bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐I‐17: Evaluation of Cone Beam Breast CT (CBCT) System: Detection of Randomly Distributed Micro‐Calcification and the Effect of Beam Hardening Filter
Authors: Ge S , Lai C , Yi Y , Shen Y , Liu X , Zhong Y , You Z , Wang T , Shaw C 
Published: November 2011

Purpose: Detectability of micro‐calcification is very important for breast imaging. The purpose of this study is to evaluate the breast CBCT system through its detectability of randomly distributed micro‐calcifications under different mean glandular dose (MGD) and with or without different thickness copper filters. Methods: Calcium carbonate grains of various sizes (Three size groups: 224–250μm, 250–280μm, 280–300μm) were used to simulate calcifications. A breast shaped plastic container filled with paraffin was used to simulate a fatty breast; the top half of the phantom was cylindrical with 12.5cm diameter and the total height of the phantom is 14.5cm. The phantom was imaged with a CBCT system in our lab. The system consists of a conventional tungsten target x‐ray tube (G‐1592) and an a‐Si:H/CsI flat panel detector (Paxscan 4030CB). The source to image detector and source to iso‐center distances were 152 and 100 cm, respectively, resulting in a magnification factor of 1.52 at the iso‐center. All the scans were conducted at 80 kVp. The experiment was conducted under MGD equal to 2.5, 4, 6, 8 mGy. With each MGD setting, the scan was conducted without filter, with 0.002″ copper filter or with 0.004″ copper filter. Feldkamp algorithm with a ramp filter was used for image reconstruction of all scans. Results: Our CBCT system is capable of imaging calcifications as small as 224–250μm with 6mGy MGD or 250–280μm with 4mGy MGD if set 50% visibility as threshold. To all three size groups, filtering improves visibility of micro‐calcification when the dose is between invisible and high visible settings. Conclusions: Filtering improves detectability of micro‐calcification for low dose image.This work was supported in part by grants CA104759, CA124585 and CA13852 from NIH‐NCI, a grant EB00117 from NIH‐NIBIB, and a subcontract from NIST‐ATP.
SU‐E‐I‐21: The Effects of MV Scatter on Image Quality of Cone Beam Scans Acquired Asynchronously during Rotational Delivery
Authors: Lovelock D , Munro P , Shapiro E , Star‐Lack J , Sun M , Ling C 
Published: November 2011

Purpose: To effectively integrate image‐guidance into single dose (24 Gy) SBRT to bony targets, we propose to deliver the treatment in 6 consecutive VMAT arcs and simultaneously acquire a CBCT image during each arc. This would provide a means to check and correct for intra‐fractional target motion subsequent to the 1st arc. We investigate the effect of the MV scatter on CBCT image quality and report on the feasibility of simultaneous SBRT / CBCT for intra‐fractional imaging. Methods: The CatPhan and anthropomorphic Rando phantoms were irradiated with 360° arcs using a static 10×10 cm field, and kV CBCT projections were acquired simultaneously. To investigate the effect of MV scatter on CBCT image quality, we varied the phantom size, MV dose and dose rate, CBCT mAs, and the SSD of the kV detector. In addition, a CBCT reconstruction algorithm that reduced the detrimental effects of scattered MV radiation was studied. Results: : Scattered MV radiation added noise to reconstructed images, decreasing low contrast resolution while reducing Hounsfield Unit (HU) accuracies. Increasing the size of the phantom magnified these effects since the scatter‐to‐primary ratio is increased. In part, this could be compensated for by increasing the CBCT exposure (mAs), and by increasing the separation between the isocenter and the kV detector from 50 to 80 cm. The new CBCT scatter correction algorithm was shown to offer promise of increasing HU accuracies. With the combined methods to increase SNR, good quality CBCT images that clearly visualize bony targets were obtained, even when 750 MU was delivered in an arc treatment. Conclusions: For the proposed clinical application, kV‐CBCT scans are acquired concomitantly with MV radiation delivery. These images, if automatically registered to the planning CT scan, provide monitoring of possible intra‐fractional motion, and allow, if necessary, for corrections to be made.Supported in part by Varian Medical Systems
SU‐E‐I‐22: Non‐Clinical Applications for Cobalt‐60 Cone Beam CT Imaging
Authors: Marsh M , Rawluk N , Nguyen H , Bevan G , Schreiner L 
Published: November 2011

