Uncorrected Data Research Articles

Influence of long-term CO2 storage on δ13C in vials capped with butyl and butyl/PTFE caps and the relevance for ecological samples

The carbon (C) isotope signature of solid materials such as plants and soil, or gaseous samples (atmospheric or soil air), can be used as a useful tool for investigations of the C cycle. In gaseous samples, stability of δ13C of carbon dioxide (CO2) in air during storage represents a problem. We tested the long-term storage effect of δ13C originated from CO2 in vials both capped with butyl or butyl coated with polytetrafluoroethylene (PTFE) on the internal surface. Therefore, pure CO2, depleted in 13C, was stored for up to 736 days. In addition, the relevance of long-term storage for ecological soil air data collected from a free-air CO2 enrichment (FACE) experiment located in Stuttgart (Germany) during one growing period with a maximum storage period of 210 days was judged. With increasing storage time, a change in isotopic composition towards less depleted δ13C was observed. The changes in δ13C were highest at the beginning of the storage period and decreased over time, which could be described with an asymptotic model. The maximum change in δ13C was less than 2 ‰ and lower for vials capped with butyl/PTFE septa. In the FACE experiment, the comparison between corrected and uncorrected data showed that δ13C originated from soil air changed within this data set by up to 1 ‰. The calculation of the fraction of plant derived C resulted in an underestimation of up to 10 %. The storage effect should be taken into consideration when interpreting δ13C values in order to avoid miscalculations.

Improving estimates of biomass change in buttressed trees using tree taper models

SummaryRepeat censuses of tree plots are key tools for investigating forest carbon fluxes. Current measurement procedures for trees with buttresses or trunk irregularities – trees that account for a large fraction of tropical forest biomass –introduce substantial systematic error in plot‐level estimates of biomass change. The diameters of buttressed trees are measured above the standard height of 1·3 m, and the measurement heights on individual trees are often moved upwards as buttresses grow. Because tree trunks taper (diameter decreases with height), biomass growth in buttressed individuals tends to be underestimated. Methods have been introduced to correct biomass growth estimates in individual trees for increases in measurement height; however, these methods change the distribution of effective measurement heights over time, introducing biases in plot‐level estimates of biomass change.In this study, we developed and applied new methods to measure and model trunk taper, and to use taper models to correct estimates ofAGBchange for changing measurement heights. We measured trunk taper above buttresses in 190 stems on Barro Colorado Island, Panama (BCI), a site where more than half of forest biomass is in trees measured above standard height. We compared proposed taper models to see which best described our measured taper data, then used the best taper model to correct for changing measurement heights in the historical plot data. Specifically, for all diameter measurements taken above 1·3 m, we calculated equivalent diameters at 1·3 m and substituted these into allometric equations to examine biomass change over time.We found that measured taper was best fit by an exponential model with a rate parameter that varied with measured diameter (tree size), height of measurement (buttress height) and species. Whereas uncorrected data show a decrease in biomass of 0·21% year−1between 1985 and 2010 onBCI, taper‐corrected data show an increase of 0·18% year−1.The novel correction method presented here converts all measured diameters to one standard effective measurement height. This corrects for biases at the plot level and provides a stronger foundation for measuring biomass change in tropical forests.

Application and evaluation of topographic correction methods to improve land cover mapping using object-based classification

