bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐J‐209: Geometric Distortion at 3T in a Commercial 4D MRI‐Compatible Phantom
Authors: Fatemi‐Ardekani A , Wronski M , Kim A , Stanisz G , Sarfehnia A , Keller B 
Published: June 2015

Purpose:There are very few commercial 4D phantoms that are marketed as MRI compatible. We are evaluating one such commercial phantom, made to be used with an MRI‐Linear accelerator. The focus of this work is to characterize the geometric distortions produced in this phantom at 3T using 3 clinical MR pulse sequences.Methods:The CIRS MRI‐Linac Dynamic Phantom (CIRSTM) under investigation in this study consists of a softwaredriven moving tumour volume within a thorax phantom body and enables dose accumulation by placing a dosimeter within the tumour volume. Our initial investigation is to evaluate the phantom in static mode prior to examining its 4D capability. The water‐filled thorax phantom was scanned using a wide‐bore Philips 3T Achieva MRI scanner employing a Thoracic xl coil and clinical 2D T1W FFE, 2D T1W TSE and 3D T1W TFE pulse sequences. Each of the MR image sets was rigidly fused with a reference CT image of the phantom employing a rigid registration with 6 degrees of freedom. Geometric distortions between the MR and CT image sets were measured in 3 dimensions at selected points along the periphery of the distortion grid embedded within the phantom body (11.5, 7.5 and 3 cm laterally, ant/post and sup/inf of magnetic isocenter respectively).Results:The maximal measured geometric distortions between the MR and reference CT points of interest were 0.9, 1.8 and 1.3 mm in the lateral, anteriorposterior and cranio‐caudal directions, respectively. For all 3 spatial dimensions, the maximal distortions occurred for the FFE pulse sequence. Maximal distortions for the 2D FFE, 2D TSE and 3D TFE sequences were 1, 0.7 and 1.8 mm, respectively.Conclusion:Our initial static investigation of this phantom shows minimal geometric distortions at 3T along the periphery of the embedded grid.CIRS has provided us with a phantom at no charge for evaluation at 3 Tesla.
SU‐E‐J‐212: MR Diffusion Tensor Imaging for Assessment of Tumor and Normal Brain Tissue Responses of Juvenile Pilocytic Astrocytoma Treated by Proton Therapy
Authors: Hou P , Park P , Li H , Zhu X , Mahajan A , Grosshans D 
Published: June 2015

Purpose:Diffusion tensor imaging (DTI) can measure molecular mobility at the cellular level, quantified by the apparent diffusion coefficient (ADC). DTI may also reveal axonal fiber directional information in the white matter, quantified by the fractional anisotropy (FA). Juvenile pilocytic astrocytoma (JPA) is a rare brain tumor that occurs in children and young adults. Proton therapy (PT) is increasingly used in the treatment of pediatric brain tumors including JPA. However, the response of both tumors and normal tissues to PT is currently under investigation. We report tumor and normal brain tissue responses for a pediatric case of JPA treated with PT assessed using DTI.Methods:A ten year old male with JPA of the left thalamus received passive scattered PT to a dose of 50.4 Gy (RBE) in 28 fractions. Post PT, the patient has been followed up in seven years. At each follow up, MRI imaging including DTI was performed to assess response. MR images were registered to the treatment planning CT and the GTV mapped onto each MRI. The GTV contour was then mirrored to the right side of brain through the patient's middle line to represent normal brain tissue. ADC and FA were measured within the ROIs.Results:Proton therapy can completely spare contra lateral brain while the target volume received full prescribed dose. From a series of MRI ADC images before and after PT at different follow ups, the enhancement corresponding to GTV had nearly disappeared more than 2 years after PT. Both ADC and FA demonstrate that contralateral normal brain tissue were not affect by PT and the tumor volume reverted to normal ADC and FA values.Conclusion:DTI allowed quantitative evaluation of tumor and normal brain tissue responses to PT. Further study in a larger cohort is warranted.
SU‐E‐J‐218: Novel Validation Paradigm of MRI to CT Deformation of Prostate
Authors: Padgett K , Pirozzi S , Nelson A , Stoyanova R , Piper J , Horvat M , Dogan N , Pollack A 
Published: June 2015

