bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐461: Validation of Planning Algorithms in Dynamic Conformal Arc in IPlan Using ArcCHECK and 3DVH
Authors: Lei Y , Zhang Q , Li S , Morgan B , Driewer J , Zhou S 
Published: July 2014

Purpose:To study the effect of limited angular resolution of pencil beam calculation (PBC) on dynamic conformal arc plan (DCAP) in iPlan (BrainLab) using the ArcCHECK sytem and 3DVH software (Sun Nuclear Corporation).Methods:Four DCAPs were generated in iPlan RT Dose 4.5 treatment planning system on the ArcCHECK cylindrical phantom with central planning target volume (PTV). A cylindrical shell structure (SHELL) 2.85cm from phantom surface and 1.5 mm thickness was created to simulate the ArcCHECK diode array. Planned doses were calculated using both Monte Carlo calculation (MCC) and PBC algorithms, and exported to 3DVH software for global and target based comparisons using the 3Dgamma index. Four additional DCAPs were created and calculated on patient CT images and mapped onto the ArcCHECK phantom for measurement using a Varian TrueBeam STx. The measurements were compared against both MC and PB calculation using gamma index analysis.Results:For the ArcCHECK phantom, the dose distribution agreement quantified with 3D‐gamma index is better (average‐gamma (<γ>)=99.9%vs.79.1% and 96.8%vs45.7%, p=0.0294, 0.0286 for gamma (2mm,2%) and (1mm,1%) criteria respectively using Mann‐Whitney U test) in the PTV than in the SHELL. The measurements show better agreement with MCC than the PB (<γ>=100%vs.86.7%, 99.6%vs.72.3%, 85.5%vs.50.8%, p=0.021, 0.026, 0.029 for gamma (3mm,3%), (2mm,2%) and (1mm,1%) criteria using Mann‐Whitney U test respectively). The effect due to limited (10 degree) angular resolution of the PBC was observed, and it can be one of the possible reasons for poor agreement between measurement and PB calculation.Conclusion:The PBC of iPlan shows poor peripheral dose calculation accuracy for dynamic conformal arc plans due to limited angular resolution, but it performs well in the area close to target volume without considering heterogeneity. Since the user cannot change the 10 degree angular resolution of PBC, MCC is more appropriate for dynamic conformal arc plans.
SU‐E‐T‐462: Fixed‐Jaw Optimization for Critical Structure Sparing in IMRT Treatment Planning: Beam Modeling Cautions for Non‐Routine Use
Authors: Price R , Veltchev I , Cherian G , Ma C 
Published: July 2014

Purpose:Multiple publications exist concerning fixed‐jaw utilization to avoid linac carriage shifts and reduce intensity modulated radiotherapy (IMRT) treatment times. The purpose of this work is to demonstrate delivery QA discrepancies and illustrate the need for improved treatment planning system (TPS) commissioning for non‐routine use.Methods:A 6cm diameter spherical target was delineated on a virtual phantom containing the Iba Matrixx linear array within the Varian Eclipse TPS. Optimization was performed for target coverage for the following 3 scenarios: a single open, zero degree field where the X and Y jaws completely cover the target; the same field using an asymmetric, fixed‐jaw technique where the upper Y jaw does not cover the superior 2cm of the target; and both of the aforementioned directed at the target at 315 and 45 degree gantry angles, respectively. This final orientation was also irradiated on a linac for delivery analysis. A sarcoma patient case was also analyzed where the fixed jaw technique was utilized for kidney sparing.Results:The open beam results were as predicted but the fixed‐jaw results demonstrate a pronounced fluence increase along the asymmetric, upper jaw. Analysis of the delivery of the combined beam plan Resultin 83% of pixels evaluated passing gamma criteria of 3%, 3mm DTA. Analysis for the sarcoma patient, in the plane of the shielded kidney, indicated 93% passing although the maximum dose discrepancies in this region were approximately 23%.Conclusion:Optimization within the target is routinely performed using MLC leaf‐end characteristics. The fixed‐jaw technique forces optimization of target coverage to utilize the penumbra profiles of the associated beamdefining jaw. If the profiles were collected using a common 0.125cc ionization chamber, the resolution may be insufficient resulting in a planvs.‐delivery mismatch. It is recommended that high‐resolution beam characteristics be considered when non‐routine planning methods are utilized.
SU‐E‐T‐463: Quantification of Rotational Variation in Mouse Setup for IGRT
Authors: McCarroll R , Rubinstein A , Kingsley C , Yang J , Yang P , Court L 
Published: July 2014