This study applies and evaluates topographic correction methods to reduce radiometric variation due to topography characteristics in rugged terrain. The aim of this study was to improve the capability of satellite images to generate more reliable land cover mapping using object-based classification. Several semi-empirical correction methods, which require the estimation of empirically defined parameters, were selected for this study. Usually, these parameters are estimated relying on a previous land cover map. However, in this work the correction methods were applied considering the unavailability of a previous land cover map and the ease for implementation, so the main land cover type was used to estimate correction parameters to be applied to correct all land cover type. Landsat 5 TM image and topographic data derived from SRTM (Shuttle Radar Topography Mission) over an area located in an agricultural region of southeastern Brazil were used. Land cover classification was carried out using an object-based approach, which includes image segmentation and decision tree classification. The evaluation of topographic correction methods was based on: spectral characteristics expressed by standard deviation and mean values of spectral data within land cover classes; relationship between spectral data and solar illumination angle on the slope (cosi); object (segment) mean size; decision tree structure; visual analysis; and classification accuracy. Results show that the standard deviation of spectral data and the correlation between spectral values and cosi decreased after data correction, but not for all methods for some of the tested TM bands. The methods herein referred as Cosine, S1, Ad2S and SCS methods showed to increase the standard deviation and the correlation compared to the uncorrected data, mainly for bands 1, 2 and 3. Object mean size, in general, decreased after correction, except for C method. The effect on the object size showed to be related to a calculated standard deviation of adjacent pixels values. The decision tree structure given by the number of leaves also decreased after correction. The C, SCS+C and Minnaert methods showed the highest performance, followed by S2 and E-Stat, with a general accuracy increase around 10%. Land cover classification from uncorrected and corrected data differed in a large portion of the total studied area, with values around 29% for all correction methods.

Zircon growth in (U)HP quartzo-feldspathic host gneisses exhumed in the Woodlark Rift of Papua New Guinea

To understand zircon behavior as a function of bulk composition and metamorphic grade in the world's youngest (U)HP terrane, we report U-Pb SIMS spot-mode and depth-profiling analyses for quartzo-feldspathic gneisses. Zircons from two gneisses contain Cretaceous inherited cores, with μm sized metamorphic rims requiring depth profiling for reliable dating. Linear regression of the common-Pb uncorrected data for rims yield 206Pb/238U ages of 2.89 ± 0.29 Ma and 2.77 ± 0.99 Ma (concordia intercept ages at 95% confidence). The older age is within two-sigma error of previously reported 206Pb/238U ages on zircons from mafic eclogite within the gneiss, indicating that rims formed on inherited cores within host gneisses during eclogite facies metamorphism. At the (U)HP locality zircons from host gneiss lack inheritance and yield a 206Pb/238U age of 3.66 ± 0.13 Ma. These results are younger than previously reported 206Pb/238U ages on zircons from coesite eclogite within the gneiss, but are within error of the youngest reported LA-ICP-MS 206Pb/238U zircon ages on retrogressed mafic eclogite. We also report intragrain geochemical heterogeneity, indicated by zircon Hf, Y, and Ti variations in depth profiles which suggest chemical disequilibrium over the interval of zircon growth. Collectively, these results indicate that zircon recrystallization and new growth of zircon rims on relict grains occurred during eclogite facies metamorphism and during subsequent retrogression, but not at (U)HP conditions. Comparison between results from PNG and other (U)HP terranes bolsters previous suggestions that the PNG (U)HP terrane evolved rapidly.

Graph theoretical analysis of resting-state MEG data: Identifying interhemispheric connectivity and the default mode