Purpose:Deformable registration algorithms are inherently difficult to characterize in the multi‐modality setting due to a significant differences in the characteristics of the different modalities (CT and MRI) as well as tissue deformations. We present a unique paradigm where this is overcome by utilizing a planning‐MRI acquired within an hour of the planning‐CT serving as a surrogate for quantifying MRI to CT deformation by eliminating the issues of multi‐modality comparisons.Methods:For nine subjects, T2 fast‐spin‐echo images were acquired at two different time points, the first several weeks prior to planning (diagnostic‐MRI) and the second on the same day as the planning‐CT (planning‐MRI). Significant effort in patient positioning and bowel/bladder preparation was undertaken to minimize distortion of the prostate in all datasets. The diagnostic‐MRI was rigidly and deformably aligned to the planning‐CT utilizing a commercially available deformable registration algorithm synthesized from local registrations. Additionally, the quality of rigid alignment was ranked by an imaging physicist. The distances between corresponding anatomical landmarks on rigid and deformed registrations (diagnostic‐MR to planning‐CT) were evaluated.Results:It was discovered that in cases where the rigid registration was of acceptable quality the deformable registration didn't improve the alignment, this was true of all metrics employed. If the analysis is separated into cases where the rigid alignment was ranked as unacceptable the deformable registration significantly improved the alignment, 4.62mm residual error in landmarks as compared to 5.72mm residual error in rigid alignments with a p‐value of 0.0008.Conclusion:This paradigm provides an ideal testing ground for MR to CT deformable registration algorithms by allowing for inter‐modality comparisons of multi‐modality registrations. Consistent positioning, bowel and bladder preparation may Result in higher quality rigid registrations than typically achieved which limits the impact of deformable registrations. In this study cases where significant differences exist, deformable registrations provide significant value.This work was funded by an NIH grant# 1R01CA189295‐01. PI: Alan Pollack, MD PhD. “MRI IMAGING AND GENETIC SIGNATURES TO MANAGE PROSTATE CANCER OVERDIAGNOSIS”
SU‐E‐J‐223: A BOLD Contrast Imaging Sequence to Evaluate Oxygenation Changes Due to Breath Holding for Breast Radiotherapy: A Pilot Study
Authors: Adamson J , Chang Z , Cai J , Palta M , Horton J , Yin F , Blitzblau R 
Published: June 2015

Purpose:To develop a robust MRI sequence to measure BOLD breath hold induced contrast in context of breast radiotherapy.Methods:Two sequences were selected from prior studies as candidates to measure BOLD contrast attributable to breath holding within the breast: (1) T2* based Gradient Echo EPI (TR/TE = 500/41ms, flip angle = 60°), and (2) T2 based Single Shot Fast Spin Echo (SSFSE) (TR/TE = 3000/60ms). We enrolled ten women post‐lumpectomy for breast cancer who were undergoing treatment planning for whole breast radiotherapy. Each session utilized a 1.5T GE MRI and 4 channel breast coil with the subject immobilized prone on a custom board. For each sequence, 1–3 planes of the lumpectomy breast were imaged continuously during a background measurement (1min) and intermittent breath holds (20–40s per breath hold, 3–5 holds per sequence). BOLD contrast was quantified as correlation of changes in per‐pixel intensity with the breath hold schedule convolved with a hemodynamic response function. Subtle motion was corrected using a deformable registration algorithm. Correlation with breath‐holding was considered significant if p<0.001.Results:The percentage of the breast ROI with positive BOLD contrast measured by the two sequences were in agreement with a correlation coefficient of R=0.72 (p=0.02). While both sequences demonstrated areas with strong BOLD response, the response was more systematic throughout the breast for the SSFSE (T2) sequence (% breast with response in the same direction: 51.2%±0.7% for T2* vs. 68.1%±16% for T2). In addition, the T2 sequence was less prone to magnetic susceptibility artifacts, especially in presence of seroma, and provided a more robust image with little distortion or artifacts.Conclusion:A T2 SSFSE sequence shows promise for measuring BOLD contrast in the context of breast radiotherapy utilizing a breath hold technique. Further study in a larger patient cohort is warranted to better refine this novel technique.
SU‐E‐T‐88: Acceptance Testing and Commissioning Measurements of a Newly Released InCiseâ„¢ Multileaf Collimator for CyberKnife M6â„¢ System
Authors: Huq M Saiful , Ozhasoglu C , Jang S , Hwang M , Heron D , Lalonde R 
Published: June 2015

