Partial volume correction consistently improves sensitivity to group differences and longitudinal changes over time. White matter referencing improved statistical power in the detecting longitudinal changes in relative tracer retention; however, the reason for this improvement is unclear and requires further investigation. Full dynamic acquisition and kinetic modeling improved statistical power although it may add cost and time. Several technical variations to amyloid burden quantification were examined in this study. Partial volume correction emerged as the strategy that most consistently improved statistical power for the detection of both longitudinal changes and across-group differences. For the autosomal dominant Alzheimer’s disease population with PiB imaging, utilizing brainstem as a reference region with partial volume correction may be optimal for current interventional trials. Further investigation of technical issues in quantitative amyloid imaging in different study populations using different amyloid imaging tracers is warranted. PMID:27010959

Antidepressant exposure may protect against decrement in frontal gray matter volumes in geriatric depression.

PubMed

Lavretsky, Helen; Roybal, Donna J; Ballmaier, Martina; Toga, Arthur W; Kumar, Anand

2005-08-01

Depressed elderly patients with and without antidepressant exposure were compared to normal controls to examine the effects of prior antidepressant exposure on regional brain gray matter volumes using magnetic resonance imaging (MRI). The study was conducted from October 1999 to January 2003. Patients and controls were closely matched by age and education. They underwent comprehensive neuropsychiatric and physical examinations. Measures of the total frontal lobe and the frontal gray and white matter volumes corrected by the intracranial volume were obtained using MRI, together with clinical measures of medical burden. Historical information about prior exposure to antidepressant drugs was collected using multiple information sources. The groups were compared using multivariate analyses of covariance, controlling for age, sex, and medical burden. The study sample comprised 41 patients who met the DSM-IV criteria for major depressive disorder (32 women; 11 antidepressant exposure and 30 drug-naive; mean age 70.5 years) and 41 controls (20 women; mean age 72.2 years). In the multivariate analysis, the depressed group had smaller corrected orbitofrontal cortex (OFC) total and gray matter volumes compared to the controls (p < .01). However, depressed patients with prior antidepressant exposure had larger OFC gray matter volumes compared to drug-naive depressed patients, but smaller than those in normal controls (p = .005). This effect was not explained by the group differences in sex ratio, age at onset of depression, or the number or duration of depressive episodes. We observed larger OFC regional volumes in depressed patients exposed to antidepressants compared to the drug-naive depressed subjects, but smaller than those in age-matched controls. Antidepressant exposure may protect against gray matter loss in geriatric depression.

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

Daily, Michael D.; Olsen, Brett N.; Schlesinger, Paul H.

In mammalian cells cholesterol is essential for membrane function, but in excess can be cytototoxic. The cellular response to acute cholesterol loading involves biophysical-based mechanisms that regulate cholesterol levels, through modulation of the “activity” or accessibility of cholesterol to extra-membrane acceptors. Experiments and united atom (UA) simulations show that at high concentrations of cholesterol, lipid bilayers thin significantly and cholesterol availability to external acceptors increases substantially. Such cholesterol activation is critical to its trafficking within cells. Here we aim to reduce the computational cost to enable simulation of large and complex systems involved in cholesterol regulation, such as those includingmore » oxysterols and cholesterol-sensing proteins. To accomplish this, we have modified the published MARTINI coarse-grained force field to improve its predictions of cholesterol-induced changes in both macroscopic and microscopic properties of membranes. Most notably, MARTINI fails to capture both the (macroscopic) area condensation and membrane thickening seen at less than 30% cholesterol and the thinning seen above 40% cholesterol. The thinning at high concentration is critical to cholesterol activation. Microscopic properties of interest include cholesterol-cholesterol radial distribution functions (RDFs), tilt angle, and accessible surface area. First, we develop an “angle-corrected” model wherein we modify the coarse-grained bond angle potentials based on atomistic simulations. This modification significantly improves prediction of macroscopic properties, most notably the thickening/thinning behavior, and also slightly improves microscopic property prediction relative to MARTINI. Second, we add to the angle correction a “volume correction” by also adjusting phospholipid bond lengths to achieve a more accurate volume per molecule. The angle + volume correction substantially further improves the quantitative agreement of the macroscopic properties (area per molecule and thickness) with united atom simulations. However, this improvement also reduces the accuracy of microscopic predictions like radial distribution functions and cholesterol tilt below that of either MARTINI or the angle-corrected model. Thus, while both of our forcefield corrections improve MARTINI, the combined angle and volume correction should be used for problems involving sterol effects on the overall structure of the membrane, while our angle-corrected model should be used in cases where the properties of individual lipid and sterol models are critically important.« less

Meta-analysis reveals a lack of sexual dimorphism in human amygdala volume.

PubMed

Marwha, Dhruv; Halari, Meha; Eliot, Lise

2017-02-15

The amygdala plays a key role in many affective behaviors and psychiatric disorders that differ between men and women. To test whether human amygdala volume (AV) differs reliably between the sexes, we performed a systematic review and meta-analysis of AVs reported in MRI studies of age-matched healthy male and female groups. Using four search strategies, we identified 46 total studies (58 matched samples) from which we extracted effect sizes for the sex difference in AV. All data were converted to Hedges g values and pooled effect sizes were calculated using a random-effects model. Each dataset was further meta-regressed against study year and average participant age. We found that uncorrected amygdala volume is about 10% larger in males, with pooled sex difference effect sizes of g=0.581 for right amygdala (κ=28, n=2022), 0.666 for left amygdala (κ=28, n=2006), and 0.876 for bilateral amygdala (κ=16, n=1585) volumes (all p values < 0.001). However, this difference is comparable to the sex differences in intracranial volume (ICV; g=1.186, p<.001, 11.9% larger in males, κ=11) and total brain volume (TBV; g=1.278, p<0.001, 11.5% larger in males, κ=15) reported in subsets of the same studies, suggesting the sex difference in AV is a product of larger brain size in males. Among studies reporting AVs normalized for ICV or TBV, sex difference effect sizes were small and not statistically significant: g=0.171 for the right amygdala (p=0.206, κ=13, n=1560); 0.233 for the left amygdala (p=0.092, κ=12, n=1512); and 0.257 for bilateral volume (p=0.131, κ=5, n=1629). These values correspond to less than 0.1% larger corrected right AV and 2.5% larger corrected left AV in males compared to females. In summary, AV is not selectively enhanced in human males, as often claimed. Although we cannot rule out subtle male-female group differences, it is not accurate to refer to the human amygdala as "sexually dimorphic." Copyright © 2016 Elsevier Inc. All rights reserved.

PERSISTENT CURRENT EFFECT IN 15-16 T NB3SN ACCELERATOR DIPOLES AND ITS CORRECTION

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

Kashikhin, V. V.; Zlobin, A. V.

2016-11-08

Nb3Sn magnets with operating fields of 15-16 T are considered for the LHC Energy Doubler and a future Very High Energy pp Collider. Due to large coil volume, high critical current density and large superconducting (SC) filament size the persistent current effect is very large in Nb3Sn dipoles al low fields. This paper presents the results of analysis of the persistent current effect in the 15 T Nb3Sn dipole demonstrator being developed at FNAL, and describes different possibilities of its correction including passive SC wires, iron shims and coil geometry.

Calcium Hydroxylapatite Dermal Filler for Treatment of Dorsal Hand Volume Loss: Results From a 12-Month, Multicenter, Randomized, Blinded Trial.

PubMed

Goldman, Mitchel P; Moradi, Amir; Gold, Michael H; Friedmann, Daniel P; Alizadeh, Kaveh; Adelglass, Jeffrey M; Katz, Bruce E

2018-01-01

Calcium hydroxylapatite (CaHA) microspheres suspended in a carrier gel is an opaque dermal filler that has been used to provide immediate volume correction in the dorsal hands. To assess the safety and effectiveness of CaHA for the correction of volume loss in the hands up to 12 months. This multicenter, controlled, single-blind study (NCT01832090) included 114 subjects randomized 3:1 to CaHA treatment and untreated control groups. Effectiveness was assessed by blinded investigators using the validated Merz Hand Grading Scale (MHGS). Subject-reported improvement was assessed using the Global Aesthetic Improvement Scale. Effects of treatment on hand function were also assessed. A total of 75% of subjects achieved ≥1-point improvement on the MHGS (p < .0001) at 3 months (primary end point); this response was generally maintained through 12 months. Proportions of subjects reporting improvement ranged from 98% (3 months) to 86% (12 months). There were no clinically significant differences between control and CaHA-treated subjects in any hand function measure. Adverse events were generally expected, minor, short-lived, injection-related, and similar to those observed in previous CaHA clinical studies. Treatment with CaHA results in significant improvement in the appearance of the dorsal hand and is well tolerated.

Optimized statistical parametric mapping for partial-volume-corrected amyloid positron emission tomography in patients with Alzheimer's disease and Lewy body dementia

NASA Astrophysics Data System (ADS)

Oh, Jungsu S.; Kim, Jae Seung; Chae, Sun Young; Oh, Minyoung; Oh, Seung Jun; Cha, Seung Nam; Chang, Ho-Jong; Lee, Chong Sik; Lee, Jae Hong

2017-03-01

We present an optimized voxelwise statistical parametric mapping (SPM) of partial-volume (PV)-corrected positron emission tomography (PET) of 11C Pittsburgh Compound B (PiB), incorporating the anatomical precision of magnetic resonance image (MRI) and amyloid β (A β) burden-specificity of PiB PET. First, we applied region-based partial-volume correction (PVC), termed the geometric transfer matrix (GTM) method, to PiB PET, creating MRI-based lobar parcels filled with mean PiB uptakes. Then, we conducted a voxelwise PVC by multiplying the original PET by the ratio of a GTM-based PV-corrected PET to a 6-mm-smoothed PV-corrected PET. Finally, we conducted spatial normalizations of the PV-corrected PETs onto the study-specific template. As such, we increased the accuracy of the SPM normalization and the tissue specificity of SPM results. Moreover, lobar smoothing (instead of whole-brain smoothing) was applied to increase the signal-to-noise ratio in the image without degrading the tissue specificity. Thereby, we could optimize a voxelwise group comparison between subjects with high and normal A β burdens (from 10 patients with Alzheimer's disease, 30 patients with Lewy body dementia, and 9 normal controls). Our SPM framework outperformed than the conventional one in terms of the accuracy of the spatial normalization (85% of maximum likelihood tissue classification volume) and the tissue specificity (larger gray matter, and smaller cerebrospinal fluid volume fraction from the SPM results). Our SPM framework optimized the SPM of a PV-corrected A β PET in terms of anatomical precision, normalization accuracy, and tissue specificity, resulting in better detection and localization of A β burdens in patients with Alzheimer's disease and Lewy body dementia.

Volume dependence of N-body bound states

NASA Astrophysics Data System (ADS)

König, Sebastian; Lee, Dean

2018-04-01

We derive the finite-volume correction to the binding energy of an N-particle quantum bound state in a cubic periodic volume. Our results are applicable to bound states with arbitrary composition and total angular momentum, and in any number of spatial dimensions. The only assumptions are that the interactions have finite range. The finite-volume correction is a sum of contributions from all possible breakup channels. In the case where the separation is into two bound clusters, our result gives the leading volume dependence up to exponentially small corrections. If the separation is into three or more clusters, there is a power-law factor that is beyond the scope of this work, however our result again determines the leading exponential dependence. We also present two independent methods that use finite-volume data to determine asymptotic normalization coefficients. The coefficients are useful to determine low-energy capture reactions into weakly bound states relevant for nuclear astrophysics. Using the techniques introduced here, one can even extract the infinite-volume energy limit using data from a single-volume calculation. The derived relations are tested using several exactly solvable systems and numerical examples. We anticipate immediate applications to lattice calculations of hadronic, nuclear, and cold atomic systems.

TU-G-BRA-05: Predicting Volume Change of the Tumor and Critical Structures Throughout Radiation Therapy by CT-CBCT Registration with Local Intensity Correction

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

Park, S; Robinson, A; Kiess, A

2015-06-15

Purpose: The purpose of this study is to develop an accurate and effective technique to predict and monitor volume changes of the tumor and organs at risk (OARs) from daily cone-beam CTs (CBCTs). Methods: While CBCT is typically used to minimize the patient setup error, its poor image quality impedes accurate monitoring of daily anatomical changes in radiotherapy. Reconstruction artifacts in CBCT often cause undesirable errors in registration-based contour propagation from the planning CT, a conventional way to estimate anatomical changes. To improve the registration and segmentation accuracy, we developed a new deformable image registration (DIR) that iteratively corrects CBCTmore » intensities using slice-based histogram matching during the registration process. Three popular DIR algorithms (hierarchical B-spline, demons, optical flow) augmented by the intensity correction were implemented on a graphics processing unit for efficient computation, and their performances were evaluated on six head and neck (HN) cancer cases. Four trained scientists manually contoured nodal gross tumor volume (GTV) on the planning CT and every other fraction CBCTs for each case, to which the propagated GTV contours by DIR were compared. The performance was also compared with commercial software, VelocityAI (Varian Medical Systems Inc.). Results: Manual contouring showed significant variations, [-76, +141]% from the mean of all four sets of contours. The volume differences (mean±std in cc) between the average manual segmentation and four automatic segmentations are 3.70±2.30(B-spline), 1.25±1.78(demons), 0.93±1.14(optical flow), and 4.39±3.86 (VelocityAI). In comparison to the average volume of the manual segmentations, the proposed approach significantly reduced the estimation error by 9%(B-spline), 38%(demons), and 51%(optical flow) over the conventional mutual information based method (VelocityAI). Conclusion: The proposed CT-CBCT registration with local CBCT intensity correction can accurately predict the tumor volume change with reduced errors. Although demonstrated only on HN nodal GTVs, the results imply improved accuracy for other critical structures. This work was supported by NIH/NCI under grant R42CA137886.« less

Volumetric changes in the upper airway after bimaxillary surgery for skeletal class III malocclusions: a case series study using 3-dimensional cone-beam computed tomography.

PubMed

Lee, Yoonjung; Chun, Youn-Sic; Kang, Nara; Kim, Minji

2012-12-01

Postsurgical changes of the airway have become a great point of interest and often have been reported to be a predisposing factor for obstructive sleep apnea after mandibular setback surgery. The purpose of this study was to evaluate the 3-dimensional volumetric changes in the upper airway space of patients who underwent bimaxillary surgery to correct Class III malocclusions. This study was performed retrospectively in a group of patients who underwent bimaxillary surgery for Class III malocclusion and had full cone-beam computed tomographic (CBCT) images taken before surgery and 1 day, 3 months, and 6 months after surgery. The upper and lower parts of the airway volume and the diameters of the airway were measured from 2 different levels. Presurgical measurements and the amount of surgical correction were evaluated for their effect on airway volume. Data analyses were performed by analysis of variance and multiple stepwise regression analysis. The subjects included 21 patients (6 men and 15 women; mean age, 22.7 yrs). The surgeries were Le Fort I impaction (5.27 ± 2.58 mm impaction from the posterior nasal spine) and mandibular setback surgery (9.20 ± 4.60 mm set back from the pogonion). No statistically significant differences were found in the total airway volume for all time points. In contrast, the volume of the upper part showed an increase (12.35%) and the lower part showed a decrease (14.07%), with a statistically significant difference 6 months after surgery (P < .05). Predictor variables affecting the upper and lower parts of the airway volume were presurgical A point to Nasion-perpendicular (A to N-perp) and vertical surgical correction of the pogonion and the posterior nasal spine (P < .05). Bimaxillary surgery for the correction of Class III malocclusion affected the morphology by increasing the upper part and decreasing the lower part of the airway, but not the total volume. Copyright © 2012 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.

Partial volume correction using cortical surfaces

NASA Astrophysics Data System (ADS)

Blaasvær, Kamille R.; Haubro, Camilla D.; Eskildsen, Simon F.; Borghammer, Per; Otzen, Daniel; Ostergaard, Lasse R.

2010-03-01

Partial volume effect (PVE) in positron emission tomography (PET) leads to inaccurate estimation of regional metabolic activities among neighbouring tissues with different tracer concentration. This may be one of the main limiting factors in the utilization of PET in clinical practice. Partial volume correction (PVC) methods have been widely studied to address this issue. MRI based PVC methods are well-established.1 Their performance depend on the quality of the co-registration of the MR and PET dataset, on the correctness of the estimated point-spread function (PSF) of the PET scanner and largely on the performance of the segmentation method that divide the brain into brain tissue compartments.1, 2 In the present study a method for PVC is suggested, that utilizes cortical surfaces, to obtain detailed anatomical information. The objectives are to improve the performance of PVC, facilitate a study of the relationship between metabolic activity in the cerebral cortex and cortical thicknesses, and to obtain an improved visualization of PET data. The gray matter metabolic activity after performing PVC was recovered by 99.7 - 99.8 % , in relation to the true activity when testing on simple simulated data with different PSFs and by 97.9 - 100 % when testing on simulated brain PET data at different cortical thicknesses. When studying the relationship between metabolic activities and anatomical structures it was shown on simulated brain PET data, that it is important to correct for PVE in order to get the true relationship.

The influence of RBE variations in a clinical proton treatment plan for a hypopharynx cancer

NASA Astrophysics Data System (ADS)

Tilly, N.; Johansson, J.; Isacsson, U.; Medin, J.; Blomquist, E.; Grusell, E.; Glimelius, B.

2005-06-01

Currently, most clinical range-modulated proton beams are assumed to have a fixed overall relative biological effectiveness (RBE) of 1.1. However, it is well known that the RBE increases with depth in the spread-out Bragg peak (SOBP) and becomes about 10% higher than mid-SOBP RBE at 2 mm from the distal edge (Paganetti 2003 Technol. Cancer Res. Treat. 2 413-26) and can reach values of 1.3-1.4 in vitro at the distal edge (Robertson et al 1975 Cancer 35 1664-77, Courdi et al 1994 Br. J. Radiol. 67 800-4). We present a fast method for applying a variable RBE correction with linear energy transfer (LET) dependent tissue-specific parameters based on the αref/βref ratios suitable for implementation in a treatment planning system. The influence of applying this variable RBE correction on a clinical multiple beam proton dose plan is presented here. The treatment plan is evaluated by RBE weighted dose volume histograms (DVHs) and the calculation of tumour control probability (TCP) and normal tissue complication probability (NTCP) values. The variable RBE correction yields DVHs for the clinical target volumes (CTVs), a primary advanced hypopharynx cancer and subclinical disease in the lymph nodes, that are slightly higher than those achieved by multiplying the absorbed dose with RBE = 1.1. Although, more importantly, the RBE weighted DVH for an organ at risk, the spinal cord is considerably increased for the variable RBE. As the spinal cord in this particular case is located 8 mm behind the planning target volume (PTV) and hence receives only low total doses, the NTCP values are zero in spite of the significant increase in the RBE weighted DVHs for the variable RBE. However, high NTCP values for the non-target normal tissue were obtained when applying the variable RBE correction. As RBE variations tend to be smaller for in vivo systems, this study—based on in vitro data since human tissue RBE values are scarce and have large uncertainties—can be interpreted as showing the upper limits of the possible effects of utilizing a variable RBE correction. In conclusion, the results obtained here still indicate a significant difference in introducing a variable RBE compared to applying a generic RBE of 1.1, suggesting it is worth considering such a correction in clinical proton therapy planning, especially when risk organs are located immediately behind the target volume.

Effect of attenuation correction on image quality in emission tomography

NASA Astrophysics Data System (ADS)

Denisova, N. V.; Ondar, M. M.

2017-10-01

In this paper, mathematical modeling and computer simulations of myocardial perfusion SPECT imaging are performed. The main factors affecting the quality of reconstructed images in SPECT are anatomical structures, the diastolic volume of a myocardium and attenuation of gamma rays. The purpose of the present work is to study the effect of attenuation correction on image quality in emission tomography. The basic 2D model describing a Tc-99m distribution in a transaxial slice of the thoracic part of a patient body was designed. This model was used to construct four phantoms simulated various anatomical shapes: 2 male and 2 female patients with normal, obese and subtle physique were included in the study. Data acquisition model which includes the effect of non-uniform attenuation, collimator-detector response and Poisson statistics was developed. The projection data were calculated for 60 views in accordance with the standard myocardial perfusion SPECT imaging protocol. Reconstructions of images were performed using the OSEM algorithm which is widely used in modern SPECT systems. Two types of patient's examination procedures were simulated: SPECT without attenuation correction and SPECT/CT with attenuation correction. The obtained results indicate a significant effect of the attenuation correction on the SPECT images quality.

Use of bias correction techniques to improve seasonal forecasts for reservoirs - A case-study in northwestern Mediterranean.

PubMed

Marcos, Raül; Llasat, Ma Carmen; Quintana-Seguí, Pere; Turco, Marco

2018-01-01

In this paper, we have compared different bias correction methodologies to assess whether they could be advantageous for improving the performance of a seasonal prediction model for volume anomalies in the Boadella reservoir (northwestern Mediterranean). The bias correction adjustments have been applied on precipitation and temperature from the European Centre for Middle-range Weather Forecasting System 4 (S4). We have used three bias correction strategies: two linear (mean bias correction, BC, and linear regression, LR) and one non-linear (Model Output Statistics analogs, MOS-analog). The results have been compared with climatology and persistence. The volume-anomaly model is a previously computed Multiple Linear Regression that ingests precipitation, temperature and in-flow anomaly data to simulate monthly volume anomalies. The potential utility for end-users has been assessed using economic value curve areas. We have studied the S4 hindcast period 1981-2010 for each month of the year and up to seven months ahead considering an ensemble of 15 members. We have shown that the MOS-analog and LR bias corrections can improve the original S4. The application to volume anomalies points towards the possibility to introduce bias correction methods as a tool to improve water resource seasonal forecasts in an end-user context of climate services. Particularly, the MOS-analog approach gives generally better results than the other approaches in late autumn and early winter. Copyright © 2017 Elsevier B.V. All rights reserved.

Pragmatics: Teaching Speech Acts

ERIC Educational Resources Information Center

Tatsuki, Donna H., Ed.; Houck, Noel R., Ed.

2010-01-01

Language teachers have long been aware of the devastating effect of learners' grammatically correct, yet situationally inappropriate spoken or written communication. This volume addresses how to raise learner awareness of pragmatic gaffs through research-based, field-tested activities such as composing e-mail requests, giving advice, making…

You Sank My... Bacteriophage?

ERIC Educational Resources Information Center

Bokor, Julie

2012-01-01

Practicing correct pipetting procedure doesn't have to be boring. "Pipetting by Coordinates" is an effective way to teach necessary pipetting skills in an enjoyable manner. Students create designs as they add volumes of colored water to specific wells and gain experience using a basic biotechnology tool.

Apparent CBF decrease with normal aging due to partial volume effects: MR-based partial volume correction on CBF SPECT.

PubMed

Inoue, Kentaro; Ito, Hiroshi; Goto, Ryoi; Nakagawa, Manabu; Kinomura, Shigeo; Sato, Tachio; Sato, Kazunori; Fukuda, Hiroshi

2005-06-01

Several studies using single photon emission tomography (SPECT) have shown changes in cerebral blood flow (CBF) with age, which were associated with partial volume effects by some authors. Some studies have also demonstrated gender-related differences in CBF. The present study aimed to examine age and gender effects on CBF SPECT images obtained using the 99mTc-ethyl cysteinate dimer and a SPECT scanner, before and after partial volume correction (PVC) using magnetic resonance (MR) imaging. Forty-four healthy subjects (29 males and 15 females; age range, 27-64 y; mean age, 50.0 +/- 9.8 y) participated. Each MR image was segmented to yield grey and white matter images and coregistered to a corresponding SPECT image, followed by convolution to approximate the SPECT spatial resolution. PVC-SPECT images were produced using the convoluted grey matter MR (GM-MR) and white matter MR images. The age and gender effects were assessed using SPM99. Decreases with age were detected in the anterolateral prefrontal cortex and in areas along the lateral sulcus and the lateral ventricle, bilaterally, in the GM-MR images and the SPECT images. In the PVC-SPECT images, decreases in CBF in the lateral prefrontal cortex lost their statistical significance. Decreases in CBF with age found along the lateral sulcus and the lateral ventricle, on the other hand, remained statistically significant, but observation of the spatially normalized MR images suggests that these findings are associated with the dilatation of the lateral sulcus and lateral ventricle, which was not completely compensated for by the spatial normalization procedure. Our present study demonstrated that age effects on CBF in healthy subjects could reflect morphological differences with age in grey matter.

Beta-erythropoietin effects on ventricular remodeling, left and right systolic function, pulmonary pressure, and hospitalizations in patients affected with heart failure and anemia.

PubMed

Palazzuoli, Alberto; Silverberg, Donald S; Calabrò, Anna; Spinelli, Tommaso; Quatrini, Ilaria; Campagna, Maria S; Franci, Beatrice; Nuti, Ranuccio

2009-06-01

Anemia in heart failure is related to advanced New York Heart Association classes, severe systolic dysfunction, and reduced exercise tolerance. Although anemia is frequently found in congestive heart failure (CHF), little is known about the effect of its' correction with erythropoietin (EPO) on cardiac structure and function. The present study examines, in patients with advanced CHF and anemia, the effects of beta-EPO on left ventricular volumes, left ventricular ejection fraction (LVEF), left and right longitudinal function mitral anular plane systolic excursion (MAPSE), tricuspid anular plane excursion (TAPSE), and pulmonary artery pressures in 58 patients during 1-year follow-up in a double-blind controlled study of correction of anemia with subcutaneous beta-EPO. Echocardiographic evaluation, B-Type natriuretic peptide (BNP) levels, and hematological parameters are reported at 4 and 12 months. The patients in group A after 4 months of follow-up period demonstrated an increase in LVEF and MAPSE (P < 0.05 and P < 0.01, respectively) with left ventricular systolic volume reduction (P < 0.02) with respect to baseline and controls. After 12 months, results regarding left ventricular systolic volume LVEF and MAPSE persisted (P < 0.001). In addition, TAPSE increased and pulmonary artery pressures fell significantly in group A (P < 0.01). All these changes occurred together with a significant BNP reduction and significant hemoglobin increase in the treated group. Therefore, we revealed a reduced hospitalization rate in treated patients with respect to the controls (25% in treated vs. 54% in controls). In patients with anemia and CHF, correction of anemia with beta-EPO and oral iron over 1 year leads to an improvement in left and right ventricular systolic function by reducing cardiac remodeling, BNP levels, and hospitalization rate.

Beyond the plane-parallel and Newtonian approach: wide-angle redshift distortions and convergence in general relativity

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

Bertacca, Daniele; Maartens, Roy; Raccanelli, Alvise

We extend previous analyses of wide-angle correlations in the galaxy power spectrum in redshift space to include all general relativistic effects. These general relativistic corrections to the standard approach become important on large scales and at high redshifts, and they lead to new terms in the wide-angle correlations. We show that in principle the new terms can produce corrections of nearly 10% on Gpc scales over the usual Newtonian approximation. General relativistic corrections will be important for future large-volume surveys such as SKA and Euclid, although the problem of cosmic variance will present a challenge in observing this.

Investigation of electron-loss and photon scattering correction factors for FAC-IR-300 ionization chamber

NASA Astrophysics Data System (ADS)

Mohammadi, S. M.; Tavakoli-Anbaran, H.; Zeinali, H. Z.

2017-02-01

The parallel-plate free-air ionization chamber termed FAC-IR-300 was designed at the Atomic Energy Organization of Iran, AEOI. This chamber is used for low and medium X-ray dosimetry on the primary standard level. In order to evaluate the air-kerma, some correction factors such as electron-loss correction factor (ke) and photon scattering correction factor (ksc) are needed. ke factor corrects the charge loss from the collecting volume and ksc factor corrects the scattering of photons into collecting volume. In this work ke and ksc were estimated by Monte Carlo simulation. These correction factors are calculated for mono-energy photon. As a result of the simulation data, the ke and ksc values for FAC-IR-300 ionization chamber are 1.0704 and 0.9982, respectively.

Observational constraints on loop quantum cosmology.

PubMed

Bojowald, Martin; Calcagni, Gianluca; Tsujikawa, Shinji

2011-11-18

In the inflationary scenario of loop quantum cosmology in the presence of inverse-volume corrections, we give analytic formulas for the power spectra of scalar and tensor perturbations convenient to compare with observations. Since inverse-volume corrections can provide strong contributions to the running spectral indices, inclusion of terms higher than the second-order runnings in the power spectra is crucially important. Using the recent data of cosmic microwave background and other cosmological experiments, we place bounds on the quantum corrections.

Diminished gray matter in the hippocampus of cannabis users: possible protective effects of cannabidiol.

PubMed

Demirakca, Traute; Sartorius, Alexander; Ende, Gabriele; Meyer, Nadja; Welzel, Helga; Skopp, Gisela; Mann, Karl; Hermann, Derik

2011-04-01

Chronic cannabis use has been associated with memory deficits and a volume reduction of the hippocampus, but none of the studies accounted for different effects of tetrahydrocannabinol (THC) and cannabidiol (CBD). Using a voxel based morphometry approach optimized for small subcortical structures (DARTEL) gray matter (GM) concentration and volume of the hippocampus were measured in 11 chronic recreational cannabis users and 13 healthy controls, and correlated with THC and CBD from hair analyses. GM volume was calculated by modulating VBM using Jacobian determinants derived from the spatial normalization. Cannabis users showed lower GM volume located in a cluster of the right anterior hippocampus (P(uncorr)=0.002; effect size Cohen's d=1.34). In a regression analysis an inverse correlation of the ratio THC/CBD with the volume of the right hippocampus (P(uncorr) p<0.001, Cohen's d=3.43) was observed. Furthermore Cannabidiol correlated positively with GM concentration (unmodulated VBM data), but not with GM volume (modulated VBM) in the bilateral hippocampus (P=0.03 after correction for hippocampal volume; left hippocampus Cohen's d=4.37 and right hippocampus 4.65). Lower volume in the right hippocampus in chronic cannabis users was corroborated. Higher THC and lower CBD was associated with this volume reduction indicating neurotoxic effects of THC and neuroprotective effects of CBD. This confirms existing preclinical and clinical results. As a possible mechanism the influence of cannabinoids on hippocampal neurogenesis is suggested. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

Target coverage in image-guided stereotactic body radiotherapy of liver tumors.

PubMed

Wunderink, Wouter; Méndez Romero, Alejandra; Vásquez Osorio, Eliana M; de Boer, Hans C J; Brandwijk, René P; Levendag, Peter C; Heijmen, Ben J M

2007-05-01

To determine the effect of image-guided procedures (with computed tomography [CT] and electronic portal images before each treatment fraction) on target coverage in stereotactic body radiotherapy for liver patients using a stereotactic body frame (SBF) and abdominal compression. CT guidance was used to correct for day-to-day variations in the tumor's mean position in the SBF. By retrospectively evaluating 57 treatment sessions, tumor coverage, as obtained with the clinically applied CT-guided protocol, was compared with that of alternative procedures. The internal target volume-plus (ITV(+)) was introduced to explicitly include uncertainties in tumor delineations resulting from CT-imaging artifacts caused by residual respiratory motion. Tumor coverage was defined as the volume overlap of the ITV(+), derived from a tumor delineated in a treatment CT scan, and the planning target volume. Patient stability in the SBF, after acquisition of the treatment CT scan, was evaluated by measuring the displacement of the bony anatomy in the electronic portal images relative to CT. Application of our clinical protocol (with setup corrections following from manual measurements of the distances between the contours of the planning target volume and the daily clinical target volume in three orthogonal planes, multiple two-dimensional) increased the frequency of nearly full (> or = 99%) ITV(+) coverage to 77% compared with 63% without setup correction. An automated three-dimensional method further improved the frequency to 96%. Patient displacements in the SBF were generally small (< or = 2 mm, 1 standard deviation), but large craniocaudal displacements (maximal 7.2 mm) were occasionally observed. Daily, CT-assisted patient setup may substantially improve tumor coverage, especially with the automated three-dimensional procedure. In the present treatment design, patient stability in the SBF should be verified with portal imaging.

Project SQUID: The Foundations of Nonequilibrium Statistical Mechanics. Volume 1

DTIC Science & Technology

1963-06-01

equations available (Boltzmann, Landau,, Bogolubov- Balescu -Lenard) are essentially exact and cannot be improved. That isv for kinetic gases (those...effects) as well as to the newly obtained kinetic equation for plasmas (8) (Bogolubov- Balescu -Lenard equation). The hope of ob- taining correctly

76 FR 15553 - National Emission Standards for Hazardous Air Pollutants for Area Sources: Industrial, Commercial...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-21

... unpredictability of the non-mercury metal HAP compositions and amounts in fuel has a material effect on the... heat input. c. Carbon 400 ppm by volume on a dry basis corrected Monoxide. to 3 percent oxygen. >=10... 15560

TEMPERATURE CORRECTION FORMULAE FOR ADJUSTING ESTIMATES OF EMISSIONS FROM AUTOMOBILES. VOLUME I

EPA Science Inventory

This report describes an analysis of the effects of temperature on the emissions of hydrocarbons, carbon monoxide, and oxides of nitrogen from autombiles. The analysis was conducted by Vector Research, Incorporated, (VRI) For the Environmental Protection Agency (EPA). The analysi...

A Study of volumetric variations of basal nuclei in the normal human brain by magnetic resonance imaging.

PubMed

Elkattan, Amal; Mahdy, Amal; Eltomey, Mohamed; Ismail, Radwa

2017-03-01

Knowledge of the effects of healthy aging on brain structures is necessary to identify abnormal changes due to diseases. Many studies have demonstrated age-related volume changes in the brain using MRI. 60 healthy individuals who had normal MRI aged from 20 years to 80 years were examined and classified into three groups: Group I: 21 persons; nine males and 12 females aging between 20-39 years old. Group II: 22 persons; 11 males and 11 females aging between 40-59 years old. Group III: 17 persons; eight males and nine females aging between 60-80 years old. Volumetric analysis was done to evaluate the effect of age, gender and hemispheric difference in the caudate and putamen by the slicer 4.3.3.1 software using 3D T1-weighted images. Data were analyzed by student's unpaired t test, ANOVA and regression analysis. The volumes of the measured and corrected caudate nuclei and putamen significantly decreased with aging in males. There was a statistically insignificant relation between the age and the volume of the measured caudate nuclei and putamen in females but there was a statistically significant relation between the age and the corrected caudate nuclei and putamen. There was no significant difference on the caudate and putamen volumes between males and females. There was no significant difference between the right and left caudate nuclei volumes. There was a leftward asymmetry in the putamen volumes. The results can be considered as a base to track individual changes with time (aging and CNS diseases). Clin. Anat. 30:175-182, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

The power-proportion method for intracranial volume correction in volumetric imaging analysis.

PubMed

Liu, Dawei; Johnson, Hans J; Long, Jeffrey D; Magnotta, Vincent A; Paulsen, Jane S

2014-01-01

In volumetric brain imaging analysis, volumes of brain structures are typically assumed to be proportional or linearly related to intracranial volume (ICV). However, evidence abounds that many brain structures have power law relationships with ICV. To take this relationship into account in volumetric imaging analysis, we propose a power law based method-the power-proportion method-for ICV correction. The performance of the new method is demonstrated using data from the PREDICT-HD study.

Lighting design for globally illuminated volume rendering.

PubMed

Zhang, Yubo; Ma, Kwan-Liu

2013-12-01

With the evolution of graphics hardware, high quality global illumination becomes available for real-time volume rendering. Compared to local illumination, global illumination can produce realistic shading effects which are closer to real world scenes, and has proven useful for enhancing volume data visualization to enable better depth and shape perception. However, setting up optimal lighting could be a nontrivial task for average users. There were lighting design works for volume visualization but they did not consider global light transportation. In this paper, we present a lighting design method for volume visualization employing global illumination. The resulting system takes into account view and transfer-function dependent content of the volume data to automatically generate an optimized three-point lighting environment. Our method fully exploits the back light which is not used by previous volume visualization systems. By also including global shadow and multiple scattering, our lighting system can effectively enhance the depth and shape perception of volumetric features of interest. In addition, we propose an automatic tone mapping operator which recovers visual details from overexposed areas while maintaining sufficient contrast in the dark areas. We show that our method is effective for visualizing volume datasets with complex structures. The structural information is more clearly and correctly presented under the automatically generated light sources.

Moduli thermalization and finite temperature effects in "big" divisor large volume D3/ D7 Swiss-cheese compactification

NASA Astrophysics Data System (ADS)

Shukla, Pramod

2011-01-01

In the context of Type IIB compactified on a large volume Swiss-Cheese orientifold in the presence of a mobile space-time filling D3-brane and stacks of fluxed D7-branes wrapping the "big" divisor Σ B of a Swiss-Cheese Calabi Yau in WCP 4[1, 1, 1, 6, 9], we explore various implications of moduli dynamics and discuss their couplings and decay into MSSM (-like) matter fields early in the history of universe to reach thermal equilibrium. Like finite temperature effects in O'KKLT, we observe that the local minimum of zero-temperature effective scalar potential is stable against any finite temperature corrections (up to two-loops) in large volume scenarios as well. Also we find that moduli are heavy enough to avoid any cosmological moduli problem.

SU-E-I-79: Source Geometry Dependence of Gamma Well-Counter Measurements

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

Park, M; Belanger, A; Kijewski, M

Purpose: To determine the effect of liquid sample volume and geometry on counting efficiency in a gamma well-counter, and to assess the relative contributions of sample geometry and self-attenuation. Gamma wellcounters are standard equipment in clinical and preclinical studies, for measuring patient blood radioactivity and quantifying animal tissue uptake for tracer development and other purposes. Accurate measurements are crucial. Methods: Count rates were measured for aqueous solutions of 99m- Tc at four liquid volume values in a 1-cm-diam tube and at six volume values in a 2.2-cm-diam vial. Total activity was constant for all volumes, and data were corrected formore » decay. Count rates from a point source in air, supported by a filter paper, were measured at seven heights between 1.3 and 5.7 cm from the bottom of a tube. Results: Sample volume effects were larger for the tube than for the vial. For the tube, count efficiency relative to a 1-cc volume ranged from 1.05 at 0.05 cc to 0.84 at 3 cc. For the vial, relative count efficiency ranged from 1.02 at 0.05 cc to 0.87 at 15 cc. For the point source, count efficiency relative to 1.3 cm from the tube bottom ranged from 0.98 at 1.8 cm to 0.34 at 5.7 cm. The relative efficiency of a 3-cc liquid sample in a tube compared to a 1-cc sample is 0.84; the average relative efficiency for the solid sample in air between heights in the tube corresponding to the surfaces of those volumes (1.3 and 4.8 cm) is 0.81, implying that the major contribution to efficiency loss is geometry, rather than attenuation. Conclusion: Volume-dependent correction factors should be used for accurate quantitation radioactive of liquid samples. Solid samples should be positioned at the bottom of the tube for maximum count efficiency.« less

Breast density quantification using magnetic resonance imaging (MRI) with bias field correction: A postmortem study

PubMed Central

Ding, Huanjun; Johnson, Travis; Lin, Muqing; Le, Huy Q.; Ducote, Justin L.; Su, Min-Ying; Molloi, Sabee

2013-01-01

Purpose: Quantification of breast density based on three-dimensional breast MRI may provide useful information for the early detection of breast cancer. However, the field inhomogeneity can severely challenge the computerized image segmentation process. In this work, the effect of the bias field in breast density quantification has been investigated with a postmortem study. Methods: T1-weighted images of 20 pairs of postmortem breasts were acquired on a 1.5 T breast MRI scanner. Two computer-assisted algorithms were used to quantify the volumetric breast density. First, standard fuzzy c-means (FCM) clustering was used on raw images with the bias field present. Then, the coherent local intensity clustering (CLIC) method estimated and corrected the bias field during the iterative tissue segmentation process. Finally, FCM clustering was performed on the bias-field-corrected images produced by CLIC method. The left–right correlation for breasts in the same pair was studied for both segmentation algorithms to evaluate the precision of the tissue classification. Finally, the breast densities measured with the three methods were compared to the gold standard tissue compositions obtained from chemical analysis. The linear correlation coefficient, Pearson's r, was used to evaluate the two image segmentation algorithms and the effect of bias field. Results: The CLIC method successfully corrected the intensity inhomogeneity induced by the bias field. In left–right comparisons, the CLIC method significantly improved the slope and the correlation coefficient of the linear fitting for the glandular volume estimation. The left–right breast density correlation was also increased from 0.93 to 0.98. When compared with the percent fibroglandular volume (%FGV) from chemical analysis, results after bias field correction from both the CLIC the FCM algorithms showed improved linear correlation. As a result, the Pearson's r increased from 0.86 to 0.92 with the bias field correction. Conclusions: The investigated CLIC method significantly increased the precision and accuracy of breast density quantification using breast MRI images by effectively correcting the bias field. It is expected that a fully automated computerized algorithm for breast density quantification may have great potential in clinical MRI applications. PMID:24320536

Breast density quantification using magnetic resonance imaging (MRI) with bias field correction: a postmortem study.

PubMed

Ding, Huanjun; Johnson, Travis; Lin, Muqing; Le, Huy Q; Ducote, Justin L; Su, Min-Ying; Molloi, Sabee

2013-12-01

Quantification of breast density based on three-dimensional breast MRI may provide useful information for the early detection of breast cancer. However, the field inhomogeneity can severely challenge the computerized image segmentation process. In this work, the effect of the bias field in breast density quantification has been investigated with a postmortem study. T1-weighted images of 20 pairs of postmortem breasts were acquired on a 1.5 T breast MRI scanner. Two computer-assisted algorithms were used to quantify the volumetric breast density. First, standard fuzzy c-means (FCM) clustering was used on raw images with the bias field present. Then, the coherent local intensity clustering (CLIC) method estimated and corrected the bias field during the iterative tissue segmentation process. Finally, FCM clustering was performed on the bias-field-corrected images produced by CLIC method. The left-right correlation for breasts in the same pair was studied for both segmentation algorithms to evaluate the precision of the tissue classification. Finally, the breast densities measured with the three methods were compared to the gold standard tissue compositions obtained from chemical analysis. The linear correlation coefficient, Pearson's r, was used to evaluate the two image segmentation algorithms and the effect of bias field. The CLIC method successfully corrected the intensity inhomogeneity induced by the bias field. In left-right comparisons, the CLIC method significantly improved the slope and the correlation coefficient of the linear fitting for the glandular volume estimation. The left-right breast density correlation was also increased from 0.93 to 0.98. When compared with the percent fibroglandular volume (%FGV) from chemical analysis, results after bias field correction from both the CLIC the FCM algorithms showed improved linear correlation. As a result, the Pearson's r increased from 0.86 to 0.92 with the bias field correction. The investigated CLIC method significantly increased the precision and accuracy of breast density quantification using breast MRI images by effectively correcting the bias field. It is expected that a fully automated computerized algorithm for breast density quantification may have great potential in clinical MRI applications.

Advances in Surgical Care: Management of Severe Burn Injury

DTIC Science & Technology

2008-01-01

worsen hypocalcemia , es- pecially when hypovolemia is corrected. Neither mannitol nor sodium bicarbon- ate has been shown more effective than volume...umented. Circumferential burn wounds involving the extremities are prone to the tourniquet effect of the inelastic burn es- char. This is further...in a clean environment using electrocautery to ensure hemosta- sis. A vascular examination is repeated after the procedure to verify effectiveness of

Intercomparison of methods for coincidence summing corrections in gamma-ray spectrometry--part II (volume sources).

PubMed

Lépy, M-C; Altzitzoglou, T; Anagnostakis, M J; Capogni, M; Ceccatelli, A; De Felice, P; Djurasevic, M; Dryak, P; Fazio, A; Ferreux, L; Giampaoli, A; Han, J B; Hurtado, S; Kandic, A; Kanisch, G; Karfopoulos, K L; Klemola, S; Kovar, P; Laubenstein, M; Lee, J H; Lee, J M; Lee, K B; Pierre, S; Carvalhal, G; Sima, O; Tao, Chau Van; Thanh, Tran Thien; Vidmar, T; Vukanac, I; Yang, M J

2012-09-01

The second part of an intercomparison of the coincidence summing correction methods is presented. This exercise concerned three volume sources, filled with liquid radioactive solution. The same experimental spectra, decay scheme and photon emission intensities were used by all the participants. The results were expressed as coincidence summing corrective factors for several energies of (152)Eu and (134)Cs, and different source-to-detector distances. They are presented and discussed. Copyright © 2012 Elsevier Ltd. All rights reserved.

A novel forward projection-based metal artifact reduction method for flat-detector computed tomography.

PubMed

Prell, Daniel; Kyriakou, Yiannis; Beister, Marcel; Kalender, Willi A

2009-11-07

Metallic implants generate streak-like artifacts in flat-detector computed tomography (FD-CT) reconstructed volumetric images. This study presents a novel method for reducing these disturbing artifacts by inserting discarded information into the original rawdata using a three-step correction procedure and working directly with each detector element. Computation times are minimized by completely implementing the correction process on graphics processing units (GPUs). First, the original volume is corrected using a three-dimensional interpolation scheme in the rawdata domain, followed by a second reconstruction. This metal artifact-reduced volume is then segmented into three materials, i.e. air, soft-tissue and bone, using a threshold-based algorithm. Subsequently, a forward projection of the obtained tissue-class model substitutes the missing or corrupted attenuation values directly for each flat detector element that contains attenuation values corresponding to metal parts, followed by a final reconstruction. Experiments using tissue-equivalent phantoms showed a significant reduction of metal artifacts (deviations of CT values after correction compared to measurements without metallic inserts reduced typically to below 20 HU, differences in image noise to below 5 HU) caused by the implants and no significant resolution losses even in areas close to the inserts. To cover a variety of different cases, cadaver measurements and clinical images in the knee, head and spine region were used to investigate the effectiveness and applicability of our method. A comparison to a three-dimensional interpolation correction showed that the new approach outperformed interpolation schemes. Correction times are minimized, and initial and corrected images are made available at almost the same time (12.7 s for the initial reconstruction, 46.2 s for the final corrected image compared to 114.1 s and 355.1 s on central processing units (CPUs)).

Fast Computation of Solvation Free Energies with Molecular Density Functional Theory: Thermodynamic-Ensemble Partial Molar Volume Corrections.

PubMed

Sergiievskyi, Volodymyr P; Jeanmairet, Guillaume; Levesque, Maximilien; Borgis, Daniel

2014-06-05

Molecular density functional theory (MDFT) offers an efficient implicit-solvent method to estimate molecule solvation free-energies, whereas conserving a fully molecular representation of the solvent. Even within a second-order approximation for the free-energy functional, the so-called homogeneous reference fluid approximation, we show that the hydration free-energies computed for a data set of 500 organic compounds are of similar quality as those obtained from molecular dynamics free-energy perturbation simulations, with a computer cost reduced by 2-3 orders of magnitude. This requires to introduce the proper partial volume correction to transform the results from the grand canonical to the isobaric-isotherm ensemble that is pertinent to experiments. We show that this correction can be extended to 3D-RISM calculations, giving a sound theoretical justification to empirical partial molar volume corrections that have been proposed recently.

Evaluation of the effects of insufficient blood volume samples on the performance of blood glucose self-test meters.

PubMed

Pfützner, Andreas; Schipper, Christina; Ramljak, Sanja; Flacke, Frank; Sieber, Jochen; Forst, Thomas; Musholt, Petra B

2013-11-01

Accuracy of blood glucose readings is (among other things) dependent on the test strip being completely filled with sufficient sample volume. The devices are supposed to display an error message in case of incomplete filling. This laboratory study was performed to test the performance of 31 commercially available devices in case of incomplete strip filling. Samples with two different glucose levels (60-90 and 300-350 mg/dl) were used to generate three different sample volumes: 0.20 µl (too low volume for any device), 0.32 µl (borderline volume), and 1.20 µl (low but supposedly sufficient volume for all devices). After a point-of-care capillary reference measurement (StatStrip, NovaBiomedical), the meter strip was filled (6x) with the respective volume, and the response of the meters (two devices) was documented (72 determinations/meter type). Correct response was defined as either an error message indicating incomplete filling or a correct reading (±20% compared with reference reading). Only five meters showed 100% correct responses [BGStar and iBGStar (both Sanofi), ACCU-CHEK Compact+ and ACCU-CHEK Mobile (both Roche Diagnostics), OneTouch Verio (LifeScan)]. The majority of the meters (17) had up to 10% incorrect reactions [predominantly incorrect readings with sufficient volume; Precision Xceed and Xtra, FreeStyle Lite, and Freedom Lite (all Abbott); GlucoCard+ and GlucoMen GM (both Menarini); Contour, Contour USB, and Breeze2 (all Bayer); OneTouch Ultra Easy, Ultra 2, and Ultra Smart (all LifeScan); Wellion Dialog and Premium (both MedTrust); FineTouch (Terumo); ACCU-CHEK Aviva (Roche); and GlucoTalk (Axis-Shield)]. Ten percent to 20% incorrect reactions were seen with OneTouch Vita (LifeScan), ACCU-CHEK Aviva Nano (Roche), OmniTest+ (BBraun), and AlphaChek+ (Berger Med). More than 20% incorrect reactions were obtained with Pura (Ypsomed), GlucoCard Meter and GlucoMen LX (both Menarini), Elite (Bayer), and MediTouch (Medisana). In summary, partial and incomplete blood filling of glucose meter strips is often associated with inaccurate reading. These findings underline the importance of appropriate patient education on this aspect of blood glucose self-monitoring. © 2013 Diabetes Technology Society.

Investigation of thermal and temporal responses of ionization chambers in radiation dosimetry.

PubMed

AlMasri, Hussein; Funyu, Akira; Kakinohana, Yasumasa; Murayama, Sadayuki

2012-07-01

The ionization chamber is a primary dosimeter that is used in radiation dosimetry. Generally, the ion chamber response requires temperature/pressure correction according to the ideal gas law. However, this correction does not consider the thermal volume effect of chambers. The temporal and thermal volume effects of various chambers (CC01, CC13, NACP parallel-plate, PTW) with different wall and electrode materials have been studied in a water phantom. Measurements were done after heating the water with a suitable heating system, and chambers were submerged for a sufficient time to allow for temperature equilibrium. Temporal results show that all chambers equilibrate quickly in water. The equilibration time was between 3 and 5 min for all chambers. Thermal results show that all chambers expanded in response to heating except for the PTW, which contracted. This might be explained by the differences in the volumes of all chambers and also by the difference in wall material composition of PTW from the other chambers. It was found that the smallest chamber, CC01, showed the greatest expansion. The magnitude of the expansion was ~1, 0.8, and 0.9% for CC01, CC13, and parallel-plate chambers, respectively, in the temperature range of 295-320 K. The magnitude of the detected contraction was <0.3% for PTW in the same temperature range. For absolute dosimetry, it is necessary to make corrections for the ion chamber response, especially for small ion chambers like the CC01. Otherwise, room and water phantom temperatures should remain within a close range.

Experimental aspects of buoyancy correction in measuring reliable high-pressure excess adsorption isotherms using the gravimetric method

NASA Astrophysics Data System (ADS)

Nguyen, Huong Giang T.; Horn, Jarod C.; Thommes, Matthias; van Zee, Roger D.; Espinal, Laura

2017-12-01

Addressing reproducibility issues in adsorption measurements is critical to accelerating the path to discovery of new industrial adsorbents and to understanding adsorption processes. A National Institute of Standards and Technology Reference Material, RM 8852 (ammonium ZSM-5 zeolite), and two gravimetric instruments with asymmetric two-beam balances were used to measure high-pressure adsorption isotherms. This work demonstrates how common approaches to buoyancy correction, a key factor in obtaining the mass change due to surface excess gas uptake from the apparent mass change, can impact the adsorption isotherm data. Three different approaches to buoyancy correction were investigated and applied to the subcritical CO2 and supercritical N2 adsorption isotherms at 293 K. It was observed that measuring a collective volume for all balance components for the buoyancy correction (helium method) introduces an inherent bias in temperature partition when there is a temperature gradient (i.e. analysis temperature is not equal to instrument air bath temperature). We demonstrate that a blank subtraction is effective in mitigating the biases associated with temperature partitioning, instrument calibration, and the determined volumes of the balance components. In general, the manual and subtraction methods allow for better treatment of the temperature gradient during buoyancy correction. From the study, best practices specific to asymmetric two-beam balances and more general recommendations for measuring isotherms far from critical temperatures using gravimetric instruments are offered.

Experimental aspects of buoyancy correction in measuring reliable highpressure excess adsorption isotherms using the gravimetric method.

PubMed

Nguyen, Huong Giang T; Horn, Jarod C; Thommes, Matthias; van Zee, Roger D; Espinal, Laura

2017-12-01

Addressing reproducibility issues in adsorption measurements is critical to accelerating the path to discovery of new industrial adsorbents and to understanding adsorption processes. A National Institute of Standards and Technology Reference Material, RM 8852 (ammonium ZSM-5 zeolite), and two gravimetric instruments with asymmetric two-beam balances were used to measure high-pressure adsorption isotherms. This work demonstrates how common approaches to buoyancy correction, a key factor in obtaining the mass change due to surface excess gas uptake from the apparent mass change, can impact the adsorption isotherm data. Three different approaches to buoyancy correction were investigated and applied to the subcritical CO 2 and supercritical N 2 adsorption isotherms at 293 K. It was observed that measuring a collective volume for all balance components for the buoyancy correction (helium method) introduces an inherent bias in temperature partition when there is a temperature gradient (i.e. analysis temperature is not equal to instrument air bath temperature). We demonstrate that a blank subtraction is effective in mitigating the biases associated with temperature partitioning, instrument calibration, and the determined volumes of the balance components. In general, the manual and subtraction methods allow for better treatment of the temperature gradient during buoyancy correction. From the study, best practices specific to asymmetric two-beam balances and more general recommendations for measuring isotherms far from critical temperatures using gravimetric instruments are offered.

40 CFR 1065.695 - Data requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... restriction. (v) Charge air cooler volume. (vi) Charge air cooler outlet temperature, specified engine... following: (i) Drift correction. (ii) Noise correction. (iii) “Dry-to-wet” correction. (iv) NMHC, CH4, and...

40 CFR 1065.695 - Data requirements.

Code of Federal Regulations, 2013 CFR

2013-07-01

... restriction. (v) Charge air cooler volume. (vi) Charge air cooler outlet temperature, specified engine... following: (i) Drift correction. (ii) Noise correction. (iii) “Dry-to-wet” correction. (iv) NMHC, CH4, and...

40 CFR 1065.695 - Data requirements.

Code of Federal Regulations, 2012 CFR

2012-07-01

... restriction. (v) Charge air cooler volume. (vi) Charge air cooler outlet temperature, specified engine... following: (i) Drift correction. (ii) Noise correction. (iii) “Dry-to-wet” correction. (iv) NMHC, CH4, and...

Adolescent idiopathic scoliosis: risk factors for complications and the effect of hospital volume on outcomes.

PubMed

Menger, Richard P; Kalakoti, Piyush; Pugely, Andrew J; Nanda, Anil; Sin, Anthony

2017-10-01

OBJECTIVE Adolescent idiopathic scoliosis (AIS) is the most common form of scoliosis. Limited literature exists defining risk factors associated with outcomes during initial hospitalization in these patients. In this study, the authors investigated patient demographics, clinical and hospital characteristics impacting short-term outcomes, and costs in adolescent patients undergoing surgical deformity correction for idiopathic scoliosis. Additionally, the authors elucidate the impact of hospital surgical volume on outcomes for these patients. METHODS Using the National Inpatient Sample database and appropriate International Classification of Diseases, 9th Revision codes, the authors identified adolescent patients (10-19 years of age) undergoing surgical deformity correction for idiopathic scoliosis during 2001-2014. For national estimates, appropriate weights provided by the Agency of Healthcare Research and Quality were used. Multivariable regression techniques were employed to assess the association of risk factors with discharge disposition, postsurgical neurological complications, length of hospital stay, and hospitalization costs. RESULTS Overall, 75,106 adolescent patients underwent surgical deformity correction. The rates of postsurgical complications were estimated at 0.9% for neurological issues, 2.8% for respiratory complications, 0.8% for cardiac complications, 0.4% for infections, 2.7% for gastrointestinal complications, 0.1% for venous thromboembolic events, and 0.1% for acute renal failure. Overall, patients stayed at the hospital for an average of 5.72 days (median 5 days) and on average incurred hospitalization costs estimated at $54,997 (median $47,909). As compared with patients at low-volume centers (≤ 50 operations/year), those undergoing surgical deformity correction at high-volume centers (> 50/year) had a significantly lower likelihood of an unfavorable discharge (discharge to rehabilitation) (OR 1.16, 95% CI 1.03-1.30, p = 0.016) and incurred lower costs (mean $33,462 vs $56,436, p < 0.001) but had a longer duration of stay (mean 6 vs 5.65 days, p = 0.002). In terms of neurological complications, no significant differences in the odds ratios were noted between high- and low-volume centers (OR 1.23, 95% CI 0.97-1.55, p = 0.091). CONCLUSIONS This study provides insight into the clinical characteristics of AIS patients and their postoperative outcomes following deformity correction as they relate to hospital volume. It provides information regarding independent risk factors for unfavorable discharge and neurological complications following surgery for AIS. The proposed estimates could be used as an adjunct to clinical judgment in presurgical planning, risk stratification, and cost containment.

Monitoring of intracranial compliance: correction for a change in body position.

PubMed

Raabe, A; Czosnyka, M; Piper, I; Seifert, V

1999-01-01

The objectives of our study were 1. to investigate whether the intracranial compliance changes with body position; 2. to test if the pressure-volume index (PVI) calculation is affected by different body positions; 3. to define the optimal parameter to correct PVI for changes in body position and 4. to investigate the physiological meaning of the constant term (P0) in the model of the intracranial volume-pressure relationship. Thirteen patients were included in this study. All patients were subjected to 2 to 3 different body positions. In each position, either classic bolus injection was performed for measurement of intracranial compliance and calculation of PVI or the new Spiegelberg compliance monitor was used to calculate PVI continuously. Four different models were used for calculating the constant pressure term P0 and the P0 corrected PVI values. Pressure volume index not corrected for the constant term P0 significantly decreased with elevating the patients head (r = 0.70, p < 0.0001). In contrast, volume-pressure response and ICP pulse amplitude did not change with position. Using the constant term P0 to correct the PVI we found no changes between the different body positions. Our results suggest that during the variation in body position there is no change in intracranial compliance but a change in hydrostatic offset pressure which causes a shifting of the volume-pressure curve along the pressure axis without its shape being affected. PVI measurements should either be performed only with the patient in the 0 degree recumbent position or that the PVI calculation should be corrected for the hydrostatic difference between the level of the ICP transducer and the hydrostatic indifference point of the craniospinal system close to the third thoracic vertebra.

Analysis of excimer laser radiant exposure effect toward corneal ablation volume at LASIK procedure

NASA Astrophysics Data System (ADS)

Adiati, Rima Fitria; Rini Rizki, Artha Bona; Kusumawardhani, Apriani; Setijono, Heru; Rahmadiansah, Andi

2016-11-01

LASIK (Laser Asissted In Situ Interlamelar Keratomilieusis) is a technique for correcting refractive disorders of the eye such as myopia and astigmatism using an excimer laser. This procedure use photoablation technique to decompose corneal tissues. Although preferred due to its efficiency, permanency, and accuracy, the inappropriate amount radiant exposure often cause side effects like under-over correction, irregular astigmatism and problems on surrounding tissues. In this study, the radiant exposure effect toward corneal ablation volume has been modelled through several processes. Data collecting results is laser data specifications with 193 nm wavelength, beam diameter of 0.065 - 0.65 cm, and fluence of 160 mJ/cm2. For the medical data, the myopia-astigmatism value, cornea size, corneal ablation thickness, and flap data are taken. The first modelling step is determining the laser diameter between 0.065 - 0.65 cm with 0.45 cm increment. The energy, power, and intensity of laser determined from laser beam area. Number of pulse and total energy is calculated before the radiant exposure of laser is obtained. Next is to determine the parameters influence the ablation volume. Regression method used to create the equation, and then the spot size is substituted to the model. The validation used is statistic correlation method to both experimental data and theory. By the model created, it is expected that any potential complications can be prevented during LASIK procedures. The recommendations can give the users clearer picture to determine the appropriate amount of radiant exposure with the corneal ablation volume necessary.

Towards an explicit model of large field inflation

NASA Astrophysics Data System (ADS)

Dorronsoro, Juan Diaz; Schillo, Marjorie

2018-05-01

The unwinding inflation mechanism is studied in a type IIB flux compactification where all moduli are stabilized using flux, non-perturbative effects, and the leading α' corrections of the large volume scenario. We consider the backreaction on the geometry due to the presence of anti-D3 branes as well as the backreaction of inflation on the Kähler moduli, and compute the resulting corrections to the slow-roll potential. By taking large flux numbers, we are able to find inflationary epochs where backreaction effects are under control, the inflaton traverses a super-Planckian field range, and the resulting amplitude of scalar perturbations is consistent with observation.

Optimization of yttrium-90 PET for simultaneous PET/MR imaging: A phantom study

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

Eldib, Mootaz

2016-08-15

Purpose: Positron emission tomography (PET) imaging of yttrium-90 in the liver post radioembolization has been shown useful for personalized dosimetry calculations and evaluation of extrahepatic deposition. The purpose of this study was to quantify the benefits of several MR-based data correction approaches offered by using a combined PET/MR system to improve Y-90 PET imaging. In particular, the feasibility of motion and partial volume corrections were investigated in a controlled phantom study. Methods: The ACR phantom was filled with an initial concentration of 8 GBq of Y-90 solution resulting in a contrast of 10:1 between the hot cylinders and the background.more » Y-90 PET motion correction through motion estimates from MR navigators was evaluated by using a custom-built motion stage that simulated realistic amplitudes of respiration-induced liver motion. Finally, the feasibility of an MR-based partial volume correction method was evaluated using a wavelet decomposition approach. Results: Motion resulted in a large (∼40%) loss of contrast recovery for the 8 mm cylinder in the phantom, but was corrected for after MR-based motion correction was applied. Partial volume correction improved contrast recovery by 13% for the 8 mm cylinder. Conclusions: MR-based data correction improves Y-90 PET imaging on simultaneous PET/MR systems. Assessment of these methods must be studied further in the clinical setting.« less

Glucose hypometabolism is highly localized, but lower cortical thickness and brain atrophy are widespread in cognitively normal older adults.

PubMed

Nugent, Scott; Castellano, Christian-Alexandre; Goffaux, Philippe; Whittingstall, Kevin; Lepage, Martin; Paquet, Nancy; Bocti, Christian; Fulop, Tamas; Cunnane, Stephen C

2014-06-01

Several studies have suggested that glucose hypometabolism may be present in specific brain regions in cognitively normal older adults and could contribute to the risk of subsequent cognitive decline. However, certain methodological shortcomings, including a lack of partial volume effect (PVE) correction or insufficient cognitive testing, confound the interpretation of most studies on this topic. We combined [(18)F]fluorodeoxyglucose ([(18)F]FDG) positron emission tomography (PET) and magnetic resonance (MR) imaging to quantify cerebral metabolic rate of glucose (CMRg) as well as cortical volume and thickness in 43 anatomically defined brain regions from a group of cognitively normal younger (25 ± 3 yr old; n = 25) and older adults (71 ± 9 yr old; n = 31). After correcting for PVE, we observed 11-17% lower CMRg in three specific brain regions of the older group: the superior frontal cortex, the caudal middle frontal cortex, and the caudate (P ≤ 0.01 false discovery rate-corrected). In the older group, cortical volumes and cortical thickness were 13-33 and 7-18% lower, respectively, in multiple brain regions (P ≤ 0.01 FDR correction). There were no differences in CMRg between individuals who were or were not prescribed antihypertensive medication. There were no significant correlations between CMRg and cognitive performance or metabolic parameters measured in fasting plasma. We conclude that highly localized glucose hypometabolism and widespread cortical thinning and atrophy can be present in older adults who are cognitively normal, as assessed using age-normed neuropsychological testing measures. Copyright © 2014 the American Physiological Society.

Respiratory effort correction strategies to improve the reproducibility of lung expansion measurements

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

Du, Kaifang; Reinhardt, Joseph M.; Christensen, Gary E.

2013-12-15

Purpose: Four-dimensional computed tomography (4DCT) can be used to make measurements of pulmonary function longitudinally. The sensitivity of such measurements to identify change depends on measurement uncertainty. Previously, intrasubject reproducibility of Jacobian-based measures of lung tissue expansion was studied in two repeat prior-RT 4DCT human acquisitions. Difference in respiratory effort such as breathing amplitude and frequency may affect longitudinal function assessment. In this study, the authors present normalization schemes that correct ventilation images for variations in respiratory effort and assess the reproducibility improvement after effort correction.Methods: Repeat 4DCT image data acquired within a short time interval from 24 patients priormore » to radiation therapy (RT) were used for this analysis. Using a tissue volume preserving deformable image registration algorithm, Jacobian ventilation maps in two scanning sessions were computed and compared on the same coordinate for reproducibility analysis. In addition to computing the ventilation maps from end expiration to end inspiration, the authors investigated the effort normalization strategies using other intermediated inspiration phases upon the principles of equivalent tidal volume (ETV) and equivalent lung volume (ELV). Scatter plots and mean square error of the repeat ventilation maps and the Jacobian ratio map were generated for four conditions: no effort correction, global normalization, ETV, and ELV. In addition, gamma pass rate was calculated from a modified gamma index evaluation between two ventilation maps, using acceptance criterions of 2 mm distance-to-agreement and 5% ventilation difference.Results: The pattern of regional pulmonary ventilation changes as lung volume changes. All effort correction strategies improved reproducibility when changes in respiratory effort were greater than 150 cc (p < 0.005 with regard to the gamma pass rate). Improvement of reproducibility was correlated with respiratory effort difference (R = 0.744 for ELV in the cohort with tidal volume difference greater than 100 cc). In general for all subjects, global normalization, ETV and ELV significantly improved reproducibility compared to no effort correction (p = 0.009, 0.002, 0.005 respectively). When tidal volume difference was small (less than 100 cc), none of the three effort correction strategies improved reproducibility significantly (p = 0.52, 0.46, 0.46 respectively). For the cohort (N = 13) with tidal volume difference greater than 100 cc, the average gamma pass rate improves from 57.3% before correction to 66.3% after global normalization, and 76.3% after ELV. ELV was found to be significantly better than global normalization (p = 0.04 for all subjects, and p = 0.003 for the cohort with tidal volume difference greater than 100 cc).Conclusions: All effort correction strategies improve the reproducibility of the authors' pulmonary ventilation measures, and the improvement of reproducibility is highly correlated with the changes in respiratory effort. ELV gives better results as effort difference increase, followed by ETV, then global. However, based on the spatial and temporal heterogeneity in the lung expansion rate, a single scaling factor (e.g., global normalization) appears to be less accurate to correct the ventilation map when changes in respiratory effort are large.« less

Pulmonary function tests correlated with thoracic volumes in adolescent idiopathic scoliosis.

PubMed

Ledonio, Charles Gerald T; Rosenstein, Benjamin E; Johnston, Charles E; Regelmann, Warren E; Nuckley, David J; Polly, David W

2017-01-01

Scoliosis deformity has been linked with deleterious changes in the thoracic cavity that affect pulmonary function. The causal relationship between spinal deformity and pulmonary function has yet to be fully defined. It has been hypothesized that deformity correction improves pulmonary function by restoring both respiratory muscle efficiency and increasing the space available to the lungs. This research aims to correlate pulmonary function and thoracic volume before and after scoliosis correction. Retrospective correlational analysis between thoracic volume modeling from plain x-rays and pulmonary function tests was conducted. Adolescent idiopathic scoliosis patients enrolled in a multicenter database were sorted by pre-operative Total Lung Capacities (TLC) % predicted values from their Pulmonary Function Tests (PFT). Ten patients with the best and ten patients with the worst TLC values were included. Modeled thoracic volume and TLC values were compared before and 2 years after surgery. Scoliosis correction resulted in an increase in the thoracic volume for patients with the worst initial TLCs (11.7%) and those with the best initial TLCs (12.5%). The adolescents with the most severe pulmonary restriction prior to surgery strongly correlated with post-operative change in total lung capacity and thoracic volume (r 2  = 0.839; p < 0.001). The mean increase in thoracic volume in this group was 373.1 cm 3 (11.7%) which correlated with a 21.2% improvement in TLC. Scoliosis correction in adolescents was found to increase thoracic volume and is strongly correlated with improved TLC in cases with severe restrictive pulmonary function, but no correlation was found in cases with normal pulmonary function. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:175-182, 2017. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Loop quantum corrected Einstein Yang-Mills black holes

NASA Astrophysics Data System (ADS)

Protter, Mason; DeBenedictis, Andrew

2018-05-01

In this paper, we study the homogeneous interiors of black holes possessing SU(2) Yang-Mills fields subject to corrections inspired by loop quantum gravity. The systems studied possess both magnetic and induced electric Yang-Mills fields. We consider the system of equations both with and without Wilson loop corrections to the Yang-Mills potential. The structure of the Yang-Mills Hamiltonian, along with the restriction to homogeneity, allows for an anomaly-free effective quantization. In particular, we study the bounce which replaces the classical singularity and the behavior of the Yang-Mills fields in the quantum corrected interior, which possesses topology R ×S2 . Beyond the bounce, the magnitude of the Yang-Mills electric field asymptotically grows monotonically. This results in an ever-expanding R sector even though the two-sphere volume is asymptotically constant. The results are similar with and without Wilson loop corrections on the Yang-Mills potential.

Combining MRI With PET for Partial Volume Correction Improves Image-Derived Input Functions in Mice

NASA Astrophysics Data System (ADS)

Evans, Eleanor; Buonincontri, Guido; Izquierdo, David; Methner, Carmen; Hawkes, Rob C.; Ansorge, Richard E.; Krieg, Thomas; Carpenter, T. Adrian; Sawiak, Stephen J.

2015-06-01

Accurate kinetic modelling using dynamic PET requires knowledge of the tracer concentration in plasma, known as the arterial input function (AIF). AIFs are usually determined by invasive blood sampling, but this is prohibitive in murine studies due to low total blood volumes. As a result of the low spatial resolution of PET, image-derived input functions (IDIFs) must be extracted from left ventricular blood pool (LVBP) ROIs of the mouse heart. This is challenging because of partial volume and spillover effects between the LVBP and myocardium, contaminating IDIFs with tissue signal. We have applied the geometric transfer matrix (GTM) method of partial volume correction (PVC) to 12 mice injected with 18F - FDG affected by a Myocardial Infarction (MI), of which 6 were treated with a drug which reduced infarction size [1]. We utilised high resolution MRI to assist in segmenting mouse hearts into 5 classes: LVBP, infarcted myocardium, healthy myocardium, lungs/body and background. The signal contribution from these 5 classes was convolved with the point spread function (PSF) of the Cambridge split magnet PET scanner and a non-linear fit was performed on the 5 measured signal components. The corrected IDIF was taken as the fitted LVBP component. It was found that the GTM PVC method could recover an IDIF with less contamination from spillover than an IDIF extracted from PET data alone. More realistic values of Ki were achieved using GTM IDIFs, which were shown to be significantly different (p <; 0.05) between the treated and untreated groups.

