bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐458: Instability of Electronic Portal Imaging Device Responses for Intensity Modulated Irradiation
Authors: Yeo I , Jung J , Yi B , Piskulich F , Choi D , Nookala P , Patyal B 
Published: November 2011

Purpose: To investigate the response of electronic portal imaging device (EPID) in integration mode for intensity modulated beams including step‐ and‐shoot (SS) and sliding window (SW) deliveries. Methods: We evaluated EPID dose response measurements of open, SS, and SW irradiations. We designed three beams using 6MV x‐rays with 10×10 cm2 field size. For the SS irradiation, two MLC leaves with 0.5 cm opening outside 10 × 10 cm2 were discontinuously moved by 10 cm during each segmental irradiation among ten segments of the entire delivery. For the SW beam, the same MLC leaves were continuously moved by 10 cm ten times during the delivery. The employment of the same open beam area ensures the same dose irradiation by the three. Monitor units were varied. We additionally investigated the dose linearity of EPID response. We used EPID‐ADU1000 operated with IAS3 system for the integrated acquisition. Results: The SS delivery showed a deviation greater than 2% from the open beam, if a segment employed less than 10 MUs. If it employed greater than 10 MUs, then a deviation less than 1% was observed. The SW delivery showed a maximum deviation of 1.4% at the lowest MU. The open beam irradiation showed linearity within 0.8%, the SW irradiation 1.2%, and the SS irradiation 1.7%. Conclusions: The SS delivery is associated with a greater error than the SW delivery due to beam instability at the start of acquisition and reading loss during MLC movement. Using large monitor units greater than 10 MUs/segment can minimize the deviation for the SS delivery from open beam. The linearity of EPID response to dose was better with the SW delivery than the SS delivery. This study will help understand dosimetric response of EPID for the SS delivery.This study was in part supported by Varian Medical Systems, Inc.
SU‐E‐T‐651: Radiobiological Effect of Target Volume in SBRT of Lung Tumor: Comparison of Treatment Planning Algorithms Between Pencil Beam Algorithm and Monte Carlo Method
Authors: Liu D , Kumar S , Ajlouni M , Jin J , Glide C , Ryu S , Wen N , Siddiqui M , Li H , Fraser C , Movsas B , Chetty I 
Published: November 2011

Purpose: To use equivalent uniform dose (EUD) and tumor control probability (TCP) to retrospectively analyze the radiobiological effect of target volumes in patients with NSCLC planned and treated with Stereotactic Body Radiotherapy (SBRT). Methods: Eighty‐three stage I–II lung cancer patients with 86 lesions treated with SBRT were retrospectively analyzed. For each patient, a Pencil Beam (PB) algorithm‐based treatment plan with a dose regimen of 12 Gy/fraction in 4 fractions was generated. To overcome the known uncertainties of conventional PB algorithm in lung tissue, Monte Carlo (MC) treatment plans were also created in the iPlan (BrainLab) system using the same monitor units derived from the PB‐based plan. Niemierkoˈs EUD and TCP (Poisson model) were computed using different surviving fraction (SF) parameters for each dose calculation algorithm. The radiobiological effects of target volume were analyzed by correlating EUD and TCP with PTV volumes. Results: Mean PTV volume was 39.31 +/− 28.96 cc. The mean PB EUDs were 50.61, 50.60, 50.57 and 50.55 Gy for SF parameter values of 0.36, 0.34, 0.3 and 0.28, compared with MC EUDs 43.97, 43.84, 43.56 and 43.41 Gy. The mean PB TCP values were up to 18% higher than the mean MC TCP. EUDs calculated using both PB and MC were not sensitive to SF parameters, whereas they were for TCP calculation. Overall, MC EUDs were more sensitive to PTV volumes than PB EUDs, measured by Pearson correlation 0.46 vs. 0.07. Larger PTV volume decreased PB TCP values while this was not the case for MC TCP Conclusions: This work demonstrates encouraging evidence that radiobiological effect of target volume and dose calculation algorithm selection is significant in EUD and TCP estimations. Further studies confirming this relationship and relating to treatment outcomes are warranted.Work supported in part by NIH R01 CA106770
SU‐E‐T‐799: Improvement in Chest Wall Dose with Volumetric Modulated Arc Therapy for the Treatment of SBRT Lung Lesions
Authors: Happersett L , Zhang P , Rimner A , Hunt M , Yorke E , Jackson A , Mageras G , Mechalakos J 
Published: November 2011