Interhemispheric connectivity with resting state MEG has been elusive, and demonstration of the default mode network (DMN) yet more challenging. Recent seed-based MEG analyses have shown interhemispheric connectivity using power envelope correlations. The purpose of this study is to compare graph theoretic maps of brain connectivity generated using MEG with and without signal leakage correction to evaluate for the presence of interhemispheric connectivity.Eight minutes of resting state eyes-open MEG data were obtained in 22 normal male subjects enrolled in an IRB-approved study (ages 16–18). Data were processed using an in-house automated MEG processing pipeline and projected into standard (MNI) source space at 7mm resolution using a scalar beamformer. Mean beta-band amplitude was sampled at 2.5second epochs from the source space time series. Leakage correction was performed in the time domain of the source space beam formed signal prior to amplitude transformation. Graph theoretic voxel-wise source space correlation connectivity analysis was performed for leakage corrected and uncorrected data. Degree maps were thresholded across subjects for the top 20% of connected nodes to identify hubs. Additional degree maps for sensory, visual, motor, and temporal regions were generated to identify interhemispheric connectivity using laterality indices. Hubs for the uncorrected MEG networks were predominantly symmetric and midline, bearing some resemblance to fMRI networks. These included the cingulate cortex, bilateral inferior frontal lobes, bilateral hippocampal formations and bilateral cerebellar hemispheres. These uncorrected networks however, demonstrated little to no interhemispheric connectivity using the ROI-based degree maps. Leakage corrected MEG data identified the DMN, with hubs in the posterior cingulate and biparietal areas. These corrected networks demonstrated robust interhemispheric connectivity for the ROI-based degree maps. Graph theoretic analysis of MEG resting state data without signal leakage correction can demonstrate symmetric networks with some resemblance to fMRI networks. These networks however, are an artifact of high local correlation from signal leakage and lack interhemispheric connectivity. Following signal leakage correction, MEG hubs emerge in the DMN, with strong interhemispheric connectivity.

MP32-10 BASELINE CORRECTION IN TESTOSTERONE BIOEQUIVALENCE STUDY

You have accessJournal of UrologySexual Function/Dysfunction/Andrology: Evaluation1 Apr 2014MP32-10 BASELINE CORRECTION IN TESTOSTERONE BIOEQUIVALENCE STUDY LaiMing Lee, SangAeh Park, Myong-Jin Kim, Chongwoo Yu, and Li Li LaiMing LeeLaiMing Lee More articles by this author , SangAeh ParkSangAeh Park More articles by this author , Myong-Jin KimMyong-Jin Kim More articles by this author , Chongwoo YuChongwoo Yu More articles by this author , and Li LiLi Li More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2014.02.940AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES For applicants seeking approval of a drug product, a bioequivalence (BE) study may be required if an application relies on FDA’s finding of safety and/or effectiveness for the reference listed drug (RLD). Testosterone (T), an anabolic steroid, is approved to treat men with hypogonadism. For approval of a T product, an endogenous substance drug product, the demonstration of BE against an RLD is complicated by endogenous T production. To rule out the influence of endogenous T, baseline T concentrations are subtracted from the total T concentrations for each subject after the drug product is administered. Pharmacokinetic and statistical analyses are performed on both uncorrected and corrected data as appropriate. Determination of BE between a test and RLD is based on the baseline-corrected T data. BE assessment may be complicated if an individual’s endogenous T concentrations change day-to-day or exhibit a circadian pattern. Currently, there are no consistent or data-driven approaches to assessing and reporting baseline T concentrations. The objectives of this study was to use FDA in-house data to assess baseline T characteristics and to determine the optimal baseline correction method for evaluation of BE of T products. METHODS FDA in-house data from T clinical trials (pivotal BE and phase 1 studies) were collected and analyzed for baseline T concentrations in hypogonadal men. We assessed the presence of a circadian rhythm in hypogonadal men and intra-subject variability of endogenous T between treatment periods. RESULTS A total of 266 hypogonadal men from 4 new drug applications submitted to FDA were analyzed. Data were obtained from 3 BE studies and 3 relative bioavailability studies. The age and body mass index in hypogonadal men ranged from 18 to 80 years and 15 to 35 kg/m2, respectively. Preliminary results show that, in general, baseline T concentrations in hypogonadal men fluctuated less than 100 ng/dL over a 12- to 24-hour period pre-treatment. Up to 200% intra-subject variability was seen when endogenous T concentration measurements were taken at the same time of the day with several days of separation (i.e., 108 versus 325 ng/dL taken at 10 am on Days 1 and 8). CONCLUSIONS Correction of baseline T concentration is needed for the assessment of BE of T products. Circadian rhythm is not significant in hypogonadal men compared to intra-subject variability. Therefore, the need to take extensive blood samples over 24 hours to characterize baseline T concentrations may not be necessary. However, due to the intra-subject variability, assessment of baseline T is needed before each treatment period. © 2014FiguresReferencesRelatedDetails Volume 191Issue 4SApril 2014Page: e334 Advertisement Copyright & Permissions© 2014MetricsAuthor Information LaiMing Lee More articles by this author SangAeh Park More articles by this author Myong-Jin Kim More articles by this author Chongwoo Yu More articles by this author Li Li More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