Real-Time Correction By Optical Tracking with Integrated Geometric Distortion Correction for Reducing Motion Artifacts in fMRI

NASA Astrophysics Data System (ADS)

Rotenberg, David J.

Artifacts caused by head motion are a substantial source of error in fMRI that limits its use in neuroscience research and clinical settings. Real-time scan-plane correction by optical tracking has been shown to correct slice misalignment and non-linear spin-history artifacts, however residual artifacts due to dynamic magnetic field non-uniformity may remain in the data. A recently developed correction technique, PLACE, can correct for absolute geometric distortion using the complex image data from two EPI images, with slightly shifted k-space trajectories. We present a correction approach that integrates PLACE into a real-time scan-plane update system by optical tracking, applied to a tissue-equivalent phantom undergoing complex motion and an fMRI finger tapping experiment with overt head motion to induce dynamic field non-uniformity. Experiments suggest that including volume by volume geometric distortion correction by PLACE can suppress dynamic geometric distortion artifacts in a phantom and in vivo and provide more robust activation maps.

Evaluation of a 3D local multiresolution algorithm for the correction of partial volume effects in positron emission tomography.

PubMed

Le Pogam, Adrien; Hatt, Mathieu; Descourt, Patrice; Boussion, Nicolas; Tsoumpas, Charalampos; Turkheimer, Federico E; Prunier-Aesch, Caroline; Baulieu, Jean-Louis; Guilloteau, Denis; Visvikis, Dimitris

2011-09-01

Partial volume effects (PVEs) are consequences of the limited spatial resolution in emission tomography leading to underestimation of uptake in tissues of size similar to the point spread function (PSF) of the scanner as well as activity spillover between adjacent structures. Among PVE correction methodologies, a voxel-wise mutual multiresolution analysis (MMA) was recently introduced. MMA is based on the extraction and transformation of high resolution details from an anatomical image (MR/CT) and their subsequent incorporation into a low-resolution PET image using wavelet decompositions. Although this method allows creating PVE corrected images, it is based on a 2D global correlation model, which may introduce artifacts in regions where no significant correlation exists between anatomical and functional details. A new model was designed to overcome these two issues (2D only and global correlation) using a 3D wavelet decomposition process combined with a local analysis. The algorithm was evaluated on synthetic, simulated and patient images, and its performance was compared to the original approach as well as the geometric transfer matrix (GTM) method. Quantitative performance was similar to the 2D global model and GTM in correlated cases. In cases where mismatches between anatomical and functional information were present, the new model outperformed the 2D global approach, avoiding artifacts and significantly improving quality of the corrected images and their quantitative accuracy. A new 3D local model was proposed for a voxel-wise PVE correction based on the original mutual multiresolution analysis approach. Its evaluation demonstrated an improved and more robust qualitative and quantitative accuracy compared to the original MMA methodology, particularly in the absence of full correlation between anatomical and functional information.

Evaluation of a 3D local multiresolution algorithm for the correction of partial volume effects in positron emission tomography

PubMed Central

Le Pogam, Adrien; Hatt, Mathieu; Descourt, Patrice; Boussion, Nicolas; Tsoumpas, Charalampos; Turkheimer, Federico E.; Prunier-Aesch, Caroline; Baulieu, Jean-Louis; Guilloteau, Denis; Visvikis, Dimitris

2011-01-01

Purpose Partial volume effects (PVE) are consequences of the limited spatial resolution in emission tomography leading to under-estimation of uptake in tissues of size similar to the point spread function (PSF) of the scanner as well as activity spillover between adjacent structures. Among PVE correction methodologies, a voxel-wise mutual multi-resolution analysis (MMA) was recently introduced. MMA is based on the extraction and transformation of high resolution details from an anatomical image (MR/CT) and their subsequent incorporation into a low resolution PET image using wavelet decompositions. Although this method allows creating PVE corrected images, it is based on a 2D global correlation model which may introduce artefacts in regions where no significant correlation exists between anatomical and functional details. Methods A new model was designed to overcome these two issues (2D only and global correlation) using a 3D wavelet decomposition process combined with a local analysis. The algorithm was evaluated on synthetic, simulated and patient images, and its performance was compared to the original approach as well as the geometric transfer matrix (GTM) method. Results Quantitative performance was similar to the 2D global model and GTM in correlated cases. In cases where mismatches between anatomical and functional information were present the new model outperformed the 2D global approach, avoiding artefacts and significantly improving quality of the corrected images and their quantitative accuracy. Conclusions A new 3D local model was proposed for a voxel-wise PVE correction based on the original mutual multi-resolution analysis approach. Its evaluation demonstrated an improved and more robust qualitative and quantitative accuracy compared to the original MMA methodology, particularly in the absence of full correlation between anatomical and functional information. PMID:21978037

A hybrid strategy of offline adaptive planning and online image guidance for prostate cancer radiotherapy.

PubMed

Lei, Yu; Wu, Qiuwen

2010-04-21

Offline adaptive radiotherapy (ART) has been used to effectively correct and compensate for prostate motion and reduce the required margin. The efficacy depends on the characteristics of the patient setup error and interfraction motion through the whole treatment; specifically, systematic errors are corrected and random errors are compensated for through the margins. In online image-guided radiation therapy (IGRT) of prostate cancer, the translational setup error and inter-fractional prostate motion are corrected through pre-treatment imaging and couch correction at each fraction. However, the rotation and deformation of the target are not corrected and only accounted for with margins in treatment planning. The purpose of this study was to investigate whether the offline ART strategy is necessary for an online IGRT protocol and to evaluate the benefit of the hybrid strategy. First, to investigate the rationale of the hybrid strategy, 592 cone-beam-computed tomography (CBCT) images taken before and after each fraction for an online IGRT protocol from 16 patients were analyzed. Specifically, the characteristics of prostate rotation were analyzed. It was found that there exist systematic inter-fractional prostate rotations, and they are patient specific. These rotations, if not corrected, are persistent through the treatment fraction, and rotations detected in early fractions are representative of those in later fractions. These findings suggest that the offline adaptive replanning strategy is beneficial to the online IGRT protocol with further margin reductions. Second, to quantitatively evaluate the benefit of the hybrid strategy, 412 repeated helical CT scans from 25 patients during the course of treatment were included in the replanning study. Both low-risk patients (LRP, clinical target volume, CTV = prostate) and intermediate-risk patients (IRP, CTV = prostate + seminal vesicles) were included in the simulation. The contours of prostate and seminal vesicles were delineated on each CT. The benefit of margin reduction to compensate for both rotation and deformation in the hybrid strategy was evaluated geometrically. With the hybrid strategy, the planning margins can be reduced by 1.4 mm for LRP, and 2.0 mm for IRP, compared with the standard online IGRT only, to maintain the same 99% target volume coverage. The average relative reduction in planning target volume (PTV) based on the internal target volume (ITV) from PTV based on CTV is 19% for LRP, and 27% for IRP.

Correction techniques for depth errors with stereo three-dimensional graphic displays

NASA Technical Reports Server (NTRS)

Parrish, Russell V.; Holden, Anthony; Williams, Steven P.

1992-01-01

Three-dimensional (3-D), 'real-world' pictorial displays that incorporate 'true' depth cues via stereopsis techniques have proved effective for displaying complex information in a natural way to enhance situational awareness and to improve pilot/vehicle performance. In such displays, the display designer must map the depths in the real world to the depths available with the stereo display system. However, empirical data have shown that the human subject does not perceive the information at exactly the depth at which it is mathematically placed. Head movements can also seriously distort the depth information that is embedded in stereo 3-D displays because the transformations used in mapping the visual scene to the depth-viewing volume (DVV) depend intrinsically on the viewer location. The goal of this research was to provide two correction techniques; the first technique corrects the original visual scene to the DVV mapping based on human perception errors, and the second (which is based on head-positioning sensor input data) corrects for errors induced by head movements. Empirical data are presented to validate both correction techniques. A combination of the two correction techniques effectively eliminates the distortions of depth information embedded in stereo 3-D displays.

40 CFR 53.56 - Test for effect of variations in ambient pressure.

Code of Federal Regulations, 2010 CFR

2010-07-01

... measurement accuracy. (iv) Coefficient of variability measurement accuracy. (v) Ambient pressure measurement... through the sample filter, measured in actual volume units at the temperature and pressure of the air as... volumetric flow rate corrections are made based on measurements of actual ambient temperature and pressure...

Macrolane (large particle biphasic hyaluronic acid) filler injection for correction of defect contour after liposuction.

PubMed

Cerqua, Sandro; Angelucci, Francesco

2013-08-01

In a minority of patients undergoing liposuction, superficial irregularities (or skin depression) in the operated area may occur. Macrolane is a gel composed of hyaluronic acid (HA), used for volume restoration of soft tissues. In this study, the authors investigated the effectiveness, maintenance, and safety of Macrolane as a "non-surgical" treatment to correct skin depression after liposuction. Twelve female patients were included. Macrolane was injected at a subdermal superficial plane using an intramuscular or spinal needle. In all patients, Macrolane was successful in correcting skin depression. No relevant side effects were observed. At 8 months post-injection, a persistence of correction of 60-70% was still present in 90% of the patients. In conclusion, Macrolane filler injections are a predictable, safe, and long-lasting non-surgical procedure to fill contour defects that arise after liposuction, and represent a good option for patients who refuse to undergo an additional surgery to fill the arisen skin depressions.

Atypical nucleus accumbens morphology in psychopathy: another limbic piece in the puzzle.

PubMed

Boccardi, Marina; Bocchetta, Martina; Aronen, Hannu J; Repo-Tiihonen, Eila; Vaurio, Olli; Thompson, Paul M; Tiihonen, Jari; Frisoni, Giovanni B

2013-01-01

Psychopathy has been associated with increased putamen and striatum volumes. The nucleus accumbens - a key structure in reversal learning, less effective in psychopathy - has not yet received specific attention. Moreover, basal ganglia morphology has never been explored. We examined the morphology of the caudate, putamen and accumbens, manually segmented from magnetic resonance images of 26 offenders (age: 32.5 ± 8.4) with medium-high psychopathy (mean PCL-R=30 ± 5) and 25 healthy controls (age: 34.6 ± 10.8). Local differences were statistically modeled using a surface-based radial distance mapping method (p<0.05; multiple comparisons correction through permutation tests). In psychopathy, the caudate and putamen had normal global volume, but different morphology, significant after correction for multiple comparisons, for the right dorsal putamen (permutation test: p=0.02). The volume of the nucleus accumbens was 13% smaller in psychopathy (p corrected for multiple comparisons <0.006). The atypical morphology consisted of predominant anterior hypotrophy bilaterally (10-30%). Caudate and putamen local morphology displayed negative correlation with the lifestyle factor of the PCL-R (permutation test: p=0.05 and 0.03). From these data, psychopathy appears to be associated with an atypical striatal morphology, with highly significant global and local differences of the accumbens. This is consistent with the clinical syndrome and with theories of limbic involvement. Copyright © 2013 Elsevier Ltd. All rights reserved.

Atlas-based automatic segmentation of head and neck organs at risk and nodal target volumes: a clinical validation.

PubMed

Daisne, Jean-François; Blumhofer, Andreas

2013-06-26

Intensity modulated radiotherapy for head and neck cancer necessitates accurate definition of organs at risk (OAR) and clinical target volumes (CTV). This crucial step is time consuming and prone to inter- and intra-observer variations. Automatic segmentation by atlas deformable registration may help to reduce time and variations. We aim to test a new commercial atlas algorithm for automatic segmentation of OAR and CTV in both ideal and clinical conditions. The updated Brainlab automatic head and neck atlas segmentation was tested on 20 patients: 10 cN0-stages (ideal population) and 10 unselected N-stages (clinical population). Following manual delineation of OAR and CTV, automatic segmentation of the same set of structures was performed and afterwards manually corrected. Dice Similarity Coefficient (DSC), Average Surface Distance (ASD) and Maximal Surface Distance (MSD) were calculated for "manual to automatic" and "manual to corrected" volumes comparisons. In both groups, automatic segmentation saved about 40% of the corresponding manual segmentation time. This effect was more pronounced for OAR than for CTV. The edition of the automatically obtained contours significantly improved DSC, ASD and MSD. Large distortions of normal anatomy or lack of iodine contrast were the limiting factors. The updated Brainlab atlas-based automatic segmentation tool for head and neck Cancer patients is timesaving but still necessitates review and corrections by an expert.

Investigating the state-of-the-art in whole-body MR-based attenuation correction: an intra-individual, inter-system, inventory study on three clinical PET/MR systems.

PubMed

Beyer, Thomas; Lassen, Martin L; Boellaard, Ronald; Delso, Gaspar; Yaqub, Maqsood; Sattler, Bernhard; Quick, Harald H

2016-02-01

We assess inter- and intra-subject variability of magnetic resonance (MR)-based attenuation maps (MRμMaps) of human subjects for state-of-the-art positron emission tomography (PET)/MR imaging systems. Four healthy male subjects underwent repeated MR imaging with a Siemens Biograph mMR, Philips Ingenuity TF and GE SIGNA PET/MR system using product-specific MR sequences and image processing algorithms for generating MRμMaps. Total lung volumes and mean attenuation values in nine thoracic reference regions were calculated. Linear regression was used for comparing lung volumes on MRμMaps. Intra- and inter-system variability was investigated using a mixed effects model. Intra-system variability was seen for the lung volume of some subjects, (p = 0.29). Mean attenuation values across subjects were significantly different (p < 0.001) due to different segmentations of the trachea. Differences in the attenuation values caused noticeable intra-individual and inter-system differences that translated into a subsequent bias of the corrected PET activity values, as verified by independent simulations. Significant differences of MRμMaps generated for the same subjects but different PET/MR systems resulted in differences in attenuation correction factors, particularly in the thorax. These differences currently limit the quantitative use of PET/MR in multi-center imaging studies.

A multifractal approach to space-filling recovery for PET quantification.

PubMed

Willaime, Julien M Y; Aboagye, Eric O; Tsoumpas, Charalampos; Turkheimer, Federico E

2014-11-01

A new image-based methodology is developed for estimating the apparent space-filling properties of an object of interest in PET imaging without need for a robust segmentation step and used to recover accurate estimates of total lesion activity (TLA). A multifractal approach and the fractal dimension are proposed to recover the apparent space-filling index of a lesion (tumor volume, TV) embedded in nonzero background. A practical implementation is proposed, and the index is subsequently used with mean standardized uptake value (SUV mean) to correct TLA estimates obtained from approximate lesion contours. The methodology is illustrated on fractal and synthetic objects contaminated by partial volume effects (PVEs), validated on realistic (18)F-fluorodeoxyglucose PET simulations and tested for its robustness using a clinical (18)F-fluorothymidine PET test-retest dataset. TLA estimates were stable for a range of resolutions typical in PET oncology (4-6 mm). By contrast, the space-filling index and intensity estimates were resolution dependent. TLA was generally recovered within 15% of ground truth on postfiltered PET images affected by PVEs. Volumes were recovered within 15% variability in the repeatability study. Results indicated that TLA is a more robust index than other traditional metrics such as SUV mean or TV measurements across imaging protocols. The fractal procedure reported here is proposed as a simple and effective computational alternative to existing methodologies which require the incorporation of image preprocessing steps (i.e., partial volume correction and automatic segmentation) prior to quantification.

Analytical techniques for retrieval of atmospheric composition with the quadrupole mass spectrometer of the Sample Analysis at Mars instrument suite on Mars Science Laboratory

NASA Astrophysics Data System (ADS)

B. Franz, Heather; G. Trainer, Melissa; H. Wong, Michael; L. K. Manning, Heidi; C. Stern, Jennifer; R. Mahaffy, Paul; K. Atreya, Sushil; Benna, Mehdi; G. Conrad, Pamela; N. Harpold, Dan; A. Leshin, Laurie; A. Malespin, Charles; P. McKay, Christopher; Thomas Nolan, J.; Raaen, Eric

2014-06-01

The Sample Analysis at Mars (SAM) instrument suite is the largest scientific payload on the Mars Science Laboratory (MSL) Curiosity rover, which landed in Mars' Gale Crater in August 2012. As a miniature geochemical laboratory, SAM is well-equipped to address multiple aspects of MSL's primary science goal, characterizing the potential past or present habitability of Gale Crater. Atmospheric measurements support this goal through compositional investigations relevant to martian climate evolution. SAM instruments include a quadrupole mass spectrometer, a tunable laser spectrometer, and a gas chromatograph that are used to analyze martian atmospheric gases as well as volatiles released by pyrolysis of solid surface materials (Mahaffy et al., 2012). This report presents analytical methods for retrieving the chemical and isotopic composition of Mars' atmosphere from measurements obtained with SAM's quadrupole mass spectrometer. It provides empirical calibration constants for computing volume mixing ratios of the most abundant atmospheric species and analytical functions to correct for instrument artifacts and to characterize measurement uncertainties. Finally, we discuss differences in volume mixing ratios of the martian atmosphere as determined by SAM (Mahaffy et al., 2013) and Viking (Owen et al., 1977; Oyama and Berdahl, 1977) from an analytical perspective. Although the focus of this paper is atmospheric observations, much of the material concerning corrections for instrumental effects also applies to reduction of data acquired with SAM from analysis of solid samples. The Sample Analysis at Mars (SAM) instrument measures the composition of the martian atmosphere. Rigorous calibration of SAM's mass spectrometer was performed with relevant gas mixtures. Calibration included derivation of a new model to correct for electron multiplier effects. Volume mixing ratios for Ar and N2 obtained with SAM differ from those obtained with Viking. Differences between SAM and Viking volume mixing ratios are under investigation.

A New CT Reconstruction Technique Using Adaptive Deformation Recovery and Intensity Correction (ADRIC)

PubMed Central

Zhang, You; Ma, Jianhua; Iyengar, Puneeth; Zhong, Yuncheng; Wang, Jing

2017-01-01

Purpose Sequential same-patient CT images may involve deformation-induced and non-deformation-induced voxel intensity changes. An adaptive deformation recovery and intensity correction (ADRIC) technique was developed to improve the CT reconstruction accuracy, and to separate deformation from non-deformation-induced voxel intensity changes between sequential CT images. Materials and Methods ADRIC views the new CT volume as a deformation of a prior high-quality CT volume, but with additional non-deformation-induced voxel intensity changes. ADRIC first applies the 2D-3D deformation technique to recover the deformation field between the prior CT volume and the new, to-be-reconstructed CT volume. Using the deformation-recovered new CT volume, ADRIC further corrects the non-deformation-induced voxel intensity changes with an updated algebraic reconstruction technique (‘ART-dTV’). The resulting intensity-corrected new CT volume is subsequently fed back into the 2D-3D deformation process to further correct the residual deformation errors, which forms an iterative loop. By ADRIC, the deformation field and the non-deformation voxel intensity corrections are optimized separately and alternately to reconstruct the final CT. CT myocardial perfusion imaging scenarios were employed to evaluate the efficacy of ADRIC, using both simulated data of the extended-cardiac-torso (XCAT) digital phantom and experimentally acquired porcine data. The reconstruction accuracy of the ADRIC technique was compared to the technique using ART-dTV alone, and to the technique using 2D-3D deformation alone. The relative error metric and the universal quality index metric are calculated between the images for quantitative analysis. The relative error is defined as the square root of the sum of squared voxel intensity differences between the reconstructed volume and the ‘ground-truth’ volume, normalized by the square root of the sum of squared ‘ground-truth’ voxel intensities. In addition to the XCAT and porcine studies, a physical lung phantom measurement study was also conducted. Water-filled balloons with various shapes/volumes and concentrations of iodinated contrasts were put inside the phantom to simulate both deformations and non-deformation-induced intensity changes for ADRIC reconstruction. The ADRIC-solved deformations and intensity changes from limited-view projections were compared to those of the ‘gold-standard’ volumes reconstructed from fully-sampled projections. Results For the XCAT simulation study, the relative errors of the reconstructed CT volume by the 2D-3D deformation technique, the ART-dTV technique and the ADRIC technique were 14.64%, 19.21% and 11.90% respectively, by using 20 projections for reconstruction. Using 60 projections for reconstruction reduced the relative errors to 12.33%, 11.04% and 7.92% for the three techniques, respectively. For the porcine study, the corresponding results were 13.61%, 8.78%, 6.80% by using 20 projections; and 12.14%, 6.91% and 5.29% by using 60 projections. The ADRIC technique also demonstrated robustness to varying projection exposure levels. For the physical phantom study, the average DICE coefficient between the initial prior balloon volume and the new ‘gold-standard’ balloon volumes was 0.460. ADRIC reconstruction by 21 projections increased the average DICE coefficient to 0.954. Conclusion The ADRIC technique outperformed both the 2D-3D deformation technique and the ART-dTV technique in reconstruction accuracy. The alternately solved deformation field and non-deformation voxel intensity corrections can benefit multiple clinical applications, including tumor tracking, radiotherapy dose accumulation and treatment outcome analysis. PMID:28380247

WE-G-18A-03: Cone Artifacts Correction in Iterative Cone Beam CT Reconstruction

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

Yan, H; Folkerts, M; Jiang, S

Purpose: For iterative reconstruction (IR) in cone-beam CT (CBCT) imaging, data truncation along the superior-inferior (SI) direction causes severe cone artifacts in the reconstructed CBCT volume images. Not only does it reduce the effective SI coverage of the reconstructed volume, it also hinders the IR algorithm convergence. This is particular a problem for regularization based IR, where smoothing type regularization operations tend to propagate the artifacts to a large area. It is our purpose to develop a practical cone artifacts correction solution. Methods: We found it is the missing data residing in the truncated cone area that leads to inconsistencymore » between the calculated forward projections and measured projections. We overcome this problem by using FDK type reconstruction to estimate the missing data and design weighting factors to compensate the inconsistency caused by the missing data. We validate the proposed methods in our multi-GPU low-dose CBCT reconstruction system on multiple patients' datasets. Results: Compared to the FDK reconstruction with full datasets, while IR is able to reconstruct CBCT images using a subset of projection data, the severe cone artifacts degrade overall image quality. For head-neck case under a full-fan mode, 13 out of 80 slices are contaminated. It is even more severe in pelvis case under half-fan mode, where 36 out of 80 slices are affected, leading to inferior soft-tissue delineation. By applying the proposed method, the cone artifacts are effectively corrected, with a mean intensity difference decreased from ∼497 HU to ∼39HU for those contaminated slices. Conclusion: A practical and effective solution for cone artifacts correction is proposed and validated in CBCT IR algorithm. This study is supported in part by NIH (1R01CA154747-01)« less

Three-dimensional CT might be a potential evaluation modality in correction of asymmetrical masseter muscle hypertrophy by botulinum toxin injection.

PubMed

No, Yeon A; Ahn, Byeong Heon; Kim, Beom Joon; Kim, Myeung Nam; Hong, Chang Kwon

2016-01-01

For correction of this asymmetrical hypertrophy, botulinum toxin type A (BTxA) injection is one of convenient treatment modalities. Unfortunately, physical examination of masseter muscle is not enough to estimate the exact volume of muscle hypertrophy difference. Two Koreans, male and female, of bilateral masseter hypertrophy with asymmetricity were evaluated. BTxA (NABOTA(®), Daewoong, Co. Ltd., Seoul, Korea) was injected at master muscle site with total 50 U (25 U at each side) and volume change was evaluated with three-dimensional (3D) CT image analysis. Maximum reduction of masseter hypertrophy was recognized at 2-month follow-up and reduced muscle size started to restore after 3 months. Mean reduction of masseter muscle volume was 36% compared with baseline. More hypertrophied side of masseter muscle presented 42% of volume reduction at 2-month follow-up but less hypertrophied side of masseter muscle showed 30% of volume shrinkage. In conclusion, 3D CT image analysis might be the exact evaluation tool for correction of asymmetrical masseter hypertrophy by botulinum toxin injection.

Automated measurements for individualized heart rate correction of the QT interval.

PubMed

Mason, Jay W; Moon, Thomas E

2015-04-01

Subject-specific electrocardiographic QT interval correction for heart rate is often used in clinical trials with frequent electrocardiographic recordings. However, in these studies relatively few 10-s, 12-lead electrocardiograms may be available for calculating the individual correction. Highly automated QT and RR measurement tools have made it practical to measure electrocardiographic intervals on large volumes of continuous electrocardiogram data. The purpose of this study was to determine whether an automated method can be used in lieu of a manual method. In 49 subjects who completed all treatments in a four-armed crossover study we compared two methods for derivation of individualized rate-correction coefficients: manual measurement on 10-s electrocardiograms and automated measurement of QT and RR during continuous 24-h electrocardiogram recordings. The four treatments, received by each subject in a latin-square randomization sequence were placebo, moxifloxacin, and two doses of an investigational drug. Analysis of continuous electrocardiogram data yielded a lower standard deviation of QT:RR regression values than the manual method, though the differences were not statistically significant. The within-subject and within-treatment coefficients of variation between the manual and automated methods were not significantly different. Corrected QT values from the two methods had similar rates of true and false positive identification of moxifloxacin's QT prolonging effect. An automated method for individualized rate correction applied to continuous electrocardiogram data could be advantageous in clinical trials, as the automated method is simpler, is based upon a much larger volume of data, yields similar results, and requires no human over-reading of the measurements. © The Author(s) 2015.

T1- and T2*-dominant extravasation correction in DSC-MRI: Part I—theoretical considerations and implications for assessment of tumor hemodynamic properties

PubMed Central

Bjornerud, Atle; Sorensen, A Gregory; Mouridsen, Kim; Emblem, Kyrre E

2011-01-01

We present a novel contrast agent (CA) extravasation-correction method based on analysis of the tissue residue function for assessment of multiple hemodynamic parameters. The method enables semiquantitative determination of the transfer constant and can be used to distinguish between T1- and T2*-dominant extravasation effects, while being insensitive to variations in tissue mean transit time (MTT). Results in 101 patients with confirmed glioma suggest that leakage-corrected absolute cerebral blood volume (CBV) values obtained with the proposed method provide improved overall survival prediction compared with normalized CBV values combined with an established leakage-correction method. Using a standard gradient-echo echo-planar imaging sequence, ∼60% and 10% of tumors with detectable CA extravasation mainly exhibited T1- and T2*-dominant leakage effects, respectively. The remaining 30% of leaky tumors had mixed T1- and T2*-dominant effects. Using an MTT-sensitive correction method, our results show that CBV is underestimated when tumor MTT is significantly longer than MTT in the reference tissue. Furthermore, results from our simulations suggest that the relative contribution of T1- versus T2*-dominant extravasation effects is strongly dependent on the effective transverse relaxivity in the extravascular space and may thus be a potential marker for cellular integrity and tissue structure. PMID:21505483

Associations between regional brain volumes at term-equivalent age and development at 2 years of age in preterm children.

PubMed

Lind, Annika; Parkkola, Riitta; Lehtonen, Liisa; Munck, Petriina; Maunu, Jonna; Lapinleimu, Helena; Haataja, Leena

2011-08-01

Altered brain volumes and associations between volumes and developmental outcomes have been reported in prematurely born children. To assess which regional brain volumes are different in very low birth weight (VLBW) children without neurodevelopmental impairments ([NDI] cerebral palsy, hearing loss, blindness and significantly delayed cognitive performance) compared with VLBW children with NDI, and to evaluate the association between regional brain volumes at term-equivalent age and cognitive development and neurological performance at a corrected age of 2 years. The study group consisted of a regional cohort of 164 VLBW children, divided into one group of children without NDI (n = 148) and one group of children with NDI (n = 16). Brain (MRI) was performed at term-equivalent age, from which brain volumes were manually analysed. Cognitive development was assessed with the Bayley Scales of Infant Development II (BSID-II), and neurological performance with the Hammersmith Infant Neurological Examination at the corrected age of 2 years. The volumes of total brain tissue, cerebrum, frontal lobes, basal ganglia and thalami, and cerebellum were significantly smaller, and the volume of the ventricles significantly larger, in the children with NDI than in those without NDI. Even in children without NDI, a smaller cerebellar volume was significantly correlated with poor neurological performance at 2 years of corrected age. Volumetric analysis at brain MRI can provide an additional parameter for early prediction of outcome in VLBW children.

Spectral distribution of particle fluence in small field detectors and its implication on small field dosimetry.

PubMed

Benmakhlouf, Hamza; Andreo, Pedro

2017-02-01

Correction factors for the relative dosimetry of narrow megavoltage photon beams have recently been determined in several publications. These corrections are required because of the several small-field effects generally thought to be caused by the lack of lateral charged particle equilibrium (LCPE) in narrow beams. Correction factors for relative dosimetry are ultimately necessary to account for the fluence perturbation caused by the detector. For most small field detectors the perturbation depends on field size, resulting in large correction factors when the field size is decreased. In this work, electron and photon fluence differential in energy will be calculated within the radiation sensitive volume of a number of small field detectors for 6 MV linear accelerator beams. The calculated electron spectra will be used to determine electron fluence perturbation as a function of field size and its implication on small field dosimetry analyzed. Fluence spectra were calculated with the user code PenEasy, based on the PENELOPE Monte Carlo system. The detectors simulated were one liquid ionization chamber, two air ionization chambers, one diamond detector, and six silicon diodes, all manufactured either by PTW or IBA. The spectra were calculated for broad (10 cm × 10 cm) and narrow (0.5 cm × 0.5 cm) photon beams in order to investigate the field size influence on the fluence spectra and its resulting perturbation. The photon fluence spectra were used to analyze the impact of absorption and generation of photons. These will have a direct influence on the electrons generated in the detector radiation sensitive volume. The electron fluence spectra were used to quantify the perturbation effects and their relation to output correction factors. The photon fluence spectra obtained for all detectors were similar to the spectrum in water except for the shielded silicon diodes. The photon fluence in the latter group was strongly influenced, mostly in the low-energy region, by photoabsorption in the high-Z shielding material. For the ionization chambers and the diamond detector, the electron fluence spectra were found to be similar to that in water, for both field sizes. In contrast, electron spectra in the silicon diodes were much higher than that in water for both field sizes. The estimated perturbations of the fluence spectra for the silicon diodes were 11-21% for the large fields and 14-27% for the small fields. These perturbations are related to the atomic number, density and mean excitation energy (I-value) of silicon, as well as to the influence of the "extracameral"' components surrounding the detector sensitive volume. For most detectors the fluence perturbation was also found to increase when the field size was decreased, in consistency with the increased small-field effects observed for the smallest field sizes. The present work improves the understanding of small-field effects by relating output correction factors to spectral fluence perturbations in small field detectors. It is shown that the main reasons for the well-known small-field effects in silicon diodes are the high-Z and density of the "extracameral" detector components and the high I-value of silicon relative to that of water and diamond. Compared to these parameters, the density and atomic number of the radiation sensitive volume material play a less significant role. © 2016 American Association of Physicists in Medicine.

Neonatal Plasma Transfusion: An Evidence-Based Review.

PubMed

Keir, Amy K; Stanworth, Simon J

2016-10-01

Several clinical scenarios for plasma transfusion are repeatedly identified in audits, including treatment of bleeding in association with laboratory evidence of coagulopathy, correction of disseminated intravascular coagulation, prevention of intraventricular hemorrhage, management of critically ill neonates (eg, during sepsis or as a volume expander), or correction of markers of prolonged coagulation in the absence of bleeding. The findings of at least one national audit of transfusion practice indicated that almost half of plasma transfusions are given to neonates with abnormal coagulation values with no evidence of active bleeding, despite the limited evidence base to support the effectiveness of this practice. Plasma transfusions to neonates should be considered in the clinical context of bleeding (eg, vitamin K dependent), disseminated intravascular coagulation, and very rare inherited deficiencies of coagulation factors. There seems to be no role for prophylactic plasma to prevent intraventricular hemorrhage or for use as a volume expander. Copyright © 2016 Elsevier Inc. All rights reserved.

Effects of solvent composition in the normal-phase liquid chromatography of alkylphenols and naphthols

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

Hurtubise, R.J.; Hussain, A.; Silver, H.F.

1981-11-01

The normal-phase liquid chromatographic models of Scott, Snyder, and Soczewinski were considered for a ..mu..-Bondapak NH/sub 2/ stationary phase. n-Heptane:2-propanol and n-heptane:ethyl acetate mobile phases of different compositions were used. Linear relationships were obtained from graphs of log K' vs. log mole fraction of the strong solvent for both n-heptane:2-propanol and n-heptane:ethyl acetate mobile phases. A linear relationship was obtained between the reciprocal of corrected retention volume and % wt/v of 2-propanol but not between the reciprocal of corrected retention volume and % wt/v of ethyl acetate. The slopes and intercept terms from the Snyder and Soczewinski models were foundmore » to approximately describe interactions with ..mu..-Bondapak NH/sub 2/. Capacity factors can be predicted for the compounds by using the equations obtained from mobile phase composition variation experiments.« less

Arterial Transit Time-corrected Renal Blood Flow Measurement with Pulsed Continuous Arterial Spin Labeling MR Imaging.

PubMed

Shimizu, Kazuhiro; Kosaka, Nobuyuki; Fujiwara, Yasuhiro; Matsuda, Tsuyoshi; Yamamoto, Tatsuya; Tsuchida, Tatsuro; Tsuchiyama, Katsuki; Oyama, Nobuyuki; Kimura, Hirohiko

2017-01-10

The importance of arterial transit time (ATT) correction for arterial spin labeling MRI has been well debated in neuroimaging, but it has not been well evaluated in renal imaging. The purpose of this study was to evaluate the feasibility of pulsed continuous arterial spin labeling (pcASL) MRI with multiple post-labeling delay (PLD) acquisition for measuring ATT-corrected renal blood flow (ATC-RBF). A total of 14 volunteers were categorized into younger (n = 8; mean age, 27.0 years) and older groups (n = 6; 64.8 years). Images of pcASL were obtained at three different PLDs (0.5, 1.0, and 1.5 s), and ATC-RBF and ATT were calculated using a single-compartment model. To validate ATC-RBF, a comparative study of effective renal plasma flow (ERPF) measured by 99m Tc-MAG3 scintigraphy was performed. ATC-RBF was corrected by kidney volume (ATC-cRBF) for comparison with ERPF. The younger group showed significantly higher ATC-RBF (157.68 ± 38.37 mL/min/100 g) and shorter ATT (961.33 ± 260.87 ms) than the older group (117.42 ± 24.03 mL/min/100 g and 1227.94 ± 226.51 ms, respectively; P < 0.05). A significant correlation was evident between ATC-cRBF and ERPF (P < 0.05, r = 0.47). With suboptimal single PLD (1.5 s) settings, there was no significant correlation between ERPF and kidney volume-corrected RBF calculated from single PLD data. Calculation of ATT and ATC-RBF by pcASL with multiple PLD was feasible in healthy volunteers, and differences in ATT and ATC-RBF were seen between the younger and older groups. Although ATT correction by multiple PLD acquisitions may not always be necessary for RBF quantification in the healthy subjects, the effect of ATT should be taken into account in renal ASL-MRI as debated in brain imaging.

Prognostic value of cardiovascular magnetic resonance imaging measurements corrected for age and sex in idiopathic pulmonary arterial hypertension.

PubMed

Swift, Andrew J; Rajaram, Smitha; Campbell, Michael J; Hurdman, Judith; Thomas, Steve; Capener, Dave; Elliot, Charlie; Condliffe, Robin; Wild, Jim M; Kiely, David G

2014-01-01

There are limited data on the prognostic value of cardiovascular magnetic resonance measurements in idiopathic pulmonary arterial hypertension, with no studies investigating the impact of correction of cardiovascular magnetic resonance indices for age and sex on prognostic value. Consecutive patients with idiopathic pulmonary arterial hypertension underwent cardiovascular magnetic resonance imaging at 1.5T. Steady-state free precession cardiac volumes and mass measurements were corrected for age, sex, and body surface area according to reference data and prognostic significance assessed. A total of 80 patients with idiopathic pulmonary arterial hypertension were identified, and 23 patients died during the mean follow-up of 32±14 months. Corrected for age, sex, and body surface area, right ventricular end-systolic volume (P=0.004) strongly predicted mortality, independent of World Health Organization functional class, mean right atrial pressure, cardiac index, and mixed venous oxygen saturations. Consideration should be given to correcting cardiovascular magnetic resonance measures for age, sex, and body surface area, particularly given the changing demographics of patients with idiopathic pulmonary arterial hypertension. Corrected right ventricular end-systolic volume is a strong prognostic marker in idiopathic pulmonary arterial hypertension, independent of invasively derived measurements, mean right atrial pressure cardiac index, and mixed venous oxygen saturations.

Intraperitoneal pressure and volume of gas injected as effective parameters of the correct position of the Veress needle during creation of pneumoperitoneum.

PubMed

Azevedo, João L M C; Azevedo, Otavio C; Sorbello, Albino A; Becker, Otavio M; Hypolito, Otavio; Freire, Dalmer; Miyahira, Susana; Guedes, Afonso; Azevedo, Glicia C

2009-12-01

The aim of this work was to establish reliable parameters of the correct position of the Veress needle in the peritoneal cavity during creation of pneumoperitoneum. The Veress needle was inserted into the peritoneal cavity of 100 selected patients, and a carbon-dioxide flow rate of 1.2 L/min and a maximum pressure of 12 mm Hg were established. Intraperitoneal pressure (IP) and the volume of gas injected (VG) were recorded at the beginning of insufflation and at every 20 seconds. Correlations were established for pressure and volume in function of time. Values of IP and VG were predicted at 1, 2, 3, and 4 minutes of insufflation, by applying the following formulas: IP = 2.3083 + 0.0266 x time +8.3 x 10(-5) x time(2) - 2.44 x 10(-7) x time(3); and VG = 0.813 + 0.0157 x time. A strong correlation was observed between IP and preestablished time points during creation of the pneumoperitoneum, as well as between VG and preestablished time points during creation of the pneumoperitoneum, with a coefficient of determination of 0.8011 for IP and of 0.9604 for VG. The predicted values were as follows: 1 minute = 4.15; 2 minutes = 6.27; 3 minutes = 8.36; and 4 minutes = 10.10 for IP (mm Hg); and 1 minute = 1.12; 2 minutes = 2.07; 3 minutes = 3.01; and 4 minutes = 3.95 for VG (L). Values of IP and VG at given time points during insufflation for creation of the pneumoperitoneum, using the Veress needle, can be effective parameters to determine whether the needle is correctly positioned in the peritoneal cavity.

Refractive errors and corrections for OCT images in an inflated lung phantom

PubMed Central

Golabchi, Ali; Faust, J.; Golabchi, F. N.; Brooks, D. H.; Gouldstone, A.; DiMarzio, C. A.

2012-01-01

Visualization and correct assessment of alveolar volume via intact lung imaging is important to study and assess respiratory mechanics. Optical Coherence Tomography (OCT), a real-time imaging technique based on near-infrared interferometry, can image several layers of distal alveoli in intact, ex vivo lung tissue. However optical effects associated with heterogeneity of lung tissue, including the refraction caused by air-tissue interfaces along alveoli and duct walls, and changes in speed of light as it travels through the tissue, result in inaccurate measurement of alveolar volume. Experimentally such errors have been difficult to analyze because of lack of ’ground truth,’ as the lung has a unique microstructure of liquid-coated thin walls surrounding relatively large airspaces, which is difficult to model with cellular foams. In addition, both lung and foams contain airspaces of highly irregular shape, further complicating quantitative measurement of optical artifacts and correction. To address this we have adapted the Bragg-Nye bubble raft, a crystalline two-dimensional arrangement of elements similar in geometry to alveoli (up to several hundred μm in diameter with thin walls) as an inflated lung phantom in order to understand, analyze and correct these errors. By applying exact optical ray tracing on OCT images of the bubble raft, the errors are predicted and corrected. The results are validated by imaging the bubble raft with OCT from one edge and with a charged coupled device (CCD) camera in transillumination from top, providing ground truth for the OCT. PMID:22567599

Size distribution and volume fraction of T(1) phase precipitates from TEM images: Direct measurements and related correction.

PubMed

Dorin, Thomas; Donnadieu, Patricia; Chaix, Jean-Marc; Lefebvre, Williams; Geuser, Frédéric De; Deschamps, Alexis

2015-11-01

Transmission Electron Microscopy (TEM) can be used to measure the size distribution and volume fraction of fine scale precipitates in metallic systems. However, such measurements suffer from a number of artefacts that need to be accounted for, related to the finite thickness of the TEM foil and to the projected observation in two dimensions of the microstructure. We present a correction procedure to describe the 3D distribution of disc-like particles and apply this method to the plate-like T1 precipitates in an Al-Li-Cu alloy in two ageing conditions showing different particle morphologies. The precipitates were imaged in a High-Angular Annular Dark Field Microscope (HAADF-STEM). The corrected size distribution is further used to determine the precipitate volume fraction. Atom probe tomography (APT) is finally utilised as an alternative way to measure the precipitate volume fraction and test the validity of the electron microscopy results. Copyright © 2015 Elsevier Ltd. All rights reserved.

NTCP modelling of lung toxicity after SBRT comparing the universal survival curve and the linear quadratic model for fractionation correction.

PubMed

Wennberg, Berit M; Baumann, Pia; Gagliardi, Giovanna; Nyman, Jan; Drugge, Ninni; Hoyer, Morten; Traberg, Anders; Nilsson, Kristina; Morhed, Elisabeth; Ekberg, Lars; Wittgren, Lena; Lund, Jo-Åsmund; Levin, Nina; Sederholm, Christer; Lewensohn, Rolf; Lax, Ingmar

2011-05-01

In SBRT of lung tumours no established relationship between dose-volume parameters and the incidence of lung toxicity is found. The aim of this study is to compare the LQ model and the universal survival curve (USC) to calculate biologically equivalent doses in SBRT to see if this will improve knowledge on this relationship. Toxicity data on radiation pneumonitis grade 2 or more (RP2+) from 57 patients were used, 10.5% were diagnosed with RP2+. The lung DVHs were corrected for fractionation (LQ and USC) and analysed with the Lyman- Kutcher-Burman (LKB) model. In the LQ-correction α/β = 3 Gy was used and the USC parameters used were: α/β = 3 Gy, D(0) = 1.0 Gy, [Formula: see text] = 10, α = 0.206 Gy(-1) and d(T) = 5.8 Gy. In order to understand the relative contribution of different dose levels to the calculated NTCP the concept of fractional NTCP was used. This might give an insight to the questions of whether "high doses to small volumes" or "low doses to large volumes" are most important for lung toxicity. NTCP analysis with the LKB-model using parameters m = 0.4, D(50) = 30 Gy resulted for the volume dependence parameter (n) with LQ correction n = 0.87 and with USC correction n = 0.71. Using parameters m = 0.3, D(50) = 20 Gy n = 0.93 with LQ correction and n = 0.83 with USC correction. In SBRT of lung tumours, NTCP modelling of lung toxicity comparing models (LQ,USC) for fractionation correction, shows that low dose contribute less and high dose more to the NTCP when using the USC-model. Comparing NTCP modelling of SBRT data and data from breast cancer, lung cancer and whole lung irradiation implies that the response of the lung is treatment specific. More data are however needed in order to have a more reliable modelling.

Noise suppressed partial volume correction for cardiac SPECT/CT

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

Chan, Chung; Liu, Chi, E-mail: chi.liu@yale.edu

Purpose: Partial volume correction (PVC) methods typically improve quantification at the expense of increased image noise and reduced reproducibility. In this study, the authors developed a novel voxel-based PVC method that incorporates anatomical knowledge to improve quantification while suppressing noise for cardiac SPECT/CT imaging. Methods: In the proposed method, the SPECT images were first reconstructed using anatomical-based maximum a posteriori (AMAP) with Bowsher’s prior to penalize noise while preserving boundaries. A sequential voxel-by-voxel PVC approach (Yang’s method) was then applied on the AMAP reconstruction using a template response. This template response was obtained by forward projecting a template derived frommore » a contrast-enhanced CT image, and then reconstructed using AMAP to model the partial volume effects (PVEs) introduced by both the system resolution and the smoothing applied during reconstruction. To evaluate the proposed noise suppressed PVC (NS-PVC), the authors first simulated two types of cardiac SPECT studies: a {sup 99m}Tc-tetrofosmin myocardial perfusion scan and a {sup 99m}Tc-labeled red blood cell (RBC) scan on a dedicated cardiac multiple pinhole SPECT/CT at both high and low count levels. The authors then applied the proposed method on a canine equilibrium blood pool study following injection with {sup 99m}Tc-RBCs at different count levels by rebinning the list-mode data into shorter acquisitions. The proposed method was compared to MLEM reconstruction without PVC, two conventional PVC methods, including Yang’s method and multitarget correction (MTC) applied on the MLEM reconstruction, and AMAP reconstruction without PVC. Results: The results showed that the Yang’s method improved quantification, however, yielded increased noise and reduced reproducibility in the regions with higher activity. MTC corrected for PVE on high count data with amplified noise, although yielded the worst performance among all the methods tested on low-count data. AMAP effectively suppressed noise and reduced the spill-in effect in the low activity regions. However it was unable to reduce the spill-out effect in high activity regions. NS-PVC yielded superior performance in terms of both quantitative assessment and visual image quality while improving reproducibility. Conclusions: The results suggest that NS-PVC may be a promising PVC algorithm for application in low-dose protocols, and in gated and dynamic cardiac studies with low counts.« less

78 FR 68161 - Greenhouse Gas Reporting Program: Final Amendments and Confidentiality Determinations for...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-13

... measurements corrected for temperature and non-ideal gas behavior). For gases with low volume consumption for... effect of that abatement system when using either the emission factors and calculation methods in 40 CFR...) basis. To develop the preliminary estimate, the reporter must use the gas consumption in the tools...

Flight effects on the aerodynamic and acoustic characteristics of inverted profile coannular nozzles, volume 2. [supersonic cruise aircraft research wind tunnel tests

NASA Technical Reports Server (NTRS)

Kozlowski, H.; Packman, A. B.

1978-01-01

Data from the acoustic tests of the convergent reference nozzle and the 0.75 area ratio coannular nozzle are presented in tables. Data processing routines used to scale the acoustic data and to correct the data for atmospheric attenuation are included.

The Real-Time Wall Interference Correction System of the NASA Ames 12-Foot Pressure Wind Tunnel

NASA Technical Reports Server (NTRS)

Ulbrich, Norbert

1998-01-01

An improved version of the Wall Signature Method was developed to compute wall interference effects in three-dimensional subsonic wind tunnel testing of aircraft models in real-time. The method may be applied to a full-span or a semispan model. A simplified singularity representation of the aircraft model is used. Fuselage, support system, propulsion simulator, and separation wake volume blockage effects are represented by point sources and sinks. Lifting effects are represented by semi-infinite line doublets. The singularity representation of the test article is combined with the measurement of wind tunnel test reference conditions, wall pressure, lift force, thrust force, pitching moment, rolling moment, and pre-computed solutions of the subsonic potential equation to determine first order wall interference corrections. Second order wall interference corrections for pitching and rolling moment coefficient are also determined. A new procedure is presented that estimates a rolling moment coefficient correction for wings with non-symmetric lift distribution. Experimental data obtained during the calibration of the Ames Bipod model support system and during tests of two semispan models mounted on an image plane in the NASA Ames 12 ft. Pressure Wind Tunnel are used to demonstrate the application of the wall interference correction method.

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

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

Nakayama, Masao, E-mail: naka2008@med.kobe-u.ac.jp; Yoshida, Kenji; Nishimura, Hideki

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,more » 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.« less

Improving the accuracy of ionization chamber dosimetry in small megavoltage x-ray fields

NASA Astrophysics Data System (ADS)

McNiven, Andrea L.

The dosimetry of small x-ray fields is difficult, but important, in many radiation therapy delivery methods. The accuracy of ion chambers for small field applications, however, is limited due to the relatively large size of the chamber with respect to the field size, leading to partial volume effects, lateral electronic disequilibrium and calibration difficulties. The goal of this dissertation was to investigate the use of ionization chambers for the purpose of dosimetry in small megavoltage photon beams with the aim of improving clinical dose measurements in stereotactic radiotherapy and helical tomotherapy. A new method for the direct determination of the sensitive volume of small-volume ion chambers using micro computed tomography (muCT) was investigated using four nominally identical small-volume (0.56 cm3) cylindrical ion chambers. Agreement between their measured relative volume and ionization measurements (within 2%) demonstrated the feasibility of volume determination through muCT. Cavity-gas calibration coefficients were also determined, demonstrating the promise for accurate ion chamber calibration based partially on muCT. The accuracy of relative dose factor measurements in 6MV stereotactic x-ray fields (5 to 40mm diameter) was investigated using a set of prototype plane-parallel ionization chambers (diameters of 2, 4, 10 and 20mm). Chamber and field size specific correction factors ( CSFQ ), that account for perturbation of the secondary electron fluence, were calculated using Monte Carlo simulation methods (BEAM/EGSnrc simulations). These correction factors (e.g. CSFQ = 1.76 (2mm chamber, 5mm field) allow for accurate relative dose factor (RDF) measurement when applied to ionization readings, under conditions of electronic disequilibrium. With respect to the dosimetry of helical tomotherapy, a novel application of the ion chambers was developed to characterize the fan beam size and effective dose rate. Characterization was based on an adaptation of the computed tomography dose index (CTDI), a concept normally used in diagnostic radiology. This involved experimental determination of the fan beam thickness using the ion chambers to acquire fan beam profiles and extrapolation to a 'zero-size' detector. In conclusion, improvements have been made in the accuracy of small field dosimetry measurements in stereotactic radiotherapy and helical tomotherapy. This was completed through introduction of an original technique involving micro-CT imaging for sensitive volume determination and potentially ion chamber calibration coefficients, the use of appropriate Monte Carlo derived correction factors for RDF measurement, and the exploitation of the partial volume effect for helical tomotherapy fan beam dosimetry. With improved dosimetry for a wide range of challenging small x-ray field situations, it is expected that the patient's radiation safety will be maintained, and that clinical trials will adopt calibration protocols specialized for modern radiotherapy with small fields or beamlets. Keywords. radiation therapy, ionization chambers, small field dosimetry, stereotactic radiotherapy, helical tomotherapy, micro-CT.

Experimental evaluation of a mathematical model for predicting transfer efficiency of a high volume-low pressure air spray gun.

PubMed

Tan, Y M; Flynn, M R

2000-10-01

The transfer efficiency of a spray-painting gun is defined as the amount of coating applied to the workpiece divided by the amount sprayed. Characterizing this transfer process allows for accurate estimation of the overspray generation rate, which is important for determining a spray painter's exposure to airborne contaminants. This study presents an experimental evaluation of a mathematical model for predicting the transfer efficiency of a high volume-low pressure spray gun. The effects of gun-to-surface distance and nozzle pressure on the agreement between the transfer efficiency measurement and prediction were examined. Wind tunnel studies and non-volatile vacuum pump oil in place of commercial paint were used to determine transfer efficiency at nine gun-to-surface distances and four nozzle pressure levels. The mathematical model successfully predicts transfer efficiency within the uncertainty limits. The least squares regression between measured and predicted transfer efficiency has a slope of 0.83 and an intercept of 0.12 (R2 = 0.98). Two correction factors were determined to improve the mathematical model. At higher nozzle pressure settings, 6.5 psig and 5.5 psig, the correction factor is a function of both gun-to-surface distance and nozzle pressure level. At lower nozzle pressures, 4 psig and 2.75 psig, gun-to-surface distance slightly influences the correction factor, while nozzle pressure has no discernible effect.

Exact mode volume and Purcell factor of open optical systems

NASA Astrophysics Data System (ADS)

Muljarov, E. A.; Langbein, W.

2016-12-01

The Purcell factor quantifies the change of the radiative decay of a dipole in an electromagnetic environment relative to free space. Designing this factor is at the heart of photonics technology, striving to develop ever smaller or less lossy optical resonators. The Purcell factor can be expressed using the electromagnetic eigenmodes of the resonators, introducing the notion of a mode volume for each mode. This approach allows an analytic treatment, reducing the Purcell factor and other observables to sums over eigenmode resonances. Calculating the mode volumes requires a correct normalization of the modes. We introduce an exact normalization of modes, not relying on perfectly matched layers. We present an analytic theory of the Purcell effect based on this exact mode normalization and the resulting effective mode volume. We use a homogeneous dielectric sphere in vacuum, which is analytically solvable, to exemplify these findings. We furthermore verify the applicability of the normalization to numerically determined modes of a finite dielectric cylinder.

Dynamic Collimator Angle Adjustments During Volumetric Modulated Arc Therapy to Account for Prostate Rotations

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

Boer, Johan de; Wolf, Anne Lisa; Szeto, Yenny Z.

2015-04-01

Purpose: Rotations of the prostate gland induce considerable geometric uncertainties in prostate cancer radiation therapy. Collimator and gantry angle adjustments can correct these rotations in intensity modulated radiation therapy. Modern volumetric modulated arc therapy (VMAT) treatments, however, include a wide range of beam orientations that differ in modulation, and corrections require dynamic collimator rotations. The aim of this study was to implement a rotation correction strategy for VMAT dose delivery and validate it for left-right prostate rotations. Methods and Materials: Clinical VMAT treatment plans of 5 prostate cancer patients were used. Simulated left-right prostate rotations between +15° and −15° weremore » corrected by collimator rotations. We compared corrected and uncorrected plans by dose volume histograms, minimum dose (D{sub min}) to the prostate, bladder surface receiving ≥78 Gy (S78) and rectum equivalent uniform dose (EUD; n=0.13). Each corrected plan was delivered to a phantom, and its deliverability was evaluated by γ-evaluation between planned and delivered dose, which was reconstructed from portal images acquired during delivery. Results: On average, clinical target volume minimum dose (D{sub min}) decreased up to 10% without corrections. Negative left-right rotations were corrected almost perfectly, whereas D{sub min} remained within 4% for positive rotations. Bladder S78 and rectum EUD of the corrected plans matched those of the original plans. The average pass rate for the corrected plans delivered to the phantom was 98.9% at 3% per 3 mm gamma criteria. The measured dose in the planning target volume approximated the original dose, rotated around the simulated left-right angle, well. Conclusions: It is feasible to dynamically adjust the collimator angle during VMAT treatment delivery to correct for prostate rotations. This technique can safely correct for left-right prostate rotations up to 15°.« less

Dosimetry for Small and Nonstandard Fields

NASA Astrophysics Data System (ADS)

Junell, Stephanie L.

The proposed small and non-standard field dosimetry protocol from the joint International Atomic Energy Agency (IAEA) and American Association of Physicist in Medicine working group introduces new reference field conditions for ionization chamber based reference dosimetry. Absorbed dose beam quality conversion factors (kQ factors) corresponding to this formalism were determined for three different models of ionization chambers: a Farmer-type ionization chamber, a thimble ionization chamber, and a small volume ionization chamber. Beam quality correction factor measurements were made in a specially developed cylindrical polymethyl methacrylate (PMMA) phantom and a water phantom using thermoluminescent dosimeters (TLDs) and alanine dosimeters to determine dose to water. The TLD system for absorbed dose to water determination in high energy photon and electron beams was fully characterized as part of this dissertation. The behavior of the beam quality correction factor was observed as it transfers the calibration coefficient from the University of Wisconsin Accredited Dosimetry Calibration Laboratory (UWADCL) 60Co reference beam to the small field calibration conditions of the small field formalism. TLD-determined beam quality correction factors for the calibration conditions investigated ranged from 0.97 to 1.30 and had associated standard deviations from 1% to 3%. The alanine-determined beam quality correction factors ranged from 0.996 to 1.293. Volume averaging effects were observed with the Farmer-type ionization chamber in the small static field conditions. The proposed small and non-standard field dosimetry protocols new composite-field reference condition demonstrated its potential to reduce or remove ionization chamber volume dependancies, but the measured beam quality correction factors were not equal to the standard CoP's kQ, indicating a change in beam quality in the small and non-standard field dosimetry protocols new composite-field reference condition relative to the standard broad beam reference conditions. The TLD- and alanine-determined beam quality correction factors in the composite-field reference conditions were approximately 3% greater and differed by more than one standard deviation from the published TG-51 kQ values for all three chambers.

SeaWiFS technical report series. Volume 31: Stray light in the SeaWiFS radiometer

NASA Technical Reports Server (NTRS)

Hooker, Stanford B. (Editor); Firestone, Elaine R. (Editor); Acker, James G. (Editor); Barnes, Robert A.; Holmes, Alan W.; Esaias, Wayne E.

1995-01-01

Some of the measurements from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) will not be useful as ocean measurements. For the ocean data set, there are procedures in place to mask the SeaWiFS measurements of clouds and ice. Land measurements will also be masked using a geographic technique based on each measurment's latitude and longitude. Each of these masks involves a source of light much brighter than the ocean. Because of stray light in the SeaWiFS radiometer, light from these bright sources can contaminate ocean measurements located a variable number of pixels away from a bright source. In this document, the sources of stray light in the sensor are examined, and a method is developed for masking measurements near bright targets for stray light effects. In addition, a procedure is proposed for reducing the effects of stray light in the flight data from SeaWiFS. This correction can also reduce the number of pixels masked for stray light. Without these corrections, local area scenes must be masked 10 pixels before and after bright targets in the along-scan direction. The addition of these corrections reduces the along-scan masks to four pixels before and after bright sources. In the along-track direction, the flight data are not corrected, and are masked two pixels before and after. Laboratory measurements have shown that stray light within the instrument changes in a direct ratio to the intensity of the bright source. The measurements have also shown that none of the bands show peculiarities in their stray light response. In other words, the instrument's response is uniform from band to band. The along-scan correction is based on each band's response to a 1 pixel wide bright sources. Since these results are based solely on preflight laboratory measurements, their successful implementation requires compliance with two additional criteria. First, since SeaWiFS has a large data volume, the correction and masking procedures must be such that they can be converted into computationally fast algorithms. Second, they must be shown to operate properly on flight data. The laboratory results, and the corrections and masking procedures that derive from them, should be considered as zeroeth order estimates of the effects that will be found on orbit.

Energy response corrections for profile measurements using a combination of different detector types.

PubMed

Wegener, Sonja; Sauer, Otto A

2018-02-01

Different detector properties will heavily affect the results of off-axis measurements outside of radiation fields, where a different energy spectrum is encountered. While a diode detector would show a high spatial resolution, it contains high atomic number elements, which lead to perturbations and energy-dependent response. An ionization chamber, on the other hand, has a much smaller energy dependence, but shows dose averaging over its larger active volume. We suggest a way to obtain spatial energy response corrections of a detector independent of its volume effect for profiles of arbitrary fields by using a combination of two detectors. Measurements were performed at an Elekta Versa HD accelerator equipped with an Agility MLC. Dose profiles of fields between 10 × 4 cm² and 0.6 × 0.6 cm² were recorded several times, first with different small-field detectors (unshielded diode 60012 and stereotactic field detector SFD, microDiamond, EDGE, and PinPoint 31006) and then with a larger volume ionization chamber Semiflex 31010 for different photon beam qualities of 6, 10, and 18 MV. Correction factors for the small-field detectors were obtained from the readings of the respective detector and the ionization chamber using a convolution method. Selected profiles were also recorded on film to enable a comparison. After applying the correction factors to the profiles measured with different detectors, agreement between the detectors and with profiles measured on EBT3 film was improved considerably. Differences in the full width half maximum obtained with the detectors and the film typically decreased by a factor of two. Off-axis correction factors outside of a 10 × 1 cm² field ranged from about 1.3 for the EDGE diode about 10 mm from the field edge to 0.7 for the PinPoint 31006 25 mm from the field edge. The microDiamond required corrections comparable in size to the Si-diodes and even exceeded the values in the tail region of the field. The SFD was found to require the smallest correction. The corrections typically became larger for higher energies and for smaller field sizes. With a combination of two detectors, experimentally derived correction factors can be obtained. Application of those factors leads to improved agreement between the measured profiles and those recorded on EBT3 film. The results also complement so far only Monte Carlo-simulated values for the off-axis response of different detectors. © 2017 American Association of Physicists in Medicine.

What approach to brain partial volume correction is best for PET/MRI?

NASA Astrophysics Data System (ADS)

Hutton, B. F.; Thomas, B. A.; Erlandsson, K.; Bousse, A.; Reilhac-Laborde, A.; Kazantsev, D.; Pedemonte, S.; Vunckx, K.; Arridge, S. R.; Ourselin, S.

2013-02-01

Many partial volume correction approaches make use of anatomical information, readily available in PET/MRI systems but it is not clear what approach is best. Seven novel approaches to partial volume correction were evaluated, including several post-reconstruction methods and several reconstruction methods that incorporate anatomical information. These were compared with an MRI-independent approach (reblurred van Cittert ) and uncorrected data. Monte Carlo PET data were generated for activity distributions representing both 18F FDG and amyloid tracer uptake. Post-reconstruction methods provided the best recovery with ideal segmentation but were particularly sensitive to mis-registration. Alternative approaches performed better in maintaining lesion contrast (unseen in MRI) with good noise control. These were also relatively insensitive to mis-registration errors. The choice of method will depend on the specific application and reliability of segmentation and registration algorithms.

Anatomy and aging of the amygdala and hippocampus in autism spectrum disorder: an in vivo magnetic resonance imaging study of Asperger syndrome.

PubMed

Murphy, Clodagh M; Deeley, Q; Daly, E M; Ecker, C; O'Brien, F M; Hallahan, B; Loth, E; Toal, F; Reed, S; Hales, S; Robertson, D M; Craig, M C; Mullins, D; Barker, G J; Lavender, T; Johnston, P; Murphy, K C; Murphy, D G

2012-02-01

It has been proposed that people with autism spectrum disorder (ASD) have abnormal morphometry and development of the amygdala and hippocampus (AH). However, previous reports are inconsistent, perhaps because they included people of different ASD diagnoses, ages, and health. We compared, using magnetic resonance imaging, the in vivo anatomy of the AH in 32 healthy individuals with Asperger syndrome (12-47 years) and 32 healthy controls who did not differ significantly in age or IQ. We measured bulk (gray + white matter) volume of the AH using manual tracing (MEASURE). We first compared the volume of AH between individuals with Asperger syndrome and controls and then investigated age-related differences. We compared differences in anatomy before, and after, correcting for whole brain size. There was no significant between group differences in whole brain volume. However, individuals with Asperger syndrome had a significantly larger raw bulk volume of total (P<0.01), right (P<0.01), and left amygdala (P<0.05); and when corrected for overall brain size, total (P<0.05), and right amygdala (P<0.01). There was a significant group difference in aging of left amygdala; controls, but not individuals with Asperger syndrome, had a significant age-related increase in volume (r = 0.486, P<0.01, and r = 0.007, P = 0.97, z = 1.995). There were no significant group differences in volume or age-related effects in hippocampus. Individuals with Asperger syndrome have significant differences from controls in bulk volume and aging of the amygdala. Copyright © 2011, International Society for Autism Research, Wiley-Liss, Inc.

Molecular Volumes and the Stokes-Einstein Equation

ERIC Educational Resources Information Center

Edward, John T.

1970-01-01

Examines the limitations of the Stokes-Einstein equation as it applies to small solute molecules. Discusses molecular volume determinations by atomic increments, molecular models, molar volumes of solids and liquids, and molal volumes. Presents an empirical correction factor for the equation which applies to molecular radii as small as 2 angstrom…

Accurate computer-aided quantification of left ventricular parameters: experience in 1555 cardiac magnetic resonance studies from the Framingham Heart Study.

PubMed

Hautvast, Gilion L T F; Salton, Carol J; Chuang, Michael L; Breeuwer, Marcel; O'Donnell, Christopher J; Manning, Warren J

2012-05-01

Quantitative analysis of short-axis functional cardiac magnetic resonance images can be performed using automatic contour detection methods. The resulting myocardial contours must be reviewed and possibly corrected, which can be time-consuming, particularly when performed across all cardiac phases. We quantified the impact of manual contour corrections on both analysis time and quantitative measurements obtained from left ventricular short-axis cine images acquired from 1555 participants of the Framingham Heart Study Offspring cohort using computer-aided contour detection methods. The total analysis time for a single case was 7.6 ± 1.7 min for an average of 221 ± 36 myocardial contours per participant. This included 4.8 ± 1.6 min for manual contour correction of 2% of all automatically detected endocardial contours and 8% of all automatically detected epicardial contours. However, the impact of these corrections on global left ventricular parameters was limited, introducing differences of 0.4 ± 4.1 mL for end-diastolic volume, -0.3 ± 2.9 mL for end-systolic volume, 0.7 ± 3.1 mL for stroke volume, and 0.3 ± 1.8% for ejection fraction. We conclude that left ventricular functional parameters can be obtained under 5 min from short-axis functional cardiac magnetic resonance images using automatic contour detection methods. Manual correction more than doubles analysis time, with minimal impact on left ventricular volumes and ejection fraction. Copyright © 2011 Wiley Periodicals, Inc.

Rocksalt or cesium chloride: Investigating the relative stability of the cesium halide structures with random phase approximation based methods

NASA Astrophysics Data System (ADS)

Nepal, Niraj K.; Ruzsinszky, Adrienn; Bates, Jefferson E.

2018-03-01

The ground state structural and energetic properties for rocksalt and cesium chloride phases of the cesium halides were explored using the random phase approximation (RPA) and beyond-RPA methods to benchmark the nonempirical SCAN meta-GGA and its empirical dispersion corrections. The importance of nonadditivity and higher-order multipole moments of dispersion in these systems is discussed. RPA generally predicts the equilibrium volume for these halides within 2.4% of the experimental value, while beyond-RPA methods utilizing the renormalized adiabatic LDA (rALDA) exchange-correlation kernel are typically within 1.8%. The zero-point vibrational energy is small and shows that the stability of these halides is purely due to electronic correlation effects. The rAPBE kernel as a correction to RPA overestimates the equilibrium volume and could not predict the correct phase ordering in the case of cesium chloride, while the rALDA kernel consistently predicted results in agreement with the experiment for all of the halides. However, due to its reasonable accuracy with lower computational cost, SCAN+rVV10 proved to be a good alternative to the RPA-like methods for describing the properties of these ionic solids.

Mass-corrections for the conservative coupling of flow and transport on collocated meshes

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

Waluga, Christian, E-mail: waluga@ma.tum.de; Wohlmuth, Barbara; Rüde, Ulrich

2016-01-15

Buoyancy-driven flow models demand a careful treatment of the mass-balance equation to avoid spurious source and sink terms in the non-linear coupling between flow and transport. In the context of finite-elements, it is therefore commonly proposed to employ sufficiently rich pressure spaces, containing piecewise constant shape functions to obtain local or even strong mass-conservation. In three-dimensional computations, this usually requires nonconforming approaches, special meshes or higher order velocities, which make these schemes prohibitively expensive for some applications and complicate the implementation into legacy code. In this paper, we therefore propose a lean and conservatively coupled scheme based on standard stabilizedmore » linear equal-order finite elements for the Stokes part and vertex-centered finite volumes for the energy equation. We show that in a weak mass-balance it is possible to recover exact conservation properties by a local flux-correction which can be computed efficiently on the control volume boundaries of the transport mesh. We discuss implementation aspects and demonstrate the effectiveness of the flux-correction by different two- and three-dimensional examples which are motivated by geophysical applications.« less

A multifractal approach to space-filling recovery for PET quantification

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

Willaime, Julien M. Y., E-mail: julien.willaime@siemens.com; Aboagye, Eric O.; Tsoumpas, Charalampos

2014-11-01

Purpose: A new image-based methodology is developed for estimating the apparent space-filling properties of an object of interest in PET imaging without need for a robust segmentation step and used to recover accurate estimates of total lesion activity (TLA). Methods: A multifractal approach and the fractal dimension are proposed to recover the apparent space-filling index of a lesion (tumor volume, TV) embedded in nonzero background. A practical implementation is proposed, and the index is subsequently used with mean standardized uptake value (SUV {sub mean}) to correct TLA estimates obtained from approximate lesion contours. The methodology is illustrated on fractal andmore » synthetic objects contaminated by partial volume effects (PVEs), validated on realistic {sup 18}F-fluorodeoxyglucose PET simulations and tested for its robustness using a clinical {sup 18}F-fluorothymidine PET test–retest dataset. Results: TLA estimates were stable for a range of resolutions typical in PET oncology (4–6 mm). By contrast, the space-filling index and intensity estimates were resolution dependent. TLA was generally recovered within 15% of ground truth on postfiltered PET images affected by PVEs. Volumes were recovered within 15% variability in the repeatability study. Results indicated that TLA is a more robust index than other traditional metrics such as SUV {sub mean} or TV measurements across imaging protocols. Conclusions: The fractal procedure reported here is proposed as a simple and effective computational alternative to existing methodologies which require the incorporation of image preprocessing steps (i.e., partial volume correction and automatic segmentation) prior to quantification.« less

Effects of online cone-beam computed tomography with active breath control in determining planning target volume during accelerated partial breast irradiation.

PubMed

Li, Y; Zhong, R; Wang, X; Ai, P; Henderson, F; Chen, N; Luo, F

2017-04-01

To test if active breath control during cone-beam computed tomography (CBCT) could improve planning target volume during accelerated partial breast radiotherapy for breast cancer. Patients who were more than 40 years old, underwent breast-conserving dissection and planned for accelerated partial breast irradiation, and with postoperative staging limited to T1-2 N0 M0, or postoperative staging T2 lesion no larger than 3cm with a negative surgical margin greater than 2mm were enrolled. Patients with lobular carcinoma or extensive ductal carcinoma in situ were excluded. CBCT images were obtained pre-correction, post-correction and post-treatment. Set-up errors were recorded at left-right, anterior-posterior and superior-inferior directions. The differences between these CBCT images, as well as calculated radiation doses, were compared between patients with active breath control or free breathing. Forty patients were enrolled, among them 25 had active breath control. A total of 836 CBCT images were obtained for analysis. CBCT significantly reduced planning target volume. However, active breath control did not show significant benefit in decreasing planning target volume margin and the doses of organ-at-risk when compared to free breathing. CBCT, but not active breath control, could reduce planning target volume during accelerated partial breast irradiation. Copyright © 2017 Société française de radiothérapie oncologique (SFRO). Published by Elsevier SAS. All rights reserved.

