bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐C‐224‐11: Investigating the Effects of Using Several Calibration Conditions on the Measurement Accuracy of Plastic Scintillation Detectors
Authors: Klein D , Wootton L , Tailor R , Beddar S 
Published: November 2011

Purpose: To investigate the effects of using several conditions (employing assorted radiation field sizes, doses, and depths in water) for the calibration of a plastic scintillation detector (PSD) on measurement accuracy. Methods: The detector system comprised one PSD and a charge‐coupled device (CCD) camera‐based reader system designed to implement the chromatic removal method for discriminating Cerenkov light from scintillation signal. PSD systems of this type are typically calibrated using only two calibration conditions. In this study, we constructed twelve calibration conditions using field sizes of 5×5, 10×10, 20×20, and 30×30 cm2; doses of 10 and 100 cGy; and depths of 2 and 10 cm, with the PSD centered in a water phantom for 60Co irradiation. We used every combination of two or more conditions (up to twelve) to produce 4083 distinct sets of calibration factors via a combinatorial computer algorithm. We tested all calibrations against data taken using a clinical linear accelerator with the PSD placed at water‐equivalent depths of dose maximum and 6.6 cm for 6 MV (setups ‘A’ and ‘B’, respectively) and 18 MV (setups ‘C’ and ‘D’, respectively) photon beams. Results: The most accurate calibration resulted from a combination of four conditions using both depths, field sizes of 10×10 and 30×30 cm2, but all using 10 cGy doses. For setups A, B, C, and D the PSD‐measured dose differed from the known dose by 0.5%, 0.9%, 0.3%, and 0.3% respectively. However, six hundred of the calibrations resulted in differences of <1% between PSD and known doses delivered by the linac across the four test setups Conclusions: This study suggests that the accurate calibration of PSDs is flexible with respect to the number of conditions used, though certain condition combinations should be avoided due to their considerable inadequacy in satisfying the requirements of the chromatic removal method.This work was supported in part by the National Cancer Institute through a T32 grant (CA119930‐04) and an R01 grant (CA120198‐01A2).
SU‐C‐110‐01: Strategies for Online Plan Re‐Optimization: Objective Settings and Starting Stage
Authors: Li T , Zhang Y , Wu Q , Yuan L , Yin F , Wu Q 
Published: November 2011

Purpose: To find the most robust strategies of objective setting and starting stage for online plan re‐optimization, so it can be automatically executed within 1 min while providing high quality adaptive plans. Methods: 10 prostate cancer patients, each with 1 planning‐CT and 5 CBCTs, were retrospectively studied to simulate daily re‐optimization. PTV objectives were (same across plans): D95>100% and Dmax<110%. Three OAR optimization objectives were compared: RTOG objectives (same across patients); DVH parameters extracted from original CT‐plans (CT objectives); and DVH parameters extracted from “goal” dose distributions obtained through deformable registration between planning‐CT and CBCT (Deformed‐CT objectives). Two starting stages were compared: optimal‐fluence in original CT‐plan (Warm‐start) and unity‐intensity within PTV (Cold‐start). Conformity index (CI) and homogeneity index (HI) were calculated to assess the target coverage. OAR sparing was evaluated by V50%/V100% for the bladder and V50%/V70Gy for the rectum. Delivery efficiency was evaluated by total‐MU of each plan. Results: (1)Target: CIs (all<1.2) were similar for all objective settings with either Warm‐ or Cold‐start. However, HIs were consistently lower for RTOG (p<0.0001). (2)Rectum: Deformed‐CT objectives achieved slightly lower V70Gy (<2.5cc) than CT or RTOG (p<0.0001). Both CT and Deformed‐CT objectives achieved lower V50% (p<0.0001) than RTOG by 5.7%–23.6%. (3)Bladder: Deformed‐CT and CT objectives had small differences in V100%/V50%, but were better than RTOG (p<0.0001), especially for V50% (6.8%–16.9% reduction). (4)Warm‐start increased total‐MU by 23%±11% for all plans, but also reduced V50% by 9.7%–26.9% for rectum with all objective settings, and reduced V50% by ∼10% for bladder with RTOG setting. (5)Deformed‐CT objectives showed greater advantage over CT objectives when OAR volume in CBCT is >30% larger than planning‐CT. Conclusions: CT and Deformed‐CT objectives are in general superior to RTOG for OAR sparing. Deformed‐CT objective is more robust when OAR volume significantly increases. Warm‐start has better OAR sparing, but significantly increases total‐MU.Research partially supported by a master research grant from Varian Medical Systems.
SU‐C‐110‐05: Analysis of Intra‐ and Inter‐Fractional Range Variations to Fiducials in Proton Radiotherapy of Liver Tumors
Authors: Rubinstein A , Chen G , Mori S , Hong T , Wolfgang J 
Published: November 2011