System wide analyses have underestimated protein abundances and the importance of transcription in mammals

Large scale surveys in mammalian tissue culture cells suggest that the protein expressed at the median abundance is present at 8,000–16,000 molecules per cell and that differences in mRNA expression between genes explain only 10–40% of the differences in protein levels. We find, however, that these surveys have significantly underestimated protein abundances and the relative importance of transcription. Using individual measurements for 61 housekeeping proteins to rescale whole proteome data from Schwanhausser et al. (2011), we find that the median protein detected is expressed at 170,000 molecules per cell and that our corrected protein abundance estimates show a higher correlation with mRNA abundances than do the uncorrected protein data. In addition, we estimated the impact of further errors in mRNA and protein abundances using direct experimental measurements of these errors. The resulting analysis suggests that mRNA levels explain at least 56% of the differences in protein abundance for the 4,212 genes detected by Schwanhausser et al. (2011), though because one major source of error could not be estimated the true percent contribution should be higher. We also employed a second, independent strategy to determine the contribution of mRNA levels to protein expression. We show that the variance in translation rates directly measured by ribosome profiling is only 12% of that inferred by Schwanhausser et al. (2011), and that the measured and inferred translation rates correlate poorly (R2 = 0.13). Based on this, our second strategy suggests that mRNA levels explain ∼81% of the variance in protein levels. We also determined the percent contributions of transcription, RNA degradation, translation and protein degradation to the variance in protein abundances using both of our strategies. While the magnitudes of the two estimates vary, they both suggest that transcription plays a more important role than the earlier studies implied and translation a much smaller role. Finally, the above estimates only apply to those genes whose mRNA and protein expression was detected. Based on a detailed analysis by Hebenstreit et al. (2012), we estimate that approximately 40% of genes in a given cell within a population express no mRNA. Since there can be no translation in the absence of mRNA, we argue that differences in translation rates can play no role in determining the expression levels for the ∼40% of genes that are non-expressed.

Retrieving water surface temperature from archive LANDSAT thermal infrared data: Application of the mono-channel atmospheric correction algorithm over two freshwater reservoirs

Water surface temperature is a key element in characterizing the thermodynamics of waterbodies, and for irregularly-shaped inland reservoirs, LANDSAT thermal infrared images are the best alternative yet for the retrieval of this parameter. However, images must be corrected mainly for atmospheric effects in order to be fully exploitable. The objective of this study is to validate the mono-channel correction algorithm for single-band thermal infrared LANDSAT data as put forward by Jiménez-Muñoz et al. (2009). Two freshwater reservoirs in continental France were selected as study sites, and best use was made of all accessible image and field data. Results obtained are satisfactory and in accordance with the literature: r2 values are above 0.90 and root-mean-square error values are comprised between 1 and 2°C. Moreover, paired Wilcoxon signed rank tests showed a highly significant difference between field and uncorrected image data, a very highly significant difference between uncorrected and corrected image data, and no significant difference between field and corrected image data. The mono-channel algorithm is hence recommended for correcting archive LANDSAT single-band thermal infrared data for inland waterbody monitoring and study.