Purpose:Accuray recently released a new collimator, the InCise™ Multileaf Collimator (MLC), for clinical use with the CyberKnife M6™ System. This work reports the results of acceptance testing and commissioning measurements for this collimator.Methods:The MLC consists of 41 pairs of 2.5 mm wide leaves projecting a clinical maximum field size of 110 mm × 97.5 mm at 800 mm SAD. The leaves are made of tungsten, 90 mm in height and tilted by 0.5 degree. The manufacturer stated leaf positioning accuracy and reproducibility are 0.5 mm and 0.4 mm respectively at 800 mm SAD. The leaf over‐travel is 100% with full interdigitation capability. Acceptance testing included, but are not limited to, the verification of the specifications of various parameters described above, leakage measurements and end‐to‐end tests. Dosimetric measurements included, but not limited to, measurements of output factors, open beam profiles, tissue‐phantom ratios, beam flatness and symmetry, and patient specific QA.Results:All measurements were well within the manufacturer specifications. The values of output factors ranged from 0.804 (smallest field size of 7.6 mm × 7.5 mm) to 1.018 (largest field size of 110.0 mm × 97.5 mm). End‐to‐end test results for the various tracking modes are: Skull (0.27mm), fiducial (0.16mm), Xsight Spine (0.4mm), Xsight Lung (0.93 mm) and Synchrony (0.43mm). Measured maximum and average leakage was 0.37% and 0.3%, respectively. Patient‐specific QA measurements with chamber were all within 5% absolute dose agreement, and film measurements all passed 2%/2mm gamma evaluation for more than 95% of measurement points.Conclusion:The presented results are the first set of data reported on the InCise™ MLC. The MLC proved to be very reliable and is currently in clinical use.
SU‐E‐T‐110: An Investigation On Monitor Unit Threshold and Effects On IMPT Delivery in Proton Pencil Beam Planning System
Authors: Syh J , Ding X , Syh J , Patel B , Rosen L , Wu H 
Published: June 2015

Purpose:An approved proton pencil beam scanning (PBS) treatment plan might not be able to deliver because of existed extremely low monitor unit per beam spot. A dual hybrid plan with higher efficiency of higher spot monitor unit and the efficacy of less number of energy layers were searched and optimized. The range of monitor unit threshold setting was investigated and the plan quality was evaluated by target dose conformity.Methods:Certain limitations and requirements need to be checks and tested before a nominal proton PBS treatment plan can be delivered. The plan needs to be met the machine characterization, specification in record and verification to deliver the beams. Minimal threshold of monitor unit, e.g. 0.02, per spot was set to filter the low counts and plan was re‐computed. Further MU threshold increment was tested in sequence without sacrificing the plan quality. The number of energy layer was also alternated due to elimination of low count layer(s).Results:Minimal MU/spot threshold, spot spacing in each energy layer and total number of energy layer and the MU weighting of beam spots of each beam were evaluated. Plan optimization between increases of the spot MU (efficiency) and less energy layers of delivery (efficacy) was adjusted. 5% weighting limit of total monitor unit per beam was feasible. Scarce spreading of beam spots was not discouraging as long as target dose conformity within 3% criteria.Conclusion:Each spot size is equivalent to the relative dose in the beam delivery system. The energy layer is associated with the depth of the targeting tumor. Our work is crucial to maintain the best possible quality plan. To keep integrity of all intrinsic elements such as spot size, spot number, layer number and the carried weighting of spots in each layer is important in this study.
SU‐E‐T‐118: Analysis of Variability and Stability Between Two Water Tank Phantoms Utilizing Water Tank Commissioning Procedures
Authors: Roring J , Saenz D , Cruz W , Papanikolaou N , Stathakis S 
Published: June 2015