Purpose: To investigate possible applications of a Cobalt‐60 (Co 60) cone‐beam megavoltage computed tomography (CoCBCT) imaging system, developed for patient positioning on Co‐60 teletherapy machines, in non‐clinical fields such as archaeology and non‐destructive testing. Methods: CoCBCT scans were performed on a series of dense objects requiring nondestructive testing using a bench‐top imaging system consisting of a Theratron 780C Co 60 unit (Best Theratronics, Kanata, ON) and a Varian aS500 amorphous silicon portal imager (Varian, Palo Alto, CA). Images were obtained on a series of heavily concreted artifacts recovered from a 17th century shipwreck at LˈAnse aux Bouleaux in Québec. and on cylindrical test cylinders of hematite‐rich shielding concrete obtained during the construction of new linac bunkers in our cancer centre expansion. The CoCBCT images were generated using the FDK back‐projection algorithm from transmission portal images that were obtained by rotating the objects by 1.5° degree increments through a full rotation. Results: In the case of the shipwreck artifacts, CoCBCT allowed dense metal features such as lead shot to be identified within the concretion layers, and offered a clear view of the shape of voids and other features that would be difficult or impossible to see without damaging the objects. These images will guide subsequent manipulation of the objects during archaeological assessment. CoCBCT images of the concrete cylinders reveal details in the concrete structure, such as voids or aggregate segregation, that would affect the shielding performance of the concrete. Consistent, uniform distribution of the aggregate in most of the samples implied that the mix was stable and not likely to segregate in the shielding walls. Conclusions: Co 60 CBCT is also suitable for non‐destructive imaging of highly attenuating non‐clinical objects, including items with large metal features which would limit accurate imaging using kV CT or broad energy spectrum MV CT.Funding from the Ontario government has been secured through the Ontario Consortium for Adaptive Interventions in Radiation Oncology (OCAIRO), which matches funding from an industrial partner, Best Theratronics (Kanata, ON).
SU‐E‐I‐24: Pediatric CT Effective Dose ‐ A Comparison Between the MOSFET Method and the DLP Method
Authors: Fredrickson M , Toncheva G , Frush D , Lowry C , Yoshizumi T 
Published: November 2011

Purpose: The effective doses (ED) were compared between the MOSFET method and the DLP method for a variety of clinical CT scans. Methods: Two CT scanners (Manufacturer A and B) were used in this study. Organ doses were measured with MOSFET detectors. Twenty MOSFET detectors were inserted in the 5‐year‐old anthropomorphic phantom (CIRS, Norfork, VA). The calibration factor for each MOSFET was determined using equivalent CT beam quality of respective manufacturer separately. The phantom was scanned using head, chest, abdomen‐pelvis and chest‐abdomen‐pelvis protocols at our institution. CTDIvol and DLP were recorded from the scanner console display. The MOSFET method employed the ICRP 103 weighting factors to calculate ED; the DLP method used the AAPM 96 (2008) anatomy‐age specific k‐factors. Pediatric protocols except head used CTDIvol data from 32 cm CTDI phantom. For this reason a factor of approximately 2 was applied to the CTDIvol and DLP in body protocols. In addition, CTDIvol measurements were performed with a Piranha CT Dose Profiler (RTI, Fairfield, NJ). Results: The calculated ED from manufacturer A scans underestimated the ED for the head, chest, chest‐abdomen‐pelvis and abdomen‐pelvis scans by 133.27%, 55.84%, 30.24% and 19.13%, respectively. The calculated ED from manufacturer B scans underestimated the ED for the head by 85.66% and overestimated the ED for the chest, chest‐abdomen‐pelvis and the abdomen‐pelvis scans by 102.81%, 114.52% and 96.19%, respectively. The percent difference between console and measured CTDIvol ranged from 11.04% to 24.88% Conclusions: ED calculations from the DLP method differed grossly from the MOSFET method. Console displayed CTDIvol showed good agreement with measured values. One possible explanation for ED disagreement between the two methods may lie in inaccuracies of k‐factors. These k‐factors were computed from old Monte Carlo codes based on mathematical phantoms. Additionally, manufacturer specific conversion factors may need to be proposed.Funding for this research was provided by GE Healthcare and Siemens Healthcare.
SU‐E‐I‐41: The DCE Tool: A Freeware Analysis Tool for DCE CT and MR Studies
Authors: Yeung I , Haider M , Gonzalez N , Kim S , Coolens C , Yeung T , Driscoll B , Jaffray D 
Published: November 2011