Dose calculation accuracy at presence of dental implants on UNCORRECTED and metal artifact reduced computed tomography data

Dose calculation accuracy at presence of dental implants on UNCORRECTED and metal artifact reduced computed tomography data

Mineralogical Characterization of Sieved and Un-Sieved Samples

Mineralogical characterization applied to mineral processing is now widespread. The first step for a mineralogi- cal characterization study is usually size fractionation. Preparation of polished sections is done on size fractions to reduce complications in making representative cross sections of particles with large size differences. A sample is commonly fractionated into five or six size intervals. The drawback of this procedure is that it makes liberation studies more expensive, because one sample actually produces five or six sub-samples that need to be studied, i.e. one from each size interval. Thus to reduce cost of liberation studies, it would be desirable to study the un-sized sample. This paper provides a comparative liberation study of a set of samples both using size fractions and using the un-sized samples. The samples studied are the feed, the concentrate and the tails of a lead rougher flotation circuit. The results consistently show significant differences between the sized and the un-sized samples. Nevertheless, the results indicate that un-corrected liberation data from un-sized samples can be used for comparative studies that involve several related samples. Thus, it is possible to improve (or further understand) a concentrator circuit by using mineralogical data from un-sized samples around such circuit.

Calibration of selected pyranometers and satellite derived solar radiation in Puerto Rico

Knowledge of solar radiation at the ground surface is valuable for many disciplines. In this study, ground-based sensors at Fortuna and Mayaguez, Puerto Rico, were used to calibrate daily-integrated satellite-derived solar radiation. The calibration equations yielded R 2 values of 0.88 and 0.83 at Fortuna and Mayaguez, respectively. A regression equation was also derived based on the combined data from the two locations with an R 2 of 0.87. The calibration equations for Fortuna and UPRM were validated using 283 and 227 days of solar radiation data from 2010, respectively. The combined data equation (intended as an island-wide equation) worked well at UPRM but not at Fortuna. We recommend, for locations other than the study areas, that the uncorrected remotely sensed data be used. At the study sites, the uncorrected data produced reasonably accurate results with a maximum 6.22% error between the mean estimated and measured solar radiation.

Correction of B0‐Distortions in Echo‐Planar‐Imaging–Based Perfusion‐Weighted MRI

To evaluate and quantify a scheme for correcting susceptibility artifacts in spin-echo echo-planar-imaging-based dynamic susceptibility contrast (DSC) perfusion MRI of high-grade gliomas at 3 Tesla. Sixteen patients with a total of 78 scans were studied. DSC-MRI images were corrected using a displacement map generated from opposite phase-encoding polarity images. Two methods were used for quantification in the correction: (i) linear regression of pixel-by-pixel comparisons, performed both globally and relative to the anterior and posterior commissure plane (AC-PC plane), of T2-weighted images with both corrected and uncorrected raw DSC images; and (ii) counting significant (>2.0) normalized cerebral blood volume (nCBV) pixels from perfusion maps in the tumor region of interest. Sixty-four of 78 datasets showed significant differences in the coefficient of correlation (r2) values. The difference between corrected and uncorrected r2 values was positive in all but one patient. Correction of B0- distortion significantly improved r2 in slices around the AC-PC plane. In 62% of the datasets, we observed an increased number of significant pixels in the corrected nCBV maps; 36% showed more significant pixels in uncorrected nCBV maps; 1% showed no difference. Distortion correction of DSC-MRI may provide improved accuracy compared with uncorrected data, especially for tumors located below the corpus callosum and near the frontal sinuses.

Impact of partial volume effect correction on cerebral β-amyloid imaging in APP-Swe mice using [18F]-florbetaben PET

