bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐14: A Feasibility Study of Using Modified AP Proton Beam for Post‐Operative Pancreatic Cancer Therapy
Authors: Ding X , Witztum A , Kenton O , Younan F , Dormer J , Kremmel E , Lin H , Liu H , Tang S , Both S , Kassaee A , Avery S 
Published: July 2014

Purpose:Due to the unpredictability of bowel gas movement, the PA beam direction is always favored for robust proton therapy in post‐operative pancreatic cancer treatment. We investigate the feasibility of replacing PA beam with a modified AP beam to take the bowel gas uncertainty into account.Methods:Nine post‐operative pancreatic cancer patients treated with proton therapy (5040cGy, 28 fractions) in our institution were randomly selected. The original plan uses PA and lateral direction passive‐scattering proton beams. Beam weighting is about 1:1. All patients received weekly verification CTs to assess the daily variations(total 17 verification CTs). The PA direction beam was replaced by two other groups of AP direction beam. Group AP: takes 3.5% range uncertainty into account. Group APmod: compensates the bowel gas uncertainty by expanding the proximal margin to 2cm more. The 2cm margin was acquired from the average bowel diameter in from 100 adult abdominal CT scans near pancreatic region (+/‐ 5cm superiorly and inferiorly). Dose Volume Histograms(DVHs) of the verification CTs were acquired for robustness study.Results:Without the lateral beam, Group APmod is as robust as Group PA. In Group AP, more than 10% of iCTV D98/D95 were reduced by 4–8%. LT kidney and Liver dose robustness are not affected by the AP/PA beam direction. There is 10% of chance that RT kidney and cord will be hit by AP proton beam due to the bowel gas. Compared to Group PA, APmod plan reduced the dose to kidneys and cord max significantly, while there is no statistical significant increase in bowel mean dose.Conclusion:APmod proton beam for the target coverage could be as robust as the PA direction without sacrificing too much of bowel dose. When the AP direction beam has to be selected, a 2cm proximal margin should be considered.
SU‐E‐T‐36: An Investigation of the Margin From CTV to PTV Using Retraction Method for Cervical Carcinoma
Authors: Wu D , Chen J , Hao Y , Liao C , Huang Y , Mo Y , Wei Y 
Published: July 2014

Purpose:This work employs the retraction method to compute and evaluate the margin from CTV to PTV based on the influence of target dosimetry of setup errors during cervical carcinoma patients treatment.Methods:Sixteen patients with cervical cancer were treated by Elekta synergy and received a total of 305 KV‐CBCT images. The iso‐center of the initial plans were changed according to the setup errors to simulate radiotherapy and then recalculated the dose distribution using leaf sequences and MUs for individual plans. The margin from CTV to PTV will be concluded both by the method of retracting (Fixed the PTV of the original plan, and retract PTV a certain distance defined as simulative organization CTVnx. The minimum distance value from PTV to CTVnx which get specified doses, namely guarantee at least 99% CTV volume can receive the dose of 95%, is the margin CTV to PTV we found) and the former formula method.Results:(1)The setup errors of 16 patients in X, Y and Z directions were(1.13±2.94) mm,(−1.63±7.13) mm,(−0.65±2.25) mm. (2) The distance between CTVx and PTV was 5, 9 and 3mm in X, Y and Z directions According to 2.5+0.7σ. (3) Transplantation plans displayed 99% of CTVx10‐ CTVx7 and received 95% of prescription dose, but CTVx6‐ CTVx3 departed from standard of clinic.In order to protect normal tissues, we selected 7mm as the minimum value of the margin from CTV to PTV.Conclusion:We have test an retraction method for the margin from CTV to PTV evaluation. The retraction method is more reliable than the formula method for calculating the margin from the CTV to the PTV, because it represented practice of treatment, and increasing a new method in this field.
SU‐E‐T‐41: Analysis of GI Dose Variability Due to Intrafraction Setup Variance
Authors: Phillips J , Wolfgang J 
Published: July 2014

