bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐505: CT‐Based Independent Dose Verification for RapidArc Plan as a Secondary Check
Authors: Tachibana H , Kamima T , Takahashi R , Baba H 
Published: July 2014

Purpose:To design and develop a CT‐based independent dose verification for the RapidArc plan and also to show the effectiveness of inhomogeneous correction in the secondary check for the plan.Methods:To compute the radiological path from the body surface to the reference point and equivalent field sizes from the multiple MLC aperture shapes in the RapidArc MLC sequences independently, DICOM files of CT image, structure and RapidArc plan were imported to our in‐house software. The radiological path was computed using a three‐dimensional CT arrays for each segment. The multiple MLC aperture shapes were used to compute tissue maximum ratio and phantom scatter factor using the Clarkson‐method. In this study, two RapidArc plans for oropharynx cancer were used to compare the doses in CT‐based calculation and water‐equivalent phantom calculation using the contoured body structure to the dose in a treatment planning system (TPS).Results:The comparison in the one plan shows good agreement in both of the calculation (within 1%). However, in the other case, the CT‐based calculation shows better agreement compared to the water‐equivalent phantom calculation (CT‐based: ‐2.8% vs. Water‐based: ‐3.8%). Because there were multiple structures along the multiple beam paths and the radiological path length in the CT‐based calculation and the path in the water‐homogenous phantom calculation were comparatively different.Conclusion:RapidArc treatments are performed in any sites (from head, chest, abdomen to pelvis), which includes inhomogeneous media. Therefore, a more reliable CT‐based calculation may be used as a secondary check for the independent verification.
SU‐E‐T‐508: End to End Testing of a Prototype Eclipse Module for Planning Modulated Arc Therapy On the Siemens Platform
Authors: Huang L , Sarkar V , Spiessens S , Rassiah‐Szegedi P , Huang Y , Zhao H , Szegedi M , Salter B 
Published: July 2014

Purpose:The latest clinical implementation of the Siemens Artiste linac allows for delivery of modulated arcs (mARC) using full‐field flattening filter free (FFF) photon beams. The maximum doserate of 2000 MU/min is well suited for high dose treatments such as SBRT. We tested and report on the performance of a prototype Eclipse TPS module supporting mARC capability on the Artiste platform.Method:our spine SBRT patients originally treated with 12/13 field static‐gantry IMRT (SGIMRT) were chosen for this study. These plans were designed to satisfy RTOG0631 guidelines with a prescription of 16Gy in a single fraction. The cases were re‐planned as mARC plans in the prototype Eclipse module using the 7MV FFF beam and required to satisfy RTOG0631 requirements. All plans were transferred from Eclipse, delivered on a Siemens Artiste linac and dose‐validated using the Delta4 system.Results:All treatment plans were straightforwardly developed, in timely fashion, without challenge or inefficiency using the prototype module. Due to the limited number of segments in a single arc, mARC plans required 2‐3 full arcs to yield plan quality comparable to SGIMRT plans containing over 250 total segments. The average (3%/3mm) gamma pass‐rate for all arcs was 98.5±1.1%, thus demonstrating both excellent dose prediction by the AAA dose algorithm and excellent delivery fidelity. Mean delivery times for the mARC plans(10.5±1.7min) were 50‐70% lower than the SGIMRT plans(26±2min), with both delivered at 2000 MU/min.Conclusion:A prototype Eclipse module capable of planning for Burst Mode modulated arc delivery on the Artiste platform has been tested and found to perform efficiently and accurately for treatment plan development and delivered‐dose prediction. Further investigation of more treatment sites is being carried out and data will be presented.
SU‐E‐T‐511: Do Presage 3D Dosimeters Show Dose Fractionation Sensitivity?
Authors: Klawikowski S , Adamovics J , Alqathami M , Benning R , Ibbott G 
Published: July 2014