Purpose: To develop a freeware tool for analysis of dynamic contrast enhanced (DCE) CT and MR studies.Methods: The DCE Tool was developed as FREEWARE to work as a plugin for the the ClearCanvas 2.0SP1 framework. It combined the NET Platform and the MATLAB MCR to provide robust DCE analysis. The software was designed to support CT and MR studies with display capability of DCE data. The analysis included simple metrics on time‐intensity curves as well as on compartmental modeling analysis. Easy export of results to spreadsheet file was also a design requirement.Results: The DCE Tool has been developed to process DCE CT and MR studies. DICOM images from CT and MR studies can be loaded to the software and a 4D time browser is available to view the images. Region of interest tool is available which produces time intensity curves, for which the DCE Tool provides analysis on area under curve, initial slope and peak etc. It also provides analysis using the 1‐compartment model, 2‐compartment model, the ATH (adiabatic tissue homogeneity) model for CT, as well as the Toftˈs model for MR study. Pixel‐by‐pixel analysis is available and functional maps can be generated. Numerical and graphic results can readily be exported to EXCEL files. The tool has been used by a number of researchers for phantom and pre‐clinical studies. The DCE Tool is available for free download at www.thedcetool.com Conclusions: The DCE Tool has been developed for DCE CT and MR studies. It provides analysis based on density intensity curves as well as tracer kinetic modeling. The DCE Tool is potentially an invaluable research tool for CT and MR perfusion studies.The project is partly funded by Ontario Institute of Cancer Research
SU‐E‐I‐66: Estimating Organ and Effective Doses for Digital Tomosynthesis Imaging Using PCXMC Software
Authors: King J , Ma H , Elbakri I 
Published: November 2011

Purpose: In order to accurately model a tomosynthesis image acquisition for estimating organ and effective doses with PCXMC, we must consider each discrete projection angle of the x‐ray tube separately, compute the dose in each case, and sum the results. This can be a time‐consuming task that requires a considerable amount of data entry. We have developed two techniques that we can use to improve the user‐friendliness and time‐efficiency of obtaining dose estimates for a tomosynthesis sweep. Methods: We developed a MATLAB program to automatically generate the definition files for each x‐ray tube position and compared the resulting definition files and dose calculations to those that we created manually for two test cases. We also calculated the doses by simplifying the imaging geometry to neglect the motion of the x‐ray tube during the tomosynthesis sweep. We applied the sum of the incident air kerma for the entire sweep to a single, central projection, and evaluated the impact of this simplification on the speed and accuracy of the dose calculations. Results: Our program produced the same definition files and doses as our manual calculation in both cases, and using the program resulted in a dramatic reduction in the amount of time required to complete the calculations. When neglecting the motion of the x‐ray tube, the doses to some organs were over‐ or underestimated but the effective doses still agreed with the values calculated using the more accurately modeled geometry. Conclusions: Our MATLAB program allows us to accurately model the imaging geometry of a tomosynthesis exam in PCXMC in a time‐efficient manner. For both test cases, a reasonable estimate of the effective dose can be achieved very quickly by neglecting the motion of the x‐ray tube, but this also sacrifices the accuracy of individual organ dose calculations.This research was supported by funding from GE Healthcare.
SU‐E‐I‐107: Compositing Daily Images for Coverage and Enhancement
Authors: Gering D 
Published: November 2011