Purpose:Proton SBRT (stereotactic body radiation therapy) can be an effective modality for treatment of gastrointestinal tumors, but limited in practice due to sensitivity with respect to variation in the RPL (radiological path length). Small, intrafractional shifts in patient anatomy can lead to significant changes in the dose distribution. This study describes a tool designed to visualize uncertainties in radiological depth in patient CT's and aid in treatment plan design.Methods:This project utilizes the Shadie toolkit, a GPU‐based framework that allows for real‐time interactive calculations for volume visualization. Current SBRT simulation practice consists of a serial CT acquisition for the assessment of inter‐ and intra‐fractional motion utilizing patient specific immobilization systems. Shadie was used to visualize potential uncertainties, including RPL variance and changes in gastric content. Input for this procedure consisted of two patient CT sets, contours of the desired organ, and a pre‐calculated dose. In this study, we performed rigid registrations between sets of 4DCT's obtained from a patient with varying setup conditions. Custom visualizations are written by the user in Shadie, permitting one to create color‐coded displays derived from a calculation along each ray.Results:Serial CT data acquired on subsequent days was analyzed for variation in RPB and gastric content. Specific shaders were created to visualize clinically relevant features, including RPL (radiological path length) integrated up to organs of interest. Using pre‐calculated dose distributions and utilizing segmentation masks as additional input allowed us to further refine the display output from Shadie and create tools suitable for clinical usage.Conclusion:We have demonstrated a method to visualize potential uncertainty for intrafractional proton radiotherapy. We believe this software could prove a useful tool to guide those looking to design treatment plans least insensitive to motion for patients undergoing proton SBRT in the GI tract.
SU‐E‐T‐42: Analysis of Spatial Trade‐Offs for a Spinal SRS Case
Authors: Viulet T , Blanck O , Schlaefer A 
Published: July 2014

Purpose:To study whether the spatially limited relaxation of dose constraints could improve the target coverage for spinal lesions. Particularly, to illustrate that the localized relaxation of areas identified as restricting can be used to consider critical trade‐offs.Methods:We used an in‐house planning system based on constrained optimization to explore potential spatial dose distributions. A three‐dimensional visualization of the iso‐dose surfaces and the dose bounds allowed studying the location of limiting constraints. An interactive tool was used to set optimization objectives and to selectively relax constraints. Considering a spinal tumor treatment which resulted in a relapse close to the spinal cord we studied trade‐offs that could increase the coverage of the original GTV. Starting from a plan similar to the original treatment our goal was to cover the GTV facing the spinal cord and including the area of recurrence. Subsequently, different trade‐offs are analyzed. For comparison, a global relaxation of the bounds was studied.Results:We identified that the upper bounds on spinal cord, esophagus and PTV are partially limiting for the optimization. Relaxing limiting constraints in lateral directions, the upper bound in part of the GTV, and on the surface of the spine increased the coverage of the selected region from 5.6 to 87.4 % with 97.3% coverage of the recurrence. Only the explicitly relaxed areas received higher doses. In comparison, relaxing the upper bounds globally yielded 94.5% and 98.5% coverage for the selected and the recurrence regions, respectively. However, hot spots extended even outside the PTV and the 8.5 Gy iso‐dose cut substantially deeper into the spinal cord.Conclusion:Highlighting the constraining regions helped to quickly identify possible trade‐offs. Spatially localized relaxation allows more fine grained compromises when planning cases where conflicting goals prevent solutions close to the original goals.
SU‐E‐T‐47: Application of the Repair‐Misrepair‐Fixation RBE Model to Describe the Results of High Resolution Proton Irradiation Cell Survival Experiments
Authors: Peeler C , Taleei R , Guan F , Bronk L , Grosshans D , Mirkovic D , Titt U , Mohan R 
Published: July 2014