A Study on Micropipetting Detection Technology of Automatic Enzyme Immunoassay Analyzer.

PubMed

Shang, Zhiwu; Zhou, Xiangping; Li, Cheng; Tsai, Sang-Bing

2018-04-10

In order to improve the accuracy and reliability of micropipetting, a method of micro-pipette detection and calibration combining the dynamic pressure monitoring in pipetting process and quantitative identification of pipette volume in image processing was proposed. Firstly, the normalized pressure model for the pipetting process was established with the kinematic model of the pipetting operation, and the pressure model is corrected by the experimental method. Through the pipetting process pressure and pressure of the first derivative of real-time monitoring, the use of segmentation of the double threshold method as pipetting fault evaluation criteria, and the pressure sensor data are processed by Kalman filtering, the accuracy of fault diagnosis is improved. When there is a fault, the pipette tip image is collected through the camera, extract the boundary of the liquid region by the background contrast method, and obtain the liquid volume in the tip according to the geometric characteristics of the pipette tip. The pipette deviation feedback to the automatic pipetting module and deviation correction is carried out. The titration test results show that the combination of the segmented pipetting kinematic model of the double threshold method of pressure monitoring, can effectively real-time judgment and classification of the pipette fault. The method of closed-loop adjustment of pipetting volume can effectively improve the accuracy and reliability of the pipetting system.

Real-time fMRI processing with physiological noise correction - Comparison with off-line analysis.

PubMed

Misaki, Masaya; Barzigar, Nafise; Zotev, Vadim; Phillips, Raquel; Cheng, Samuel; Bodurka, Jerzy

2015-12-30

While applications of real-time functional magnetic resonance imaging (rtfMRI) are growing rapidly, there are still limitations in real-time data processing compared to off-line analysis. We developed a proof-of-concept real-time fMRI processing (rtfMRIp) system utilizing a personal computer (PC) with a dedicated graphic processing unit (GPU) to demonstrate that it is now possible to perform intensive whole-brain fMRI data processing in real-time. The rtfMRIp performs slice-timing correction, motion correction, spatial smoothing, signal scaling, and general linear model (GLM) analysis with multiple noise regressors including physiological noise modeled with cardiac (RETROICOR) and respiration volume per time (RVT). The whole-brain data analysis with more than 100,000voxels and more than 250volumes is completed in less than 300ms, much faster than the time required to acquire the fMRI volume. Real-time processing implementation cannot be identical to off-line analysis when time-course information is used, such as in slice-timing correction, signal scaling, and GLM. We verified that reduced slice-timing correction for real-time analysis had comparable output with off-line analysis. The real-time GLM analysis, however, showed over-fitting when the number of sampled volumes was small. Our system implemented real-time RETROICOR and RVT physiological noise corrections for the first time and it is capable of processing these steps on all available data at a given time, without need for recursive algorithms. Comprehensive data processing in rtfMRI is possible with a PC, while the number of samples should be considered in real-time GLM. Copyright © 2015 Elsevier B.V. All rights reserved.

Thermodynamic variables of first-order entropy corrected Lovelock-AdS black holes: P{-}V criticality analysis

NASA Astrophysics Data System (ADS)

Haldar, Amritendu; Biswas, Ritabrata

2018-06-01

We investigate the effect of thermal fluctuations on the thermodynamics of a Lovelock-AdS black hole. Taking the first order logarithmic correction term in entropy we analyze the thermodynamic potentials like Helmholtz free energy, enthalpy and Gibbs free energy. We find that all the thermodynamic potentials are decreasing functions of correction coefficient α . We also examined this correction coefficient must be positive by analysing P{-}V diagram. Further we study the P{-}V criticality and stability and find that presence of logarithmic correction in it is necessary to have critical points and stable phases. When P{-}V criticality appears, we calculate the critical volume V_c, critical pressure P_c and critical temperature T_c using different equations and show that there is no critical point for this black hole without thermal fluctuations. We also study the geometrothermodynamics of this kind of black holes. The Ricci scalar of the Ruppeiner metric is graphically analysed.

Skin Rejuvenation and Volume Enhancement with the Micro Superficial Enhanced Fluid Fat Injection (M-SEFFI) for Skin Aging of the Periocular and Perioral Regions.

PubMed

Gennai, Alessandro; Zambelli, Alessandra; Repaci, Erica; Quarto, Rodolfo; Baldelli, Ilaria; Fraternali, Giulio; Bernardini, Francesco P

2017-01-01

Adipose-derived stromal and stem cells (ADSC) in autologous fat promises regenerative advantages, and injected into the dermal and subdermal layers, enhances rejuvenation and volume. However, extremely superficial fat injection with current techniques is limited. Efficacy and viability evaluation of fat harvested with extremely small side port (0.3 mm) cannulae without further tissue manipulation for the correction of aging/thin skin in the periocular and perioral regions. Micro-superficial enhanced fluid fat injection (M-SEFFI) harvests adipose tissue with a multi-perforated cannula (0.3 mm), and autologous platelet rich plasma (PRP) is added. The tissue is injected into the dermal region of the periocular and perioral zones. Efficacy and viability were evaluated by histological and cell culture analysis. Clinical assessment included retrospective evaluation according to 1 = no effect, 2 = fair effect, 3 = good effect, 4 = excellent effect. Between June 2014 and July 2015, 65 patients (7 men; mean age 49.7 years) were treated with M-SEFFI. No intraoperative complications or visible lumpiness were recorded. Analysis demonstrated mature, viable adipocytes with a strong stromal component. Following PRP addition, there was a greater proliferation noted in the M-SEFFI compared to the SEFFI (0.5 mm). Mean follow-up was 4.1 months. Clinical assessment by surgeons and patients at 1 month was 3.52 and 3.74, and 6 months 3.06 and 2.6 respectively. M-SEFFI is effective and viable for lump free skin rejuvenation and volume enhancement, through the extraction of smoother ADSC rich, autologous fat tissue that does not require further tissue manipulation, to correct skin aging. 4 Therapeutic. © 2016 The American Society for Aesthetic Plastic Surgery, Inc. Reprints and permission: journals.permissions@oup.com.

Intrauterine growth restriction affects the preterm infant's hippocampus.

PubMed

Lodygensky, Gregory A; Seghier, Mohammed L; Warfield, Simon K; Tolsa, Cristina Borradori; Sizonenko, Stephane; Lazeyras, François; Hüppi, Petra S

2008-04-01

The hippocampus is known to be vulnerable to hypoxia, stress, and undernutrition, all likely to be present in fetal intrauterine growth restriction (IUGR). The effect of IUGR in preterm infants on the hippocampus was studied using 3D magnetic resonance imaging at term-equivalent age Thirteen preterm infants born with IUGR after placental insufficiency were compared with 13 infants with normal intrauterine growth age matched for gestational age. The hippocampal structural differences were defined using voxel-based morphometry and manual segmentation. The specific neurobehavioral function was evaluated by the Assessment of Preterm Infants' Behavior at term and at 24 mo of corrected age by a Bayley Scales of Infant and Toddler Development. Voxel-based morphometry detected significant gray matter volume differences in the hippocampus between the two groups. This finding was confirmed by manual segmentation of the hippocampus with a reduction of hippocampal volume after IUGR. The hippocampal volume reduction was further associated with functional behavioral differences at term-equivalent age in all six subdomains of the Assessment of Preterm Infants' Behavior but not at 24 mo of corrected age. We conclude that hippocampal development in IUGR is altered and might result from a combination of maternal corticosteroid hormone exposure, hypoxemia, and micronutrient deficiency.

Fully automatic multi-atlas segmentation of CTA for partial volume correction in cardiac SPECT/CT

NASA Astrophysics Data System (ADS)

Liu, Qingyi; Mohy-ud-Din, Hassan; Boutagy, Nabil E.; Jiang, Mingyan; Ren, Silin; Stendahl, John C.; Sinusas, Albert J.; Liu, Chi

2017-05-01

Anatomical-based partial volume correction (PVC) has been shown to improve image quality and quantitative accuracy in cardiac SPECT/CT. However, this method requires manual segmentation of various organs from contrast-enhanced computed tomography angiography (CTA) data. In order to achieve fully automatic CTA segmentation for clinical translation, we investigated the most common multi-atlas segmentation methods. We also modified the multi-atlas segmentation method by introducing a novel label fusion algorithm for multiple organ segmentation to eliminate overlap and gap voxels. To evaluate our proposed automatic segmentation, eight canine 99mTc-labeled red blood cell SPECT/CT datasets that incorporated PVC were analyzed, using the leave-one-out approach. The Dice similarity coefficient of each organ was computed. Compared to the conventional label fusion method, our proposed label fusion method effectively eliminated gaps and overlaps and improved the CTA segmentation accuracy. The anatomical-based PVC of cardiac SPECT images with automatic multi-atlas segmentation provided consistent image quality and quantitative estimation of intramyocardial blood volume, as compared to those derived using manual segmentation. In conclusion, our proposed automatic multi-atlas segmentation method of CTAs is feasible, practical, and facilitates anatomical-based PVC of cardiac SPECT/CT images.

Methods to control phase inversions and enhance mass transfer in liquid-liquid dispersions

DOEpatents

Tsouris, Constantinos; Dong, Junhang

2002-01-01

The present invention is directed to the effects of applied electric fields on liquid-liquid dispersions. In general, the present invention is directed to the control of phase inversions in liquid-liquid dispersions. Because of polarization and deformation effects, coalescence of aqueous drops is facilitated by the application of electric fields. As a result, with an increase in the applied voltage, the ambivalence region is narrowed and shifted toward higher volume fractions of the dispersed phase. This permits the invention to be used to ensure that the aqueous phase remains continuous, even at a high volume fraction of the organic phase. Additionally, the volume fraction of the organic phase may be increased without causing phase inversion, and may be used to correct a phase inversion which has already occurred. Finally, the invention may be used to enhance mass transfer rates from one phase to another through the use of phase inversions.

An Allometric Analysis of Sex and Sex Chromosome Dosage Effects on Subcortical Anatomy in Humans

PubMed Central

Clasen, Liv; Giedd, Jay N.; Blumenthal, Jonathan; Lerch, Jason P.; Chakravarty, M. Mallar; Raznahan, Armin

2016-01-01

Structural neuroimaging of humans with typical and atypical sex-chromosome complements has established the marked influence of both Yand X-/Y-chromosome dosage on total brain volume (TBV) and identified potential cortical substrates for the psychiatric phenotypes associated with sex-chromosome aneuploidy (SCA). Here, in a cohort of 354 humans with varying karyotypes (XX, XY, XXX, XXY, XYY, XXYY, XXXXY), we investigate sex and SCA effects on subcortical size and shape; focusing on the striatum, pallidum and thalamus. We find large effect-size differences in the volume and shape of all three structures as a function of sex and SCA. We correct for TBV effects with a novel allometric method harnessing normative scaling rules for subcortical size and shape in humans, which we derive here for the first time. We show that all three subcortical volumes scale sublinearly with TBV among healthy humans, mirroring known relationships between subcortical volume and TBV among species. Traditional TBV correction methods assume linear scaling and can therefore invert or exaggerate sex and SCA effects on subcortical anatomy. Allometric analysis restricts sex-differences to: (1) greater pallidal volume (PV) in males, and (2) relative caudate head expansion and ventral striatum contraction in females. Allometric analysis of SCA reveals that supernumerary X- and Y-chromosomes both cause disproportionate reductions in PV, and coordinated deformations of striatopallidal shape. Our study provides a novel understanding of sex and sex-chromosome dosage effects on subcortical organization, using an allometric approach that can be generalized to other basic and clinical structural neuroimaging settings. SIGNIFICANCE STATEMENT Sex and sex-chromosome dosage (SCD) are known to modulate human brain size and cortical anatomy, but very little is known regarding their impact on subcortical structures that work with the cortex to subserve a range of behaviors in health and disease. Moreover, regional brain allometry (nonlinear scaling) poses largely unaddressed methodological and theoretical challenges for such research. We build the first set of allometric norms for global and regional subcortical anatomy, and use these to dissect out the complex, distributed and topologically organized patterns of areal contraction and expansion, which characterize sex and SCD effects on subcortical anatomy. Our data inform basic research into the patterning of neuroanatomical variation, and the clinical neuroscience of sex-chromosome aneuploidy. PMID:26911691

Two-compartment modeling of tissue microcirculation revisited.

PubMed

Brix, Gunnar; Salehi Ravesh, Mona; Griebel, Jürgen

2017-05-01

Conventional two-compartment modeling of tissue microcirculation is used for tracer kinetic analysis of dynamic contrast-enhanced (DCE) computed tomography or magnetic resonance imaging studies although it is well-known that the underlying assumption of an instantaneous mixing of the administered contrast agent (CA) in capillaries is far from being realistic. It was thus the aim of the present study to provide theoretical and computational evidence in favor of a conceptually alternative modeling approach that makes it possible to characterize the bias inherent to compartment modeling and, moreover, to approximately correct for it. Starting from a two-region distributed-parameter model that accounts for spatial gradients in CA concentrations within blood-tissue exchange units, a modified lumped two-compartment exchange model was derived. It has the same analytical structure as the conventional two-compartment model, but indicates that the apparent blood flow identifiable from measured DCE data is substantially overestimated, whereas the three other model parameters (i.e., the permeability-surface area product as well as the volume fractions of the plasma and interstitial distribution space) are unbiased. Furthermore, a simple formula was derived to approximately compute a bias-corrected flow from the estimates of the apparent flow and permeability-surface area product obtained by model fitting. To evaluate the accuracy of the proposed modeling and bias correction method, representative noise-free DCE curves were analyzed. They were simulated for 36 microcirculation and four input scenarios by an axially distributed reference model. As analytically proven, the considered two-compartment exchange model is structurally identifiable from tissue residue data. The apparent flow values estimated for the 144 simulated tissue/input scenarios were considerably biased. After bias-correction, the deviations between estimated and actual parameter values were (11.2 ± 6.4) % (vs. (105 ± 21) % without correction) for the flow, (3.6 ± 6.1) % for the permeability-surface area product, (5.8 ± 4.9) % for the vascular volume and (2.5 ± 4.1) % for the interstitial volume; with individual deviations of more than 20% being the exception and just marginal. Increasing the duration of CA administration only had a statistically significant but opposite effect on the accuracy of the estimated flow (declined) and intravascular volume (improved). Physiologically well-defined tissue parameters are structurally identifiable and accurately estimable from DCE data by the conceptually modified two-compartment model in combination with the bias correction. The accuracy of the bias-corrected flow is nearly comparable to that of the three other (theoretically unbiased) model parameters. As compared to conventional two-compartment modeling, this feature constitutes a major advantage for tracer kinetic analysis of both preclinical and clinical DCE imaging studies. © 2017 American Association of Physicists in Medicine.

BODY COMPOSITION OF A MILITARY POPULATION FT. CARSON 1963. I. BODY DENSITY, FAT, AND POTASSIUM 40.

DTIC Science & Technology

Body volumes were measured on 97 soldiers between the ages of 17 - 52 years by water displacement volumetry and corrected for respiratory gas by a...Effective ranking of body fat burden of populations was demonstrated by body volumetry and age differences were noted from potassium 40 counting. A

Quantitative estimation of infarct size by simultaneous dual radionuclide single photon emission computed tomography: comparison with peak serum creatine kinase activity

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

Kawaguchi, K.; Sone, T.; Tsuboi, H.

1991-05-01

To test the hypothesis that simultaneous dual energy single photon emission computed tomography (SPECT) with technetium-99m (99mTc) pyrophosphate and thallium-201 (201TI) can provide an accurate estimate of the size of myocardial infarction and to assess the correlation between infarct size and peak serum creatine kinase activity, 165 patients with acute myocardial infarction underwent SPECT 3.2 +/- 1.3 (SD) days after the onset of acute myocardial infarction. In the present study, the difference in the intensity of 99mTc-pyrophosphate accumulation was assumed to be attributable to difference in the volume of infarcted myocardium, and the infarct volume was corrected by the ratiomore » of the myocardial activity to the osseous activity to quantify the intensity of 99mTc-pyrophosphate accumulation. The correlation of measured infarct volume with peak serum creatine kinase activity was significant (r = 0.60, p less than 0.01). There was also a significant linear correlation between the corrected infarct volume and peak serum creatine kinase activity (r = 0.71, p less than 0.01). Subgroup analysis showed a high correlation between corrected volume and peak creatine kinase activity in patients with anterior infarctions (r = 0.75, p less than 0.01) but a poor correlation in patients with inferior or posterior infarctions (r = 0.50, p less than 0.01). In both the early reperfusion and the no reperfusion groups, a good correlation was found between corrected infarct volume and peak serum creatine kinase activity (r = 0.76 and r = 0.76, respectively; p less than 0.01).« less

40 CFR 1065.695 - Data requirements.

Code of Federal Regulations, 2014 CFR

2014-07-01

... restriction. (v) Charge air cooler volume. (vi) Charge air cooler outlet temperature, specified engine.... (iii) “Dry-to-wet” correction. (iv) NMHC, CH4, and contamination correction. (v) NOX humidity...

Publisher Correction: Recent progress and perspectives of space electric propulsion systems based on smart nanomaterials.

PubMed

Levchenko, I; Xu, S; Teel, G; Mariotti, D; Walker, M L R; Keidar, M

2018-04-10

The original PDF version of this Article had an incorrect volume number of '8'; it should have been '9'. This has been corrected in the PDF version of the Article. The HTML version was correct from the time of publication.

Dental artifacts in the head and neck region: implications for Dixon-based attenuation correction in PET/MR.

PubMed

Ladefoged, Claes N; Hansen, Adam E; Keller, Sune H; Fischer, Barbara M; Rasmussen, Jacob H; Law, Ian; Kjær, Andreas; Højgaard, Liselotte; Lauze, Francois; Beyer, Thomas; Andersen, Flemming L

2015-12-01

In the absence of CT or traditional transmission sources in combined clinical positron emission tomography/magnetic resonance (PET/MR) systems, MR images are used for MR-based attenuation correction (MR-AC). The susceptibility effects due to metal implants challenge MR-AC in the neck region of patients with dental implants. The purpose of this study was to assess the frequency and magnitude of subsequent PET image distortions following MR-AC. A total of 148 PET/MR patients with clear visual signal voids on the attenuation map in the dental region were included in this study. Patients were injected with [(18)F]-FDG, [(11)C]-PiB, [(18)F]-FET, or [(64)Cu]-DOTATATE. The PET/MR data were acquired over a single-bed position of 25.8 cm covering the head and neck. MR-AC was based on either standard MR-ACDIXON or MR-ACINPAINTED where the susceptibility-induced signal voids were substituted with soft tissue information. Our inpainting algorithm delineates the outer contour of signal voids breaching the anatomical volume using the non-attenuation-corrected PET image and classifies the inner air regions based on an aligned template of likely dental artifact areas. The reconstructed PET images were evaluated visually and quantitatively using regions of interests in reference regions. The volume of the artifacts and the computed relative differences in mean and max standardized uptake value (SUV) between the two PET images are reported. The MR-based volume of the susceptibility-induced signal voids on the MR-AC attenuation maps was between 1.6 and 520.8 mL. The corresponding/resulting bias of the reconstructed tracer distribution was localized mainly in the area of the signal void. The mean and maximum SUVs averaged across all patients increased after inpainting by 52% (± 11%) and 28% (± 11%), respectively, in the corrected region. SUV underestimation decreased with the distance to the signal void and correlated with the volume of the susceptibility artifact on the MR-AC attenuation map. Metallic dental work may cause severe MR signal voids. The resulting PET/MR artifacts may exceed the actual volume of the dental fillings. The subsequent bias in PET is severe in regions in and near the signal voids and may affect the conspicuity of lesions in the mandibular region.

SU-F-T-490: Separating Effects Influencing Detector Response in Small MV Photon Fields

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

Wegener, S; Sauer, O

2016-06-15

Purpose: Different detector properties influence their responses especially in field sizes below the lateral electron range. Due to the finite active volume, the detector density and electron perturbation at other structural parts, the response factor is in general field size dependent. We aimed to visualize and separate the main effects contributing to detector behavior for a variety of detector types. This was achieved in an experimental setup, shielding the field center. Thus, effects caused by scattered radiation could be examined separately. Methods: Signal ratios for field sizes down to 8 mm (SSD 90 cm, water depth 10 cm) of amore » 6MV beam from a Siemens Primus LINAC were recorded with several detectors: PTW microDiamond and PinPoint ionization chamber, shielded diodes (PTW P-60008, IBA PFD and SNC Edge) and unshielded diodes (PTW E-60012 and IBA SFD). Measurements were carried out in open fields and with an aluminum pole of 4 mm diameter as a central block. The geometric volume effect was calculated from profiles obtained with Gafchromic EBT3 film, evaluated using FilmQA Pro software (Ashland, USA). Results: Volume corrections were 1.7% at maximum. After correction, in small open fields, unshielded diodes showed a lower response than the diamond, i.e. diamond detector over-response seems to be higher than that for unshielded diodes. Beneath the block, this behavior was amplified by a factor of 2. For the shielded diodes, the overresponse for small open fields could be confirmed. However their lateral response behavior was strongly type dependent, e.g. the signal ratio dropped from 1.02 to 0.98 for the P-60008 diode. Conclusion: The lateral detector response was experimentally examined. Detector volume and density alone do not fully account for the field size dependence of detector response. Detector construction details play a major role, especially for shielded diodes.« less

Elevated Gray Matter Volume of the Emotional Cerebellum in Women with Premenstrual Dysphoric Disorder Disorder

PubMed Central

Berman, Steven M.; London, Edythe D.; Morgan, Melinda; Rapkin, Andrea J.

2012-01-01

OBJECTIVE Premenstrual dysphoric disorder (PMDD) is characterized by severe, negative mood symptoms during the luteal phase of each menstrual cycle. We recently reported that women with PMDD show a greater increase in relative glucose metabolism in the posterior cerebellum from the follicular to the luteal phase, as compared with healthy women, and that the phase-related increase is proportional to PMDD symptom severity. We extended this work with a study of brain structure in PMDD. METHODS High-resolution magnetic resonance imaging (MRI) scans were obtained from 12 women with PMDD and 13 healthy control subjects (whole-brain volume-corrected p<.05). Voxel-based morphometry was used to assess group differences in cerebral grey-matter volume (GMV), using a statistical criterion of p<.05, correcting for multiple comparisons in the whole-brain volume. RESULTS PMDD subjects had greater GMV than controls in the posterior cerebellum but not in any other brain area. Age was negatively correlated with GMV within this region in healthy women, but not in women with PMDD. The group difference in GMV was significant for women over age 30 (p=.0002) but not younger participants (p>.1). CONCLUSIONS PMDD appears to be associated with reduced age-related loss in posterior cerebellar GMV. Although the mechanism underlying this finding is unclear, cumulative effects of symptom-related cerebellar activity may be involved. PMID:22868063

Validation of Student and Parent Reported Data on the Basic Grant Application Form: Corrections Analysis Study. Final Report, Volume 4.

ERIC Educational Resources Information Center

Vogel, Ronald J.

A study was conducted in 1976 of applicants who submitted corrections or amendments to their Student Eligibility Reports (SERs) for the Basic Educational Opportunity Grant (BEOG) Program. The objective was to review the applications corrections process and to determine factors linked to applicants' use of correction procedures. Attention was…

Comparison of epicardial adipose tissue radiodensity threshold between contrast and non-contrast enhanced computed tomography scans: A cohort study of derivation and validation.

PubMed

Xu, Lingyu; Xu, Yuancheng; Coulden, Richard; Sonnex, Emer; Hrybouski, Stanislau; Paterson, Ian; Butler, Craig

2018-05-11

Epicardial adipose tissue (EAT) volume derived from contrast enhanced (CE) computed tomography (CT) scans is not well validated. We aim to establish a reliable threshold to accurately quantify EAT volume from CE datasets. We analyzed EAT volume on paired non-contrast (NC) and CE datasets from 25 patients to derive appropriate Hounsfield (HU) cutpoints to equalize two EAT volume estimates. The gold standard threshold (-190HU, -30HU) was used to assess EAT volume on NC datasets. For CE datasets, EAT volumes were estimated using three previously reported thresholds: (-190HU, -30HU), (-190HU, -15HU), (-175HU, -15HU) and were analyzed by a semi-automated 3D Fat analysis software. Subsequently, we applied a threshold correction to (-190HU, -30HU) based on mean differences in radiodensity between NC and CE images (ΔEATrd = CE radiodensity - NC radiodensity). We then validated our findings on EAT threshold in 21 additional patients with paired CT datasets. EAT volume from CE datasets using previously published thresholds consistently underestimated EAT volume from NC dataset standard by a magnitude of 8.2%-19.1%. Using our corrected threshold (-190HU, -3HU) in CE datasets yielded statistically identical EAT volume to NC EAT volume in the validation cohort (186.1 ± 80.3 vs. 185.5 ± 80.1 cm 3 , Δ = 0.6 cm 3 , 0.3%, p = 0.374). Estimating EAT volume from contrast enhanced CT scans using a corrected threshold of -190HU, -3HU provided excellent agreement with EAT volume from non-contrast CT scans using a standard threshold of -190HU, -30HU. Copyright © 2018. Published by Elsevier B.V.

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

Staring, M., E-mail: m.staring@lumc.nl; Bakker, M. E.; Shamonin, D. P.

Purpose: Whole lung densitometry on chest CT images is an accepted method for measuring tissue destruction in patients with pulmonary emphysema in clinical trials. Progression measurement is required for evaluation of change in health condition and the effect of drug treatment. Information about the location of emphysema progression within the lung may be important for the correct interpretation of drug efficacy, or for determining a treatment plan. The purpose of this study is therefore to develop and validate methods that enable the local measurement of lung density changes, which requires proper modeling of the effect of respiration on density. Methods:more » Four methods, all based on registration of baseline and follow-up chest CT scans, are compared. The first naïve method subtracts registered images. The second employs the so-called dry sponge model, where volume correction is performed using the determinant of the Jacobian of the transformation. The third and the fourth introduce a novel adaptation of the dry sponge model that circumvents its constant-mass assumption, which is shown to be invalid. The latter two methods require a third CT scan at a different inspiration level to estimate the patient-specific density-volume slope, where one method employs a global and the other a local slope. The methods were validated on CT scans of a phantom mimicking the lung, where mass and volume could be controlled. In addition, validation was performed on data of 21 patients with pulmonary emphysema. Results: The image registration method was optimized leaving a registration error below half the slice increment (median 1.0 mm). The phantom study showed that the locally adapted slope model most accurately measured local progression. The systematic error in estimating progression, as measured on the phantom data, was below 2 gr/l for a 70 ml (6%) volume difference, and 5 gr/l for a 210 ml (19%) difference, if volume correction was applied. On the patient data an underlying linearity assumption relating lung volume change with density change was shown to hold (fitR{sup 2} = 0.94), and globalized versions of the local models are consistent with global results (R{sup 2} of 0.865 and 0.882 for the two adapted slope models, respectively). Conclusions: In conclusion, image matching and subsequent analysis of differences according to the proposed lung models (i) has good local registration accuracy on patient data, (ii) effectively eliminates a dependency on inspiration level at acquisition time, (iii) accurately predicts progression in phantom data, and (iv) is reasonably consistent with global results in patient data. It is therefore a potential future tool for assessing local emphysema progression in drug evaluation trials and in clinical practice.« less

Towards local progression estimation of pulmonary emphysema using CT.

PubMed

Staring, M; Bakker, M E; Stolk, J; Shamonin, D P; Reiber, J H C; Stoel, B C

2014-02-01

Whole lung densitometry on chest CT images is an accepted method for measuring tissue destruction in patients with pulmonary emphysema in clinical trials. Progression measurement is required for evaluation of change in health condition and the effect of drug treatment. Information about the location of emphysema progression within the lung may be important for the correct interpretation of drug efficacy, or for determining a treatment plan. The purpose of this study is therefore to develop and validate methods that enable the local measurement of lung density changes, which requires proper modeling of the effect of respiration on density. Four methods, all based on registration of baseline and follow-up chest CT scans, are compared. The first naïve method subtracts registered images. The second employs the so-called dry sponge model, where volume correction is performed using the determinant of the Jacobian of the transformation. The third and the fourth introduce a novel adaptation of the dry sponge model that circumvents its constant-mass assumption, which is shown to be invalid. The latter two methods require a third CT scan at a different inspiration level to estimate the patient-specific density-volume slope, where one method employs a global and the other a local slope. The methods were validated on CT scans of a phantom mimicking the lung, where mass and volume could be controlled. In addition, validation was performed on data of 21 patients with pulmonary emphysema. The image registration method was optimized leaving a registration error below half the slice increment (median 1.0 mm). The phantom study showed that the locally adapted slope model most accurately measured local progression. The systematic error in estimating progression, as measured on the phantom data, was below 2 gr/l for a 70 ml (6%) volume difference, and 5 gr/l for a 210 ml (19%) difference, if volume correction was applied. On the patient data an underlying linearity assumption relating lung volume change with density change was shown to hold (fitR(2) = 0.94), and globalized versions of the local models are consistent with global results (R(2) of 0.865 and 0.882 for the two adapted slope models, respectively). In conclusion, image matching and subsequent analysis of differences according to the proposed lung models (i) has good local registration accuracy on patient data, (ii) effectively eliminates a dependency on inspiration level at acquisition time, (iii) accurately predicts progression in phantom data, and (iv) is reasonably consistent with global results in patient data. It is therefore a potential future tool for assessing local emphysema progression in drug evaluation trials and in clinical practice.

On the radiobiological impact of metal artifacts in head-and-neck IMRT in terms of tumor control probability (TCP) and normal tissue complication probability (NTCP).

PubMed

Kim, Yusung; Tomé, Wolfgang A

2007-11-01

To investigate the effects of distorted head-and-neck (H&N) intensity-modulated radiation therapy (IMRT) dose distributions (hot and cold spots) on normal tissue complication probability (NTCP) and tumor control probability (TCP) due to dental-metal artifacts. Five patients' IMRT treatment plans have been analyzed, employing five different planning image data-sets: (a) uncorrected (UC); (b) homogeneous uncorrected (HUC); (c) sinogram completion corrected (SCC); (d) minimum-value-corrected (MVC); and (e) streak-artifact-reduction including minimum-value-correction (SAR-MVC), which has been taken as the reference data-set. The effects on NTCP and TCP were evaluated using the Lyman-NTCP model and the Logistic-TCP model, respectively. When compared to the predicted NTCP obtained using the reference data-set, the treatment plan based on the original CT data-set (UC) yielded an increase in NTCP of 3.2 and 2.0% for the spared parotid gland and the spinal cord, respectively. While for the treatment plans based on the MVC CT data-set the NTCP increased by a 1.1% and a 0.1% for the spared parotid glands and the spinal cord, respectively. In addition, the MVC correction method showed a reduction in TCP for target volumes (MVC: delta TCP = -0.6% vs. UC: delta TCP = -1.9%) with respect to that of the reference CT data-set. Our results indicate that the presence of dental-metal-artifacts in H&N planning CT data-sets has an impact on the estimates of TCP and NTCP. In particular dental-metal-artifacts lead to an increase in NTCP for the spared parotid glands and a slight decrease in TCP for target volumes.

Brain extraction in partial volumes T2*@7T by using a quasi-anatomic segmentation with bias field correction.

PubMed

Valente, João; Vieira, Pedro M; Couto, Carlos; Lima, Carlos S

2018-02-01

Poor brain extraction in Magnetic Resonance Imaging (MRI) has negative consequences in several types of brain post-extraction such as tissue segmentation and related statistical measures or pattern recognition algorithms. Current state of the art algorithms for brain extraction work on weighted T1 and T2, being not adequate for non-whole brain images such as the case of T2*FLASH@7T partial volumes. This paper proposes two new methods that work directly in T2*FLASH@7T partial volumes. The first is an improvement of the semi-automatic threshold-with-morphology approach adapted to incomplete volumes. The second method uses an improved version of a current implementation of the fuzzy c-means algorithm with bias correction for brain segmentation. Under high inhomogeneity conditions the performance of the first method degrades, requiring user intervention which is unacceptable. The second method performed well for all volumes, being entirely automatic. State of the art algorithms for brain extraction are mainly semi-automatic, requiring a correct initialization by the user and knowledge of the software. These methods can't deal with partial volumes and/or need information from atlas which is not available in T2*FLASH@7T. Also, combined volumes suffer from manipulations such as re-sampling which deteriorates significantly voxel intensity structures making segmentation tasks difficult. The proposed method can overcome all these difficulties, reaching good results for brain extraction using only T2*FLASH@7T volumes. The development of this work will lead to an improvement of automatic brain lesions segmentation in T2*FLASH@7T volumes, becoming more important when lesions such as cortical Multiple-Sclerosis need to be detected. Copyright © 2017 Elsevier B.V. All rights reserved.

PETPVC: a toolbox for performing partial volume correction techniques in positron emission tomography

NASA Astrophysics Data System (ADS)

Thomas, Benjamin A.; Cuplov, Vesna; Bousse, Alexandre; Mendes, Adriana; Thielemans, Kris; Hutton, Brian F.; Erlandsson, Kjell

2016-11-01

Positron emission tomography (PET) images are degraded by a phenomenon known as the partial volume effect (PVE). Approaches have been developed to reduce PVEs, typically through the utilisation of structural information provided by other imaging modalities such as MRI or CT. These methods, known as partial volume correction (PVC) techniques, reduce PVEs by compensating for the effects of the scanner resolution, thereby improving the quantitative accuracy. The PETPVC toolbox described in this paper comprises a suite of methods, both classic and more recent approaches, for the purposes of applying PVC to PET data. Eight core PVC techniques are available. These core methods can be combined to create a total of 22 different PVC techniques. Simulated brain PET data are used to demonstrate the utility of toolbox in idealised conditions, the effects of applying PVC with mismatched point-spread function (PSF) estimates and the potential of novel hybrid PVC methods to improve the quantification of lesions. All anatomy-based PVC techniques achieve complete recovery of the PET signal in cortical grey matter (GM) when performed in idealised conditions. Applying deconvolution-based approaches results in incomplete recovery due to premature termination of the iterative process. PVC techniques are sensitive to PSF mismatch, causing a bias of up to 16.7% in GM recovery when over-estimating the PSF by 3 mm. The recovery of both GM and a simulated lesion was improved by combining two PVC techniques together. The PETPVC toolbox has been written in C++, supports Windows, Mac and Linux operating systems, is open-source and publicly available.

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

PubMed

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

2014-01-01

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 1.10Gy (1.8%), 1.35Gy (2.2%), 1.10Gy (1.9%), and 0.56Gy (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 30Gy (lung V5, V10, V20, and V30) 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., V5 and V10) than on the dosimetric parameters related to the PTV and other OARs. © 2013 Published by American Association of Medical Dosimetrists on behalf of American Association of Medical Dosimetrists.

Unifying framework for multimodal brain MRI segmentation based on Hidden Markov Chains.

PubMed

Bricq, S; Collet, Ch; Armspach, J P

2008-12-01

In the frame of 3D medical imaging, accurate segmentation of multimodal brain MR images is of interest for many brain disorders. However, due to several factors such as noise, imaging artifacts, intrinsic tissue variation and partial volume effects, tissue classification remains a challenging task. In this paper, we present a unifying framework for unsupervised segmentation of multimodal brain MR images including partial volume effect, bias field correction, and information given by a probabilistic atlas. Here-proposed method takes into account neighborhood information using a Hidden Markov Chain (HMC) model. Due to the limited resolution of imaging devices, voxels may be composed of a mixture of different tissue types, this partial volume effect is included to achieve an accurate segmentation of brain tissues. Instead of assigning each voxel to a single tissue class (i.e., hard classification), we compute the relative amount of each pure tissue class in each voxel (mixture estimation). Further, a bias field estimation step is added to the proposed algorithm to correct intensity inhomogeneities. Furthermore, atlas priors were incorporated using probabilistic brain atlas containing prior expectations about the spatial localization of different tissue classes. This atlas is considered as a complementary sensor and the proposed method is extended to multimodal brain MRI without any user-tunable parameter (unsupervised algorithm). To validate this new unifying framework, we present experimental results on both synthetic and real brain images, for which the ground truth is available. Comparison with other often used techniques demonstrates the accuracy and the robustness of this new Markovian segmentation scheme.

Development of a calibration protocol for quantitative imaging for molecular radiotherapy dosimetry

NASA Astrophysics Data System (ADS)

Wevrett, J.; Fenwick, A.; Scuffham, J.; Nisbet, A.

2017-11-01

Within the field of molecular radiotherapy, there is a significant need for standardisation in dosimetry, in both quantitative imaging and dosimetry calculations. Currently, there are a wide range of techniques used by different clinical centres and as a result there is no means to compare patient doses between centres. To help address this need, a 3 year project was funded by the European Metrology Research Programme, and a number of clinical centres were involved in the project. One of the required outcomes of the project was to develop a calibration protocol for three dimensional quantitative imaging of volumes of interest. Two radionuclides were selected as being of particular interest: iodine-131 (131I, used to treat thyroid disorders) and lutetium-177 (177Lu, used to treat neuroendocrine tumours). A small volume of activity within a scatter medium (water), representing a lesion within a patient body, was chosen as the calibration method. To ensure ease of use in clinical centres, an "off-the-shelf" solution was proposed - to avoid the need for in-house manufacturing. The BIODEX elliptical Jaszczak phantom and 16 ml fillable sphere were selected. The protocol was developed for use on SPECT/CT gamma cameras only, where the CT dataset would be used to correct the imaging data for attenuation of the emitted photons within the phantom. The protocol corrects for scatter of emitted photons using the triple energy window correction technique utilised by most clinical systems. A number of clinical systems were tested in the development of this protocol, covering the major manufacturers of gamma camera generally used in Europe. Initial imaging was performed with 131I and 177Lu at a number of clinical centres, but due to time constraints in the project, some acquisitions were performed with 177Lu only. The protocol is relatively simplistic, and does not account for the effects of dead-time in high activity patients, the presence of background activity surrounding volumes of interest or the partial volume effect of imaging lesions smaller than 16 ml. The development of this simple protocol demonstrates that it is possible to produce a standardised quantitative imaging protocol for molecular radiotherapy dosimetry. However, the protocol needs further development to expand it to incorporate other radionuclides, and to account for the effects that have been disregarded in this initial version.

Effectiveness and Safety of Large Gel Particle Hyaluronic Acid With Lidocaine for Correction of Midface Volume Deficit or Contour Deficiency.

PubMed

Weiss, Robert A; Moradi, Amir; Bank, David; Few, Julius; Joseph, John; Dover, Jeffrey; Lin, Xiaoming; Nogueira, Alessandra; Mashburn, Jay

2016-06-01

Aging effects, such as facial flatness, increased tissue laxity, and soft tissue descent and deflation, contribute to midface deficiency. To evaluate whether large gel particle hyaluronic acid with lidocaine (LGP-HAL) is more effective in the treatment of midface deficiencies than no treatment. Subjects with mild to substantial loss of midface fullness were randomized 3:1 to LGP-HAL (Restylane Lyft; Galderma Laboratories, L.P., Fort Worth, TX) or no treatment. Treatment success was defined as at least 1-grade improvement in Medicis Midface Volume Scale (MMVS) on each side of the face at 8 weeks as assessed by a blinded evaluator. Secondary efficacy end points included MMVS score, global aesthetic improvement, and subject satisfaction. Significantly greater percent of subjects achieved treatment success in the LGP-HAL group compared to no treatment at all time points through Month 12 (p < .001). One year after initial treatment, 85% of subjects still had a global aesthetic improvement assessed by the treating investigator. Subject satisfaction demonstrated that LGP-HAL improved the aesthetic appearance of the midface. Most reported adverse events (80%) were mild in severity. The LGP-HAL treatment is well tolerated and provides significant improvement up to 12 months for the correction of midface deficiencies.

Correcting for static shift of magnetotelluric data with airborne electromagnetic measurements: a case study from Rathlin Basin, Northern Ireland

NASA Astrophysics Data System (ADS)

Delhaye, Robert; Rath, Volker; Jones, Alan G.; Muller, Mark R.; Reay, Derek

2017-05-01

Galvanic distortions of magnetotelluric (MT) data, such as the static-shift effect, are a known problem that can lead to incorrect estimation of resistivities and erroneous modelling of geometries with resulting misinterpretation of subsurface electrical resistivity structure. A wide variety of approaches have been proposed to account for these galvanic distortions, some depending on the target area, with varying degrees of success. The natural laboratory for our study is a hydraulically permeable volume of conductive sediment at depth, the internal resistivity structure of which can be used to estimate reservoir viability for geothermal purposes; however, static-shift correction is required in order to ensure robust and precise modelling accuracy.We present here a possible method to employ frequency-domain electromagnetic data in order to correct static-shift effects, illustrated by a case study from Northern Ireland. In our survey area, airborne frequency domain electromagnetic (FDEM) data are regionally available with high spatial density. The spatial distributions of the derived static-shift corrections are analysed and applied to the uncorrected MT data prior to inversion. Two comparative inversion models are derived, one with and one without static-shift corrections, with instructive results. As expected from the one-dimensional analogy of static-shift correction, at shallow model depths, where the structure is controlled by a single local MT site, the correction of static-shift effects leads to vertical scaling of resistivity-thickness products in the model, with the corrected model showing improved correlation to existing borehole wireline resistivity data. In turn, as these vertical scalings are effectively independent of adjacent sites, lateral resistivity distributions are also affected, with up to half a decade of resistivity variation between the models estimated at depths down to 2000 m. Simple estimation of differences in bulk porosity, derived using Archie's Law, between the two models reinforces our conclusion that the suborder of magnitude resistivity contrasts induced by the correction of static shifts correspond to similar contrasts in estimated porosities, and hence, for purposes of reservoir investigation or similar cases requiring accurate absolute resistivity estimates, galvanic distortion correction, especially static-shift correction, is essential.

Inflationary spectra with inverse-volume corrections in loop quantum cosmology and their observational constraints from Planck 2015 data

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

Zhu, Tao; Wang, Anzhong; Wu, Qiang

We first derive the primordial power spectra, spectral indices and runnings of both scalar and tensor perturbations of a flat inflationary universe to the second-order approximations of the slow-roll parameters, in the framework of loop quantum cosmology with the inverse-volume quantum corrections. This represents an extension of our previous work in which the parameter σ was assumed to be an integer, where σ characterizes the quantum corrections and in general can take any of values from the range σ  element of  (0, 6]. Restricting to the first-order approximations of the slow-roll parameters, we find corrections to the results obtained previously inmore » the literature, and point out the causes for such errors. To our best knowledge, these represent the most accurate calculations of scalar and tensor perturbations given so far in the literature. Then, fitting the perturbations to the recently released data by Planck (2015), we obtain the most severe constraints for various values of σ. Using these constraints as our referring point, we discuss whether these quantum gravitational corrections can lead to measurable signatures in the future cosmological observations. We show that, depending on the value of σ, the scale-dependent contributions to the relativistic inflationary spectra due to the inverse-volume corrections could be well within the range of the detectability of the forthcoming generations of experiments, such as the Stage IV experiments.« less

Brain-derived Neurotrophic Factor (BDNF) and gray matter volume in bipolar disorder.

PubMed

Poletti, S; Aggio, V; Hoogenboezem, T A; Ambrée, O; de Wit, H; Wijkhuijs, A J M; Locatelli, C; Colombo, C; Arolt, V; Drexhage, H A; Benedetti, F

2017-02-01

Bipolar Disorder (BD) is a severe psychiatric condition characterized by grey matter (GM) volumes reduction. Neurotrophic factors have been suggested to play a role in the neuroprogressive changes during the illness course. In particular peripheral brain-derived neurotrophic factor (BDNF) has been proposed as a potential biomarker related to disease activity and neuroprogression in BD. The aim of our study was to investigate if serum levels of BDNF are associated with GM volumes in BD patients and healthy controls (HC). We studied 36 inpatients affected by a major depressive episode in course of BD type I and 17 HC. Analysis of variance was performed to investigate the effect of diagnosis on GM volumes in the whole brain. Threshold for significance was P<0.05, Family Wise Error (FWE) corrected for multiple comparisons. All the analyses were controlled for the effect of nuisance covariates known to influence GM volumes, such as age, gender and lithium treatment. BD patients showed significantly higher serum BDNF levels compared with HC. Reduced GM volumes in BD patients compared to HC were observed in several brain areas, encompassing the caudate head, superior temporal gyrus, insula, fusiform gyrus, parahippocampal gyrus, and anterior cingulate cortex. The interaction analysis between BDNF levels and diagnosis showed a significant effect in the middle frontal gyrus. HC reported higher BDNF levels associated with higher GM volumes, whereas no association between BDNF and GM volumes was observed in BD. Our study seems to suggest that although the production of BDNF is increased in BD possibly to prevent and repair neural damage, its effects could be hampered by underlying neuroinflammatory processes interfering with the neurodevelopmental role of BDNF. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Sanity check for NN bound states in lattice QCD with Lüscher's finite volume formula - Disclosing Symptoms of Fake Plateaux -

NASA Astrophysics Data System (ADS)

Aoki, Sinya; Doi, Takumi; Iritani, Takumi

2018-03-01

The sanity check is to rule out certain classes of obviously false results, not to catch every possible error. After reviewing such a sanity check for NN bound states with the Lüscher's finite volume formula [1-3], we give further evidences for the operator dependence of plateaux, a symptom of the fake plateau problem, against the claim [4]. We then present our critical comments on [5] by NPLQCD: (i) Operator dependences of plateaux in NPL2013 [6, 7] exist with the P value of 4-5%. (ii) The volume independence of plateaux in NPL2013 does not prove their correctness. (iii) Effective range expansions (EREs) in NPL2013 violate the physical pole condition. (iv) Their comment is partly based on new data and analysis different from the original ones. (v) Their new ERE does not satisfy the Lüscher's finite volume formula.

Clinical presentation of metabolic alkalosis in an adult patient with cystic fibrosis.

PubMed

Sweetser, Lisel J; Douglas, James A; Riha, Renata L; Bell, Scott C

2005-03-01

In subtropical and tropical climates, dehydration is common in cystic fibrosis patients with respiratory exacerbations. This may lead to a clinical presentation of metabolic alkalosis with associated hyponatraemia and hypochloraemia. An adult cystic fibrosis patient who presented with a severe respiratory exacerbation accompanied by metabolic alkalosis is presented and the effects of volume correction are reported.

Rotational Diffusion Depends on Box Size in Molecular Dynamics Simulations.

PubMed

Linke, Max; Köfinger, Jürgen; Hummer, Gerhard

2018-06-07

We show that the rotational dynamics of proteins and nucleic acids determined from molecular dynamics simulations under periodic boundary conditions suffer from significant finite-size effects. We remove the box-size dependence of the rotational diffusion coefficients by adding a hydrodynamic correction k B T/6 ηV with k B Boltzmann's constant, T the absolute temperature, η the solvent shear viscosity, and V the box volume. We show that this correction accounts for the finite-size dependence of the rotational diffusion coefficients of horse-heart myoglobin and a B-DNA dodecamer in aqueous solution. The resulting hydrodynamic radii are in excellent agreement with experiment.

Stochastic properties of radiation-induced DSB: DSB distributions in large scale chromatin loops, the HPRT gene and within the visible volumes of DNA repair foci.

PubMed

Ponomarev, Artem L; Costes, Sylvain V; Cucinotta, Francis A

2008-11-01

We computed probabilities to have multiple double-strand breaks (DSB), which are produced in DNA on a regional scale, and not in close vicinity, in volumes matching the size of DNA damage foci, of a large chromatin loop, and in the physical volume of DNA containing the HPRT (human hypoxanthine phosphoribosyltransferase) locus. The model is based on a Monte Carlo description of DSB formation by heavy ions in the spatial context of the entire human genome contained within the cell nucleus, as well as at the gene sequence level. We showed that a finite physical volume corresponding to a visible DNA repair focus, believed to be associated with one DSB, can contain multiple DSB due to heavy ion track structure and the DNA supercoiled topography. A corrective distribution was introduced, which was a conditional probability to have excess DSB in a focus volume, given that there was already one present. The corrective distribution was calculated for 19.5 MeV/amu N ions, 3.77 MeV/amu alpha-particles, 1000 MeV/amu Fe ions, and X-rays. The corrected initial DSB yield from the experimental data on DNA repair foci was calculated. The DSB yield based on the corrective function converts the focus yield into the DSB yield, which is comparable with the DSB yield based on the earlier PFGE experiments. The distribution of DSB within the physical limits of the HPRT gene was analyzed by a similar method as well. This corrective procedure shows the applicability of the model and empowers the researcher with a tool to better analyze focus statistics. The model enables researchers to analyze the DSB yield based on focus statistics in real experimental situations that lack one-to-one focus-to-DSB correspondance.

Robust tissue-air volume segmentation of MR images based on the statistics of phase and magnitude: Its applications in the display of susceptibility-weighted imaging of the brain.

PubMed

Du, Yiping P; Jin, Zhaoyang

2009-10-01

To develop a robust algorithm for tissue-air segmentation in magnetic resonance imaging (MRI) using the statistics of phase and magnitude of the images. A multivariate measure based on the statistics of phase and magnitude was constructed for tissue-air volume segmentation. The standard deviation of first-order phase difference and the standard deviation of magnitude were calculated in a 3 x 3 x 3 kernel in the image domain. To improve differentiation accuracy, the uniformity of phase distribution in the kernel was also calculated and linear background phase introduced by field inhomogeneity was corrected. The effectiveness of the proposed volume segmentation technique was compared to a conventional approach that uses the magnitude data alone. The proposed algorithm was shown to be more effective and robust in volume segmentation in both synthetic phantom and susceptibility-weighted images of human brain. Using our proposed volume segmentation method, veins in the peripheral regions of the brain were well depicted in the minimum-intensity projection of the susceptibility-weighted images. Using the additional statistics of phase, tissue-air volume segmentation can be substantially improved compared to that using the statistics of magnitude data alone. (c) 2009 Wiley-Liss, Inc.

77 FR 22788 - Advisory Committee on Breast Cancer in Young Women (ACBCYW); Correction

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-17

... DEPARTMENT OF HEALTH AND HUMAN SERVICES Centers for Disease Control and Prevention Advisory Committee on Breast Cancer in Young Women (ACBCYW); Correction Correction: This notice was published in the Federal Register on March 20, 2012, Volume 77, Number 54, Page 16232. The meeting time and date listed...

Improved scatterer property estimates from ultrasound backscatter for small gate lengths using a gate-edge correction factor

NASA Astrophysics Data System (ADS)

Oelze, Michael L.; O'Brien, William D.

2004-11-01

Backscattered rf signals used to construct conventional ultrasound B-mode images contain frequency-dependent information that can be examined through the backscattered power spectrum. The backscattered power spectrum is found by taking the magnitude squared of the Fourier transform of a gated time segment corresponding to a region in the scattering volume. When a time segment is gated, the edges of the gated regions change the frequency content of the backscattered power spectrum due to truncating of the waveform. Tapered windows, like the Hanning window, and longer gate lengths reduce the relative contribution of the gate-edge effects. A new gate-edge correction factor was developed that partially accounted for the edge effects. The gate-edge correction factor gave more accurate estimates of scatterer properties at small gate lengths compared to conventional windowing functions. The gate-edge correction factor gave estimates of scatterer properties within 5% of actual values at very small gate lengths (less than 5 spatial pulse lengths) in both simulations and from measurements on glass-bead phantoms. While the gate-edge correction factor gave higher accuracy of estimates at smaller gate lengths, the precision of estimates was not improved at small gate lengths over conventional windowing functions. .

Quantitative Evaluation of 2 Scatter-Correction Techniques for 18F-FDG Brain PET/MRI in Regard to MR-Based Attenuation Correction.

PubMed

Teuho, Jarmo; Saunavaara, Virva; Tolvanen, Tuula; Tuokkola, Terhi; Karlsson, Antti; Tuisku, Jouni; Teräs, Mika

2017-10-01

In PET, corrections for photon scatter and attenuation are essential for visual and quantitative consistency. MR attenuation correction (MRAC) is generally conducted by image segmentation and assignment of discrete attenuation coefficients, which offer limited accuracy compared with CT attenuation correction. Potential inaccuracies in MRAC may affect scatter correction, because the attenuation image (μ-map) is used in single scatter simulation (SSS) to calculate the scatter estimate. We assessed the impact of MRAC to scatter correction using 2 scatter-correction techniques and 3 μ-maps for MRAC. Methods: The tail-fitted SSS (TF-SSS) and a Monte Carlo-based single scatter simulation (MC-SSS) algorithm implementations on the Philips Ingenuity TF PET/MR were used with 1 CT-based and 2 MR-based μ-maps. Data from 7 subjects were used in the clinical evaluation, and a phantom study using an anatomic brain phantom was conducted. Scatter-correction sinograms were evaluated for each scatter correction method and μ-map. Absolute image quantification was investigated with the phantom data. Quantitative assessment of PET images was performed by volume-of-interest and ratio image analysis. Results: MRAC did not result in large differences in scatter algorithm performance, especially with TF-SSS. Scatter sinograms and scatter fractions did not reveal large differences regardless of the μ-map used. TF-SSS showed slightly higher absolute quantification. The differences in volume-of-interest analysis between TF-SSS and MC-SSS were 3% at maximum in the phantom and 4% in the patient study. Both algorithms showed excellent correlation with each other with no visual differences between PET images. MC-SSS showed a slight dependency on the μ-map used, with a difference of 2% on average and 4% at maximum when a μ-map without bone was used. Conclusion: The effect of different MR-based μ-maps on the performance of scatter correction was minimal in non-time-of-flight 18 F-FDG PET/MR brain imaging. The SSS algorithm was not affected significantly by MRAC. The performance of the MC-SSS algorithm is comparable but not superior to TF-SSS, warranting further investigations of algorithm optimization and performance with different radiotracers and time-of-flight imaging. © 2017 by the Society of Nuclear Medicine and Molecular Imaging.

Measurement of Crystalline Lens Volume During Accommodation in a Lens Stretcher.

PubMed

Marussich, Lauren; Manns, Fabrice; Nankivil, Derek; Maceo Heilman, Bianca; Yao, Yue; Arrieta-Quintero, Esdras; Ho, Arthur; Augusteyn, Robert; Parel, Jean-Marie

2015-07-01

To determine if the lens volume changes during accommodation. The study used data acquired on 36 cynomolgus monkey lenses that were stretched in a stepwise fashion to simulate disaccommodation. At each step, stretching force and dioptric power were measured and a cross-sectional image of the lens was acquired using an optical coherence tomography system. Images were corrected for refractive distortions and lens volume was calculated assuming rotational symmetry. The average change in lens volume was calculated and the relation between volume change and power change, and between volume change and stretching force, were quantified. Linear regressions of volume-power and volume-force plots were calculated. The mean (± SD) volume in the unstretched (accommodated) state was 97 ± 8 mm3. On average, there was a small but statistically significant (P = 0.002) increase in measured lens volume with stretching. The mean change in lens volume was +0.8 ± 1.3 mm3. The mean volume-power and volume-load slopes were -0.018 ± 0.058 mm3/D and +0.16 ± 0.40 mm3/g. Lens volume remains effectively constant during accommodation, with changes that are less than 1% on average. This result supports a hypothesis that the change in lens shape with accommodation is accompanied by a redistribution of tissue within the capsular bag without significant compression of the lens contents or fluid exchange through the capsule.

Gray Matter Features of Reading Disability: A Combined Meta-Analytic and Direct Analysis Approach1234

PubMed Central

Berninger, Virginia W.; Gebregziabher, Mulugeta; Tsu, Loretta

2016-01-01

Abstract Meta-analysis of voxel-based morphometry dyslexia studies and direct analysis of 293 reading disability and control cases from six different research sites were performed to characterize defining gray matter features of reading disability. These analyses demonstrated consistently lower gray matter volume in left posterior superior temporal sulcus/middle temporal gyrus regions and left orbitofrontal gyrus/pars orbitalis regions. Gray matter volume within both of these regions significantly predicted individual variation in reading comprehension after correcting for multiple comparisons. These regional gray matter differences were observed across published studies and in the multisite dataset after controlling for potential age and gender effects, and despite increased anatomical variance in the reading disability group, but were not significant after controlling for total gray matter volume. Thus, the orbitofrontal and posterior superior temporal sulcus gray matter findings are relatively reliable effects that appear to be dependent on cases with low total gray matter volume. The results are considered in the context of genetics studies linking orbitofrontal and superior temporal sulcus regions to alleles that confer risk for reading disability. PMID:26835509

Cost-Effectiveness of Flight Simulators for Military Training. Volume 1. Use and Effectiveness of Flight Simulators

DTIC Science & Technology

1977-08-01

favorable. Lack of realism and inability to stimulate the feelings involved in flying are given as the major objections to the simulators. Youngling et...and pitching motion * Subliminal , -hout of banked attitudes during turns. The GAT-2 provides nPvon with 2 degrees of freedom: bank and pitch...small to stimulate the semicircular canals; straight and level flight maintained by successive corrections may be interpreted as gradual turning, due

Recent experience with design and manufacture of cine lenses

NASA Astrophysics Data System (ADS)

Thorpe, Michael D.; Dalzell, Kristen E.

2015-09-01

Modern cine lenses require a high degree of aberration correction over a large and ever expanding image size. At low to medium volume production levels, these highly corrected designs also require a workable tolerance set and compensation scheme for successful manufacture. In this paper we discuss the design and manufacture of cine lenses with reference to current designs both internal and in the patent literature and some experience in design, tolerancing and manufacturing these lenses in medium volume production.

CREPT-MCNP code for efficiency calibration of HPGe detectors with the representative point method.

PubMed

Saegusa, Jun

2008-01-01

The representative point method for the efficiency calibration of volume samples has been previously proposed. For smoothly implementing the method, a calculation code named CREPT-MCNP has been developed. The code estimates the position of a representative point which is intrinsic to each shape of volume sample. The self-absorption correction factors are also given to make correction on the efficiencies measured at the representative point with a standard point source. Features of the CREPT-MCNP code are presented.

Increased gray-matter volume in medication-naive high-functioning children with autism spectrum disorder.

PubMed

Palmen, Saskia J M C; Hulshoff Pol, Hilleke E; Kemner, Chantal; Schnack, Hugo G; Durston, Sarah; Lahuis, Bertine E; Kahn, René S; Van Engeland, Herman

2005-04-01

To establish whether high-functioning children with autism spectrum disorder (ASD) have enlarged brains in later childhood, and if so, whether this enlargement is confined to the gray and/or to the white matter and whether it is global or more prominent in specific brain regions. Brain MRI scans were acquired from 21 medication-naive, high-functioning children with ASD between 7 and 15 years of age and 21 comparison subjects matched for gender, age, IQ, height, weight, handedness, and parental education, but not pubertal status. Patients showed a significant increase of 6% in intracranium, total brain, cerebral gray matter, cerebellum, and of more than 40% in lateral and third ventricles compared to controls. The cortical gray-matter volume was evenly affected in all lobes. After correction for brain volume, ventricular volumes remained significantly larger in patients. High-functioning children with ASD showed a global increase in gray-matter, but not white-matter and cerebellar volume, proportional to the increase in brain volume, and a disproportional increase in ventricular volumes, still present after correction for brain volume. Advanced pubertal development in the patients compared to the age-matched controls may have contributed to the findings reported in the present study.

Novel hyaluronic acid dermal filler: dermal gel extra physical properties and clinical outcomes.

PubMed

Monheit, Gary D; Baumann, Leslie S; Gold, Michael H; Goldberg, David J; Goldman, Mitchel P; Narins, Rhoda S; Bachtell, Nathan; Garcia, Emily; Kablik, Jeffrey; Gershkovich, Julia; Burkholder, David

2010-11-01

Dermal gel extra (DGE) is a new, tightly cross-linked hyaluronic acid (HA)-based dermal filler containing lidocaine engineered to resist gel deformation and degradation. To develop a firmer gel product (DGE) and compare the efficacy and safety of DGE with nonanimal stabilized HA (NASHA) for correction of nasolabial folds (NLFs). DGE physical properties were characterized, and 140 subjects with moderate to deep NLFs were treated with DGE and NASHA in a randomized, multicenter, split-face design study. Efficacy, pain, and satisfaction were measured using appropriate standard instruments. Adverse events were monitored throughout the study. DGE has a higher modulus and a higher gel:fluid ratio than other HA fillers. Similar optimal correction was observed with DGE and NASHA through 36 weeks (9 months). Study subjects required less volume (p<.001) and fewer touch-ups (p=.005) and reported less injection pain (p<.001) with DGE treatment. Most adverse events were mild to moderate skin reactions. DGE is a firm HA gel that required significantly less volume and fewer touch-ups to provide equivalent efficacy to NASHA for NLF correction; both dermal gels were well tolerated. DGE will provide a comfortable and cost-effective dermal filler option for clinicians and patients. © 2010 by the American Society for Dermatologic Surgery, Inc.

[Development of a Striatal and Skull Phantom for Quantitative 123I-FP-CIT SPECT].

PubMed

Ishiguro, Masanobu; Uno, Masaki; Miyazaki, Takuma; Kataoka, Yumi; Toyama, Hiroshi; Ichihara, Takashi

123 Iodine-labelled N-(3-fluoropropyl) -2β-carbomethoxy-3β-(4-iodophenyl) nortropane ( 123 I-FP-CIT) single photon emission computerized tomography (SPECT) images are used for differential diagnosis such as Parkinson's disease (PD). Specific binding ratio (SBR) is affected by scattering and attenuation in SPECT imaging, because gender and age lead to changes in skull density. It is necessary to clarify and correct the influence of the phantom simulating the the skull. The purpose of this study was to develop phantoms that can evaluate scattering and attenuation correction. Skull phantoms were prepared based on the measuring the results of the average computed tomography (CT) value, average skull thickness of 12 males and 16 females. 123 I-FP-CIT SPECT imaging of striatal phantom was performed with these skull phantoms, which reproduced normal and PD. SPECT images, were reconstructed with scattering and attenuation correction. SBR with partial volume effect corrected (SBR act ) and conventional SBR (SBR Bolt ) were measured and compared. The striatum and the skull phantoms along with 123 I-FP-CIT were able to reproduce the normal accumulation and disease state of PD and further those reproduced the influence of skull density on SPECT imaging. The error rate with the true SBR, SBR act was much smaller than SBR Bolt . The effect on SBR could be corrected by scattering and attenuation correction even if the skull density changes with 123 I-FP-CIT on SPECT imaging. The combination of triple energy window method and CT-attenuation correction method would be the best correction method for SBR act .

Reduction of Topographic Effect for Curve Number Estimated from Remotely Sensed Imagery

NASA Astrophysics Data System (ADS)

Zhang, Wen-Yan; Lin, Chao-Yuan

2016-04-01

The Soil Conservation Service Curve Number (SCS-CN) method is commonly used in hydrology to estimate direct runoff volume. The CN is the empirical parameter which corresponding to land use/land cover, hydrologic soil group and antecedent soil moisture condition. In large watersheds with complex topography, satellite remote sensing is the appropriate approach to acquire the land use change information. However, the topographic effect have been usually found in the remotely sensed imageries and resulted in land use classification. This research selected summer and winter scenes of Landsat-5 TM during 2008 to classified land use in Chen-You-Lan Watershed, Taiwan. The b-correction, the empirical topographic correction method, was applied to Landsat-5 TM data. Land use were categorized using K-mean classification into 4 groups i.e. forest, grassland, agriculture and river. Accuracy assessment of image classification was performed with national land use map. The results showed that after topographic correction, the overall accuracy of classification was increased from 68.0% to 74.5%. The average CN estimated from remotely sensed imagery decreased from 48.69 to 45.35 where the average CN estimated from national LULC map was 44.11. Therefore, the topographic correction method was recommended to normalize the topographic effect from the satellite remote sensing data before estimating the CN.

Feasibility and performance of novel software to quantify metabolically active volumes and 3D partial volume corrected SUV and metabolic volumetric products of spinal bone marrow metastases on 18F-FDG-PET/CT.

PubMed

Torigian, Drew A; Lopez, Rosa Fernandez; Alapati, Sridevi; Bodapati, Geetha; Hofheinz, Frank; van den Hoff, Joerg; Saboury, Babak; Alavi, Abass

2011-01-01

Our aim was to assess feasibility and performance of novel semi-automated image analysis software called ROVER to quantify metabolically active volume (MAV), maximum standardized uptake value-maximum (SUV(max)), 3D partial volume corrected mean SUV (cSUV(mean)), and 3D partial volume corrected mean MVP (cMVP(mean)) of spinal bone marrow metastases on fluorine-18 fluorodeoxyglucose-positron emission tomography/computerized tomography ((18)F-FDG-PET/CT). We retrospectively studied 16 subjects with 31 spinal metastases on FDG-PET/CT and MRI. Manual and ROVER determinations of lesional MAV and SUV(max), and repeated ROVER measurements of MAV, SUV(max), cSUV(mean) and cMVP(mean) were made. Bland-Altman and correlation analyses were performed to assess reproducibility and agreement. Our results showed that analyses of repeated ROVER measurements revealed MAV mean difference (D)=-0.03±0.53cc (95% CI(-0.22, 0.16)), lower limit of agreement (LLOA)=-1.07cc, and upper limit of agreement (ULOA)=1.01cc; SUV(max) D=0.00±0.00 with LOAs=0.00; cSUV(mean) D=-0.01±0.39 (95% CI(-0.15, 0.13)), LLOA=-0.76, and ULOA=0.75; cMVP(mean) D=-0.52±4.78cc (95% CI(-2.23, 1.23)), LLOA=-9.89cc, and ULOA=8.86cc. Comparisons between ROVER and manual measurements revealed volume D= -0.39±1.37cc (95% CI (-0.89, 0.11)), LLOA=-3.08cc, and ULOA=2.30cc; SUV(max) D=0.00±0.00 with LOAs=0.00. Mean percent increase in lesional SUV(mean) and MVP(mean) following partial volume correction using ROVER was 84.25±36.00% and 84.45±35.94% , respectively. In conclusion, it is feasible to estimate MAV, SUV(max), cSUV(mean), and cMVP(mean) of spinal bone marrow metastases from (18)F-FDG-PET/CT quickly and easily with good reproducibility via ROVER software. Partial volume correction is imperative, as uncorrected SUV(mean) and MVP(mean) are significantly underestimated, even for large lesions. This novel approach has great potential for practical, accurate, and precise combined structural-functional PET quantification of disease before and after therapeutic intervention.

When structure affects function--the need for partial volume effect correction in functional and resting state magnetic resonance imaging studies.

PubMed

Dukart, Juergen; Bertolino, Alessandro

2014-01-01

Both functional and also more recently resting state magnetic resonance imaging have become established tools to investigate functional brain networks. Most studies use these tools to compare different populations without controlling for potential differences in underlying brain structure which might affect the functional measurements of interest. Here, we adapt a simulation approach combined with evaluation of real resting state magnetic resonance imaging data to investigate the potential impact of partial volume effects on established functional and resting state magnetic resonance imaging analyses. We demonstrate that differences in the underlying structure lead to a significant increase in detected functional differences in both types of analyses. Largest increases in functional differences are observed for highest signal-to-noise ratios and when signal with the lowest amount of partial volume effects is compared to any other partial volume effect constellation. In real data, structural information explains about 25% of within-subject variance observed in degree centrality--an established resting state connectivity measurement. Controlling this measurement for structural information can substantially alter correlational maps obtained in group analyses. Our results question current approaches of evaluating these measurements in diseased population with known structural changes without controlling for potential differences in these measurements.

Casimir effect in rugby-ball type flux compactifications

NASA Astrophysics Data System (ADS)

Elizalde, Emilio; Minamitsuji, Masato; Naylor, Wade

2007-03-01

As a continuation of the work by Minamitsuji, Naylor, and Sasaki [J. High Energy Phys.JHEPFG1029-8479 12 (2006) 07910.1088/1126-6708/2006/12/079], we discuss the Casimir effect for a massless bulk scalar field in a 4D toy model of a 6D warped flux compactification model, to stabilize the volume modulus. The one-loop effective potential for the volume modulus has a form similar to the Coleman-Weinberg potential. The stability of the volume modulus against quantum corrections is related to an appropriate heat kernel coefficient. However, to make any physical predictions after volume stabilization, knowledge of the derivative of the zeta function, ζ'(0) (in a conformally related spacetime) is also required. By adding up the exact mass spectrum using zeta-function regularization, we present a revised analysis of the effective potential. Finally, we discuss some physical implications, especially concerning the degree of the hierarchy between the fundamental energy scales on the branes. For a larger degree of warping our new results are very similar to the ones given by Minamitsuji, Naylor, and Sasaki [J. High Energy Phys.JHEPFG1029-8479 12 (2006) 07910.1088/1126-6708/2006/12/079] and imply a larger hierarchy. In the nonwarped (rugby ball) limit the ratio tends to converge to the same value, independently of the bulk dilaton coupling.

Thermodynamic evaluation of transonic compressor rotors using the finite volume approach

NASA Technical Reports Server (NTRS)

Moore, J.; Nicholson, S.; Moore, J. G.

1985-01-01

Research at NASA Lewis Research Center gave the opportunity to incorporate new control volumes in the Denton 3-D finite-volume time marching code. For duct flows, the new control volumes require no transverse smoothing and this allows calculations with large transverse gradients in properties without significant numerical total pressure losses. Possibilities for improving the Denton code to obtain better distributions of properties through shocks were demonstrated. Much better total pressure distributions through shocks are obtained when the interpolated effective pressure, needed to stabilize the solution procedure, is used to calculate the total pressure. This simple change largely eliminates the undershoot in total pressure down-stream of a shock. Overshoots and undershoots in total pressure can then be further reduced by a factor of 10 by adopting the effective density method, rather than the effective pressure method. Use of a Mach number dependent interpolation scheme for pressure then removes the overshoot in static pressure downstream of a shock. The stability of interpolation schemes used for the calculation of effective density is analyzed and a Mach number dependent scheme is developed, combining the advantages of the correct perfect gas equation for subsonic flow with the stability of 2-point and 3-point interpolation schemes for supersonic flow.

Effects of hypertonic saline (7.5%) on extracellular fluid volumes compared with normal saline (0.9%) and 6% hydroxyethyl starch after aortocoronary bypass graft surgery.

