bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐C‐WAB‐06: Deformable Registration of Post‐Implant MRI to Intra‐Operative Ultrasound Images for Permanent Prostate Brachytherapy Treatment Assessment
Authors: Le Y , Lee J , Robinson A , Song D
Published: July 2013

Purpose: Transrectal‐ultrasound (TRUS) is the most common image modality used in permanent prostate brachytherapy (PPI), while MRI images can provide additional anatomical information. Our goals were to develop a novel method to register post‐implant MRI to intra‐operative ultrasound (US) images and demonstrate its potential usage for retrospective implant assessment. Methods: TRUS images of prostate and non‐isocentric C‐arm fluoroscopy (FL) images are captured intraoperatively right after implant. The reconstructed 3D seed cloud from FL images (seeds_FL) will be used as a bridge to register post MRI to US images. The Registration of Ultrasound and Fluoroscopy (RUF) images is done by an intensity‐based point to volume algorithm. The day‐one post CT and T2‐MRI images are co‐registered and the 3D seed cloud is segmented from CT (seeds_CT). The iterative‐closest‐point algorithm is used to compute rigid transformation between seeds_FL and seed_CT. MRI can be transferred to FL coordinate using registration of two seed clouds and then to US coordinate using RUF registration. A thin‐plate‐spline algorithm is used to deform the MRI contours and images according to deformation of two seed clouds. To demonstrate this registration method, post MRI images from ten patients were registered to US images. The prostate contours were compared between post US and MRI. The planning needle interferences with critical structure like neurovascular bundles (NVB) were investigated. Results: After registration, center of mass of both prostate and urethra were within 3mm between two contour sets. The anterior boundaries of prostate were often overestimated in post US contours. When planning needles were superimposed over contours, there were about 3–4 needles passing through or in close vicinity of NVB in all patients. Conclusion: A novel method to register post‐implant MRI to intra‐operative US images was developed and demonstrated in evaluating accuracy of intra‐operative US contours and accessing needle passages to NVB during PPI.
SU‐C‐141‐01: Dose Impact in Lung Fibrosis Following Lung SBRT: Statistical Analysis and Geometric Interpretation
Authors: Yu V , Kishan A , Lee P , Low D , Ruan D
Published: July 2013

Purpose: To test the hypothesis that certain dosimetric parameters prognosticate treatment‐induced lung fibrosis. To obtain estimates for most prognostic dose values and to utilize them in developing new planning strategies to reduce injury in future SBRT. Methods: Follow‐up CT scans at 6 and 12 months were acquired from patients treated with SBRT (18Gy/Fx*3Fx or 12.5Gy/Fx*4Fx) for stage‐1 primary lung cancers or oligometastic lesions. Fibrosis regions were identified in these scans and propagated to the planning CT coordinates by rigidly registering the follow‐up and the planning CTs. Among a cohort of 8 properly registered cases, a bimodal behavior was repeatedly observed from the probability distribution for dose values within fibrosis regions. Based on a mixture‐Gaussian assumption, an Expectation‐Maximization (EM) algorithm was used to obtain characteristic parameters for such distribution. Geometric analysis was performed to interpret such parameters and infer the dose level that is potentially inductive of post‐SBRT fibrosis. Results: The Gaussian mixture obtained from the EM algorithm closely approximates the empirical dose histogram within the fibrosis volume with good consistency. The Kolmogorov‐Smirnov test yields a goodness of fit value 0.039. The higher Gaussian component, contributed by the dose received by PTV, was located around the prescription dose (50 or 54 Gy), as expected. Geometrical analysis suggests the mean of the lower Gaussian component as a possible indicator for a threshold dose that induces fibrosis after SBRT. Conclusion: Bimodal behavior was observed in the dose distribution of lung fibrosis volumes after SBRT. Novel statistical and geometrical analysis has shown that the systematically quantified low‐dose peak is a good indication of a threshold dose for injury. We seek to further improve the quality of registration to extend this analysis to a larger cohort for validation, and to explore planning strategies to reduce post‐SBRT injury by controlling the exposure above the threshold value.
SU‐C‐103‐04: 3D Tumor Tracking On Vero
Authors: Mao W , Kearney V , Jiang L , Yordy J , Solberg T
Published: July 2013

Purpose: The unique gimbal system of the BrainLAB Vero allows the treatment head to pivot in two dimensions for tumor tracking. In order to utilize this feature, it is crucial to directly monitor tumor motion during treatment. We present a 3D tumor motion monitoring method incorporating the orthogonal kV imaging subsystems on Vero. Methods: An anthropomorphic phantom was used in this study. A lung tumor and two BBs were driven in a regular 3D sine motion pattern using a programmable 4D motion platform. 4D CT scans were performed and the tumor was contoured at the end of inhale phase. Stereoscopic kV images were acquired at a rate of 5 fps. A spherical template was created to match the projections of BBs. Two sets of DRRs were created: one DRR set containing the tumor only and the other set containing the full anatomy without the tumor. They were combined to produce composite DRRs and their individual positions were optimized by comparing of the composite DRRs with acquired kV images. 3D tumor and BB positions were then determined from the results of stereo kV x‐rays. Results: Dual orthogonal kV images were acquired with the MV beam at gantry angles of 0 and 45 degrees. This produced approximately 640 images with corresponding kV imaging angles of ‐ 315, 45, 0, and 90 degrees. The tumor and the BBs were identified on every kV image. Both 2D and 3D positions were compared with the programmed positions. The maximum differences were 1 mm. Conclusion: The dual kV imaging systems on Vero, used in conjunction with our tumor tracking algorithm, are capable of marker or marker‐less lung tumor tracking. This technique may be applied to track tumors in real‐time to provide direct tumor motion information for compensation of tumor motion throughout the course of radiotherapy.
SU‐C‐103‐05: Automated Interstitial Brachytherapy Catheter Localization From Volumetric MR Data
Authors: Pernelle G , Kapur T , Mehrtash A , Penzkofer T , Damato A , Barber L , Schmidt E , Viswanathan A , Cormack R
Published: July 2013