Purpose:To develop a system to rapidly and accurately calculate RBE with the repair‐misrepair‐fixation (RMF) model for proton therapy data sets and to evaluate its effectiveness in modeling RBE for cell survival experiments performed with the H460 cell line for a range of proton LET.Methods:A system for using the Monte Carlo Damage Simulation (MCDS) software with high performance computing was developed. Input for the MCDS software for a range of proton energies in increments of 0.1 MeV was generated and simulated. The output data were then used to determine doseaveraged quantities for the RMF model based on equivalently binned proton energy spectra. The method was applied to calculate RBE at 50% survival for experimental cell survival data. Experimental data were obtained using a system which allowed for the accumulation of cell survival data at known values of dose‐averaged proton LETs at a range of doses. RBE was calculated based directly on a Cs‐137 reference experiment and, additionally, according to fitted values of the θ and κ terms of the RMF model.Results:Dose‐averaged RMF model quantities were calculated using the HPC system. Compared to experimental RBE determined using a Cs‐137 irradiation as a reference, the RBE from the model differed by at most 49%. RBE based on the fitted values of θ and κ differed by at most 18% for the highest LET.Conclusion:A system for rapidly generating data necessary to calculate RBE with the RMF model has been developed. For the H460 cell line, the RMF model could not reproduce the experimentally determined RBE based solely on the photon reference data. Fitting of the θ and κ terms of the RMF model indicates that their values increase for proton LET exceeding approximately 10 keV/µm.NIH Program Project Grant P01CA021239
SU‐E‐T‐48: Automated Quality Assurance for XML Controlled Linacs
Authors: Valdes G , Morin O , Pouliot J , Chuang C 
Published: July 2014

Purpose:To automate routine imaging QA procedures so that complying with TG 142 and TG 179 can be efficient and reliable.Methods:Two QA tests for a True Beam Linac were automatized. A Winston Lutz test as described by Lutz et al1 using the Winston Lutz test kit from BrainLab, Germany and a CBCT Image Quality test as described in TG 179 using the EMMA phantom, Siemens Medical Physics, Germany were performed in our True Beam. For each QA procedure tested, a 3 step paradigm was used. First, the data was automatically acquired using True Beam Developer Mode and XML scripting. Second, the data acquired in the first step was automatically processed using in‐home grown Matlab GUIs. Third, Machine Learning algorithms were used to automatically classify the processed data and reports generated.Results:The Winston Luzt test could be performed by an experienced medical physicist in 29.0 ± 8.0 min. The same test, if automated using our paradigm, could be performed in 3.0 ± 0.1 min. In the same lieu, time could be substantially saved for image quality tests. In this case, the amount of time saved will depend on the phantoms used and the initial localization method. Additionally, machine learning algorithms could automatically identify the roots of the problems if any and possibly help reduce machine down time.Conclusion:Modern linear accelerators are equipped with advanced 2D and 3D imaging that are used for patient alignment substantially improving IGRT protocols. However, this extra complexity exponentially increases the number of QA tests needed. Using the new paradigm described above, not only bare minimum but best practice QA programs could be implemented with the same manpower.This work is supported by Varian, Palo Alto, CA
SU‐E‐T‐52: Beam Data Comparison for 20 Linear Accelerators in One Network
Authors: LoSasso T , Lim S , Tang G , Chan M , Li J , Obcemea C , Song Y , Ma R , Yang G , Xiong W , Huang D , Burman C , Mechalakos J , Hunt M 
Published: July 2014

Purpose:To compare photon beam data for the 20 Varian linear accelerators (TrueBeam, iX, and EX models) in use at five centers in the same network with the intent to model with one set of beam data in Eclipsec.Methods:Varian linear accelerators, TrueBeam (3), 21 EX, iX, and Trilogy (14), and 6 EX (3), installed between 1999 and 2014 have their 6 MV and 15 MV x‐ray beams reevaluated. Full commissioning, including output factors (St), percent depth doses (PDD), and off‐axis profiles, was recently performed for a TrueBeam with a cc04 ion chamber in an IBA Blue phantom. Similarly, a subset of beam data for each of the other accelerators was measured recently as follows: for 3×3, 10×10, and 30×30 cm2 field sizes, flatness and penumbra (80–20%) were measured at dmax and 10 cm depths, PDD were measured at 10 and 20 cm depths, and St were measured at 5 cm depth. Measurement results for all machines were compared.Results:For 15 high‐energy (6 and 15 MV) and 3 low‐energy machines (6MV only): 1) PDD agreed within 1.4% at 10 and 20 cm depths; 2) penumbra agreed within 1.0 mm at dmax and 10 cm depths; 3) flatness was within 1.3% at dmax and 10 cm depths; and 4) with exception of the three low energy machines, output factors were within 1.1% and 0.5% for 3×3 and 30×30 cm2, respectively. Measurement uncertainty, not quantified here, accounts for some of these differences.Conclusion:Measured beam data from 15 high‐energy Varian linacs are consistent enough that they can be classified using one beam data set in Eclipse. Two additional high‐energy machines are removed from this group until their data are further confirmed. Three low‐energy machines will be in a separate class based upon differences in output factors (St).
SU‐E‐T‐53: Benchmarking a Monte Carlo Model for Patient Plane Leakage Calculations of Low Energy 6MV Unique Linacs
Authors: Constantin M , Sawkey D , Johnsen S , Hsu H 
Published: July 2014