PubMed

Järvelä, K; Koskinen, M; Kaukinen, S; Kööbi, T

2001-04-01

To compare the effects of hypertonic (7.5%) saline (HS), normal (0.9%) saline (NS), and 6% hydroxyethyl starch (HES) on extracellular fluid volumes in the early postoperative period after cardiopulmonary bypass. A prospective, randomized, double-blind study. University teaching hospital. Forty-eight patients scheduled for elective coronary artery bypass graft surgery. Patients were randomly allocated to receive 4 mL/kg of HS, NS, or HES during 30 minutes when volume loading was needed during the postoperative rewarming period in the intensive care unit. Plasma volume was measured using a dilution of iodine-125-labeled human serum albumin. Extracellular water and cardiac output were measured by whole-body impedance cardiography. Plasma volume had increased by 19 +/- 7% in the HS group and by 10 +/- 3% in the NS group (p = 0.001) at the end of the study fluid infusion. After 1-hour follow-up time, the plasma volume increase was greatest (23 +/- 8%) in the group receiving HES (p < 0.001). The increase of extracellular water was greater than the infused volume in the HS and HES groups at the end of the infusion. One-hour diuresis after the study infusion was greater in the HS group (536 +/- 280 mL) than in the NS (267 +/- 154 mL, p = 0.006) and HES groups (311 +/- 238 mL, p = 0.025). The effect of HS on plasma volume was short-lasting, but it stimulated excretion of excess body fluid accumulated during cardiopulmonary bypass and cardiac surgery. HS may be used in situations in which excess free water administration is to be avoided but the intravascular volume needs correction. Copyright 2001 by W.B. Saunders Company

Local respiratory motion correction for PET/CT imaging: Application to lung cancer

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

Lamare, F., E-mail: frederic.lamare@chu-bordeaux.fr; Fernandez, P.; Fayad, H.

Purpose: Despite multiple methodologies already proposed to correct respiratory motion in the whole PET imaging field of view (FOV), such approaches have not found wide acceptance in clinical routine. An alternative can be the local respiratory motion correction (LRMC) of data corresponding to a given volume of interest (VOI: organ or tumor). Advantages of LRMC include the use of a simple motion model, faster execution times, and organ specific motion correction. The purpose of this study was to evaluate the performance of LMRC using various motion models for oncology (lung lesion) applications. Methods: Both simulated (NURBS based 4D cardiac-torso phantom)more » and clinical studies (six patients) were used in the evaluation of the proposed LRMC approach. PET data were acquired in list-mode and synchronized with respiration. The implemented approach consists first in defining a VOI on the reconstructed motion average image. Gated PET images of the VOI are subsequently reconstructed using only lines of response passing through the selected VOI and are used in combination with a center of gravity or an affine/elastic registration algorithm to derive the transformation maps corresponding to the respiration effects. Those are finally integrated in the reconstruction process to produce a motion free image over the lesion regions. Results: Although the center of gravity or affine algorithm achieved similar performance for individual lesion motion correction, the elastic model, applied either locally or to the whole FOV, led to an overall superior performance. The spatial tumor location was altered by 89% and 81% for the elastic model applied locally or to the whole FOV, respectively (compared to 44% and 39% for the center of gravity and affine models, respectively). This resulted in similar associated overall tumor volume changes of 84% and 80%, respectively (compared to 75% and 71% for the center of gravity and affine models, respectively). The application of the nonrigid deformation model in LRMC led to over an order of magnitude gain in computational efficiency of the correction relative to the application of the deformable model to the whole FOV. Conclusions: The results of this study support the use of LMRC as a flexible and efficient correction approach for respiratory motion effects for single lesions in the thoracic area.« less

Anatomical substrates of cognitive and clinical dimensions in first episode schizophrenia.

PubMed

Rigucci, S; Rossi-Espagnet, C; Ferracuti, S; De Carolis, A; Corigliano, V; Carducci, F; Mancinelli, I; Cicone, F; Tatarelli, R; Bozzao, A; Girardi, P; Comparelli, A

2013-10-01

To explore gray (GM) and white matter (WM) abnormalities and the relationships with neuropsychopathology in first-episode schizophrenia (FES). Nineteen patients with first episode of non-affective psychosis and 18 controls underwent a magnetic resonance voxel-based morphometry. Additionally, WM fractional anisotropy (FA) was calculated. For correlative analysis, symptoms and neuropsychological performances were scored by PANSS and by a comprehensive neuropsychological assessment respectively. Patients showed significantly decreased volume of left temporal lobe and disarray of all major WM tracts. Disorganized PANSS factor was inversely related to left cerebellar GM volume (corrected P = 0.03) and to WM FA of the left cerebellum, inferior fronto-occipital fasciculi (IFOF), and inferior longitudinal fasciculi (corrected P < 0.05). PANSS negative factor was inversely related to FA in the IFOF and superior longitudinal fasciculi (corrected P < 0.05). Impairment in facial emotion identification showed associations with temporo-occipital GM volume decrease (corrected P = 0.003) and WM disarray of superior and middle temporal gyri, anterior thalamic radiation, and superior longitudinal fasciculi (corrected P < 0.05). Speed of processing and visual memory correlated with WM abnormalities in fronto-temporal tracts. These results confirm how the structural development of key brain regions is related to neuropsychopathological dysfunction in FES, consistently with a neurodevelopmentally derived misconnection syndrome. © 2012 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Right ventricular remodelling after transcatheter pulmonary valve implantation.

PubMed

Pagourelias, Efstathios D; Daraban, Ana M; Mada, Razvan O; Duchenne, Jürgen; Mirea, Oana; Cools, Bjorn; Heying, Ruth; Boshoff, Derize; Bogaert, Jan; Budts, Werner; Gewillig, Marc; Voigt, Jens-Uwe

2017-09-01

To define the optimal timing for percutaneous pulmonary valve implantation (PPVI) in patients with severe pulmonary regurgitation (PR) after Fallot's Tetralogy (ToF) correction. PPVI among the aforementioned patients is mainly driven by symptoms or by severe right ventricular (RV) dilatation/dysfunction. The optimal timing for PPVI is still disputed. Twenty patients [age 13.9 ± 9.2 years, (range 4.3-44.9), male 70%] with severe PR (≥3 grade) secondary to previous correction of ToF, underwent Melody valve (Medtronic, Minneapolis, MN) implantation, after a pre-stent placement. Full echocardiographic assessment (traditional and deformation analysis) and cardiovascular magnetic resonance evaluation were performed before and at 3 months after the intervention. 'Favorable remodelling' was considered the upper quartile of RV size decrease (>20% in 3 months). After PPVI, indexed RV effective stroke volume increased from 38.4 ± 9.5 to 51.4 ± 10.7 mL/m 2 , (P = 0.005), while RV end-diastolic volume and strain indices decreased (123.1 ± 24.1-101.5 ± 18.3 mL/m 2 , P = 0.005 and -23.5 ± 2.5 to -21 ± 2.5%, P = 0.002, respectively). After inserting pre-PPVI clinical, RV volumetric and deformation parameters in a multiple regression model, only time after last surgical correction causing PR remained as significant regressor of RV remodelling [R 2  = 0.60, beta = 0.387, 95%CI(0.07-0.7), P = 0.019]. Volume reduction and functional improvement were more pronounced in patients treated with PPVI earlier than 7 years after last RV outflow tract (RVOT) correction, reaching close-to-normal values. Early PPVI (<7 years after last RVOT operation) is associated with a more favorable RV reverse remodelling toward normal range and should be considered, before symptoms or RV damage become apparent. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Vibrational and thermodynamic properties of β-HMX: a first-principles investigation.

PubMed

Wu, Zhongqing; Kalia, Rajiv K; Nakano, Aiichiro; Vashishta, Priya

2011-05-28

Thermodynamic properties of β-HMX crystal are investigated using the quasi-harmonic approximation and density functional theory within the local density approximation (LDA), generalized gradient approximation (GGA), and GGA + empirical van der Waals (vdW) correction. It is found that GGA well describes the thermal expansion coefficient and heat capacity but fails to produce correct bulk modulus and equilibrium volume. The vdW correction improves the bulk modulus and volume, but worsens the thermal expansion coefficient and heat capacity. In contrast, LDA describes all thermodynamic properties with reasonable accuracy, and overall is a good exchange-correlation functional for β-HMX molecular crystal. The results also demonstrate significant contributions of phonons to the equation of state. The static calculation of equilibrium volume for β-HMX differs from the room-temperature value incorporating lattice vibrations by over 5%. Therefore, for molecular crystals, it is essential to include phonon contributions when calculated equation of state is compared with experimental data at ambient condition. © 2011 American Institute of Physics

Pressure-Volume-Temperature (PVT) Gauging of an Isothermal Cryogenic Propellant Tank Pressurized with Gaseous Helium

NASA Technical Reports Server (NTRS)

VanDresar, Neil T.; Zimmerli, Gregory A.

2014-01-01

Results are presented for pressure-volume-temperature (PVT) gauging of a liquid oxygen/liquid nitrogen tank pressurized with gaseous helium that was supplied by a high-pressure cryogenic tank simulating a cold helium supply bottle on a spacecraft. The fluid inside the test tank was kept isothermal by frequent operation of a liquid circulation pump and spray system, and the propellant tank was suspended from load cells to obtain a high-accuracy reference standard for the gauging measurements. Liquid quantity gauging errors of less than 2 percent of the tank volume were obtained when quasi-steady-state conditions existed in the propellant and helium supply tanks. Accurate gauging required careful attention to, and corrections for, second-order effects of helium solubility in the liquid propellant plus differences in the propellant/helium composition and temperature in the various plumbing lines attached to the tanks. On the basis of results from a helium solubility test, a model was developed to predict the amount of helium dissolved in the liquid as a function of cumulative pump operation time. Use of this model allowed correction of the basic PVT gauging calculations and attainment of the reported gauging accuracy. This helium solubility model is system specific, but it may be adaptable to other hardware systems.

A new Doppler-echo method to quantify regurgitant volume.

PubMed

Wang, S S; Rubenstein, J J; Goldman, M; Sidd, J J

1992-01-01

An in vitro technique using color flow imaging and continuous wave Doppler was developed to measure the initial regurgitant flow jet diameter and velocity integral to yield the parameters for a volume calculation. Jets were produced by volume-controlled injection through tubes of various diameters (1.3, 1.9, 2.8, and 3.5 mm) to deliver volumes from 1 to 7 ml over 100 to 300 msec at pressures from 40 to 200 mm Hg. One hundred forty-five samples were obtained. Flow jet diameter consistently overestimated tube diameter by 2 mm when injected volume was 1.5 to 7 ml and by 1.5 mm when injected volume was less than 1.5 ml. This offset was stable with various transducers (2.5, 3.5, 5.0 MHz) at normal gain setting (just under noise). Therefore, corrected flow jet diameter (FJD) = FJD - 2 mm, and Doppler volume = corrected flow jet area x velocity integral. A range of injectates from 1.1 to 7 ml generated Doppler volume of 1.0 to 8.2 ml. The relation between Doppler volume (DV) and injected volume (IV) was DV = 1.079 IV - 0.22, r2 = 0.945, p less than 0.01. This relation was not altered by tube diameter. Thus a method combining color flow imaging and continuous wave Doppler provides a reliable and accurate measure of in vitro flow volume.

Correction of 3D rigid body motion in fMRI time series by independent estimation of rotational and translational effects in k-space.

PubMed

Costagli, Mauro; Waggoner, R Allen; Ueno, Kenichi; Tanaka, Keiji; Cheng, Kang

2009-04-15

In functional magnetic resonance imaging (fMRI), even subvoxel motion dramatically corrupts the blood oxygenation level-dependent (BOLD) signal, invalidating the assumption that intensity variation in time is primarily due to neuronal activity. Thus, correction of the subject's head movements is a fundamental step to be performed prior to data analysis. Most motion correction techniques register a series of volumes assuming that rigid body motion, characterized by rotational and translational parameters, occurs. Unlike the most widely used applications for fMRI data processing, which correct motion in the image domain by numerically estimating rotational and translational components simultaneously, the algorithm presented here operates in a three-dimensional k-space, to decouple and correct rotations and translations independently, offering new ways and more flexible procedures to estimate the parameters of interest. We developed an implementation of this method in MATLAB, and tested it on both simulated and experimental data. Its performance was quantified in terms of square differences and center of mass stability across time. Our data show that the algorithm proposed here successfully corrects for rigid-body motion, and its employment in future fMRI studies is feasible and promising.

PET motion correction in context of integrated PET/MR: Current techniques, limitations, and future projections.

PubMed

Gillman, Ashley; Smith, Jye; Thomas, Paul; Rose, Stephen; Dowson, Nicholas

2017-12-01

Patient motion is an important consideration in modern PET image reconstruction. Advances in PET technology mean motion has an increasingly important influence on resulting image quality. Motion-induced artifacts can have adverse effects on clinical outcomes, including missed diagnoses and oversized radiotherapy treatment volumes. This review aims to summarize the wide variety of motion correction techniques available in PET and combined PET/CT and PET/MR, with a focus on the latter. A general framework for the motion correction of PET images is presented, consisting of acquisition, modeling, and correction stages. Methods for measuring, modeling, and correcting motion and associated artifacts, both in literature and commercially available, are presented, and their relative merits are contrasted. Identified limitations of current methods include modeling of aperiodic and/or unpredictable motion, attaining adequate temporal resolution for motion correction in dynamic kinetic modeling acquisitions, and maintaining availability of the MR in PET/MR scans for diagnostic acquisitions. Finally, avenues for future investigation are discussed, with a focus on improvements that could improve PET image quality, and that are practical in the clinical environment. © 2017 American Association of Physicists in Medicine.

Electromagnetic corrections to the hadronic vacuum polarization of the photon within QEDL and QEDM

NASA Astrophysics Data System (ADS)

Bussone, Andrea; Della Morte, Michele; Janowski, Tadeusz

2018-03-01

We compute the leading QED corrections to the hadronic vacuum polarization (HVP) of the photon, relevant for the determination of leptonic anomalous magnetic moments, al. We work in the electroquenched approximation and use dynamical QCD configurations generated by the CLS initiative with two degenerate flavors of nonperturbatively O(a)-improved Wilson fermions. We consider QEDL and QEDM to deal with the finite-volume zero modes. We compare results for the Wilson loops with exact analytical determinations. In addition we make sure that the volumes and photon masses used in QEDM are such that the correct dispersion relation is reproduced by the energy levels extracted from the charged pions two-point functions. Finally we compare results for pion masses and the HVP between QEDL and QEDM. For the vacuum polarization, corrections with respect to the pure QCD case, at fixed pion masses, turn out to be at the percent level.

SU-G-TeP1-03: Beam Quality Correction Factors for Linear Accelerator with and Without Flattening Filter

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

Czarnecki, D; Voigts-Rhetz, P von; Zink, K

2016-06-15

Purpose: The impact of removing the flattening filter on absolute dosimetry based on IAEA’s TPR-398 and AAPM’s TG-51 was investigated in this study using Monte Carlo simulations. Methods: The EGSnrc software package was used for all Monte Carlo simulations performed in this work. Five different ionization chambers and nine linear accelerator heads have been modeled according to technical drawings. To generate a flattening filter free radiation field the flattening filter was replaced by a 2 mm thick aluminum layer. Dose calculation in a water phantom were performed to calculate the beam quality correction factor k{sub Q} as a function ofmore » the beam quality specifiers %dd(10){sub x}, TPR{sub 20,10} and mean photon and electron energies at the point of measurement in photon fields with (WFF) and without flattening filter (FFF). Results: The beam quality correction factor as a function of %dd(10){sub x} differs systematically between FFF and WFF beams for all investigated ionization chambers. The largest difference of 1.8% was observed for the largest investigated Farmer-type ionization chamber with a sensitive volume of 0.69 cm{sup 3}. For ionization chambers with a smaller nominal sensitive volume (0.015 – 0.3 cm{sup 3}) the deviation was less than 0.4% between WFF and FFF beams for %dd(10){sub x} > 62%. The specifier TPR{sub 20,10} revealed only a good correlation between WFF and FFF beams (< 0.3%) for low energies. Conclusion: The results confirm that %dd(10){sub x} is a suitable beam quality specifier for FFF beams with an acceptable bias. The deviation depends on the volume of the ionization chamber. Using %dd(10){sub x} to predict k{sub Q} for a large volume chamber in a FFF photon field may lead to not acceptable errors according to the results of this study. This bias may be caused by the volume effect due to the inhomogeneous photon fields of FFF linear accelerators.« less

Application of 3D Rapid Prototyping Technology in Posterior Corrective Surgery for Lenke 1 Adolescent Idiopathic Scoliosis Patients

PubMed Central

Yang, Mingyuan; Li, Chao; Li, Yanming; Zhao, Yingchuan; Wei, Xianzhao; Zhang, Guoyou; Fan, Jianping; Ni, Haijian; Chen, Ziqiang; Bai, Yushu; Li, Ming

2015-01-01

Abstract A retrospective study to evaluate the effectiveness of 3-dimensional rapid prototyping (3DRP) technology in corrective surgery for Lenke 1 adolescent idiopathic scoliosis (AIS) patients. 3DRP technology has been widely used in medical field; however, no study has been performed on the effectiveness of 3DRP technology in corrective surgery for Lenke 1 AIS patients. Lenke 1 AIS patients who were preparing to undergo posterior corrective surgery from a single center between January 2010 and January 2012 were included in this analysis. Patients were divided into 2 groups. In group A, 3-dimensional (3D) printing technology was used to create subject-specific spine models in the preoperative planning process. Group B underwent posterior corrective surgery as usual (by free hand without image guidance). Perioperative and postoperative clinical outcomes were compared between 2 groups, including operation time, perioperative blood loss, transfusion volume, postoperative hemoglobin (Hb), postoperative complications, and length of hospital stay. Radiological outcomes were also compared, including the assessment of screw placement, postoperative Cobb angle, coronal balance, sagittal vertical axis, thoracic kyphosis, and lumbar lordosis. Subgroup was also performed according to the preoperative Cobb angle: mean Cobb angle <50° and mean Cobb angle >50°. Besides, economic evaluation was also compared between 2 groups. A total of 126 patients were included in this study (group A, 50 and group B, 76). Group A had significantly shorter operation time, significantly less blood loss and transfusion volume, and higher postoperative Hb (all, P < 0.001). However, no significant differences were observed in complication rate, length of hospital stay, and postoperative radiological outcomes between 2 groups (all, P>0.05). There was also no significant difference in misplacement of screws in total populations (16.90% vs 18.82%, P = 0.305), whereas a low misplacement rate of pedicle screws was observed in patients whose mean Cobb angle was >50° (9.15% vs 13.03%, P = 0.02). Besides, using 3DRP increased the economic burden of patients (157,000 ± 9948.85 Ren Min Bi (RMB) vs 152,500 ± 11,445.52 RMB, P = 0.03). Using the 3D printing technology before posterior corrective surgery might reduce the operation time, perioperative blood loss, and transfusion volume. There did not appear to be a benefit to using this technology with respect to complication rate and postoperative radiological outcomes; however, 3D technology could reduce the misplacement rate in patients whose preoperative mean Cobb angle was >50°. Besides, it also increased the patients’ hospital cost. Therefore, future prospective studies are needed to elucidate the efficacy of this emerging technology. PMID:25715261

Design, simulation, and optimization of an RGB polarization independent transmission volume hologram

NASA Astrophysics Data System (ADS)

Mahamat, Adoum Hassan

Volume phase holographic (VPH) gratings have been designed for use in many areas of science and technology such as optical communication, medical imaging, spectroscopy and astronomy. The goal of this dissertation is to design a volume phase holographic grating that provides diffraction efficiencies of at least 70% for the entire visible wavelengths and higher than 90% for red, green, and blue light when the incident light is unpolarized. First, the complete design, simulation and optimization of the volume hologram are presented. The optimization is done using a Monte Carlo analysis to solve for the index modulation needed to provide higher diffraction efficiencies. The solutions are determined by solving the diffraction efficiency equations determined by Kogelnik's two wave coupled-wave theory. The hologram is further optimized using the rigorous coupled-wave analysis to correct for effects of absorption omitted by Kogelnik's method. Second, the fabrication or recording process of the volume hologram is described in detail. The active region of the volume hologram is created by interference of two coherent beams within the thin film. Third, the experimental set up and measurement of some properties including the diffraction efficiencies of the volume hologram, and the thickness of the active region are conducted. Fourth, the polarimetric response of the volume hologram is investigated. The polarization study is developed to provide insight into the effect of the refractive index modulation onto the polarization state and diffraction efficiency of incident light.

Accurately determining log and bark volumes of saw logs using high-resolution laser scan data

Treesearch

R. Edward Thomas; Neal D. Bennett

2014-01-01

Accurately determining the volume of logs and bark is crucial to estimating the total expected value recovery from a log. Knowing the correct size and volume of a log helps to determine which processing method, if any, should be used on a given log. However, applying volume estimation methods consistently can be difficult. Errors in log measurement and oddly shaped...

Chronic fatigue syndrome: illness severity, sedentary lifestyle, blood volume and evidence of diminished cardiac function.

PubMed

Hurwitz, Barry E; Coryell, Virginia T; Parker, Meela; Martin, Pedro; Laperriere, Arthur; Klimas, Nancy G; Sfakianakis, George N; Bilsker, Martin S

2009-10-19

The study examined whether deficits in cardiac output and blood volume in a CFS (chronic fatigue syndrome) cohort were present and linked to illness severity and sedentary lifestyle. Follow-up analyses assessed whether differences in cardiac output levels between CFS and control groups were corrected by controlling for cardiac contractility and TBV (total blood volume). The 146 participants were subdivided into two CFS groups based on symptom severity data, severe (n=30) and non-severe (n=26), and two healthy non-CFS control groups based on physical activity, sedentary (n=58) and non-sedentary (n=32). Controls were matched to CFS participants using age, gender, ethnicity and body mass. Echocardiographic measures indicated that the severe CFS participants had 10.2% lower cardiac volume (i.e. stroke index and end-diastolic volume) and 25.1% lower contractility (velocity of circumferential shortening corrected by heart rate) than the control groups. Dual tag blood volume assessments indicated that the CFS groups had lower TBV, PV (plasma volume) and RBCV (red blood cell volume) than control groups. Of the CFS subjects with a TBV deficit (i.e. > or = 8% below ideal levels), the mean+/-S.D. percentage deficit in TBV, PV and RBCV were -15.4+/-4.0, -13.2+/-5.0 and -19.1+/-6.3% respectively. Lower cardiac volume levels in CFS were substantially corrected by controlling for prevailing TBV deficits, but were not affected by controlling for cardiac contractility levels. Analyses indicated that the TBV deficit explained 91-94% of the group differences in cardiac volume indices. Group differences in cardiac structure were offsetting and, hence, no differences emerged for left ventricular mass index. Therefore the findings indicate that lower cardiac volume levels, displayed primarily by subjects with severe CFS, were not linked to diminished cardiac contractility levels, but were probably a consequence of a co-morbid hypovolaemic condition. Further study is needed to address the extent to which the cardiac and blood volume alterations in CFS have physiological and clinical significance.

Correction for slope in point and transect relascope sampling of downed coarse woody debris

Treesearch

Goran Stahl; Anna Ringvall; Jeffrey H. Gove; Mark J. Ducey

2002-01-01

In this article, the effect of sloping terrain on estimates in point and transect relascope sampling (PRS and TRS, respectively) is studied. With these inventory methods, a wide angle relascope is used either from sample points (PRS) or along survey lines (TRS). Characteristics associated with line-shaped objects on the ground are assessed, e.g., the length or volume...

Interfacial ion solvation: Obtaining the thermodynamic limit from molecular simulations

NASA Astrophysics Data System (ADS)

Cox, Stephen J.; Geissler, Phillip L.

2018-06-01

Inferring properties of macroscopic solutions from molecular simulations is complicated by the limited size of systems that can be feasibly examined with a computer. When long-ranged electrostatic interactions are involved, the resulting finite size effects can be substantial and may attenuate very slowly with increasing system size, as shown by previous work on dilute ions in bulk aqueous solution. Here we examine corrections for such effects, with an emphasis on solvation near interfaces. Our central assumption follows the perspective of Hünenberger and McCammon [J. Chem. Phys. 110, 1856 (1999)]: Long-wavelength solvent response underlying finite size effects should be well described by reduced models like dielectric continuum theory, whose size dependence can be calculated straightforwardly. Applied to an ion in a periodic slab of liquid coexisting with vapor, this approach yields a finite size correction for solvation free energies that differs in important ways from results previously derived for bulk solution. For a model polar solvent, we show that this new correction quantitatively accounts for the variation of solvation free energy with volume and aspect ratio of the simulation cell. Correcting periodic slab results for an aqueous system requires an additional accounting for the solvent's intrinsic charge asymmetry, which shifts electric potentials in a size-dependent manner. The accuracy of these finite size corrections establishes a simple method for a posteriori extrapolation to the thermodynamic limit and also underscores the realism of dielectric continuum theory down to the nanometer scale.

Analyte quantification with comprehensive two-dimensional gas chromatography: assessment of methods for baseline correction, peak delineation, and matrix effect elimination for real samples.

PubMed

Samanipour, Saer; Dimitriou-Christidis, Petros; Gros, Jonas; Grange, Aureline; Samuel Arey, J

2015-01-02

Comprehensive two-dimensional gas chromatography (GC×GC) is used widely to separate and measure organic chemicals in complex mixtures. However, approaches to quantify analytes in real, complex samples have not been critically assessed. We quantified 7 PAHs in a certified diesel fuel using GC×GC coupled to flame ionization detector (FID), and we quantified 11 target chlorinated hydrocarbons in a lake water extract using GC×GC with electron capture detector (μECD), further confirmed qualitatively by GC×GC with electron capture negative chemical ionization time-of-flight mass spectrometer (ENCI-TOFMS). Target analyte peak volumes were determined using several existing baseline correction algorithms and peak delineation algorithms. Analyte quantifications were conducted using external standards and also using standard additions, enabling us to diagnose matrix effects. We then applied several chemometric tests to these data. We find that the choice of baseline correction algorithm and peak delineation algorithm strongly influence the reproducibility of analyte signal, error of the calibration offset, proportionality of integrated signal response, and accuracy of quantifications. Additionally, the choice of baseline correction and the peak delineation algorithm are essential for correctly discriminating analyte signal from unresolved complex mixture signal, and this is the chief consideration for controlling matrix effects during quantification. The diagnostic approaches presented here provide guidance for analyte quantification using GC×GC. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

Improved workflow for quantification of left ventricular volumes and mass using free-breathing motion corrected cine imaging.

PubMed

Cross, Russell; Olivieri, Laura; O'Brien, Kendall; Kellman, Peter; Xue, Hui; Hansen, Michael

2016-02-25

Traditional cine imaging for cardiac functional assessment requires breath-holding, which can be problematic in some situations. Free-breathing techniques have relied on multiple averages or real-time imaging, producing images that can be spatially and/or temporally blurred. To overcome this, methods have been developed to acquire real-time images over multiple cardiac cycles, which are subsequently motion corrected and reformatted to yield a single image series displaying one cardiac cycle with high temporal and spatial resolution. Application of these algorithms has required significant additional reconstruction time. The use of distributed computing was recently proposed as a way to improve clinical workflow with such algorithms. In this study, we have deployed a distributed computing version of motion corrected re-binning reconstruction for free-breathing evaluation of cardiac function. Twenty five patients and 25 volunteers underwent cardiovascular magnetic resonance (CMR) for evaluation of left ventricular end-systolic volume (ESV), end-diastolic volume (EDV), and end-diastolic mass. Measurements using motion corrected re-binning were compared to those using breath-held SSFP and to free-breathing SSFP with multiple averages, and were performed by two independent observers. Pearson correlation coefficients and Bland-Altman plots tested agreement across techniques. Concordance correlation coefficient and Bland-Altman analysis tested inter-observer variability. Total scan plus reconstruction times were tested for significant differences using paired t-test. Measured volumes and mass obtained by motion corrected re-binning and by averaged free-breathing SSFP compared favorably to those obtained by breath-held SSFP (r = 0.9863/0.9813 for EDV, 0.9550/0.9685 for ESV, 0.9952/0.9771 for mass). Inter-observer variability was good with concordance correlation coefficients between observers across all acquisition types suggesting substantial agreement. Both motion corrected re-binning and averaged free-breathing SSFP acquisition and reconstruction times were shorter than breath-held SSFP techniques (p < 0.0001). On average, motion corrected re-binning required 3 min less than breath-held SSFP imaging, a 37% reduction in acquisition and reconstruction time. The motion corrected re-binning image reconstruction technique provides robust cardiac imaging that can be used for quantification that compares favorably to breath-held SSFP as well as multiple average free-breathing SSFP, but can be obtained in a fraction of the time when using cloud-based distributed computing reconstruction.

The Hematocrit Affects the Volume of Plasma Treated With Coupled Plasma Filtration and Adsorption With Predilution.

PubMed

Finazzi, Stefano; Garbero, Elena; Trussardi, Giampietro; Bertolini, Guido

2017-05-01

Coupled plasma filtration and adsorption (CPFA) is an extracorporeal blood purification technique proposed for the treatment of septic-shock. By removing pro- and anti-inflammatory mediators from plasma, CPFA is supposed to have a therapeutic effect on the abnormal inflammatory response seen in this condition. Recently, blood predilution with citrate solution has been adopted to prevent clotting in the CPFA circuit-one of the main problems of the technique. Taking into account the patient's hematocrit, we worked out a formula for the volume of plasma effectively treated by CPFA after predilution. Neglecting this effect, as is commonly done, introduces significant distortions in the estimation of the volume, possibly causing under-treatment. The distortion is stronger when the hematocrit and the predilution fraction are large and weaker when both values shrink. By correctly indicating the daily dose of plasma adsorption received by patients, this formula is essential for assessing the therapeutic efficacy of CPFA and, subsequently, establishing its optimal doses. © 2017 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Toxic effects of electrolyte and trace mineral administration in the intensive care unit.

PubMed

Besunder, J B; Smith, P G

1991-07-01

Electrolytes and trace minerals are administered routinely to ICU patients to correct deficiencies or as specific therapy for various conditions. Complications are usually related to the rate of infusion, rapidity of correction of a deficiency state, or iatrogenic poisoning with the agent. Adverse effects associated with Na+ administration included volume overload, CPM, and central nervous system bleeds. The toxic effects of K+, Ca2+, and Mg2+ are primarily related to their effects on the myocardium, nervous system, and muscle. Other than precipitating or maintaining a metabolic acidosis, Cl- administration is relatively nontoxic. Its accompanying anion (i.e., ammonium or arginine), however, may contribute significantly to patient morbidity and, possibly, mortality. Side effects observed with phosphate administration include hypocalcemia, metastatic calcification, and hypernatremia or hyperkalemia. Most of these toxicities are avoidable if appropriate precautions are taken and appropriate monitoring implemented. Finally, when administering any of these agents, the intensivist should be familiar with their toxicologic profiles and management of potential complications.

Atlas-Based Segmentation Improves Consistency and Decreases Time Required for Contouring Postoperative Endometrial Cancer Nodal Volumes

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

Young, Amy V.; Department of Radiation Oncology, St. Luke's-Roosevelt Hospital, New York, NY; Wortham, Angela

2011-03-01

Purpose: Accurate target delineation of the nodal volumes is essential for three-dimensional conformal and intensity-modulated radiotherapy planning for endometrial cancer adjuvant therapy. We hypothesized that atlas-based segmentation ('autocontouring') would lead to time savings and more consistent contours among physicians. Methods and Materials: A reference anatomy atlas was constructed using the data from 15 postoperative endometrial cancer patients by contouring the pelvic nodal clinical target volume on the simulation computed tomography scan according to the Radiation Therapy Oncology Group 0418 trial using commercially available software. On the simulation computed tomography scans from 10 additional endometrial cancer patients, the nodal clinical targetmore » volume autocontours were generated. Three radiation oncologists corrected the autocontours and delineated the manual nodal contours under timed conditions while unaware of the other contours. The time difference was determined, and the overlap of the contours was calculated using Dice's coefficient. Results: For all physicians, manual contouring of the pelvic nodal target volumes and editing the autocontours required a mean {+-} standard deviation of 32 {+-} 9 vs. 23 {+-} 7 minutes, respectively (p = .000001), a 26% time savings. For each physician, the time required to delineate the manual contours vs. correcting the autocontours was 30 {+-} 3 vs. 21 {+-} 5 min (p = .003), 39 {+-} 12 vs. 30 {+-} 5 min (p = .055), and 29 {+-} 5 vs. 20 {+-} 5 min (p = .0002). The mean overlap increased from manual contouring (0.77) to correcting the autocontours (0.79; p = .038). Conclusion: The results of our study have shown that autocontouring leads to increased consistency and time savings when contouring the nodal target volumes for adjuvant treatment of endometrial cancer, although the autocontours still required careful editing to ensure that the lymph nodes at risk of recurrence are properly included in the target volume.« less

Use, misuse and abuse of diuretics.

PubMed

Bartoli, Ettore; Rossi, Luca; Sola, Daniele; Castello, Luigi; Sainaghi, Pier Paolo; Smirne, Carlo

2017-04-01

Resolution of edema requires a correct interpretation of body fluids-related renal function, to excrete the excess volume while restoring systemic hemodynamics and avoiding renal failure. In heart failure, the intensive diuresis should be matched by continuous fluids refeeding from interstitium to plasma, avoiding central volume depletion. The slowly reabsorbed ascites cannot refeed this contracted volume in cirrhosis: the ensuing activation of intrathoracic receptors, attended by increased adrenergic and Renin release, causes more avid sodium retention, producing a positive fluid and Na balance in the face of continuous treatment. High-dose-furosemide creates a defect in tubular Na causing diuresis adequate to excrete the daily water and electrolyte load in Chronic Renal Failure. Diuretic treatment requires care, caution and bedside "tricks" aimed at minimizing volume contraction by correctly assessing the homeostatic system of body fluids and related renal hemodynamics. Copyright © 2017 European Federation of Internal Medicine. Published by Elsevier B.V. All rights reserved.

Phantom studies investigating extravascular density imaging for partial volume correction of 3-D PET /sup 18/FDG studies

NASA Astrophysics Data System (ADS)

Wassenaar, R. W.; Beanlands, R. S. B.; deKemp, R. A.

2004-02-01

Limited scanner resolution and cardiac motion contribute to partial volume (PV) averaging of cardiac PET images. An extravascular (EV) density image, created from the subtraction of a blood pool scan from a transmission image, has been used to correct for PV averaging in H/sub 2//sup 15/O studies using 2-D imaging but not with 3-D imaging of other tracers such as /sup 18/FDG. A cardiac phantom emulating the left ventricle was used to characterize the method for use in 3-D PET studies. Measurement of the average myocardial activity showed PV losses of 32% below the true activity (p<0.001). Initial application of the EV density correction still yielded a myocardial activity 13% below the true value (p<0.001). This failure of the EV density image was due to the 1.66 mm thick plastic barrier separating the myocardial and ventricular chambers within the phantom. Upon removal of this artifact by morphological dilation of the blood pool, the corrected myocardial value was within 2% of the true value (p=ns). Spherical ROIs (diameter of 2 to 10 mm), evenly distributed about the myocardium, were also used to calculate the average activity. The EV density image was able to account for PV averaging throughout the range of diameters to within a 5% accuracy, however, a small bias was seen as the size of the ROIs increased. This indicated a slight mismatch between the emission and transmission image resolutions, a result of the difference in data acquisitions (i.e., span and ring difference) and default smoothing. These results show that the use of EV density image to correct for PV averaging is possible with 3-D PET. A method of correcting barrier effects in phantoms has been presented, as well as a process for evaluating resolution mismatch.

Homotaurine Effects on Hippocampal Volume Loss and Episodic Memory in Amnestic Mild Cognitive Impairment.

PubMed

Spalletta, Gianfranco; Cravello, Luca; Gianni, Walter; Piras, Federica; Iorio, Mariangela; Cacciari, Claudia; Casini, Anna Rosa; Chiapponi, Chiara; Sancesario, Giuseppe; Fratangeli, Claudia; Orfei, Maria Donata; Caltagirone, Carlo; Piras, Fabrizio

2016-01-01

Homotaurine supplementation may have a positive effect on early Alzheimer's disease. Here, we investigated its potential neuroprotective effect on the hippocampus structure and episodic memory performances in amnestic mild cognitive impairment (aMCI). Neuropsychological, clinical, and neuroimaging assessment in 11 treated and 22 untreated patients were performed at baseline and after 1 year. Magnetic resonance data were analyzed using voxel-based morphometry to explore significant differences (Family Wise Error corrected) between the two groups over time. Patients treated with homotaurine showed decreased volume loss in the left and right hippocampal tail, left and right fusiform gyrus, and right inferior temporal cortex which was associated with improved short-term episodic memory performance as measured by the recency effect of the Rey 15-word list learning test immediate recall. Thus, homotaurine supplementation in individuals with aMCI has a positive effect on hippocampus atrophy and episodic memory loss. Future studies should further clarify the mechanisms of its effects on brain morphometry.

Vocational Education in Correctional Institutions: State-of-the-Art Assessment of Programs in Region IV. Volume I, Final Technical Report.

ERIC Educational Resources Information Center

Rice, Eric; And Others

To identify the issues, characteristics, barriers, and needs related to vocational education provisions in Southeastern correctional institutions, a project was developed. Survey data was collected through a 100% sample of adult and juvenile correctional facilities in seven states. Study procedures utilized a combination of state level interviews,…

The Value of Full Correction: Achieving Excellent and Affordable Results.

PubMed

Kaplan, Julie Bass

2016-01-01

Patients often come to medical aesthetic offices with hopes to fully correct lost facial volume and achieve a natural appearance. Unfortunately, the cost per syringe of dermal filler can be a barrier to desired outcomes. Many aesthetic practitioners do the best they can with the amount of product the patient can afford, often falling short of the "wow" effect for the patient. This article describes what one office implemented to solve the conundrum of affordability while still allowing offices to cover its own financial realities. This tool can help patients achieve beautiful, natural, and affordable outcomes while helping offices advance in manufacturer's tiers, improve word-of-mouth advertising, and increase job satisfaction.

Measurement of Crystalline Lens Volume During Accommodation in a Lens Stretcher

PubMed Central

Marussich, Lauren; Manns, Fabrice; Nankivil, Derek; Maceo Heilman, Bianca; Yao, Yue; Arrieta-Quintero, Esdras; Ho, Arthur; Augusteyn, Robert; Parel, Jean-Marie

2015-01-01

Purpose To determine if the lens volume changes during accommodation. Methods The study used data acquired on 36 cynomolgus monkey lenses that were stretched in a stepwise fashion to simulate disaccommodation. At each step, stretching force and dioptric power were measured and a cross-sectional image of the lens was acquired using an optical coherence tomography system. Images were corrected for refractive distortions and lens volume was calculated assuming rotational symmetry. The average change in lens volume was calculated and the relation between volume change and power change, and between volume change and stretching force, were quantified. Linear regressions of volume-power and volume-force plots were calculated. Results The mean (±SD) volume in the unstretched (accommodated) state was 97 ± 8 mm3. On average, there was a small but statistically significant (P = 0.002) increase in measured lens volume with stretching. The mean change in lens volume was +0.8 ± 1.3 mm3. The mean volume-power and volume-load slopes were −0.018 ± 0.058 mm3/D and +0.16 ± 0.40 mm3/g. Conclusions Lens volume remains effectively constant during accommodation, with changes that are less than 1% on average. This result supports a hypothesis that the change in lens shape with accommodation is accompanied by a redistribution of tissue within the capsular bag without significant compression of the lens contents or fluid exchange through the capsule. PMID:26161985

SeaWiFS Postlaunch Calibration and Validation Analyses

NASA Technical Reports Server (NTRS)

Hooker, Stanford B. (Editor); Firestone, Elaine (Editor); McClain, Charles R.; Barnes, Robert A.; Eplee, Robert E., Jr.; Franz, Bryan A.; Hsu, N. Christina; Patt, Frederick S.; Pietras, Christophe M.; Robinson, Wayne D.

2000-01-01

The effort to resolve data quality issues and improve on the initial data evaluation methodologies of the SeaWiFS Project was an extensive one. These evaluations have resulted, to date, in three major reprocessings of the entire data set where each reprocessing addressed the data quality issues that could be identified up to the time of the reprocessing. Three volumes of the SeaWiFS Postlaunch Technical Report Series (Volumes 9, 10, and 11) are needed to document the improvements implemented since launch. Volume 10 continues the sequential presentation of postlaunch data analysis and algorithm descriptions begun in Volume 9. Chapter 1 of Volume 10 describes an absorbing aerosol index, similar to that produced by the Total Ozone Mapping Spectrometer (TOMS) Project, which is used to flag pixels contaminated by absorbing aerosols, such as, dust and smoke. Chapter 2 discusses the algorithm being used to remove SeaWiFS out-of-band radiance from the water-leaving radiances. Chapter 3 provides an itemization of all significant changes in the processing algorithms for each of the first three reprocessings. Chapter 4 shows the time series of global clear water and deep-water (depths greater than 1,000m) bio-optical and atmospheric properties (normalized water-leaving radiances, chlorophyll, atmospheric optical depth, etc.) based on the eight-day composites as a check on the sensor calibration stability. Chapter 5 examines the variation in the derived products with scan angle using high resolution data around Hawaii to test for residual scan modulation effects and atmospheric correction biases. Chapter 6 provides a methodology for evaluating the atmospheric correction algorithm and atmospheric derived products using ground-based observations. Similarly, Chapter 7 presents match-up comparisons of coincident satellite and in situ data to determine the accuracy of the water-leaving radiances, chlorophyll a, and K(490) products.

Alcohol consumption during adolescence is associated with reduced grey matter volumes.

PubMed

Heikkinen, Noora; Niskanen, Eini; Könönen, Mervi; Tolmunen, Tommi; Kekkonen, Virve; Kivimäki, Petri; Tanila, Heikki; Laukkanen, Eila; Vanninen, Ritva

2017-04-01

Cognitive impairment has been associated with excessive alcohol use, but its neural basis is poorly understood. Chronic excessive alcohol use in adolescence may lead to neuronal loss and volumetric changes in the brain. Our objective was to compare the grey matter volumes of heavy- and light-drinking adolescents. This was a longitudinal study: heavy-drinking adolescents without an alcohol use disorder and their light-drinking controls were followed-up for 10 years using questionnaires at three time-points. Magnetic resonance imaging was conducted at the last time-point. The area near Kuopio University Hospital, Finland. The 62 participants were aged 22-28 years and included 35 alcohol users and 27 controls who had been followed-up for approximately 10 years. Alcohol use was measured by the Alcohol Use Disorders Identification Test (AUDIT)-C at three time-points during 10 years. Participants were selected based on their AUDIT-C score. Magnetic resonance imaging was conducted at the last time-point. Grey matter volume was determined and compared between heavy- and light-drinking groups using voxel-based morphometry on three-dimensional T1-weighted magnetic resonance images using predefined regions of interest and a threshold of P < 0.05, with small volume correction applied on cluster level. Grey matter volumes were significantly smaller among heavy-drinking participants in the bilateral anterior cingulate cortex, right orbitofrontal and frontopolar cortex, right superior temporal gyrus and right insular cortex compared to the control group (P < 0.05, family-wise error-corrected cluster level). Excessive alcohol use during adolescence appears to be associated with an abnormal development of the brain grey matter. Moreover, the structural changes detected in the insula of alcohol users may reflect a reduced sensitivity to alcohol's negative subjective effects. © 2016 Society for the Study of Addiction.

Phase Error Correction in Time-Averaged 3D Phase Contrast Magnetic Resonance Imaging of the Cerebral Vasculature

PubMed Central

MacDonald, M. Ethan; Forkert, Nils D.; Pike, G. Bruce; Frayne, Richard

2016-01-01

Purpose Volume flow rate (VFR) measurements based on phase contrast (PC)-magnetic resonance (MR) imaging datasets have spatially varying bias due to eddy current induced phase errors. The purpose of this study was to assess the impact of phase errors in time averaged PC-MR imaging of the cerebral vasculature and explore the effects of three common correction schemes (local bias correction (LBC), local polynomial correction (LPC), and whole brain polynomial correction (WBPC)). Methods Measurements of the eddy current induced phase error from a static phantom were first obtained. In thirty healthy human subjects, the methods were then assessed in background tissue to determine if local phase offsets could be removed. Finally, the techniques were used to correct VFR measurements in cerebral vessels and compared statistically. Results In the phantom, phase error was measured to be <2.1 ml/s per pixel and the bias was reduced with the correction schemes. In background tissue, the bias was significantly reduced, by 65.6% (LBC), 58.4% (LPC) and 47.7% (WBPC) (p < 0.001 across all schemes). Correction did not lead to significantly different VFR measurements in the vessels (p = 0.997). In the vessel measurements, the three correction schemes led to flow measurement differences of -0.04 ± 0.05 ml/s, 0.09 ± 0.16 ml/s, and -0.02 ± 0.06 ml/s. Although there was an improvement in background measurements with correction, there was no statistical difference between the three correction schemes (p = 0.242 in background and p = 0.738 in vessels). Conclusions While eddy current induced phase errors can vary between hardware and sequence configurations, our results showed that the impact is small in a typical brain PC-MR protocol and does not have a significant effect on VFR measurements in cerebral vessels. PMID:26910600

Positioning accuracy during VMAT of gynecologic malignancies and the resulting dosimetric impact by a 6-degree-of-freedom couch in combination with daily kilovoltage cone beam computed tomography.

PubMed

Yao, Lihong; Zhu, Lihong; Wang, Junjie; Liu, Lu; Zhou, Shun; Jiang, ShuKun; Cao, Qianqian; Qu, Ang; Tian, Suqing

2015-04-26

To improve the delivery of radiotherapy in gynecologic malignancies and to minimize the irradiation of unaffected tissues by using daily kilovoltage cone beam computed tomography (kV-CBCT) to reduce setup errors. Thirteen patients with gynecologic cancers were treated with postoperative volumetric-modulated arc therapy (VMAT). All patients had a planning CT scan and daily CBCT during treatment. Automatic bone anatomy matching was used to determine initial inter-fraction positioning error. Positional correction on a six-degrees-of-freedom (6DoF) couch was followed by a second scan to calculate the residual inter-fraction error, and a post-treatment scan assessed intra-fraction motion. The margins of the planning target volume (MPTV) were calculated from these setup variations and the effect of margin size on normal tissue sparing was evaluated. In total, 573 CBCT scans were acquired. Mean absolute pre-/post-correction errors were obtained in all six planes. With 6DoF couch correction, the MPTV accounting for intra-fraction errors was reduced by 3.8-5.6 mm. This permitted a reduction in the maximum dose to the small intestine, bladder and femoral head (P=0.001, 0.035 and 0.032, respectively), the average dose to the rectum, small intestine, bladder and pelvic marrow (P=0.003, 0.000, 0.001 and 0.000, respectively) and markedly reduced irradiated normal tissue volumes. A 6DoF couch in combination with daily kV-CBCT can considerably improve positioning accuracy during VMAT treatment in gynecologic malignancies, reducing the MPTV. The reduced margin size permits improved normal tissue sparing and a smaller total irradiated volume.

Extrapolation-Based References Improve Motion and Eddy-Current Correction of High B-Value DWI Data: Application in Parkinson's Disease Dementia.

PubMed

Nilsson, Markus; Szczepankiewicz, Filip; van Westen, Danielle; Hansson, Oskar

2015-01-01

Conventional motion and eddy-current correction, where each diffusion-weighted volume is registered to a non diffusion-weighted reference, suffers from poor accuracy for high b-value data. An alternative approach is to extrapolate reference volumes from low b-value data. We aim to compare the performance of conventional and extrapolation-based correction of diffusional kurtosis imaging (DKI) data, and to demonstrate the impact of the correction approach on group comparison studies. DKI was performed in patients with Parkinson's disease dementia (PDD), and healthy age-matched controls, using b-values of up to 2750 s/mm2. The accuracy of conventional and extrapolation-based correction methods was investigated. Parameters from DTI and DKI were compared between patients and controls in the cingulum and the anterior thalamic projection tract. Conventional correction resulted in systematic registration errors for high b-value data. The extrapolation-based methods did not exhibit such errors, yielding more accurate tractography and up to 50% lower standard deviation in DKI metrics. Statistically significant differences were found between patients and controls when using the extrapolation-based motion correction that were not detected when using the conventional method. We recommend that conventional motion and eddy-current correction should be abandoned for high b-value data in favour of more accurate methods using extrapolation-based references.

LANDSAT-D data format control book. Volume 6: (Products)

NASA Technical Reports Server (NTRS)

Kabat, F.

1981-01-01

Four basic product types are generated from the raw thematic mapper (TM) and multispectral scanner (MSS) payload data by the NASA GSFC LANDSAT 4 data management system: (1) unprocessed data (raw sensor data); (2) partially processed data, which consists of radiometrically corrected sensor data with geometric correction information appended; (3) fully processed data, which consists of radiometrically and geometrically corrected sensor data; and (4) inventory data which consists of summary information about product types 2 and 3. High density digital recorder formatting and the radiometric correction process are described. Geometric correction information is included.

Effect of PVA fiber content on creep property of fiber reinforced high-strength concrete columns

NASA Astrophysics Data System (ADS)

Xu, Zongnan; Wang, Tao; Wang, Weilun

2018-04-01

The effect of PVA (polyvinyl alcohol) fiber content on the creep property of fiber reinforced high-strength concrete columns was investigated. The correction factor of PVA fiber content was proposed and the creep prediction model of ACI209 was modified. Controlling the concrete strength as C80, changing the content of PVA fiber (volume fraction 0%, 0.25%, 0.5%, 1% respectively), the creep experiment of PVA fiber reinforced concrete columns was carried out, the creep coefficient of each specimen was calculated to characterize the creep property. The influence of PVA fiber content on the creep property was analyzed based on the creep coefficient and the calculation results of several frequently used creep prediction models. The correction factor of PVA fiber content was proposed to modify the ACI209 creep prediction model.

Diurnal fluctuations in brain volume: Statistical analyses of MRI from large populations.

PubMed

Nakamura, Kunio; Brown, Robert A; Narayanan, Sridar; Collins, D Louis; Arnold, Douglas L

2015-09-01

We investigated fluctuations in brain volume throughout the day using statistical modeling of magnetic resonance imaging (MRI) from large populations. We applied fully automated image analysis software to measure the brain parenchymal fraction (BPF), defined as the ratio of the brain parenchymal volume and intracranial volume, thus accounting for variations in head size. The MRI data came from serial scans of multiple sclerosis (MS) patients in clinical trials (n=755, 3269 scans) and from subjects participating in the Alzheimer's Disease Neuroimaging Initiative (ADNI, n=834, 6114 scans). The percent change in BPF was modeled with a linear mixed effect (LME) model, and the model was applied separately to the MS and ADNI datasets. The LME model for the MS datasets included random subject effects (intercept and slope over time) and fixed effects for the time-of-day, time from the baseline scan, and trial, which accounted for trial-related effects (for example, different inclusion criteria and imaging protocol). The model for ADNI additionally included the demographics (baseline age, sex, subject type [normal, mild cognitive impairment, or Alzheimer's disease], and interaction between subject type and time from baseline). There was a statistically significant effect of time-of-day on the BPF change in MS clinical trial datasets (-0.180 per day, that is, 0.180% of intracranial volume, p=0.019) as well as the ADNI dataset (-0.438 per day, that is, 0.438% of intracranial volume, p<0.0001), showing that the brain volume is greater in the morning. Linearly correcting the BPF values with the time-of-day reduced the required sample size to detect a 25% treatment effect (80% power and 0.05 significance level) on change in brain volume from 2 time-points over a period of 1year by 2.6%. Our results have significant implications for future brain volumetric studies, suggesting that there is a potential acquisition time bias that should be randomized or statistically controlled to account for the day-to-day brain volume fluctuations. Copyright © 2015 Elsevier Inc. All rights reserved.

Examining the effect of psychopathic traits on gray matter volume in a community substance abuse sample.

PubMed

Cope, Lora M; Shane, Matthew S; Segall, Judith M; Nyalakanti, Prashanth K; Stevens, Michael C; Pearlson, Godfrey D; Calhoun, Vince D; Kiehl, Kent A

2012-11-30

Psychopathy is believed to be associated with brain abnormalities in both paralimbic (i.e., orbitofrontal cortex, insula, temporal pole, parahippocampal gyrus, posterior cingulate) and limbic (i.e., amygdala, hippocampus, anterior cingulate) regions. Recent structural imaging studies in both community and prison samples are beginning to support this view. Sixty-six participants, recruited from community corrections centers, were administered the Hare psychopathy checklist-revised (PCL-R), and underwent magnetic resonance imaging (MRI). Voxel-based morphometry was used to test the hypothesis that psychopathic traits would be associated with gray matter reductions in limbic and paralimbic regions. Effects of lifetime drug and alcohol use on gray matter volume were covaried. Psychopathic traits were negatively associated with gray matter volumes in right insula and right hippocampus. Additionally, psychopathic traits were positively associated with gray matter volumes in bilateral orbital frontal cortex and right anterior cingulate. Exploratory regression analyses indicated that gray matter volumes within right hippocampus and left orbital frontal cortex combined to explain 21.8% of the variance in psychopathy scores. These results support the notion that psychopathic traits are associated with abnormal limbic and paralimbic gray matter volume. Furthermore, gray matter increases in areas shown to be functionally impaired suggest that the structure-function relationship may be more nuanced than previously thought. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Supine posture changes lung volumes and increases ventilation heterogeneity in cystic fibrosis.

PubMed

Smith, Laurie J; Macleod, Kenneth A; Collier, Guilhem J; Horn, Felix C; Sheridan, Helen; Aldag, Ina; Taylor, Chris J; Cunningham, Steve; Wild, Jim M; Horsley, Alex

2017-01-01

Lung Clearance Index (LCI) is recognised as an early marker of cystic fibrosis (CF) lung disease. The effect of posture on LCI however is important when considering longitudinal measurements from infancy and when comparing LCI to imaging studies. 35 children with CF and 28 healthy controls (HC) were assessed. Multiple breath washout (MBW) was performed both sitting and supine in triplicate and analysed for LCI, Scond, Sacin, and lung volumes. These values were also corrected for the Fowler dead-space to create 'alveolar' indices. From sitting to supine there was a significant increase in LCI and a significant decrease in FRC for both CF and HC (p<0.01). LCI, when adjusted to estimate 'alveolar' LCI (LCIalv), increased the magnitude of change with posture for both LCIalv and FRCalv in both groups, with a greater effect of change in lung volume in HC compared with children with CF. The % change in LCIalv for all subjects correlated significantly with lung volume % changes, most notably tidal volume/functional residual capacity (Vtalv/FRCalv (r = 0.54,p<0.001)). There is a significant increase in LCI from sitting to supine, which we believe to be in part due to changes in lung volume and also increasing ventilation heterogeneity related to posture. This may have implications in longitudinal measurements from infancy to older childhood and for studies comparing supine imaging methods to LCI.

Application and assessment of a robust elastic motion correction algorithm to dynamic MRI.

PubMed

Herrmann, K-H; Wurdinger, S; Fischer, D R; Krumbein, I; Schmitt, M; Hermosillo, G; Chaudhuri, K; Krishnan, A; Salganicoff, M; Kaiser, W A; Reichenbach, J R

2007-01-01

The purpose of this study was to assess the performance of a new motion correction algorithm. Twenty-five dynamic MR mammography (MRM) data sets and 25 contrast-enhanced three-dimensional peripheral MR angiographic (MRA) data sets which were affected by patient motion of varying severeness were selected retrospectively from routine examinations. Anonymized data were registered by a new experimental elastic motion correction algorithm. The algorithm works by computing a similarity measure for the two volumes that takes into account expected signal changes due to the presence of a contrast agent while penalizing other signal changes caused by patient motion. A conjugate gradient method is used to find the best possible set of motion parameters that maximizes the similarity measures across the entire volume. Images before and after correction were visually evaluated and scored by experienced radiologists with respect to reduction of motion, improvement of image quality, disappearance of existing lesions or creation of artifactual lesions. It was found that the correction improves image quality (76% for MRM and 96% for MRA) and diagnosability (60% for MRM and 96% for MRA).

Clinical evaluation of respiration-induced attenuation uncertainties in pulmonary 3D PET/CT.

PubMed

Kruis, Matthijs F; van de Kamer, Jeroen B; Vogel, Wouter V; Belderbos, José Sa; Sonke, Jan-Jakob; van Herk, Marcel

2015-12-01

In contemporary positron emission tomography (PET)/computed tomography (CT) scanners, PET attenuation correction is performed by means of a CT-based attenuation map. Respiratory motion can however induce offsets between the PET and CT data. Studies have demonstrated that these offsets can cause errors in quantitative PET measures. The purpose of this study is to quantify the effects of respiration-induced CT differences on the attenuation correction of pulmonary 18-fluordeoxyglucose (FDG) 3D PET/CT in a patient population and to investigate contributing factors. For 32 lung cancer patients, 3D-CT, 4D-PET and 4D-CT data were acquired. The 4D FDG PET data were attenuation corrected (AC) using a free-breathing 3D-CT (3D-AC), the end-inspiration CT (EI-AC), the end-expiration CT (EE-AC) or phase-by-phase (P-AC). After reconstruction and AC, the 4D-PET data were averaged. In the 4Davg data, we measured maximum tumour standardised uptake value (SUV)max in the tumour, SUVmean in a lung volume of interest (VOI) and average SUV (SUVmean) in a muscle VOI. On the 4D-CT, we measured the lung volume differences and CT number changes between inhale and exhale in the lung VOI. Compared to P-AC, we found -2.3% (range -9.7% to 1.2%) lower tumour SUVmax in EI-AC and 2.0% (range -0.9% to 9.5%) higher SUVmax in EE-AC. No differences in the muscle SUV were found. The use of 3D-AC led to respiration-induced SUVmax differences up to 20% compared to the use of P-AC. SUVmean differences in the lung VOI between EI-AC and EE-AC correlated to average CT differences in this region (ρ = 0.83). SUVmax differences in the tumour correlated to the volume changes of the lungs (ρ = -0.55) and the motion amplitude of the tumour (ρ = 0.53), both as measured on the 4D-CT. Respiration-induced CT variations in clinical data can in extreme cases lead to SUV effects larger than 10% on PET attenuation correction. These differences were case specific and correlated to differences in CT number in the lungs.

Variability in Annual and Average Mass Changes in Antarctica from 2004 to 2009 using Satellite Laser Altimetry

NASA Astrophysics Data System (ADS)

Babonis, G. S.; Csatho, B. M.; Schenk, A. F.

2016-12-01

We present a new record of Antarctic ice thickness changes, reconstructed from ICESat laser altimetry observations, from 2004-2009, at over 100,000 locations across the Antarctic Ice Sheet (AIS). This work generates elevation time series at ICESat groundtrack crossover regions on an observation-by-observation basis, with rigorous, quantified, error estimates using the SERAC approach (Schenk and Csatho, 2012). The results include average and annual elevation, volume and mass changes in Antarctica, fully corrected for glacial isostatic adjustment (GIA) and known intercampaign biases; and partitioned into contributions from surficial processes (e.g. firn densification) and ice dynamics. The modular flexibility of the SERAC framework allows for the assimilation of multiple ancillary datasets (e.g. GIA models, Intercampaign Bias Corrections, IBC), in a common framework, to calculate mass changes for several different combinations of GIA models and IBCs and to arrive at a measure of variability from these results. We are able to determine the effect these corrections have on annual and average volume and mass change calculations in Antarctica, and to explore how these differences vary between drainage basins and with elevation. As such, this contribution presents a method that compliments, and is consistent with, the 2012 Ice sheet Mass Balance Inter-comparison Exercise (IMBIE) results (Shepherd 2012). Additionally, this work will contribute to the 2016 IMBIE, which seeks to reconcile ice sheet mass changes from different observations,, including laser altimetry, using a different methodologies and ancillary datasets including GIA models, Firn Densification Models, and Intercampaign Bias Corrections.

Quantifying Rigid and Nonrigid Motion of Liver Tumors During Stereotactic Body Radiation Therapy

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

Xu, Qianyi, E-mail: xuqianyi@gmail.com; Hanna, George; Grimm, Jimm

2014-09-01

Purpose: To quantify rigid and nonrigid motion of liver tumors using reconstructed 3-dimensional (3D) fiducials from stereo imaging during CyberKnife-based stereotactic body radiation therapy (SBRT). Methods and Materials: Twenty-three liver patients treated with 3 fractions of SBRT were used in this study. After 2 orthogonal kilovoltage images were taken during treatment, the 3D locations of the fiducials were generated by the CyberKnife system and validated using geometric derivations. A total of 4824 pairs of kilovoltage images from start to end of treatment were analyzed. For rigid motion, the rotational angles and translational shifts were reported by aligning 3D fiducial groupsmore » from different image pairs, using least-squares fitting. For nonrigid motion, we quantified interfractional tumor volume variations by using the proportional volume derived from the fiducials, which correlates to the sum of interfiducial distances. The individual fiducial displacements were also reported (1) after rigid corrections and (2) without angle corrections. Results: The proportional volume derived by the fiducials demonstrated a volume-increasing trend in the second (101.9% ± 3.6%) and third (101.0 ± 5.9%) fractions among most patients, possibly due to radiation-induced edema. For all patients, the translational shifts in left-right, anteroposterior, and superoinferior directions were 2.1 ± 2.3 mm, 2.9 ± 2.8 mm, and 6.4 ± 5.5 mm, respectively. The greatest translational shifts occurred in the superoinferior direction, likely due to respiratory motion from the diaphragm. The rotational angles in roll, pitch, and yaw were 1.2° ± 1.8°, 1.8° ± 2.4°, and 1.7° ± 2.1°, respectively. The 3D individual fiducial displacements with rigid corrections were 0.2 ± 0.2 mm and increased to 0.5 ± 0.4 mm without rotational corrections. Conclusions: Accurate 3D locations of internal fiducials can be reconstructed from stereo imaging during treatment. As an effective surrogate to tumor motion, fiducials provide a close estimation of both rigid and nonrigid motion of liver tumors. The reported displacements could be further utilized for tumor margin definition and motion management in conventional linear accelerator–based liver SBRT.« less

Quantification of FDG-PET/CT with delayed imaging in patients with newly diagnosed recurrent breast cancer.

PubMed

Baun, Christina; Falch, Kirsten; Gerke, Oke; Hansen, Jeanette; Nguyen, Tram; Alavi, Abass; Høilund-Carlsen, Poul-Flemming; Hildebrandt, Malene G

2018-05-09

Several studies have shown the advantage of delayed-time-point imaging with 18F-FDG-PET/CT to distinguish malignant from benign uptake. This may be relevant in cancer diseases with low metabolism, such as breast cancer. We aimed at examining the change in SUV from 1 h (1h) to 3 h (3h) time-point imaging in local and distant lesions in patients with recurrent breast cancer. Furthermore, we investigated the effect of partial volume correction in the different types of metastases, using semi-automatic quantitative software (ROVER™). One-hundred and two patients with suspected breast cancer recurrence underwent whole-body PET/CT scans 1h and 3h after FDG injection. Semi-quantitative standardised uptake values (SUVmax, SUVmean) and partial volume corrected SUVmean (cSUVmean), were estimated in malignant lesions, and as reference in healthy liver tissue. The change in quantitative measures from 1h to 3h was calculated, and SUVmean was compared to cSUVmean. Metastases were verified by biopsy. Of the 102 included patients, 41 had verified recurrent disease with in median 15 lesions (range 1-70) amounting to a total of 337 malignant lesions included in the analysis. SUVmax of malignant lesions increased from 6.4 ± 3.4 [0.9-19.7] (mean ± SD, min and max) at 1h to 8.1 ± 4.4 [0.7-29.7] at 3h. SUVmax in breast, lung, lymph node and bone lesions increased significantly (p < 0.0001) between 1h and 3h by on average 25, 40, 33, and 27%, respectively. A similar pattern was observed with (uncorrected) SUVmean. Partial volume correction increased SUVmean significantly, by 63 and 71% at 1h and 3h imaging, respectively. The highest impact was in breast lesions at 3h, where cSUVmean increased by 87% compared to SUVmean. SUVs increased from 1h to 3h in malignant lesions, SUVs of distant recurrence were in general about twice as high as those of local recurrence. Partial volume correction caused significant increases in these values. However, it is questionable, if these relatively modest quantitative advances of 3h imaging are sufficient to warrant delayed imaging in this patient group. ClinicalTrails.gov NCT01552655 . Registered 28 February 2012, partly retrospectively registered.

Effect of perfluorocarbon (perfluorooctyl bromide) vapor on tidal volume measurement during partial liquid ventilation.

PubMed

Davies, Mark W; Dunster, Kimble R

2002-05-01

To compare measured tidal volumes with and without perfluorocarbon (perfluorooctyl bromide) vapor, by using tidal volumes in the range suitable for neonates ventilated with partial liquid ventilation. We also aimed to determine the correction factor needed to calculate tidal volumes measured in the presence of perfluorooctyl bromide vapor. Prospective, experimental study. Neonatal research laboratory. Reproducible tidal volumes from 5 to 30 mL were produced with a rodent ventilator and drawn from humidifier chambers immersed in a water bath at 37 degrees C. Control tidal volumes were drawn from a chamber containing oxygen and water vapor, and the perfluorocarbon tidal volumes were drawn from a chamber containing oxygen, water vapor, and perfluorooctyl bromide vapor. Tidal volumes were measured by a VenTrak respiratory mechanics monitor with a neonatal flow sensor and a Dräger pneumotachometer attached to a Dräger neonatal ventilator. All tidal volumes measured with perfluorooctyl bromide vapor were increased compared with control. The VenTrak-measured tidal volumes increased by 1.8% to 3.5% (an overall increase of 2.2%). The increase was greater with the Dräger hot-wire anemometer: from 2.4% to 6.1% (an overall increase of 5.9%). Regression equations for mean control tidal volumes (response, Y) vs. mean perfluorooctyl bromide tidal volumes (predictor, X) are as follows: for the VenTrak, Y = -0.026 + (0.978 x X), r =.9999, p <.0001; and for the Dräger, Y = 0.251 + (0.944 x X), r =.9996, p <.0001. The presence of perfluorooctyl bromide vapor in the gas flowing through pneumotachometers gives falsely high tidal volume measurements. An estimate of the true tidal volume allowing for the presence of perfluorooctyl bromide vapor can be made from regression equations. Any calculation of lung mechanics must take into account the effect of perfluorooctyl bromide vapor on the measurement of tidal volume.

Effects of Long-Term Low-Level Radiofrequency Radiation Exposure on Rats. Volume 1. Design, Facilities, and Procedures.

DTIC Science & Technology

1983-09-01

uncovering unsuspected organ system malfunctions. In animals with subclinical or undiagnosed abnormalities, the emphasis is placed on the correct...normochromic, normocytic anemia are suggestive of hypothyroidism , although they do not occur in all hypothyroid animals. The thyroid hormones, thyroxine (T4...evaluation increased the opportunity to detect subclinical abnormalities and follow their pathophysiological course. Open-field assessment was conducted

Method for correcting for isotope burn-in effects in fission neutron dosimeters

DOEpatents

Gold, Raymond; McElroy, William N.

1988-01-01

A method is described for correcting for effect of isotope burn-in in fission neutron dosimeters. Two quantities are measured in order to quantify the "burn-in" contribution, namely P.sub.Z',A', the amount of (Z', A') isotope that is burned-in, and F.sub.Z', A', the fissions per unit volume produced in the (Z', A') isotope. To measure P.sub.Z', A', two solid state track recorder fission deposits are prepared from the very same material that comprises the fission neutron dosimeter, and the mass and mass density are measured. One of these deposits is exposed along with the fission neutron dosimeter, whereas the second deposit is subsequently used for observation of background. P.sub.Z', A' is then determined by conducting a second irradiation, wherein both the irradiated and unirradiated fission deposits are used in solid state track recorder dosimeters for observation of the absolute number of fissions per unit volume. The difference between the latter determines P.sub.Z', A' since the thermal neutron cross section is known. F.sub.Z', A' is obtained by using a fission neutron dosimeter for this specific isotope, which is exposed along with the original threshold fission neutron dosimeter to experience the same neutron flux-time history at the same location. In order to determine the fissions per unit volume produced in the isotope (Z', A') as it ingrows during the irradiation, B.sub.Z', A', from these observations, the neutron field must generally be either time independent or a separable function of time t and neutron energy E.

A Model-Based Approach for Microvasculature Structure Distortion Correction in Two-Photon Fluorescence Microscopy Images

PubMed Central

Dao, Lam; Glancy, Brian; Lucotte, Bertrand; Chang, Lin-Ching; Balaban, Robert S; Hsu, Li-Yueh

2015-01-01

SUMMARY This paper investigates a post-processing approach to correct spatial distortion in two-photon fluorescence microscopy images for vascular network reconstruction. It is aimed at in vivo imaging of large field-of-view, deep-tissue studies of vascular structures. Based on simple geometric modeling of the object-of-interest, a distortion function is directly estimated from the image volume by deconvolution analysis. Such distortion function is then applied to sub volumes of the image stack to adaptively adjust for spatially varying distortion and reduce the image blurring through blind deconvolution. The proposed technique was first evaluated in phantom imaging of fluorescent microspheres that are comparable in size to the underlying capillary vascular structures. The effectiveness of restoring three-dimensional spherical geometry of the microspheres using the estimated distortion function was compared with empirically measured point-spread function. Next, the proposed approach was applied to in vivo vascular imaging of mouse skeletal muscle to reduce the image distortion of the capillary structures. We show that the proposed method effectively improve the image quality and reduce spatially varying distortion that occurs in large field-of-view deep-tissue vascular dataset. The proposed method will help in qualitative interpretation and quantitative analysis of vascular structures from fluorescence microscopy images. PMID:26224257

Further applications of Archimedes' principle in the correction of asymmetrical breasts.

PubMed

Schultz, R C; Dolezal, R F; Nolan, J

1986-02-01

Archimedes' law of buoyancy has been extended to the preoperative bedside assessment of volume differences between breasts, whatever their cause. The simple method described has proved to be a helpful aid in surgical procedures for the correction of breast asymmetry.

[Palliative surgical correction of respiratory insufficiency in diffusive pulmonary emphysema].

PubMed

Gorbunkov, S D; Varlamov, V V; Cherny, S M; Lukina, O V; Kiryukhina, L D; Romanikhin, A I; Zinchenko, A V; Akopov, A L

To analyze early postoperative period in patients with diffuse pulmonary emphysema after palliative surgical correction of respiratory failure. The study included 196 patients who underwent bullectomy (n=111) and surgical reduction of pulmonary volume (n=85). Overall morbidity and mortality were 40.8% and 12.2% respectively. Among patients older than 60 years these values were significantly higher (58.0% and 22.6% respectively). It was shown that age over 60 years is associated with high risk of complications and mortality after excision of large and giant bulls. In patients <60 years morbidity is comparable after bullectomy and surgical reduction of pulmonary volume. Selection of patients for palliative surgical correction of respiratory failure is generally corresponded to that for lung transplantation. However, these methods should be considered complementary rather competing.