Purpose: This work seeks to validate an automatic method for extracting interstitial catheter locations from volumetric MR data. Methods: A 3D b‐SSFP (balanced Steady State Free Precession) MRI sequence was used to enhance catheter detection, utilizing a controlled enlargement of size caused by magnetic susceptibility artifacts . Starting with a user‐provided needle‐tip location, the needle extraction algorithm searched the MR image for segments that maximized the “needle likelihood” and iteratively fit Bezier curves to these segments. To validate the geometry of extracted catheters, a phantom was constructed from transparent gel wax. An obturator was placed at the center of a transparent plastic container, and wax gel was melted and poured around it. A Syed‐Neblett template was then placed at one end of the obturator and 12 MR compatible catheters were inserted into the gel. The catheter trajectories extracted from the MR scan by the algorithm were compared to a CT scan. The algorithm was applied to patient scans under an IRB approved protocol. Results: The volumetric b‐SSFP sequence produced an artifact enhancement that enabled brachytherapy catheters to be distinguished from other signal voids. Comparison in a phantom of catheter locations extracted automatically from MR to those extracted manually from CT showed agreement of 3.5 mm Hausdorff Distance. When applied to patient scans, the presence of low signal regions between template and the target tumor required some manual intervention to ensure proper catheter extraction. Conclusion: An automatic algorithm for extracting interstitial catheter locations from MR scans has been developed. Using a b‐SSFP sequence allowed an iterative curve fitting algorithm to track MR artifacts from user provided tips to template. This algorithm should prove helpful to facilitate MR based treatment planning for interstitial brachytherapy. NIH P41 EB015898
SU‐C‐103‐06: Isocenter Calibration Concept and Feasibility for MR‐Guided Radiation Therapy (MRgRT)
Authors: Winter J , Carlone M , Westmore M , Breen S , Stanescu T , Dahan M , Jaffray D
Published: July 2013

Purpose: To describe and assess feasibility of a novel MR‐to‐Linac isocenter calibration tool for magnetic resonance guided radiotherapy (MRgRT™). Methods: The MRgRT system co‐developed by IMRIS and Varian employs a movable MR system, which travels into a Linac vault. To support MR‐based couch corrections based on MR‐to‐MR registration, we developed a software tool to calibrate the MR‐to‐Linac coordinate system transformation and apply it to MR images acquired for treatment guidance. To assess feasibility, we quantified repeatability of the movable MRI system at MR isocenter by securing an ACR phantom to a fixed IMRIS interventional table, and moving the MR system between the two adjacent rooms simulate normal function. We performed 18 cycles over two days in which we acquired 3D MRI datasets with 1 mm isotropic resolution. We assessed position variability by registering the MR volume for each cycle to the first volume, and tabulating transform parameters. Separately, we investigated if a calibrated position encoder on the magnet mover could minimize the z‐direction shift variability. Results: Greatest isocenter variability was observed in the z direction, with mean shift of 0.21 +/− 0.12 mm over both days. The greatest rotational variability was observed about the z‐axis, with mean rotation of 0.8 +/− 0.8 mrad over both days. Maximum shift was 0.51 mm in the z direction, and maximum rotation was 1.7 mrad about the z‐axis. In the separate repeatability experiment we found that the calibrated position encoder reduced the mean z‐shift variability from 0.59 +/− 0.35 mm to 0.17 +/− 0.13 mm. Conclusion: We showed that the movable MRI system provides a consistent within‐day and between‐day isocenter location, and z‐shift variability can be minimized with a position encoder. This work demonstrates the feasibility of using an MR‐to‐Linac isocenter calibration tool for the MRgRT system. Jeff Winter, Michael Westmore and Meir Dahan are all employees of IMRIS, the company co‐developing the MRgRT system. Funding for the MRgRT project at Princess Margaret Hospital was provided by the Canadian Foundation for Innovation.
SU‐C‐103‐07: Employing Compressed Sensing to Improve Tracking Image Quality of the MRI‐Guided Radiotherapy System
Authors: Du D , Green O Pechenaya , Feng Y , Mutic S , Parikh P , Olsen J , Hu Y
Published: July 2013