Purpose: To quantify radiological pathlength variations to fiducials in proton beam treatment of liver tumors. Methods: Serial 4DCT scans of 10 patients with primary liver tumors were analyzed. The water equivalent pathlength (WEL) was quantified from entrance surface to radio‐opaque clips 1) for different respiratory phases 2) for serial 4DCT scans 3) for each treatment angle (typically AP or PA and a single lateral field) 4) for different immobilization methods. WEL measurements to fiducials is well defined, Vs range to the distal surface of a deformably registered target, but results in fewer measurements (typically 3 clips). A statistical analysis of the mean range variations and spread is performed. Results: AP range at T50 to clips is reproducible from day to day with a mean variation of 1.8mm, SD 1.3mm. Lateral field range variations from day to day at T50 were 1.3mm SD 2.6mm. Range variations at inhale were more variable, with AP T00 mean WEL variation of 3.5mm SD 4.4mm and lateral mean variations of 3.2mm SD 1.7mm. An 8mm lateral range variation was observed in one patient. Range variation during respiration was also studied. The mean AP and lateral range variation was 3mm SD 2.4 and 4.1 mm SD 2.1mm. A 13mm variation was observed in one patient, and attributed to clip motion during respiration without significant change in the entrance surface. Conclusions: Several sources of range uncertainty are routinely included in treatment range determination for proton therapy. These include uncertainties in CT HU numbers, relative stopping powers of tissues, compensator misalignment, etc. Organ motion is explicitly taken into account in the aperture plane, but not in the beam direction. This study elucidates the magnitude and causes of range variations to well defined points. Inclusion of this uncertainty should be considered in determining treatment range.The project described was supported by Award Number P01CA021239 from the National Cancer Institute. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Cancer Institute or the National Institutes of Health.
SU‐C‐301‐03: A Spatially Distributed X‐Ray Source Array for High Resolution Digital Breast Tomosynthesis
Authors: Qian X , Yang G , Sultana S , Gidcumb E , Tucker A , Spronk D , Sprenger F , Lu J , Zhou O 
Published: November 2011

Purpose: The current digital breast tomosynthesis (DBT) scanners are based on regular full‐field digital mammography systems and require partial isocentric motion of an x‐ray tube over certain angular range to record the projection views needed for reconstruction. This prolongs scanning time and degrades imaging quality due to motion blur. The purpose of this study is to evaluate the feasibility of improving spatial resolution and scanning speed of the current DBT device by replacing mammography tube with a stationary carbon nanotube (CNT) based x‐ray source array. Methods: A spatially distributed multi‐beam field emission x‐ray (MBFEX) source array was designed for DBT. Electrostatic simulations were carried out to design the electron focusing optics to achieve the desired x‐ray focal spot size. Finite element analysis was performed to determine the x‐ray source anode heat load. A control electronic system was developed to scan and to regulate the imaging dose from each beam by compensating the driving voltages and by modulating the exposure time from each beam. The x‐ray flux, lifetime, focal spot size, variation between different beams, etc were characterized. Results: A MBFEX source array with 31 individually controllable beams covering 30 degrees viewing angle was fabricated. It is operated up to 50KVp anode voltage and 30mA tube current per beam at an effective focal size comparable to that of the traditional mammography tube. Consistency in the beam‐to‐beam performance was achieved by optimizing the CNT cathodes and by electronic compensation. Tomosynthesis images of a breast phantom were obtained using the new source array. Conclusions: These preliminary results demonstrate the feasibility of CNT x‐ray source array for stationary DBT to eliminate image blurring from tube motion. With a fast detector the device can provide a higher spatial resolution at a reduced imaging time compared to the current rotating gantry DBT systems.This research is currently supported by the following grants&#65306;NCI Grant No. U54CA119343, NIH R01 Grant No. CA134598‐01 and the University Cancer Research Fund at the University of North Carolina. Dr. Xin Qian, was supported by a fellowship from DoD Grant No. BC087505.
SU‐C‐220‐01: Comparative MTF and DQE Performance of Wireless Digital Image Receptors
Authors: Murphy S , Christianson O , Samei E 
Published: November 2011