Dose measurement in heterogeneous phantoms with an extrapolation chamber

NASA Astrophysics Data System (ADS)

Deblois, Francois

A hybrid phantom-embedded extrapolation chamber (PEEC) made of Solid Water(TM) and bone-equivalent material was used for determining absolute dose in a bone-equivalent phantom irradiated with clinical radiation beams (cobalt-60 gamma rays; 6 and 18 MV x-rays; and 9 and 15 MeV electrons). The dose was determined with the Spencer-Attix cavity theory, using ionization gradient measurements and an indirect determination of the chamber air-mass through measurements of chamber capacitance. The air gaps used were between 2 and 3 mm and the sensitive air volume of the extrapolation chamber was remotely controlled through the motion of the motorized piston with a precision of +/-0.0025 mm. The collected charge was corrected for ionic recombination and diffusion in the chamber air volume following the standard two-voltage technique. Due to the hybrid chamber design, correction factors accounting for scatter deficit and electrode composition were determined and applied in the dose equation to obtain dose data for the equivalent homogeneous bone phantom. Correction factors for graphite electrodes were calculated with Monte Carlo techniques and the calculated results were verified through relative air cavity dose measurements for three different polarizing electrode materials: graphite, steel, and brass in conjunction with a graphite collecting electrode. Scatter deficit, due mainly to loss of lateral scatter in the hybrid chamber, reduces the dose to the air cavity in the hybrid PEEC in comparison with full bone PEEC from 0.7 to ˜2% depending on beam quality and energy. In megavoltage photon and electron beams, graphite electrodes do not affect the dose measurement in the Solid Water(TM) PEEC but decrease the cavity dose by up to 5% in the bone-equivalent PEEC even for very thin graphite electrodes (<0.0025 cm). The collecting electrode material in comparison with the polarizing electrode material has a larger effect on the electrode correction factor; the thickness of thin electrodes, on the other hand, has a negligible effect on dose determination. The uncalibrated hybrid PEEC is an accurate and absolute device for measuring the dose directly in bone material in conjunction with appropriate correction factors determined with Monte Carlo techniques.

Computational Investigation of Soot and Radiation in Turbulent Reacting Flows

NASA Astrophysics Data System (ADS)

Lalit, Harshad

This study delves into computational modeling of soot and infrared radiation for turbulent reacting flows, detailed understanding of both of which is paramount in the design of cleaner engines and pollution control. In the first part of the study, the concept of Stochastic Time and Space Series Analysis (STASS) as a numerical tool to compute time dependent statistics of radiation intensity is introduced for a turbulent premixed flame. In the absence of high fidelity codes for large eddy simulation or direct numerical simulation of turbulent flames, the utility of STASS for radiation imaging of reacting flows to understand the flame structure is assessed by generating images of infrared radiation in spectral bands dominated by radiation from gas phase carbon dioxide and water vapor using an assumed PDF method. The study elucidates the need for time dependent computation of radiation intensity for validation with experiments and the need for accounting for turbulence radiation interactions for correctly predicting radiation intensity and consequently the flame temperature and NOx in a reacting fluid flow. Comparison of single point statistics of infrared radiation intensity with measurements show that STASS can not only predict the flame structure but also estimate the dynamics of thermochemical scalars in the flame with reasonable accuracy. While a time series is used to generate realizations of thermochemical scalars in the first part of the study, in the second part, instantaneous realizations of resolved scale temperature, CO2 and H2O mole fractions and soot volume fractions are extracted from a large eddy simulation (LES) to carry out quantitative imaging of radiation intensity (QIRI) for a turbulent soot generating ethylene diffusion flame. A primary motivation of the study is to establish QIRI as a computational tool for validation of soot models, especially in the absence of conventional flow field and measured scalar data for sooting flames. Realizations of scalars from the LES are used in conjunction with the radiation heat transfer equation and a narrow band radiation model to compute time dependent and time averaged images of infrared radiation intensity in spectral bands corresponding to molecular radiation from gas phase carbon dioxide and soot particles exclusively. While qualitative and quantitative comparisons with measured images in the CO2 radiation band show that the flame structure is correctly computed, images computed in the soot radiation band illustrate that the soot volume fraction is under predicted by the computations. The effect of the soot model and cause of under prediction is investigated further by correcting the soot volume fraction using an empirical state relationship. By comparing default simulations with computations using the state relation, it is shown that while the soot model under-estimates the soot concentration, it correctly computes the intermittency of soot in the flame. The study of sooting flames is extended further by performing a parametric analysis of physical and numerical parameters that affect soot formation and transport in two laboratory scale turbulent sooting flames, one fueled by natural gas and the other by ethylene. The study is focused on investigating the effect of molecular diffusion of species, dilution of fuel with hydrogen gas and the effect of chemical reaction mechanism on the soot concentration in the flame. The effect of species Lewis numbers on soot evolution and transport is investigated by carrying out simulations, first with the default equal diffusivity (ED) assumption and then by incorporating a differential diffusion (DD) model. Computations using the DD model over-estimate the concentration of the soot precursor and soot oxidizer species, leading to inconsistencies in the estimate of the soot concentration. The linear differential diffusion (LDD) model, reported previously to consistently model differential diffusion effects is implemented to correct the over prediction effect of the DD model. It is shown that the effect of species Lewis number on soot evolution is a secondary phenomenon and that soot is primarily transported by advection of the fluid in a turbulent flame. The effect of hydrogen dilution on the soot formation and transport process is also studied. It is noted that the decay of soot volume fraction and flame length with hydrogen addition follows trends observed in laminar sooting flame measurements. While hydrogen enhances mixing shown by the laminar flamelet solutions, the mixing effect does not significantly contribute to differential molecular diffusion effects in the soot nucleation regions downstream of the flame and has a negligible effect on soot transport. The sensitivity of computations of soot volume fraction towards the chemical reaction mechanism is shown. It is concluded that modeling reaction pathways of C3 and C4 species that lead up to Polycyclic Aromatic Hydrocarbon (PAH) molecule formation is paramount for accurate predictions of soot in the flame. (Abstract shortened by ProQuest.).

Effects of Weightlessness on Human Fluid and Electrolyte Physiology

NASA Technical Reports Server (NTRS)

Leach, Carolyn S.; Johnson, Philip C., Jr.

1991-01-01

The changes that occur in human fluid and electrolyte physiology during the acute and adaptive phases of adaptation to spaceflight are summarized. A number of questions remain to be answered. At a time when plasma volume and extracellular fluid volume are contracted and salt and water intake is unrestricted. ADH does not correct the volume deficit and serum sodium decreases. Change in secretion or activity of a natriuretic factor during spaceflight is one possible explanation. Recent identification of a polypeptide hormone produced in cardiac muscle cells which is natiuretic, is hypotensive, and has an inhibitory effect on renin and aldosterone secretion has renewed interest in the role of a natriuretic factor. The role of this atrial natriuretic factor (ANF) in both long- and short-term variation in extracellular volumes and in the inability of the kidney to bring about an escape from the sodium-retaining state accompanying chronic cardiac dysfunction makes it reasonable to look for a role of ANF in the regulation of sodium during exposure to microgravity. Prostaglandin-E is another hormone that may antagonize the action of ADH. Assays of these hormones will be performed on samples from crew members in the future.

Assessing the effects of ketorolac and acetazolamide on macular thickness by optical coherence tomography following cataract surgery.

PubMed

Turan-Vural, Ece; Halili, Elvin; Serin, Didem

2014-06-01

We aimed to evaluate the efficacy of topical ketorolac 0.5 % solution and oral acetazolamide 250 mg/day delivery during the first month after uneventful phacoemulsification surgery by measuring the macular thickness using optical coherence tomography. Our nonmasked randomized prospective study comprised 87 eyes of 80 patients. Complete follow-up was achieved on 84 eyes of 77 eligible patients. Postoperatively, the patients were divided into three groups. One group received ketorolac 0.5 %, the other group received acetazolamide 250 mg/day, and the control group was given no agent. Macular thickness and volume were measured at 1 week and 1 month after surgery by optical coherence tomography. Foveal thickness, parafoveal thickness, and perifoveal thickness were determined to be significantly elevated at postoperative 1 week and 1 month in the control group. Foveal, perifoveal, and parafoveal volumes were also significantly high at postoperative week 1 and month 1 in the control group. There was no significant difference between the ketorolac and acetazolamide groups. The correlation analysis between best-corrected visual acuity, and volume and thickness revealed a negative correlation in the acetazolamide group. Use of acetazolamide after cataract surgery is as effective as ketorolac on macular thickness and volume.

Principles of Considering the Effect of the Limited Volume of a System on Its Thermodynamic State

NASA Astrophysics Data System (ADS)

Tovbin, Yu. K.

2018-01-01

The features of a system with a finite volume that affect its thermodynamic state are considered in comparison to describing small bodies in macroscopic phases. Equations for unary and pair distribution functions are obtained using difference derivatives of a discrete statistical sum. The structure of the equation for the free energy of a system consisting of an ensemble of volume-limited regions with different sizes and a full set of equations describing a macroscopic polydisperse system are discussed. It is found that the equations can be applied to molecular adsorption on small faces of microcrystals, to bound and isolated pores of a polydisperse material, and to describe the spinodal decomposition of a fluid in brief periods of time and high supersaturations of the bulk phase when each local region functions the same on average. It is shown that as the size of a system diminishes, corrections must be introduced for the finiteness of the system volume and fluctuations of the unary and pair distribution functions.

A modified elastance model to control mock ventricles in real-time: numerical and experimental validation.

PubMed

Colacino, Francesco Maria; Moscato, Francesco; Piedimonte, Fabio; Danieli, Guido; Nicosia, Salvatore; Arabia, Maurizio

2008-01-01

This article describes an elastance-based mock ventricle able to reproduce the correct ventricular pressure-volume relationship and its correct interaction with the hydraulic circuit connected to it. A real-time control of the mock ventricle was obtained by a new left ventricular mathematical model including resistive and inductive terms added to the classical Suga-Sagawa elastance model throughout the whole cardiac cycle. A valved piston pump was used to mimic the left ventricle. The pressure measured into the pump chamber was fed back into the mathematical model and the calculated reference left ventricular volume was used to drive the piston. Results show that the classical model is very sensitive to pressure disturbances, especially during the filling phase, while the modified model is able to filter out the oscillations thus eliminating their detrimental effects. The presented model is thus suitable to control mock ventricles in real-time, where sudden pressure disturbances represent a key issue and are not negligible. This real-time controlled mock ventricle is able to reproduce the elastance mechanism of a natural ventricle by mimicking its preload (mean atrial pressure) and afterload (mean aortic pressure) sensitivity, i.e., the Starling law. Therefore, it can be used for designing and testing cardiovascular prostheses due to its capability to reproduce the correct ventricle-vascular system interaction.

Automatic motion correction for in vivo human skin optical coherence tomography angiography through combined rigid and nonrigid registration

NASA Astrophysics Data System (ADS)

Wei, David Wei; Deegan, Anthony J.; Wang, Ruikang K.

2017-06-01

When using optical coherence tomography angiography (OCTA), the development of artifacts due to involuntary movements can severely compromise the visualization and subsequent quantitation of tissue microvasculatures. To correct such an occurrence, we propose a motion compensation method to eliminate artifacts from human skin OCTA by means of step-by-step rigid affine registration, rigid subpixel registration, and nonrigid B-spline registration. To accommodate this remedial process, OCTA is conducted using two matching all-depth volume scans. Affine transformation is first performed on the large vessels of the deep reticular dermis, and then the resulting affine parameters are applied to all-depth vasculatures with a further subpixel registration to refine the alignment between superficial smaller vessels. Finally, the coregistration of both volumes is carried out to result in the final artifact-free composite image via an algorithm based upon cubic B-spline free-form deformation. We demonstrate that the proposed method can provide a considerable improvement to the final en face OCTA images with substantial artifact removal. In addition, the correlation coefficients and peak signal-to-noise ratios of the corrected images are evaluated and compared with those of the original images, further validating the effectiveness of the proposed method. We expect that the proposed method can be useful in improving qualitative and quantitative assessment of the OCTA images of scanned tissue beds.

Automatic motion correction for in vivo human skin optical coherence tomography angiography through combined rigid and nonrigid registration.

PubMed

Wei, David Wei; Deegan, Anthony J; Wang, Ruikang K

2017-06-01

When using optical coherence tomography angiography (OCTA), the development of artifacts due to involuntary movements can severely compromise the visualization and subsequent quantitation of tissue microvasculatures. To correct such an occurrence, we propose a motion compensation method to eliminate artifacts from human skin OCTA by means of step-by-step rigid affine registration, rigid subpixel registration, and nonrigid B-spline registration. To accommodate this remedial process, OCTA is conducted using two matching all-depth volume scans. Affine transformation is first performed on the large vessels of the deep reticular dermis, and then the resulting affine parameters are applied to all-depth vasculatures with a further subpixel registration to refine the alignment between superficial smaller vessels. Finally, the coregistration of both volumes is carried out to result in the final artifact-free composite image via an algorithm based upon cubic B-spline free-form deformation. We demonstrate that the proposed method can provide a considerable improvement to the final en face OCTA images with substantial artifact removal. In addition, the correlation coefficients and peak signal-to-noise ratios of the corrected images are evaluated and compared with those of the original images, further validating the effectiveness of the proposed method. We expect that the proposed method can be useful in improving qualitative and quantitative assessment of the OCTA images of scanned tissue beds.

The influence of CT based attenuation correction on PET/CT registration: an evaluation study

NASA Astrophysics Data System (ADS)

Yaniv, Ziv; Wong, Kenneth H.; Banovac, Filip; Levy, Elliot; Cleary, Kevin

2007-03-01

We are currently developing a PET/CT based navigation system for guidance of biopsies and radiofrequency ablation (RFA) of early stage hepatic tumors. For these procedures, combined PET/CT data can potentially improve current interventions. The diagnostic efficacy of biopsies can potentially be improved by accurately targeting the region within the tumor that exhibits the highest metabolic activity. For RFA procedures the system can potentially enable treatment of early stage tumors, targeting tumors before structural abnormalities are clearly visible on CT. In both cases target definition is based on the metabolic data (PET), and navigation is based on the spatial data (CT), making the system highly dependent upon accurate spatial alignment between these data sets. In our institute all clinical data sets include three image volumes: one CT, and two PET volumes, with and without CT-based attenuation correction. This paper studies the effect of the CT-based attenuation correction on the registration process. From comparing the pairs of registrations from five data sets we observe that the point motion magnitude difference between registrations is on the same scale as the point motion magnitude in each one of the registrations, and that visual inspection cannot identify this discrepancy. We conclude that using non-rigid registration to align the PET and CT data sets is too variable, and most likely does not provide sufficient accuracy for interventional procedures.

The use of polymethyl-methacrylate (Artecoll) as an adjunct to facial reconstruction

PubMed Central

Mok, David; Schwarz, Jorge

2004-01-01

BACKGROUND: Injectable polymethyl-methacrylate (PMMA) microspheres, or Artecoll, has been used for the last few years in aesthetic surgery as long-term tissue filler for the correction of wrinkles and for lip augmentation. This paper presents three cases of the use of PMMA microsphere injection for reconstructive patients with defects of varying etiologies. These cases provide examples of a novel adjunct to the repertoire of the reconstructive surgeon. OBJECTIVES: To evaluate the effectiveness (short- and long-term) of PMMA injection for the correction of small soft tissue defects of the face. METHODS: Three case histories are presented. They include the origin of the defect; previous reconstructions of the defect; and area, volume, timing and technical particularities of PMMA administration. RESULTS: All three cases showed improvement of the defect with the PMMA injection with respect to both objective evidence and patient satisfaction. The improvements can still be seen after several years. CONCLUSIONS: PMMA microsphere injection can be effectively used to correct selected small facial defects in reconstructive cases and the results are long lasting. PMID:24115873

EM Bias-Correction for Ice Thickness and Surface Roughness Retrievals over Rough Deformed Sea Ice

NASA Astrophysics Data System (ADS)

Li, L.; Gaiser, P. W.; Allard, R.; Posey, P. G.; Hebert, D. A.; Richter-Menge, J.; Polashenski, C. M.

2016-12-01

The very rough ridge sea ice accounts for significant percentage of total ice areas and even larger percentage of total volume. The commonly used Radar altimeter surface detection techniques are empirical in nature and work well only over level/smooth sea ice. Rough sea ice surfaces can modify the return waveforms, resulting in significant Electromagnetic (EM) bias in the estimated surface elevations, and thus large errors in the ice thickness retrievals. To understand and quantify such sea ice surface roughness effects, a combined EM rough surface and volume scattering model was developed to simulate radar returns from the rough sea ice `layer cake' structure. A waveform matching technique was also developed to fit observed waveforms to a physically-based waveform model and subsequently correct the roughness induced EM bias in the estimated freeboard. This new EM Bias Corrected (EMBC) algorithm was able to better retrieve surface elevations and estimate the surface roughness parameter simultaneously. In situ data from multi-instrument airborne and ground campaigns were used to validate the ice thickness and surface roughness retrievals. For the surface roughness retrievals, we applied this EMBC algorithm to co-incident LiDAR/Radar measurements collected during a Cryosat-2 under-flight by the NASA IceBridge missions. Results show that not only does the waveform model fit very well to the measured radar waveform, but also the roughness parameters derived independently from the LiDAR and radar data agree very well for both level and deformed sea ice. For sea ice thickness retrievals, validation based on in-situ data from the coordinated CRREL/NRL field campaign demonstrates that the physically-based EMBC algorithm performs fundamentally better than the empirical algorithm over very rough deformed sea ice, suggesting that sea ice surface roughness effects can be modeled and corrected based solely on the radar return waveforms.

A novel partial volume effects correction technique integrating deconvolution associated with denoising within an iterative PET image reconstruction

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

Merlin, Thibaut, E-mail: thibaut.merlin@telecom-bretagne.eu; Visvikis, Dimitris; Fernandez, Philippe

2015-02-15

Purpose: Partial volume effect (PVE) plays an important role in both qualitative and quantitative PET image accuracy, especially for small structures. A previously proposed voxelwise PVE correction method applied on PET reconstructed images involves the use of Lucy–Richardson deconvolution incorporating wavelet-based denoising to limit the associated propagation of noise. The aim of this study is to incorporate the deconvolution, coupled with the denoising step, directly inside the iterative reconstruction process to further improve PVE correction. Methods: The list-mode ordered subset expectation maximization (OSEM) algorithm has been modified accordingly with the application of the Lucy–Richardson deconvolution algorithm to the current estimationmore » of the image, at each reconstruction iteration. Acquisitions of the NEMA NU2-2001 IQ phantom were performed on a GE DRX PET/CT system to study the impact of incorporating the deconvolution inside the reconstruction [with and without the point spread function (PSF) model] in comparison to its application postreconstruction and to standard iterative reconstruction incorporating the PSF model. The impact of the denoising step was also evaluated. Images were semiquantitatively assessed by studying the trade-off between the intensity recovery and the noise level in the background estimated as relative standard deviation. Qualitative assessments of the developed methods were additionally performed on clinical cases. Results: Incorporating the deconvolution without denoising within the reconstruction achieved superior intensity recovery in comparison to both standard OSEM reconstruction integrating a PSF model and application of the deconvolution algorithm in a postreconstruction process. The addition of the denoising step permitted to limit the SNR degradation while preserving the intensity recovery. Conclusions: This study demonstrates the feasibility of incorporating the Lucy–Richardson deconvolution associated with a wavelet-based denoising in the reconstruction process to better correct for PVE. Future work includes further evaluations of the proposed method on clinical datasets and the use of improved PSF models.« less

Cumulative adversity and smaller gray matter volume in medial prefrontal, anterior cingulate, and insula regions.

PubMed

Ansell, Emily B; Rando, Kenneth; Tuit, Keri; Guarnaccia, Joseph; Sinha, Rajita

2012-07-01

Cumulative adversity and stress are associated with risk of psychiatric disorders. While basic science studies show repeated and chronic stress effects on prefrontal and limbic neurons, human studies examining cumulative stress and effects on brain morphology are rare. Thus, we assessed whether cumulative adversity is associated with differences in gray matter volume, particularly in regions regulating emotion, self-control, and top-down processing in a community sample. One hundred three healthy community participants, aged 18 to 48 and 68% male, completed interview assessment of cumulative adversity and a structural magnetic resonance imaging protocol. Whole-brain voxel-based-morphometry analysis was performed adjusting for age, gender, and total intracranial volume. Cumulative adversity was associated with smaller volume in medial prefrontal cortex (PFC), insular cortex, and subgenual anterior cingulate regions (familywise error corrected, p < .001). Recent stressful life events were associated with smaller volume in two clusters: the medial PFC and the right insula. Life trauma was associated with smaller volume in the medial PFC, anterior cingulate, and subgenual regions. The interaction of greater subjective chronic stress and greater cumulative life events was associated with smaller volume in the orbitofrontal cortex, insula, and anterior and subgenual cingulate regions. Current results demonstrate that increasing cumulative exposure to adverse life events is associated with smaller gray matter volume in key prefrontal and limbic regions involved in stress, emotion and reward regulation, and impulse control. These differences found in community participants may serve to mediate vulnerability to depression, addiction, and other stress-related psychopathology. Copyright © 2012 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

Cumulative Adversity and Smaller Gray Matter Volume in Medial Prefrontal, Anterior Cingulate, and Insula Regions

PubMed Central

Ansell, Emily B.; Rando, Kenneth; Tuit, Keri; Guarnaccia, Joseph; Sinha, Rajita

2012-01-01

Background Cumulative adversity and stress are associated with risk of psychiatric disorders. While basic science studies show repeated and chronic stress effects on prefrontal and limbic neurons, human studies examining cumulative stress and effects on brain morphology are rare. Thus, we assessed whether cumulative adversity is associated with differences in gray matter volume, particularly in regions regulating emotion, self-control, and top-down processing in a community sample. Methods One hundred three healthy community participants, aged 18 to 48 and 68% male, completed interview assessment of cumulative adversity and a structural magnetic resonance imaging protocol. Whole-brain voxel-based-morphometry analysis was performed adjusting for age, gender, and total intracranial volume. Results Cumulative adversity was associated with smaller volume in medial prefrontal cortex (PFC), insular cortex, and subgenual anterior cingulate regions (familywise error corrected, p <.001). Recent stressful life events were associated with smaller volume in two clusters: the medial PFC and the right insula. Life trauma was associated with smaller volume in the medial PFC, anterior cingulate, and subgenual regions. The interaction of greater subjective chronic stress and greater cumulative life events was associated with smaller volume in the orbitofrontal cortex, insula, and anterior and subgenual cingulate regions. Conclusions Current results demonstrate that increasing cumulative exposure to adverse life events is associated with smaller gray matter volume in key prefrontal and limbic regions involved in stress, emotion and reward regulation, and impulse control. These differences found in community participants may serve to mediate vulnerability to depression, addiction, and other stress-related psychopathology. PMID:22218286

Decreased frontal white-matter volume in chronic substance abuse.

PubMed

Schlaepfer, Thomas E; Lancaster, Eric; Heidbreder, Rebecca; Strain, Eric C; Kosel, Markus; Fisch, Hans-Ulrich; Pearlson, Godfrey D

2006-04-01

There is quite a body of work assessing functional brain changes in chronic substance abuse, much less is known about structural brain abnormalities in this patient population. In this study we used magnetic resonance imaging (MRI) to determine if structural brain differences exist in patients abusing illicit drugs compared to healthy controls. Sixteen substance abusers who abused heroin, cocaine and cannabis but not alcohol and 16 age-, sex- and race-matched controls were imaged on a MRI scanner. Contiguous, 5-mm-thick axial slices were acquired with simultaneous T2 and proton density sequences. Volumes were estimated for total grey and white matter, frontal grey and white matter, ventricles, and CSF using two different methods: a conventional segmentation and a stereological method based on the Cavalieri principle. Overall brain volume differences were corrected for by expressing the volumes of interest as a percentage of total brain volume. Volume measures obtained with the two methods were highly correlated (r=0.65, p<0.001). Substance abusers had significantly less frontal white-matter volume percentage than controls. There were no significant differences in any of the other brain volumes measured. This difference in frontal lobe white matter might be explained by a direct neurotoxic effect of drug use on white matter, a pre-existing abnormality in the development of the frontal lobe or a combination of both effects. This last explanation might be compelling based on the fact that newer concepts on shared aspects of some neuropsychiatric disorders focus on the promotion and inhibition of the process of myelination throughout brain development and subsequent degeneration.

Hindrance Velocity Model for Phase Segregation in Suspensions of Poly-dispersed Randomly Oriented Spheroids

NASA Astrophysics Data System (ADS)

Faroughi, S. A.; Huber, C.

2015-12-01

Crystal settling and bubbles migration in magmas have significant effects on the physical and chemical evolution of magmas. The rate of phase segregation is controlled by the force balance that governs the migration of particles suspended in the melt. The relative velocity of a single particle or bubble in a quiescent infinite fluid (melt) is well characterized; however, the interplay between particles or bubbles in suspensions and emulsions and its effect on their settling/rising velocity remains poorly quantified. We propose a theoretical model for the hindered velocity of non-Brownian emulsions of nondeformable droplets, and suspensions of spherical solid particles in the creeping flow regime. The model is based on three sets of hydrodynamic corrections: two on the drag coefficient experienced by each particle to account for both return flow and Smoluchowski effects and a correction on the mixture rheology to account for nonlocal interactions between particles. The model is then extended for mono-disperse non-spherical solid particles that are randomly oriented. The non-spherical particles are idealized as spheroids and characterized by their aspect ratio. The poly-disperse nature of natural suspensions is then taken into consideration by introducing an effective volume fraction of particles for each class of mono-disperse particles sizes. Our model is tested against new and published experimental data over a wide range of particle volume fraction and viscosity ratios between the constituents of dispersions. We find an excellent agreement between our model and experiments. We also show two significant applications for our model: (1) We demonstrate that hindered settling can increase mineral residence time by up to an order of magnitude in convecting magma chambers. (2) We provide a model to correct for particle interactions in the conventional hydrometer test to estimate the particle size distribution in soils. Our model offers a greatly improved agreement with the results obtained with direct measurement methods such as laser diffraction.

Towards a universal method for calculating hydration free energies: a 3D reference interaction site model with partial molar volume correction.

PubMed

Palmer, David S; Frolov, Andrey I; Ratkova, Ekaterina L; Fedorov, Maxim V

2010-12-15

We report a simple universal method to systematically improve the accuracy of hydration free energies calculated using an integral equation theory of molecular liquids, the 3D reference interaction site model. A strong linear correlation is observed between the difference of the experimental and (uncorrected) calculated hydration free energies and the calculated partial molar volume for a data set of 185 neutral organic molecules from different chemical classes. By using the partial molar volume as a linear empirical correction to the calculated hydration free energy, we obtain predictions of hydration free energies in excellent agreement with experiment (R = 0.94, σ = 0.99 kcal mol (- 1) for a test set of 120 organic molecules).

DETERMINATION OF THE SPEED OF SOUND ALONG THE HUGONIOT IN A SHOCKED MATERIAL

DTIC Science & Technology

2017-04-25

correctly predict higher speeds of sound for the higher energy shocked states. The approximations of higher shock pressures diverge progressively...List 11 FIGURES 1 Copper Hugoniot pressure-specific volume plane 4 2 Copper Hugoniot energy -specific volume plane 4 3 Comparison between rate of...volume and energy are being used. = (, ) Then by the chain rule: = | + | Dividing by dv

Calibration of volume and component biomass equations for Douglas-fir and lodgepole pine in Western Oregon forests

Treesearch

Krishna P. Poudel; Temesgen Hailemariam

2016-01-01

Using data from destructively sampled Douglas-fir and lodgepole pine trees, we evaluated the performance of regional volume and component biomass equations in terms of bias and RMSE. The volume and component biomass equations were calibrated using three different adjustment methods that used: (a) a correction factor based on ordinary least square regression through...

Partial volume correction of magnetic resonance spectroscopic imaging

NASA Astrophysics Data System (ADS)

Lu, Yao; Wu, Dee; Magnotta, Vincent A.

2007-03-01

The ability to study the biochemical composition of the brain is becoming important to better understand neurodegenerative and neurodevelopmental disorders. Magnetic Resonance Spectroscopy (MRS) can non-invasively provide quantification of brain metabolites in localized regions. The reliability of MRS is limited in part due to partial volume artifacts. This results from the relatively large voxels that are required to acquire sufficient signal-to-noise ratios for the studies. Partial volume artifacts result when a MRS voxel contains a mixture of tissue types. Concentrations of metabolites vary from tissue to tissue. When a voxel contains a heterogeneous tissue composition, the spectroscopic signal acquired from this voxel will consist of the signal from different tissues making reliable measurements difficult. We have developed a novel tool for the estimation of partial volume tissue composition within MRS voxels thus allowing for the correction of partial volume artifacts. In addition, the tool can localize MR spectra to anatomical regions of interest. The tool uses tissue classification information acquired as part of a structural MR scan for the same subject. The tissue classification information is co-registered with the spectroscopic data. The user can quantify the partial volume composition of each voxel and use this information as covariates for metabolite concentrations.

Fornix Under Water? Ventricular Enlargement Biases Forniceal Diffusion Magnetic Resonance Imaging Indices in Anorexia Nervosa.

PubMed

Kaufmann, Lisa-Katrin; Baur, Volker; Hänggi, Jürgen; Jäncke, Lutz; Piccirelli, Marco; Kollias, Spyros; Schnyder, Ulrich; Pasternak, Ofer; Martin-Soelch, Chantal; Milos, Gabriella

2017-07-01

Acute anorexia nervosa (AN) is characterized by reduced brain mass and corresponding increased sulcal and ventricular cerebrospinal fluid. Recent studies of white matter using diffusion tensor imaging consistently identified alterations in the fornix, such as reduced fractional anisotropy (FA). However, because the fornix penetrates the ventricles, it is prone to cerebrospinal fluid-induced partial volume effects that interfere with a valid assessment of FA. We investigated the hypothesis that in the acute stage of AN, FA of the fornix is markedly affected by ventricular volumes. First, using diffusion tensor imaging data we established the inverse associations between forniceal FA and volumes of the third and lateral ventricles in a prestudy with 32 healthy subjects to demonstrate the strength of ventricular influence on forniceal FA independent of AN. Second, we investigated a sample of 25 acute AN patients and 25 healthy control subjects. Using ventricular volumes as covariates markedly reduced the group effect of forniceal FA, even with tract-based spatial statistics focusing only on the center of the fornix. In addition, after correcting for free water on voxel level, the group differences in forniceal FA between AN patients and controls disappeared completely. It is unlikely that microstructural changes affecting FA occurred in the fornix of AN patients. Previously identified alterations in acute AN may have been biased by partial volume effects and the proposed central role of this structure in the pathophysiology may need to be reconsidered. Future studies on white matter alterations in AN should carefully deal with partial volume effects. Copyright © 2017 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

Cumulative Effects of Foraging Behavior and Social Dominance on Brain Development in a Facultatively Social Bee (Ceratina australensis).

PubMed

Rehan, Sandra M; Bulova, Susan J; O'Donnell, Sean

2015-01-01

In social insects, both task performance (foraging) and dominance are associated with increased brain investment, particularly in the mushroom bodies. Whether and how these factors interact is unknown. Here we present data on a system where task performance and social behavior can be analyzed simultaneously: the small carpenter bee Ceratina australensis. We show that foraging and dominance have separate and combined cumulative effects on mushroom body calyx investment. Female C. australensis nest solitarily and socially in the same populations at the same time. Social colonies comprise two sisters: the social primary, which monopolizes foraging and reproduction, and the social secondary, which is neither a forager nor reproductive but rather remains at the nest as a guard. We compare the brains of solitary females that forage and reproduce but do not engage in social interactions with those of social individuals while controlling for age, reproductive status, and foraging experience. Mushroom body calyx volume was positively correlated with wing wear, a proxy for foraging experience. We also found that, although total brain volume did not vary among reproductive strategies (solitary vs. social nesters), socially dominant primaries had larger mushroom body calyx volumes (corrected for both brain and body size variation) than solitary females; socially subordinate secondaries (that are neither dominant nor foragers) had the least-developed mushroom body calyces. These data demonstrate that sociality itself does not explain mushroom body volume; however, achieving and maintaining dominance status in a group was associated with mushroom body calyx enlargement. Dominance and foraging effects were cumulative; dominant social primary foragers had larger mushroom body volumes than solitary foragers, and solitary foragers had larger mushroom body volumes than nonforaging social secondary guards. This is the first evidence for cumulative effects on brain development by dominance and task performance.

Joint correction of respiratory motion artifact and partial volume effect in lung/thoracic PET/CT imaging.

PubMed

Chang, Guoping; Chang, Tingting; Pan, Tinsu; Clark, John W; Mawlawi, Osama R

2010-12-01

Respiratory motion artifacts and partial volume effects (PVEs) are two degrading factors that affect the accuracy of image quantification in PET/CT imaging. In this article, the authors propose a joint motion and PVE correction approach (JMPC) to improve PET quantification by simultaneously correcting for respiratory motion artifacts and PVE in patients with lung/thoracic cancer. The objective of this article is to describe this approach and evaluate its performance using phantom and patient studies. The proposed joint correction approach incorporates a model of motion blurring, PVE, and object size/shape. A motion blurring kernel (MBK) is then estimated from the deconvolution of the joint model, while the activity concentration (AC) of the tumor is estimated from the normalization of the derived MBK. To evaluate the performance of this approach, two phantom studies and eight patient studies were performed. In the phantom studies, two motion waveforms-a linear sinusoidal and a circular motion-were used to control the motion of a sphere, while in the patient studies, all participants were instructed to breathe regularly. For the phantom studies, the resultant MBK was compared to the true MBK by measuring a correlation coefficient between the two kernels. The measured sphere AC derived from the proposed method was compared to the true AC as well as the ACs in images exhibiting PVE only and images exhibiting both PVE and motion blurring. For the patient studies, the resultant MBK was compared to the motion extent derived from a 4D-CT study, while the measured tumor AC was compared to the AC in images exhibiting both PVE and motion blurring. For the phantom studies, the estimated MBK approximated the true MBK with an average correlation coefficient of 0.91. The tumor ACs following the joint correction technique were similar to the true AC with an average difference of 2%. Furthermore, the tumor ACs on the PVE only images and images with both motion blur and PVE effects were, on average, 75% and 47.5% (10%) of the true AC, respectively, for the linear (circular) motion phantom study. For the patient studies, the maximum and mean AC/SUV on the PET images following the joint correction are, on average, increased by 125.9% and 371.6%, respectively, when compared to the PET images with both PVE and motion. The motion extents measured from the derived MBK and 4D-CT exhibited an average difference of 1.9 mm. The proposed joint correction approach can improve the accuracy of PET quantification by simultaneously compensating for the respiratory motion artifacts and PVE in lung/thoracic PET/CT imaging.

Database of normal human cerebral blood flow measured by SPECT: II. Quantification of I-123-IMP studies with ARG method and effects of partial volume correction.

PubMed

Inoue, Kentaro; Ito, Hiroshi; Shidahara, Miho; Goto, Ryoi; Kinomura, Shigeo; Sato, Kazunori; Taki, Yasuyuki; Okada, Ken; Kaneta, Tomohiro; Fukuda, Hiroshi

2006-02-01

The limited spatial resolution of SPECT causes a partial volume effect (PVE) and can lead to the significant underestimation of regional tracer concentration in the small structures surrounded by a low tracer concentration, such as the cortical gray matter of an atrophied brain. The aim of the present study was to determine, using 123I-IMP and SPECT, normal CBF of elderly subjects with and without PVE correction (PVC), and to determine regional differences in the effect of PVC and their association with the regional tissue fraction of the brain. Quantitative CBF SPECT using 123I-IMP was performed in 33 healthy elderly subjects (18 males, 15 females, 54-74 years old) using the autoradiographic method. We corrected CBF for PVE using segmented MR images, and analyzed quantitative CBF and regional differences in the effect of PVC using tissue fractions of gray matter (GM) and white matter (WM) in regions of interest (ROIs) placed on the cortical and subcortical GM regions and deep WM regions. The mean CBF in GM-ROIs were 31.7 +/- 6.6 and 41.0 +/- 8.1 ml/100 g/min for males and females, and in WM-ROIs, 18.2 +/- 0.7 and 22.9 +/- 0.8 ml/100 g/min for males and females, respectively. The mean CBF in GM-ROIs after PVC were 50.9 +/- 12.8 and 65.8 +/- 16.1 ml/100 g/min for males and females, respectively. There were statistically significant differences in the effect of PVC among ROIs, but not between genders. The effect of PVC was small in the cerebellum and parahippocampal gyrus, and it was large in the superior frontal gyrus, superior parietal lobule and precentral gyrus. Quantitative CBF in GM recovered significantly, but did not reach values as high as those obtained by invasive methods or in the H2(15)O PET study that used PVC. There were significant regional differences in the effect of PVC, which were considered to result from regional differences in GM tissue fraction, which is more reduced in the frontoparietal regions in the atrophied brain of the elderly.

Modeling of stress distributions on the microstructural level in Alloy 600

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

Kozaczek, K.J.; Petrovic, B.G.; Ruud, C.O.

1995-04-01

Stress distribution in a random polycrystalline material (Alloy 600) was studied using a topologically correct microstructural model. Distributions of von Mises and hydrostatic stresses at the grain vertices, which could be important in intergranular stress corrosion cracking, were analyzed as functions of microstructure, grain orientations and loading conditions. Grain size, shape, and orientation had a more pronounced effect on stress distribution than loading conditions. At grain vertices the stress concentration factor was higher for hydrostatic stress (1.7) than for von Mises stress (1.5). The stress/strain distribution in the volume (grain interiors) is a normal distribution and does not depend onmore » the location of the studied material volume i.e., surface vs/bulk. The analysis of stress distribution in the volume showed the von Mises stress concentration of 1.75 and stress concentration of 2.2 for the hydrostatic pressure. The observed stress concentration is high enough to cause localized plastic microdeformation, even when the polycrystalline aggregate is in the macroscopic elastic regime. Modeling of stresses and strains in polycrystalline materials can identify the microstructures (grain size distributions, texture) intrinsically susceptible to stress/strain concentrations and justify the correctness of applied stress state during the stress corrosion cracking tests. Also, it supplies the information necessary to formulate the local failure criteria and interpret of nondestructive stress measurements.« less

Effects of operator splitting and low Mach-number correction in turbulent mixing transition simulations

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

Grinstein, F. F.; Saenz, J. A.; Dolence, J. C.

Inmore » this paper, transition and turbulence decay with the Taylor–Green vortex have been effectively used to demonstrate emulation of high Reynolds-number ( R e ) physical dissipation through numerical convective effects of various non-oscillatory finite-volume algorithms for implicit large eddy simulation (ILES), e.g. using the Godunov-based Eulerian adaptive mesh refinement code xRAGE. The inverse-chevron shock tube experiment simulations have been also used to assess xRAGE based ILES for shock driven turbulent mixing, compared with available simulation and laboratory data. The previous assessments are extended to evaluate new directionally-unsplit high-order algorithms in xRAGE, including a correction to address the well-known issue of excessive numerical diffusion of shock-capturing (e.g., Godunov-type) schemes for low Mach numbers. The unsplit options for hydrodynamics in xRAGE are discussed in detail, followed by fundamental tests with representative shock problems. Basic issues of transition to turbulence and turbulent mixing are discussed, and results of simulations of high- R e turbulent flow and mixing in canonical test cases are reported. Finally, compared to the directional-split cases, and for each grid resolution considered, unsplit results exhibit transition to turbulence with much higher effective R e —and significantly more so with the low Mach number correction.« less

Effects of operator splitting and low Mach-number correction in turbulent mixing transition simulations

DOE PAGES

Grinstein, F. F.; Saenz, J. A.; Dolence, J. C.; ...

2018-06-07

Inmore » this paper, transition and turbulence decay with the Taylor–Green vortex have been effectively used to demonstrate emulation of high Reynolds-number ( R e ) physical dissipation through numerical convective effects of various non-oscillatory finite-volume algorithms for implicit large eddy simulation (ILES), e.g. using the Godunov-based Eulerian adaptive mesh refinement code xRAGE. The inverse-chevron shock tube experiment simulations have been also used to assess xRAGE based ILES for shock driven turbulent mixing, compared with available simulation and laboratory data. The previous assessments are extended to evaluate new directionally-unsplit high-order algorithms in xRAGE, including a correction to address the well-known issue of excessive numerical diffusion of shock-capturing (e.g., Godunov-type) schemes for low Mach numbers. The unsplit options for hydrodynamics in xRAGE are discussed in detail, followed by fundamental tests with representative shock problems. Basic issues of transition to turbulence and turbulent mixing are discussed, and results of simulations of high- R e turbulent flow and mixing in canonical test cases are reported. Finally, compared to the directional-split cases, and for each grid resolution considered, unsplit results exhibit transition to turbulence with much higher effective R e —and significantly more so with the low Mach number correction.« less

It Is Chloride Depletion Alkalosis, Not Contraction Alkalosis

PubMed Central

Galla, John H.

2012-01-01

Maintenance of metabolic alkalosis generated by chloride depletion is often attributed to volume contraction. In balance and clearance studies in rats and humans, we showed that chloride repletion in the face of persisting alkali loading, volume contraction, and potassium and sodium depletion completely corrects alkalosis by a renal mechanism. Nephron segment studies strongly suggest the corrective response is orchestrated in the collecting duct, which has several transporters integral to acid-base regulation, the most important of which is pendrin, a luminal Cl/HCO3− exchanger. Chloride depletion alkalosis should replace the notion of contraction alkalosis. PMID:22223876

Robust incremental compensation of the light attenuation with depth in 3D fluorescence microscopy.

PubMed

Kervrann, C; Legland, D; Pardini, L

2004-06-01

Summary Fluorescent signal intensities from confocal laser scanning microscopes (CLSM) suffer from several distortions inherent to the method. Namely, layers which lie deeper within the specimen are relatively dark due to absorption and scattering of both excitation and fluorescent light, photobleaching and/or other factors. Because of these effects, a quantitative analysis of images is not always possible without correction. Under certain assumptions, the decay of intensities can be estimated and used for a partial depth intensity correction. In this paper we propose an original robust incremental method for compensating the attenuation of intensity signals. Most previous correction methods are more or less empirical and based on fitting a decreasing parametric function to the section mean intensity curve computed by summing all pixel values in each section. The fitted curve is then used for the calculation of correction factors for each section and a new compensated sections series is computed. However, these methods do not perfectly correct the images. Hence, the algorithm we propose for the automatic correction of intensities relies on robust estimation, which automatically ignores pixels where measurements deviate from the decay model. It is based on techniques adopted from the computer vision literature for image motion estimation. The resulting algorithm is used to correct volumes acquired in CLSM. An implementation of such a restoration filter is discussed and examples of successful restorations are given.

SeaWinds Scatterometer Wind Vector Retrievals Within Hurricanes Using AMSR and NEXRAD to Perform Corrections for Precipitation Effects: Comparison of AMSR and NEXRAD Retrievals of Rain

NASA Technical Reports Server (NTRS)

Weissman, David E.; Hristova-Veleva, Svetla; Callahan, Philip

2006-01-01

The opportunity provided by satellite scatterometers to measure ocean surface winds in strong storms and hurricanes is diminished by the errors in the received backscatter (SIGMA-0) caused by the attenuation, scattering and surface roughening produced by heavy rain. Providing a good rain correction is a very challenging problem, particularly at Ku band (13.4 GHz) where rain effects are strong. Corrections to the scatterometer measurements of ocean surface winds can be pursued with either of two different methods: empirical or physical modeling. The latter method is employed in this study because of the availability of near simultaneous and collocated measurements provided by the MIDORI-II suite of instruments. The AMSR was designed to measure atmospheric water-related parameters on a spatial scale comparable to the SeaWinds scatterometer. These quantities can be converted into volumetric attenuation and scattering at the Ku-band frequency of SeaWinds. Optimal estimates of the volume backscatter and attenuation require a knowledge of the three dimensional distribution of reflectivity on a scale comparable to that of the precipitation. Studies selected near the US coastline enable the much higher resolution NEXRAD reflectivity measurements evaluate the AMSR estimates. We are also conducting research into the effects of different beam geometries and nonuniform beamfilling of precipitation within the field-of-view of the AMSR and the scatterometer. Furthermore, both AMSR and NEXRAD estimates of atmospheric correction can be used to produce corrected SIGMA-0s, which are then input to the JPL wind retrieval algorithm.

Assessment of BoneTtissue Mineralization by Conventional X-ray Microcomputed tomography: Comparison with Synchrotron Radiation Microcomputed Tomography and Ash Measurements

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

Kazakia,G.; Burghardt, A.; Cheung, S.

2008-01-01

Assessment of bone tissue mineral density (TMD) may provide information critical to the understanding of mineralization processes and bone biomechanics. High-resolution three-dimensional assessment of TMD has recently been demonstrated using synchrotron radiation microcomputed tomography (SR{mu}CT); however, this imaging modality is relatively inaccessible due to the scarcity of SR facilities. Conventional desktop {mu}CT systems are widely available and have been used extensively to assess bone microarchitecture. However, the polychromatic source and cone-shaped beam geometry complicate assessment of TMD by conventional {mu}CT. The goal of this study was to evaluate {mu}CT-based measurement of degree and distribution of tissue mineralization in a quantitative,more » spatially resolved manner. Specifically, {mu}CT measures of bone mineral content (BMC) and TMD were compared to those obtained by SR{mu}CT and gravimetric methods. Cylinders of trabecular bone were machined from human femoral heads (n=5), vertebrae (n=5), and proximal tibiae (n=4). Cylinders were imaged in saline on a polychromatic {mu}CT system at an isotropic voxel size of 8 {mu}m. Volumes were reconstructed using beam hardening correction algorithms based on hydroxyapatite (HA)-resin wedge phantoms of 200 and 1200 mgHA/cm3. SR{mu}CT imaging was performed at an isotropic voxel size of 7.50 {mu}m at the National Synchrotron Light Source. Attenuation values were converted to HA concentration using a linear regression derived by imaging a calibration phantom. Architecture and mineralization parameters were calculated from the image data. Specimens were processed using gravimetric methods to determine ash mass and density. {mu}CT-based BMC values were not affected by altering the beam hardening correction. Volume-averaged TMD values calculated by the two corrections were significantly different (p=0.008) in high volume fraction specimens only, with the 1200 mgHA/cm3 correction resulting in a 4.7% higher TMD value. {mu}CT and SR{mu}CT provided significantly different measurements of both BMC and TMD (p<0.05). In high volume fraction specimens, {mu}CT with 1200 mgHA/cm3 correction resulted in BMC and TMD values 16.7% and 15.0% lower, respectively, than SR{mu}CT values. In low volume fraction specimens, {mu}CT with 1200 mgHA/cm3 correction resulted in BMC and TMD values 12.8% and 12.9% lower, respectively, than SR{mu}CT values. {mu}CT and SR{mu}CT values were well-correlated when volume fraction groups were considered individually (BMC R2=0.97-1.00; TMD R2=0.78-0.99). Ash mass and density were higher than the SR{mu}CT equivalents by 8.6% in high volume fraction specimens and 10.9% in low volume fraction specimens (p<0.05). BMC values calculated by tomography were highly correlated with ash mass (ash versus {mu}CT R2=0.96-1.00; ash versus SR{mu}CT R2=0.99-1.00). TMD values calculated by tomography were moderately correlated with ash density (ash versus {mu}CT R2=0.64-0.72; ash versus SR{mu}CT R2=0.64). Spatially resolved comparisons highlighted substantial geometric nonuniformity in the {mu}CT data, which were reduced (but not eliminated) using the 1200 mg HA/cm3 beam hardening correction, and did not exist in the SR{mu}CT data. This study represents the first quantitative comparison of {mu}CT mineralization evaluation against SR{mu}CT and gravimetry. Our results indicate that {mu}CT mineralization measures are underestimated but well-correlated with SR{mu}CT and gravimetric data, particularly when volume fraction groups are considered individually.« less

Assessment of bone tissue mineralization by conventional x-ray microcomputed tomography: Comparison with synchrotron radiation microcomputed tomography and ash measurements

PubMed Central

Kazakia, G. J.; Burghardt, A. J.; Cheung, S.; Majumdar, S.

2008-01-01

Assessment of bone tissue mineral density (TMD) may provide information critical to the understanding of mineralization processes and bone biomechanics. High-resolution three-dimensional assessment of TMD has recently been demonstrated using synchrotron radiation microcomputed tomography (SRμCT); however, this imaging modality is relatively inaccessible due to the scarcity of SR facilities. Conventional desktop μCT systems are widely available and have been used extensively to assess bone microarchitecture. However, the polychromatic source and cone-shaped beam geometry complicate assessment of TMD by conventional μCT. The goal of this study was to evaluate μCT-based measurement of degree and distribution of tissue mineralization in a quantitative, spatially resolved manner. Specifically, μCT measures of bone mineral content (BMC) and TMD were compared to those obtained by SRμCT and gravimetric methods. Cylinders of trabecular bone were machined from human femoral heads (n=5), vertebrae (n=5), and proximal tibiae (n=4). Cylinders were imaged in saline on a polychromatic μCT system at an isotropic voxel size of 8 μm. Volumes were reconstructed using beam hardening correction algorithms based on hydroxyapatite (HA)-resin wedge phantoms of 200 and 1200 mg HA∕cm3. SRμCT imaging was performed at an isotropic voxel size of 7.50 μm at the National Synchrotron Light Source. Attenuation values were converted to HA concentration using a linear regression derived by imaging a calibration phantom. Architecture and mineralization parameters were calculated from the image data. Specimens were processed using gravimetric methods to determine ash mass and density. μCT-based BMC values were not affected by altering the beam hardening correction. Volume-averaged TMD values calculated by the two corrections were significantly different (p=0.008) in high volume fraction specimens only, with the 1200 mg HA∕cm3 correction resulting in a 4.7% higher TMD value. μCT and SRμCT provided significantly different measurements of both BMC and TMD (p<0.05). In high volume fraction specimens, μCT with 1200 mg HA∕cm3 correction resulted in BMC and TMD values 16.7% and 15.0% lower, respectively, than SRμCT values. In low volume fraction specimens, μCT with 1200 mg HA∕cm3 correction resulted in BMC and TMD values 12.8% and 12.9% lower, respectively, than SRμCT values. μCT and SRμCT values were well-correlated when volume fraction groups were considered individually (BMC R2=0.97−1.00; TMD R2=0.78−0.99). Ash mass and density were higher than the SRμCT equivalents by 8.6% in high volume fraction specimens and 10.9% in low volume fraction specimens (p<0.05). BMC values calculated by tomography were highly correlated with ash mass (ash versus μCT R2=0.96−1.00; ash versus SRμCT R2=0.99−1.00). TMD values calculated by tomography were moderately correlated with ash density (ash versus μCT R2=0.64−0.72; ash versus SRμCT R2=0.64). Spatially resolved comparisons highlighted substantial geometric nonuniformity in the μCT data, which were reduced (but not eliminated) using the 1200 mg HA∕cm3 beam hardening correction, and did not exist in the SRμCT data. This study represents the first quantitative comparison of μCT mineralization evaluation against SRμCT and gravimetry. Our results indicate that μCT mineralization measures are underestimated but well-correlated with SRμCT and gravimetric data, particularly when volume fraction groups are considered individually. PMID:18697542

Delay time correction of the gas analyzer in the calculation of anatomical dead space of the lung.

PubMed

Okubo, T; Shibata, H; Takishima, T

1983-07-01

By means of a mathematical model, we have studied a way to correct the delay time of the gas analyzer in order to calculate the anatomical dead space using Fowler's graphical method. The mathematical model was constructed of ten tubes of equal diameter but unequal length, so that the amount of dead space varied from tube to tube; the tubes were emptied sequentially. The gas analyzer responds with a time lag from the input of the gas signal to the beginning of the response, followed by an exponential response output. The single breath expired volume-concentration relationship was examined with three types of expired flow patterns of which were constant, exponential and sinusoidal. The results indicate that the time correction by the lag time plus time constant of the exponential response of the gas analyzer gives an accurate estimation of anatomical dead space. Time correction less inclusive than this, e.g. lag time only or lag time plus 50% response time, gives an overestimation, and a correction larger than this results in underestimation. The magnitude of error is dependent on the flow pattern and flow rate. The time correction in this study is only for the calculation of dead space, as the corrected volume-concentration curves does not coincide with the true curve. Such correction of the output of the gas analyzer is extremely important when one needs to compare the dead spaces of different gas species at a rather faster flow rate.

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

Zhang, JY; Hong, DL

Purpose: The purpose of this study is to investigate the patient set-up error and interfraction target coverage in cervical cancer using image-guided adaptive radiotherapy (IGART) with cone-beam computed tomography (CBCT). Methods: Twenty cervical cancer patients undergoing intensity modulated radiotherapy (IMRT) were randomly selected. All patients were matched to the isocenter using laser with the skin markers. Three dimensional CBCT projections were acquired by the Varian Truebeam treatment system. Set-up errors were evaluated by radiation oncologists, after CBCT correction. The clinical target volume (CTV) was delineated on each CBCT, and the planning target volume (PTV) coverage of each CBCT-CTVs was analyzed.more » Results: A total of 152 CBCT scans were acquired from twenty cervical cancer patients, the mean set-up errors in the longitudinal, vertical, and lateral direction were 3.57, 2.74 and 2.5mm respectively, without CBCT corrections. After corrections, these were decreased to 1.83, 1.44 and 0.97mm. For the target coverage, CBCT-CTV coverage without CBCT correction was 94% (143/152), and 98% (149/152) with correction. Conclusion: Use of CBCT verfication to measure patient setup errors could be applied to improve the treatment accuracy. In addition, the set-up error corrections significantly improve the CTV coverage for cervical cancer patients.« less

A Computational Framework for High-Throughput Isotopic Natural Abundance Correction of Omics-Level Ultra-High Resolution FT-MS Datasets

PubMed Central

Carreer, William J.; Flight, Robert M.; Moseley, Hunter N. B.

2013-01-01

New metabolomics applications of ultra-high resolution and accuracy mass spectrometry can provide thousands of detectable isotopologues, with the number of potentially detectable isotopologues increasing exponentially with the number of stable isotopes used in newer isotope tracing methods like stable isotope-resolved metabolomics (SIRM) experiments. This huge increase in usable data requires software capable of correcting the large number of isotopologue peaks resulting from SIRM experiments in a timely manner. We describe the design of a new algorithm and software system capable of handling these high volumes of data, while including quality control methods for maintaining data quality. We validate this new algorithm against a previous single isotope correction algorithm in a two-step cross-validation. Next, we demonstrate the algorithm and correct for the effects of natural abundance for both 13C and 15N isotopes on a set of raw isotopologue intensities of UDP-N-acetyl-D-glucosamine derived from a 13C/15N-tracing experiment. Finally, we demonstrate the algorithm on a full omics-level dataset. PMID:24404440

Grey matter volume loss is associated with specific clinical motor signs in Huntington's disease.

PubMed

Coppen, Emma M; Jacobs, Milou; van den Berg-Huysmans, Annette A; van der Grond, Jeroen; Roos, Raymund A C

2018-01-01

Motor disturbances are clinical hallmarks of Huntington's disease (HD) and involve chorea, dystonia, hypokinesia and visuomotor dysfunction. Investigating the association between specific motor signs and different regional volumes is important to understand the heterogeneity of HD. To investigate the motor phenotype of HD and associations with subcortical and cortical grey matter volume loss. Structural T1-weighted MRI scans of 79 HD patients and 30 healthy controls were used to calculate volumes of seven subcortical structures including the nucleus accumbens, hippocampus, thalamus, caudate nucleus, putamen, pallidum and amygdala. Multiple linear regression analyses, corrected for age, gender, CAG, MRI scan protocol and normalized brain volume, were performed to assess the relationship between subcortical volumes and different motor subdomains (i.e. eye movements, chorea, dystonia, hypokinesia/rigidity and gait/balance). Voxel-based morphometry analysis was used to investigate the relationship between cortical volume changes and motor signs. Subcortical volume loss of the accumbens nucleus, caudate nucleus, putamen, and pallidum were associated with higher chorea scores. No other subcortical region was significantly associated with motor symptoms after correction for multiple comparisons. Voxel-based cortical grey matter volume reductions in occipital regions were related with an increase in eye movement scores. In HD, chorea is mainly associated with subcortical volume loss, while eye movements are more related to cortical volume loss. Both subcortical and cortical degeneration has an impact on motor impairment in HD. This implies that there is a widespread contribution of different brain regions resulting in the clinical motor presentation seen in HD patients. Copyright © 2017 Elsevier Ltd. All rights reserved.

Naval War College Review. Volume 62, Number, 3, Summer 2009

DTIC Science & Technology

2009-06-01

assert their sovereign rights to protect tourism , fisheries, and other environmental resources in their territorial waters and EEZs. However, many...As a result, there is still no effective gover - nance, or burden sharing in the provision of security, of the sea-lanes transiting the South China...regional frameworks for improving maritime gover - nance, and cooperation in enforcing the rule of law,” at sea.18 Although the strategy correctly suggests

RF Sytems in Space. Volume II. Space-Based Radar Analyses.

DTIC Science & Technology

1983-04-01

Electron Environment 124 5.2 Trapped Proton Environment 125 5.3 Average Expected Exposure to Solar Protons 126 5.4 Total Dose Versus Shielding Thickness...degradation will be unacceptable. Unless some form of compensation is employed, the antenna will not meet its design specification over the required...field-of-view. Section 3.2 also evaluates the effectiveness of phase compensation to correct for the aperture distortions. Two forms of phase compensa

Allometric Analysis Detects Brain Size-Independent Effects of Sex and Sex Chromosome Complement on Human Cerebellar Organization

PubMed Central

Mankiw, Catherine; Park, Min Tae M.; Reardon, P.K.; Fish, Ari M.; Clasen, Liv S.; Greenstein, Deanna; Blumenthal, Jonathan D.; Lerch, Jason P.; Chakravarty, M. Mallar

2017-01-01

The cerebellum is a large hindbrain structure that is increasingly recognized for its contribution to diverse domains of cognitive and affective processing in human health and disease. Although several of these domains are sex biased, our fundamental understanding of cerebellar sex differences—including their spatial distribution, potential biological determinants, and independence from brain volume variation—lags far behind that for the cerebrum. Here, we harness automated neuroimaging methods for cerebellar morphometrics in 417 individuals to (1) localize normative male–female differences in raw cerebellar volume, (2) compare these to sex chromosome effects estimated across five rare sex (X/Y) chromosome aneuploidy (SCA) syndromes, and (3) clarify brain size-independent effects of sex and SCA on cerebellar anatomy using a generalizable allometric approach that considers scaling relationships between regional cerebellar volume and brain volume in health. The integration of these approaches shows that (1) sex and SCA effects on raw cerebellar volume are large and distributed, but regionally heterogeneous, (2) human cerebellar volume scales with brain volume in a highly nonlinear and regionally heterogeneous fashion that departs from documented patterns of cerebellar scaling in phylogeny, and (3) cerebellar organization is modified in a brain size-independent manner by sex (relative expansion of total cerebellum, flocculus, and Crus II-lobule VIIIB volumes in males) and SCA (contraction of total cerebellar, lobule IV, and Crus I volumes with additional X- or Y-chromosomes; X-specific contraction of Crus II-lobule VIIIB). Our methods and results clarify the shifts in human cerebellar organization that accompany interwoven variations in sex, sex chromosome complement, and brain size. SIGNIFICANCE STATEMENT Cerebellar systems are implicated in diverse domains of sex-biased behavior and pathology, but we lack a basic understanding of how sex differences in the human cerebellum are distributed and determined. We leverage a rare neuroimaging dataset to deconvolve the interwoven effects of sex, sex chromosome complement, and brain size on human cerebellar organization. We reveal topographically variegated scaling relationships between regional cerebellar volume and brain size in humans, which (1) are distinct from those observed in phylogeny, (2) invalidate a traditional neuroimaging method for brain volume correction, and (3) allow more valid and accurate resolution of which cerebellar subcomponents are sensitive to sex and sex chromosome complement. These findings advance understanding of cerebellar organization in health and sex chromosome aneuploidy. PMID:28314818

Motion Artifact Reduction in Pediatric Diffusion Tensor Imaging Using Fast Prospective Correction

PubMed Central

Alhamud, A.; Taylor, Paul A.; Laughton, Barbara; van der Kouwe, André J.W.; Meintjes, Ernesta M.

2014-01-01

Purpose To evaluate the patterns of head motion in scans of young children and to examine the influence of corrective techniques, both qualitatively and quantitatively. We investigate changes that both retrospective (with and without diffusion table reorientation) and prospective (implemented with a short navigator sequence) motion correction induce in the resulting diffusion tensor measures. Materials and Methods Eighteen pediatric subjects (aged 5–6 years) were scanned using 1) a twice-refocused, 2D diffusion pulse sequence, 2) a prospectively motion-corrected, navigated diffusion sequence with reacquisition of a maximum of five corrupted diffusion volumes, and 3) a T1-weighted structural image. Mean fractional anisotropy (FA) values in white and gray matter regions, as well as tractography in the brainstem and projection fibers, were evaluated to assess differences arising from retrospective (via FLIRT in FSL) and prospective motion correction. In addition to human scans, a stationary phantom was also used for further evaluation. Results In several white and gray matter regions retrospective correction led to significantly (P < 0.05) reduced FA means and altered distributions compared to the navigated sequence. Spurious tractographic changes in the retrospectively corrected data were also observed in subject data, as well as in phantom and simulated data. Conclusion Due to the heterogeneity of brain structures and the comparatively low resolution (~2 mm) of diffusion data using 2D single shot sequencing, retrospective motion correction is susceptible to distortion from partial voluming. These changes often negatively bias diffusion tensor imaging parameters. Prospective motion correction was shown to produce smaller changes. PMID:24935904

Motion artifact reduction in pediatric diffusion tensor imaging using fast prospective correction.

PubMed

Alhamud, A; Taylor, Paul A; Laughton, Barbara; van der Kouwe, André J W; Meintjes, Ernesta M

2015-05-01

To evaluate the patterns of head motion in scans of young children and to examine the influence of corrective techniques, both qualitatively and quantitatively. We investigate changes that both retrospective (with and without diffusion table reorientation) and prospective (implemented with a short navigator sequence) motion correction induce in the resulting diffusion tensor measures. Eighteen pediatric subjects (aged 5-6 years) were scanned using 1) a twice-refocused, 2D diffusion pulse sequence, 2) a prospectively motion-corrected, navigated diffusion sequence with reacquisition of a maximum of five corrupted diffusion volumes, and 3) a T1 -weighted structural image. Mean fractional anisotropy (FA) values in white and gray matter regions, as well as tractography in the brainstem and projection fibers, were evaluated to assess differences arising from retrospective (via FLIRT in FSL) and prospective motion correction. In addition to human scans, a stationary phantom was also used for further evaluation. In several white and gray matter regions retrospective correction led to significantly (P < 0.05) reduced FA means and altered distributions compared to the navigated sequence. Spurious tractographic changes in the retrospectively corrected data were also observed in subject data, as well as in phantom and simulated data. Due to the heterogeneity of brain structures and the comparatively low resolution (∼2 mm) of diffusion data using 2D single shot sequencing, retrospective motion correction is susceptible to distortion from partial voluming. These changes often negatively bias diffusion tensor imaging parameters. Prospective motion correction was shown to produce smaller changes. © 2014 Wiley Periodicals, Inc.

Simplified correction of B1 inhomogeneity for chemical exchange saturation transfer (CEST) MRI measurement with surface transceiver coil

NASA Astrophysics Data System (ADS)

Sun, Phillip Z.; Zhou, Iris Y.; Igarashi, Takahiro; Guo, Yingkun; Xiao, Gang; Wu, Renhua

2015-03-01

Chemical exchange saturation transfer (CEST) MRI is sensitive to dilute exchangeable protons and local properties such as pH and temperate, yet its susceptibility to field inhomogeneity limits its in vivo applications. Particularly, CEST measurement varies with RF irradiation power, the dependence of which is complex due to concomitant direct RF saturation (RF spillover) effect. Because the volume transmitters provide relatively homogeneous RF field, they have been conventionally used for CEST imaging despite of their elevated specific absorption rate (SAR) and relatively low sensitivity than surface coils. To address this limitation, we developed an efficient B1 inhomogeneity correction algorithm that enables CEST MRI using surface transceiver coils. This is built on recent work that showed the inverse CEST asymmetry analysis (CESTRind) is not susceptible to confounding RF spillover effect. We here postulated that the linear relationship between RF power level and CESTRind can be extended for correcting B1 inhomogeneity induced CEST MRI artifacts. Briefly, we prepared a tissue-like Creatine gel pH phantom and collected multiparametric MRI including relaxation, field map and CEST MRI under multiple RF power levels, using a conventional surface transceiver coil. The raw CEST images showed substantial heterogeneity due to B1 inhomogeneity, with pH contrast to noise ratio (CNR) being 8.8. In comparison, pH MRI CNR of the fieldinhomogeneity corrected CEST MRI was found to be 17.2, substantially higher than that without correction. To summarize, our study validated an efficient field inhomogeneity correction that enables sensitive CEST MRI with surface transceiver, promising for in vivo translation.

40 CFR 63.6620 - What performance tests and other procedures must I use?

Code of Federal Regulations, 2011 CFR

2011-07-01

... based on the ratio of oxygen volume to the ultimate CO2 volume produced by the fuel at zero percent... volume of CO2 produced to the gross calorific value of the fuel from Method 19, dsm3/J (dscf/106 Btu... equivalent percent carbon dioxide (CO2). If pollutant concentrations are to be corrected to 15 percent oxygen...

40 CFR 63.6620 - What performance tests and other procedures must I use?

Code of Federal Regulations, 2012 CFR

2012-07-01

... based on the ratio of oxygen volume to the ultimate CO2 volume produced by the fuel at zero percent... volume of CO2 produced to the gross calorific value of the fuel from Method 19, dsm3/J (dscf/106 Btu... equivalent percent carbon dioxide (CO2). If pollutant concentrations are to be corrected to 15 percent oxygen...

White Matter Volume Predicts Language Development in Congenital Heart Disease

PubMed Central

Rollins, Caitlin K.; Asaro, Lisa A.; Akhondi-Asl, Alireza; Kussman, Barry D.; Rivkin, Michael J.; Bellinger, David C.; Warfield, Simon K.; Wypij, David; Newburger, Jane W.; Soul, Janet S.

2016-01-01

Objective To determine whether brain volume is reduced at one year and whether these volumes are associated with neurodevelopment in biventricular congenital heart disease (CHD) repaired in infancy. Study design Infants with biventricular CHD (n = 48) underwent brain magnetic resonance imaging (MRI) and neurodevelopmental testing with the Bayley Scales of Infant Development-II (BSID-II) and the MacArthur-Bates Communicative Development Inventories (CDI) at one year. A multi-template based probabilistic segmentation algorithm was applied to volumetric MRI data. We compared volumes with those of 13 healthy control infants of comparable ages. In the CHD group, we measured Spearman correlations between neurodevelopmental outcomes and the residuals from linear regression of the volumes on corrected chronological age at MRI and sex. Results Compared with controls, CHD infant had reductions of 54 mL in total brain (P = 0.009), 40 mL in cerebral white matter (P < 0.001), and 1.2 mL in brainstem (P = 0.003) volumes. Within the CHD group, brain volumes were not correlated with BSID-II scores but did correlate positively with CDI language development. Conclusion Infants with biventricular CHD show total brain volume reductions at one year of age, driven by differences in cerebral white matter. White matter volume correlates with language development, but not broader developmental indices. These findings suggest that abnormalities in white matter development detected months after corrective heart surgery may contribute to language impairment. Trial registration ClinicalTrials.gov: NCT00006183 PMID:27837950

Arm Volumetry Versus Upper Extremity Lymphedema Index: Validity of Upper Extremity Lymphedema Index for Body-Type Corrected Arm Volume Evaluation.

PubMed

Yamamoto, Nana; Yamamoto, Takumi; Hayashi, Nobuko; Hayashi, Akitatsu; Iida, Takuya; Koshima, Isao

2016-06-01

Volumetry, measurement of extremity volume, is a commonly used method for upper extremity lymphedema (UEL) evaluation. However, comparison between different patients with different physiques is difficult with volumetry, because body-type difference greatly affects arm volume. Seventy arms of 35 participants who had no history of arm edema or breast cancer were evaluated. Arm volume was calculated using a summed truncated cone model, and UEL index was calculated using circumferences and body mass index (BMI). Examinees' BMI was classified into 3 groups, namely, low BMI (BMI, <20 kg/m), middle BMI (BMI, 20-25 kg/m), and high BMI (BMI, >25 kg/m). Arm volume and UEL index were compared with corresponding BMI groups. Mean (SD) arm volume was 1090.9 (205.5) mL, and UEL index 96.9 (5.6). There were significant differences in arm volume between BMI groups [low BMI vs middle BMI vs high BMI, 945.2 (107.4) vs 1045.2 (87.5) vs 1443.1 (244.4) mL, P < 0.001]. There was no significant difference in UEL index between BMI groups [low BMI vs middle BMI vs high BMI, 97.2 (4.2) vs 96.6 (4.6) vs 96.7 (9.9), P > 0.5]. Arm volume significantly increased with increase of BMI, whereas UEL index stayed constant regardless of BMI. Upper extremity lymphedema index would allow better body-type corrected arm volume evaluation compared with arm volumetry.

Methods for the correction of vascular artifacts in PET O-15 water brain-mapping studies

NASA Astrophysics Data System (ADS)

Chen, Kewei; Reiman, E. M.; Lawson, M.; Yun, Lang-sheng; Bandy, D.; Palant, A.

1996-12-01

While positron emission tomographic (PET) measurements of regional cerebral blood flow (rCBF) can be used to map brain regions that are involved in normal and pathological human behaviors, measurements in the anteromedial temporal lobe can be confounded by the combined effects of radiotracer activity in neighboring arteries and partial-volume averaging. The authors now describe two simple methods to address this vascular artifact. One method utilizes the early frames of a dynamic PET study, while the other method utilizes a coregistered magnetic resonance image (MRI) to characterize the vascular region of interest (VROI). Both methods subsequently assign a common value to each pixel in the VROI for the control (baseline) scan and the activation scan. To study the vascular artifact and to demonstrate the ability of the proposed methods correcting the vascular artifact, four dynamic PET scans were performed in a single subject during the same behavioral state. For each of the four scans, a vascular scan containing vascular activity was computed as the summation of the images acquired 0-60 s after radiotracer administration, and a control scan containing minimal vascular activity was computed as the summation of the images acquired 20-80 s after radiotracer administration. t-score maps calculated from the four pairs of vascular and control scans were used to characterize regional blood flow differences related to vascular activity before and after the application of each vascular artifact correction method. Both methods eliminated the observed differences in vascular activity, as well as the vascular artifact observed in the anteromedial temporal lobes. Using PET data from a study of normal human emotion, these methods permitted the authors to identify rCBF increases in the anteromedial temporal lobe free from the potentially confounding, combined effects of vascular activity and partial-volume averaging.

