bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐256: Optimizing the Combination of Targeted Radionuclide Therapy Agents Using a Multi‐Scale Patient‐Specific Monte Carlo Dosimetry Platform
Authors: Besemer A , Titz B , Grudzinski J , Weichert J , Hall L , Bednarz B 
Published: July 2014

Purpose:Combination targeted radionuclide therapy (TRT) is appealing because it can potentially exploit different mechanisms of action from multiple radionuclides as well as the variable dose rates due to the different radionuclide half‐lives. The work describes the development of a multiobjective optimization algorithm to calculate the optimal ratio of radionuclide injection activities for delivery of combination TRT.Methods:The ‘diapeutic’ (diagnostic and therapeutic) agent, CLR1404, was used as a proof‐of‐principle compound in this work. Isosteric iodine substitution in CLR1404 creates a molecular imaging agent when labeled with I‐124 or a targeted radiotherapeutic agent when labeled with I‐125 or I‐131. PET/CT images of high grade glioma patients were acquired at 4.5, 24, and 48 hours post injection of 124I‐CLR1404. The therapeutic 131I‐CLR1404 and 125ICLR1404 absorbed dose (AD) and biological effective dose (BED) were calculated for each patient using a patient‐specific Monte Carlo dosimetry platform. The optimal ratio of injection activities for each radionuclide was calculated with a multi‐objective optimization algorithm using the weighted sum method. Objective functions such as the tumor dose heterogeneity and the ratio of the normal tissue to tumor doses were minimized and the relative importance weights of each optimization function were varied.Results:For each optimization function, the program outputs a Pareto surface map representing all possible combinations of radionuclide injection activities so that values that minimize the objective function can be visualized. A Pareto surface map of the weighted sum given a set of user‐specified importance weights is also displayed. Additionally, the ratio of optimal injection activities as a function of the all possible importance weights is generated so that the user can select the optimal ratio based on the desired weights.Conclusion:Multi‐objective optimization of radionuclide injection activities can provide an invaluable tool for maximizing the dosimetric benefits in multi‐radionuclide combination TRT.BT, JG, and JW are affiliated with Cellectar Biosciences which owns the licensing rights to CLR1404 and related compounds.
SU‐E‐T‐258: Parallel Optimization of Beam Configurations for CyberKnife Treatments
Authors: Viulet T , Blanck O , Schlaefer A 
Published: July 2014

Purpose:The CyberKnife delivers a large number of beams originating at different non‐planar positions and with different orientation. We study how much the quality of treatment plans depends on the beams considered during plan optimization. Particularly, we evaluate a new approach to search for optimal treatment plans in parallel by running optimization steps concurrently.Methods:So far, no deterministic, complete and efficient method to select the optimal beam configuration for robotic SRS/SBRT is known. Considering a large candidate beam set increases the likelihood to achieve a good plan, but the optimization problem becomes large and impractical to solve. We have implemented an approach that parallelizes the search by solving multiple linear programming problems concurrently while iteratively resampling zero weighted beams. Each optimization problem contains the same set of constraints but different variables representing candidate beams. The search is synchronized by sharing the resulting basis variables among the parallel optimizations. We demonstrate the utility of the approach based on an actual spinal case with the objective to improve the coverage.Results:The objective function is falling and reaches a value of 5000 after 49, 31, 25 and 15 iterations for 1, 2, 4, and 8 parallel processes. This corresponds to approximately 97% coverage in 77%, 59%, and 36% of the mean number of iterations with one process for 2, 4, and 8 parallel processes, respectively. Overall, coverage increases from approximately 91.5% to approximately 98.5%.Conclusion:While on our current computer with uniform memory access the reduced number of iterations does not translate into a similar speedup, the approach illustrates how to effectively parallelize the search for the optimal beam configuration. The experimental results also indicate that for complex geometries the beam selection is critical for further plan optimization.
SU‐E‐T‐259: Particle Swarm Optimization in Radial Dose Function Fitting for a Novel Iodine‐125 Seed
Authors: Wu X , Duan J , Popple R , Cardan R , Huang M , Benhabib S , Shen S , Brezovich I 
Published: July 2014