Purpose:To determine whether Presage 3D polymer dosimeter dose response is sensitive to dose delivery fractionation. Bang gels have demonstrated a dose fractionation related dependence in which a single 400 cGy irradiation would produce a different detector response than four 100 cGy irradiations even if delivered closely in time to one another. Such a fractional dependent response in Presage would be detrimental for measuring multi‐beam irradiations.Methods:Two separate batches of Presage were poured into cuvettes, and a third batch was molded into cuvette shaped blocks. A total of 37 cuvettes/blocks were irradiated in a Cobalt‐60 irradiator to 400 cGy within solid water phantoms in either one, eight, or sixteen fractions. Another group of 15 cuvettes were also kept unirradiated and used for background subtraction between the pre‐scan and post‐scan results. The times between fractional deliveries were held constant at 30 seconds and the Cobalt irradiator dose rate was 49 cGy/min. Each Presage batch has a separate dose sensitivity and therefore fractionation response comparisons were only performed within the same batch. The cuvettes were first pre‐scanned the day prior to irradiation and post‐scanned the day after irradiation. Other than approximately 3 hours warming time prior to each irradiation and optical density measurement the cuvettes were stored in a refrigerator. All cuvettes were stored in a lightless environment throughout manufacturing and testing. The cuvettes’ optical densities were optically measured at 632 nm with a spectrophotometer.Results:No noticeable dose fractionation dependence was detected for any of the three independent batches of Presage for either the eight or sixteen fraction irradiation schemes.Conclusion:These results indicate using Presage 3D dosimeters to measure multi‐beam photon irradiations common in IMRT, Gamma Knife, and Cyberknife treatment delivery schemes.Presage dosimeters are made by and trademarked by Heuris Inc. Skillman, NJ. Dr. John Adamovics is a founder of Heuris Inc.
SU‐E‐T‐514: Simultaneously Determination of Radiation Isocentricity of Gantry, Collimator and Couch Using a Commercial Three‐Dimensional Dosimetry QA Apparatus
Authors: Yan S , Song H , Wu Q 
Published: July 2014

Purpose:Radiation isocentricity is an important benchmark for a LINAC and is typically determined by 3 separate film star‐shots. We developed a technique to simultaneously determine the radiation isocenter of gantry, collimator and couch with a commercial 3D QA apparatus.Methods:The ArcCHECK from SunNuclear was used on two LINACs. It was aligned with room lasers. For gantry rotation, collimator and couch were set to zero and gantry was placed to 0, 49, 213 and 311 degrees. Similarly, a set of collimator/couch angles were chosen with the other two axes at neutral positions. The measured dose matrices were analyzed by an in‐house MATLAB program. For each shot, the central axis was determined by computing the FWHM of the diode arrays. The largest inscribed circle from these central axis lines was used to determine isocenter: the radius as the benchmark of isocentricity and the coordinates of the center as the discrepancy of radiation isocenter to the origin defined by lasers. To validate the method, the couch was shifted by ~5 mm in all three directions and measurements were repeated.Results:The radius of the largest inscribed circle for gantry, collimator and couch are (0.3, 0.5, 0.2) mm for one LINAC and (0.2, 0.3, 0.1) mm for the other, in agreement with the film star‐shots at annual QA. The discrepancies of radiation isocenter are generally within 1 mm, except gantry rotation on one LINAC due to the drift of foot laser. The differences in positions detected are consistent with the intentional predefined shift.Conclusion:We have demonstrated a technique for the simultaneous measurement of gantry, collimator, and couch isocentricity with a set of carefully chosen irradiation parameters based on the specific construction geometry of the 3D detector ArcCheck. This can replace the standard film star‐shots. The future work includes improving operation efficiency.
SU‐E‐T‐515: Field‐In‐Field Compensation Technique Using Multi‐Leaf Collimator to Deliver Total Body Irradiation (TBI) Dose
Authors: Lakeman T , Wang IZ 
Published: July 2014