Purpose: Two new wireless digital receptors were evaluated and compared with a conventional flat‐panel using the International Electrotechnical Commission formalism (IEC 62220‐1) for measuring modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE) using two filtration schemes. Methods: Raw images were acquired for three image receptors (Pixium 4600, Trixell; DRX‐1C and DRX‐1, Carestream Health, Inc.) using a radiographic system with a well‐characterized output (Philips Super80 CP, Philips Healthcare). Free in‐air exposures were measured using a calibrated radiation meter (Unfors Mult‐ O‐Meter Type 407, Unfors Instruments AB). Additional aluminum filtration (and a new alternative combined copper‐aluminum filtration) were used to conform the x‐ray output to IEC‐specified beam quality definitions RQA5 and RQA9. Testing was performed to exclude lag effects. Assessment of the DR systems followed the IEC 62220‐1 formalism. Each detector was irradiated with RQA5 and RQA9 open beams with each filtration at increasing photon fluence to determine the system conversion function. The normal exposure level (XN) was set at 1.0 mR to the detector surface. The NPS was evaluated at XN/2, XN, and at 2XN. The prescribed edge test device was used to evaluate the MTF. The DQE was then calculated from the MTF and NPS functions. Results: All three DR systems demonstrated similar MTFs at most frequency ranges, while the DRX‐1 showed lower values near the cutoff of approximately 3.5 cycles/mm. At each exposure, the Pixium 4600 and DRX‐1C demonstrated similar NPS curves that indicated better noise performance than the DRX‐1. Zero‐frequency DQEs for Pixium 4600, DRX‐1C, and DRX‐1 were approximately 63%, 74%, and 38% for RQA5 and 42%, 50%, and 28% for RQA9, respectively. Conclusion: In terms of DQE performance, the DRX‐1C image receptor is superior to the Pixium 4600 and DRX‐1. Wireless DR receptors offer high‐quality alternatives to CR for portable imaging applications.Supported in part by Carestream Health, Inc. (Rochester, NY)
SU‐C‐220‐02: A High Efficiency Grid System for Abdominal Radiography
Authors: Gauntt D , Barnes G 
Published: November 2011

Purpose: To improve scatter control in abdominal radiography.Methods: A crossed grid system was constructed and consists of a stationary low ratio, high strip density conventional grid (8:1, 60 lines/cm) positioned above and with its septa orthogonal to the septa of a novel high ratio, air interspace, coarse strip density scanning grid (15:1, 2.0 lines/cm). The latter has articulating grid slats; during an exposure the slats remain focused on the x‐ray focal spot. To suppress grid line artifacts, a trapezoidal x‐ray exposure was generated and coupled with the movement of the scanning grid. This effectively eliminates grid line artifacts for small grid movements. The grid DQE was measured for 4 grid configurations: the crossed grid system, the scanning grid alone, a stationary 15:1 conventional grid, and no grid. The measurements were made with standard CsI flat panel detector and a variety of acrylic thicknesses and x‐ray tube potentials.Results: In all cases the DQEgrid measured with the various grid systems was markedly better (130% to 580%) than that measured without a grid. The performance of the crossed grid system was 6% to 120% better than the conventional 15:1 grid. The scanning grid system performed 22% better (20 cm acrylic, 60 kVp) to 6% worse (40 cm acrylic, 120 kVp) than the crossed grid system. While subtle gridline artifacts are present in flat‐field images, the artifacts are invisible in images of anthropomorphic phantoms Conclusions: A high efficiency scanning grid system has been designed and constructed. The system requires only a short grid movement during an exposure to suppress grid line artifacts. It can be used with or without a crossed conventional low ratio grid. In either case, its dose efficiency in controlling scatter is markedly superior that of a high quality, high ratio conventional stationary grid.The authors are co‐owners of X‐Ray Imaging Innovations, which has developed this technology, and are co‐inventors of U.S. Patent 6,795,529, which covers this technology
SU‐C‐220‐03: Texture‐Based Identification of Pathologic Change on Temporally Subtracted Radiographic Chest Images
Authors: Armato S , Lee M , Yu G , MacMahon H 
Published: November 2011