Purpose:To determine the coefficients of bi‐ and tri‐exponential functions for the best fit of radial dose functions of the new iodine brachytherapy source: Iodine‐125 Seed AgX‐100.Methods:The particle swarm optimization (PSO) method was used to search for the coefficients of the biand tri‐exponential functions that yield the best fit to data published for a few selected radial distances from the source. The coefficients were encoded into particles, and these particles move through the search space by following their local and global best‐known positions. In each generation, particles were evaluated through their fitness function and their positions were changed through their velocities. This procedure was repeated until the convergence criterion was met or the maximum generation was reached. All best particles were found in less than 1,500 generations.Results:For the I‐125 seed AgX‐100 considered as a point source, the maximum deviation from the published data is less than 2.9% for bi‐exponential fitting function and 0.2% for tri‐exponential fitting function. For its line source, the maximum deviation is less than 1.1% for bi‐exponential fitting function and 0.08% for tri‐exponential fitting function.Conclusion:PSO is a powerful method in searching coefficients for bi‐exponential and tri‐exponential fitting functions. The bi‐ and tri‐exponential models of Iodine‐125 seed AgX‐100 point and line sources obtained with PSO optimization provide accurate analytical forms of the radial dose function. The tri‐exponential fitting function is more accurate than the bi‐exponential function.
SU‐E‐T‐260: Pediatric Total Body Irradiation Calculations and In‐Vivo Dosimetry Using Diodes and OSLD' s
Authors: Chungbin S , Fatyga M 
Published: July 2014

Purpose:To verify that a photon total body irradiation (TBI) calculation method scales properly from adult to pediatric dimensions and to determine TBI in‐vivo dosimetry correction factors for diodes and optically stimulated luminescent dosimeters (OSLD' s).Methods:TBI technique used is 400 SAD 18 MV opposed laterals with beam spoiler. Water bags are used to supplement narrower lateral dimensions for patient treatments. To verify that dose calculations scale properly with decreasing dimensions, CAX doses were measured and compared to calculations for different rectangular phantom geometries: (L=length(cm), H=height(cm), d=depth(cm)): L(30)xH(30) (d=3‐25), L(30)xH(12)(d=2–20), L(13)xH(13) (d=5–13), L(30)x(H=10–40) d=15, L(30–150) x H(10) (d=15). In infant geometry, measured off axis “leg” dose (L(30)xH(2.5–10.6), d=7)) was compared to CAX (“body” L(30)xH(10)(d=7) adjacent to “leg”). Entrance and exit doses were measured with surface diodes, diodes with buildup, OSLD' s, as well as ion chambers for comparison. Correction factors ((ion chamber CAX dose)/(in vivo dose)) were calculated for surface diodes, diodes with buildup, OSLD' s, and ion chamber.Results:All rectangular phantom measurements agree with calculated within 2.5%. For L(30)xH(30), L(30)xH(12), L(13)xH(13), L(30)x(H=10–40) and L(30–80)xH(10) agreement was within 1%. For the infant geometry, the ratio of leg dose to CAX varies from 0.956 (h=2.5) to 0.995 (h=10.6). The range of in‐vivo dosimetry entrance+exit to CAX dose correction factors varied by dosimeter (diode: 0.883–1.015, surface diode: 1.008–1.214, ion chamber: 0.924–1.084, OSLD: 0.920–1.106).Conclusion:TBI calculations scaled properly to pediatric dimensions. In‐vivo dosimetry with various detectors demonstrated similar trends with different magnitudes. OSLD measurements agreed well with ion chamber measurements.
SU‐E‐T‐261: Plan Quality Assurance of VMAT Using Fluence Images Reconstituted From Log‐Files
Authors: Katsuta Y , Shimizu E , Matsunaga K , Majima K 
Published: July 2014

Purpose:A successful VMAT plan delivery includes precise modulations of dose rate, gantry rotational and multi‐leaf collimator (MLC) shapes. One of the main problem in the plan quality assurance is dosimetric errors associated with leaf‐positional errors are difficult to analyze because they vary with MU delivered and leaf number. In this study, we calculated integrated fluence error image (IFEI) from log‐files and evaluated plan quality in the area of all and individual MLC leaves scanned.Methods:The log‐file reported the expected and actual position for inner 20 MLC leaves and the dose fraction every 0.25 seconds during prostate VMAT on Elekta Synergy. These data were imported to in‐house software that developed to calculate expected and actual fluence images from the difference of opposing leaf trajectories and dose fraction at each time. The IFEI was obtained by adding all of the absolute value of the difference between expected and actual fluence images corresponding.Results:In the area all MLC leaves scanned in the IFEI, the average and root mean square (rms) were 2.5 and 3.6 MU, the area of errors below 10, 5 and 3 MU were 98.5, 86.7 and 68.1 %, the 95 % of area was covered with less than error of 7.1 MU. In the area individual MLC leaves scanned in the IFEI, the average and rms value were 2.1 – 3.0 and 3.1 – 4.0 MU, the area of errors below 10, 5 and 3 MU were 97.6 – 99.5, 81.7 – 89.5 and 51.2 – 72.8 %, the 95 % of area was covered with less than error of 6.6 – 8.2 MU.Conclusion:The analysis of the IFEI reconstituted from log‐file was provided detailed information about the delivery in the area of all and individual MLC leaves scanned.
SU‐E‐T‐262: Planning for Proton Pencil Beam Scanning (PBS): Applications of Gradient Optimization for Field Matching
Authors: Lin H , Kirk M , Zhai H , Ding X , Liu H , Hill‐Kayser C , Lustig R , Tochner Z , Deville C , Vapiwala N , McDonough J , Both S 
Published: July 2014