Purpose:The commissioning criteria of water tank phantoms are essential for proper accuracy and reproducibility in a clinical setting. This study outlines the results of mechanical and dosimetric testing between PTW MP3‐M water tank system and the Standard Imaging Doseview 3D water tank system.Methods:Measurements were taken of each axis of movement on the tank using 30 cm calipers at 1, 5, 10, 50, 100, and 200 mm for accuracy and reproducibility of tank movement. Dosimetric quantities such as percent depth dose and dose profiles were compared between tanks using a 6 MV beam from a Varian 23EX LINAC. Properties such as scanning speed effects, central axis depth dose agreement with static measurements, reproducibility of measurements, symmetry and flatness, and scan time between tanks were also investigated.Results:Results showed high geometric accuracy within 0.2 mm. Central axis PDD and in‐field profiles agreed within 0.75% between the tanks. These outcomes test many possible discrepancies in dose measurements across the two tanks and form a basis for comparison on a broader range of tanks in the future.Conclusion:Both 3D water scanning phantoms possess a high degree of spatial accuracy, allowing for equivalence in measurements regardless of the phantom used. A commissioning procedure when changing water tanks or upon receipt of a new tank is nevertheless critical to ensure consistent operation before and after the arrival of new hardware.
SU‐E‐T‐123: Anomalous Altitude Effect in Permanent Implant Brachytherapy Seeds
Authors: Watt E , Spencer DP , Meyer T 
Published: June 2015

Purpose:Permanent seed implant brachytherapy procedures require the measurement of the air kerma strength of seeds prior to implant. This is typically accomplished using a well‐type ionization chamber. Previous measurements (Griffin et al., 2005; Bohm et al., 2005) of several low‐energy seeds using the air‐communicating HDR 1000 Plus chamber have demonstrated that the standard temperature‐pressure correction factor, PTP, may overcompensate for air density changes induced by altitude variations by up to 18%. The purpose of this work is to present empirical correction factors for two clinically‐used seeds (IsoAid ADVANTAGE™ 103Pd and Nucletron selectSeed 125I) for which empirical altitude correction factors do not yet exist in the literature when measured with the HDR 1000 Plus chamber.Methods:An in‐house constructed pressure vessel containing the HDR 1000 Plus well chamber and a digital barometer/thermometer was pumped or evacuated, as appropriate, to a variety of pressures from 725 to 1075 mbar. Current measurements, corrected with PTP, were acquired for each seed at these pressures and normalized to the reading at ‘standard’ pressure (1013.25 mbar).Results:Measurements in this study have shown that utilization of PTP can overcompensate in the corrected current reading by up to 20% and 17% for the IsoAid Pd‐103 and the Nucletron I‐125 seed respectively. Compared to literature correction factors for other seed models, the correction factors in this study diverge by up to 2.6% and 3.0% for iodine (with silver) and palladium respectively, indicating the need for seed‐specific factors.Conclusion:The use of seed specific altitude correction factors can reduce uncertainty in the determination of air kerma strength. The empirical correction factors determined in this work can be applied in clinical quality assurance measurements of air kerma strength for two previously unpublished seed designs (IsoAid ADVANTAGE™ 103Pd and Nucletron selectSeed 125I) with the HDR 1000 Plus well chamber.
SU‐E‐T‐124: Anthropomorphic Phantoms for Confirmation of Linear Accelerator Based Small Animal Irradiation
Authors: Perks J , Lucero S , Benedict S 
Published: June 2015

Purpose:To document the support of radiobiological small animal research by a modern radiation oncology facility. This study confirms that a standard, human use linear accelerator can cover the range of experiments called for by researchers performing animal irradiation. A number of representative, anthropomorphic murine phantoms were made. The phantoms confirmed the small field photon and electron beams dosimetry validated the use of the linear accelerator for rodents.Methods:Laser scanning a model, CAD design and 3D printing produced the phantoms. The phantoms were weighed and CT scanned to judge their compatibility to real animals. Phantoms were produced to specifically mimic lung, gut, brain, and othotopic lesion irradiations. Each phantom was irradiated with the same protocol as prescribed to the live animals. Delivered dose was measured with small field ion chambers, MOS/FETs or TLDs.Results:The density of the phantom material compared to density range across the real mice showed that the printed material would yield sufficiently accurate measurements when irradiated. The whole body, lung and gut irradiations were measured within 2% of prescribed doses with A1SL ion chamber. MOSFET measurements of electron irradiations for the orthotopic lesions allowed refinement of the measured small field output factor to better than 2% and validated the immunology experiment of irradiating one lesion and sparing another.Conclusion:Linacs are still useful tools in small animal bio‐radiation research. This work demonstrated a strong role for the clinical accelerator in small animal research, facilitating standard whole body dosing as well as conformal treatments down to 1cm field. The accuracy of measured dose, was always within 5%. The electron irradiations of the phantom brain and flank tumors needed adjustment; the anthropomorphic phantoms allowed refinement of the initial output factor measurements for these fields which were made in a large block of solid water.
SU‐E‐T‐125: Application of Jaw‐Tracking Function in VMAT for Upper Thoracic Esophageal Cancer
Authors: Zhang W , Chen J , Zhai T , Yan L , Chen C 
Published: June 2015