Purpose: Images acquired daily during IGRT typically do not cover the entire treatment area, and they have lower image quality than the planning image. Conventionally, a small daily image is merged with the full‐size planning image in order to form a complete picture of the patient in treatment position. In such a merged image, a given voxel contains new data if it was covered by the daily scan, and otherwise old data from the planning image. The aim of this work is to form a composite image from all available fractions so that the aggregate covers the entire target and exhibits higher image quality. Instead of using just the newest data at each voxel, all available data is blended together. Methods: Every image is segmented automatically into 5 tissue types and 42 anatomic structures. Warp fields that map daily images to the planning image are computed from 4‐parameter rigid registration, 10‐parameter Marionette deformation, and free‐form deformation. The Marionette model allows small images to impact areas outside their scan because bone movements and weight loss are global. Each daily image is warped to every other daily image, and combined via weighted averaging. Weights are assigned to fractions based on age, deformation similarity, and STAPLE probabilities for mandible and spinal cord. Weights are assigned to voxels based on tissue discrepancy to secure data integrity and avoid blurring features. Results: The method was validated on head/neck datasets from 20 patients with a total of 466 daily images. The daily images are helical megavoltage CT. The SNR in muscle was measured to increase by an average of 55%, while CNR between muscle and fat increased by 50%. Conclusions: Image quality was measured to improve in all cases, and small daily images were shown to be useful components of a broader mosaic.Supported by TomoTherapy
SU‐E‐I‐125: Uniform Sampling of Projections during Pulsed Electron Paramagnetic Resonance Imaging Data Acquisition
Authors: Redler G , Epel B , Seifi P , Bryant J , Halpern H 
Published: November 2011

Purpose: To devise a generalized, object‐independent method for uniform acquisition of projections from 3D pulsed electron paramagnetic resonance imaging (EPRI) experiments so that intermediate images approximating the final image may be reconstructed from an incomplete set of projections.Methods: Projection directions for 3D pulsed EPRI experiments can be represented as points on a hemisphere. A new technique is developed to divide the hemisphere into sectors of equal area and sample the projection points such that the standard deviation of the number of these points per sector is minimized. These sectors are defined by number of divisions in azimuthal and polar angles. Images of a cylindrical phantom were obtained using the current polar‐azimuthal raster scheme as well as this new uniform sampling scheme with different hemisphere divisions for comparison of rapidity of convergence to the final image. The mean square difference between intermediate images and the final image was the metric compared.Results: The uniform‐sampling method produces intermediate images that converge to the true final image more rapidly. An image reconstructed from half projection data is 44.6% closer to the final image than an image reconstructed from half projection data using the polar‐ azimuthal raster method. Conclusions: A novel method is developed to uniformly sample projection data for 3D pulsed EPRI that is independent of the object and produces intermediate images converging to the fully sampled image more rapidly than those from a polar‐azimuthal raster sampling scheme. This method can be implemented to allow the user to view the image being created while acquiring projections so that problems with the scan become evident earlier without the need to wait for the entire scan to finish. This new scheme also gives better temporal resolution with the addition of minor artifacts by under sampling projections and requiring less imaging time.Acknowledgement of support: R01 CA98575; P41 EB002034
SU‐E‐I‐168: An Image Quality Assurance Phantom for Positron Emission Mammography (PEM)
Authors: Luo W , Disher N , Lu X 
Published: November 2011

Purpose: Due to the compact geometry of Positron Emission Mammography (PEM), WB‐PET phantoms are not suitable for PEM scanners. This study aims to develop an image quality phantom that can be used for PEM image quality assessment. Methods: A phantom with dimensions of 240 × 160 × 60 mm was designed to assess image quality (uniformity, contrast, linearity, resolution). It has three main components: 1), a cylinder quality phantom with 110 mm ID that consists of 5 suspended hot sphere lesion inserts of varying ID (4,6,8,12,16 mm) filled with 8:1 lesion‐to‐background activity ratio and a 16 mm cold lesion. The center background region (ID = 30 mm, thickness = 28 mm) is selected for uniformity calculation. The lesion‐to‐ background ratio (LTB) is defined by the maximum of the region of interest (ROI) for the inserts divided by the mean of the background ROI. Image contrast is defined by (LTB‐1)/(Actual Activity Ratio‐1). 2), a 120 mm line source with 3.0 mm ID perpendicular to the detector motion for linearity evaluation. 3), fillable bar phantoms (ID =1.1 mm) in X and Y direction with the bar center to center separation increased from 3.0 to 7.5 mm. An optional point source can be added for spatial resolution. A 10 minute, full field of view scan was performed. Results: Quantitative analysis shows in‐ plane spatial resolution of 2.4 mm and uniformity of 7.0%. The image contrasts for the 5 spheres are 74%, 63%, 41%, 25% and 7%. The visual inspection shows the PEM scan detects all sphere inserts. The bar phantom and line source do not show linear distortion. The 3 mm bar phantom can be distinguished in high resolution mode (pixels size 0.4 mm). Conclusions This phantom demonstrates it can be useful for visual and quantitative evaluation of PEM imaging.Research sponsored by Naviscan, Inc.
SU‐E‐J‐85: A New Approach to Evaluating the Impact of Organ Sub‐Volume Sensitivity to Irradiation by Deforming Cohort Dose Data Onto a Single ‘reference Human’
Authors: Saleh Z , Apte A , Sharp G , Deasy J 
Published: November 2011