Purpose:To validate the physics parameters of a Monte Carlo model for patient plane leakage calculations on the 6MV Unique linac by comparing the simulations against IEC patient plane leakage measurements. The benchmarked model can further be used for shielding design optimization, to predict leakage in the proximity of intended treatment fields, reduce the system weight and cost, and improve components reliability.Methods:The treatment head geometry of the Unique linac was simulated in Geant4 (v9.4.p02 with “Opt3” standard electromagnetic physics list) based on CAD drawings of all collimation and shielding components projected from the target to the area within 2m from isocenter. A 4×4m2 scorer was inserted 1m from the target in the patient plane and multiple phase space files were recorded by performing a 40‐node computing cluster simulation on the EC2 cloud. The photon energy fluence was calculated relative to the value at isocenter for a 10×10cm2 field using 10×10mm2 bins. Tungsten blocks were parked accordingly to represent MLC120. The secondary particle contamination to patient plane was eliminated by “killing” those particles prior to the primary collimator entrance using a “kill‐plane”, which represented the upper head shielding components not being modeled. Both IEC patient‐plane leakage and X/Y‐jaws transmission were simulated.Results:The contribution of photons to energy fluence was 0.064% on average, in excellent agreement with the experimental data available at 0.5, 1.0, and 1.5m from isocenter, characterized by an average leakage of 0.045% and a maximum leakage of 0.085%. X‐ and Y‐jaws transmissions of 0.43% and 0.44% were found in good agreement with measurements of 0.48% and 0.43%, respectively.Conclusion:A Geant4 model based on energy fluence calculations for the 6MV Unique linac was created and validated using IEC patient plane leakage measurements. The “kill‐plane” has effectively eliminated electron contamination to patient plane in these simulations.
SU‐E‐T‐243: MonteCarlo Simulation Study of Polymer and Radiochromic Gel for Three‐Dimensional Proton Dose Distribution
Authors: Park M , Jung H , Kim G , Ji Y , Kim K , Park S 
Published: July 2014

Purpose:To estimate the three dimensional dose distributions in a polymer gel and a radiochromic gel by comparing with the virtual water phantom exposed to proton beams by applying Monte Carlo simulation.Methods:The polymer gel dosimeter is the compositeness material of gelatin, methacrylic acid, hydroquinone, tetrakis, and distilled water. The radiochromic gel is PRESAGE product. The densities of polymer and radiochromic gel were 1.040 and 1.0005 g/cm3, respectively. The shape of water phantom was a hexahedron with the size of 13 × 13 × 15 cm3. The proton beam energies of 72 and 116 MeV were used in the simulation. Proton beam was directed to the top of the phantom with Z‐axis and the shape of beam was quadrangle with 10 × 10 cm2 dimension. The Percent depth dose and the dose distribution were evaluated for estimating the dose distribution of proton particle in two gel dosimeters, and compared with the virtual water phantom.Results:The Bragg‐peak for proton particles in two gel dosimeters was similar to the virtual water phantom. Bragg‐peak regions of polymer gel, radiochromic gel, and virtual water phantom were represented in the identical region (4.3 cm) for 72 MeV proton beam. For 116 MeV proton beam, the Bragg‐peak regions of polymer gel, radiochromic gel, and virtual water phantom were represented in 9.9, 9.9 and 9.7 cm, respectively. The dose distribution of proton particles in polymer gel, radiochromic gel, and virtual water phantom was approximately identical in the case of 72 and 116 MeV energies. The errors for the simulation were under 10%.Conclusion:This work indicates the evaluation of three dimensional dose distributions by exposing proton particles to polymer and radiochromic gel dosimeter by comparing with the water phantom. The polymer gel and the radiochromic gel dosimeter show similar dose distributions for the proton beams.
SU‐E‐T‐250: New IMRT Sequencing Strategy: Towards Intra‐Fraction Plan Adaptation for the MR‐Linac
Authors: Kontaxis C , Bol G , Lagendijk J , Raaymakers B 
Published: July 2014