Purpose:Total body irradiation (TBI) uses large parallel‐opposed radiation fields to suppress the patient's immune system and eradicate the residual cancer cells in preparation of recipient for bone marrow transplant. The manual placement of lead compensators has been used conventionally to compensate for the varying thickness through the entire body in large‐field TBI. The goal of this study is to pursue utilizing the modern field‐in‐field (FIF) technique with the multi‐leaf collimator (MLC) to more accurately and efficiently deliver dose to patients in need of TBI.Method:Treatment plans utilizing the FIF technique to deliver a total body dose were created retrospectively for patients for whom CT data had been previously acquired. Treatment fields include one pair of opposed open large fields (collimator=45°) with a specific weighting and a succession of smaller fields (collimator=90°) each with their own weighting. The smaller fields are shaped by moving MLC to block the sections of the patient which have already received close to 100% of the prescribed dose. The weighting factors for each of these fields were calculated using the attenuation coefficient of the initial lead compensators and the separation of the patient in different positions in the axial plane.Results:Dose‐volume histograms (DVH) were calculated for evaluating the FIF compensation technique. The maximum body doses calculated from the DVH were reduced from the non‐compensated 179.3% to 148.2% in the FIF plans, indicating a more uniform dose with the FIF compensation. All calculated monitor units were well within clinically acceptable limits and exceeded those of the original lead compensation plan by less than 50 MU (only ~1.1% increase).Conclusion:MLC FIF technique for TBI will not significantly increase the beam on time while it can substantially reduce the compensator setup time and the potential risk of errors in manually placing lead compensators.
SU‐E‐T‐517: Analytic Formalism to Compute in Real Time Dose Distributions Delivered by HDR Units
Authors: Pokhrel S , Palaniswaamy G , Rangaraj D , Loyalka S , Izaguirre E 
Published: July 2014

Purpose:Develop an analytical algorithm to compute the dose delivered by Ir‐192 dwell positions with high accuracy using the 3‐dimensional (3D) dose distribution of an HDR source. Using our analytical function, the dose delivered by an HDR unit as treatment progresses can be determined using the actual delivered temporal and positional data of each individual dwell. Consequently, true delivered dose can be computed when each catheter becomes active. We hypothesize that the knowledge of such analytical formulation will allow developing HDR systems with a real time treatment evaluation tool to avoid mistreatments.Methods:In our analytic formulation, the dose is computed by using the full anisotropic function data of the TG 43 formalism with 3D ellipsoidal function. The discrepancy between the planned dose and the delivered dose is computed using an analytic perturbation method over the initial dose distribution. This methodology speeds up the computation because only changes in dose discrepancies originated by spatial and temporal deviations are computed. A dose difference map at the point of interest is obtained from these functions and this difference can be shown during treatment in real time to examine the treatment accuracy.Results:We determine the analytical solution and a perturbation function for the 3 translational 3 rotational, and 1D temporal errors in source distributions. The analytic formulation is a sequence of simple equations that can be processed in any modern computer in few seconds. Because computations are based in an analytical solution, small deviations of the dose when sub‐millimeter positional changes occur can be detected.Conclusions:We formulated an analytical method to compute 4D dose distributions and dose differences based on an analytical solution and perturbations to the original dose. This method is highly accurate and can be
SU‐E‐T‐518: Dosiemtric Impact of Patient Positioning Uncertainty in SBRT Treatments
Authors: Abbas H , Abolfath R , Nath R , Chen Z 
Published: July 2014

Purpose:To investigate the dosimetric impact of patient positioning uncertainties on conventionally fractionated IMRT, hypofractionated and single‐fraction SBRT in light of the recently published AAPM practice guideline on IGRT quality assurance (MPPG2a) .Methods:Treatment plans of three prostate IMRT, three lungs SBRT and three spine SBRT patients were selected for this study. For each patient, uncertainties in isocenter positioning were simulated by displacing the planned isocenter with variable amount in three cardinal directions. The resulting dose distribution was obtained by recalculating the original treatment plan for each displaced isocenter position with the same planned monitor units. Dosimetric impact was assessed by comparing the isocenter‐shifted plan with the original plan with respect to the image‐treatment isocenter coincidence tolerance recommended in MPPG2a (1 mm for SRS and 2 mm for SBRT) .Results:For prostate IMRT, a 2‐mm uncertainty in lateral and superior‐inferior direction had minimal dosimetric impact on either PTV or rectum. However, a 2‐mm deviation in the anterior‐posterior position could Result in up to 8% change in PTV minimum dose (PTVDmin) and up to 7% increase in rectum D25. For lung SBRT, uncertainties of ≤ 2mm had minimal impact on PTV mean dose and mean lung dose. However, up to 21% reduction in PTVDmin was observed with a 2‐mm uncertainty in superior‐inferior direction. For single‐fraction spine SBRT, a 1‐mm uncertainty could cause up to 10% change in PTVDmin and cord maximum dose. Formal statistical analysis for patient‐specific impact over a given course of treatment is being performed .Conclusion:In addition to SRS, single‐fraction SBRT should require isocenter alignment tolerance to be ≤ 1 mm. The 2‐mm positioning tolerance for SBRT may not be sufficient for certain patients. Our analysis can be integrated into the treatment planning system for prospective prediction of the susceptibility of individual plans to setup uncertainties.
SU‐E‐T‐519: Emission of Secondary Particles From a PMMA Phantom During Proton Irradiation: A Simulation Study with the Geant4 Monte Carlo Toolkit
Authors: Lau A , Chen Y , Ahmad S 
Published: July 2014