Purpose: This study evaluates the use of volumetric arc therapy (VMAT) for hypo‐fractionated lung treatments to improve plan conformality and reduce chest wall dose. Methods: Ten patients treated with hypo‐fractionated lung SBRT were retrospectively planned with 270 to 360 degree arc VMAT and results were compared to the 4 – 5 field IMRT plans used for treatment. Prescription doses were 45, 48 or 54Gy in 5, 4 or 3 fractions, respectively. To compare plan quality, various dose‐volume statistics were assessed for the PTV, spinal cord, esophagus, lungs, distal and mainstem bronchi. Conformity index (V(95%Rx)/ V_PTV(95%Rx)) was also evaluated. Monitor units were compared to evaluate plan efficiency. Results: Patient‐averaged PTV D(99%), D(95%), and Dmax were 97.9, 101.2, and 107.8% respectively for VMAT and 98.6, 101.6, and 106.4% respectively for IMRT. Average conformity index was 1.79 for VMAT and 1.96 for IMRT (p<0.01). The most significant normal tissue dose improvement using VMAT was for the chest wall where the average D(30cc) was 24.5 Gy, 19% lower than IMRT (p < 0.01). The average total lung V(20Gy) fell from 5.6% with IMRT to 5% with VMAT but other total lung statistics (V(10Gy), mean dose) were virtually identical. Average contralateral lung mean dose increased with VMAT (1.5 vs 1.1Gy, p<0.01). VMAT and IMRT maximum doses to cord, esophagus, mainstem and distal bronchi did not differ significantly. On average, MU required for VMAT delivery were 32% less than IMRT. Conclusions: PTV coverage and most normal tissue doses were similar for VMAT and IMRT. Conformity index and chest wall D(30cc) improved with VMAT. Although total lung dose was similar for both plans, mean contralateral lung dose on average was higher for VMAT. The VMAT plans showed improved conformality and reduced chest wall D(30cc) at a cost of increased contralateral lung mean dose.Research agreement with Varian Corporation
SU‐E‐T‐864: Beam Orientation Optimization Using Ant Colony Optimization in Intensity Modulated Radiation Therapy
Authors: Pei X , Cao R , Zheng H , Wang J , Wu Y 
Published: November 2011

Purpose: In intensity modulated radiation therapy (IMRT) treatment planning, gantry angles are usually preselected on the basis of experience and intuition. Therefore, getting an appropriate beam configuration needs a very long time. Based on the present situation, the paper puts forward beam orientation optimization using ant colony optimization. Methods: Using ant colony optimization to select the optimal beam configurations, after getting the beam configuration using Conjugate Gradient (CG) algorithm to optimize the intensity profiles. Based on the information of the effect of pencil beam‐let, the algorithm could accelerate to find the global optimal solution. Results: In order to verify the feasibility of the presented algorithm, a simulated and clinical case was tested. Comparison of Dose‐Volume histogram and isodose line between target area and organ at risk, the results showed that the plan quality was improved after optimizing beam configurations. Conclusions: The optimization approach can make treatment planning meet clinical requirements more efficiently, so it has extensive application perspective.Supported by the National Natural Science Foundation under grant No.30900386 and the Anhui Provincial Natural Science Foundation under grant No. 090413095 and 11040606Q55.
SU‐E‐T‐867: Improving the IMRT Plan Quality by Minimizing the Discrepancy Between the Optimized and Segmented Intensity Maps
Authors: Li Yongjie , Tan Youheng 
Published: November 2011