Purpose:To develop a new sequencer for IMRT planning that during treatment makes the inclusion of external factors possible and by doing so accounts for intra‐fraction anatomy changes. Given a real‐time imaging modality that will provide the updated patient anatomy during delivery, this sequencer is able to take these changes into account during the calculation of subsequent segments.Methods:Pencil beams are generated for each beam angle of the treatment and a fluence optimization is performed. The pencil beams, together with the patient anatomy and the above optimal fluence form the input of our algorithm. During each iteration the following steps are performed: A fluence optimization is done and each beam's fluence is then split to discrete intensity levels. Deliverable segments are calculated for each one of these. Each segment's area multiplied by its intensity describes its efficiency. The most efficient segment among all beams is then chosen to deliver a part of the calculated fluence and the dose that will be delivered by this segment is calculated. This delivered dose is then subtracted from the remaining dose. This loop is repeated until 90% of the dose has been delivered and a final segment weight optimization is performed to reach full convergence.Results:This algorithm was tested in several prostate cases yielding results that meet all clinical constraints. Quality assurance was performed on Delta4 and film phantoms for one of these prostate cases and received clinical acceptance after passing both gamma analyses with the 3%/3mm criteria.Conclusion:A new sequencing algorithm was developed to facilitate the needs of intensity modulated treatment. The first results on static anatomy confirm that it can calculate clinical plans equivalent to those of the commercially available planning systems. We are now working towards 100% dose convergence which will allow us to handle anatomy deformations.This work is financially supported by Elekta AB, Stockholm, Sweden.
SU‐E‐T‐251: Novel Multi‐Stage Stereotactic Radiosurgery Technique for Large Cerebral Arteriovenous Malformations Using the Gammaknife System
Authors: Ding C , Hrycushko B , Jiang S , Whitworth L , Timmerman R 
Published: July 2014

Purpose:To develop a multi‐stage stereotactic radiosurgery delivery technique for large intracranial arteriovenous malformations (AVM) using the Gammaknife treatment platform.Methods:Eleven patients having large (>15 cm3) cerebral AVMs were selected for this study. AVMs were contoured and divided into 3‐8 subtargets with volumes ranging from 3–7 cm3. Each subtarget is to be treated sequentially in 1–4 week intervals between stages. The prescription dose was 16–20 Gy depending on the target volume. Gammaknife plans were retrospectively generated to treat the entire AVM target with a simulated Extend frame system that can reposition patients within a 1mm accuracy. The coordinates of each shot from the initial plan were extracted based on the shot position within the Extend frame system. Shots were then grouped based on their relative position to individual subtarget contours to generate stage‐specific plans. The delivery time of each shot of a subtarget was corrected for decay of each stage to generate the same dose distribution as that of the original plan for the entire AVM. Conformality and dose‐volume analysis was performed to evaluate the PITV (ratio of prescription isodose volume to target volume), R50 (ratio of 50% isodose volume to target volume), and V12Gy (percentage of brain volume receiving 12Gy or greater).Results:The total accumulated dose for the multi‐staged treatments was shown to be equivalent to the initial plan of the entire AVM target. The Gammaknife plans resulted in an average of 95.8%±0.6 PTV coverage with a PITV of 1.06±0.07. The resulting V12Gy and R50 dose spillage values were 4.2%±2.0 and 3.2±0.4, respectively.Conclusion:With the Extend frame, the Gammaknife system can deliver a multi‐staged conformal dose to treat large AVMs. Target dose coverage and conformality as well as normal brain toxicity measures were shown to be similar compared to that of a single fraction treatment.