Purpose:Proton therapy exhibits several advantages over photon therapy due to depth‐dose distributions from proton interactions within the target material. However, uncertainties associated with protons beam range in the patient limit the advantage of proton therapy applications. To quantify beam range, positron‐emitting nuclei (PEN) and prompt gamma (PG) techniques have been developed. These techniques use de‐excitation photons to describe the location of the beam in the patient. To develop a detector system for implementing the PG technique for range verification applications in proton therapy, we studied the yields, energy and angular distributions of the secondary particles emitted from a PMMA phantom.Methods:Proton pencil beams of various energies incident onto a PMMA phantom with dimensions of 5 x 5 x 50 cm3 were used for simulation with the Geant4 toolkit using the standard electromagnetic packages as well as the packages based on the binary‐cascade nuclear model. The emitted secondary particles are analyzed .Results:For 160 MeV incident protons, the yields of secondary neutrons and photons per 100 incident protons were ~6 and ~15 respectively. Secondary photon energy spectrum showed several energy peaks in the range between 0 and 10 MeV. The energy peaks located between 4 and 6 MeV were attributed to originate from direct proton interactions with 12C (~ 4.4 MeV) and 16O (~ 6 MeV), respectively. Most of the escaping secondary neutrons were found to have energies between 10 and 100 MeV. Isotropic emissions were found for lower energy neutrons (<10 MeV) and photons for all energies, while higher energy neutrons were emitted predominantly in the forward direction. The yields of emitted photons and neutrons increased with the increase of incident proton energies.Conclusions:A detector system is currently being developed incorporating the yields, energy and angular distributions of secondary particles from proton interactions obtained from this study.
SU‐E‐T‐522: A Multi‐Isocenter VMAT Technique for Cranio‐Spinal Irradiation
Authors: Aristophanous M , Chi P , Tung S , Pinnix C , Dabaja B 
Published: July 2014

Purpose:Develop a matching VMAT field technique and investigate planning feasibility for treating the entire central nervous system (CNS) using Cranio‐Spinal Irradiation (CSI) .Methods:Two patients diagnosed with acute myeloid leukemia (AML) presented with CNS involvement, received CSI, and were included in this study. The patients were treated with the traditional CSI technique: prone position, opposing lateral brain fields, two posterior fields (upper and lower spine), and 5mm junction shifts to improve dose uniformity. The patients were retrospectively re‐planned using volumetric arc therapy (VMAT). The spine and brain were contoured to create the clinical target volume (CTV) as well as normal tissues including kidneys, lung and heart for optimization. Three isocenters were used for planning: brain, upper and lower spine. The beams were allowed to overlap by approximately 10cm. Entire 360 degree rotations were used for the brain fields and posterior 120 degree arcs were used for the spine fields. The dosimetric coverage of the target between the VMAT and traditional plans was compared, as well as the dose to normal tissues.Results:Both VMAT plans achieved improved dose uniformity in the CTV (standard deviation < 2%), and reduced hot spots (<110%). Dose to the heart was reduced, with the V10 being 12.7% and 28.2%, compared to 44.6% and 50.2%, respectively, for the traditional plan. Dose to the total lung V5 increased for the VMAT plans for both patients (21.6% and 27.8% compared to 12% and 13% respectively). The results for the kidneys were mixed with the mean dose increasing for one patient and decreasing for the other .Conclusion:The efficacy of planning CSI treatments using a matching VMAT technique was demonstrated. The developed technique has the potential to improve dose uniformity to the target while at the same time reduce the risk of under or over dosing the spine.
SU‐E‐T‐523: On the Radiobiological Impact of Lateral Scatter in Proton Beams
Authors: Heuvel F Van den , Deruysscher D 
Published: July 2014