Purpose: In step‐and‐shoot IMRT, beam intensity maps are first optimized, followed by a leaf‐sequencing to translate them into deliverable segments. The differences between the optimized and segmented intensity maps may degrade the deliverable dose distribution. Aiming to decrease this degradation, we present a method to minimize the discrepancy between the optimized and segmented intensity maps. Methods: The general idea of our algorithm is to minimize the sum of absolute differences (SOAD) between the optimized and sequenced intensity maps, similar to the work of Daliang Cao et al (Med. Phys. 2006, 33(4): 859–867). The improvement of our method includes: (1) the initial segment shapes and weights are produced based on the optimized intensity maps with a fast Xia and Verheyˈs leaf sequencing algorithm; (2) the segment weights and shapes are iteratively optimized with a modified gradient conjugate algorithm and genetic algorithm; and (3) the MLC‐dependent leaf transmission and penumbra are both accounted for. Results: For a simulated case involving the left and right lungs and an organ at risk (OAR) surrounded by a C‐shaped planning target volume (PTV), five beams were used. For the five optimized beam intensity maps, the segmented maps were computed using the proposed algorithm. The average computation time was about 17 sec per beam. Both of the dose distributions and dose volume histograms (DVHs) showed the improvements given by our method: more uniform dose distributions for PTV of the both cases, and lower doses for OARs of the clinical case, than that when the MLC‐dependent leaf transmission and penumbra were ignored. Also, the needed numbers of segment and monitor unit were reduced. Conclusions: The proposed method could produce a better segmentation result by improving the dose distributions and reducing the segment number.Funding support: This work was supported by the Program for New Century Excellent Talents in University of China (NCET‐07‐0151) and the Natural Science Foundations of China (61075109, 30730036).
SU‐E‐T‐883: Clinical Application of Monte Carlo for SBRT: Mediastinal Lung
Authors: Grimm J , LaCouture T , Asbell S , Kramer N , Pahlajani N , Chen Y , Xu Q , Croce R , Xue J 
Published: November 2011

Purpose: Treatment planning systems have provided Monte Carlo dose calculations for several years but many physicians are still hesitant to use them clinically due to lack of data. Therefore we recalculated 200 Ray Tracing treatment plans using Monte Carlo with heterogeneity corrections and compared to SBRT dose tolerance limits. Methods: From among these 200 CyberKnife cases, 25 mediastinal lung cases are presented in this study. An extensive literature review obtained 105 published SBRT dose tolerance limits for the mediastinal critical structures aorta, bronchi, esophagus, heart, and trachea. These limits were partitioned into high‐risk and low‐risk categories. The DVH Evaluator software tool was used to generate DVH Risk Maps for these critical structures, which superimpose a) published dose tolerance limits b) unified high‐risk and low‐risk trends and c) published adverse event doses, onto Monte Carlo patient data to assess risk of adverse events. Results: Recalculated treatment plan data is within the expected range of published SBRT dose tolerance limits, providing optimism for clinical use. None of the patients experienced any Grade 3 or higher adverse events. The low‐risk dose tolerance limits were exceeded 22 times in these cases with no severe adverse event, thus helping to validate their safety. Conclusions: The range of doses calculated by Monte Carlo for our historical patient data is compatible with published SBRT dose tolerance limits. SBRT dose tolerance limits should be fine‐tuned by Monte Carlo dose calculations in long‐term statistical followup studies.Disclosure: The first author has developed the DVH Evaluator software.
MO‐D‐BRC‐05: Reducing Megavoltage Cone Beam CT Imaging Dose without Loss of Spatial Resolution Using a Sintered Pixelated Array System
Authors: Breitbach E , Maltz J , Gangadharan B , Bani‐Hashemi A , Anderson C , Bhatia S , Stiles J , Edwards D , Flynn R 
Published: November 2011

Purpose: To demonstrate that megavoltage cone beam CT (MVCBCT) image quality can be significantly improved without increasing imaging dose or reducing spatial resolution for both head‐ and pelvis‐sized volumes. The improvement is achieved with the combination of an imaging beam line (IBL) with a low atomic number electron target and a novel sintered pixelated array (SPA) detector. Methods: Three Siemens Oncor linear accelerators were equipped with an IBL+SPA system, an IBL system with a conventional Kodak Lanex Fast B scintillator (IBL+LFB), and a 6 MV treatment beam line system with an LFB (TBL+LFB). Head‐ and pelvis‐sized phantom images were acquired with all three systems at imaging doses ranging from 2‐60 cGy. Contrast to noise ratio (CNR) and modulation transfer function (MTF) were calculated from the phantom images. Head and neck, prostate, and lung cancer patients were imaged with the three imaging systems at doses ranging from 2–15 cGy. Results: For head‐ and pelvis‐sized phantom images acquired at 5 cGy or above, the CNR average percentage increases for imaging system upgrades from TBL+LFB to IBL+LFB to IBL+SPA were 52% (p < 1E‐7) and 42% (p < 1E‐6), respectively. The MTFs do not change with imaging system by statistically significant percentages. Soft tissue contrast is generally more easily differentiated on IBL+SPA images than TBL+LFB and IBL+LFB in the patient images. Conclusions: Since CNR scales with the square root of imaging dose, each step in the TBL+LFB to IBL+LFB to IBL+SPA upgrade halves the imaging dose required to obtain a given CNR. No statistically significant change in spatial resolution was observed with any upgrade, suggesting that the pixelation of the SPA prevents a loss in spatial resolution. IBL+SPA patient image quality was always better than that of the TBL+LFB system and as good as or better than that of the IBL+LFB system.Sponsored partially by Siemens Oncology Care Systems.
MO‐F‐224‐01: Preparing for Diagnostic ACR Accreditation
Authors: Hernandez D 
Published: November 2011