Purpose:To propose the gradient optimization(GO) approach in planning for matching proton PBS fields and present two commonly used applications in our institution.Methods:GO is employed for PBS field matching in the scenarios that when the size of the target is beyond the field size limit of the beam delivery system or matching is required for beams from different angles to either improve the sparing of important organs or to pass through a short and simple beam path. Overlap is designed between adjacent fields and in the overlapped junction, the dose was optimized such that it gradually decreases in one field and the decrease is compensated by increase from another field. Clinical applications of this approach on craniospinal irradiation(CSI) and whole pelvis treatment were presented. Mathematical model was developed to study the relationships between dose errors, setup errors and junction lengths.Results:Uniform and conformal dose coverage to the entire target volumes was achieved for both applications using GO approach. For CSI, the gradient matching (6.7cm junction) between fields overcame the complexity of planning associated with feathering match lines. A slow dose gradient in the junction area significantly reduced the sensitivity of the treatment to setup errors. For whole pelvis, gradient matching (4cm junction) between posterior fields for superior target and bilateral fields for inferior target provided dose sparing to organs such as bowel, bladder and rectum. For a setup error of 3 mm in longitudinal direction from one field, mathematical model predicted dose errors of 10%, 6% and 4.3% for junction length of 3, 5 and 7cm.Conclusion:This GO approach improves the quality of the PBS treatment plan with matching fields while maintaining the safety of treatment delivery relative to potential misalignments.
SU‐E‐T‐264: Preliminary Results On New Optically Stimulated Luminescent Materials for Proton Therapy Dosimetry
Authors: Doull B , Zheng Y , Yukihara E 
Published: July 2014

Purpose:The objective of this work is to test the premise that luminescence materials with less under‐response to proton beams can be identified by testing their dose response to low‐LET radiation. The goal is to develop new Optically Stimulated Luminescence (OSL) materials with improved response for proton therapy dosimetry.Methods:We first measured the dose response of new OSL materials, synthesized in our laboratory, to low‐LET radiation (beta rays from a 9 0Sr/9 0Y source) and selected two materials having different OSL saturation characteristics and good dosimetric properties, namely MgB4O7:Ce,Li and MgO:Li. Commercial Al2O3:C was also used for comparison. These materials were then irradiated at several depths along a pristine proton beam. The luminescence responses of the materials, relative to the entrance response, were compared with the depth dose profile measured by a multiple‐layer ion chamber.Results:The OSL signals of MgB4O7:Ce,Li and MgO:Li were characterized for signal stability, dose response, and response to a clinical proton beam. The materials were also compared with the commercial Al2O3:C. The signals from both MgB4O7:Ce,Li and MgO:Li were relatively stable after a one day delay following irradiation. The low‐LET dose response of the materials showed that, over the dose range investigated (up to ∼800 Gy), MgB4O7:Ce,Li did not saturate, whereas MgO:Li and Al2O3:C saturated at doses of ∼100 Gy. MgB4O7:Ce,Li showed less underresponse to proton beams than MgO:Li and Al2O3:C.Conclusion:In general the material with the highest saturation doses for low‐LET radiation (MgB4O7:Ce,Li) showed the least under‐response to proton beams, which suggests that it may be possible to develop better OSL materials for proton dosimetry if the dose response can be controlled during synthesis. Nevertheless, the degree in which the response to proton beams can be controlled remains to be determined.The research is funded by the Oklahoma Center for the Advancement of Science and Technology (OCAST), project number HR12‐055.
SU‐E‐T‐265: Presage Thin Sheet Dosimeter Characterization
Authors: Dumas M , Rakowski J 
Published: July 2014