Introduction:In proton therapy, justified concern has been voiced with respect to an increased efficiency in cell kill at the distal end of the Bragg peak. This coupled with range uncertainty is a counter indication to use the Bragg peak to define the border of a treated volume with a critical organ. An alternative is to use the lateral edge of the proton beam, obtaining more robust plans. We investigate the spectral and biological effects of the lateral scatter .Methods:A general purpose Monte Carlo simulation engine (MCNPX 2.7c) installed on a Scientific Linux cluster, calculated the dose deposition spectrum of protons, knock on electrons and generated neutrons for a proton beam with maximal kinetic energy of 200MeV. Around the beam at different positions in the beam direction the spectrum is calculated in concentric rings of thickness 1cm. The deposited dose is converted to a double strand break map using an analytical expression.based on micro dosimetric calculations using a phenomenological Monte Carlo code (MCDS). A strict version of RBE is defined as the ratio of generation of double strand breaks in the different modalities. To generate the reference a Varian linac was modelled in MCNPX and the generated electron dose deposition spectrum was used .Results:On a pristine point source 200MeV beam the RBE before the Bragg peak was of the order of 1.1, increasing to 1.7 right behind the Bragg peak. When using a physically more realistic beam of 10cm diameter the effect was smaller. Both the lateral dose and RBE increased with increasing beam depth, generating a dose deposition with mixed biological effect.Conclusions:The dose deposition in proton beams need to be carefully examined because the biological effect will be different depending on the treatment geometry. Deeply penetrating proton beams generate more biologically effective lateral scatter.
SU‐E‐T‐524: Web‐Based Radiation Oncology Incident Reporting and Learning System (ROIRLS)
Authors: Kapoor R , Palta J , Hagan M , Grover S , Malik G 
Published: July 2014

Purpose:Describe a Web‐based Radiation Oncology Incident Reporting and Learning system that has the potential to improve quality of care for radiation therapy patients. This system is an important facet of continuing effort by our community to maintain and improve safety of radiotherapy.Material andMethods:The VA National Radiation Oncology Program office has embarked on a program to electronically collect adverse events and near miss data of radiation treatment of over 25,000 veterans treated with radiotherapy annually. Software used for this program is deployed on the VAs intranet as a Website. All data entry forms (adverse event or near miss reports, work product reports) utilize standard causal, RT process step taxonomies and data dictionaries defined in AAPM and ASTRO reports on error reporting (AAPM Work Group Report on Prevention of Errors and ASTROs safety is no accident report). All reported incidents are investigated by the radiation oncology domain experts. This system encompasses the entire feedback loop of reporting an incident, analyzing it for salient details, and developing interventions to prevent it from happening again. The operational workflow is similar to that of the Aviation Safety Reporting System. This system is also synergistic with ROSIS and SAFRON.Results:The ROIRLS facilitates the collection of data that help in tracking adverse events and near misses and develop new interventions to prevent such incidents. The ROIRLS electronic infrastructure is fully integrated with each registered facility profile data thus minimizing key strokes and multiple entries by the event reporters.Conclusions:OIRLS is expected to improve the quality and safety of a broad spectrum of radiation therapy patients treated in the VA and fulfills our goal of Effecting Quality While Treating Safely The Radiation Oncology Incident Reporting and Learning System software used for this program has been developed, conceptualized and maintained by TSG Innovations Inc. and is deployed on the VA intranet as a Website.The Radiation Oncology Incident Reporting and Learning System software used for this program has been developed, conceptualized and maintained by TSG Innovations Inc. and is deployed on the VA intranet as a Website.