Purpose: To validate the feasibility of using compressed sensing to improve spatial resolution and image quality of motion tracking images for MRI guided radiotherapy system. Methods: This study was performed on a commercial low field 0.35T MRI‐guided radiotherapy system using the ACR phantom. The phantom was moved along the feet‐head direction 9 times to mimic motion with relative positions of 0cm, 5mm, 11mm, 15mm, 20mm, 17mm, 13mm, 8mm and 3mm, respectively. For each position, two images were acquired in the sagittal orientation using the standard TrueFISP sequence. One used the standard clinical protocol to acquire images with a spatial resolution of 3.5mm and a temporal resolution of 4 frames per second (FPS). The other was acquired with a higher spatial resolution (2.0mm) but at a lower temporal resolution (0.7 FPS). Compressed sensing (CS) was used to achieve 5.6‐fold acceleration and restore the temporal resolution of tracking images to 4 FPS. Images reconstructed using the CS technique were compared qualitatively to the standard technique as well as the low temporal, high spatial resolution images without utilizing the CS technique. Results: Image quality of the high spatial and high temporal resolution tracking images utilizing the CS technique was very close to the high spatial and low temporal resolution tracking images without utilizing the CS technique, and much better than the tracking images offered by the standard imaging protocol. Conclusion: Our results confirmed that the CS technique could accelerate the image acquisition speed nearly 6 times while maintaining similar image quality. Therefore, it could be used to significantly improve the spatial resolution of the low‐field MRI guided radiotherapy tracking images without sacrificing the temporal resolution.
SU‐C‐134‐01: CT Performance Assessment Using Statistical Processing Control Cloud‐Based Image Processing
Authors: Fredriksson J , Olafsdottir H , Levy J , Kristinsson S , Healy A , Dalbow G , Goodenough D , Pawlicki T
Published: July 2013

Purpose: Statistical Process Control is regularly used in industry to refine operations and improve quality. Historically the measurement of CT scanners has only been based on pass/fail criteria with minimal understanding of data fluctuations and implications of these fluctuations as possible early warning systems. We review different data sets in an effort to better understand how these tools can be used to establish tighter performance controls to better indicate potential system failures. Methods: We investigate effective energy, slice thickness, uniformity and resolution from data collected from weekly QA tests on one CT scanner (Site 2) over the course of one year. For comparison we use a previously collected set of 1565 scans from a ten year period during a quantitative imaging study (Site 1). The image data was processed with the ImageOwl CatphanQA software. Tolerances for CT imaging quality parameters were selected from IEC‐61223‐3‐5 and other sources. Process capability, Cp, describes the ratio of tolerance range to observed standard deviation. Cpk additionally weighs in closeness to one side of specification limits. For a Gaussian variable, process capability equal to 1 means 99.7% chance of correctly observing a single measurement within specification, i.e. 3 sigma. Results: Process capabilities are better than six sigma (Cp>2) for slice thickness measurements and sensitometry for Site 1, but not for uniformity. The greatest difference between sites were observed in sensitometric readings. The data from Site 1 showed a higher variability in slice thickness during the first year of operation, where it was discovered that the Field Of View (FOV) was often too large. This FOV check has been implemented as an automatic filter tool in the ImageOwl CatphanQA software. Conclusion: By monitoring modern CT scanners with today's test systems using commonly accepted control limits, reliable go/no‐go signals can be generated for most CT QA variables. ImageOwl sells the cloud‐based image QA software used in the study and pays the salary for some of the authors
SU‐C‐134‐07: Development and Validation of a Fast Volumetric Determination Method of Visceral Adipose Using CT Images
Authors: Yu Z , Parikh A , Klopp A , Cheung J , Court L
Published: July 2013

Purpose: To develop and validate a method for quick and accurate calculation of visceral adipose volume with minimal user interaction. The goal is to provide a tool that can be reliably used to analyze sizable patient databases. Methods: CT images are imported into in‐house software. Superior and inferior boundaries of the visceral region are defined by the user. Five ellipses, spaced equal distance apart between these boundaries, are then manually drawn on axial slices inside the rectus abdominis and transverse abdominis muscles to define the border between visceral and subcutaneous adipose. Ellipses are automatically interpolated to fill the rest of the region. A histogram of Hounsfield Units of all voxels within the visceral region is obtained. The threshold for adipose was defined to be the peak adipose value ±1.25 FWHM. The accuracy of the ellipse estimation method was validated by taking ten patient CT images, 5 obese and 5 lean, and comparing them with manually delineated rectus abdominis and transverse abdominis muscles. The accuracy of visceral fat measurement was validated using a CT scan of a physical phantom which was made using animal fat (to simulate human adipose) and other animal tissues. Results: The mean difference between manually delineated and ellipse‐based visceral adipose volumes for all ten patients was −1.3%. For nine out of ten patients, this difference was less than 5%. For the phantom measurements, our calculations using CT images differed from absolute fat volume by less than 10% for all scanning parameters. Accuracy of volume determination is inversely proportional to slice thickness and field‐of‐view, and not affected by kVp or mAs. Conclusion: We developed and validated a method to determine the total volume of visceral adipose based on CT imaging. The entire process takes on average 2 minutes per patient and will be useful for large population studies.
SU‐C‐116‐02: Volumetric Dose Deposition in the Breast Using Real‐Time Dosimetry
Authors: Nosratieh A , Burkett G , Boone J
Published: July 2013