TU-H-206-04: An Effective Homomorphic Unsharp Mask Filtering Method to Correct Intensity Inhomogeneity in Daily Treatment MR Images

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

Yang, D; Gach, H; Li, H

Purpose: The daily treatment MRIs acquired on MR-IGRT systems, like diagnostic MRIs, suffer from intensity inhomogeneity issue, associated with B1 and B0 inhomogeneities. An improved homomorphic unsharp mask (HUM) filtering method, automatic and robust body segmentation, and imaging field-of-view (FOV) detection methods were developed to compute the multiplicative slow-varying correction field and correct the intensity inhomogeneity. The goal is to improve and normalize the voxel intensity so that the images could be processed more accurately by quantitative methods (e.g., segmentation and registration) that require consistent image voxel intensity values. Methods: HUM methods have been widely used for years. A bodymore » mask is required, otherwise the body surface in the corrected image would be incorrectly bright due to the sudden intensity transition at the body surface. In this study, we developed an improved HUM-based correction method that includes three main components: 1) Robust body segmentation on the normalized image gradient map, 2) Robust FOV detection (needed for body segmentation) using region growing and morphologic filters, and 3) An effective implementation of HUM using repeated Gaussian convolution. Results: The proposed method was successfully tested on patient images of common anatomical sites (H/N, lung, abdomen and pelvis). Initial qualitative comparisons showed that this improved HUM method outperformed three recently published algorithms (FCM, LEMS, MICO) in both computation speed (by 50+ times) and robustness (in intermediate to severe inhomogeneity situations). Currently implemented in MATLAB, it takes 20 to 25 seconds to process a 3D MRI volume. Conclusion: Compared to more sophisticated MRI inhomogeneity correction algorithms, the improved HUM method is simple and effective. The inhomogeneity correction, body mask, and FOV detection methods developed in this study would be useful as preprocessing tools for many MRI-related research and clinical applications in radiotherapy. Authors have received research grants from ViewRay and Varian.« less

The effect of on-line position correction on the dose distribution in focal radiotherapy for bladder cancer

PubMed Central

van Rooijen, Dominique C; van de Kamer, Jeroen B; Pool, René; Hulshof, Maarten CCM; Koning, Caro CE; Bel, Arjan

2009-01-01

Background The purpose of this study was to determine the dosimetric effect of on-line position correction for bladder tumor irradiation and to find methods to predict and handle this effect. Methods For 25 patients with unifocal bladder cancer intensity modulated radiotherapy (IMRT) with 5 beams was planned. The requirement for each plan was that 99% of the target volume received 95% of the prescribed dose. Tumor displacements from -2.0 cm to 2.0 cm in each dimension were simulated, using 0.5 cm increments, resulting in 729 simulations per patient. We assumed that on-line correction for the tumor was applied perfectly. We determined the correlation between the change in D99% and the change in path length, which is defined here as the distance from the skin to the isocenter for each beam. In addition the margin needed to avoid underdosage was determined and the probability that an underdosage occurs in a real treatment was calculated. Results Adjustments for tumor displacement with perfect on-line position correction resulted in an altered dose distribution. The altered fraction dose to the target varied from 91.9% to 100.4% of the prescribed dose. The mean D99% (± SD) was 95.8% ± 1.0%. There was a modest linear correlation between the difference in D99% and the change in path length of the beams after correction (R2 = 0.590). The median probability that a systematic underdosage occurs in a real treatment was 0.23% (range: 0 - 24.5%). A margin of 2 mm reduced that probability to < 0.001% in all patients. Conclusion On-line position correction does result in an altered target coverage, due to changes in average path length after position correction. An extra margin can be added to prevent underdosage. PMID:19775479

Diaphragm correction factors for the FAC-IR-300 free-air ionization chamber.

PubMed

Mohammadi, Seyed Mostafa; Tavakoli-Anbaran, Hossein

2018-02-01

A free-air ionization chamber FAC-IR-300, designed by the Atomic Energy Organization of Iran, is used as the primary Iranian national standard for the photon air kerma. For accurate air kerma measurements, the contribution from the scattered photons to the total energy released in the collecting volume must be eliminated. One of the sources of scattered photons is the chamber's diaphragm. In this paper, the diaphragm scattering correction factor, k dia , and the diaphragm transmission correction factor, k tr , were introduced. These factors represent corrections to the measured charge (or current) for the photons scattered from the diaphragm surface and the photons penetrated through the diaphragm volume, respectively. The k dia and k tr values were estimated by Monte Carlo simulations. The simulations were performed for the mono-energetic photons in the energy range of 20 - 300keV. According to the simulation results, in this energy range, the k dia values vary between 0.9997 and 0.9948, and k tr values decrease from 1.0000 to 0.9965. The corrections grow in significance with increasing energy of the primary photons. Copyright © 2017 Elsevier Ltd. All rights reserved.

Spatiotemporal alignment of in utero BOLD-MRI series.

PubMed

Turk, Esra Abaci; Luo, Jie; Gagoski, Borjan; Pascau, Javier; Bibbo, Carolina; Robinson, Julian N; Grant, P Ellen; Adalsteinsson, Elfar; Golland, Polina; Malpica, Norberto

2017-08-01

To present a method for spatiotemporal alignment of in-utero magnetic resonance imaging (MRI) time series acquired during maternal hyperoxia for enabling improved quantitative tracking of blood oxygen level-dependent (BOLD) signal changes that characterize oxygen transport through the placenta to fetal organs. The proposed pipeline for spatiotemporal alignment of images acquired with a single-shot gradient echo echo-planar imaging includes 1) signal nonuniformity correction, 2) intravolume motion correction based on nonrigid registration, 3) correction of motion and nonrigid deformations across volumes, and 4) detection of the outlier volumes to be discarded from subsequent analysis. BOLD MRI time series collected from 10 pregnant women during 3T scans were analyzed using this pipeline. To assess pipeline performance, signal fluctuations between consecutive timepoints were examined. In addition, volume overlap and distance between manual region of interest (ROI) delineations in a subset of frames and the delineations obtained through propagation of the ROIs from the reference frame were used to quantify alignment accuracy. A previously demonstrated rigid registration approach was used for comparison. The proposed pipeline improved anatomical alignment of placenta and fetal organs over the state-of-the-art rigid motion correction methods. In particular, unexpected temporal signal fluctuations during the first normoxia period were significantly decreased (P < 0.01) and volume overlap and distance between region boundaries measures were significantly improved (P < 0.01). The proposed approach to align MRI time series enables more accurate quantitative studies of placental function by improving spatiotemporal alignment across placenta and fetal organs. 1 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:403-412. © 2017 International Society for Magnetic Resonance in Medicine.

SU-E-T-513: Investigating Dose of Internal Target Volume After Correcting for Tissue Heterogeneity in SBRT Lung Plans with Homogeneity Calculation

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

Qi, P; Zhuang, T; Magnelli, A

2015-06-15

Purpose It was recommended to use the prescription of 54 Gy/3 with heterogeneity corrections for previously established dose scheme of 60 Gy/3 with homogeneity calculation. This study is to investigate dose coverage for the internal target volume (ITV) with and without heterogeneity correction. Methods Thirty patients who received stereotactic body radiotherapy (SBRT) to a dose of 60 Gy in 3 fractions with homogeneous planning for early stage non-small-cell lung cancer (NSCLC) were selected. ITV was created either from 4DCT scans or a fusion of multi-phase respiratory scans. Planning target volume (PTV) was a 5 mm expansion of the ITV. Formore » this study, we recalculated homogeneous clinical plans using heterogeneity corrections with monitor units set as clinically delivered. All plans were calculated with 3 mm dose grids and collapsed cone convolution algorithm. To account for uncertainties from tumor delineation and image-guided radiotherapy, a structure ITV2mm was created by expanding ITV with 2 mm margins. Dose coverage to the PTV, ITV and ITV2mm were compared with a student paired t-test. Results With heterogeneity corrections, the PTV V60Gy decreased by 10.1% ± 18.4% (p<0.01) while the maximum dose to the PTV increased by 3.7 ± 4.3% (p<0.01). With and without corrections, D99% was 65.8 ± 4.0 Gy and 66.7 ± 4.8 Gy (p=0.15) for the ITV, and 63.9 ± 3.4 Gy and 62.9 ± 4.6 Gy for the ITV2mm (p=0.22), respectively. The mean dose to the ITV and ITV2mm increased 3.6% ± 4.7% (p<0.01) and 2.3% ± 5.2% (p=0.01) with heterogeneity corrections. Conclusion After heterogeneity correction, the peripheral coverage of the PTV decreased to approximately 54 Gy, but D99% of the ITV and ITV2mm was unchanged and the mean dose to the ITV and ITV2mm was increased. Clinical implication of these results requires more investigation.« less

Correction to: The effect of cationically-modified phosphorylcholine polymers on human osteoblasts in vitro and their effect on bone formation in vivo.

PubMed

Lawton, Jonathan M; Habib, Mariam; Ma, Bingkui; Brooks, Roger A; Best, Serena M; Lewis, Andrew L; Rushton, Neil; Bonfield, William

2018-02-22

The article "The effect of cationically modified phosphorylcholine polymers on human osteoblasts in vitro and their effect on bone formation in vivo", written by Jonathan M. Lawton, Mariam Habib, Bingkui Ma, Roger A. Brooks, Serena M. Best, Andrew L. Lewis, Neil Rushton and William Bonfield, was originally published Online First without open access. After publication in volume 28, issue 9, page 144 it was noticed that the copyright was wrong in the PDF version of the article. The copyright of the article should read as " © The Author(s) 2017".

The Schwarzschild effect of the dosimetry film Kodak EDR 2.

PubMed

Djouguela, A; Kollhoff, R; Rubach, A; Harder, D; Poppe, B

2005-11-07

The magnitude of the Schwarzschild effect or failure of the reciprocity law has been experimentally investigated for the dosimetry film EDR 2 from Kodak. When the dose rate applied to achieve a given dose was reduced by a factor of 12, the net optical density was reduced by up to 5%. The clinical importance of this effect is negligible as long as the films are calibrated at a value of the dose rate approximately representative of the dose rates occurring in the target volume, but in target regions of strongly reduced dose rate the Schwarzschild effect should be allowed for by a correction of the net optical density.

The effects of a physician slowdown on emergency department volume and treatment.

PubMed

Walsh, Brian; Eskin, Barnet; Allegra, John; Rothman, Jonathan; Junker, Elizabeth

2006-11-01

In February 2003, many physicians in New Jersey participated in a work slowdown to publicize large increases in malpractice premiums and generate support for legislative reform. It was anticipated that the community physician slowdown (hereafter referred to as "slowdown") would increase emergency department (ED) visits. The authors' goal was to help others prepare for anticipated increases in ED volumes by describing the preparatory staffing changes made and quantifying increases in ED volume. This was a retrospective cohort study performed at a New Jersey suburban teaching hospital with 70,000 annual visits. Consecutive patients seen by emergency physicians were enrolled. The authors extracted patient visit data from the computerized tracking system and analyzed hours worked by personnel, patient volumes, admission rates, and patient throughput times. Variables from each day of the slowdown with baseline values for the same day of the week for the four weeks before and after the slowdown were compared. A Bonferroni correction was used, with p < 0.01 considered statistically significant. Total patient volume increased 79% from baseline (95% confidence interval [CI] = 20% to 137%). Pediatric volume increased 223% (95% CI = 171% to 274%). Overall admission rate decreased 29% compared with baseline (95% CI = 8% to 51%). Patient throughput times did not change significantly. Similar results for these variables were found for the second through fourth days of the slowdown. Emergency department visits, especially pediatric visits, increased markedly during the community physician slowdown. Anticipatory increases in staffing effectively prevented increased throughput times.

User's manual for the one-dimensional hypersonic experimental aero-thermodynamic (1DHEAT) data reduction code

NASA Technical Reports Server (NTRS)

Hollis, Brian R.

1995-01-01

A FORTRAN computer code for the reduction and analysis of experimental heat transfer data has been developed. This code can be utilized to determine heat transfer rates from surface temperature measurements made using either thin-film resistance gages or coaxial surface thermocouples. Both an analytical and a numerical finite-volume heat transfer model are implemented in this code. The analytical solution is based on a one-dimensional, semi-infinite wall thickness model with the approximation of constant substrate thermal properties, which is empirically corrected for the effects of variable thermal properties. The finite-volume solution is based on a one-dimensional, implicit discretization. The finite-volume model directly incorporates the effects of variable substrate thermal properties and does not require the semi-finite wall thickness approximation used in the analytical model. This model also includes the option of a multiple-layer substrate. Fast, accurate results can be obtained using either method. This code has been used to reduce several sets of aerodynamic heating data, of which samples are included in this report.

Single Transducer Ultrasonic Imaging Method that Eliminates the Effect of Plate Thickness Variation in the Image

NASA Technical Reports Server (NTRS)

Roth, Don J.

1996-01-01

This article describes a single transducer ultrasonic imaging method that eliminates the effect of plate thickness variation in the image. The method thus isolates ultrasonic variations due to material microstructure. The use of this method can result in significant cost savings because the ultrasonic image can be interpreted correctly without the need for machining to achieve precise thickness uniformity during nondestructive evaluations of material development. The method is based on measurement of ultrasonic velocity. Images obtained using the thickness-independent methodology are compared with conventional velocity and c-scan echo peak amplitude images for monolithic ceramic (silicon nitride), metal matrix composite and polymer matrix composite materials. It was found that the thickness-independent ultrasonic images reveal and quantify correctly areas of global microstructural (pore and fiber volume fraction) variation due to the elimination of thickness effects. The thickness-independent ultrasonic imaging method described in this article is currently being commercialized under a cooperative agreement between NASA Lewis Research Center and Sonix, Inc.

Patterns of age related changes for phosphodiesterase type-10A in comparison with dopamine D2/3 receptors and sub-cortical volumes in the human basal ganglia: A PET study with 18F-MNI-659 and 11C-raclopride with correction for partial volume effect.

PubMed

Fazio, Patrik; Schain, Martin; Mrzljak, Ladislav; Amini, Nahid; Nag, Sangram; Al-Tawil, Nabil; Fitzer-Attas, Cheryl J; Bronzova, Juliana; Landwehrmeyer, Bernhard; Sampaio, Cristina; Halldin, Christer; Varrone, Andrea

2017-05-15

Phosphodiesterase 10A enzyme (PDE10A) is an important striatal target that has been shown to be affected in patients with neurodegenerative disorders, particularly Huntington´s disease (HD). PDE10A is expressed on striatal neurones in basal ganglia where other known molecular targets are enriched such as dopamine D 2/3 receptors (D 2/3 R). The aim of this study was to examine the availability of PDE10A enzyme in relation with age and gender and to compare those changes with those related to D 2/3 R and volumes in different regions of the basal ganglia. As a secondary objective we examined the relative distribution of D 2/3 R and PDE10A enzyme in the striatum and globus pallidus. Forty control subjects (20F/20M; age: 44±11y, age range 27-69) from an ongoing positron emission tomography (PET) study in HD gene expansion carriers were included. Subjects were examined with PET using the high-resolution research tomograph (HRRT) and with 3T magnetic resonance imaging (MRI). The PDE10A radioligand 18 F-MNI-659 and D 2/3 R radioligand 11 C-raclopride were used. The outcome measure was the binding potential (BP ND ) estimated with the two-tissue compartment model ( 18 F-MNI-659) and the simplified reference tissue model ( 11 C-raclopride) using the cerebellum as reference region. The PET data were corrected for partial volume effects. In the striatum, PDE10A availability showed a significant age-related decline that was larger compared to the age-related decline of D 2/3 R availability and to the age-related decline of volumes measured with MRI. In the globus pallidus, a less pronounced decline of PDE10A availability was observed, whereas D 2/3 R availability and volumes seemed to be rather stable with aging. The distribution of the PDE10A enzyme was different from the distribution of D 2/3 R, with higher availability in the globus pallidus. These results indicate that aging is associated with a considerable physiological reduction of the availability of PDE10A enzyme in the striatum. Moreover as result of the analysis, in the striatum for both the molecular targets, we observed a gender effect with higher BP ND the female group. Copyright © 2017 Elsevier Inc. All rights reserved.

Small Volume Isotopic Analysis of Zircon Using LA-MC-ICP-MS U-Pb and Lu-Hf and Sub-ng Amounts of Hf in Solution

NASA Astrophysics Data System (ADS)

Bauer, A.; Horstwood, M. S.

2016-12-01

Crust-mantle evolution studies are greatly informed by zircon U-Pb and Lu-Hf isotopic datasets and the ease with which these data can now be acquired has seen their application become commonplace. In order to deconvolute geochemical change and interpret geologic variation in complexly zoned zircons, this information is most ideally obtained on the smallest volume of zircon by successive SIMS U-Pb and LA-MC-ICP-MS Lu-Hf isotopic analyses. However, due to variations in zircon growth zone geometry at depth, the Lu-Hf analysis may not relate to the lower volume U-Pb analysis, potentially causing inaccuracy of the resultant age-corrected Hf isotope signature. Laser ablation split-stream methods are applied to be certain that U-Pb and Lu-Hf data represent the same volume of zircon, however, the sampling volume remains relatively large at 40x30µm1. Coupled ID-TIMS U-Pb and solution MC-ICP-MS Lu-Hf work traditionally utilize whole-zircon dissolution ( 10-50ng Hf), which has the potential to homogenize different zones of geologic significance within an analysis. Conversely, modern ID-TIMS U-Pb methods utilize microsampling of zircon grains, often providing < 5ng Hf, thereby challenging conventional Lu-Hf acquisition protocols to achieve the required precision. In order to obtain usable precision on minimal zircon volumes, we developed laser ablation methods using successive 25um spot U-Pb and Lu-Hf ablation pits with a combined depth of 18um, and low-volume solution introduction methods without Hf-REE separation utilizing Hf amounts as low as 0.4ng, while retaining an uncertainty level of ca. 1 ɛHf for both methods. We investigated methods of Yb interference correction and the potential for matrix effects, with a particular focus on the accurate quantification of 176Lu/177Hf. These improvements reduce the minimum amount of material required for U-Pb and Hf isotopic analysis of zircon by about an order of magnitude. 1Ibanez-Mejia et al (2015). PreRes, 267, 285-310.

Reproducibility and day time bias correction of optoelectronic leg volumetry: a prospective cohort study.

PubMed

Engelberger, Rolf P; Blazek, Claudia; Amsler, Felix; Keo, Hong H; Baumann, Frédéric; Blättler, Werner; Baumgartner, Iris; Willenberg, Torsten

2011-10-05

Leg edema is a common manifestation of various underlying pathologies. Reliable measurement tools are required to quantify edema and monitor therapeutic interventions. Aim of the present work was to investigate the reproducibility of optoelectronic leg volumetry over 3 weeks' time period and to eliminate daytime related within-individual variability. Optoelectronic leg volumetry was performed in 63 hairdressers (mean age 45 ± 16 years, 85.7% female) in standing position twice within a minute for each leg and repeated after 3 weeks. Both lower leg (legBD) and whole limb (limbBF) volumetry were analysed. Reproducibility was expressed as analytical and within-individual coefficients of variance (CVA, CVW), and as intra-class correlation coefficients (ICC). A total of 492 leg volume measurements were analysed. Both legBD and limbBF volumetry were highly reproducible with CVA of 0.5% and 0.7%, respectively. Within-individual reproducibility of legBD and limbBF volumetry over a three weeks' period was high (CVW 1.3% for both; ICC 0.99 for both). At both visits, the second measurement revealed a significantly higher volume compared to the first measurement with a mean increase of 7.3 ml ± 14.1 (0.33% ± 0.58%) for legBD and 30.1 ml ± 48.5 ml (0.52% ± 0.79%) for limbBF volume. A significant linear correlation between absolute and relative leg volume differences and the difference of exact day time of measurement between the two study visits was found (P < .001). A therefore determined time-correction formula permitted further improvement of CVW. Leg volume changes can be reliably assessed by optoelectronic leg volumetry at a single time point and over a 3 weeks' time period. However, volumetry results are biased by orthostatic and daytime-related volume changes. The bias for day-time related volume changes can be minimized by a time-correction formula.

Greater intake of vitamins B6 and B12 spares gray matter in healthy elderly: a voxel-based morphometry study

PubMed Central

Erickson, Kirk I.; Suever, Barbara L.; Shaurya Prakash, Ruchika; Colcombe, Stanley J.; McAuley, Edward; Kramer, Arthur F.

2008-01-01

Previous studies have reported that high concentrations of homocysteine and lower concentrations of vitamin B6, B12, and folate increase the risk for cognitive decline and pathology in aging populations. In this cross-sectional study, high-resolution magnetic resonance imaging (MRI) scans and a 3-day food diary were collected on 32 community-dwelling adults between the ages of 59 and 79. We examined the relation between vitamin B6, B12, and folate intake on cortical volume using an optimized voxel-based morphometry (VBM) method and global gray and white matter volume after correcting for age, sex, body mass index, calorie intake, and education. All participants met or surpassed the recommended daily intake for these vitamins. In the VBM analysis, we found that adults with greater vitamin B6 intake had greater gray matter volume along the medial wall, anterior cingulate cortex, medial parietal cortex, middle temporal gyrus, and superior frontal gyrus, whereas people with greater B12 intake had greater volume in the left and right superior parietal sulcus. These effects were driven by vitamin supplementation and were negated when only examining vitamin intake from diet. Folate had no effect on brain volume. Furthermore, there was no relationship between vitamin B6, B12, or folate intake on global brain volume measures, indicating that VBM methods are more sensitive for detecting localized differences in gray matter volume than global measures. These results are discussed in relation to a growing literature on vitamin intake on age-related neurocognitive deterioration. PMID:18281020

Lower subcortical gray matter volume in both younger smokers and established smokers relative to non-smokers

PubMed Central

Hanlon, Colleen A.; Owens, Max M.; Joseph, Jane E.; Zhu, Xun; George, Mark S.; Brady, Kathleen T.; Hartwell, Karen J.

2014-01-01

Although established adult smokers with long histories of nicotine dependence have lower neural tissue volume than non-smokers, it is not clear if lower regional brain volume is also observed in younger, less established smokers. The primary goal of this study was to investigate neural tissue volume in a large group of smokers and non-smokers, with a secondary goal of measuring the impact of age on these effects. We used voxel-based morphometry to compare regional gray matter volume in 118 individuals (59 smokers, 59 age- and gender-matched non-smokers). Younger smokers had significantly lower gray matter volume in the left thalamus and the left amygdala than their non-smoking peers (family-wise error-corrected clusters, P < 0.05). There was no correlation between smoking use variables and tissue volume among younger smokers. Established smokers had significantly lower gray matter volume than age-matched non-smokers in the insula, parahippocampal gyrus and pallidum. Medial prefrontal cortex gray matter volume was negatively correlated with pack-years of smoking among the established smokers, but not the younger smokers. These data reveal that regional tissue volume differences are not limited exclusively to established smokers. Deficits in young adults indicate that cigarette smoking may either be deleterious to the thalamus and amygdala at an earlier age than previously reported, or that pre-existing differences in these areas may predispose individuals to the development of nicotine dependence. PMID:25125263

Set-up uncertainties: online correction with X-ray volume imaging.

PubMed

Kataria, Tejinder; Abhishek, Ashu; Chadha, Pranav; Nandigam, Janardhan

2011-01-01

To determine interfractional three-dimensional set-up errors using X-ray volumetric imaging (XVI). Between December 2007 and August 2009, 125 patients were taken up for image-guided radiotherapy using online XVI. After matching of reference and acquired volume view images, set-up errors in three translation directions were recorded and corrected online before treatment each day. Mean displacements, population systematic (Σ), and random (σ) errors were calculated and analyzed using SPSS (v16) software. Optimum clinical target volume (CTV) to planning target volume (PTV) margin was calculated using Van Herk's (2.5Σ + 0.7 σ) and Stroom's (2Σ + 0.7 σ) formula. Patients were grouped in 4 cohorts, namely brain, head and neck, thorax, and abdomen-pelvis. The mean vector displacement recorded were 0.18 cm, 0.15 cm, 0.36 cm, and 0.35 cm for brain, head and neck, thorax, and abdomen-pelvis, respectively. Analysis of individual mean set-up errors revealed good agreement with the proposed 0.3 cm isotropic margins for brain and 0.5 cm isotropic margins for head-neck. Similarly, 0.5 cm circumferential and 1 cm craniocaudal proposed margins were in agreement with thorax and abdomen-pelvic cases. The calculated mean displacements were well within CTV-PTV margin estimates of Van Herk (90% population coverage to minimum 95% prescribed dose) and Stroom (99% target volume coverage by 95% prescribed dose). Employing these individualized margins in a particular cohort ensure comparable target coverage as described in literature, which is further improved if XVI-aided set-up error detection and correction is used before treatment.

Factors affecting volume calculation with single photon emission tomography (SPECT) method

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

Liu, T.H.; Lee, K.H.; Chen, D.C.P.

1985-05-01

Several factors may influence the calculation of absolute volumes (VL) from SPECT images. The effect of these factors must be established to optimize the technique. The authors investigated the following on the VL calculations: % of background (BG) subtraction, reconstruction filters, sample activity, angular sampling and edge detection methods. Transaxial images of a liver-trunk phantom filled with Tc-99m from 1 to 3 ..mu..Ci/cc were obtained in 64x64 matrix with a Siemens Rota Camera and MDS computer. Different reconstruction filters including Hanning 20,32, 64 and Butterworth 20, 32 were used. Angular samplings were performed in 3 and 6 degree increments. ROI'smore » were drawn manually and with an automatic edge detection program around the image after BG subtraction. VL's were calculated by multiplying the number of pixels within the ROI by the slice thickness and the x- and y- calibrations of each pixel. One or 2 pixel per slice thickness was applied in the calculation. An inverse correlation was found between the calculated VL and the % of BG subtraction (r=0.99 for 1,2,3 ..mu..Ci/cc activity). Based on the authors' linear regression analysis, the correct liver VL was measured with about 53% BG subtraction. The reconstruction filters, slice thickness and angular sampling had only minor effects on the calculated phantom volumes. Detection of the ROI automatically by the computer was not as accurate as the manual method. The authors conclude that the % of BG subtraction appears to be the most important factor affecting the VL calculation. With good quality control and appropriate reconstruction factors, correct VL calculations can be achieved with SPECT.« less

Internal motion and its pressure dependence in FeSiF6+6/H2O/.

NASA Technical Reports Server (NTRS)

Vaughan, R. W.; Nicolaides, G. L.; Elleman, D. D.

1972-01-01

Both wideline and pulsed NMR techniques were used to examine the internal motion in FeSiF6+6(H2O). Corrections of second moments for bulk paramagnetic effects were essential. At room temperature and pressure, the fluorine-fluorine contribution to the 19F second moment is 0.38 (plus or minus 0.06) G2, and indicates rapid orientation of the SiF6(--) group. Analysis of the second moment within the transition region allows calculation of an activation volume which is 2.4 (plus or minus 0.4) % of the molar volume. The application of pressure slows the internal motion such that the rigid lattice values of the 19F second moment are obtained above 50 kbar.

Coexistence Curve of Perfluoromethylcyclohexane-Isopropyl Alcohol

NASA Technical Reports Server (NTRS)

Jacobs, D. T.; Kuhl, D. E.; Selby, C. E.

1996-01-01

The coexistence curve of the binary fluid mixture perfluoromethylcyclohexane-isopropyl alcohol was determined by precisely measuring the refractive index both above and below its upper critical consolute point. Sixty-seven two-phase data points were obtained over a wide range of reduced temperatures, 10(exp -5) less than t less than 2.5 x 10(exp -1), to determine the location of the critical point: critical temperature=89.901 C, and critical composition = 62.2% by volume perfluoromethylcyclohexane. These data were analyzed to determine the critical exponent 8 close to the critical point, the amplitude B, and the anomaly in the diameter. The volume-fraction coexistence curve is found to be as symmetric as any composition like variable. Correction to scaling is investigated as well as the need for a crossover theory. A model is proposed that describes the asymptotic approach to zero of the effective exponent Beta, which allows an estimation of the temperature regime free of crossover effects.

Zero-Headspace Coal-Core Gas Desorption Canister, Revised Desorption Data Analysis Spreadsheets and a Dry Canister Heating System

USGS Publications Warehouse

Barker, Charles E.; Dallegge, Todd A.

2005-01-01

Coal desorption techniques typically use the U.S. Bureau of Mines (USBM) canister-desorption method as described by Diamond and Levine (1981), Close and Erwin (1989), Ryan and Dawson (1993), McLennan and others (1994), Mavor and Nelson (1997) and Diamond and Schatzel (1998). However, the coal desorption canister designs historically used with this method have an inherent flaw that allows a significant gas-filled headspace bubble to remain in the canister that later has to be compensated for by correcting the measured desorbed gas volume with a mathematical headspace volume correction (McLennan and others, 1994; Mavor and Nelson, 1997).

Eddy current correction in volume-localized MR spectroscopy

NASA Technical Reports Server (NTRS)

Lin, C.; Wendt, R. E. 3rd; Evans, H. J.; Rowe, R. M.; Hedrick, T. D.; LeBlanc, A. D.

1994-01-01

The quality of volume-localized magnetic resonance spectroscopy is affected by eddy currents caused by gradient switching. Eddy currents can be reduced with improved gradient systems; however, it has been suggested that the distortion due to eddy currents can be compensated for during postprocessing with a single-frequency reference signal. The authors propose modifying current techniques for acquiring the single-frequency reference signal by using relaxation weighting to reduce interference from components that cannot be eliminated by digital filtering alone. Additional sequences with T1 or T2 weighting for reference signal acquisition are shown to have the same eddy current characteristics as the original signal without relaxation weighting. The authors also studied a new eddy current correction method that does not require a single-frequency reference signal. This method uses two free induction decays (FIDs) collected from the same volume with two sequences with opposite gradients. Phase errors caused by eddy currents are opposite in these two FIDs and can be canceled completely by combining the FIDs. These methods were tested in a phantom. Eddy current distortions were corrected, allowing quantitative measurement of structures such as the -CH = CH- component, which is otherwise undetectable.

Safety Education Handbook. Volume 2.

ERIC Educational Resources Information Center

Kansas State Dept. of Education, Topeka.

This is the second of three volumes of a safety guide developed to assist Kansas administrators and teachers in organizing, evaluating, and maintaining safety programs. It provides information to help them identify, assess, and correct unsafe conditions relating to equipment and facilities and ensure a safe and healthy environment for themselves…

Equipment for the Disabled. Volumes 1 - 4.

ERIC Educational Resources Information Center

Wilshere, E. Rosamond, Comp.

Four volumes of equipment for the disabled which can simplify their lives and those who live with them are presented. The authors have not included surgical, medical, therapeutic, corrective or gymnastic equipment in the publication. Voume one includes house adaptations and planning, beds and bed accessories, chairs, and wheelchairs and…

Safety Education Handbook. Volume 3.

ERIC Educational Resources Information Center

Kansas State Dept. of Education, Topeka.

This is the third of three volumes of a safety guide developed to assist Kansas administrators and teachers in organizing, evaluating, and maintaining safety programs. It provides information to help them identify, assess, and correct unsafe conditions relating to equipment and facilities and ensure a safe and healthy environment for themselves…

The Coast Artillery Journal. Volume 66, Number 6, June 1927

DTIC Science & Technology

1927-06-01

on the fuse setter it serves to determine the length of the fuse powder train. With the firing tables as a basis, data computers are constructed to...continuously by means of a wind computer and applied on the guns. In trial fire, therefore, wind effects are carefnlly eliminated before the corrections...are computed . (2) Change in the muzzle velocity. This result may he due to 488 THE COAST ARTILLERY JOURNAL change in the quality, weight, or

Correction for FDG PET dose extravasations: Monte Carlo validation and quantitative evaluation of patient studies.

PubMed

Silva-Rodríguez, Jesús; Aguiar, Pablo; Sánchez, Manuel; Mosquera, Javier; Luna-Vega, Víctor; Cortés, Julia; Garrido, Miguel; Pombar, Miguel; Ruibal, Alvaro

2014-05-01

Current procedure guidelines for whole body [18F]fluoro-2-deoxy-D-glucose (FDG)-positron emission tomography (PET) state that studies with visible dose extravasations should be rejected for quantification protocols. Our work is focused on the development and validation of methods for estimating extravasated doses in order to correct standard uptake value (SUV) values for this effect in clinical routine. One thousand three hundred sixty-seven consecutive whole body FDG-PET studies were visually inspected looking for extravasation cases. Two methods for estimating the extravasated dose were proposed and validated in different scenarios using Monte Carlo simulations. All visible extravasations were retrospectively evaluated using a manual ROI based method. In addition, the 50 patients with higher extravasated doses were also evaluated using a threshold-based method. Simulation studies showed that the proposed methods for estimating extravasated doses allow us to compensate the impact of extravasations on SUV values with an error below 5%. The quantitative evaluation of patient studies revealed that paravenous injection is a relatively frequent effect (18%) with a small fraction of patients presenting considerable extravasations ranging from 1% to a maximum of 22% of the injected dose. A criterion based on the extravasated volume and maximum concentration was established in order to identify this fraction of patients that might be corrected for paravenous injection effect. The authors propose the use of a manual ROI based method for estimating the effectively administered FDG dose and then correct SUV quantification in those patients fulfilling the proposed criterion.

Correction for FDG PET dose extravasations: Monte Carlo validation and quantitative evaluation of patient studies

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

Silva-Rodríguez, Jesús, E-mail: jesus.silva.rodriguez@sergas.es; Aguiar, Pablo, E-mail: pablo.aguiar.fernandez@sergas.es; Servicio de Medicina Nuclear, Complexo Hospitalario Universidade de Santiago de Compostela

Purpose: Current procedure guidelines for whole body [18F]fluoro-2-deoxy-D-glucose (FDG)-positron emission tomography (PET) state that studies with visible dose extravasations should be rejected for quantification protocols. Our work is focused on the development and validation of methods for estimating extravasated doses in order to correct standard uptake value (SUV) values for this effect in clinical routine. Methods: One thousand three hundred sixty-seven consecutive whole body FDG-PET studies were visually inspected looking for extravasation cases. Two methods for estimating the extravasated dose were proposed and validated in different scenarios using Monte Carlo simulations. All visible extravasations were retrospectively evaluated using a manualmore » ROI based method. In addition, the 50 patients with higher extravasated doses were also evaluated using a threshold-based method. Results: Simulation studies showed that the proposed methods for estimating extravasated doses allow us to compensate the impact of extravasations on SUV values with an error below 5%. The quantitative evaluation of patient studies revealed that paravenous injection is a relatively frequent effect (18%) with a small fraction of patients presenting considerable extravasations ranging from 1% to a maximum of 22% of the injected dose. A criterion based on the extravasated volume and maximum concentration was established in order to identify this fraction of patients that might be corrected for paravenous injection effect. Conclusions: The authors propose the use of a manual ROI based method for estimating the effectively administered FDG dose and then correct SUV quantification in those patients fulfilling the proposed criterion.« less

Using resting-state fMRI to assess the effect of aerobic exercise on functional connectivity of the DLPFC in older overweight adults.

PubMed

Prehn, Kristin; Lesemann, Anne; Krey, Georgia; Witte, A Veronica; Köbe, Theresa; Grittner, Ulrike; Flöel, Agnes

2017-08-23

Cardiovascular fitness is thought to exert beneficial effects on brain function and might delay the onset of cognitive decline. Empirical evidence of exercise-induced cognitive enhancement, however, has not been conclusive, possibly due to short intervention times in clinical trials. Resting-state functional connectivity (RSFC) has been proposed asan early indicator for intervention-induced changes. Here, we conducted a study in which healthy older overweight subjects took either part in a moderate aerobic exercise program over 6months (AE group; n=11) or control condition of non-aerobic stretching and toning (NAE group; n=18). While cognitive and gray matter volume changes were rather small (i.e., appeared only in certain sub-scores without Bonferroni correction for multiple comparisons or using small volume correction), we found significantly increased RSFC after training between dorsolateral prefrontal cortex and superior parietal gyrus/precuneus in the AE compared to the NAE group. This intervention study demonstrates an exercise-induced modulation of RSFC between key structures of the executive control and default mode networks, which might mediate an interaction between task-positive and task-negative brain activation required for task switching. Results further emphasize the value of RSFC asa sensitive biomarker for detecting early intervention-related cognitive improvements in clinical trials. Copyright © 2017 Elsevier Inc. All rights reserved.

SU-F-T-492: The Impact of Water Temperature On Absolute Dose Calibration

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

Islam, N; Podgorsak, M; Roswell Park Cancer Institute, Buffalo, NY

Purpose: The Task Group 51 (TG 51) protocol prescribes that dose calibration of photon beams be done by irradiating an ionization chamber in a water tank at pre-defined depths. Methodologies are provided to account for variations in measurement conditions by applying correction factors. However, the protocol does not completely account for the impact of water temperature. It is well established that water temperature will influence the density of air in the ion chamber collecting volume. Water temperature, however, will also influence the size of the collecting volume via thermal expansion of the cavity wall and the density of the watermore » in the tank. In this work the overall effect of water temperature on absolute dosimetry has been investigated. Methods: Dose measurements were made using a Farmer-type ion chamber for 6 and 23 MV photon beams with water temperatures ranging from 10 to 40°C. A reference ion chamber was used to account for fluctuations in beam output between successive measurements. Results: For the same beam output, the dose determined using TG 51 was dependent on the temperature of the water in the tank. A linear regression of the data suggests that the dependence is statistically significant with p-values of the slope equal to 0.003 and 0.01 for 6 and 23 MV beams, respectively. For a 10 degree increase in water phantom temperature, the absolute dose determined with TG 51 increased by 0.27% and 0.31% for 6 and 23 MV beams, respectively. Conclusion: There is a measurable effect of water temperature on absolute dose calibration. To account for this effect, a reference temperature can be defined and a correction factor applied to account for deviations from this reference temperature during beam calibration. Such a factor is expected to be of similar magnitude to most of the existing TG 51 correction factors.« less

Evaluation metrics for bone segmentation in ultrasound

NASA Astrophysics Data System (ADS)

Lougheed, Matthew; Fichtinger, Gabor; Ungi, Tamas

2015-03-01

Tracked ultrasound is a safe alternative to X-ray for imaging bones. The interpretation of bony structures is challenging as ultrasound has no specific intensity characteristic of bones. Several image segmentation algorithms have been devised to identify bony structures. We propose an open-source framework that would aid in the development and comparison of such algorithms by quantitatively measuring segmentation performance in the ultrasound images. True-positive and false-negative metrics used in the framework quantify algorithm performance based on correctly segmented bone and correctly segmented boneless regions. Ground-truth for these metrics are defined manually and along with the corresponding automatically segmented image are used for the performance analysis. Manually created ground truth tests were generated to verify the accuracy of the analysis. Further evaluation metrics for determining average performance per slide and standard deviation are considered. The metrics provide a means of evaluating accuracy of frames along the length of a volume. This would aid in assessing the accuracy of the volume itself and the approach to image acquisition (positioning and frequency of frame). The framework was implemented as an open-source module of the 3D Slicer platform. The ground truth tests verified that the framework correctly calculates the implemented metrics. The developed framework provides a convenient way to evaluate bone segmentation algorithms. The implementation fits in a widely used application for segmentation algorithm prototyping. Future algorithm development will benefit by monitoring the effects of adjustments to an algorithm in a standard evaluation framework.

Effect of nitric oxide, perfluorocarbon, and heliox on minute volume measurement and ventilator volumes delivered.

PubMed

Devabhaktuni, V G; Torres, A; Wilson, S; Yeh, M P

1999-08-01

To determine the effect of heliox, nitric oxide (NO), and perfluorocarbon on differential pressure pneumotachometer characteristics and to determine the effect of heliox on volumes delivered by the Siemens S900C (S900C), and Servo Ventilator 300 (SV300) ventilators. Prospective, laboratory study. Pulmonary laboratory of a tertiary care, nonprofit children's hospital. SV300, S900C ventilator, differential pressure pneumotachometer. Dual pneumotachometers were connected in series to a 0.5-L calibration syringe and a 1-L anesthesia bag creating a closed system. Calibration of the pneumotachometers was done in room air at ambient temperature with 100 strokes. Accepted accuracy of measured volumes is within 0.5%. Flow-conductance curves were constructed using 100 strokes each for heliox (70:30 mixture), NO, and perfluorocarbon. Expired gases of room air and a 70:30 mixture of heliox from the above ventilators were collected into a nondiffusing gas collection bag, and the volume was measured in a chain-compensated gasometer. Ten sets of 500-mL breaths (20 breaths each set) and 100-mL breaths (40 breaths each set) were collected. The paired Student's t-test was used to detect significant differences in measured volumes, with significance defined as p < .01. Volumes measured with the pneumotachometer using 25 ppm of NO, 50 ppm of NO, and perfluorocarbon were within +0.25%, -0.7%, and +0.4%, respectively (p = .155, p = .001, p = .06). Heliox decreased the conductance of the pneumotachometer, thereby increasing the measured volume by 15% (p < .001). However, heliox did not affect its linearity. Heliox had no affect on volumes delivered by the S900C. However, the SV300 delivered 7.9% less volume of heliox at a set tidal volume of 500 mL and 10.8% less at a set tidal volume of 100 mL. A 70:30 mixture of heliox caused a significantly overestimated gas volume measured and, therefore, an underestimated gas volume delivered by SV300. NO at 25 ppm and perfluorocarbon did not interfere with the accuracy of a differential pressure pneumotachometer. However, at 50 ppm, NO caused a difference in measured gas volume that was statistically, but not clinically, significant. Application of pneumotachometers in critically ill children receiving heliox requires recalibration. Heliox did not affect volumes delivered with the S900C ventilator. Although volumes delivered with the SV300 were significantly reduced by heliox, the difference can be corrected easily by increasing minute ventilation until expired tidal volume equals desired tidal volume.

LANDSAT-D data format control book. Volume 6, appendix D: Thematic mapper Computer Compatible Tape (CCT-AT/PT)

NASA Technical Reports Server (NTRS)

Ahmed, H.

1981-01-01

The format of computer compatible tapes which contain LANDSAT 4 and D Prime thematic mapper data is defined. A complete specification of the CCT-AT (radiometric corrections applied and geometric matrices appended) and the CCT-PT (radiometric and geometric corrections) data formats is provided.

Serum vitamin D and hippocampal gray matter volume in schizophrenia.

PubMed

Shivakumar, Venkataram; Kalmady, Sunil V; Amaresha, Anekal C; Jose, Dania; Narayanaswamy, Janardhanan C; Agarwal, Sri Mahavir; Joseph, Boban; Venkatasubramanian, Ganesan; Ravi, Vasanthapuram; Keshavan, Matcheri S; Gangadhar, Bangalore N

2015-08-30

Disparate lines of evidence including epidemiological and case-control studies have increasingly implicated vitamin D in the pathogenesis of schizophrenia. Vitamin D deficiency can lead to dysfunction of the hippocampus--a brain region hypothesized to be critically involved in schizophrenia. In this study, we examined for potential association between serum vitamin D level and hippocampal gray matter volume in antipsychotic-naïve or antipsychotic-free schizophrenia patients (n = 35). Serum vitamin D level was estimated using 25-OH vitamin D immunoassay. Optimized voxel-based morphometry was used to analyze 3-Tesla magnetic resonance imaging (MRI) (1-mm slice thickness). Ninety-seven percent of the schizophrenia patients (n = 34) had sub-optimal levels of serum vitamin D (83%, deficiency; 14%, insufficiency). A significant positive correlation was seen between vitamin D and regional gray matter volume in the right hippocampus after controlling for age, years of education and total intracranial volume (Montreal Neurological Institute (MNI) coordinates: x = 35, y = -18, z = -8; t = 4.34 pFWE(Corrected) = 0.018). These observations support a potential role of vitamin D deficiency in mediating hippocampal volume deficits, possibly through neurotrophic, neuroimmunomodulatory and glutamatergic effects. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

OPC care-area feedforwarding to MPC

NASA Astrophysics Data System (ADS)

Dillon, Brian; Peng, Yi-Hsing; Hamaji, Masakazu; Tsunoda, Dai; Muramatsu, Tomoyuki; Ohara, Shuichiro; Zou, Yi; Arnoux, Vincent; Baron, Stanislas; Zhang, Xiaolong

2016-10-01

Demand for mask process correction (MPC) is growing for leading-edge process nodes. MPC was originally intended to correct CD linearity for narrow assist features difficult to resolve on a photomask without any correction, but it has been extended to main features as process nodes have been shrinking. As past papers have observed, MPC shows improvements in photomask fidelity. Using advanced shape and dose corrections could give more improvements, especially at line-ends and corners. However, there is a dilemma on using such advanced corrections on full mask level because it increases data volume and run time. In addition, write time on variable shaped beam (VSB) writers also increases as the number of shots increases. Optical proximity correction (OPC) care-area defines circuit design locations that require high mask fidelity under mask writing process variations such as energy fluctuation. It is useful for MPC to switch its correction strategy and permit the use of advanced mask correction techniques in those local care-areas where they provide maximum wafer benefits. The use of mask correction techniques tailored to localized post-OPC design can result in similar desired level of data volume, run time, and write time. ASML Brion and NCS have jointly developed a method to feedforward the care-area information from Tachyon LMC to NDE-MPC to provide real benefit for improving both mask writing and wafer printing quality. This paper explains the detail of OPC care-area feedforwarding to MPC between ASML Brion and NCS, and shows the results. In addition, improvements on mask and wafer simulations are also shown. The results indicate that the worst process variation (PV) bands are reduced up to 37% for a 10nm tech node metal case.

Investigation of brain structure in the 1-month infant.

PubMed

Dean, Douglas C; Planalp, E M; Wooten, W; Schmidt, C K; Kecskemeti, S R; Frye, C; Schmidt, N L; Goldsmith, H H; Alexander, A L; Davidson, R J

2018-05-01

The developing brain undergoes systematic changes that occur at successive stages of maturation. Deviations from the typical neurodevelopmental trajectory are hypothesized to underlie many early childhood disorders; thus, characterizing the earliest patterns of normative brain development is essential. Recent neuroimaging research provides insight into brain structure during late childhood and adolescence; however, few studies have examined the infant brain, particularly in infants under 3 months of age. Using high-resolution structural MRI, we measured subcortical gray and white matter brain volumes in a cohort (N = 143) of 1-month infants and examined characteristics of these volumetric measures throughout this early period of neurodevelopment. We show that brain volumes undergo age-related changes during the first month of life, with the corresponding patterns of regional asymmetry and sexual dimorphism. Specifically, males have larger total brain volume and volumes differ by sex in regionally specific brain regions, after correcting for total brain volume. Consistent with findings from studies of later childhood and adolescence, subcortical regions appear more rightward asymmetric. Neither sex differences nor regional asymmetries changed with gestation-corrected age. Our results complement a growing body of work investigating the earliest neurobiological changes associated with development and suggest that asymmetry and sexual dimorphism are present at birth.

The plasticity of extracellular fluid homeostasis in insects.

PubMed

Beyenbach, Klaus W

2016-09-01

In chemistry, the ratio of all dissolved solutes to the solution's volume yields the osmotic concentration. The present Review uses this chemical perspective to examine how insects deal with challenges to extracellular fluid (ECF) volume, solute content and osmotic concentration (pressure). Solute/volume plots of the ECF (hemolymph) reveal that insects tolerate large changes in all three of these ECF variables. Challenges beyond those tolerances may be 'corrected' or 'compensated'. While a correction simply reverses the challenge, compensation accommodates the challenge with changes in the other two variables. Most insects osmoregulate by keeping ECF volume and osmotic concentration within a wide range of tolerance. Other insects osmoconform, allowing the ECF osmotic concentration to match the ambient osmotic concentration. Aphids are unique in handling solute and volume loads largely outside the ECF, in the lumen of the gut. This strategy may be related to the apparent absence of Malpighian tubules in aphids. Other insects can suspend ECF homeostasis altogether in order to survive extreme temperatures. Thus, ECF homeostasis in insects is highly dynamic and plastic, which may partly explain why insects remain the most successful class of animals in terms of both species number and biomass. © 2016. Published by The Company of Biologists Ltd.

Gay-Lussac Did Better Than He Knew

NASA Astrophysics Data System (ADS)

Holbrow, Charles H.; Amato, Joseph C.

2011-04-01

In his 1802 paper Joseph Louis Gay-Lussac reported the first definitive experimental evidence that many different gases exhibit the same fractional expansion of volume when heated. This property is known as Charles Law, Amontons Law, Dalton's Law, or the law of volumes. Gay-Lussac concluded from his experiments that many gases expand by 37.5% when heated from 0 ,oC to 100,oC. Although his result is within 2.5% of the modern value of 36.6% = 100/273.15, the discrepancy is surprising because his direct and simple experimental method allowed him to measure changes in volume with a precision of a few tenths of a percent. An examination of his original paper suggests, however, that he did not take into account that his measurements of the initial and final volumes of gas were made at slightly different pressures. With reasonable assumptions about the diagrams in his paper, one can use Pascal's law and the ideal gas law to correct the measured volumes so that they correspond to the same initial and final pressure. With this correction the results imply δV/V = .366. Gay-Lussac did better than he knew.

Structural Impairments of Hippocampus in Coal Mine Gas Explosion-Related Posttraumatic Stress Disorder

PubMed Central

Lang, Xu; Li, Huabing; Qin, Wen; Yu, Chunshui

2014-01-01

Investigations on hippocampal and amygdalar volume have revealed inconsistent results in patients with posttraumatic stress disorder (PTSD). Little is known about the structural covariance alterations between the hippocampus and amygdala in PTSD. In this study, we evaluated the alteration in the hippocampal and amygdalar volume and their structural covariance in the coal mine gas explosion related PTSD. High resolution T1-weighted magnetic resonance imaging (MRI) was performed on coal mine gas explosion related PTSD male patients (n = 14) and non-traumatized coalminers without PTSD (n = 25). The voxel-based morphometry (VBM) method was used to test the inter-group differences in hippocampal and amygdalar volume as well as the inter-group differences in structural covariance between the ipsilateral hippocampus and amygdala. PTSD patients exhibited decreased gray matter volume (GMV) in the bilateral hippocampi compared to controls (p<0.05, FDR corrected). GMV covariances between the ipsilateral hippocampus and amygdala were significantly reduced in PTSD patients compared with controls (p<0.05, FDR corrected). The coalminers with gas explosion related PTSD had decreased hippocampal volume and structural covariance with the ipsilateral amygdala, suggesting that the structural impairment of the hippocampus may implicate in the pathophysiology of PTSD. PMID:25000505

GWAS-identified risk variants for major depressive disorder: Preliminary support for an association with late-life depressive symptoms and brain structural alterations.

PubMed

Ryan, Joanne; Artero, Sylvaine; Carrière, Isabelle; Maller, Jerome J; Meslin, Chantal; Ritchie, Karen; Ancelin, Marie-Laure

2016-01-01

A number of genome-wide association studies (GWAS) have investigated risk factors for major depressive disorder (MDD), however there has been little attempt to replicate these findings in population-based studies of depressive symptoms. Variants within three genes, BICC1, PCLO and GRM7 were selected for replication in our study based on the following criteria: they were identified in a prior MDD GWAS study; a subsequent study found evidence that they influenced depression risk; and there is a solid biological basis for a role in depression. We firstly investigated whether these variants were associated with depressive symptoms in our population-based cohort of 929 elderly (238 with clinical depressive symptoms and 691 controls), and secondly to investigate associations with structural brain alterations. A number of nominally significant associations were identified, but none reached Bonferroni-corrected significance levels. Common SNPs in BICC1 and PCLO were associated with a 50% and 30% decreased risk of depression, respectively. PCLO rs2522833 was also associated with the volume of grey matter (p=1.6×10(-3)), and to a lesser extent with hippocampal volume and white matter lesions. Among depressed individuals rs9870680 (GRM7) was associated with the volume of grey and white matter (p=10(-4) and 8.3×10(-3), respectively). Our results provide some support for the involvement of BICC1 and PCLO in late-life depressive disorders and preliminary evidence that these genetic variants may also influence brain structural volumes. However effect sizes remain modest and associations did not reach corrected significance levels. Further large imaging studies are needed to confirm our findings. Copyright © 2015 Elsevier B.V. and ECNP. All rights reserved.

Finite element simulation of texture evolution and Swift effect in NiAl under torsion

NASA Astrophysics Data System (ADS)

Böhlke, Thomas; Glüge, Rainer; Klöden, Burghardt; Skrotzki, Werner; Bertram, Albrecht

2007-09-01

The texture evolution and the Swift effect in NiAl under torsion at 727 °C are studied by finite element simulations for two different initial textures. The material behaviour is modelled by an elastic-viscoplastic Taylor model. In order to overcome the well-known shortcomings of Taylor's approach, the texture evolution is also investigated by a representative volume element (RVE) with periodic boundary conditions and a compatible microstructure at the opposite faces of the RVE. Such a representative volume element takes into account the grain morphology and the grain interaction. The numerical results are compared with experimental data. It is shown that the modelling of a finite element based RVE leads to a better prediction of the final textures. However, the texture evolution path is not accounted for correctly. The simulated Swift effect depends much more on the initial orientation distribution than observed in experiment. Deviations between simulation and experiment may be due to continuous dynamic recrystallization.

Sex differences in the correlation of emotional control and amygdala volumes in adolescents.

PubMed

Blanton, Rebecca E; Chaplin, Tara M; Sinha, Rajita

2010-10-06

We examined male and female adolescents (8-18 years of age) that were scanned with structural brain MRI and looked for a correlation between volume of the right or the left amygdala and parent-reported ability of emotional control. A sex difference was found in the correlation between emotional control and the corrected volume of the left amygdala (that is the amygdala volume adjusted for total cranial volume). In girls, smaller left amygdala volumes were associated with better emotional control. In boys, larger left amygdala volumes were associated with better emotional control. These findings suggest that healthy girls and boys show a difference in the correlation between parental reports of emotional control and the left amygdala volume.

The "'Grammar Correction' Debate in L2 Writing": Where Are We, and Where Do We Go from Here?--(And What Do We Do in the Meantime ...?)

ERIC Educational Resources Information Center

Ferris, Dana R.

2004-01-01

The efficacy of teacher error/grammar correction in second language writing classes has been the subject of much controversy, including a published debate in an earlier volume of this journal [J. Second Language Writing 8 (1999) 1; J. Second Language Writing 8 (1999) 111]. In this paper, the state-of-the-art in error correction research in L2…

Reproducible MRI Measurement of Adipose Tissue Volumes in Genetic and Dietary Rodent Obesity Models

PubMed Central

Johnson, David H.; Flask, Chris A.; Ernsberger, Paul R.; Wong, Wilbur C. K.; Wilson, David L.

2010-01-01

Purpose To develop ratio MRI [lipid/(lipid+water)] methods for assessing lipid depots and compare measurement variability to biological differences in lean controls (spontaneously hypertensive rats, SHRs), dietary obese (SHR-DO), and genetic/dietary obese (SHROBs) animals. Materials and Methods Images with and without CHESS water-suppression were processed using a semi-automatic method accounting for relaxometry, chemical shift, receive coil sensitivity, and partial volume. Results Partial volume correction improved results by 10–15%. Over six operators, volume variation was reduced to 1.9 ml from 30.6 ml for single-image-analysis with intensity inhomogeneity. For three acquisitions on the same animal, volume reproducibility was <1%. SHROBs had 6X visceral and 8X subcutaneous adipose tissue than SHRs. SHR-DOs had enlarged visceral depots (3X SHRs). SHROB had significantly more subcutaneous adipose tissue, indicating a strong genetic component to this fat depot. Liver ratios in SHR-DO and SHROB were higher than SHR, indicating elevated fat content. Among SHROBs, evidence suggested a phenotype SHROB* having elevated liver ratios and visceral adipose tissue volumes. Conclusion Effects of diet and genetics on obesity were significantly larger than variations due to image acquisition and analysis, indicating that these methods can be used to assess accumulation/depletion of lipid depots in animal models of obesity. PMID:18821617

PSF mapping-based correction of eddy-current-induced distortions in diffusion-weighted echo-planar imaging.

PubMed

In, Myung-Ho; Posnansky, Oleg; Speck, Oliver

2016-05-01

To accurately correct diffusion-encoding direction-dependent eddy-current-induced geometric distortions in diffusion-weighted echo-planar imaging (DW-EPI) and to minimize the calibration time at 7 Tesla (T). A point spread function (PSF) mapping based eddy-current calibration method is newly presented to determine eddy-current-induced geometric distortions even including nonlinear eddy-current effects within the readout acquisition window. To evaluate the temporal stability of eddy-current maps, calibration was performed four times within 3 months. Furthermore, spatial variations of measured eddy-current maps versus their linear superposition were investigated to enable correction in DW-EPIs with arbitrary diffusion directions without direct calibration. For comparison, an image-based eddy-current correction method was additionally applied. Finally, this method was combined with a PSF-based susceptibility-induced distortion correction approach proposed previously to correct both susceptibility and eddy-current-induced distortions in DW-EPIs. Very fast eddy-current calibration in a three-dimensional volume is possible with the proposed method. The measured eddy-current maps are very stable over time and very similar maps can be obtained by linear superposition of principal-axes eddy-current maps. High resolution in vivo brain results demonstrate that the proposed method allows more efficient eddy-current correction than the image-based method. The combination of both PSF-based approaches allows distortion-free images, which permit reliable analysis in diffusion tensor imaging applications at 7T. © 2015 Wiley Periodicals, Inc.

Comparison of silver and molybdenum microfocus X-ray sources for single-crystal structure determination.

PubMed

Krause, Lennard; Herbst-Irmer, Regine; Sheldrick, George M; Stalke, Dietmar

2015-02-01

The quality of diffraction data obtained using silver and molybdenum microsources has been compared for six model compounds with a wide range of absorption factors. The experiments were performed on two 30 W air-cooled Incoatec IµS microfocus sources with multilayer optics mounted on a Bruker D8 goniometer with a SMART APEX II CCD detector. All data were analysed, processed and refined using standard Bruker software. The results show that Ag  K α radiation can be beneficial when heavy elements are involved. A numerical absorption correction based on the positions and indices of the crystal faces is shown to be of limited use for the highly focused microsource beams, presumably because the assumption that the crystal is completely bathed in a (top-hat profile) beam of uniform intensity is no longer valid. Fortunately the empirical corrections implemented in SADABS , although originally intended as a correction for absorption, also correct rather well for the variations in the effective volume of the crystal irradiated. In three of the cases studied (two Ag and one Mo) the final SHELXL R 1 against all data after application of empirical corrections implemented in SADABS was below 1%. Since such corrections are designed to optimize the agreement of the intensities of equivalent reflections with different paths through the crystal but the same Bragg 2θ angles, a further correction is required for the 2θ dependence of the absorption. For this, SADABS uses the transmission factor of a spherical crystal with a user-defined value of μ r (where μ is the linear absorption coefficient and r is the effective radius of the crystal); the best results are obtained when r is biased towards the smallest crystal dimension. The results presented here suggest that the IUCr publication requirement that a numerical absorption correction must be applied for strongly absorbing crystals is in need of revision.

Finite size effects in the thermodynamics of a free neutral scalar field

NASA Astrophysics Data System (ADS)

Parvan, A. S.

2018-04-01

The exact analytical lattice results for the partition function of the free neutral scalar field in one spatial dimension in both the configuration and the momentum space were obtained in the framework of the path integral method. The symmetric square matrices of the bilinear forms on the vector space of fields in both configuration space and momentum space were found explicitly. The exact lattice results for the partition function were generalized to the three-dimensional spatial momentum space and the main thermodynamic quantities were derived both on the lattice and in the continuum limit. The thermodynamic properties and the finite volume corrections to the thermodynamic quantities of the free real scalar field were studied. We found that on the finite lattice the exact lattice results for the free massive neutral scalar field agree with the continuum limit only in the region of small values of temperature and volume. However, at these temperatures and volumes the continuum physical quantities for both massive and massless scalar field deviate essentially from their thermodynamic limit values and recover them only at high temperatures or/and large volumes in the thermodynamic limit.

Intra-fraction motion of larynx radiotherapy

NASA Astrophysics Data System (ADS)

Durmus, Ismail Faruk; Tas, Bora

2018-02-01

In early stage laryngeal radiotherapy, movement is an important factor. Thyroid cartilage can move from swallowing, breathing, sound and reflexes. The effects of this motion on the target volume (PTV) during treatment were examined. In our study, the target volume movement during the treatment for this purpose was examined. Thus, setup margins are re-evaluated and patient-based PTV margins are determined. Intrafraction CBCT was scanned in 246 fractions for 14 patients. During the treatment, the amount of deviation which could be lateral, vertical and longitudinal axis was determined. ≤ ± 0.1cm deviation; 237 fractions in the lateral direction, 202 fractions in the longitudinal direction, 185 fractions in the vertical direction. The maximum deviation values were found in the longitudinal direction. Intrafraction guide in laryngeal radiotherapy; we are sure of the correctness of the treatment, the target volume is to adjust the margin and dose more precisely, we control the maximum deviation of the target volume for each fraction. Although the image quality of intrafraction-CBCT scans was lower than the image quality of planning CT, they showed sufficient contrast for this work.

Neonatal hygroscopic condenser humidifier.

PubMed

Gedeon, A; Mebius, C; Palmer, K

1987-01-01

A hygroscopic condenser humidifier was developed for neonates on mechanical ventilation and was evaluated by laboratory tests and clinically. Humidification provided by the unit was measured in the 10- to 50-ml tidal-volume range at ambient temperatures of 24 degrees C and 38 degrees C. The effect of a leaking patient connection on device performance was investigated. Leakage rates were measured routinely in a neonatal ICU and surgery to determine the clinical significance. In the entire tidal volume and temperature range, the unit provided an inspiratory water content in excess of 30 g/m3 when the leak fraction (volume leaked/volume delivered at Y-piece) was less than 15%. This was found in three out of four cases. In about one out of ten cases, the leak exceeded 30%, which invariably led to corrective action, such as repositioning or changing the endotracheal tube. However, even at a 30% leak, a water content of about 26 g/m3 was still available for humidifying the inspired gas, which corresponds to normal physiologic conditions found in the trachea for nasal breathing of room air.

White Matter Volume Predicts Language Development in Congenital Heart Disease.

PubMed

Rollins, Caitlin K; Asaro, Lisa A; Akhondi-Asl, Alireza; Kussman, Barry D; Rivkin, Michael J; Bellinger, David C; Warfield, Simon K; Wypij, David; Newburger, Jane W; Soul, Janet S

2017-02-01

To determine whether brain volume is reduced at 1 year of age and whether these volumes are associated with neurodevelopment in biventricular congenital heart disease (CHD) repaired in infancy. Infants with biventricular CHD (n = 48) underwent brain magnetic resonance imaging (MRI) and neurodevelopmental testing with the Bayley Scales of Infant Development-II and the MacArthur-Bates Communicative Development Inventories at 1 year of age. A multitemplate based probabilistic segmentation algorithm was applied to volumetric MRI data. We compared volumes with those of 13 healthy control infants of comparable ages. In the group with CHD, we measured Spearman correlations between neurodevelopmental outcomes and the residuals from linear regression of the volumes on corrected chronological age at MRI and sex. Compared with controls, infants with CHD had reductions of 54 mL in total brain (P = .009), 40 mL in cerebral white matter (P <.001), and 1.2 mL in brainstem (P = .003) volumes. Within the group with CHD, brain volumes were not correlated with Bayley Scales of Infant Development-II scores but did correlate positively with MacArthur-Bates Communicative Development Inventory language development. Infants with biventricular CHD show total brain volume reductions at 1 year of age, driven by differences in cerebral white matter. White matter volume correlates with language development, but not broader developmental indices. These findings suggest that abnormalities in white matter development detected months after corrective heart surgery may contribute to language impairment. ClinicalTrials.gov: NCT00006183. Copyright © 2016 Elsevier Inc. All rights reserved.

Statistical distribution of the vacuum energy density in racetrack Kähler uplift models in string theory

NASA Astrophysics Data System (ADS)

Sumitomo, Yoske; Tye, S.-H. Henry; Wong, Sam S. C.

2013-07-01

We study a racetrack model in the presence of the leading α'-correction in flux compactification in Type IIB string theory, for the purpose of getting conceivable de-Sitter vacua in the large compactified volume approximation. Unlike the Kähler Uplift model studied previously, the α'-correction is more controllable for the meta-stable de-Sitter vacua in the racetrack case since the constraint on the compactified volume size is very much relaxed. We find that the vacuum energy density Λ for de-Sitter vacua approaches zero exponentially as the volume grows. We also analyze properties of the probability distribution of Λ in this class of models. As in other cases studied earlier, the probability distribution again peaks sharply at Λ = 0. We also study the Racetrack Kähler Uplift model in the Swiss-Cheese type model.

What Gay-Lussac didn't tell us

NASA Astrophysics Data System (ADS)

Holbrow, C. H.; Amato, J. C.

2011-01-01

Gay-Lussac's 1801 experiments establishing the law of volumes for gases are brilliantly simple, and he described them with a level of detail that was new to physics writing. But he did not present his actual measurements or tell us how he analyzed them to conclude that between 0 to 100 °C, a volume of any gas will expand by about 37.5%. We review his experiments and conclude that he measured initial and final volumes at slightly different pressures. By using the gas laws and his apparatus diagrams, we corrected his data so that they correspond to constant pressure. His corrected results give ΔV/V=36.6%, the currently accepted value for nearly ideal gases. Aside from their intrinsic interest, our analyses can provide students intriguing applications of the gas laws and Pascal's law and motivate them to consider Pascal's paradox. We also note the influence of ballooning and of the French Revolution on Gay-Lussac.

Analysis of Prostate Patient Setup and Tracking Data: Potential Intervention Strategies

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

Su Zhong, E-mail: zsu@floridaproton.org; Zhang Lisha; Murphy, Martin

Purpose: To evaluate the setup, interfraction, and intrafraction organ motion error distributions and simulate intrafraction intervention strategies for prostate radiotherapy. Methods and Materials: A total of 17 patients underwent treatment setup and were monitored using the Calypso system during radiotherapy. On average, the prostate tracking measurements were performed for 8 min/fraction for 28 fractions for each patient. For both patient couch shift data and intrafraction organ motion data, the systematic and random errors were obtained from the patient population. The planning target volume margins were calculated using the van Herk formula. Two intervention strategies were simulated using the tracking data:more » the deviation threshold and period. The related planning target volume margins, time costs, and prostate position 'fluctuation' were presented. Results: The required treatment margin for the left-right, superoinferior, and anteroposterior axes was 8.4, 10.8, and 14.7 mm for skin mark-only setup and 1.3, 2.3, and 2.8 mm using the on-line setup correction, respectively. Prostate motion significantly correlated among the superoinferior and anteroposterior directions. Of the 17 patients, 14 had prostate motion within 5 mm of the initial setup position for {>=}91.6% of the total tracking time. The treatment margin decreased to 1.1, 1.8, and 2.3 mm with a 3-mm threshold correction and to 0.5, 1.0, and 1.5 mm with an every-2-min correction in the left-right, superoinferior, and anteroposterior directions, respectively. The periodic corrections significantly increase the treatment time and increased the number of instances when the setup correction was made during transient excursions. Conclusions: The residual systematic and random error due to intrafraction prostate motion is small after on-line setup correction. Threshold-based and time-based intervention strategies both reduced the planning target volume margins. The time-based strategies increased the treatment time and the in-fraction position fluctuation.« less

Ion recombination and polarity correction factors for a plane-parallel ionization chamber in a proton scanning beam.

PubMed

Liszka, Małgorzata; Stolarczyk, Liliana; Kłodowska, Magdalena; Kozera, Anna; Krzempek, Dawid; Mojżeszek, Natalia; Pędracka, Anna; Waligórski, Michael Patrick Russell; Olko, Paweł

2018-01-01

To evaluate the effect on charge collection in the ionization chamber (IC) in proton pencil beam scanning (PBS), where the local dose rate may exceed the dose rates encountered in conventional MV therapy by up to three orders of magnitude. We measured values of the ion recombination (k s ) and polarity (k pol ) correction factors in water, for a plane-parallel Markus TM23343 IC, using the cyclotron-based Proteus-235 therapy system with an active proton PBS of energies 30-230 MeV. Values of k s were determined from extrapolation of the saturation curve and the Two-Voltage Method (TVM), for planar fields. We compared our experimental results with those obtained from theoretical calculations. The PBS dose rates were estimated by combining direct IC measurements with results of simulations performed using the FLUKA MC code. Values of k s were also determined by the TVM for uniformly irradiated volumes over different ranges and modulation depths of the proton PBS, with or without range shifter. By measuring charge collection efficiency versus applied IC voltage, we confirmed that, with respect to ion recombination, our proton PBS represents a continuous beam. For a given chamber parameter, e.g., nominal voltage, the value of k s depends on the energy and the dose rate of the proton PBS, reaching c. 0.5% for the TVM, at the dose rate of 13.4 Gy/s. For uniformly irradiated regular volumes, the k s value was significantly smaller, within 0.2% or 0.3% for irradiations with or without range shifter, respectively. Within measurement uncertainty, the average value of k pol , for the Markus TM23343 IC, was close to unity over the whole investigated range of clinical proton beam energies. While no polarity effect was observed for the Markus TM23343 IC in our pencil scanning proton beam system, the effect of volume recombination cannot be ignored. © 2017 American Association of Physicists in Medicine.

A Randomized Clinical Trial of Comparing Monophasic Monodensified and Biphasic Nonanimal Stabilized Hyaluronic Acid Dermal Fillers in Treatment of Asian Nasolabial Folds.