Purpose:To explore the effect of the Jaw‐tracking with RapidArc(JT‐RapidArc) plans for upper thoracic esophageal cancer.Methods:Treatment planning was designed by using RapidArc and JT‐RapidArc techniques for 11 consecutive patients. The dose‐volume histogram parameters of PTV and the organs at risk(OAR), conformity index(CI), heterogeneity index(HI), low dose volume of normal tissue(B‐P) and monitor units(MUs) were compared between the different techniques.Results:JT‐RapidArc plans provided the better coverage of PTV1(64) D98 and HI(P<0.05), lower MLD, D2 of PTV1(64) and PTV2(54), but no statistically difference in CI(P>0.05), which comparison with RapidArc plans. Plans with JT‐ RapidArc had lower Lung of V5, V10, V13, V20, V30, MLD(P<0.05); heart of V20, MLD(P<0.05); and B‐P of V5, V10, V15, V20, V30(P<0.05); but no significantly different in Spinal cord and SC‐PRV as compared with RapidArc plans. JT‐RapidArc plans increaseed the MUs by 1%(P>0.05) as compared with RapidArc plans.Conclusion:All of the plans had met the requirements of clinical dosimetry. JT‐RapidArc plans as compared with RapidArc plans, showing better part of target coverage, part of OARS(lung and heart) and heart and B‐P sparing, which MUs was slightly increased.This work was sponsored by Shantou University Medical College Clinical Research Enhancement Initiative(NO.201424)
SU‐E‐T‐157: CARMEN: A MatLab‐Based Research Platform for Monte Carlo Treatment Planning (MCTP) and Customized System for Planning Evaluation
Authors: Baeza J.A. , Ureba A. , Jimenez‐Ortega E. , Barbeiro A.R. , Lagares J.I. , Plaza A. Leal 
Published: June 2015

Purpose:Although there exist several radiotherapy research platforms, such as: CERR, the most widely used and referenced; SlicerRT, which allows treatment plan comparison from various sources; and MMCTP, a full MCTP system; it is still needed a full MCTP toolset that provides users complete control of calculation grids, interpolation methods and filters in order to “fairly” compare results from different TPSs, supporting verification with experimental measurements.Methods:This work presents CARMEN, a MatLab‐based platform including multicore and GPGPU accelerated functions for loading RT data; designing treatment plans; and evaluating dose matrices and experimental data.CARMEN supports anatomic and functional imaging in DICOM format, as well as RTSTRUCT, RTPLAN and RTDOSE. Besides, it contains numerous tools to accomplish the MCTP process, managing egs4phant and phase space files.CARMEN planning mode assist in designing IMRT, VMAT and MERT treatments via both inverse and direct optimization. The evaluation mode contains a comprehensive toolset (e.g. 2D/3D gamma evaluation, difference matrices, profiles, DVH, etc.) to compare datasets from commercial TPS, MC simulations (i.e. 3ddose) and radiochromic film in a user‐controlled manner.Results:CARMEN has been validated against commercial RTPs and well‐established evaluation tools, showing coherent behavior of its multiple algorithms. Furthermore, CARMEN platform has been used to generate competitive complex treatment that has been published in comparative studies.Conclusion:A new research oriented MCTP platform with a customized validation toolset has been presented. Despite of being coded with a high‐level programming language, CARMEN is agile due to the use of parallel algorithms. The wide‐spread use of MatLab provides straightforward access to CARMEN's algorithms to most researchers. Similarly, our platform can benefit from the MatLab community scientific developments as filters, registration algorithms etc. Finally, CARMEN arises the importance of grid and filtering control in treatment plan comparison.