Purpose: We propose a new approach to normal tissue complication probability (NTCP) investigations by deforming doses from a patient cohort onto a single anatomic frame of reference in order to identify crucial anatomic features. Methods: To perform this study, IMRT treatment plans of seven different prostate cancer patients were used. Organs of interest (rectum, prostate) were delineated manually by an expert physician. CT scans, structures, and prescription dose distributions were exported into DICOM and then imported into the Computational Environment for Radiotherapy Research (CERR). The contrast of the organ of interest was enhanced at the surface boundary using the contour lines and overwriting the Hounsfield Unit (HU) of the CT scan. CTscans [2,7] were deformed onto reference scan CT1 using B‐spline method for deformable image registration available in Plastimatch. The warping of doses [2,7] was then performed utilizing the corresponding B‐spline transformation files. Results: Examination of the Dose Volume Histograms (DVHs) of the prostate reveals a substantial agreement in the mean dose within 1% between the initial prescribed dose and warped dose. However, for organs with large irregularity and heterogeneous dose distribution such as rectum, the DVHs of the warped dose showed larger deviation from the initial prescribed dose. Dose variance shows a significant variation along the rectum anterior wall. Conclusions: This study shows the feasibility of deforming a patient cohort onto a standard anatomy while retaining the dosimetric and volumetric information. This technique works better with organs which have simple geometry that can be indentified on the CT scan. Discrepancies between the initial and warped dose can be attributed to the low resolution CT scans and the choice of the DIR algorithm. This might be improved by mapping onto a reference anatomy with a high resolution CT scan such as the one provided by the Visible Human Project.NIH R01 CA85181
SU‐E‐J‐147: Effect of Audio Instruction on the Tracking Accuracy for a Four‐ Dimensional Image‐Guided Radiotherapy System, MHI‐TM2000 (VERO)
Authors: Nakamura M , Sawada A , Mukumoto N , Takahashi K , Miyabe Y , Takayama K , Matsuo Y , Mizowaki T , Kokubo M , Hiraoka M 
Published: November 2011

Purpose: To assess the effect of audio instruction on tracking accuracy for MHI‐TM2000 (VERO).Methods: Anterior‐posterior abdominal skin surface displacements for ten patients with a lung tumor were measured by a respiratory monitoring system with and without audio instruction. Based on the obtained twenty respiratory patterns, a three‐dimensional movable phantom with a steel ball target of 9.5 mm in diameter was driven along the superior‐inferior direction. The target position was measured in real time by the laser displacement gauge and the orthogonal kV x‐ray imaging subsystem. Simultaneously, the kV x‐ray imaging subsystem predicted the future target position, and then the system controller calculated the corresponding rotation angles. Thereafter, the gimbaled x‐ray head tracked the target based on the command. Total tracking system error (ET) was computed by both target prediction errors and mechanical response errors of the gimbaled x‐ray head, and then compared between with and without audio instruction.Results: By applying audio instruction, the reproducibility of respiratory pattern was significantly improved (p < 0.01), although motion amplitude was increased by a factor of 2.1 on average. The root mean squares of the ET (RMSET) were up to 1.18 mm without audio instruction and 1.26 mm with audio instruction, respectively. There was no significant difference between free breathing and audio instruction in the RMSET (p = 0.26). The correlation between the RMSET and the 90th percentile of respiratory speed (v) was stronger under the conditions of audio instruction (R2 = 0.77) than under the conditions of free breathing (R2 = 0.29) Conclusions: Audio instruction improved reproducibility of respiratory pattern but increased to the v that negatively affected the tracking accuracy. The tracking errors can be deduced from the v for regular respiratory pattern, suggesting upper limit of the v to achieve high tracking accuracy.This research was in part sponsored by Mitsubishi Heavy Industries, Ltd., Japan.