Purpose: To empirically determine the angular dose distribution to a breast in a digital breast tomosythesis and mammography system using real‐time dosimetry technology. Methods: Three breast phantoms, constructed from polyethylene to simulate adipose tissue, were fabricated based on ninety cranio‐caudal mammography patients. The smallest (3.2 cm), average (5.1 cm), and largest (7.0 cm) breast thickness matched the measured breast shape using 13 mm polyethylene sheets. Technique factors, which matched the automatic settings in both tomo and mammo were used. Phantoms were designed to be modular allowing a dose probe to be placed in various heights and depths. A total of 390 signal trains, comprised of 15‐individual pulses (one for each angle) in tomo‐mode and a single pulse for mammo, were collected using a real‐time air ionization chamber (AccuGold, Radcal, Monrovia, CA). The signal train was integrated to generate a dose value at each location. This data was then used to generate a dynamic model of cumulative dose deposition as a function of x‐ray tube angle in tomo and mammo modes. Additionally, the effective linear attenuation coefficient for each energy was calculated. Using a look up table for the linear attenuation of polyethylene, the effective energy was calculated. Results: The dose deposition decreases from the compression paddle to the detector. Cumulative dose from tomo scan was comparable to that of mammo; differences in cumulative dose increased with phantom size. The effective energy for tomo at 28, 31 and 35 kVp with Al filter was calculated to be 19.7, 21.7 and 25 kV respectively. For mammo at 26, 29 (Rh filter) and 30 kV (Ag filter) was found to be19.1, 20.4 and 23.7 respectively. Conclusion: The volumetric dose deposition in Hologics dBT system shows angular dependence as a function of angle in tomo mode. NIH Grants
SU‐C‐116‐04: Development of a Comprehensive QC Protocol for Digital Breast Tomosynthesis (DBT)
Authors: Vecchio S , Brunner C , Taylor M , Williams M , Kaczmarek R , Chakrabarti K
Published: July 2013

Purpose: We define a general method for assessing imaging and dosimetric characteristics of tomosynthesis units that can be used under MQSA for acceptance and maintenance tests under 900.12 (e). Methods: Several QC tests have been selected as criteria for the evaluation, which are: geometric accuracy, flat‐field uniformity and noise, in‐plane resolution and slice sensitivity, consistency of AEC performance with varied thickness and glandularity and associated radiation dose. Both projection and reconstructed images were analyzed whenever possible. Several commercially available phantoms were used to evaluate these parameters. The acquisitions were performed on Hologic Selenia Dimension units in Combo mode and in a QC mode where all the tomo projections are acquired at zero‐degree position. Results: To our liking, the systems evaluated did not show any geometric distortion, and distance accuracy was found to be independent of object height above the breast support. Flood‐field illumination voxel value was less than 3% within the entire reconstructed volume. The FWHM of the Slice Sensitivity Profile of 1 mm Al beads is within (10 +/− 1) mm for any bead position and PMMA phantom thickness. The FWHM of the Line Spread Function of a 20 um tungsten wire is (180+/− 10) um and (230 +/−10) um in the two in‐plane directions, i.e. a degradation of the resolution along the direction of tube movement has been detected. Dose delivered in our AEC assessment, ranged from 1.2 mGy to 3.1 mGy. Automatic analysis of the contrast‐detail phantom images showed similar trends in both projection and reconstructed images. Conclusion: We have identified particular metrics that can serve as part of a quality assurance protocol under MQSA, and that can be evaluated with commercial phantoms. In order to fully characterize a DBT system, further measurements should still be required, such as ghost and lag measurements, or artifact evaluation.
SU‐E‐I‐18: Uncertainty Analysis of Pharmacokinetic Modeling in Dynamic Contrast‐Enhanced MRI Evaluated with MMID4 Simulation
Authors: Liu CY , Liao YP , Lin YS , Chin SC , Liu HL
Published: July 2013

Purpose: Uncertainty analysis including accuracy and precision evaluation is important for the pharmacokinetic modeling in dynamic contrast‐enhanced (DCE) MRI. Few studies had attempted to assess the precision of the commonly used modified Tofts and Kermode (mTK) and the adiabatic approximation to the tissue homogeneity (AATH) models using neutrally simulated data. The study aimed to investigate the precision of these two models using the time curves simulated by multiple path, multiple tracer, indicator dilution, 4 region (MMID4) model, and perform comparisons in patients with nasopharyngeal carcinoma (NPC). Methods: Tissue uptake curves were simulated using the MMID4 model, by adjusting input parameters including blood flow, capillary permeability surface area product, interstitial volume (Ve) and capillary plasma volume(Vp), using literature values representing breast tumor and meningioma. Four levels of Gaussian noise, corresponding to SNRs of 100, 50, 20 and 10, were added to the signal time curves, with 1000 iterations each. A literature‐based arterial input function was applied to the model. For NPC datasets, DCE‐MRI was performed at a 3T clinical scanner using a 3D‐SPGR sequence (TR/TE/FA=4.9ms/1.3ms/30degrees, 60 dynamics, sampling interval=3.9s). Results: Our simulation showed that the AATH provided better accuracy than the mTK model. From the results of the NPC patients, the AATH gave smaller transfer constant (Ktrans) and Ve, and larger Vp values, as compared to mTK model, which agreed with the simulation data. When comparing the coefficient of variance of common parameters by both models, the mTK resulted in superior precision than AATH, and greater CV was found with smaller SNR in all cases. Conclusion: Using the MMID4 model for data simulation, this work found that the AATH model resulted in more accurate but less precise estimates of physiological parameters as compared to the mTK model. Results from the analysis of clinical NPC data were consistent with the computer simulation.
SU‐E‐I‐30: Simulation of the Scatter Energy Spectrum for Multiple C‐Arm/patient Thickness Configurations Using MCNPX
Authors: Handley S , Pasciak A
Published: July 2013