Purpose:To quantify the sensitivity and stability of the Presage dosimeter in sheet form for different concentrations of chemicals and for a diverse range of clinical photon energies.Methods:Presage polymer dosimeters are formulated to investigate and optimize their sensitivity and stability. The dosimeter is composed of clear polyurethane base, leucomalachite green reporting dye, and bromoform radical initiator in 1mm thick sheets. The chemicals are well mixed together, cast in an aluminum mold, and left to cure at 60 psi for a minimum of 2 days. Dosimeter response will be characterized at multiple energies including Co‐60, 6 MV, 15 MV, 50 kVp, and 250 kVp. The dosimeters are read by an Epson 10000 XL scanner at 800 dpi, 2^16 bit depth. Red component images are analyzed with ImageJ.Results:Analysis of optical density verse dose for Co‐60 energies indicates that the bromoform containing Presage was able to quantify dose from 0 to 300 Gy, with saturation beyond 300 Gy. Initial results show two regions of linear response, 0–100 Gy and 150–300 Gy. The 150–300 Gy region has a sensitivity of 0.0024 net OD/Gy. Further results on other energies are still in progress.Conclusions:This work shows the potential for use of thin sheets of Presage dosimeter as a dosimeter capable of being analyzed with a flatbed scanner.
SU‐E‐T‐266: Proton PBS Plan Design and Robustness Evaluation for Head and Neck Cancers
Authors: Liang X , Tang S , Zhai H , Kirk M , Kalbasi A , Lin A , Ahn P , Tochner Z , McDonough J , Both S 
Published: July 2014

Purpose:To describe a newly designed proton pencil beam scanning (PBS) planning technique for radiotherapy of patients with bilateral oropharyngeal cancer, and to assess plan robustness.Methods:We treated 10 patients with proton PBS plans using 2 posterior oblique field (2F PBS) comprised of 80% single‐field uniform dose (SFUD) and 20% intensity‐modulated proton therapy (IMPT). All patients underwent weekly CT scans for verification. Using dosimetric indicators for both targets and organs at risk (OARs), we quantitatively compared initial plans and verification plans using student t‐tests. We created a second proton PBS plan for each patient using 2 posterior oblique plus 1 anterior field comprised of 100% SFUD (3F PBS). We assessed plan robustness for both proton plan groups, as well as a photon volumetric modulated arc therapy (VMAT) plan group by comparing initial and verification plans.Results:The 2F PBS plans were not robust in target coverage. D98% for clinical target volume (CTV) degraded from 100% to 96% on average, with maximum change Δ D98% of −24%. Two patients were moved to photon VMAT treatment due to insufficient CTV coverage on verification plans. Plan robustness was especially weak in the low‐anterior neck. The 3F PBS plans, however, demonstrated robust target coverage, which was comparable to the VMAT photon plan group. Doses to oral cavity were lower in the Proton PBS plans compared to photon VMAT plans due to no lower exit dose to the oral cavity.Conclusion:Proton PBS plans using 2 posterior oblique fields were not robust for CTV coverage, due to variable positioning of redundant soft tissue in the posterior neck. We designed 3‐field proton PBS plans using an anterior field to avoid long heterogeneous paths in the low neck. These 3‐field proton PBS plans had significantly improved plan robustness, and the robustness is comparable to VMAT photon plans.
SU‐E‐T‐269: Quality Assurance of Spine Volumetric Modulated Arc Therapy with Flattening Filter Free Beams Using Gafchromic EBT3 Films
Authors: Choi Y , Cho B , Kwak J , Ahn S , Choi E , Kim J , Song S , Yoon S , Kim Y , Kim S , Park J 
Published: July 2014

Purpose:We implemented the Gafchromic film‐based patient specific QA of volumetric modulated arc therapy (VMAT) with flattening‐filter free (FFF) beams for spine metastases and validated the accuracy of fast arc delivery.Methods:EBT3 films and a homemade cylindrical QA phantom were employed for dosimetric verification of VMATs. For 14 FFF VMAT plans (10 with 10‐MV FFF beams and 4 with 6‐MV FFF beams), the doses were recalculated on the phantom and delivered by a TrueBeam STx accelerator equipped with a high‐definition 120 leaf MLC. The EBT3 films were scanned using an Epson 10000XL scanner through the FilmQA Pro software. All the irradiated film images were converted to dose map using a calibration response curve. The resulting dose map of film measurement was compared with treatment plan and evaluated using gamma analysis with dose tolerance of 2% within 2 mm. In addition, the point‐dose measurement in the phantom using an ion chamber was evaluated as a reference in a ratio of measured and planned doses.Results:The gamma pass rates averaged over all FFF plans for composite‐field measurements were 96.0 ± 3.6% (88.9%–99.5%). When adopting a tolerance level of 3% – 3 mm, the gamma pass rates were improved with the ranges from 98% to 100%. In addition, dose profiles and dose distributions showed that spinal cord was protected by the rapid dose fall‐off and by delivering the treatment with high precision. In point‐dose measurements, the average differences between the measured and planned doses were 0.5% ± 1.0% of the prescription dose.Conclusion:We demonstrated that Gafchromic EBT3 film would be an effective patient‐specific QA tool, especially for VMAT of spine SBRT with treatment of small fields and highly gradient dose distributions. The results of film QA verified that the dosimetric accuracy of spine SBRT utilizing RapidArc with FFF beams in our institution is reliable.
SU‐E‐T‐275: Radiobiological Evaluation of Intensity Modulated Radiotherapy Treatment for Locally Advanced Head and Neck Squamous Cell Carcinomas
Authors: Rekha Reddy B. , Ravikumar M. , Tanvir Pasha C.R , Anil Kumar M.R , Pyakuryal A , Varatharaj C. , Narayanasamy Ganesh 
Published: July 2014