We previously investigated the progression of β-amyloid deposition in brain of mice over-expressing amyloid-precursor protein (APP-Swe), a model of Alzheimer's disease (AD), in a longitudinal PET study with the novel β-amyloid tracer [18F]-florbetaben. There were certain discrepancies between PET and autoradiographic findings, which seemed to arise from partial volume effects (PVE). Since this phenomenon can lead to bias, most especially in the quantitation of brain microPET studies of mice, we aimed in the present study to investigate the magnitude of PVE on [18F]-florbetaben quantitation in murine brain, and to establish and validate a useful correction method (PVEC).Phantom studies with solutions of known radioactivity concentration were performed to measure the full-width-at-half-maximum (FWHM) resolution of the Siemens Inveon DPET and to validate a volume-of-interest (VOI)-based PVEC algorithm. Several VOI-brain-masks were applied to perform in vivo PVEC on [18F]-florbetaben data from C57BL/6(N=6) mice, while uncorrected and PVE-corrected data were cross-validated with gamma counting and autoradiography. Next, PVEC was performed on longitudinal PET data set consisting of 43 PET scans in APP-Swe (13–20months) and age-matched wild-type (WT) mice using the previously defined masks. VOI-based cortex-to-cerebellum ratios (SUVR) were compared for uncorrected and PVE-corrected results. Brains from a subset of transgenic mice were ultimately examined by autoradiography ex vivo and histochemistry in vitro as gold standard assessments, and compared to VOI-based PET results.The phantom study indicated a FWHM of 1.72mm. Applying a VOI-brain-mask including extracerebral regions gave robust PVEC, with increased precision of the SUVR results. Cortical SUVR increased with age in APP-Swe mice compared to baseline measurements (16months: +5.5%, p<0.005; 20months: +15.5%, p<0.05) with uncorrected data, and to a substantially greater extent with PVEC (16months: +12.2% p<0.005; 20months: +36.4% p<0.05). WT animals showed no binding changes, irrespective of PVEC. Relative to autoradiographic results, the error [%] for uncorrected cortical SUVR was 18.9% for native PET data, and declined to 4.8% upon PVEC, in high correlation with histochemistry results. We calculate that PVEC increases by 10% statistical power for detecting altered [18F]-florbetaben uptake in aging APP-Swe mice in planned studies of disease modifying treatments on amyloidogenesis.

Incorporating Geomechanical and Dynamic Hydraulic-Fracture-Property Changes Into Rate-Transient Analysis: Example From the Haynesville Shale

Summary It is well-known that many unconventional reservoirs experience porosity and permeability changes with pressure change during production. In recent work, authors have incorporated geomechanical modeling into production-analysis procedures to account for stress sensitivity of permeability of unconventional gas reservoirs, such as shale gas. Such corrections are necessary both for deriving accurate estimates of reservoir and hydraulic-fracture properties from rate-transient analysis (RTA) and for developing accurate long-term forecasts. It is possible with some shale-gas reservoirs that dynamic changes may occur in both the induced hydraulic fracture and matrix permeability, which could have a substantial impact on shale-gas productivity. The stress dependence of shale-gas permeability has been quantified in the laboratory by several researchers, but measurements of this kind for propped or unpropped fractures under in-situ conditions are less routinely acquired. For the latter, a variety of mechanisms, caused in part or wholly by stress changes in the induced hydraulic fracture, could lead to conductivity changes. In the current work, we investigate the impact of both stress-dependent matrix permeability and fracture-conductivity changes on rate-transient signatures and derived reservoir and hydraulic-fracture properties. Stress-dependent matrix permeability is incorporated into RTA by use of modified pseudopressure and pseudotime formulations, and fracture-conductivity changes are approximated by applying a time-dependent (dynamic) skin effect. We demonstrate that when RTA incorporates both matrix permeability changes and dynamic skin, the resulting rate-transient signature looks very similar to those of other shale plays (longterm transient linear flow). Uncorrected data appear to have a very short transient-linear-flow period, followed by apparent boundary-dominated flow. The impact of the applied corrections on the estimates of system permeability and fracture half-length is demonstrated, as is the impact on production forecasts.