Purpose: Lead‐free composite aprons consist of a mixture of relatively low atomic number materials with K shell absorption edges that have been selected to provide maximum X‐ray attenuation per unit mass of the apron for common x‐ray energy spectra encountered in fluoroscopy. The purpose of this study was to simulate and then analyze several factors that may influence the energy spectrum encountered by a physician near the fluoroscopy table. Methods: Dose curves were determined on a Siemens Artis Zee C‐arm system using varying thicknesses of PMMA. A model energy spectrum was generated using SPEKTR for patients of varying size based on the filtration and kVp described by the dose curves. The energy spectrum was imported into MCNPX v2.5.0 and a Monte Carlo simulation performed. Simulated geometries included both AP and lateral, with the physician standing on both the tube and detector side of the bed. Multiple flux tallies were created to generate an energy fluence histogram as a function of physician location for each fluoroscopy geometry. Plots of the energy spectrum were generated from the resultant MCNPX tallies. Results: The average energy of the scatter spectrum varied weakly as a function of C‐arm orientation and physician location relative to C‐arm isocenter. The average energy was the highest at a location of 40 cm inferior at the detector side for a lateral exam at 43.67 keV. The average energy was the lowest at 160 cm inferior on the source side for a lateral exam at 39.82 keV. Conclusion: The influence of physician location and C‐arm geometry on the scatter spectrum was, at its largest, 3.9 keV. The difference in energy was relatively small and provides a well‐defined target region for material‐composite aprons to optimally attenuate scattered photons.
SU‐E‐I‐32: A Comparison of Multi‐Detector CT Energy Spectrums for Use in Monte Carlo Simulations
Authors: Miller G , Ahmad S , Ruan C
Published: July 2013

Purpose: To compare two different methods of obtaining energy spectrums for use in Monte Carlo (MC) simulations of a multi‐detector CT (MDCT) scanner. Methods: The first set of CT energy spectrums were obtained by directly measuring the x‐ray tube output using an Amptek CdTe detector with a collimator. The CT x‐ray tube was fixed at the 12 o' clock position and the detector was placed on the patient table. The bowtie filters were removed from the path of the beam, and the tube current was set to 10 mA, the lowest possible setting, to minimize x‐ray fluence. Data was recorded for tube potentials of 80, 100, 120, and 140 kVp. However, the 140 kVp potential saturated the detector. The second set of CT energy spectrums was derived by utilizing a MC simulation to pass a soft tungsten anode spectrum through a proprietary beam hardening material and recording the resulting spectrum. The initial tungsten anode spectrum was obtained using an implementation of Boone and Seibert's tungsten anode spectral model. Results: The MDCT scanner uses a tungsten anode which theoretically results in a spectrum with characteristic x‐rays of 59 keV and 67 keV. The second characteristic x‐ray peak was clearly evident in all of the measured spectrums; however, the first characteristic x‐ray peak was almost nonexistent. The derived spectrums were similar to the measured spectrums in that most of the soft energy in the 30–50 keV range had been filtered out. However, both characteristic x‐rays were present in the derived spectrums. Conclusion: Different spectrums resulting from measured and derived methods suggest a machine specific spectrum should be acquired for accurate Monte Carlo patient dose evaluation. The attenuation in the measured spectrum indicates the presence of a fairly significant hardening filter which may not have been fully accounted for when developing the derived spectrums.
SU‐E‐I‐34: On‐Line Program for CT Quality Control
Authors: Borras C , Costa P , da Silva A Marques
Published: July 2013

Purpose: An on‐line quality control program (QC) for computed tomography (CT) scanners was developed in Porto Alegre and in Sao Paulo, two main cities of Brazil, led by two university medical physicists, and coordinated by the Health Technology Task Group of the International Union for Physical and Engineering Sciences in Medicine. Method and Materials: Using a combination of commercial phantoms and software and in‐house computer programs, and following the methodologies developed by the AAPM and the ACR, the following parameters were documented with the purpose of being periodically monitored: CT protocols for adult and pediatric head and abdomen scans, evaluation of scanner performance and image quality, and CTDI information from DICOM headers for the head and abdomen studies. The initial evaluations were performed by medical physicists, who then trained the CT technologists at the institutions to scan the phantoms, extract the information from the DICOM headers and transmit the data to the two Brazilian universities, which collated and analyzed the results. Results: The problems encountered in the implementation of the on‐line program in over 30 CT facilities, especially regarding DICOM interconnectivity issues, will be reviewed. Initial results showed that although most scanners complied with AAPM/ACR requirements regarding image quality, there was a wide range of doses for each procedure among and even within the institutions, pointing out to the lack of optimized image acquisition protocols. Conclusion: The need to implement QC programs for CT has been recognized for a long time. However, the scarcity of diagnostic medical physicists in resource‐limited settings requires innovative solutions such as this on‐line program that allows local data gathering and remote data analysis.
SU‐E‐I‐35: Using Six‐Sigma Methodology for Practice Quality Improvement Projects
Authors: Paden R
Published: July 2013