Purpose: Temporal subtraction images created from sequential chest radiographs provide a tool for the enhanced visualization of pathologic change. Although these images provide valuable information to radiologists, the presence of misregistration artifacts could confound the appreciation of actual pathologic change regions. The purpose of this study was to develop a method for the automated identification of pathologic change depicted on temporal subtraction images using a texture‐based classification framework.Methods: Eighty‐eight temporal subtraction images derived from the posteroanterior chest radiographs of 49 patients were created using an existing temporal subtraction algorithm. With the corresponding computed tomography (CT) scan as a reference, an experienced radiologist manually outlined all regions of pathologic change on each subtraction image to provide the “truth.” Generated with each subtraction image was a corresponding “lung mask” image that defined the spatial extent of the lung fields within the image. Candidate pathologic change regions were segmented within the lung mask using a gray‐level thresholding technique, and morphological features computed for each region (e.g., area, circularity, perimeter) were used to reduce false positives. Texture features extracted from a 64×64‐pixel region of interest (ROI) placed over the centroid of each remaining candidate within the subtraction image were input to an automated linear discriminant classifier, which was trained using the regions of actual change outlined by the radiologist. Performance was evaluated using receiver operating characteristic (ROC) analysis.Results: A resubstitution classifier training/testing paradigm applied to the set of change region candidates yielded an area‐under‐the‐ROC‐curve value (Az) of 0.75. A 10‐fold cross validation training/testing paradigm for evaluating “truth” regions yielded Az=0.88 Conclusions: This study demonstrates the potential for texture features to distinguish regions of pathologic change from misregistration artifacts on temporal subtraction images of the chest. Future work will seek to improve the extraction of initial region candidates.Disclosure statement: SGA and HM receive royalties and licensing fees through the University of Chicago related to computer‐aided diagnosis. HM is a consultant for Riverain Medical.
SU‐D‐BRB‐02: Monte Carlo Modeling of the Gamma Knife Perfexion
Authors: Best R , Bennett M , Gersh J , Wiant D , Bourland J 
Published: November 2011

Purpose: For dosimetric and research irradiation studies, we have implemented a Monte Carlo (MC) dose computation model based on the physical and radiological characteristics of the Gamma Knife Perfexion (GK PFX) using the Penelope MC dosimetry codes. GK dosimetric aspects examined include: 1) output factors (OF) for each of the three GK collimator sizes (4, 8, 16 mm), 2) OFs for each source row and collimator size, and 3) dose distribution profiles. Methods: Vendor proprietary information facilitated our modeling of the GK PFX irradiation geometry, which was mathematically defined within Penelope. MC simulations were carried out on a Linux cluster. 3D dose distributions were analyzed using Matlab. A 16 cm diameter dosimetry sphere was modeled with a virtual detector volume at its center. Detector volume varied from 33 to 590 mm̂3 to study detector volume effects. A single source per row was modeled for five rows for each collimator (15 beams modeled). Single‐source dose distributions were rotated about the z‐axis of the axially symmetric geometry and summed to simulate all 192 sources. Results: Good agreement is found for row‐ and total‐output factors (greatest deviation <2% for the 4 mm collimator) compared to reference values. Simulated and measured full‐width at half‐ max values of 3D dose distribution profiles show sub‐millimeter differences (0.4 mm, 4 and 8 mm collimators; 0.9 mm, 16 mm collimator). There is excellent agreement for integrated profile shapes. Conclusions: Detailed geometric representations (radiation source, device components) of the GK PFX are required for high fidelity MC simulations. Calculated GK PFX OF values are dependent on the simulated detector volume size (4 mm OF most dependent). Our model shows strong agreement for the GK PFX OFs and dose profile shapes compared to reference values.Acknowledgement: Non‐disclosure agreement for proprietary information with Elekta AB. No financial contribution.
SU‐D‐BRC‐06: Multimodality Assessment of Response to Combined Chemoradiation and Anti‐Angiogenic Therapy with CuATSM‐PET, FLT‐PET, and Contrast‐Enhanced CT Imaging
Authors: Nyflot M , Simoncic U , Harari P , Perlman S , Jeraj R 
Published: November 2011