The American College of Radiology is a professional society and membership organization made up of radiologists, medical physicists, radiation oncologists and nuclear medicine physicians dedicated to making imaging safe and effective. The primary mission of the ACR is to serve patients and society by advancing the science of radiology, improving the quality of patient care, providing continuing education and conducting research for the future of radiology.The ACR has a long history of developing and administrating accreditation programs. The purpose of the various accreditation programs is to set quality standards for practices and to help improve the quality of care given to patients. Accreditation is a peer review process designed to be educational and evaluates personnel qualifications, policies and procedures, equipment performance, effectiveness of quality control measures and the quality of clinical images.The Diagnostic Modality Accreditation Program (DMAP) incorporates all of the ACR accreditation programs with the exception of mammography and radiation oncology. The current programs include Breast Magnetic Resonance Imaging, Breast Ultrasound, Computed Tomography, Magnetic Resonance Imaging, Nuclear Medicine, PET, Stereotactic Breast Biopsy and Ultrasound. While mammography accreditation is required by the FDA under MQSA, facilities seeking ACR accreditation in the other diagnostic modalities have done so voluntarily but for a variety of reasons including the MIPAA mandate requiring the providers of advanced diagnostic services that bill under part B of the Medicare Physician Fee Schedule to be accredited by January 1, 2012 in order to receive technical component reimbursement from Medicare.ACR accreditation is a team process. The medical physicist plays a critical role in the process. A basic understanding of the overall accreditation process is crucial to the achievement of accreditation.Educational Objectives1. Understand the basics of the ACR diagnostic modality accreditation process2. Understand the important roles of the medical physicist in the accreditation process
MO‐F‐110‐06: Developing Deformable 3D Dosimeters: Radiochromic Gels in Latex Balloons
Authors: Walsh A , Battista J , Jordan K 
Published: November 2011

Purpose: To develop radiochromic hydrogels contained in latex balloons as a model for 3D dosimetry in deformable tissue. Methods: Films of latex solution were thermally cured to form thin sheets of transparent rubber. Spheroid, elastic dosimeters were made by filling adaptor tubes sealed at one end by circular rubber sheets with radiochromic hydrogel. These dosimeters were evaluated for optical and mechanical properties and dosimetric performance. Dosimeters were scanned with a fast 3D optical cone beam computed tomography system and dose distributions were reconstructed with isotropic 0.25 mm sized voxels. Gels were irradiated in a water tank to a uniform 3 Gy dose or by an array of 5 mm square beamlets in a grid pattern, with the dosimeter in either relaxed or deformed state. Four percent gelatin gels were employed in the study and dosimeter rigidity was adjustable by filling balloons with more gel. Dosimeters were maintained at a temperature of 20° C throughout the experiments. Deformed gels were allowed to return to the relaxed state for 30 minutes while the radiochromic reaction completed prior to CT scanning. Results: Ferrous ‐ xylenol orange ‐ gelatin hydrogels in latex balloons exhibited similar auto‐oxidation rates and dose sensitivities to samples contained in rigid plastic vessels. The thin‐walled latex balloons provided excellent optical transmission performance allowing accurate dosimetry to within 1 mm of the balloon wall. Uniform irradiations resulted in uniform dose reconstructions for both the relaxed and deformed dosimeters. Deformed gel irradiated with the beamlet array and scanned in relaxed state demonstrated ability of dosimeter to record 3D dose deformation patterns. Conclusions: The elastic properties of transparent films and hydrogels can be combined to produce deformable 3D radiochromic dosimeters compatible with optical CT scanners. These dosimeters can be used to validate multi‐ fraction dose accumulation algorithms based on image warping algorithms.A. Walsh supported by grant: Optimization of Radiation Therapy: Uncertainty Analysis and Strategies for Improvement. Canadian Institutes of Health Research #200403MOP‐128435‐BME‐CEEA‐11379
MO‐F‐220‐02: Imaging Educational Course ‐ Ultrasound Miniaturization
Authors: Smith S 
Published: November 2011