Purpose: To illustrate the utility of Six‐Sigma tools for Practice Quality Improvement Projects Methods: Practice Quality Improvement (PQI) Projects are required as a component of Maintenance of Certification (MOC). The methodology of Define, Measure, Analyze, Improve, and Control (DMAIC) is particularly well suited for PQI. An example of the DMAIC approach is presented using the CT pulmonary embolism protocol. Within DMAIC the Define phase consists of stating the problem and the processes involved in the task. During Measure phase the baseline performance of the process is established. Analyze phase involves looking at the data collected and proposing methods to enhance the process. The Improve phase comprises the changes that are made to the process. Control phase consists of follow‐up to insure that improvements are robust and remain in place over time. For the CT pulmonary embolism example:Define: For dose reduction purposes kV is switched from 120 to 100 resulting in higher mA values than desired by the Radiologist. Manual mA is utilized instead of mA modulation techniques.Measure: Baseline CTDIvol values across patient sizes for pulmonary embolism.Analyze: What modulation algorithm will Result in similar doses? Improve: Pilot studies with adjusted mA modulation parameters. Control: Establish a database to continually monitor doses from pulmonary embolism protocol. Results: Baseline measurements demonstrate four dose levels 2.1 mGy, 3.9 mGy, 4.9 mGy, and 10.9 mGy, depending on patient size measured laterally on a localizer radiograph. After a size‐based protocol chart is implemented dose values are variable ranging from 1.02 mGy to 12.19 mGy. Conclusion: The DMAIC approach can successfully be implemented during Practice Quality Improvement Projects.
SU‐E‐I‐37: Lesion Circularity as a Potential Indicator for Detectability in Low Dose Abdomen CT
Authors: Magnetta M , Dong F , Baker M , Primak A , Herts B
Published: July 2013

Purpose: Low‐contrast lesion detection is critical for abdomen CT. However, there is no standardized, objective measure of the detectability of low‐contrast objects. The purpose of this study is to investigate a new measure, the ability of a circular lesion to maintain its shape or circularity, as a potential indicator of lesion detectability. Methods: An anthropomorphic phantom with embedded spherical liver lesions was custom‐designed to assess the effectiveness of iterative reconstruction for improving the low contrast lesion detection. This phantom consists of 36 spherical lesions with 3 different sizes (5mm, 10mm, and 15mm). Each size has three different contrast levels. All spherical lesions were embedded non‐uniformly to minimize the memory bias for a concurrent human observer study. Phantom was scanned with a MDCT (Siemens Definition Flash) at multiple dose levels and images were reconstructed with both filtered back‐projection (FBP) and Iterative Reconstruction (SAFIRE). An adaptive Wiener filter was applied during the lesion detection. The circularity was calculated based on the ratio of the area to (perimeter)2 of each detected lesion. Results: The circularity was normalized to 1 when the detected lesion has a perfectly circular shape and the boundary is connected. At 50mAs, the circularity for a 10mm spherical lesion with 18HU contrast was 0.618 with FBP vs. 0.650 with SAFIRE; While at the same mAs, for a 15mm spherical lesion with 12HU contrast, the circularity was 0.666 with FBP vs. 0.763 for SAFIRE . At 200mAs, the circularity for a 10mm spherical lesion was 0.811with FBP vs. 0.870 with SAFIRE ; for a 15mm lesion, the circularity was 0.818 with FBP vs. 0.863 with SAFIRE. Conclusion: Circularity decreased with decreasing lesion size, contrast differential and dose. Iterative reconstruction techniques improved upon lesion circularity when compared to FBP at the same dose level, at similar lesion size and density differences. Dr. Herts and Dr. Baker are currently funded by Siemens Healthcare for research in low dose abdominal CT.
SU‐E‐I‐43: Automatic Exposure Control Or Fixed Tube Current? : Evaluating Dose Effectiveness of AEC in Pediatric Chest CT Examinations with CTDIvol, SSDE, and Water‐Equivalent SSDE
Authors: Chun M , Heo C , Cheon J , Kim J
Published: July 2013

Purpose: To investigate the effectiveness of automatic exposure control (AEC) in pediatric CT examinations in terms of volume CT dose index (CTDIvol), size‐specific dose estimates (SSDE), and water‐equivalent size‐specific dose estimates (SSDEw). Methods: We selected 179 pediatric chest CT examinations of patient ages 1 ∼ 15 taken with or without AEC (AEC: 88, FIXED: 91). A 16 slice MDCT(Sensation 16, Siemens) was used with tube potentials of 80kVp. The reference level for AEC was different for each patient. We assigned CT exams into one of four age groups: under 2, 25, 6&–10, and under 15. We segmented body regions using a seeded region growing method. The effective diameter (Deff) and the water‐equivalent diameter (DW) were calculated at each slice. CTDIvol was extracted from the conventional DICOM dose report image using optical character recognition (OCR) technique, and then SSDE and SSDEw were derived according to AAPM TG 204 based on Deff and DW. The patient dose was compared for with and without AEC exams using those 3 CT dose metrics. Results: Patient dose of exams with AEC was lower in all age groups regardless of the 3 CT dose metrics. CTDIvol, SSDE, and SSDEw with AEC were 1.61±1.13, 2.85±1.29, and 3.23±1.53 mGy and those without AEC were 2.86±1.34, 5.42±2.61, and 6.21±1.93 mGy, which represent dose reduction of AEC exams by 56.3%, 52.6%, and 52.0%, respectively. Conclusions: Our study revealed that patient dose of exams with AEC was substantially lower than that without AEC by 52 ∼ 56.3 % in pediatric chest CT examinations. Our study results suggest that AEC technique is recommended in pediatric CT exams. The research was supported by the Converging Research Center Program through the Ministry of Education, Science and Technology (2012K001498)
SU‐E‐I‐44: Direct Organ Dose Measurements in Cadaveric Subjects to Investigate Dose Reduction Provided by Iterative Image Reconstruction Techniques
Authors: Mench A , Sinclair L , Griglock T , Cormack B , Bidari S , Arreola M
Published: July 2013