Impacts of altimeter corrections on local linear sea level trends around Taiwan

Multi-mission altimeter measurements from TOPEX, Jason-1, and Jason-2 satellite altimetry over the 1993–2009 time span are used to characterize the local linear sea level trend (LSLT) around Taiwan. The results show that the long-term changes of default geophysical and range corrections, i.e. the inverted barometer correction, wet tropospheric correction, and sea state bias correction, have significant impacts on the determination of local LSLT. The trend of default corrections contribute more than 1.4 mm year−1 along the coastline of China mainland and 2.1 mm year−1 to local LSLT in the Taiwan Strait. The default-corrected altimetric data exhibit highest and lowest local LSLTs in the southeast and northwest of Taiwan, respectively. The regional LSLTs of 3.8 mm year−1 and 4.6 mm year−1 are estimated from the default-corrected and uncorrected altimetric data in the study area, respectively.

SU‐E‐I‐39: Experimental Study On the Performance of the OMAR CT Artifact Correction Algorithm Near Titanium and Stainless Steel

Purpose: Implants with high atomic numbers produce star‐like artifacts in CT‐images. When coupled in pairs, a black window appears in between. The Philips OMAR algorithm approaches these artifacts by post processing the images. In this study, measurements were performed with radiochromic EBT2 films in order to verify, whether the OMAR algorithm contributes to the accuracy of treatment plans in implant regions. Methods: Two sets of titanium and stainless steel rods with diameters of 1inch and 0.5inch were centered in a water phantom either single or in pairs. The phantom was scanned in a Philips Bigbore Brilliance scanner, which provides the OMAR correction algorithm. A set of uncorrected CT data was kept in addition to the post processed data. The treatment plans were calculated with AAA in Eclipse. The Hounsfield units in the volume of the metal rods were set to match the relative electron density with the conversion table extended accordingly. A 10×12 field at 90 degrees gantry rotation and 400MU was calculated using on a 1mm grid. The plans were irradiated using a Varian Novalis‐TX linac with EBT3 films placed on the sides of the single rod setup or between the rods in the two rod setups. The FilmQA Pro Software was used for evaluation of the films. Results: With one inhomogeneity present in the phantom, the difference between the plans based on the uncorrected data and the plans based on the post processed data is small. With paired inhomogeneities and the associated increased artifact, the difference becomes more significant and the OMAR algorithm improves the accuracy. High Z scattering effects cause considerable deviation from the planned dose profiles near the rods. Conclusion: The OMAR‐algorithm improves the accuracy of the dose calculations. The dose profiles across implant regions are calculated accurately, if the Hounsfield units are defined accordingly.

WE‐C‐116‐03: Spectral Parameter Estimation in the Presence of Macroscopic B0 Variations Using Fast Chemical Shift Imaging

Purpose: To assess the ability to correct for macroscopic B0 variations to obtain accurate estimates of T2* and amplitude in voxels containing multiple chemical species. Methods: A solid lipid/water phantom was constructed by adding 1.5% (w/v) agarose and 1.4% (w/v) lecithin to a mixture containing equal parts water and lard by volume. The phantom was imaged using fast multi‐echo GRE sequence (TEmin=3.8ms, ΔTE=2 ms, 10 echoes) while a linear gradient was applied in the slice direction at six linearly spaced values ranging from 32 to 200 μT/m. The decay of the complex data was corrected assuming an ideal (boxcar) slice profile and Gaussian slice profile estimated from phantom measurement. At each gradient strength, the T2* and amplitude of both chemical species was estimated using an autoregressive moving average (ARMA) model on the corrected and uncorrected data. Results: Before correction, the observed decrease in T2* over the range of gradient strengths was greater in water (ΔT2*=−37%) compared to fat (ΔT2*=−23%ms). The Gaussian slice profile assumption led to a better estimation of T2* (ΔT2*=−7% (water), +3%ms (fat) ) compared to the ideal slice profile assumption (ΔT2*=−18% (water); −9%ms (fat) ). Without any correction, the water fraction was overestimated by 2.8% compared to .7% and 1.1% for the Gaussian and boxcar slice profile assumptions, respectively. Conclusion: The method described in this work allows the T2* and amplitude of multiple chemical species to be corrected for the effects of linear B0 variations in the slice direction. In general, B0 variations have a greater effect on water T2* than fat T2*. The Gaussian slice profile provides a more robust correction for both T2* and amplitude estimates. Future work will focus on investigating the sensitivity of this model over a range of spectral parameters. This research is supported in part by the MD Anderson Cancer Center Support Grant CA016672 and the National Center for Advancing Translational Sciences of the National Institutes of Health under Award Number TL1TR000369.