PubMed

Zhou, Shuang-Bai; Xie, Yun; Chiang, Cheng-An; Liu, Kai; Li, Qing-Feng

2016-09-01

Cross-linked hyaluronic acids (HAs) with varying characteristics and formulations are available. Despite the popularity of HA, limited studies compared the effectiveness of monophasic monodensified hyaluronic acid (MMHA) and biphasic nonanimal stabilized hyaluronic acid (BHA) products in correcting nasolabial folds (NLFs) in the Asian population. This double-blinded, randomized research aimed at evaluating the outcomes of MMHA and BHA products in treating Asian NLFs. Subjects aged between 18 and 65 years with moderate-to-severe NLFs were randomized to receive MMHA or BHA treatment. A touch-up treatment with the same product was performed at the 4-week follow-up, if needed. The effectiveness was evaluated for 24 weeks by masked investigators. All adverse events were recorded for safety evaluation. Twenty-five subjects in the MMHA Group and twenty-four subjects in the BHA Group finished 24-week follow-up. Results showed that subjects from both groups obtained satisfactory outcome in NLF correction. A lower amount of MMHA was required to achieve a similar result as that of BHA (p < .01). Both HA products maintained the effectiveness at the end of the 24-week follow-up. Both MMHA and BHA are effective for correcting NLF in Asian patients, producing satisfactory results. Monophasic monodensified hyaluronic acid provides similar satisfaction to BHA while requiring less injection volume.

Propulsion of a fin whale (Balaenoptera physalus): why the fin whale is a fast swimmer.

PubMed

Bose, N; Lien, J

1989-07-22

Measurements of an immature fin whale (Balaenoptera physalus), which died as a result of entrapment in fishing gear near Frenchmans Cove, Newfoundland (47 degrees 9' N, 55 degrees 25' W), were made to obtain estimates of volume and surface area of the animal. Detailed measurements of the flukes, both planform and sections, were also obtained. A strip theory was developed to calculate the hydrodynamic performance of the whale's flukes as an oscillating propeller. This method is based on linear, two-dimensional, small-amplitude, unsteady hydrofoil theory with correction factors used to account for the effects of finite span and finite amplitude motion. These correction factors were developed from theoretical results of large-amplitude heaving motion and unsteady lifting-surface theory. A model that makes an estimate of the effects of viscous flow on propeller performance was superimposed on the potential-flow results. This model estimates the drag of the hydrofoil sections by assuming that the drag is similar to that of a hydrofoil section in steady flow. The performance characteristics of the flukes of the fin whale were estimated by using this method. The effects of the different correction factors, and of the frictional drag of the fluke sections, are emphasized. Frictional effects in particular were found to reduce the hydrodynamic efficiency of the flukes significantly. The results are discussed and compared with the known characteristics of fin-whale swimming.

Impacts of future climate change on urban flood volumes in Hohhot in northern China: benefits of climate change mitigation and adaptations

NASA Astrophysics Data System (ADS)

Zhou, Qianqian; Leng, Guoyong; Huang, Maoyi

2018-01-01

As China becomes increasingly urbanised, flooding has become a regular occurrence in its major cities. Assessing the effects of future climate change on urban flood volumes is crucial to informing better management of such disasters given the severity of the devastating impacts of flooding (e.g. the 2016 flooding events across China). Although recent studies have investigated the impacts of future climate change on urban flooding, the effects of both climate change mitigation and adaptation have rarely been accounted for together in a consistent framework. In this study, we assess the benefits of mitigating climate change by reducing greenhouse gas (GHG) emissions and locally adapting to climate change by modifying drainage systems to reduce urban flooding under various climate change scenarios through a case study conducted in northern China. The urban drainage model - Storm Water Management Model - was used to simulate urban flood volumes using current and two adapted drainage systems (i.e. pipe enlargement and low-impact development, LID), driven by bias-corrected meteorological forcing from five general circulation models in the Coupled Model Intercomparison Project Phase 5 archive. Results indicate that urban flood volume is projected to increase by 52 % over 2020-2040 compared to the volume in 1971-2000 under the business-as-usual scenario (i.e. Representative Concentration Pathway (RCP) 8.5). The magnitudes of urban flood volumes are found to increase nonlinearly with changes in precipitation intensity. On average, the projected flood volume under RCP 2.6 is 13 % less than that under RCP 8.5, demonstrating the benefits of global-scale climate change mitigation efforts in reducing local urban flood volumes. Comparison of reduced flood volumes between climate change mitigation and local adaptation (by improving drainage systems) scenarios suggests that local adaptation is more effective than climate change mitigation in reducing future flood volumes. This has broad implications for the research community relative to drainage system design and modelling in a changing environment. This study highlights the importance of accounting for local adaptation when coping with future urban floods.

Impacts of future climate change on urban flood volumes in Hohhot in northern China: benefits of climate change mitigation and adaptations

DOE PAGES

Zhou, Qianqian; Leng, Guoyong; Huang, Maoyi

2018-01-15

As China becomes increasingly urbanised, flooding has become a regular occurrence in its major cities. Assessing the effects of future climate change on urban flood volumes is crucial to informing better management of such disasters given the severity of the devastating impacts of flooding (e.g. the 2016 flooding events across China). Although recent studies have investigated the impacts of future climate change on urban flooding, the effects of both climate change mitigation and adaptation have rarely been accounted for together in a consistent framework. In this study, we assess the benefits of mitigating climate change by reducing greenhouse gas (GHG)more » emissions and locally adapting to climate change by modifying drainage systems to reduce urban flooding under various climate change scenarios through a case study conducted in northern China. The urban drainage model – Storm Water Management Model – was used to simulate urban flood volumes using current and two adapted drainage systems (i.e. pipe enlargement and low-impact development, LID), driven by bias-corrected meteorological forcing from five general circulation models in the Coupled Model Intercomparison Project Phase 5 archive. Results indicate that urban flood volume is projected to increase by 52 % over 2020–2040 compared to the volume in 1971–2000 under the business-as-usual scenario (i.e. Representative Concentration Pathway (RCP) 8.5). The magnitudes of urban flood volumes are found to increase nonlinearly with changes in precipitation intensity. On average, the projected flood volume under RCP 2.6 is 13 % less than that under RCP 8.5, demonstrating the benefits of global-scale climate change mitigation efforts in reducing local urban flood volumes. Comparison of reduced flood volumes between climate change mitigation and local adaptation (by improving drainage systems) scenarios suggests that local adaptation is more effective than climate change mitigation in reducing future flood volumes. This has broad implications for the research community relative to drainage system design and modelling in a changing environment. Furthermore, this study highlights the importance of accounting for local adaptation when coping with future urban floods.« less

Impacts of future climate change on urban flood volumes in Hohhot in northern China: benefits of climate change mitigation and adaptations

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

Zhou, Qianqian; Leng, Guoyong; Huang, Maoyi

As China becomes increasingly urbanised, flooding has become a regular occurrence in its major cities. Assessing the effects of future climate change on urban flood volumes is crucial to informing better management of such disasters given the severity of the devastating impacts of flooding (e.g. the 2016 flooding events across China). Although recent studies have investigated the impacts of future climate change on urban flooding, the effects of both climate change mitigation and adaptation have rarely been accounted for together in a consistent framework. In this study, we assess the benefits of mitigating climate change by reducing greenhouse gas (GHG)more » emissions and locally adapting to climate change by modifying drainage systems to reduce urban flooding under various climate change scenarios through a case study conducted in northern China. The urban drainage model – Storm Water Management Model – was used to simulate urban flood volumes using current and two adapted drainage systems (i.e. pipe enlargement and low-impact development, LID), driven by bias-corrected meteorological forcing from five general circulation models in the Coupled Model Intercomparison Project Phase 5 archive. Results indicate that urban flood volume is projected to increase by 52 % over 2020–2040 compared to the volume in 1971–2000 under the business-as-usual scenario (i.e. Representative Concentration Pathway (RCP) 8.5). The magnitudes of urban flood volumes are found to increase nonlinearly with changes in precipitation intensity. On average, the projected flood volume under RCP 2.6 is 13 % less than that under RCP 8.5, demonstrating the benefits of global-scale climate change mitigation efforts in reducing local urban flood volumes. Comparison of reduced flood volumes between climate change mitigation and local adaptation (by improving drainage systems) scenarios suggests that local adaptation is more effective than climate change mitigation in reducing future flood volumes. This has broad implications for the research community relative to drainage system design and modelling in a changing environment. Furthermore, this study highlights the importance of accounting for local adaptation when coping with future urban floods.« less

Assessment of estimated retinal atrophy progression in Stargardt macular dystrophy using spectral-domain optical coherence tomography

PubMed Central

Strauss, Rupert W; Muñoz, Beatriz; Wolfson, Yulia; Sophie, Raafay; Fletcher, Emily; Bittencourt, Millena G; Scholl, Hendrik P N

2016-01-01

Aims To estimate disease progression based on analysis of macular volume measured by spectral-domain optical coherence tomography (SD-OCT) in patients affected by Stargardt macular dystrophy (STGD1) and to evaluate the influence of software errors on these measurements. Methods 58 eyes of 29 STGD1 patients were included. Numbers and types of algorithm errors were recorded and manually corrected. In a subgroup of 36 eyes of 18 patients with at least two examinations over time, total macular volume (TMV) and volumes of all nine Early Treatment of Diabetic Retinopathy Study (ETDRS) subfields were obtained. Random effects models were used to estimate the rate of change per year for the population, and empirical Bayes slopes were used to estimate yearly decline in TMV for individual eyes. Results 6958 single B-scans from 190 macular cube scans were analysed. 2360 (33.9%) showed algorithm errors. Mean observation period for follow-up data was 15 months (range 3–40). The median (IQR) change in TMV using the empirical Bayes estimates for the individual eyes was −0.103 (−0.145, −0.059) mm3 per year. The mean (±SD) TMV was 6.321±1.000 mm3 at baseline, and rate of decline was −0.118 mm3 per year (p=0.003). Yearly mean volume change was −0.004 mm3 in the central subfield (mean baseline=0.128 mm3), −0.032 mm3 in the inner (mean baseline=1.484 mm3) and −0.079 mm3 in the outer ETDRS subfields (mean baseline=5.206 mm3). Conclusions SD-OCT measurements allow monitoring the decline in retinal volume in STGD1; however, they require significant manual correction of software errors. PMID:26568636

Association of GSK3beta polymorphisms with brain structural changes in major depressive disorder.

PubMed

Inkster, Becky; Nichols, Thomas E; Saemann, Philipp G; Auer, Dorothee P; Holsboer, Florian; Muglia, Pierandrea; Matthews, Paul M

2009-07-01

Indirect evidence suggests that the glycogen synthase kinase-3beta (GSK3beta) gene might be implicated in major depressive disorder (MDD). We evaluated 15 GSK3beta single-nucleotide polymorphisms (SNPs) to test for associations with regional gray matter (GM) volume differences in patients with recurrent MDD. We then used the defined regions of interest based on significant associations to test for MDD x genotype interactions by including a matched control group without any psychiatric disorder, including MDD. General linear model with nonstationary cluster-based inference. Munich, Germany. Patients with recurrent MDD (n = 134) and age-, sex-, and ethnicity-matched healthy controls (n = 143). Associations between GSK3beta polymorphisms and regional GM volume differences. Variation in GM volume was associated with GSK3beta polymorphisms; the most significant associations were found for rs6438552, a putative functional intronic SNP that showed 3 significant GM clusters in the right and left superior temporal gyri and the right hippocampus (P < .001, P = .02, and P = .02, respectively, corrected for multiple comparisons across the whole brain). Similar results were obtained with rs12630592, an SNP in high linkage disequilibrium. A significant SNP x MDD status interaction was observed for the effect on GM volumes in the right hippocampus and superior temporal gyri (P < .001 and P = .01, corrected, respectively). The GSK3beta gene may have a role in determining regional GM volume differences of the right hippocampus and bilateral superior temporal gyri. The association between genotype and brain structure was specific to the patients with MDD, suggesting that GSK3beta genotypes might interact with MDD status. We speculate that this is a consequence of regional neocortical, glial, or neuronal growth or survival. In considering core cognitive features of MDD, the association of GSK3beta polymorphisms with structural variation in the temporal lobe and hippocampus is of particular interest in the context of other evidence for structural and functional abnormalities in the hippocampi of patients with MDD.

Measurement of gastric meal and secretion volumes using magnetic resonance imaging

PubMed Central

Hoad, C.L.; Parker, H.; Hudders, N.; Costigan, C.; Cox, E.F.; Perkins, A.C.; Blackshaw, P.E.; Marciani, L.; Spiller, R.C.; Fox, M.R.; Gowland, P.A.

2015-01-01

MRI can assess multiple gastric functions without ionizing radiation. However, time consuming image acquisition and analysis of gastric volume data, plus confounding of gastric emptying measurements by gastric secretions mixed with the test meal have limited its use to research centres. This study presents an MRI acquisition protocol and analysis algorithm suitable for the clinical measurement of gastric volume and secretion volume. Reproducibility of gastric volume measurements was assessed using data from 10 healthy volunteers following a liquid test meal with rapid MRI acquisition within one breath-hold and semi-automated analysis. Dilution of the ingested meal with gastric secretion was estimated using a respiratory-triggered T1 mapping protocol. Accuracy of the secretion volume measurements was assessed using data from 24 healthy volunteers following a mixed (liquid/solid) test meal with MRI meal volumes compared to data acquired using gamma scintigraphy (GS) on the same subjects studied on a separate study day. The mean (SD) coefficient of variance between 3 observers for both total gastric contents (including meal, secretions and air) and just the gastric contents (meal and secretion only) was 3 (2) % at large gastric volumes (> 200 ml). Mean (SD) secretion volumes post meal ingestion were 64 (51) ml and 110 (40) ml at 15 and 75 minutes respectively. Comparison with GS meal volumes, showed that MRI meal only volume (after correction for secretion volume) were similar to GS, with a linear regression gradient (std err) of 1.06 (0.10) and intercept −11 (24) ml. In conclusion, (i) rapid acquisition removed the requirement to image during prolonged breath-hold (ii) semi-automatic analysis greatly reduced time required to derive measurements and (iii) correction for secretion volumes provides accurate assessment of gastric meal volumes and emptying. Together these features provide the scientific basis of a protocol which would be suitable in clinical practice. PMID:25592405

A three-dimensional model-based partial volume correction strategy for gated cardiac mouse PET imaging

NASA Astrophysics Data System (ADS)

Dumouchel, Tyler; Thorn, Stephanie; Kordos, Myra; DaSilva, Jean; Beanlands, Rob S. B.; deKemp, Robert A.

2012-07-01

Quantification in cardiac mouse positron emission tomography (PET) imaging is limited by the imaging spatial resolution. Spillover of left ventricle (LV) myocardial activity into adjacent organs results in partial volume (PV) losses leading to underestimation of myocardial activity. A PV correction method was developed to restore accuracy of the activity distribution for FDG mouse imaging. The PV correction model was based on convolving an LV image estimate with a 3D point spread function. The LV model was described regionally by a five-parameter profile including myocardial, background and blood activities which were separated into three compartments by the endocardial radius and myocardium wall thickness. The PV correction was tested with digital simulations and a physical 3D mouse LV phantom. In vivo cardiac FDG mouse PET imaging was also performed. Following imaging, the mice were sacrificed and the tracer biodistribution in the LV and liver tissue was measured using a gamma-counter. The PV correction algorithm improved recovery from 50% to within 5% of the truth for the simulated and measured phantom data and image uniformity by 5-13%. The PV correction algorithm improved the mean myocardial LV recovery from 0.56 (0.54) to 1.13 (1.10) without (with) scatter and attenuation corrections. The mean image uniformity was improved from 26% (26%) to 17% (16%) without (with) scatter and attenuation corrections applied. Scatter and attenuation corrections were not observed to significantly impact PV-corrected myocardial recovery or image uniformity. Image-based PV correction algorithm can increase the accuracy of PET image activity and improve the uniformity of the activity distribution in normal mice. The algorithm may be applied using different tracers, in transgenic models that affect myocardial uptake, or in different species provided there is sufficient image quality and similar contrast between the myocardium and surrounding structures.

Nonergodicity of microfine binary systems

NASA Astrophysics Data System (ADS)

Son, L. D.; Sidorov, V. E.; Popel', P. S.; Shul'gin, D. B.

2016-02-01

The correction to the equation of state that is related to the nonergodicity of diffusion dynamics is discussed for a binary solid solution with a limited solubility. It is asserted that, apart from standard thermodynamic variables (temperature, volume, concentration), this correction should be taken into account in the form of the average local chemical potential fluctuations associated with microheterogeneity in order to plot a phase diagram. It is shown that a low value of this correction lowers the miscibility gap and that this gap splits when this correction increases. This situation is discussed for eutectic systems and Ga-Pb, Fe-Cu, and Cu-Zr alloys.

Monte Carlo modeling of the MammoSite(Reg) treatments: Dose effects of air pockets

NASA Astrophysics Data System (ADS)

Huang, Yu-Huei Jessica

In the treatment of early-stage breast cancer, MammoSiteRTM has been used as one of the partial breast irradiation techniques after breast-conserving surgery. The MammoSiteRTM applicator is a single catheter with an inflatable balloon at its distal end that can be placed in the resected cavity (tumor bed). The treatment is performed by delivering the Ir-192 high-dose-rate source through the center lumen of the catheter by a remote afterloader while the balloon is inflated in the tumor bed cavity. In the MammoSiteRTM treatment, it has been found that air pockets occasionally exist and can be seen and measured in CT images. Experiences have shown that about 90% of the patients have air pockets when imaged two days after the balloon placement. The criterion for the air pocket volume is less than or equal to 10% of the planning target volume in volume. The purpose of this study is to quantify dose errors occurring at the interface of the air pocket in MammoSiteRTM treatments with Monte Carlo calculations, so that the dosimetric effects from the air pocket can be fully understood. Modern brachytherapy treatment planning systems typically consider patient anatomy as a homogeneous water medium, and incorrectly model lateral and backscatter radiation during treatment delivery. Heterogeneities complicate the problem and may result in overdosage to the tissue located near the medium interface. This becomes a problem in MammoSiteRTM brachytherapy when air pocket appears during the treatment. The resulting percentage dose difference near the air-tissue interface is hypothesized to be greater than 10% when comparing Monte Carlo N-Particle (version 5) with current treatment planning systems. The specific aims for this study are: (1) Validate Monte Carlo N-Particle (Version 5) source modeling. (2) Develop phantom. (3) Calculate phantom doses with Monte Carlo N-Particle (Version 5) and investigate doses difference between thermoluminescent dosimeter measurement, treatment planning system, and Monte Carlo results. (4) Calculate dose differences for various treatment parameters. The results from thermoliminescent dosimeter phantom measurements proves that with correct geometric and source models, Monte Carlo method can be used to estimate homogeneity and heterogeneity doses in MammoSiteRTM treatment. The resulting dose differences at various points of interests in Monte Carlo calculations were presented and compared between different calculation methods. The air pocket doses were found to be underestimated by the treatment planning system. It was concluded that after correcting for inverse square law, the underestimation error from the treatment planning system will be less than +/- 2.0%, and +/- 3.5%, at the air pocket surface and air pocket planning target volume, respectively, when comparing Monte Carlo N-Particle (version 5) results. If the skin surface is located close to the air pocket, the underestimation effect at the air pocket surface and air pocket planning target volume doses becomes less because the air outside of the skin surface reduces the air pocket inhomogeneity effect. In order to maintain appropriate skin dose within tolerance, the skin surface criterion should be considered as the smallest thickness of the breast tissue located between the air pocket and the skin surface. The thickness should be at least 5 mm. In conclusion, the air pocket outside the balloon had less than 10% inhomogeneity effect based on the situations studied. It is recommended that at least an inverse square correction should be taken into consideration in order to relate clinical outcomes to actual delivered doses to the air pocket and surrounding tissues.

Apolipoprotein ε4 is associated with lower brain volume in cognitively normal Chinese but not white older adults.

PubMed

Yokoyama, Jennifer S; Lee, Allen K L; Takada, Leonel T; Busovaca, Edgar; Bonham, Luke W; Chao, Steven Z; Tse, Marian; He, Jing; Schwarz, Christopher G; Carmichael, Owen T; Matthews, Brandy R; Karydas, Anna; Weiner, Michael W; Coppola, Giovanni; DeCarli, Charles S; Miller, Bruce L; Rosen, Howard J

2015-01-01

Studying ethnically diverse groups is important for furthering our understanding of biological mechanisms of disease that may vary across human populations. The ε4 allele of apolipoprotein E (APOE ε4) is a well-established risk factor for Alzheimer's disease (AD), and may confer anatomic and functional effects years before clinical signs of cognitive decline are observed. The allele frequency of APOE ε4 varies both across and within populations, and the size of the effect it confers for dementia risk may be affected by other factors. Our objective was to investigate the role APOE ε4 plays in moderating brain volume in cognitively normal Chinese older adults, compared to older white Americans. We hypothesized that carrying APOE ε4 would be associated with reduced brain volume and that the magnitude of this effect would be different between ethnic groups. We performed whole brain analysis of structural MRIs from Chinese living in America (n = 41) and Shanghai (n = 30) and compared them to white Americans (n = 71). We found a significant interaction effect of carrying APOE ε4 and being Chinese. The APOE ε4xChinese interaction was associated with lower volume in bilateral cuneus and left middle frontal gyrus (Puncorrected<0.001), with suggestive findings in right entorhinal cortex and left hippocampus (Puncorrected<0.01), all regions that are associated with neurodegeneration in AD. After correction for multiple testing, the left cuneus remained significantly associated with the interaction effect (PFWE = 0.05). Our study suggests there is a differential effect of APOE ε4 on brain volume in Chinese versus white cognitively normal elderly adults. This represents a novel finding that, if verified in larger studies, has implications for how biological, environmental and/or lifestyle factors may modify APOE ε4 effects on the brain in diverse populations.

Influence of Co-57 and CT Transmission Measurements on the Quantification Accuracy and Partial Volume Effect of a Small Animal PET Scanner.

PubMed

Mannheim, Julia G; Schmid, Andreas M; Pichler, Bernd J

2017-12-01

Non-invasive in vivo positron emission tomography (PET) provides high detection sensitivity in the nano- to picomolar range and in addition to other advantages, the possibility to absolutely quantify the acquired data. The present study focuses on the comparison of transmission data acquired with an X-ray computed tomography (CT) scanner or a Co-57 source for the Inveon small animal PET scanner (Siemens Healthcare, Knoxville, TN, USA), as well as determines their influences on the quantification accuracy and partial volume effect (PVE). A special focus included the impact of the performed calibration on the quantification accuracy. Phantom measurements were carried out to determine the quantification accuracy, the influence of the object size on the quantification, and the PVE for different sphere sizes, along the field of view and for different contrast ratios. An influence of the emission activity on the Co-57 transmission measurements was discovered (deviations up to 24.06 % measured to true activity), whereas no influence of the emission activity on the CT attenuation correction was identified (deviations <3 % for measured to true activity). The quantification accuracy was substantially influenced by the applied calibration factor and by the object size. The PVE demonstrated a dependency on the sphere size, the position within the field of view, the reconstruction and correction algorithms and the count statistics. Depending on the reconstruction algorithm, only ∼30-40 % of the true activity within a small sphere could be resolved. The iterative 3D reconstruction algorithms uncovered substantially increased recovery values compared to the analytical and 2D iterative reconstruction algorithms (up to 70.46 % and 80.82 % recovery for the smallest and largest sphere using iterative 3D reconstruction algorithms). The transmission measurement (CT or Co-57 source) to correct for attenuation did not severely influence the PVE. The analysis of the quantification accuracy and the PVE revealed an influence of the object size, the reconstruction algorithm and the applied corrections. Particularly, the influence of the emission activity during the transmission measurement performed with a Co-57 source must be considered. To receive comparable results, also among different scanner configurations, standardization of the acquisition (imaging parameters, as well as applied reconstruction and correction protocols) is necessary.

Polarity effects and apparent ion recombination in microionization chambers

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

Miller, Jessica R., E-mail: miller@humonc.wisc.edu; Hooten, Brian D.; Micka, John A.

Purpose: Microchambers demonstrate anomalous voltage-dependent polarity effects. Existing polarity and ion recombination correction factors do not account for these effects. As a result, many commercial microchamber models do not meet the specification of a reference-class ionization chamber as defined by the American Association of Physicists in Medicine. The purpose of this investigation is to determine the cause of these voltage-dependent polarity effects. Methods: A series of microchamber prototypes were produced to isolate the source of the voltage-dependent polarity effects. Parameters including ionization-chamber collecting-volume size, stem and cable irradiation, chamber assembly, contaminants, high-Z materials, and individual chamber components were investigated. Measurementsmore » were performed with electrodes coated with graphite to isolate electrode conductivity. Chamber response was measured as the potential bias of the guard electrode was altered with respect to the collecting electrode, through the integration of additional power supplies. Ionization chamber models were also simulated using COMSOL Multiphysics software to investigate the effect of a potential difference between electrodes on electric field lines and collecting volume definition. Results: Investigations with microchamber prototypes demonstrated that the significant source of the voltage-dependent polarity effects was a potential difference between the guard and collecting electrodes of the chambers. The voltage-dependent polarity effects for each prototype were primarily isolated to either the guard or collecting electrode. Polarity effects were reduced by coating the isolated electrode with a conductive layer of graphite. Polarity effects were increased by introducing a potential difference between the electrodes. COMSOL simulations further demonstrated that for a given potential difference between electrodes, the collecting volume of the chamber changed as the applied voltage was altered, producing voltage-dependent polarity effects in the chamber response. Ionization chamber measurements and COMSOL simulations demonstrated an inverse relationship between the chamber collecting volume size and the severity of voltage-dependent polarity effects on chamber response. The effect of a given potential difference on chamber polarity effects was roughly ten times greater for microchambers as compared to Farmer-type chambers. Stem and cable irradiations, chamber assembly, contaminants, and high-Z materials were not found to be a significant source of the voltage-dependent polarity effects. Conclusions: A potential difference between the guard and collecting electrodes was found to be the primary source of the voltage-dependent polarity effects demonstrated by microchambers. For a given potential difference between electrodes, the relative change in the collecting volume is smaller for larger-volume chambers, illustrating why these polarity effects are not seen in larger-volume chambers with similar guard and collecting electrode designs. Thus, for small-volume chambers, it is necessary to reduce the potential difference between the guard and collecting electrodes in order to reduce polarity effects for reference dosimetry measurements.« less

Impact of the column hardware volume on resolution in very high pressure liquid chromatography non-invasive investigations.

PubMed

Gritti, Fabrice; McDonald, Thomas; Gilar, Martin

2015-11-13

The impact of the column hardware volume (≃ 1.7 μL) on the optimum reduced plate heights of a series of short 2.1 mm × 50 mm columns (hold-up volume ≃ 80-90 μL) packed with 1.8 μm HSS-T3, 1.7 μm BEH-C18, 1.7 μm CSH-C18, 1.6 μm CORTECS-C18+, and 1.7 μm BEH-C4 particles was investigated. A rapid and non-invasive method based on the reduction of the system dispersion (to only 0.15 μL(2)) of an I-class Acquity system and on the corrected plate heights (for system dispersion) of five weakly retained n-alkanophenones in RPLC was proposed. Evidence for sample dispersion through the column hardware volume was also revealed from the experimental plot of the peak capacities for smooth linear gradients versus the corrected efficiency of a weakly retained alkanophenone (isocratic runs). The plot is built for a constant gradient steepness irrespective of the applied flow rates (0.01-0.30 mL/min) and column lengths (2, 3, 5, and 10 cm). The volume variance caused by column endfittings and frits was estimated in between 0.1 and 0.7 μL(2) depending on the applied flow rate. After correction for system and hardware dispersion, the minimum reduced plate heights of short (5 cm) and narrow-bore (2.1mm i.d.) beds packed with sub-2 μm fully and superficially porous particles were found close to 1.5 and 0.7, respectively, instead of the classical h values of 2.0 and 1.4 for the whole column assembly. Copyright © 2015 Elsevier B.V. All rights reserved.

Use of an acoustic helium analyzer for measuring lung volumes.

PubMed

Krumpe, P E; MacDannald, H J; Finley, T N; Schear, H E; Hall, J; Cribbs, D

1981-01-01

We have evaluated the use of an acoustic gas analyzer (AGA) for the measurement of total lung capacity (TLC) by single-breath helium dilution. The AGA has a rapid response time (0-90% response = 160 ms for 10% He), is linear for helium concentration of 0.1-10%, is stable over a wide range of ambient temperatures, and is small and portable. We plotted the output of the AGA vs. expired lung volume after a vital capacity breath of 10% He. However, since the AGA is sensitive to changes in speed of sound relative to air, the AGA output signal also reports an artifact due to alveolar gases. We corrected for this artifact by replotting a single-breath expiration after a vital capacity breath of room air. Mean alveolar helium concentration (HeA) was then measured by planimetry, using this alveolar gas curve as the base line. TLC was calculated using the HeA from the corrected AGA output and compared with TLC calculated from HeA simultaneously measured using a mass spectrometer (MS). In 12 normal subjects and 9 patients with chronic obstructive pulmonary disease (COPD) TLC-AGA and TLC-MS were compared by linear regression analysis; correlation coefficient (r) was 0.973 for normals and 0.968 for COPD patients (P less than 0.001). This single-breath; estimation of TLC using the corrected signal of the AGA vs. Expired volume seems ideally suited for the measurement of subdivisions of lung volume in field studies.

40 CFR 80.1622 - Approval for small refiner and small volume refinery status.

Code of Federal Regulations, 2014 CFR

2014-07-01

... appropriate data to correct the record when the company submits its application. (ii) Foreign small refiners... 40 Protection of Environment 17 2014-07-01 2014-07-01 false Approval for small refiner and small... Approval for small refiner and small volume refinery status. (a) Applications for small refiner or small...

LANDSAT-D program. Volume 2: Ground segment

NASA Technical Reports Server (NTRS)

1984-01-01

Raw digital data, as received from the LANDSAT spacecraft, cannot generate images that meet specifications. Radiometric corrections must be made to compensate for aging and for differences in sensitivity among the instrument sensors. Geometric corrections must be made to compensate for off-nadir look angle, and to calculate spacecraft drift from its prescribed path. Corrections must also be made for look-angle jitter caused by vibrations induced by spacecraft equipment. The major components of the LANDSAT ground segment and their functions are discussed.

Satellite radar altimetry over ice. Volume 1: Processing and corrections of Seasat data over Greenland

NASA Technical Reports Server (NTRS)

Zwally, H. Jay; Brenner, Anita C.; Major, Judith A.; Martin, Thomas V.; Bindschadler, Robert A.

1990-01-01

The data-processing methods and ice data products derived from Seasat radar altimeter measurements over the Greenland ice sheet and surrounding sea ice are documented. The corrections derived and applied to the Seasat radar altimeter data over ice are described in detail, including the editing and retracking algorithm to correct for height errors caused by lags in the automatic range tracking circuit. The methods for radial adjustment of the orbits and estimation of the slope-induced errors are given.

Accuracy and variability of tumor burden measurement on multi-parametric MRI

NASA Astrophysics Data System (ADS)

Salarian, Mehrnoush; Gibson, Eli; Shahedi, Maysam; Gaed, Mena; Gómez, José A.; Moussa, Madeleine; Romagnoli, Cesare; Cool, Derek W.; Bastian-Jordan, Matthew; Chin, Joseph L.; Pautler, Stephen; Bauman, Glenn S.; Ward, Aaron D.

2014-03-01

Measurement of prostate tumour volume can inform prognosis and treatment selection, including an assessment of the suitability and feasibility of focal therapy, which can potentially spare patients the deleterious side effects of radical treatment. Prostate biopsy is the clinical standard for diagnosis but provides limited information regarding tumour volume due to sparse tissue sampling. A non-invasive means for accurate determination of tumour burden could be of clinical value and an important step toward reduction of overtreatment. Multi-parametric magnetic resonance imaging (MPMRI) is showing promise for prostate cancer diagnosis. However, the accuracy and inter-observer variability of prostate tumour volume estimation based on separate expert contouring of T2-weighted (T2W), dynamic contrastenhanced (DCE), and diffusion-weighted (DW) MRI sequences acquired using an endorectal coil at 3T is currently unknown. We investigated this question using a histologic reference standard based on a highly accurate MPMRIhistology image registration and a smooth interpolation of planimetric tumour measurements on histology. Our results showed that prostate tumour volumes estimated based on MPMRI consistently overestimated histological reference tumour volumes. The variability of tumour volume estimates across the different pulse sequences exceeded interobserver variability within any sequence. Tumour volume estimates on DCE MRI provided the lowest inter-observer variability and the highest correlation with histology tumour volumes, whereas the apparent diffusion coefficient (ADC) maps provided the lowest volume estimation error. If validated on a larger data set, the observed correlations could support the development of automated prostate tumour volume segmentation algorithms as well as correction schemes for tumour burden estimation on MPMRI.

Scale Estimation and Correction of the Monocular Simultaneous Localization and Mapping (SLAM) Based on Fusion of 1D Laser Range Finder and Vision Data.

PubMed

Zhang, Zhuang; Zhao, Rujin; Liu, Enhai; Yan, Kun; Ma, Yuebo

2018-06-15

This article presents a new sensor fusion method for visual simultaneous localization and mapping (SLAM) through integration of a monocular camera and a 1D-laser range finder. Such as a fusion method provides the scale estimation and drift correction and it is not limited by volume, e.g., the stereo camera is constrained by the baseline and overcomes the limited depth range problem associated with SLAM for RGBD cameras. We first present the analytical feasibility for estimating the absolute scale through the fusion of 1D distance information and image information. Next, the analytical derivation of the laser-vision fusion is described in detail based on the local dense reconstruction of the image sequences. We also correct the scale drift of the monocular SLAM using the laser distance information which is independent of the drift error. Finally, application of this approach to both indoor and outdoor scenes is verified by the Technical University of Munich dataset of RGBD and self-collected data. We compare the effects of the scale estimation and drift correction of the proposed method with the SLAM for a monocular camera and a RGBD camera.

Application of London-type dispersion corrections to the solid-state density functional theory simulation of the terahertz spectra of crystalline pharmaceuticals.

PubMed

King, Matthew D; Buchanan, William D; Korter, Timothy M

2011-03-14

The effects of applying an empirical dispersion correction to solid-state density functional theory methods were evaluated in the simulation of the crystal structure and low-frequency (10 to 90 cm(-1)) terahertz spectrum of the non-steroidal anti-inflammatory drug, naproxen. The naproxen molecular crystal is bound largely by weak London force interactions, as well as by more prominent interactions such as hydrogen bonding, and thus serves as a good model for the assessment of the pair-wise dispersion correction term in systems influenced by intermolecular interactions of various strengths. Modifications to the dispersion parameters were tested in both fully optimized unit cell dimensions and those determined by X-ray crystallography, with subsequent simulations of the THz spectrum being performed. Use of the unmodified PBE density functional leads to an unrealistic expansion of the unit cell volume and the poor representation of the THz spectrum. Inclusion of a modified dispersion correction enabled a high-quality simulation of the THz spectrum and crystal structure of naproxen to be achieved without the need for artificially constraining the unit cell dimensions.

Rotorcraft Flight Simulation Computer Program C81 with DATAMAP interface. Volume I. User’s Manual

DTIC Science & Technology

1981-10-01

any one of the RWAS tables to simulate the defined effect of that input, care must be exercised to assure that the table used is based on the correct... IMPROVED MANEUVER AUTOPILOT HAVE BEEN INSTALLED IN AGAPBO. A NEW LISTING OF THE CONTENTS OF THE ANALYTICAL DATA BASE WILL BE GENERATED DURING THE WEEK...of the program (Reference 1) has been improved by providing the cap- ability to generate Postprocessing Data Blocks containing selected variables

Allometric Analysis Detects Brain Size-Independent Effects of Sex and Sex Chromosome Complement on Human Cerebellar Organization.

PubMed

Mankiw, Catherine; Park, Min Tae M; Reardon, P K; Fish, Ari M; Clasen, Liv S; Greenstein, Deanna; Giedd, Jay N; Blumenthal, Jonathan D; Lerch, Jason P; Chakravarty, M Mallar; Raznahan, Armin

2017-05-24

The cerebellum is a large hindbrain structure that is increasingly recognized for its contribution to diverse domains of cognitive and affective processing in human health and disease. Although several of these domains are sex biased, our fundamental understanding of cerebellar sex differences-including their spatial distribution, potential biological determinants, and independence from brain volume variation-lags far behind that for the cerebrum. Here, we harness automated neuroimaging methods for cerebellar morphometrics in 417 individuals to (1) localize normative male-female differences in raw cerebellar volume, (2) compare these to sex chromosome effects estimated across five rare sex (X/Y) chromosome aneuploidy (SCA) syndromes, and (3) clarify brain size-independent effects of sex and SCA on cerebellar anatomy using a generalizable allometric approach that considers scaling relationships between regional cerebellar volume and brain volume in health. The integration of these approaches shows that (1) sex and SCA effects on raw cerebellar volume are large and distributed, but regionally heterogeneous, (2) human cerebellar volume scales with brain volume in a highly nonlinear and regionally heterogeneous fashion that departs from documented patterns of cerebellar scaling in phylogeny, and (3) cerebellar organization is modified in a brain size-independent manner by sex (relative expansion of total cerebellum, flocculus, and Crus II-lobule VIIIB volumes in males) and SCA (contraction of total cerebellar, lobule IV, and Crus I volumes with additional X- or Y-chromosomes; X-specific contraction of Crus II-lobule VIIIB). Our methods and results clarify the shifts in human cerebellar organization that accompany interwoven variations in sex, sex chromosome complement, and brain size. SIGNIFICANCE STATEMENT Cerebellar systems are implicated in diverse domains of sex-biased behavior and pathology, but we lack a basic understanding of how sex differences in the human cerebellum are distributed and determined. We leverage a rare neuroimaging dataset to deconvolve the interwoven effects of sex, sex chromosome complement, and brain size on human cerebellar organization. We reveal topographically variegated scaling relationships between regional cerebellar volume and brain size in humans, which (1) are distinct from those observed in phylogeny, (2) invalidate a traditional neuroimaging method for brain volume correction, and (3) allow more valid and accurate resolution of which cerebellar subcomponents are sensitive to sex and sex chromosome complement. These findings advance understanding of cerebellar organization in health and sex chromosome aneuploidy. Copyright © 2017 the authors 0270-6474/17/375222-11$15.00/0.

Gray Matter Volume Decrease Distinguishes Schizophrenia From Bipolar Offspring During Childhood and Adolescence.

PubMed

Sugranyes, Gisela; de la Serna, Elena; Romero, Soledad; Sanchez-Gistau, Vanessa; Calvo, Anna; Moreno, Dolores; Baeza, Inmaculada; Diaz-Caneja, Covadonga M; Sanchez-Gutierrez, Teresa; Janssen, Joost; Bargallo, Nuria; Castro-Fornieles, Josefina

2015-08-01

There is increasing support toward the notion that schizophrenia and bipolar disorder share neurodevelopmental underpinnings, although areas of divergence remain. We set out to examine gray matter volume characteristics of child and adolescent offspring of patients with schizophrenia or bipolar disorder comparatively. In this 2-center study, magnetic resonance structural neuroimaging data were acquired in 198 children and adolescents (aged 6-17 years): 38 offspring of patients with schizophrenia, 77 offspring of patients with bipolar disorder, and 83 offspring of community controls. Analyses of global brain volumes and voxel-based morphometry (using familywise error correction) were conducted. There was an effect of group on total cerebral gray matter volume (F = 3.26, p = .041), driven by a decrease in offspring of patients with schizophrenia relative to offspring of controls (p = .035). At a voxel-based level, we observed an effect of group in the left inferior frontal cortex/anterior insula (F = 14.7, p < .001), which was driven by gray matter volume reduction in offspring of patients with schizophrenia relative to both offspring of controls (p = .044) and of patients with bipolar disorder (p < .001). No differences were observed between offspring of patients with bipolar disorder and offspring of controls in either global or voxel-based gray matter volumes. This first comparative study between offspring of patients with schizophrenia and bipolar disorder suggests that gray matter volume reduction in childhood and adolescence may be specific to offspring of patients with schizophrenia; this may index a greater neurodevelopmental impact of risk for schizophrenia relative to bipolar disorder during youth. Copyright © 2015 American Academy of Child and Adolescent Psychiatry. Published by Elsevier Inc. All rights reserved.

Technical note: In vitro total gas and methane production measurements from closed or vented rumen batch culture systems.

PubMed

Cattani, M; Tagliapietra, F; Maccarana, L; Hansen, H H; Bailoni, L; Schiavon, S

2014-03-01

This study compared measured gas production (GP) and computed CH4 production values provided by closed or vented bottles connected to gas collection bags. Two forages and 3 concentrates were incubated. Two incubations were conducted, where the 5 feeds were tested in 3 replicates in closed or vented bottles, plus 4 blanks, for a total of 64 bottles. Half of the bottles were not vented, and the others were vented at a fixed pressure (6.8 kPa) and gas was collected into one gas collection bag connected to each bottle. Each bottle (317 mL) was filled with 0.4000 ± 0.0010 g of feed sample and 60 mL of buffered rumen fluid (headspace volume = 257 mL) and incubated at 39.0°C for 24 h. At 24 h, gas samples were collected from the headspace of closed bottles or from headspace and bags of vented bottles and analyzed for CH4 concentration. Volumes of GP at 24 h were corrected for the gas dissolved in the fermentation fluid, according to Henry's law of gas solubility. Methane concentration (mL/100mL of GP) was measured and CH4 production (mL/g of incubated DM) was computed using corrected or uncorrected GP values. Data were analyzed for the effect of venting technique (T), feed (F), interaction between venting technique and feed (T × F), and incubation run as a random factor. Closed bottles provided lower uncorrected GP (-18%) compared with vented bottles, especially for concentrates. Correction for dissolved gas reduced but did not remove differences between techniques, and closed bottles (+25 mL of gas/g of incubated DM) had a greater magnitude of variation than did vented bottles (+1 mL of gas/g of incubated DM). Feeds differed in uncorrected and corrected GP, but the ranking was the same for the 2 techniques. The T × F interaction influenced uncorrected GP values, but this effect disappeared after correction. Closed bottles provided uncorrected CH4 concentrations 23% greater than that of vented bottles. Correction reduced but did not remove this difference. Methane concentration was influenced by feed but not by the T × F interaction. Corrected CH4 production was influenced by feed, but not by venting technique or the T × F interaction. Closed bottles provide good measurements of CH4 production but not of GP. Venting of bottles at low pressure permits a reliable evaluation of total GP and CH4 production. Copyright © 2014 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Correction of Age-Related Midface Volume Loss With Low-Volume Hyaluronic Acid Filler.

PubMed

Wilson, Monique Vanaman; Fabi, Sabrina Guillen; Greene, Ryan

2017-03-01

The pivotal approval trial for a smooth, highly cohesive, viscous, 20-mg/mL hyaluronic acid filler demonstrated sustained aesthetic improvement, with a mean injection volume of 6.65 mL. In daily practice, however, it is not often practical or necessary to use large injection volumes to achieve the desired cosmetic outcome. To assess the efficacy, longevity, and patient satisfaction associated with correction of age-related midface volume loss using the low volumes of hyaluronic acid filler more commonly used in day-to-day practice. A 2-center, retrospective cohort study examined medical records of 61 healthy patients who underwent treatment for facial volume loss with hyaluronic acid filler from November 1, 2013, through April 31, 2014. Follow-up visits were conducted at 1, 3, 6, and 12 months after the procedure. Data were pooled from a private facial plastic surgery practice in Weston, Florida, and a private cosmetic dermatology practice in San Diego, California. Patients were treated with hyaluronic acid filler according to the investigator's usual practices. The main outcome measure was patient-graded Global Aesthetic Improvement Scale scores at 1, 3, 6, and 12 months after treatment. Scores range from 1 to 5; 1 indicates very much improved and 5, worse. A total of 61 consecutive, healthy adult patients (mean [SD] age, 57.4 [12.8] years) with mild to severe facial volume loss were enrolled in the study. A total of 46 patients (75%) were white, 3 (5%) were black/African American, 9 (15%) were Hispanic/Latino, 1 (2%) was Asian/Pacific Islander, and 2 (3%) were other. Three patients (5%) were male, and 58 (95%) were female. Mean initial treatment volume was 1.6 mL. At follow-up, 29 patients (48%) elected to have a touch-up treatment; mean total touch-up volume was 1.4 mL. The patient-graded Global Aesthetic Improvement Scale scores at 1, 3, 6, and 12 months after treatment demonstrated that 73% (41 of 56) to 89% (24 of 27) of the study patients reported being very much or moderately improved. Most patients were rated by investigators on the Global Aesthetic Improvement Scale as very much or moderately improved at the 12-month follow-up. At 12 months after the procedure, 43 of 51 patients (84%) reported satisfaction with their outcome. At all time points, most patients would elect to undergo the procedure again (range, 17 [68%] to 61 [100%]). Adverse events were mild, and all resolved spontaneously within 14 days. At the 2-year follow-up, there were no reports of delayed adverse events. Midface volumization using the low volumes of hyaluronic acid filler more commonly used in daily clinical practice is effective and well tolerated. 3.

Mitral regurgitation: anatomy is destiny.

PubMed

Athanasuleas, Constantine L; Stanley, Alfred W H; Buckberg, Gerald D

2018-04-26

Mitral regurgitation (MR) occurs when any of the valve and ventricular mitral apparatus components are disturbed. As MR progresses, left ventricular remodelling occurs, ultimately causing heart failure when the enlarging left ventricle (LV) loses its conical shape and becomes globular. Heart failure and lethal ventricular arrhythmias may develop if the left ventricular end-systolic volume index exceeds 55 ml/m2. These adverse changes persist despite satisfactory correction of the annular component of MR. Our goal was to describe this process and summarize evolving interventions that reduce the volume of the left ventricle and rebuild its elliptical shape. This 'valve/ventricle' approach addresses the spherical ventricular culprit and offsets the limits of treating MR by correcting only its annular component.

Simple Correction of Alar Retraction by Conchal Cartilage Extension Grafts.

PubMed

Jang, Yong Jun; Kim, Sung Min; Lew, Dae Hyun; Song, Seung Yong

2016-11-01

Alar retraction is a challenging condition in rhinoplasty marked by exaggerated nostril exposure and awkwardness. Although various methods for correcting alar retraction have been introduced, none is without drawbacks. Herein, we report a simple procedure that is both effective and safe for correcting alar retraction using only conchal cartilage grafting. Between August 2007 and August 2009, 18 patients underwent conchal cartilage extension grafting to correct alar retraction. Conchal cartilage extension grafts were fixed to the caudal margins of the lateral crura and covered with vestibular skin advancement flaps. Preoperative and postoperative photographs were reviewed and analyzed. Patient satisfaction was surveyed and categorized into 4 groups (very satisfied, satisfied, moderate, or unsatisfied). According to the survey, 8 patients were very satisfied, 9 were satisfied, and 1 considered the outcome moderate, resulting in satisfaction for most patients. The average distance from the alar rim to the long axis of the nostril was reduced by 1.4 mm (3.6 to 2.2 mm). There were no complications, except in 2 cases with palpable cartilage step-off that resolved without any aesthetic problems. Conchal cartilage alar extension graft is a simple, effective method of correcting alar retraction that can be combined with aesthetic rhinoplasty conveniently, utilizing conchal cartilage, which is the most similar cartilage to alar cartilage, and requiring a lesser volume of cartilage harvest compared to previously devised methods. However, the current procedure lacks efficacy for severe alar retraction and a longer follow-up period may be required to substantiate the enduring efficacy of the current procedure.

Evaluation of a semiautomated lung mass calculation technique for internal dosimetry applications

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

Busse, Nathan; Erwin, William; Pan, Tinsu

2013-12-15

Purpose: The authors sought to evaluate a simple, semiautomated lung mass estimation method using computed tomography (CT) scans obtained using a variety of acquisition techniques and reconstruction parameters for mass correction of medical internal radiation dose-based internal radionuclide radiation absorbed dose estimates.Methods: CT scans of 27 patients with lung cancer undergoing stereotactic body radiation therapy treatment planning with PET/CT were analyzed retrospectively. For each patient, free-breathing (FB) and respiratory-gated 4DCT scans were acquired. The 4DCT scans were sorted into ten respiratory phases, representing one complete respiratory cycle. An average CT reconstruction was derived from the ten-phase reconstructions. Mid expiration breath-holdmore » CT scans were acquired in the same session for many patients. Deep inspiration breath-hold diagnostic CT scans of many of the patients were obtained from different scanning sessions at similar time points to evaluate the effect of contrast administration and maximum inspiration breath-hold. Lung mass estimates were obtained using all CT scan types, and intercomparisons made to assess lung mass variation according to scan type. Lung mass estimates using the FB CT scans from PET/CT examinations of another group of ten male and ten female patients who were 21–30 years old and did not have lung disease were calculated and compared with reference lung mass values. To evaluate the effect of varying CT acquisition and reconstruction parameters on lung mass estimation, an anthropomorphic chest phantom was scanned and reconstructed with different CT parameters. CT images of the lungs were segmented using the OsiriX MD software program with a seed point of about −850 HU and an interval of 1000. Lung volume, and mean lung, tissue, and air HUs were recorded for each scan. Lung mass was calculated by assuming each voxel was a linear combination of only air and tissue. The specific gravity of lung volume was calculated using the formula (lung HU − air HU)/(tissue HU − air HU), and mass = specific gravity × total volume × 1.04 g/cm{sup 3}.Results: The range of calculated lung masses was 0.51–1.29 kg. The average male and female lung masses during FB CT were 0.80 and 0.71 kg, respectively. The calculated lung mass varied across the respiratory cycle but changed to a lesser degree than did lung volume measurements (7.3% versus 15.4%). Lung masses calculated using deep inspiration breath-hold and average CT were significantly larger (p < 0.05) than were some masses calculated using respiratory-phase and FB CT. Increased voxel size and smooth reconstruction kernels led to high lung mass estimates owing to partial volume effects.Conclusions: Organ mass correction is an important component of patient-specific internal radionuclide dosimetry. Lung mass calculation necessitates scan-based density correction to account for volume changes owing to respiration. The range of lung masses in the authors’ patient population represents lung doses for the same absorbed energy differing from 25% below to 64% above the dose found using reference phantom organ masses. With proper management of acquisition parameters and selection of FB or midexpiration breath hold scans, lung mass estimates with about 10% population precision may be achieved.« less

Carotid Flow Time Test Performance for the Detection of Dehydration in Children With Diarrhea.

PubMed

Mackenzie, David C; Nasrin, Sabiha; Atika, Bita; Modi, Payal; Alam, Nur H; Levine, Adam C

2018-06-01

Unstructured clinical assessments of dehydration in children are inaccurate. Point-of-care ultrasound is a noninvasive diagnostic tool that can help evaluate the volume status; the corrected carotid artery flow time has been shown to predict volume depletion in adults. We sought to determine the ability of the corrected carotid artery flow time to identify dehydration in a population of children presenting with acute diarrhea in Dhaka, Bangladesh. Children presenting with acute diarrhea were recruited and rehydrated according to hospital protocols. The corrected carotid artery flow time was measured at the time of presentation. The percentage of weight change with rehydration was used to categorize each child's dehydration as severe (>9%), some (3%-9%), or none (<3%). A receiver operating characteristic curve was constructed to test the performance of the corrected carotid artery flow time for detecting severe dehydration. Linear regression was used to model the relationship between the corrected carotid artery flow time and percentage of dehydration. A total of 350 children (0-60 months) were enrolled. The mean corrected carotid artery flow time was 326 milliseconds (interquartile range, 295-351 milliseconds). The area under the receiver operating characteristic curve for the detection of severe dehydration was 0.51 (95% confidence interval, 0.42, 0.61). Linear regression modeling showed a weak association between the flow time and dehydration. The corrected carotid artery flow time was a poor predictor of severe dehydration in this population of children with diarrhea. © 2017 by the American Institute of Ultrasound in Medicine.

LLCEDATA and LLCECALC for Windows version 1.0, Volume 3: Software verification and validation

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

McFadden, J.G.

1998-09-04

LLCEDATA and LLCECALC for Windows are user-friendly computer software programs that work together to determine the proper waste designation, handling, and disposition requirements for Long Length Contaminated Equipment (LLCE). LLCEDATA reads from a variety of data bases to produce an equipment data file(EDF) that represents a snapshot of both the LLCE and the tank from which it originates. LLCECALC reads the EDF and the gamma assay file (AV2) that is produced by the flexible Receiver Gamma Energy Analysis System. LLCECALC performs corrections to the AV2 file as it is being read and characterizes the LLCE. Both programs produce a varietymore » of reports, including a characterization report and a status report. The status report documents each action taken by the user, LLCEDATA, and LLCECALC. Documentation for LLCEDATA and LLCECALC for Windows is available in three volumes. Volume 1 is a user`s manual, which is intended as a quick reference for both LLCEDATA and LLCECALC. Volume 2 is a technical manual, which discusses system limitations and provides recommendations to the LLCE process. Volume 3 documents LLCEDATA and LLCECALC`s verification and validation. Two of the three installation test cases, from Volume 1, are independently confirmed. Data bases used in LLCEDATA are verified and referenced. Both phases of LLCECALC process gamma and characterization, are extensively tested to verify that the methodology and algorithms used are correct.« less

Brain-region–specific alterations of the trajectories of neuronal volume growth throughout the lifespan in autism

PubMed Central

2014-01-01

Several morphometric studies have revealed smaller than normal neurons in the neocortex of autistic subjects. To test the hypothesis that abnormal neuronal growth is a marker of an autism-associated global encephalopathy, neuronal volumes were estimated in 16 brain regions, including various subcortical structures, Ammon’s horn, archicortex, cerebellum, and brainstem in 14 brains from individuals with autism 4 to 60 years of age and 14 age-matched control brains. This stereological study showed a significantly smaller volume of neuronal soma in 14 of 16 regions in the 4- to 8-year-old autistic brains than in the controls. Arbitrary classification revealed a very severe neuronal volume deficit in 14.3% of significantly altered structures, severe in 50%, moderate in 21.4%, and mild in 14.3% structures. This pattern suggests desynchronized neuronal growth in the interacting neuronal networks involved in the autistic phenotype. The comparative study of the autistic and control subject brains revealed that the number of structures with a significant volume deficit decreased from 14 in the 4- to 8-year-old autistic subjects to 4 in the 36- to 60-year-old. Neuronal volumes in 75% of the structures examined in the older adults with autism are comparable to neuronal volume in age-matched controls. This pattern suggests defects of neuronal growth in early childhood and delayed up-regulation of neuronal growth during adolescence and adulthood reducing neuron soma volume deficit in majority of examined regions. However, significant correction of neuron size but limited clinical improvements suggests that delayed correction does not restore functional deficits. PMID:24612906

Comparison of high-pressure CO 2 sorption isotherms on Eastern and Western US coals

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

Romanov, V; Hur, T -B; Fazio, J

2013-10-01

Accurate estimation of carbon dioxide (CO 2) sorption capacity of coal is important for planning the CO 2 sequestration efforts. In this work, we investigated sorption and swelling behavior of several Eastern and Western US coal samples from the Central Appalachian Basin and from San Juan Basin. The CO 2 sorption isotherms have been completed at 55°C for as received and dried samples. The role of mineral components in coal, the coal swelling, the effects of temperature and moisture, and the error propagation have been analyzed. Changes in void volume due to dewatering and other factors such as temporary cagingmore » of carbon dioxide molecules in coal matrix were identified among the main factors affecting accuracy of the carbon dioxide sorption isotherms. The (helium) void volume in the sample cells was measured before and after the sorption isotherm experiments and was used to build the volume-corrected data plots.« less

Bias in Estimation of Hippocampal Atrophy using Deformation-Based Morphometry Arises from Asymmetric Global Normalization: An Illustration in ADNI 3 Tesla MRI Data

PubMed Central

Yushkevich, Paul A.; Avants, Brian B.; Das, Sandhitsu R.; Pluta, John; Altinay, Murat; Craige, Caryne

2009-01-01

Measurement of brain change due to neurodegenerative disease and treatment is one of the fundamental tasks of neuroimaging. Deformation-based morphometry (DBM) has been long recognized as an effective and sensitive tool for estimating the change in the volume of brain regions over time. This paper demonstrates that a straightforward application of DBM to estimate the change in the volume of the hippocampus can result in substantial bias, i.e., an overestimation of the rate of change in hippocampal volume. In ADNI data, this bias is manifested as a non-zero intercept of the regression line fitted to the 6 and 12 month rates of hippocampal atrophy. The bias is further confirmed by applying DBM to repeat scans of subjects acquired on the same day. This bias appears to be the result of asymmetry in the interpolation of baseline and followup images during longitudinal image registration. Correcting this asymmetry leads to bias-free atrophy estimation. PMID:20005963

Synthesis from Design Requirements of a Hybrid System for Transport Aircraft Longitudinal Control. Volume 1

NASA Technical Reports Server (NTRS)

Hynes, Charles S.; Hardy, Gordon H.; Sherry, Lance

2007-01-01

Volume I of this report presents a new method for synthesizing hybrid systems directly from design requirements, and applies the method to design of a hybrid system for longitudinal control of transport aircraft. The resulting system satisfies general requirement for safety and effectiveness specified a priori, enabling formal validation to be achieved. Volume II contains seven appendices intended to make the report accessible to readers with backgrounds in human factors, fli ght dynamics and control. and formal logic. Major design goals are (1) system desi g n integrity based on proof of correctness at the design level, (2), significant simplification and cost reduction in system development and certification, and (3) improved operational efficiency, with significant alleviation of human-factors problems encountered by pilots in current transport aircraft. This report provides for the first time a firm technical basis for criteria governing design and certification of avionic systems for transport aircraft. It should be of primary interest to designers of next-generation avionic systems.

Synthesis from Design Requirements of a Hybrid System for Transport Aircraft Longitudinal Control. Volume 2

NASA Technical Reports Server (NTRS)

Hynes, Charles S.; Hardy, Gordon H.; Sherry, Lance

2007-01-01

Volume I of this report presents a new method for synthesizing hybrid systems directly from desi gn requirements, and applies the method to design of a hybrid system for longitudinal control of transport aircraft. The resulting system satisfies general requirement for safety and effectiveness specified a priori, enabling formal validation to be achieved. Volume II contains seven appendices intended to make the report accessible to readers with backgrounds in human factors, flight dynamics and control, and formal logic. Major design goals are (1) system design integrity based on proof of correctness at the design level, (2) significant simplification and cost reduction in system development and certification, and (3) improved operational efficiency, with significant alleviation of human-factors problems encountered by pilots in current transport aircraft. This report provides for the first time a firm technical basis for criteria governing design and certification of avionic systems for transport aircraft. It should be of primary interest to designers of next-generation avionic systems.

Impact of motion and partial volume effects correction on PET myocardial perfusion imaging using simultaneous PET-MR

NASA Astrophysics Data System (ADS)

Petibon, Yoann; Guehl, Nicolas J.; Reese, Timothy G.; Ebrahimi, Behzad; Normandin, Marc D.; Shoup, Timothy M.; Alpert, Nathaniel M.; El Fakhri, Georges; Ouyang, Jinsong

2017-01-01

PET is an established modality for myocardial perfusion imaging (MPI) which enables quantification of absolute myocardial blood flow (MBF) using dynamic imaging and kinetic modeling. However, heart motion and partial volume effects (PVE) significantly limit the spatial resolution and quantitative accuracy of PET MPI. Simultaneous PET-MR offers a solution to the motion problem in PET by enabling MR-based motion correction of PET data. The aim of this study was to develop a motion and PVE correction methodology for PET MPI using simultaneous PET-MR, and to assess its impact on both static and dynamic PET MPI using 18F-Flurpiridaz, a novel 18F-labeled perfusion tracer. Two dynamic 18F-Flurpiridaz MPI scans were performed on healthy pigs using a PET-MR scanner. Cardiac motion was tracked using a dedicated tagged-MRI (tMR) sequence. Motion fields were estimated using non-rigid registration of tMR images and used to calculate motion-dependent attenuation maps. Motion correction of PET data was achieved by incorporating tMR-based motion fields and motion-dependent attenuation coefficients into image reconstruction. Dynamic and static PET datasets were created for each scan. Each dataset was reconstructed as (i) Ungated, (ii) Gated (end-diastolic phase), and (iii) Motion-Corrected (MoCo), each without and with point spread function (PSF) modeling for PVE correction. Myocardium-to-blood concentration ratios (MBR) and apparent wall thickness were calculated to assess image quality for static MPI. For dynamic MPI, segment- and voxel-wise MBF values were estimated by non-linear fitting of a 2-tissue compartment model to tissue time-activity-curves. MoCo and Gating respectively decreased mean apparent wall thickness by 15.1% and 14.4% and increased MBR by 20.3% and 13.6% compared to Ungated images (P  <  0.01). Combined motion and PSF correction (MoCo-PSF) yielded 30.9% (15.7%) lower wall thickness and 82.2% (20.5%) higher MBR compared to Ungated data reconstructed without (with) PSF modeling (P  <  0.01). For dynamic PET, mean MBF across all segments were comparable for MoCo (0.72  ±  0.21 ml/min/ml) and Gating (0.69  ±  0.18 ml/min/ml). Ungated data yielded significantly lower mean MBF (0.59  ±  0.16 ml/min/ml). Mean MBF for MoCo-PSF was 0.80  ±  0.22 ml/min/ml, which was 37.9% (25.0%) higher than that obtained from Ungated data without (with) PSF correction (P  <  0.01). The developed methodology holds promise to improve the image quality and sensitivity of PET MPI studies performed using PET-MR.

Epsilon-aminocaproic acid influence in postoperative [corrected] bleeding and hemotransfusion [corrected] in mitral valve surgery.

PubMed

Benfatti, Ricardo Ádala; Carli, Amanda Ferreira; Silva, Guilherme Viotto Rodrigues da; Dias, Amaury Edgardo Mont'serrat Ávila Souza; Goldiano, José Anderson; Pontes, José Carlos Dorsa Vieira

2010-01-01

The epsilon aminocaproic acid is an antifibrinolytic used in cardiovascular surgery to inhibit the fibrinolysis and to reduce the bleeding after CPB. [corrected] To analyze the influence of the using of epsilon aminocaproic acid in the bleeding and in red-cell transfusion requirement in the first twenty-four hours postoperative of mitral valve surgery. Prospective studying, forty-two patients, randomized and divided in two equal groups: group #1 control and group #2--epsilon aminocaproic acid. In Group II were infused five grams of EACA in the induction of anesthesia, after full heparinization, CPB perfusate after reversal of heparin and one hour after the surgery, totaling 25 grams. In group I, saline solution was infused only in those moments. Group #1 showed average bleeding volume of 633.57 ± 305,7 ml, and Group #2, an average of 308.81 ± 210.1 ml, with significant statistic difference (P = 0.0003). Average volume of red-cell transfusion requirement in Groups 1 and 2 was, respectively, 942.86 ± 345.79 ml and 214.29 ± 330.58 ml, with significant difference (P < 0.0001). The epsilon aminocaproic acid was able to reduce the bleeding volume and the red-cell transfusion requirement in the immediate postoperative of patients submitted to mitral valve surgery.

Impact of Corrections to the Spallings Volume Calculation on Waste Isolation Pilot Plant Performance Assessment

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

Kicker, Dwayne Curtis; Herrick, Courtney G; Zeitler, Todd

2015-11-01

The numerical code DRSPALL (from direct release spallings) is written to calculate the volume of Waste Isolation Pilot Plant solid waste subject to material failure and transport to the surface (i.e., spallings) as a result of a hypothetical future inadvertent drilling intrusion into the repository. An error in the implementation of the DRSPALL finite difference equations was discovered and documented in a software problem report in accordance with the quality assurance procedure for software requirements. This paper describes the corrections to DRSPALL and documents the impact of the new spallings data from the modified DRSPALL on previous performance assessment calculations.more » Updated performance assessments result in more simulations with spallings, which generally translates to an increase in spallings releases to the accessible environment. Total normalized radionuclide releases using the modified DRSPALL data were determined by forming the summation of releases across each potential release pathway, namely borehole cuttings and cavings releases, spallings releases, direct brine releases, and transport releases. Because spallings releases are not a major contributor to the total releases, the updated performance assessment calculations of overall mean complementary cumulative distribution functions for total releases are virtually unchanged. Therefore, the corrections to the spallings volume calculation did not impact Waste Isolation Pilot Plant performance assessment calculation results.« less

[Bellows or bag? Testing 10 ventilators and some medical history comments].

PubMed

Kötter, K P; Maleck, W H; Altmannsberger, S; Herchet, J; Petroianu, G A

1998-01-01

We compared a new bellows ventilator (Kendall Cardiovent) with two other bellows (Dräger Resutator 63, Tagg Breathsaver) and seven bag or ball ventilators (Aerodyne Hope, Ambu Mark 3, Ambu Silicon, Dräger Resutator 2000, Laerdal Resu, Mercury CPR, Weinmann Combibag). Tidal volumes were measured with two Laerdal Recording Resusci Annies, one lying on the floor, one in a bed. Twelve participants performed mask ventilation with all ten devices on both manikins for two minutes, trying to achieve tidal volumes of between 0.8 and 1.21 as recommended by the AHA. The last ten ventilations each on the graphic strips were analysed for volume. The participants scored handling of the devices on a 6-point scale (1 = very good, 6 = insufficient). The results of the Cardiovent were compared to those of the other devices by rank sum test (percentage of correct ventilations) and sign test (subjective handling). The Cardiovent provided exact ventilation with 95% of ventilations) on the floor and 78% of ventilations in bed in the recommended range. However, the percentage of correct ventilations with the Cardiovent was not significantly different to the other devices except for a lower percentage of correct ventilations with the Combibag in the in bed setting. Concerning subjective handling, the Cardiovent was significantly superior to several ball ventilators.

The effect on cardiopulmonary function after thoracoplasty in pectus carinatum: a systematic literature review.

PubMed

Sigl, Stephan; Del Frari, Barbara; Harasser, Carina; Schwabegger, Anton H

2018-03-01

Creating an aesthetically appealing result using thoracoplasty, especially when correcting extensive deformities, but only causing low morbidity, is challenging. The frequency of thoracoplasties in cases of pectus carinatum (PC) has increased due to improved experience and modified surgical techniques, resulting in low morbidity and low complication rates. The indications for surgical treatment are still controversial and, in most cases, remain aesthetic or psychological rather than physiological. However, whether cardiopulmonary function changes after surgical repair remains a matter of controversy. We sought to investigate and shed light on published knowledge regarding this question. We searched MEDLINE and PubMed databases, using various defined search phrases and inclusion criteria, to identify articles on pre- and postoperative cardiopulmonary evaluation and outcomes. Six studies met the inclusion criteria: 5 studies evaluated patients with PC for cardiopulmonary outcomes after chest wall surgery and 1 did so following conservative compression treatment. In these studies, surgical and conservative correction of PC did not reduce absolute lung volumes and spirometric measurements and consequently had no pathogenic effect on cardiopulmonary function. The results of this systematic review suggest that surgical correction of PC has no symptomatic pathogenic effect on cardiopulmonary function. The results, however, revealed both heterogeneity in the examinations used and inconsistent methods within each study. Further prospective trials with a stronger methodological design are necessary to objectively confirm that surgical correction of PC does not impair cardiopulmonary function. © The Author 2017. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.

Validation of Test Weighing Protocol to Estimate Enteral Feeding Volumes in Preterm Infants.

PubMed

Rankin, Michael W; Jimenez, Elizabeth Yakes; Caraco, Marina; Collinson, Marie; Lostetter, Lisa; DuPont, Tara L

2016-11-01

To evaluate the accuracy of pre- and postfeeding weights to estimate enteral feeding volumes in preterm infants. Single-center prospective cohort study of infants 28-36 weeks' corrected age receiving gavage feedings. For each test weight, 3 pre- and 3 postgavage feeding weights were obtained by study personnel, blinded to feeding volume, via a specific protocol. The correlation between test weight difference and actual volume ingested was assessed by the use of summary statistics, Spearman rho, and graphical analyses. The relationship between categorical predictive variables and a predefined acceptable difference (±5 mL) was assessed with the χ 2 or Fisher exact test. A total of 101 test weights were performed in 68 infants. Estimated and actual feeding volumes were highly correlated (r = 0.94, P < .001), with a mean absolute difference of 2.95 mL (SD: 2.70; range: 0, 12.3 mL; 5th, 95th percentile: 0, 9.3); 85% of test weights were within ±5 mL of actual feeding volume and did not vary significantly by corrected age, feeding tube or respiratory support type, feeding duration or volume, formula vs breast milk, or caloric density. With adherence to study protocol, 89% of test weights (66/74) were within ±5 mL of actual volume, compared with 71% (19/27, P = .04) when concerns about protocol adherence were noted (eg, difficulty securing oxygen tubing). Via the use of a standard protocol, feeding volumes can be estimated accurately by pre- and postfeeding weights. Test weighing could be a valuable tool to support direct breastfeeding in the neonatal intensive care unit. Copyright © 2016 Elsevier Inc. All rights reserved.

Bidirectional Contrast agent leakage correction of dynamic susceptibility contrast (DSC)-MRI improves cerebral blood volume estimation and survival prediction in recurrent glioblastoma treated with bevacizumab.

PubMed

Leu, Kevin; Boxerman, Jerrold L; Lai, Albert; Nghiemphu, Phioanh L; Pope, Whitney B; Cloughesy, Timothy F; Ellingson, Benjamin M

2016-11-01

To evaluate a leakage correction algorithm for T 1 and T2* artifacts arising from contrast agent extravasation in dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) that accounts for bidirectional contrast agent flux and compare relative cerebral blood volume (CBV) estimates and overall survival (OS) stratification from this model to those made with the unidirectional and uncorrected models in patients with recurrent glioblastoma (GBM). We determined median rCBV within contrast-enhancing tumor before and after bevacizumab treatment in patients (75 scans on 1.5T, 19 scans on 3.0T) with recurrent GBM without leakage correction and with application of the unidirectional and bidirectional leakage correction algorithms to determine whether rCBV stratifies OS. Decreased post-bevacizumab rCBV from baseline using the bidirectional leakage correction algorithm significantly correlated with longer OS (Cox, P = 0.01), whereas rCBV change using the unidirectional model (P = 0.43) or the uncorrected rCBV values (P = 0.28) did not. Estimates of rCBV computed with the two leakage correction algorithms differed on average by 14.9%. Accounting for T 1 and T2* leakage contamination in DSC-MRI using a two-compartment, bidirectional rather than unidirectional exchange model might improve post-bevacizumab survival stratification in patients with recurrent GBM. J. Magn. Reson. Imaging 2016;44:1229-1237. © 2016 International Society for Magnetic Resonance in Medicine.

Overcoming turbulence-induced space-variant blur by using phase-diverse speckle.