Purpose: To quantify average organ dose reduction resulting from use of adaptive iterative image reconstruction algorithm in Computed Tomography (CT). Methods: To determine the average organ dose reduction offered by the Adaptive Iterative Dose Reduction algorithm (AIDR3D) on a Toshiba Aquilion One 320‐slice CT scanner, organ doses were directly measured utilizing a method involving cadaveric subjects and optically‐stimulated luminescent dosimeters (OSLDs). Three female cadaveric subjects of various body habitus were scanned for the case of a clinically standardized Chest Abdomen Pelvis (CAP) protocol. Average organ doses were measured using OSLDs inserted into the breasts, lungs, liver, stomach, small intestine, colon, ovary, and uterus and placed on the skin of the cadavers. Measurements were first obtained for a standard non‐contrast CAP exam and then again, under identical scanning conditions, with the AIDR3D turned on. Measured doses were compared between the two scans for each of the organs. Results: Average organ dose reduction ranged from as low as 4% to as high as 66% for various organs. When averaged across all organs, the overall percent reduction amongst the three cadaveric subjects ranged from 18% to 46%. Significant dose reduction was noted for the lungs, breast and uterus in all three cadaveric subjects. The cadaveric subject with the lowest BMI level experienced the most prominent reduction in organ doses when compared to the subjects of higher BMI. Conclusions: As CT continues to be an indispensable tool in diagnostic radiology, future technological developments will remain focused on dose reduction methods. From this work it is clear that use of the AIDR 3D image reconstruction algorithm offers significant organ dose savings to patients. Based on recent literature and our own clinical experience, the dose savings do not come at the cost of degraded image quality.
SU‐E‐I‐47: A Classification of Validation Tasks for Monte Carlo Simulations of CT Scanners: From Simple to Complex Source Models and Geometries
Authors: McMillan K , Khatonabadi M , McNitt‐Gray M
Published: July 2013

Purpose: To develop a classification system of validation tasks for Monte Carlo simulations of CT scanners that reflects the level of complexities of source and object models used in Monte Carlo simulation methods within the medical physics community and specifically within X‐ray CT dosimetry simulations. Methods: In order to quantify the relative strength of CT Monte Carlo models developed for CT dosimetry with respect to imaging parameters such as source motion, tube current modulation, phantom type and location of measurement, we have devised a classification system consisting of six levels, each with a number of sublevels that encompass an extensive number of validation scenarios. The complexity of the levels/sublevels ranges from very simple source and object models, such as simulating and validating a CTDI in air measurement at isocenter with a single axial source rotation and fixed tube current, to complex source and patient models, such as simulating and validating surface and depth dose integrated readings from TLDs for a patient model with helical source movement and tube current modulation. 15 unique CT Monte Carlo models found in the literature with some validation of Monte Carlo simulations were examined within the scope of the classification system. Results: All 15 models had a primary validation measurement that fell under the first two levels of the classification system, CTDI measurements. Only 5 models demonstrated validation of the model beyond CTDI measurements. Only 2 of these models demonstrated helical scan validation. No models demonstrated tube current modulation validation. Conclusion: This investigation has revealed that a vast majority of advanced CT dosimetry Monte Carlo simulations lack validation beyond CTDI measurements. This classification system has the potential to be used as a justification metric as to the appropriateness of a particular CT Monte Carlo model for use in a specific CT dosimetry simulation. (a) Dr. McNitt‐Gray: Institutional research agreement, Siemens AG; Recipient research support Siemens AG; Consultant, Flaherty Sensabaugh Bonasso PLLC; Consultant, Fulbright and Jaworski, LLC; (b) K McMillan: Research partially supported by a grant from Siemens AG; Research partially supported by a grant from AACR; Research partially supported by a grant from TRDRP; (c) M Khatonabadi: Research partially supported by a grant from Siemens AG
SU‐E‐I‐57: Design of a Tabletop Simulating and Testing System for CT Research and Development
Authors: Li X , Liu H , Zhang J
Published: July 2013

Purpose: The performance of a CT system can only be maximized with an optimal combination of design parameters, which need to be thoroughly studied at its early development stage. The purpose of this investigation is to develop a tabletop simulating and testing system for CT research and development. The main functionalities of the system include the simulation of different scanning modes, verification of imaging quality, and testing of key components of CT system. Methods: The tabletop system assembly is composed of three subassemblies: a stationary gantry and its supporting frame, a rotating and elevating stage and its servo system, and a high resolution arc trail testing mechanism. The entire assembly is placed on a rigid mounting table to minimize possible vibration. X‐ray tube and detector assembly can be easily mounted or removed in order to accommodate the need of different testing tasks. A high resolution servo motor is used to drive a detector testing device to move along the rail to scan through the detector array under testing. Results: A tabletop system is designed for CT imaging simulation and key component testing. During testing, the x‐ray tube and detector assembly of the proposed system stay stationary during imaging acquisition. A variety of CT scanning modes and imaging simulations instead can be achieved by controlling the motion of an object rotating and elevating stage. A high resolution arc trail testing mechanism is also adopted for the spatial localization required for detector testing. Conclusion: Our preliminary Result of the prototype system has demonstrated its capability of performing a variety of simulating and testing tasks and providing reliable outcomes in a satisfactory fashion. This new system, with its unique and flexible design, will provide a viable way to speed up the CT research and development process.
SU‐E‐I‐64: High‐Resolution Detection of Cerebral Neurochemical Profile in Rat Hippocampus After Acute Binge Alcohol Intoxication
Authors: Lee Do‐Wan , Kim Tai‐Kyung , Shin Youngwon , Kim Jae‐Hwa , Kim Sang‐Young , Jung Jin‐Young , Song Kyu‐Ho , Kim Hwi‐Yool , Kim Dai‐Jin , Choe Bo‐Young
Published: July 2013