WE‐C‐108‐09: Patient‐Specific Monte Carlo Dosimetry for I–125 Prostate Brachytherapy

Purpose: To investigate dose distributions in the prostate and surrounding tissues for I–125 brachytherapy using Monte Carlo (MC) calculations with patient‐specific phantoms derived from CT images. We explore the effectiveness of different techniques to mitigate streaking artifacts due to brachytherapy sources in post‐implant CT images. Methods: Nine patients (45–87 sources) are considered. Streaking artifacts in post‐implant CT images are mitigated using various metallic artifact reduction (MAR) techniques: raw sinogram, fan beam virtual sinogram and 3D median filter. Segmented structures (CTV, rectum and bladder) guide the assignment of tissues (air, muscle, prostate, calcification, average tissue and bone) to develop patient‐specific MC phantoms. The EGSnrc user‐code Brachydose and GEANT4 user‐code ALGEBRA are employed for MC dose calculations using patient‐specific phantoms derived from CT images. Dose distributions generated with patient models derived using different MAR techniques and different calculation methods (MC, TG‐43) are compared directly, and using recommended dose metrics. Results: Application of each MAR technique to patient CT data results in comparable mitigation of streaking artifacts within the treatment volume in CT images. MC calculations based on uncorrected CT data Result in high dose spikes (&gt;200%) in the treatment volume and lower doses (40–70%) in surrounding tissues compared to MC calculations with corrected phantoms. Dose distributions within the prostate from MC simulations using phantoms generated with different MAR techniques are comparable to each other but differ from TG‐43 calculations with significant (10%+) local differences. Conclusion: Mitigation of streaking artifacts in CT images is necessary for patient‐specific MC dose calculations; however, dose distributions and clinical metrics in the target and OAR are insensitive to the particular MAR technique applied. Differences between MC and TG‐43 dose distributions within the target volume and surrounding organs for I‐125 prostate brachytherapy underline the importance of patient‐specific model‐based dose calculations for treatment planning and evaluation. NSERC, CCSRI, The Canada Research Chairs Program

Detection and correction of interference in SRM analysis

Selected Reaction Monitoring (SRM) is a method of choice for accurate quantitation of low-abundance proteins in complex backgrounds. This strategy is, however, sensitive to interference from other components in the sample that have the same precursor and fragment masses as the monitored transitions. We present here an approach to detect interference by using the expected relative intensity of SRM transitions. We also designed an algorithm to automatically detect the linear range of calibration curves. These approaches were applied to the experimental data of Clinical Proteomic Tumor Analysis Consortium (CPTAC) Verification Work Group Study 7 and show that the corrected measurements provide more accurate quantitation than the uncorrected data.

Measurement of the intrinsic attenuation of longitudinal waves in anisotropic material from uncorrected raw data

Among the physical parameters characterising the interaction of the ultrasonic beam with its supporting medium, ultrasonic attenuation is an important input parameter to simulate wave propagation and defect-beam phenomena. The measurement of the intrinsic attenuation in anisotropic material however is a difficult task. The paper presents an approach to determine intrinsic attenuation in anisotropic materials such as austenitic stainless steel welds and cladding. It deals with improvements on the initial device, based on measurements on two samples with different thicknesses (10mm and 20mm). A previous paper presented preliminary results with this new approach for isotropic materials.