Ultrasound is used more often than any other medical imaging modality because compared to the alternatives it is fast, safe, portable, and inexpensive. Moreover ultrasound has evolved symbiotically with advances in integrated electronics to allow increasingly higher image quality, along with enhanced functional information, like color flow, perfusion, tissue‐strain, and elasticity imaging. It has now become possible to incorporate in compact instruments capabilities that were only available in full size consoles a decade ago.Imagers consist of a sensor that both transmits and receives ultrasound, an electronic beamformer to create focused beams of energy, a mid processor to convert these into grey scale images or functional information, and a display module for output. User interface and control elements complete the units. Three key technologies drive ultrasound miniaturization. First, integrated electronics that allow more processing per volume and per watt are important for both the analog front end as well as the digital beamforming and mid processing units. Second, advances in CPU, and now GPUs, along with simpler software platforms allow many of the functions that used to be done in dedicated hardware to be done in software. Third, the migration of beamforming into the probe shrinks the cable diameter and distributes processing and power consumption.Several examples from recent progress will be used to illustrate these points: the introduction of laptop, tablet, and hand‐held imagers; automatic image optimization to simplify the user experience, and automatic physiological parameter estimates. Recent studies show that in some cases the diagnostic utility of small ultrasound imagers matches results from the larger and more costly consoles. Ultrasound imaging will be adopted in more point‐of‐care and rural settings. Spurred by technological innovations, the ability of ultrasound to address quality, access, and cost issues will likely increase its utilization worldwide.Research supported by General Electric CorporationLearning Objectives:1. Be able to describe the operation of the major parts of an ultrasound imager.2. Appreciate recent advances in probes and microelectronics.3. Understand how engineering specifications impact the diagnostic workflow.
MO‐G‐BRC‐05: Impact of Secondary Particles on Linear Energy Transfer for Biological Treatment Planning in Proton Therapy
Authors: Grassberger C , Paganetti H 
Published: November 2011

Purpose: To assess the contribution of secondary particles to pencil and passively scattered proton beams, in particular to determine the impact on linear energy transfer (LET), a central quantity in biological treatment planning. Methods: Proton Monte Carlo simulations were performed directly in patient geometries considering all primary and secondary particles, including recoils stemming from inelastic nuclear interactions. Simulations were conducted for a prostate and a head&neck case to investigate the impact of different initial proton energies. Results: Examination of the results reveals that secondary protons exhibit LET‐ values up to a factor 10 higher than those of the primary protons in the same region. This causes significant changes to the dose‐averaged LET when including secondary protons, from 50% along the central axis of the beam to >200% in the penumbra. Furthermore the LET‐maximum increases from 12 to 15 MeV/mm. The contribution of recoils (A>3) was observed to be 1.2% in the entrance region of the prostate case, increasing slightly compared to the same beam in a water phantom. The degree of biological damage inflicted by recoils remains hard to quantify, but can be discussed on account of detailed energy spectra of the preeminent particles. Conclusions: These results indicate that secondary protons have a significant influence on LET and should therefore be incorporated into RBE calculations for proton therapy, as well as into radiobiological experiments. The contribution of heavier secondary particles is complex, yet may have an impact on precise measurements of the radiobiological effectiveness (RBE) of protons, especially in the plateau region of high‐energy beams. In addition the LET distributions presented demonstrate the impact of inhomogeneities on the LET and the subtle changes between the LET distributions of passively scattered and actively scanned beams. The latter observation suggests higher RBE variations in active scanning than in passively scattered fields.The project was supported by the Federal Share of program income earned by Massachusetts General Hospital on C06 CA059267, Proton Therapy Research and Treatment Center.