Purpose: The aim of present study was to provide ex vivo evidence of changes in neurochemical profiles of rat hippocampus after acute‐binge ethanol intoxication, using high‐resolution magic angle spinning (HR‐MAS) NMR spectroscopy using a 500‐MHz spectrometer. Methods: Twenty‐male‐Wistar rats, divided into two groups (control group: n=10, binge ‐ ethanol group: n=10), were used in this study. The 10 rats in binge ‐ ethanol group received an initial ethanol dose of 5 g/kg (30% w/v solution) via oral gavage, then received additional doses of 1.5 g/kg (25% w/v solution) every 8 hours (at 1000, 1800, and 0200 hours) for 4 days. The 10 control rats received an equivalent volume of normal saline, with treatments occurring at comparable times (1100, 1900, and 0300 hours). Ex vivo 1H HR‐MAS spectroscopy was performed using an Agilent VNMRS‐500 (500.13‐MHz). One ‐ dimensional HR‐MAS spectra were acquired from all 20 tissue samples with CPMG sequence [complex data number = 16384, spectral width = 8012.8 Hz, relaxation delay time= 5.0 sec, pre‐saturation time = 2.0 sec, inter‐pulse delay (τ) = 0.4 msec, number of acquisitions = 128, and a total scan time = 15 min 24 sec]. Results: Figure 1 (A and B) shows representative 500‐MHz spectra from hippocampal regions of animals in binge ‐ ethanol and control groups. Figure 2 shows total creatine ratio levels that were quantified from 20 hippocampal tissue samples. Glutamate/tCr (**: p=0.007) and Glx/tCr (Glx: glutamine and glutamate complex [glutamate+glutamine]) (**: p=0.006) ratios were significantly higher in binge‐ethanol group than in control group. Conclusion: Our findings suggest that glutamate signals and glutamate‐glutamine cycle in hippocampal region are particularly sensitive to acute‐binge ethanol consumption. Future studies using a combination of human patients and in vivo animal MRS investigations, as well as other neuroimaging approaches, are required to strengthen our findings and to validate translational component in acute‐binge alcohol intoxicated condition.
SU‐E‐I‐65: Pitfalls in the Production of Enhancement Kinetic Curves in 3T Dynamic Magnetic Resonance Mammography and Means of Avoidance
Authors: Lavdas E , Mavroidis P , Roka V , Fezoulidis I , Vassiou K
Published: July 2013

Purpose: The purpose of the present study is to investigate suggested means for the reduction or even elimination of errors that appear in enhancement kinetic curves in order to avoid pitfalls and increase the sensitivity and specificity of the method. Methods: This retrospective study included 115 women who underwent breast MRI in a magnetic resonance unit 3‐Tesla. In the MRI acquisition the following sequences were used: a) axial T2‐TSE, b) axial STIR and c) Vibrant (six phases) unenhanced and contrast‐enhanced axial T1‐weighted fat saturation. In the semi‐automated technique there was no consistency in the location of the selected region of interest — ROI in all the phases of the dynamic acquisition during the assessment of the kinetic curves. The measurements were repeated by positioning the ROIs manually from stable reference points in all the phases and the enhancement kinetic curves were subsequently plotted based on the signal intensity. Results: 115 patients were examined and 376 abnormalities were investigated. In 81 cases, a change of the enhancement kinetic curve type was found between the two methods. In large and dense breasts there was not any change in the type of the kinetic curves calculated between the two methods, whereas in the large but non‐dense breasts, 13 lesions were found to be of different type. In the case of the small and dense breasts only 4 lesions changed type, whereas in the case of the small and non‐dense breasts, 64 lesions changed type out of which 50 were observed in left breasts and 14 in right breasts. Conclusion: The derivation of enhancement kinetic curves should be performed by controlling and verifying that the ROIs lay at the same location of the lesion in all the phases of the dynamic study. In these cases, the use of stable reference points should be employed.
SU‐E‐I‐81: Experimental Study of Many‐View Under‐Sampling CT
Authors: Lee T , Hammad M , Cho S
Published: July 2013

Purpose: Sparse‐view CT takes projections at sparser view‐angles and provides a viable option to reducing radiation dose. However, a fast power switching of an x‐ray tube, which is needed for the sparse‐view sampling, can be challenging in many CT systems. We have recently proposed a many‐view under‐sampling (MVUS) technique as an alternative to sparse‐view CT. Methods: We used a bench‐top circular cone‐beam CT projection data set of a water‐phantom which includes 720 projections. The multi‐slit collimator made of tungsten was mounted on the X‐ray source for beam blocking. The collimator is composed periodically of slit‐openings and radio‐opaque rectangular areas, and the length dimension of the slits is parallel to the rotation axis. In addition, we used a sinusoidal motion of the collimator to the perpendicular direction of the rotation axis for the purpose of more uniform spatial sampling of the image. For image reconstruction, we used a total‐variation minimization (TV) algorithm and modified the POCS step so that only the measured data through the collimator slits are to be used in the computation. Results: Image reconstruction parameters are thought to play an important role in determining the image quality. More study for the optimization of reconstruction parameters is under progress and will be reported in the conference. Conclusion: We proposed a novel scanning method for low‐dose CT, and performed a real‐study to possible.