Purpose:To evaluate the radiobiological outcome of Intensity Modulated Radiotherapy Treatment (IMRT) for locally advanced head and neck squamous cell carcinomas using HART (Histogram Analysis in Radiation Therapy; J Appl Clin Med Phys 11(1): 137–157, 2010) program and compare with the clinical outcomes.Methods:We have treated 20 patients of stage III and IV HNSCC Oropharynx and hypopharynx with accelerated IMRT technique and concurrent chemotherapy. Delineation of tumor and normal tissues were done using Danish Head and Neck Cancer Group (DAHANCA) contouring guidelines and radiotherapy was delivered to a dose of 70Gy in 35 fractions to the primary and involved lymph nodes, 63Gy to intermediate risk areas and 56 Gy to lower risk areas, Monday to Saturday, 6 Days/week using 6 MV Photons with an expected overall treatment time of 6 weeks. The TCP and NTCP's were calculated from the dose‐volume histogram (DVH) statistics using the Poisson Statistics (PS) and JT Lyman models respectively and theResultwas correlated with clinical outcomes of the patients with mean follow up of 24 months. Results:Using HART program, the TCP (0.89± 0.01) of primary tumor and the NTCP for parotids (0.20±0.12), spinal cord (0.05±0.01), esophagus (0.30±0.2), mandible (0.35±0.21), Oral cavity (0.37±0.18), Larynx (0.30±0.15) were estimated and correlated with clinical outcome of the patients.Conclusion:Accelerated IMRT with Chemotherapy is a clinical feasible option in the treatment of locally advanced HNSCC with encouraging initial tumour response and acceptable acute toxicities. The correlation between the clinical outcomes and radiobiological model estimated parameters using HART programs are found to be satisfactory.
SU‐E‐T‐277: Raystation Electron Monte Carlo Commissioning and Clinical Implementation
Authors: Allen C , Sansourekidou P , Pavord D 
Published: July 2014

Purpose:To evaluate the Raystation v4.0 Electron Monte Carlo algorithm for an Elekta Infinity linear accelerator and commission for clinical use.Methods:A total of 199 tests were performed (75 Export and Documentation, 20 PDD, 30 Profiles, 4 Obliquity, 10 Inhomogeneity, 55 MU Accuracy, and 5 Grid and Particle History). Export and documentation tests were performed with respect to MOSAIQ (Elekta AB) and RadCalc (Lifeline Software Inc). Mechanical jaw parameters and cutout magnifications were verified. PDD and profiles for open cones and cutouts were extracted and compared with water tank measurements. Obliquity and inhomogeneity for bone and air calculations were compared to film dosimetry. MU calculations for open cones and cutouts were performed and compared to both RadCalc and simple hand calculations. Grid size and particle histories were evaluated per energy for statistical uncertainty performance. Acceptability was categorized as follows: performs as expected, negligible impact on workflow, marginal impact, critical impact or safety concern, and catastrophic impact of safety concern.Results:Overall results are: 88.8% perform as expected, 10.2% negligible, 2.0% marginal, 0% critical and 0% catastrophic. Results per test category are as follows: Export and Documentation: 100% perform as expected, PDD: 100% perform as expected, Profiles: 66.7% perform as expected, 33.3% negligible, Obliquity: 100% marginal, Inhomogeneity 50% perform as expected, 50% negligible, MU Accuracy: 100% perform as expected, Grid and particle histories: 100% negligible. To achieve distributions with satisfactory smoothness level, 5,000,000 particle histories were used. Calculation time was approximately 1 hour.Conclusion:Raystation electron Monte Carlo is acceptable for clinical use. All of the issues encountered have acceptable workarounds. Known issues were reported to Raysearch and will be resolved in upcoming releases.