PubMed

Thelen, Brian J; Paxman, Richard G; Carrara, David A; Seldin, John H

2009-01-01

Space-variant blur occurs when imaging through volume turbulence over sufficiently large fields of view. Space-variant effects are particularly severe in horizontal-path imaging, slant-path (air-to-ground or ground-to-air) geometries, and ground-based imaging of low-elevation satellites or astronomical objects. In these geometries, the isoplanatic angle can be comparable to or even smaller than the diffraction-limited resolution angle. We report on a postdetection correction method that seeks to correct for the effects of space-variant aberrations, with the goal of reconstructing near-diffraction-limited imagery. Our approach has been to generalize the method of phase-diverse speckle (PDS) by using a physically motivated distributed-phase-screen model. Simulation results are presented that demonstrate the reconstruction of near-diffraction-limited imagery under both matched and mismatched model assumptions. In addition, we present evidence that PDS could be used as a beaconless wavefront sensor in a multiconjugate adaptive optics system when imaging extended scenes.

SeaWiFS Technical Report Series. Volume 40; SeaWiFS Calibration Topics

NASA Technical Reports Server (NTRS)

Barnes, Robert A.; Eplee, Robert E., Jr.; Yeh, Eueng-nan; Esaias, Wayne E.

1997-01-01

For Earth-observing satellite instruments, it was standard to consider each instrument band to have a spectral response that is infinitely narrow, i.e., to have a response from a single wavelength. The SeaWiFS bands, however, have nominal spectral bandwidths of 20 and 40 nm. These bandwidths effect the SeaWiFS measurements on orbit. The effects are also linked to the manner in which the instrument was calibrated and to the spectral shape of the radiance that SeaWiFS views. The spectral shape of that radiance will not be well known on orbit. In this technical memorandum, two source spectra are examined. The first is a 12,000 K Planck function, and the second is based on the modeling results of H. Gordon at the University of Miami. By comparing these spectra, the best available corrections to the SeaWiFS measurements for source spectral shape, plus estimates of the uncertainties in these corrections, can be tabulated.

Enabling full-field physics-based optical proximity correction via dynamic model generation

NASA Astrophysics Data System (ADS)

Lam, Michael; Clifford, Chris; Raghunathan, Ananthan; Fenger, Germain; Adam, Kostas

2017-07-01

As extreme ultraviolet lithography becomes closer to reality for high volume production, its peculiar modeling challenges related to both inter and intrafield effects have necessitated building an optical proximity correction (OPC) infrastructure that operates with field position dependency. Previous state-of-the-art approaches to modeling field dependency used piecewise constant models where static input models are assigned to specific x/y-positions within the field. OPC and simulation could assign the proper static model based on simulation-level placement. However, in the realm of 7 and 5 nm feature sizes, small discontinuities in OPC from piecewise constant model changes can cause unacceptable levels of edge placement errors. The introduction of dynamic model generation (DMG) can be shown to effectively avoid these dislocations by providing unique mask and optical models per simulation region, allowing a near continuum of models through the field. DMG allows unique models for electromagnetic field, apodization, aberrations, etc. to vary through the entire field and provides a capability to precisely and accurately model systematic field signatures.

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

Bialas, A.; Czyz, W.; Zalewski, K.

The relation between Renyi entropies and moments of the Wigner function, representing the quantum mechanical description of the M-particle semi-inclusive distribution at freeze-out, is investigated. It is shown that in the limit of infinite volume of the system, the classical and quantum descriptions are equivalent. Finite volume corrections are derived and shown to be small for systems encountered in relativistic heavy ion collisions.

Historical and Political Gazeteer of Afghanistan. Volume 1, Badakhshan Province and Northeastern Afghanistan.

ERIC Educational Resources Information Center

Adamec, Ludwig W., Ed.

Combining the most important geographical data with historical, political, and cultural information, this work, one of six volumes designed as a tool of research and a general reference source, updates and includes a previous publication compiled in 1914 with corrections and additions of maps and considerable new material to take into account…

30 CFR 250.198 - Documents incorporated by reference.

Code of Federal Regulations, 2014 CFR

2014-07-01

... Conditions, May 2007; incorporated by reference at § 250.901; (3) API Bulletin 2INT-EX, Interim Guidance for...; incorporated by reference at § 250.1202; (34) API MPMS, Chapter 11.1—Volume Correction Factors, Volume 1, Table...; (35) API MPMS, Chapter 11.2.2—Compressibility Factors for Hydrocarbons: 0.350-0.637 Relative Density...

30 CFR 250.198 - Documents incorporated by reference.

Code of Federal Regulations, 2013 CFR

2013-07-01

... Conditions, May 2007; incorporated by reference at § 250.901; (3) API Bulletin 2INT-EX, Interim Guidance for...; incorporated by reference at § 250.1202; (34) API MPMS, Chapter 11.1—Volume Correction Factors, Volume 1, Table...; (35) API MPMS, Chapter 11.2.2—Compressibility Factors for Hydrocarbons: 0.350-0.637 Relative Density...

Compulsive sexual behavior: Prefrontal and limbic volume and interactions.

PubMed

Schmidt, Casper; Morris, Laurel S; Kvamme, Timo L; Hall, Paula; Birchard, Thaddeus; Voon, Valerie

2017-03-01

Compulsive sexual behaviors (CSB) are relatively common and associated with significant personal and social dysfunction. The underlying neurobiology is still poorly understood. The present study examines brain volumes and resting state functional connectivity in CSB compared with matched healthy volunteers (HV). Structural MRI (MPRAGE) data were collected in 92 subjects (23 CSB males and 69 age-matched male HV) and analyzed using voxel-based morphometry. Resting state functional MRI data using multi-echo planar sequence and independent components analysis (ME-ICA) were collected in 68 subjects (23 CSB subjects and 45 age-matched HV). CSB subjects showed greater left amygdala gray matter volumes (small volume corrected, Bonferroni adjusted P < 0.01) and reduced resting state functional connectivity between the left amygdala seed and bilateral dorsolateral prefrontal cortex (whole brain, cluster corrected FWE P < 0.05) compared with HV. CSB is associated with elevated volumes in limbic regions relevant to motivational salience and emotion processing, and impaired functional connectivity between prefrontal control regulatory and limbic regions. Future studies should aim to assess longitudinal measures to investigate whether these findings are risk factors that predate the onset of the behaviors or are consequences of the behaviors. Hum Brain Mapp 38:1182-1190, 2017. © 2016 Wiley Periodicals, Inc. © 2016 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.

A study of shape-dependent partial volume correction in pet imaging using ellipsoidal phantoms fabricated via rapid prototyping

NASA Astrophysics Data System (ADS)

Mille, Matthew M.

Positron emission tomography (PET) with 2-[18F]fluoro-2-deoxy-D-glucose (FDG) is being increasingly recognized as an important tool for quantitative assessment of tumor response because of its ability to capture functional information about the tumor's metabolism. However, despite many advances in PET technology, measurements of tumor radiopharmaceutical uptake in PET are still challenged by issues of accuracy and consistency, thereby compromising the use of PET as a surrogate endpoint in clinical trials. One limiting component of the overall uncertainty in PET is the relatively poor spatial resolution of the images which directly affects the accuracy of the tumor radioactivity measurements. These spatial resolution effects, colloquially known as the partial volume effect (PVE), are a function of the characteristics of the scanner as well as the tumor being imaged. Previous efforts have shown that the PVE depends strongly on the tumor volume and the background-to-tumor activity concentration ratio. The PVE is also suspected to be a function of tumor shape, although to date no systematic study of this effect has been performed. This dissertation seeks to help fill the gap in the current knowledge about the shape-dependence of the PVE by attempting to quantify, through both theoretical calculation and experimental measurement, the magnitude of the shape effect for ellipsoidal tumors. An experimental investigation of the tumor shape effect necessarily requires tumor phantoms of multiple shapes. Hence, a prerequisite for this research was the design and fabrication of hollow tumor phantoms which could be filled uniformly with radioactivity and imaged on a PET scanner. The phantom fabrication was achieved with the aid of stereolithography and included prolate ellipsoids of various axis ratios. The primary experimental method involved filling the tumor phantoms with solutions of 18F whose activity concentrations were known and traceable to primary radioactivity standards held by the National Institute of Standards and Technology (NIST). The tumor phantoms were then placed inside a Jaszczak cylinder (representing the human body) and imaged on a PET scanner located at NIST. This experimental approach allowed for the testing of: (1) The relative difference between tumors phantoms of different shapes, but same volume; (2) The overall accuracy of the PET measurements in terms of a ground truth reference value. Theoretical calculations of the tumor shape effect were also performed by mathematically convolving the phantom shapes with a 3D Gaussian point-spread function, and the results of the calculations were compared with the experimental data. The data show that the shape effect in PET tumor imaging can be as large as 15% for ellipsoid phantoms with axis ratios of 2:1, volume of 1.15 cm 3, and tumor-to-background activity concentration ratio of 9:1. This is explained by a greater loss of counts along the minor axis direction in the ellipsoid tumors compared to that of spheres of the same volume. The results of this PhD research confirm the existence of a tumor shape effect PET imaging. However, except in the case of ellipsoids with major-to-minor axis ratio greater than 2:1, a correction for the effect using recovery coefficients is expected to be challenging because its magnitude is comparable to the repeatability of the PET measurements.

Cardiovascular magnetic resonance of cardiac function and myocardial mass in preterm infants: a preliminary study of the impact of patent ductus arteriosus

PubMed Central

2014-01-01

Background Many pathologies seen in the preterm population are associated with abnormal blood supply, yet robust evaluation of preterm cardiac function is scarce and consequently normative ranges in this population are limited. The aim of this study was to quantify and validate left ventricular dimension and function in preterm infants using cardiovascular magnetic resonance (CMR). An initial investigation of the impact of the common congenital defect patent ductus arteriosus (PDA) was then carried out. Methods Steady State Free Procession short axis stacks were acquired. Normative ranges of left ventricular end diastolic volume (EDV), stroke volume (SV), left ventricular output (LVO), ejection fraction (EF), left ventricular (LV) mass, wall thickness and fractional thickening were determined in “healthy” (control) neonates. Left ventricular parameters were then investigated in PDA infants. Unpaired student t-tests compared the 2 groups. Multiple linear regression analysis assessed impact of shunt volume in PDA infants, p-value ≤ 0.05 being significant. Results 29 control infants median (range) corrected gestational age at scan 34+6(31+1-39+3) weeks were scanned. EDV, SV, LVO, LV mass normalized by weight and EF were shown to decrease with increasing corrected gestational age (cGA) in controls. In 16 PDA infants (cGA 30+3(27+3-36+1) weeks) left ventricular dimension and output were significantly increased, yet there was no significant difference in ejection fraction and fractional thickening between the two groups. A significant association between shunt volume and increased left ventricular mass correcting for postnatal age and corrected gestational age existed. Conclusion CMR assessment of left ventricular function has been validated in neonates, providing more robust normative ranges of left ventricular dimension and function in this population. Initial investigation of PDA infants would suggest that function is relatively maintained. PMID:25160730

The Voices of Youth: Perspectives and Recommendations from Young Adults Involved in Juvenile Corrections. Information Brief. Volume 5, Issue 2

ERIC Educational Resources Information Center

Stenhjem, Pam

2006-01-01

This brief describes two exceptional model programs for adjudicated youth with disabilities: Woodland Hills Residential Facility in Duluth, Minnesota and the Minnesota Correctional Facility-Walter McGinnis High School in Red Wing, Minnesota. The brief shares best practices from research about these programs as well as insight, commentary, and…

Divergence correction schemes in finite difference method for 3D tensor CSAMT in axial anisotropic media

NASA Astrophysics Data System (ADS)

Wang, Kunpeng; Tan, Handong; Zhang, Zhiyong; Li, Zhiqiang; Cao, Meng

2017-05-01

Resistivity anisotropy and full-tensor controlled-source audio-frequency magnetotellurics (CSAMT) have gradually become hot research topics. However, much of the current anisotropy research for tensor CSAMT only focuses on the one-dimensional (1D) solution. As the subsurface is rarely 1D, it is necessary to study three-dimensional (3D) model response. The staggered-grid finite difference method is an effective simulation method for 3D electromagnetic forward modelling. Previous studies have suggested using the divergence correction to constrain the iterative process when using a staggered-grid finite difference model so as to accelerate the 3D forward speed and enhance the computational accuracy. However, the traditional divergence correction method was developed assuming an isotropic medium. This paper improves the traditional isotropic divergence correction method and derivation process to meet the tensor CSAMT requirements for anisotropy using the volume integral of the divergence equation. This method is more intuitive, enabling a simple derivation of a discrete equation and then calculation of coefficients related to the anisotropic divergence correction equation. We validate the result of our 3D computational results by comparing them to the results computed using an anisotropic, controlled-source 2.5D program. The 3D resistivity anisotropy model allows us to evaluate the consequences of using the divergence correction at different frequencies and for two orthogonal finite length sources. Our results show that the divergence correction plays an important role in 3D tensor CSAMT resistivity anisotropy research and offers a solid foundation for inversion of CSAMT data collected over an anisotropic body.

3-D transcranial ultrasound imaging with bilateral phase aberration correction of multiple isoplanatic patches: a pilot human study with microbubble contrast enhancement.

PubMed

Lindsey, Brooks D; Nicoletto, Heather A; Bennett, Ellen R; Laskowitz, Daniel T; Smith, Stephen W

2014-01-01

With stroke currently the second-leading cause of death globally, and 87% of all strokes classified as ischemic, the development of a fast, accessible, cost-effective approach for imaging occlusive stroke could have a significant impact on health care outcomes and costs. Although clinical examination and standard computed tomography alone do not provide adequate information for understanding the complex temporal events that occur during an ischemic stroke, ultrasound imaging is well suited to the task of examining blood flow dynamics in real time and may allow for localization of a clot. A prototype bilateral 3-D ultrasound imaging system using two matrix array probes on either side of the head allows for correction of skull-induced aberration throughout two entire phased array imaging volumes. We investigated the feasibility of applying this custom correction technique in five healthy volunteers with Definity microbubble contrast enhancement. Subjects were scanned simultaneously via both temporal acoustic windows in 3-D color flow mode. The number of color flow voxels above a common threshold increased as a result of aberration correction in five of five subjects, with a mean increase of 33.9%. The percentage of large arteries visualized by 3-D color Doppler imaging increased from 46% without aberration correction to 60% with aberration correction. Copyright © 2014 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Teaching basic life support: a prospective randomized study on low-cost training strategies in secondary schools.

PubMed

Van Raemdonck, Veerle; Monsieurs, Koenraad G; Aerenhouts, Dirk; De Martelaer, Kristine

2014-08-01

Cardiopulmonary resuscitation (CPR) training at school is recommended. Limited school resources prevent implementation. The learning efficacy of low-cost training strategies is unknown. To evaluate the efficacy of different CPR learning strategies using low-cost didactic tools. Children (n=593, 15-16 years) were randomized to four training conditions: (1) manikin+teacher instruction (control group), (2) manikin+video instruction, (3) foam dice+plastic bag+peer training+teacher instruction, and (4) foam dice+plastic bag+peer training+video instruction. After a 50 min training, a 3 min CPR test on a manikin was performed using SkillReporting Software (Laerdal, Norway), and repeated after 6 months. The data of children without previous CPR training were analysed. Analysis of variance and the χ-test assessed differences between groups. Complete data sets were available for 165 pupils. Initially, group 3 scored lower on the mean ventilation volume (P<0.05). The control group scored better than the alternative groups (P<0.05) on the mean compression rate. After 6 months, the differences disappeared. All groups scored equally on ventilation volume (P=0.12), compression depth (P=0.11), compression rate (P=0.10), correct hand position (P=0.46) and number of correct compressions (P=0.76). Ventilation volume was sufficient in 32% of the pupils, 18% had a correct compression depth and 59% had a correct compression rate. Training efficacy with low-cost equipment was not different from training with a manikin. The outcome for all training strategies was suboptimal. The basics of CPR can be taught with alternative equipment if manikins are not available.

Revisiting the Logan plot to account for non-negligible blood volume in brain tissue.

PubMed

Schain, Martin; Fazio, Patrik; Mrzljak, Ladislav; Amini, Nahid; Al-Tawil, Nabil; Fitzer-Attas, Cheryl; Bronzova, Juliana; Landwehrmeyer, Bernhard; Sampaio, Christina; Halldin, Christer; Varrone, Andrea

2017-08-18

Reference tissue-based quantification of brain PET data does not typically include correction for signal originating from blood vessels, which is known to result in biased outcome measures. The bias extent depends on the amount of radioactivity in the blood vessels. In this study, we seek to revisit the well-established Logan plot and derive alternative formulations that provide estimation of distribution volume ratios (DVRs) that are corrected for the signal originating from the vasculature. New expressions for the Logan plot based on arterial input function and reference tissue were derived, which included explicit terms for whole blood radioactivity. The new methods were evaluated using PET data acquired using [ 11 C]raclopride and [ 18 F]MNI-659. The two-tissue compartment model (2TCM), with which signal originating from blood can be explicitly modeled, was used as a gold standard. DVR values obtained for [ 11 C]raclopride using the either blood-based or reference tissue-based Logan plot were systematically underestimated compared to 2TCM, and for [ 18 F]MNI-659, a proportionality bias was observed, i.e., the bias varied across regions. The biases disappeared when optimal blood-signal correction was used for respective tracer, although for the case of [ 18 F]MNI-659 a small but systematic overestimation of DVR was still observed. The new method appears to remove the bias introduced due to absence of correction for blood volume in regular graphical analysis and can be considered in clinical studies. Further studies are however required to derive a generic mapping between plasma and whole-blood radioactivity levels.

Finite volume for three-flavour Partially Quenched Chiral Perturbation Theory through NNLO in the meson sector

NASA Astrophysics Data System (ADS)

Bijnens, Johan; Rössler, Thomas

2015-11-01

We present a calculation of the finite volume corrections to meson masses and decay constants in three flavour Partially Quenched Chiral Perturbation Theory (PQChPT) through two-loop order in the chiral expansion for the flavour-charged (or off-diagonal) pseudoscalar mesons. The analytical results are obtained for three sea quark flavours with one, two or three different masses. We reproduce the known infinite volume results and the finite volume results in the unquenched case. The calculation has been performed using the supersymmetric formulation of PQChPT as well as with a quark flow technique.

Three-Dimensional Mathematical Model of Oxygen Transport Behavior in Electroslag Remelting Process

NASA Astrophysics Data System (ADS)

Huang, Xuechi; Li, Baokuan; Liu, Zhongqiu

2018-04-01

A transient three-dimensional model has been proposed to investigate the oxygen transport behavior in electroslag remelting process. The electromagnetism, heat transfer, multiphase flow, and species transport were calculated simultaneously by finite volume method. The volume of fluid approach was adopted to trace the metal-slag-air three-phase flow. Based on the necessary thermodynamics of oxygen transport behavior, a kinetic model was established to predict the mass source terms in species transport equation. The kinetic correction factor was proposed to account for the effect of the oxide scale formed on the electrode on the FeO content in slag. Finally, the effect of applied current on the oxygen transfer was studied. The predicted result agrees well with the measured data when the kinetic correction factor is set to be 0.5. The temperature distribution that affects the thermodynamics differs at the interfaces. The oxygen in air is absorbed into slag due to the oxidation at the slag/air interface. The Fe2O3 in slag and the oxide scale contribute to the increase of FeO content in slag, and the latter one plays the leading role. The oxygen transfer from slag to metal mainly occurs during the formation of the droplet at the slag/metal droplet interface. With the current increasing from 1200 to 1800 A, the oxygen content increases from 76.4 to 89.8 ppm, and then slightly declines to 89.2 ppm when the current increases to 2100 A.

A Prospective, Open-Label, Observational, Postmarket Study Evaluating VYC-17.5L for the Correction of Moderate to Severe Nasolabial Folds Over 12 Months

PubMed Central

Sattler, Gerhard; Philipp-Dormston, Wolfgang G.; Van Den Elzen, Helga; Van Der Walt, Cornelius; Nathan, Myooran; Kerson, Graeme; Dhillon, Benjeev

2017-01-01

BACKGROUND VYC-17.5L (17.5 mg/mL hyaluronic acid, 0.3% lidocaine) is a dermal filler intended for deep dermis injection for the treatment of skin depressions. OBJECTIVE To evaluate 12-month effectiveness and safety of VYC-17.5L for the treatment of moderate/severe nasolabial folds (NLFs). METHODS Subjects ≥18 years old with moderate/severe NLFs were recruited (N = 70). Injected volume was aimed at achieving optimum correction; top-up treatment was given at 2 weeks if needed. The primary endpoint was investigator-assessed change in NLF severity over 12 months using the validated photonumeric NLF Severity Scale. Secondary endpoints included investigator- and subject-assessed satisfaction and safety. Adverse events judged to be more severe or prolonged than routinely observed were recorded. RESULTS Sixty-five subjects completed study requirements. Mean volume injected was 3.0 ± 1.0 mL for both NLFs combined. Significant improvement was maintained in investigator-assessed NLF severity at 12 months, and investigators and subjects reported high satisfaction with VYC-17.5L throughout the study. Two unexpected adverse events were reported: (1) redness, swelling, and decreased sensitivity (resolved after 4 days) and (2) swelling (resolved after 48 hours); neither event was serious or life threatening. CONCLUSION VYC-17.5L is effective and well tolerated for the treatment of moderate to severe NLFs for 1 year. PMID:28165349

Measurement of gastric meal and secretion volumes using magnetic resonance imaging

NASA Astrophysics Data System (ADS)

Hoad, C. L.; Parker, H.; Hudders, N.; Costigan, C.; Cox, E. F.; Perkins, A. C.; Blackshaw, P. E.; Marciani, L.; Spiller, R. C.; Fox, M. R.; Gowland, P. A.

2015-02-01

MRI can assess multiple gastric functions without ionizing radiation. However, time consuming image acquisition and analysis of gastric volume data, plus confounding of gastric emptying measurements by gastric secretions mixed with the test meal have limited its use to research centres. This study presents an MRI acquisition protocol and analysis algorithm suitable for the clinical measurement of gastric volume and secretion volume. Reproducibility of gastric volume measurements was assessed using data from 10 healthy volunteers following a liquid test meal with rapid MRI acquisition within one breath-hold and semi-automated analysis. Dilution of the ingested meal with gastric secretion was estimated using a respiratory-triggered T1 mapping protocol. Accuracy of the secretion volume measurements was assessed using data from 24 healthy volunteers following a mixed (liquid/solid) test meal with MRI meal volumes compared to data acquired using gamma scintigraphy (GS) on the same subjects studied on a separate study day. The mean ± SD coefficient of variance between 3 observers for both total gastric contents (including meal, secretions and air) and just the gastric contents (meal and secretion only) was 3  ±  2% at large gastric volumes (>200 ml). Mean ± SD secretion volumes post meal ingestion were 64  ±  51 ml and 110  ±  40 ml at 15 and 75 min, respectively. Comparison with GS meal volumes, showed that MRI meal only volume (after correction for secretion volume) were similar to GS, with a linear regression gradient ± std err of 1.06  ±  0.10 and intercept -11  ±  24 ml. In conclusion, (i) rapid volume acquisition and respiratory triggered T1 mapping removed the requirement to image during prolonged breath-holds (ii) semi-automatic analysis greatly reduced the time required to derive measurements and (iii) correction for secretion volumes provided accurate assessment of gastric meal volumes and emptying. Together these features provide the scientific basis of a protocol which would be suitable in clinical practice.

Multispectral scanner system for ERTS: Four band scanner system. Volume 2: Engineering model panoramic pictures and engineering tests

NASA Technical Reports Server (NTRS)

1972-01-01

This document is Volume 2 of three volumes of the Final Report for the four band Multispectral Scanner System (MSS). The results are contained of an analysis of pictures of actual outdoor scenes imaged by the engineering model MSS for spectral response, resolution, noise, and video correction. Also included are the results of engineering tests on the MSS for reflectance and saturation from clouds. Finally, two panoramic pictures of Yosemite National Park are provided.

Measured body composition and geometrical data of four ``virtual family'' members for thermoregulatory modeling

NASA Astrophysics Data System (ADS)

Xu, Xiaojiang; Rioux, Timothy P.; MacLeod, Tynan; Patel, Tejash; Rome, Maxwell N.; Potter, Adam W.

2017-03-01

The purpose of this paper is to develop a database of tissue composition, distribution, volume, surface area, and skin thickness from anatomically correct human models, the virtual family. These models were based on high-resolution magnetic resonance imaging (MRI) of human volunteers, including two adults (male and female) and two children (boy and girl). In the segmented image dataset, each voxel is associated with a label which refers to a tissue type that occupies up that specific cubic millimeter of the body. The tissue volume was calculated from the number of the voxels with the same label. Volumes of 24 organs in body and volumes of 7 tissues in 10 specific body regions were calculated. Surface area was calculated from the collection of voxels that are touching the exterior air. Skin thicknesses were estimated from its volume and surface area. The differences between the calculated and original masses were about 3 % or less for tissues or organs that are important to thermoregulatory modeling, e.g., muscle, skin, and fat. This accurate database of body tissue distributions and geometry is essential for the development of human thermoregulatory models. Data derived from medical imaging provide new effective tools to enhance thermal physiology research and gain deeper insight into the mechanisms of how the human body maintains heat balance.

Ice Ih anomalies: Thermal contraction, anomalous volume isotope effect, and pressure-induced amorphization.

PubMed

Salim, Michael A; Willow, Soohaeng Yoo; Hirata, So

2016-05-28

Ice Ih displays several anomalous thermodynamic properties such as thermal contraction at low temperatures, an anomalous volume isotope effect (VIE) rendering the volume of D2O ice greater than that of H2O ice, and a pressure-induced transition to the high-density amorphous (HDA) phase. Furthermore, the anomalous VIE increases with temperature, despite its quantum-mechanical origin. Here, embedded-fragment ab initio second-order many-body perturbation (MP2) theory in the quasiharmonic approximation (QHA) is applied to the Gibbs energy of an infinite, proton-disordered crystal of ice Ih at wide ranges of temperatures and pressures. The quantum effect of nuclei moving in anharmonic potentials is taken into account from first principles without any empirical or nonsystematic approximation to either the electronic or vibrational Hamiltonian. MP2 predicts quantitatively correctly the thermal contraction at low temperatures, which is confirmed to originate from the volume-contracting hydrogen-bond bending modes (acoustic phonons). It qualitatively reproduces (but underestimates) the thermal expansion at higher temperatures, caused by the volume-expanding hydrogen-bond stretching (and to a lesser extent librational) modes. The anomalous VIE is found to be the result of subtle cancellations among closely competing isotope effects on volume from all modes. Consequently, even ab initio MP2 with the aug-cc-pVDZ and aug-cc-pVTZ basis sets has difficulty reproducing this anomaly, yielding qualitatively varied predictions of the sign of the VIE depending on such computational details as the choice of the embedding field. However, the temperature growth of the anomalous VIE is reproduced robustly and is ascribed to the librational modes. These solid-state MP2 calculations, as well as MP2 Born-Oppenheimer molecular dynamics, find a volume collapse and a loss of symmetry and long-range order in ice Ih upon pressure loading of 2.35 GPa or higher. Concomitantly, rapid softening of acoustic phonons is observed starting around 2 GPa. They constitute a computational detection of a mechanical instability in ice Ih and the resulting pressure-induced amorphization to HDA.

Ice Ih anomalies: Thermal contraction, anomalous volume isotope effect, and pressure-induced amorphization

NASA Astrophysics Data System (ADS)

Salim, Michael A.; Willow, Soohaeng Yoo; Hirata, So

2016-05-01

Ice Ih displays several anomalous thermodynamic properties such as thermal contraction at low temperatures, an anomalous volume isotope effect (VIE) rendering the volume of D2O ice greater than that of H2O ice, and a pressure-induced transition to the high-density amorphous (HDA) phase. Furthermore, the anomalous VIE increases with temperature, despite its quantum-mechanical origin. Here, embedded-fragment ab initio second-order many-body perturbation (MP2) theory in the quasiharmonic approximation (QHA) is applied to the Gibbs energy of an infinite, proton-disordered crystal of ice Ih at wide ranges of temperatures and pressures. The quantum effect of nuclei moving in anharmonic potentials is taken into account from first principles without any empirical or nonsystematic approximation to either the electronic or vibrational Hamiltonian. MP2 predicts quantitatively correctly the thermal contraction at low temperatures, which is confirmed to originate from the volume-contracting hydrogen-bond bending modes (acoustic phonons). It qualitatively reproduces (but underestimates) the thermal expansion at higher temperatures, caused by the volume-expanding hydrogen-bond stretching (and to a lesser extent librational) modes. The anomalous VIE is found to be the result of subtle cancellations among closely competing isotope effects on volume from all modes. Consequently, even ab initio MP2 with the aug-cc-pVDZ and aug-cc-pVTZ basis sets has difficulty reproducing this anomaly, yielding qualitatively varied predictions of the sign of the VIE depending on such computational details as the choice of the embedding field. However, the temperature growth of the anomalous VIE is reproduced robustly and is ascribed to the librational modes. These solid-state MP2 calculations, as well as MP2 Born-Oppenheimer molecular dynamics, find a volume collapse and a loss of symmetry and long-range order in ice Ih upon pressure loading of 2.35 GPa or higher. Concomitantly, rapid softening of acoustic phonons is observed starting around 2 GPa. They constitute a computational detection of a mechanical instability in ice Ih and the resulting pressure-induced amorphization to HDA.

Ice Ih anomalies: Thermal contraction, anomalous volume isotope effect, and pressure-induced amorphization

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

Salim, Michael A.; Willow, Soohaeng Yoo; Hirata, So, E-mail: sohirata@illinois.edu

Ice Ih displays several anomalous thermodynamic properties such as thermal contraction at low temperatures, an anomalous volume isotope effect (VIE) rendering the volume of D{sub 2}O ice greater than that of H{sub 2}O ice, and a pressure-induced transition to the high-density amorphous (HDA) phase. Furthermore, the anomalous VIE increases with temperature, despite its quantum-mechanical origin. Here, embedded-fragment ab initio second-order many-body perturbation (MP2) theory in the quasiharmonic approximation (QHA) is applied to the Gibbs energy of an infinite, proton-disordered crystal of ice Ih at wide ranges of temperatures and pressures. The quantum effect of nuclei moving in anharmonic potentials ismore » taken into account from first principles without any empirical or nonsystematic approximation to either the electronic or vibrational Hamiltonian. MP2 predicts quantitatively correctly the thermal contraction at low temperatures, which is confirmed to originate from the volume-contracting hydrogen-bond bending modes (acoustic phonons). It qualitatively reproduces (but underestimates) the thermal expansion at higher temperatures, caused by the volume-expanding hydrogen-bond stretching (and to a lesser extent librational) modes. The anomalous VIE is found to be the result of subtle cancellations among closely competing isotope effects on volume from all modes. Consequently, even ab initio MP2 with the aug-cc-pVDZ and aug-cc-pVTZ basis sets has difficulty reproducing this anomaly, yielding qualitatively varied predictions of the sign of the VIE depending on such computational details as the choice of the embedding field. However, the temperature growth of the anomalous VIE is reproduced robustly and is ascribed to the librational modes. These solid-state MP2 calculations, as well as MP2 Born–Oppenheimer molecular dynamics, find a volume collapse and a loss of symmetry and long-range order in ice Ih upon pressure loading of 2.35 GPa or higher. Concomitantly, rapid softening of acoustic phonons is observed starting around 2 GPa. They constitute a computational detection of a mechanical instability in ice Ih and the resulting pressure-induced amorphization to HDA.« less

Monte Carlo calculated correction factors for diodes and ion chambers in small photon fields.

PubMed

Czarnecki, D; Zink, K

2013-04-21

The application of small photon fields in modern radiotherapy requires the determination of total scatter factors Scp or field factors Ω(f(clin), f(msr))(Q(clin), Q(msr)) with high precision. Both quantities require the knowledge of the field-size-dependent and detector-dependent correction factor k(f(clin), f(msr))(Q(clin), Q(msr)). The aim of this study is the determination of the correction factor k(f(clin), f(msr))(Q(clin), Q(msr)) for different types of detectors in a clinical 6 MV photon beam of a Siemens KD linear accelerator. The EGSnrc Monte Carlo code was used to calculate the dose to water and the dose to different detectors to determine the field factor as well as the mentioned correction factor for different small square field sizes. Besides this, the mean water to air stopping power ratio as well as the ratio of the mean energy absorption coefficients for the relevant materials was calculated for different small field sizes. As the beam source, a Monte Carlo based model of a Siemens KD linear accelerator was used. The results show that in the case of ionization chambers the detector volume has the largest impact on the correction factor k(f(clin), f(msr))(Q(clin), Q(msr)); this perturbation may contribute up to 50% to the correction factor. Field-dependent changes in stopping-power ratios are negligible. The magnitude of k(f(clin), f(msr))(Q(clin), Q(msr)) is of the order of 1.2 at a field size of 1 × 1 cm(2) for the large volume ion chamber PTW31010 and is still in the range of 1.05-1.07 for the PinPoint chambers PTW31014 and PTW31016. For the diode detectors included in this study (PTW60016, PTW 60017), the correction factor deviates no more than 2% from unity in field sizes between 10 × 10 and 1 × 1 cm(2), but below this field size there is a steep decrease of k(f(clin), f(msr))(Q(clin), Q(msr)) below unity, i.e. a strong overestimation of dose. Besides the field size and detector dependence, the results reveal a clear dependence of the correction factor on the accelerator geometry for field sizes below 1 × 1 cm(2), i.e. on the beam spot size of the primary electrons hitting the target. This effect is especially pronounced for the ionization chambers. In conclusion, comparing all detectors, the unshielded diode PTW60017 is highly recommended for small field dosimetry, since its correction factor k(f(clin), f(msr))(Q(clin), Q(msr)) is closest to unity in small fields and mainly independent of the electron beam spot size.

Calculation of Derivative Thermodynamic Hydration and Aqueous Partial Molar Properties of Ions Based on Atomistic Simulations.

PubMed

Dahlgren, Björn; Reif, Maria M; Hünenberger, Philippe H; Hansen, Niels

2012-10-09

The raw ionic solvation free energies calculated on the basis of atomistic (explicit-solvent) simulations are extremely sensitive to the boundary conditions and treatment of electrostatic interactions used during these simulations. However, as shown recently [Kastenholz, M. A.; Hünenberger, P. H. J. Chem. Phys.2006, 124, 224501 and Reif, M. M.; Hünenberger, P. H. J. Chem. Phys.2011, 134, 144104], the application of an appropriate correction scheme allows for a conversion of the methodology-dependent raw data into methodology-independent results. In this work, methodology-independent derivative thermodynamic hydration and aqueous partial molar properties are calculated for the Na(+) and Cl(-) ions at P° = 1 bar and T(-) = 298.15 K, based on the SPC water model and on ion-solvent Lennard-Jones interaction coefficients previously reoptimized against experimental hydration free energies. The hydration parameters considered are the hydration free energy and enthalpy. The aqueous partial molar parameters considered are the partial molar entropy, volume, heat capacity, volume-compressibility, and volume-expansivity. Two alternative calculation methods are employed to access these properties. Method I relies on the difference in average volume and energy between two aqueous systems involving the same number of water molecules, either in the absence or in the presence of the ion, along with variations of these differences corresponding to finite pressure or/and temperature changes. Method II relies on the calculation of the hydration free energy of the ion, along with variations of this free energy corresponding to finite pressure or/and temperature changes. Both methods are used considering two distinct variants in the application of the correction scheme. In variant A, the raw values from the simulations are corrected after the application of finite difference in pressure or/and temperature, based on correction terms specifically designed for derivative parameters at P° and T(-). In variant B, these raw values are corrected prior to differentiation, based on corresponding correction terms appropriate for the different simulation pressures P and temperatures T. The results corresponding to the different calculation schemes show that, except for the hydration free energy itself, accurate methodological independence and quantitative agreement with even the most reliable experimental parameters (ion-pair properties) are not yet reached. Nevertheless, approximate internal consistency and qualitative agreement with experimental results can be achieved, but only when an appropriate correction scheme is applied, along with a careful consideration of standard-state issues. In this sense, the main merit of the present study is to set a clear framework for these types of calculations and to point toward directions for future improvements, with the ultimate goal of reaching a consistent and quantitative description of single-ion hydration thermodynamics in molecular dynamics simulations.

Principles, performance, and applications of spectral reconstitution (SR) in quantitative analysis of oils by Fourier transform infrared spectroscopy (FT-IR).

PubMed

García-González, Diego L; Sedman, Jacqueline; van de Voort, Frederik R

2013-04-01

Spectral reconstitution (SR) is a dilution technique developed to facilitate the rapid, automated, and quantitative analysis of viscous oil samples by Fourier transform infrared spectroscopy (FT-IR). This technique involves determining the dilution factor through measurement of an absorption band of a suitable spectral marker added to the diluent, and then spectrally removing the diluent from the sample and multiplying the resulting spectrum to compensate for the effect of dilution on the band intensities. The facsimile spectrum of the neat oil thus obtained can then be qualitatively or quantitatively analyzed for the parameter(s) of interest. The quantitative performance of the SR technique was examined with two transition-metal carbonyl complexes as spectral markers, chromium hexacarbonyl and methylcyclopentadienyl manganese tricarbonyl. The estimation of the volume fraction (VF) of the diluent in a model system, consisting of canola oil diluted to various extents with odorless mineral spirits, served as the basis for assessment of these markers. The relationship between the VF estimates and the true volume fraction (VF(t)) was found to be strongly dependent on the dilution ratio and also depended, to a lesser extent, on the spectral resolution. These dependences are attributable to the effect of changes in matrix polarity on the bandwidth of the ν(CO) marker bands. Excellent VF(t) estimates were obtained by making a polarity correction devised with a variance-spectrum-delineated correction equation. In the absence of such a correction, SR was shown to introduce only a minor and constant bias, provided that polarity differences among all the diluted samples analyzed were minimal. This bias can be built into the calibration of a quantitative FT-IR analytical method by subjecting appropriate calibration standards to the same SR procedure as the samples to be analyzed. The primary purpose of the SR technique is to simplify preparation of diluted samples such that only approximate proportions need to be adhered to, rather than using exact weights or volumes, the marker accounting for minor variations. Additional applications discussed include the use of the SR technique in extraction-based, quantitative, automated FT-IR methods for the determination of moisture, acid number, and base number in lubricating oils, as well as of moisture content in edible oils.

Atlas-based analysis of cardiac shape and function: correction of regional shape bias due to imaging protocol for population studies.

PubMed

Medrano-Gracia, Pau; Cowan, Brett R; Bluemke, David A; Finn, J Paul; Kadish, Alan H; Lee, Daniel C; Lima, Joao A C; Suinesiaputra, Avan; Young, Alistair A

2013-09-13

Cardiovascular imaging studies generate a wealth of data which is typically used only for individual study endpoints. By pooling data from multiple sources, quantitative comparisons can be made of regional wall motion abnormalities between different cohorts, enabling reuse of valuable data. Atlas-based analysis provides precise quantification of shape and motion differences between disease groups and normal subjects. However, subtle shape differences may arise due to differences in imaging protocol between studies. A mathematical model describing regional wall motion and shape was used to establish a coordinate system registered to the cardiac anatomy. The atlas was applied to data contributed to the Cardiac Atlas Project from two independent studies which used different imaging protocols: steady state free precession (SSFP) and gradient recalled echo (GRE) cardiovascular magnetic resonance (CMR). Shape bias due to imaging protocol was corrected using an atlas-based transformation which was generated from a set of 46 volunteers who were imaged with both protocols. Shape bias between GRE and SSFP was regionally variable, and was effectively removed using the atlas-based transformation. Global mass and volume bias was also corrected by this method. Regional shape differences between cohorts were more statistically significant after removing regional artifacts due to imaging protocol bias. Bias arising from imaging protocol can be both global and regional in nature, and is effectively corrected using an atlas-based transformation, enabling direct comparison of regional wall motion abnormalities between cohorts acquired in separate studies.

Three-dimensional mapping of equiprobable hydrostratigraphic units at the Frenchman Flat Corrective Action Unit, Nevada Test Site

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

Shirley, C.; Pohlmann, K.; Andricevic, R.

1996-09-01

Geological and geophysical data are used with the sequential indicator simulation algorithm of Gomez-Hernandez and Srivastava to produce multiple, equiprobable, three-dimensional maps of informal hydrostratigraphic units at the Frenchman Flat Corrective Action Unit, Nevada Test Site. The upper 50 percent of the Tertiary volcanic lithostratigraphic column comprises the study volume. Semivariograms are modeled from indicator-transformed geophysical tool signals. Each equiprobable study volume is subdivided into discrete classes using the ISIM3D implementation of the sequential indicator simulation algorithm. Hydraulic conductivity is assigned within each class using the sequential Gaussian simulation method of Deutsch and Journel. The resulting maps show the contiguitymore » of high and low hydraulic conductivity regions.« less

Correction for Delay and Dispersion Results in More Accurate Cerebral Blood Flow Ischemic Core Measurement in Acute Stroke.

PubMed

Lin, Longting; Bivard, Andrew; Kleinig, Timothy; Spratt, Neil J; Levi, Christopher R; Yang, Qing; Parsons, Mark W

2018-04-01

This study aimed to assess how the ischemic core measured by perfusion computed tomography (CTP) was affected by the delay and dispersion effect. Ischemic stroke patients having CTP performed within 6 hours of onset were included. The CTP data were processed twice, generating standard cerebral blood flow (sCBF) and delay- and dispersion-corrected CBF (ddCBF), respectively. Ischemic core measured by the sCBF and ddCBF was then compared at the relative threshold <30% of normal tissue. Two references for ischemic core were used: acute diffusion-weighted imaging or 24-hour diffusion-weighted imaging in patients with complete recanalization. Difference of core volume between CTP and diffusion-weighted imaging was estimated by Mann-Whitney U test and limits of agreement. Patients were also classified into favorable and unfavorable CTP patterns. The imaging pattern classification by sCBF and ddCBF was compared by the χ 2 test; their respective ability to predict good clinical outcome (3-month modified Rankin Scale score) was tested in logistic regression. Fifty-five patients were included in this study. Median sCBF ischemic core volume was 38.5 mL (12.4-61.9 mL), much larger than the median core volume of 17.2 mL measured by ddCBF (interquartile range, 5.5-38.8; P <0.001). Moreover, compared with sCBF <30%, ddCBF <30% measured the ischemic core much closer to diffusion-weighted imaging core references, with the mean volume difference of -0.1 mL (95% limits of agreement, -25.4 to 25.2; P =0.97) and 16.7 mL (95% limits of agreement, -21.7 to 55.2; P <0.001), respectively. Imaging patterns defined by sCBF showed a difference to that defined by ddCBF ( P <0.001), with 12 patients classified as favorable imaging patterns by ddCBF but as unfavorable by sCBF. The favorable imaging pattern classified by ddCBF, compared with sCBF classification, had higher predictive power for good clinical outcome (odds ratio, 7.8 [2-30.5] and 3.1 [0.9-11], respectively). Delay and dispersion correction increases the accuracy of ischemic core measurement on CTP. © 2018 American Heart Association, Inc.

Biofeedback defaecation training for anismus.

PubMed

Lestàr, B; Penninckx, F; Kerremans, R

1991-11-01

Anismus, paradoxical external sphincter function, spastic pelvic floor syndrome, rectoanal dysnergia, abdomino-levator incoordination for abdominopelvic asychronism, are all due to paradoxical contraction of the striated sphincter apparatus during voiding and is characterised by prolonged and excessive straining at stool. Biofeedback is the treatment of choice and has to be introduced at an early stage. We present the results of an ambulatory approach based on the integration of simulated balloon defaecation with small (50 ml) as well as constant rectal sensation volume, defaecometry and anal manometry. The pathophysiology visualised by the patient's own anorectal pressure recordings on the screen of a personal computer is explained and corrected. Sixteen patients were treated and followed for at least 1 year. Manometric data were normal except for an increased minimum residual pressure and rectal compliance. Nine patients could not evacuate a 50 ml bolus initially. Simulated defaecation became possible in seven out of these nine patients when the bolus was increased up to the individual constant rectal sensation volume. Two patients could not evacuate this volume either, while defaecation was made much less laborious in the other seven patients. Paradoxical contraction was immediately corrected in 7/16 cases. Also, as an immediate, objective benefit of a single training session, improved defaecation of a 50 ml bolus was observed in 11 patients. This effect was preserved after 6 weeks in nine cases; symptomatic recurrence did not occur in these patients during follow-up. This method of defaecation training has many advantages as compared with sphincter training using EMG electrodes eventually performed in the absence of a desire to defaecate or in lying position.(ABSTRACT TRUNCATED AT 250 WORDS)

Simulating Fiber Ordering and Aggregation In Shear Flow Using Dissipative Particle Dynamics

NASA Astrophysics Data System (ADS)

Stimatze, Justin T.

We have developed a mesoscale simulation of fiber aggregation in shear flow using LAMMPS and its implementation of dissipative particle dynamics. Understanding fiber aggregation in shear flow and flow-induced microstructural fiber networks is critical to our interest in high-performance composite materials. Dissipative particle dynamics enables the consideration of hydrodynamic interactions between fibers through the coarse-grained simulation of the matrix fluid. Correctly simulating hydrodynamic interactions and accounting for fluid forces on the microstructure is required to correctly model the shear-induced aggregation process. We are able to determine stresses, viscosity, and fiber forces while simulating the evolution of a model fiber system undergoing shear flow. Fiber-fiber contact interactions are approximated by combinations of common pairwise forces, allowing the exploration of interaction-influenced fiber behaviors such as aggregation and bundling. We are then able to quantify aggregate structure and effective volume fraction for a range of relevant system and fiber-fiber interaction parameters. Our simulations have demonstrated several aggregate types dependent on system parameters such as shear rate, short-range attractive forces, and a resistance to relative rotation while in contact. A resistance to relative rotation at fiber-fiber contact points has been found to strongly contribute to an increased angle between neighboring aggregated fibers and therefore an increase in average aggregate volume fraction. This increase in aggregate volume fraction is strongly correlated with a significant enhancement of system viscosity, leading us to hypothesize that controlling the resistance to relative rotation during manufacturing processes is important when optimizing for desired composite material characteristics.

Charged hadrons in local finite-volume QED+QCD with C⋆ boundary conditions

NASA Astrophysics Data System (ADS)

Lucini, B.; Patella, A.; Ramos, A.; Tantalo, N.

2016-02-01

In order to calculate QED corrections to hadronic physical quantities by means of lattice simulations, a coherent description of electrically-charged states in finite volume is needed. In the usual periodic setup, Gauss's law and large gauge transformations forbid the propagation of electrically-charged states. A possible solution to this problem, which does not violate the axioms of local quantum field theory, has been proposed by Wiese and Polley, and is based on the use of C⋆ boundary conditions. We present a thorough analysis of the properties and symmetries of QED in isolation and QED coupled to QCD, with C⋆ boundary conditions. In particular we learn that a certain class of electrically-charged states can be constructed in a fully consistent fashion without relying on gauge fixing and without peculiar complications. This class includes single particle states of most stable hadrons. We also calculate finite-volume corrections to the mass of stable charged particles and show that these are much smaller than in non-local formulations of QED.

Calibration of CT Hounsfield units for proton therapy treatment planning: use of kilovoltage and megavoltage images and comparison of parameterized methods

NASA Astrophysics Data System (ADS)

De Marzi, L.; Lesven, C.; Ferrand, R.; Sage, J.; Boulé, T.; Mazal, A.

2013-06-01

Proton beam range is of major concern, in particular, when images used for dose computations are artifacted (for example in patients with surgically treated bone tumors). We investigated several conditions and methods for determination of computed tomography Hounsfield unit (CT-HU) calibration curves, using two different conversion schemes. A stoichiometric methodology was used on either kilovoltage (kV) or megavoltage (MV) CT images and the accuracy of the calibration methods was evaluated. We then studied the effects of metal artifacts on proton dose distributions using metallic implants in rigid phantom mimicking clinical conditions. MV-CT images were used to evaluate relative proton stopping power in certain high density implants, and a methodology is proposed for accurate delineation and dose calculation, using a combined set of kV- and MV-CT images. Our results show good agreement between measurements and dose calculations or relative proton stopping power determination (<5%). The results also show that range uncertainty increases when only kV-CT images are used or when no correction is made on artifacted images. However, differences between treatment plans calculated on corrected kV-CT data and MV-CT data remained insignificant in the investigated patient case, even with streak artifacts and volume effects that reduce the accuracy of manual corrections.

Updated users' guide for TAWFIVE with multigrid

NASA Technical Reports Server (NTRS)

Melson, N. Duane; Streett, Craig L.

1989-01-01

A program for the Transonic Analysis of a Wing and Fuselage with Interacted Viscous Effects (TAWFIVE) was improved by the incorporation of multigrid and a method to specify lift coefficient rather than angle-of-attack. A finite volume full potential multigrid method is used to model the outer inviscid flow field. First order viscous effects are modeled by a 3-D integral boundary layer method. Both turbulent and laminar boundary layers are treated. Wake thickness effects are modeled using a 2-D strip method. A brief discussion of the engineering aspects of the program is given. The input, output, and use of the program are covered in detail. Sample results are given showing the effects of boundary layer corrections and the capability of the lift specification method.

Federal Logistics Information System (FLIS). Volume 18. Automated Mailing Labels System (AMLS) FLIS Procedures Manual

DTIC Science & Technology

1993-07-01

LPLPW3t TIME XXXX\\ LISI ADDRESSES AND DISIRIBUTION FOR XX XXXXXXXXXXXXXXXXXX\\ LSER ID XXX P %G[ ZZ.zz9 AA MLG MAILING ADDRESS ZIP CODE PI C x XNXX XX...4100.39-M Volume Is APPENDIX C AMLS INFORMATIONAL MESSAGES Corrective Action: Press the F6 ( COM MIT) function key to add the Distribution information

Efficient phase contrast imaging in STEM using a pixelated detector. Part 1: Experimental demonstration at atomic resolution

DOE PAGES

Pennycook, Timothy J.; Lupini, Andrew R.; Yang, Hao; ...

2014-10-15

In this paper, we demonstrate a method to achieve high efficiency phase contrast imaging in aberration corrected scanning transmission electron microscopy (STEM) with a pixelated detector. The pixelated detector is used to record the Ronchigram as a function of probe position which is then analyzed with ptychography. Ptychography has previously been used to provide super-resolution beyond the diffraction limit of the optics, alongside numerically correcting for spherical aberration. Here we rely on a hardware aberration corrector to eliminate aberrations, but use the pixelated detector data set to utilize the largest possible volume of Fourier space to create high efficiency phasemore » contrast images. The use of ptychography to diagnose the effects of chromatic aberration is also demonstrated. In conclusion, the four dimensional dataset is used to compare different bright field detector configurations from the same scan for a sample of bilayer graphene. Our method of high efficiency ptychography produces the clearest images, while annular bright field produces almost no contrast for an in-focus aberration-corrected probe.« less

A new plastic surgical technique for adult congenital webbed penis

PubMed Central

Chen, Yue-bing; Ding, Xian-fan; Luo, Chong; Yu, Shi-cheng; Yu, Yan-lan; Chen, Bi-de; Zhang, Zhi-gen; Li, Gong-hui

2012-01-01

Objective: To introduce a novel surgical technique for correction of adult congenital webbed penis. Methods: From March 2010 to December 2011, 12 patients (age range: 14–23 years old) were diagnosed as having a webbed penis and underwent a new surgical procedure designed by us. Results: All cases were treated successfully without severe complication. The operation time ranged from 20 min to 1 h. The average bleeding volume was less than 50 ml. All patients achieved satisfactory cosmetic results after surgery. The penile curvature disappeared in all cases and all patients remained well after 1 to 3 months of follow-up. Conclusions: Adult webbed penis with complaints of discomfort or psychological pressure due to a poor profile should be indicators for surgery. Good corrective surgery should expose the glans and coronal sulcus, match the penile skin length to the penile shaft length dorsally and ventrally, and provide a normal penoscrotal junction. Our new technique is a safe and effective method for the correction of adult webbed penis, which produces satisfactory results. PMID:22949367

Stereotactic radiosurgery planning of vestibular schwannomas: Is MRI at 3 Tesla geometrically accurate?

PubMed

Schmidt, M A; Wells, E J; Davison, K; Riddell, A M; Welsh, L; Saran, F

2017-02-01

MRI is a mandatory requirement to accurately plan Stereotactic Radiosurgery (SRS) for Vestibular Schwannomas. However, MRI may be distorted due not only to inhomogeneity of the static magnetic field and gradients but also due to susceptibility-induced effects, which are more prominent at higher magnetic fields. We assess geometrical distortions around air spaces and consider MRI protocol requirements for SRS planning at 3 T. Hardware-related distortion and the effect of incorrect shimming were investigated with structured test objects. The magnetic field was mapped over the head on five volunteers to assess susceptibility-related distortion in the naso-oro-pharyngeal cavities (NOPC) and around the internal ear canal (IAC). Hardware-related geometric displacements were found to be less than 0.45 mm within the head volume, after distortion correction. Shimming errors can lead to displacements of up to 4 mm, but errors of this magnitude are unlikely to arise in practice. Susceptibility-related field inhomogeneity was under 3.4 ppm, 2.8 ppm, and 2.7 ppm for the head, NOPC region and IAC region, respectively. For the SRS planning protocol (890 Hz/pixel, approximately 1 mm 3 isotropic), susceptibility-related displacements were less than 0.5 mm (head), and 0.4 mm (IAC and NOPC). Large displacements are possible in MRI examinations undertaken with lower receiver bandwidth values, commonly used in clinical MRI. Higher receiver bandwidth makes the protocol less vulnerable to sub-optimal shimming. The shimming volume and the CT-MR co-registration must be considered jointly. Geometric displacements can be kept under 1 mm in the vicinity of air spaces within the head at 3 T with appropriate setting of the receiver bandwidth, correct shimming and employing distortion correction. © 2017 The Authors. Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

Long-term effects of brief hypoxia due to cardiac arrest: Hippocampal reductions and memory deficits.

PubMed

Stamenova, Vess; Nicola, Raneen; Aharon-Peretz, Judith; Goldsher, Dorith; Kapeliovich, Michael; Gilboa, Asaf

2018-05-01

To examine the effects of brief hypoxia (<7 min) due to cardiac arrest on the integrity of the brain and performance on memory and executive functions tasks. Patients after out-of-hospital cardiac arrest (CA) (n = 9), who were deemed neurologically intact on discharge, were compared to matched patients with myocardial infarction (MI) (n = 9). A battery of clinical and experimental memory and executive functions neuropsychological tests were administered and MRI scans for all patients were collected. Measures of subcortical and cortical volumes and cortical thickness were obtained using FreeSurfer. Manual segmentations of the hippocampus were also performed. APACHE-II scores were calculated based on metrics collected at admission to ICCU for all patients. Significant differences between the two groups were observed on several verbal memory tests. Both hippocampi were significantly reduced (p < 0.05) in the CA patients, relative to MI patients. Hippocampal subfields segmentation showed significantly reduced presubiculum volumes bilaterally. CA patients had on average 10% reduction in volumes bilaterally across hippocampal subfields. No cortical thickness differences survived correction. Significant correlations were observed in the CA group only between the hippocampal volumes and performance on verbal memory tasks, including recollection. Hippocampal volumes and several memory measures (but not other cognitive domains) were strongly correlated with APACHE-II scores on admission in the CA group, but not in the MI group CONCLUSIONS: Chronic patients with cardiac arrest who were discharged from hospital in "good neurological condition" showed an average of 10% reduction in hippocampal volume bilaterally and significant verbal memory deficits relative to matched controls with myocardial infarction, suggesting even brief hypoxic periods suffice to lead to specific hippocampal damage. Copyright © 2018 Elsevier B.V. All rights reserved.

Cannabis use and brain structural alterations of the cingulate cortex in early psychosis.

PubMed

Rapp, Charlotte; Walter, Anna; Studerus, Erich; Bugra, Hilal; Tamagni, Corinne; Röthlisberger, Michel; Borgwardt, Stefan; Aston, Jacqueline; Riecher-Rössler, Anita

2013-11-30

As cannabis use is more frequent in patients with psychosis than in the general population and is known to be a risk factor for psychosis, the question arises whether cannabis contributes to recently detected brain volume reductions in schizophrenic psychoses. This study is the first to investigate how cannabis use is related to the cingulum volume, a brain region involved in the pathogenesis of schizophrenia, in a sample of both at-risk mental state (ARMS) and first episode psychosis (FEP) subjects. A cross-sectional magnetic resonance imaging (MRI) study of manually traced cingulum in 23 FEP and 37 ARMS subjects was performed. Cannabis use was assessed with the Basel Interview for Psychosis. By using repeated measures analyses of covariance, we investigated whether current cannabis use is associated with the cingulum volume, correcting for age, gender, alcohol consumption, whole brain volume and antipsychotic medication. There was a significant three-way interaction between region (anterior/posterior cingulum), hemisphere (left/right cingulum) and cannabis use (yes/no). Post-hoc analyses revealed that this was due to a significant negative effect of cannabis use on the volume of the posterior cingulum which was independent of the hemisphere and diagnostic group and all other covariates we controlled for. In the anterior cingulum, we found a significant negative effect only for the left hemisphere, which was again independent of the diagnostic group. Overall, we found negative associations of current cannabis use with grey matter volume of the cingulate cortex, a region rich in cannabinoid CB1 receptors. As this finding has not been consistently found in healthy controls, it might suggest that both ARMS and FEP subjects are particularly sensitive to exogenous activation of these receptors. © 2013 Elsevier Ireland Ltd. All rights reserved.

Multi-atlas attenuation correction supports full quantification of static and dynamic brain PET data in PET-MR

NASA Astrophysics Data System (ADS)

Mérida, Inés; Reilhac, Anthonin; Redouté, Jérôme; Heckemann, Rolf A.; Costes, Nicolas; Hammers, Alexander

2017-04-01

In simultaneous PET-MR, attenuation maps are not directly available. Essential for absolute radioactivity quantification, they need to be derived from MR or PET data to correct for gamma photon attenuation by the imaged object. We evaluate a multi-atlas attenuation correction method for brain imaging (MaxProb) on static [18F]FDG PET and, for the first time, on dynamic PET, using the serotoninergic tracer [18F]MPPF. A database of 40 MR/CT image pairs (atlases) was used. The MaxProb method synthesises subject-specific pseudo-CTs by registering each atlas to the target subject space. Atlas CT intensities are then fused via label propagation and majority voting. Here, we compared these pseudo-CTs with the real CTs in a leave-one-out design, contrasting the MaxProb approach with a simplified single-atlas method (SingleAtlas). We evaluated the impact of pseudo-CT accuracy on reconstructed PET images, compared to PET data reconstructed with real CT, at the regional and voxel levels for the following: radioactivity images; time-activity curves; and kinetic parameters (non-displaceable binding potential, BPND). On static [18F]FDG, the mean bias for MaxProb ranged between 0 and 1% for 73 out of 84 regions assessed, and exceptionally peaked at 2.5% for only one region. Statistical parametric map analysis of MaxProb-corrected PET data showed significant differences in less than 0.02% of the brain volume, whereas SingleAtlas-corrected data showed significant differences in 20% of the brain volume. On dynamic [18F]MPPF, most regional errors on BPND ranged from -1 to  +3% (maximum bias 5%) for the MaxProb method. With SingleAtlas, errors were larger and had higher variability in most regions. PET quantification bias increased over the duration of the dynamic scan for SingleAtlas, but not for MaxProb. We show that this effect is due to the interaction of the spatial tracer-distribution heterogeneity variation over time with the degree of accuracy of the attenuation maps. This work demonstrates that inaccuracies in attenuation maps can induce bias in dynamic brain PET studies. Multi-atlas attenuation correction with MaxProb enables quantification on hybrid PET-MR scanners, eschewing the need for CT.

Multi-atlas attenuation correction supports full quantification of static and dynamic brain PET data in PET-MR.

PubMed

Mérida, Inés; Reilhac, Anthonin; Redouté, Jérôme; Heckemann, Rolf A; Costes, Nicolas; Hammers, Alexander

2017-04-07

In simultaneous PET-MR, attenuation maps are not directly available. Essential for absolute radioactivity quantification, they need to be derived from MR or PET data to correct for gamma photon attenuation by the imaged object. We evaluate a multi-atlas attenuation correction method for brain imaging (MaxProb) on static [ 18 F]FDG PET and, for the first time, on dynamic PET, using the serotoninergic tracer [ 18 F]MPPF. A database of 40 MR/CT image pairs (atlases) was used. The MaxProb method synthesises subject-specific pseudo-CTs by registering each atlas to the target subject space. Atlas CT intensities are then fused via label propagation and majority voting. Here, we compared these pseudo-CTs with the real CTs in a leave-one-out design, contrasting the MaxProb approach with a simplified single-atlas method (SingleAtlas). We evaluated the impact of pseudo-CT accuracy on reconstructed PET images, compared to PET data reconstructed with real CT, at the regional and voxel levels for the following: radioactivity images; time-activity curves; and kinetic parameters (non-displaceable binding potential, BP ND ). On static [ 18 F]FDG, the mean bias for MaxProb ranged between 0 and 1% for 73 out of 84 regions assessed, and exceptionally peaked at 2.5% for only one region. Statistical parametric map analysis of MaxProb-corrected PET data showed significant differences in less than 0.02% of the brain volume, whereas SingleAtlas-corrected data showed significant differences in 20% of the brain volume. On dynamic [ 18 F]MPPF, most regional errors on BP ND ranged from -1 to  +3% (maximum bias 5%) for the MaxProb method. With SingleAtlas, errors were larger and had higher variability in most regions. PET quantification bias increased over the duration of the dynamic scan for SingleAtlas, but not for MaxProb. We show that this effect is due to the interaction of the spatial tracer-distribution heterogeneity variation over time with the degree of accuracy of the attenuation maps. This work demonstrates that inaccuracies in attenuation maps can induce bias in dynamic brain PET studies. Multi-atlas attenuation correction with MaxProb enables quantification on hybrid PET-MR scanners, eschewing the need for CT.

Revisiting Tectonic Corrections Applied to Pleistocene Sea-Level Highstands

NASA Astrophysics Data System (ADS)

Creveling, J. R.; Mitrovica, J. X.; Hay, C.; Austermann, J.; Kopp, R. E.

2015-12-01

The robustness of stratigraphic- and geomorphic-based inferences of Quaternary peak interglacial sea levels — and equivalent minimum continental ice volumes — depends on the accuracy with which highstand markers can be corrected for vertical tectonic displacement. For sites that preserve a Marine Isotope Stage (MIS) 5e sea-level highstand marker, the customary method for estimating tectonic uplift/subsidence rate computes the difference between the local elevation of the highstand marker and a reference eustatic (i.e., global mean) MIS 5e sea-level height, typically assumed to be +6 m, and then divides this height difference by the age of the highstand marker. This rate is then applied to correct the elevation of other observed sea-level markers at that site for tectonic displacement. Subtracting a reference eustatic value from a local MIS 5e highstand marker elevation introduces two potentially significant errors. First, the commonly adopted peak eustatic MIS 5e sea-level value (i.e., +6 m) is likely too low; recent studies concluded that MIS 5e peak eustatic sea level was ~6-9 m. Second, local peak MIS 5e sea level was not globally uniform, but instead characterized by significant departures from eustasy due to glacial isostatic adjustment (GIA) in response to successive glacial-interglacial cycles and excess polar ice-sheet melt relative to present day. We present numerical models of GIA that incorporate both of these effects in order to quantify the plausible range in error of previous tectonic corrections. We demonstrate that, even far from melting ice sheets, local peak MIS 5e sea level may have departed from eustasy by 2-4 m, or more. Thus, adopting an assumed reference eustatic value to estimate tectonic displacement, rather than a site-specific GIA signal, can introduce significant error in estimates of peak eustatic sea level (and minimum ice volumes) during Quaternary highstands (e.g., MIS 11, MIS 5c and MIS 5a).

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

Lessard, Francois; Archambault, Louis; Plamondon, Mathieu

Purpose: Photon dosimetry in the kilovolt (kV) energy range represents a major challenge for diagnostic and interventional radiology and superficial therapy. Plastic scintillation detectors (PSDs) are potentially good candidates for this task. This study proposes a simple way to obtain accurate correction factors to compensate for the response of PSDs to photon energies between 80 and 150 kVp. The performance of PSDs is also investigated to determine their potential usefulness in the diagnostic energy range. Methods: A 1-mm-diameter, 10-mm-long PSD was irradiated by a Therapax SXT 150 unit using five different beam qualities made of tube potentials ranging from 80more » to 150 kVp and filtration thickness ranging from 0.8 to 0.2 mmAl + 1.0 mmCu. The light emitted by the detector was collected using an 8-m-long optical fiber and a polychromatic photodiode, which converted the scintillation photons to an electrical current. The PSD response was compared with the reference free air dose rate measured with a calibrated Farmer NE2571 ionization chamber. PSD measurements were corrected using spectra-weighted corrections, accounting for mass energy-absorption coefficient differences between the sensitive volumes of the ionization chamber and the PSD, as suggested by large cavity theory (LCT). Beam spectra were obtained from x-ray simulation software and validated experimentally using a CdTe spectrometer. Correction factors were also obtained using Monte Carlo (MC) simulations. Percent depth dose (PDD) measurements were compensated for beam hardening using the LCT correction method. These PDD measurements were compared with uncorrected PSD data, PDD measurements obtained using Gafchromic films, Monte Carlo simulations, and previous data. Results: For each beam quality used, the authors observed an increase of the energy response with effective energy when no correction was applied to the PSD response. Using the LCT correction, the PSD response was almost energy independent, with a residual 2.1% coefficient of variation (COV) over the 80-150-kVp energy range. Monte Carlo corrections reduced the COV to 1.4% over this energy range. All PDD measurements were in good agreement with one another except for the uncorrected PSD data, in which an over-response was observed with depth (13% at 10 cm with a 100 kVp beam), showing that beam hardening had a non-negligible effect on the PSD response. A correction based on LCT compensated very well for this effect, reducing the over-response to 3%.Conclusion: In the diagnostic energy range, PSDs show high-energy dependence, which can be corrected using spectra-weighted mass energy-absorption coefficients, showing no considerable sign of quenching between these energies. Correction factors obtained by Monte Carlo simulations confirm that the approximations made by LCT corrections are valid. Thus, PSDs could be useful for real-time dosimetry in radiology applications.« less

Corrections. Focal Point: Research, Policy, and Practice in Children's Mental Health. Volume 20, Number 2, Summer 2006

ERIC Educational Resources Information Center

Walker, Janet S., Ed.

2006-01-01

This issue of "Focal Point" describes the need for, and provides examples of, new strategies for meeting the mental health needs of children and adolescents involved with the juvenile justice system. Articles in this issue discuss the particular need for correction in the way that the juvenile justice system interacts with youth who have mental…

The unbiasedness of a generalized mirage boundary correction method for Monte Carlo integration estimators of volume

Treesearch

Thomas B. Lynch; Jeffrey H. Gove

2014-01-01

The typical "double counting" application of the mirage method of boundary correction cannot be applied to sampling systems such as critical height sampling (CHS) that are based on a Monte Carlo sample of a tree (or debris) attribute because the critical height (or other random attribute) sampled from a mirage point is generally not equal to the critical...

Real Time System for Practical Acoustic Monitoring of Global Ocean Temperature. Volume 3

DTIC Science & Technology

1994-06-30

signal processing software to the SSAR. This software performs Doppler correction , circulating sums, matched filtering and pulse compression, estimation...Doppler correction , circulating sums, matched filtering and pulse compression, estimation of multipath arrival angle, and peak- picking. At the... geometrica , sound speed, and focuing region sAles to the acoustic wavelengths Our work on this problem is based on an oceanographic application. To

Anatomical Basis for Safe and Effective Volumization of the Temple.

PubMed

Breithaupt, Andrew D; Jones, Derek H; Braz, Andre; Narins, Rhoda; Weinkle, Susan

2015-12-01

One of the earliest but often unaddressed signs of facial aging is volume loss in the temple. Treatment of the area can produce satisfying results for both patient and practitioner. Safe injection requires explicit knowledge of the anatomy to avoid complications related to the multitude of vessels that course throughout the region at various depths. The authors aim to detail the anatomy of the area and provide a safe and easy-to-follow method for injection. The authors review the relevant anatomy of the temporal region and its application to cosmetic filler injections. The authors describe an easy-to-follow approach for a safe and effective injection window based on numerous anatomical studies. Injection in this area is not without risk, including potential blindness. The authors review the potential complications and their treatments. Hollowing of the temple is an early sign of aging that, when corrected, can lead to significant patient and practitioner satisfaction. Proper anatomically knowledge is required to avoid potentially severe complications. In this study, the authors present a reliable technique to safely and effectively augment this often undertreated area of the aging face.

Systematic evaluation of three different commercial software solutions for automatic segmentation for adaptive therapy in head-and-neck, prostate and pleural cancer.

PubMed

La Macchia, Mariangela; Fellin, Francesco; Amichetti, Maurizio; Cianchetti, Marco; Gianolini, Stefano; Paola, Vitali; Lomax, Antony J; Widesott, Lamberto

2012-09-18

To validate, in the context of adaptive radiotherapy, three commercial software solutions for atlas-based segmentation. Fifteen patients, five for each group, with cancer of the Head&Neck, pleura, and prostate were enrolled in the study. In addition to the treatment planning CT (pCT) images, one replanning CT (rCT) image set was acquired for each patient during the RT course. Three experienced physicians outlined on the pCT and rCT all the volumes of interest (VOIs). We used three software solutions (VelocityAI 2.6.2 (V), MIM 5.1.1 (M) by MIMVista and ABAS 2.0 (A) by CMS-Elekta) to generate the automatic contouring on the repeated CT. All the VOIs obtained with automatic contouring (AC) were successively corrected manually. We recorded the time needed for: 1) ex novo ROIs definition on rCT; 2) generation of AC by the three software solutions; 3) manual correction of AC.To compare the quality of the volumes obtained automatically by the software and manually corrected with those drawn from scratch on rCT, we used the following indexes: overlap coefficient (DICE), sensitivity, inclusiveness index, difference in volume, and displacement differences on three axes (x, y, z) from the isocenter. The time saved by the three software solutions for all the sites, compared to the manual contouring from scratch, is statistically significant and similar for all the three software solutions. The time saved for each site are as follows: about an hour for Head&Neck, about 40 minutes for prostate, and about 20 minutes for mesothelioma. The best DICE similarity coefficient index was obtained with the manual correction for: A (contours for prostate), A and M (contours for H&N), and M (contours for mesothelioma). From a clinical point of view, the automated contouring workflow was shown to be significantly shorter than the manual contouring process, even though manual correction of the VOIs is always needed.