Purpose: The integration of molecular therapies into chemoradiation treatments has motivated improved tools for treatment assessment. We used hypoxia, proliferation, and perfusion imaging techniques for multimodality response assessment in patients receiving combined therapy. Methods: Ten HNSCC patients received anti‐angiogenic therapy (Avastin). After three weeks, patients began chemoradiation and continued Avastin. Patients were imaged at baseline, after Avastin monotherapy, and during combined therapy. Imaging modalities were CuATSM‐PET (tumor hypoxia), FLT‐ PET (proliferation), dynamic FLT‐PET (FLT kinetics) and dynamic contrast‐enhanced CT (perfusion). Mean SUV was calculated from PET data and dynamic FLT data were analyzed for kinetics with a two‐compartment, four‐parameter model. DCE‐CT data were analyzed with GE Advantage software. Paired t‐tests were used to evaluate tumor response and mean imaging values were correlated with Pearsonˈs R.Results: After Avastin monotherapy, significant decreases were measured in CuATSM_SUV (p=0.05), FLT_SUV (p<0.01), FLT_Ki (p<0.01), and CT_Enhancement (p<0.01). During combined therapy, further decreases were measured in CuATSM_SUV and FLT_SUV (p=0.05, p<0.001). Across the study, significant correlations were found between CuATSM_SUV and CT_BloodVolume (R=0.72), CT_BloodFlow (R=0.59), and FLT_K1 (R=0.53). Additionally, FLT_Ki was significantly correlated to FLT_SUV (R=0.80) and CT_Enhancement (R=0.50) Conclusions: Multimodality imaging has been used to identify clinically relevant tumor characteristics over the course of therapy. Significant decrease in tumor proliferation suggests effective combination of Avastin and chemoradiotherapy, and FLT imaging endpoints could potentially be used to optimize combined therapy. Decrease in hypoxia was also measured, and given the established prognostic value of hypoxia, mid‐therapy hypoxic status is another potential therapeutic endpoint. Decrease in CT_Enhancement after Avastin may indicate reduction in vascular permeability, and correlation between CuATSM_SUV and perfusion‐related parameters such as FLT_K1, CT_BloodVolume, and CT_BloodFlow suggests further importance of vascular status in effectiveness of combined therapies. As outcome data becomes available, these imaging biomarkers could eventually be used to personalize delivery of combined therapy.Study supported in part by Genentech
SU‐E‐E‐11: Results from the Tomotherapy Daily QA Using the Rotational Therapy Phantom
Authors: Jaradat H , Freeman K 
Published: November 2011

Purpose: In this study we will present results from the daily QA program used to monitor the tomotherapy machine over a period of eight months. Methods: The daily QA uses the Rotational Therapy Phantom, Gammex 507 (RTP). The RTP system allows for checking the rotational output, energy, gantry speed, gantry position, MLC‐Gantry position synchrony and beam profile constancies. All of these tests are done within one five‐minute procedure to check these metrics on the tomotherapy machine. The measurements are done using two ion chambers connected to the TomoElectrometer in rate collection mode. Daily QA data is analyzed using the Rotational Therapy Phantom Software (RTPS) to compare the constancy of these metrics relative to a standard set. The Daily QA protocol runs a dynamic MLC, five‐identical‐rotation procedure with a period of 40 seconds per rotation. Results: Measurements are taken using the TomoElectrometer with a sample time of 200ms, because the procedure utilizes dynamic MLC and rotational gantry, the procedure allows the software to detect variations in the output rate, energy constancies, gantry speed, position and MLC/Gantry position synchrony at the same rate. This work will present examples of these variations including evidence on gantry position/MLC asynchrony of up to 2 seconds. This corresponds to 18 degrees or 2.55 projections. Conclusions: Using the RTPS for daily QA on tomotherapy system shows that the system can run with up to 2 seconds (18 degrees) asynchrony between the MLC and the gantry position. This 18 degree discrepancy between the plan and the actual delivery could result in significant clinical outcome for a wide range of treatment sites, such as prostate, H&N, Lung and Brain treatments.Work is currently being done to expand the application of the RTPS to be applicable on the Varian and Elekta rotational therapy modalities.Kennith Freeman is an employee of Gammex Inc.