Purpose:New small‐animal irradiators include extremely precise IGRT capabilities. However, mouse immobilization and localization remains a challenge. In particular, unlike week‐to‐week translational displacements, rotational changes in positioning are not easily corrected for in subject setup. Using two methods of setup, we aim to quantify week‐to‐week rotational variation in mice for the purpose of IGRT planning in small animal studies.Methods:Ten mice were imaged weekly using breath‐hold CBCT (X‐RAD 225 Cx), with the mouse positioned in a half‐pipe support, providing 40 scans. A second group of two mice were positioned in a 3D printed immobilization device, which was created using a CT from a similarly shaped mouse, providing 10 scans. For each mouse, the first image was taken to be the reference image. Subsequent CT images were then rigidly registered, based on bony anatomy. Rotations in the axial (roll), sagittal (pitch), and coronal (yaw) planes were recorded and used to quantify variation in angular setup.Results:For the mice imaged in the half pipe, average magnitude of roll was found to be 5.4±4.6° (range: −12.9:18.86°), of pitch 1.6±1.3° (range: −1.4:4.7°), and of yaw 1.9±1.5° (range −5.4:1.1°). For the mice imaged in the printed setup; average magnitude of roll was found to be 0.64±0.6° (range: −2.1:1.0°), of pitch 0.6±0.4° (range: 0.0:1.3°), and of yaw 0.2±0.1° (range: 0.0:0.4°). The printed setup provided reduction in roll, pitch, and yaw by 88, 62, and 90 percent, respectively.Conclusion:For the typical setup routine, roll in mouse position is the dominant source of rotational variation. However, when a printed device was used, drastic improvements in mouse immobilization were seen. This work provides a promising foundation for mouse immobilization, required for full scale small animal IGRT. Currently, we are making improvements to allo±w the use of a similar system for MR, PET, and bioluminescence.
SU‐E‐T‐464: On the Equivalence of the Quality Correction Factor for Pencil Beam Scanning Proton Therapy
Authors: Sorriaux J , Paganetti H , Testa M , Giantsoudi D , Schuemann J , Bertrand D , Orban de Xivry J. , Lee J , Palmans H , Vynckier S , Sterpin E 
Published: July 2014

Purpose:In current practice, most proton therapy centers apply IAEA TRS‐398 reference dosimetry protocol. Quality correction factors (kQ) take into account in the dose determination process the differences in beam qualities used for calibration unit and for treatment unit. These quality correction factors are valid for specific reference conditions. TRS‐398 reference conditions should be achievable in both scattered proton beams (i.e. DS) and scanned proton beams (i.e. PBS). However, it is not a priori clear if TRS‐398 kQ data, which are based on Monte Carlo (MC) calculations in scattered beams, can be used for scanned beams. Using TOPAS‐Geant4 MC simulations, the study aims to determine whether broad beam quality correction factors calculated in TRS‐398 can be directly applied to PBS delivery modality.Methods:As reference conditions, we consider a 10×10×10 cm3 homogeneous dose distribution delivered by PBS system in a water phantom (32/10 cm range/modulation) and an air cavity placed at the center of the spread‐out‐Bragg‐peak. In order to isolate beam differences, a hypothetical broad beam is simulated. This hypothetical beam reproduces exactly the same range modulation, and uses the same energy layers than the PBS field. Ion chamber responses are computed for the PBS and hypothetical beams and then compared.Results:For an air cavity of 2×2×0.2 cm3, the ratio of ion chamber responses for the PBS and hypothetical beam qualities is 0.9991 ± 0.0016.Conclusion:Quality correction factors are insensitive to the delivery pattern of the beam (broad beam or PBS), as long as similar dose distributions are achieved. This investigation, for an air cavity, suggests that broad beam quality correction factors published in TRS‐398 can be applied for scanned beams.J. Sorriaux is financially supported by a public‐private partnership involving the company Ion Beam Applications (IBA).
SU‐E‐T‐465: Dose Calculation Method for Dynamic Tumor Tracking Using a Gimbal‐Mounted Linac
Authors: Sugimoto S , Utsunomiya S , Ebe K , Inoue T , Kurokawa C , Usui K , Sasai K 
Published: July 2014

Purpose:Dynamic tumor tracking using the gimbal‐mounted linac (Vero4DRT, Mitsubishi Heavy Industries, Ltd., Japan) has been available when respiratory motion is significant. The irradiation accuracy of the dynamic tumor tracking has been reported to be excellent. In addition to the irradiation accuracy, a fast and accurate dose calculation algorithm is needed to validate the dose distribution in the presence of respiratory motion because the multiple phases of it have to be considered. A modification of dose calculation algorithm is necessary for the gimbal‐mounted linac due to the degrees of freedom of gimbal swing. The dose calculation algorithm for the gimbal motion was implemented using the linear transformation between coordinate systems.Methods:The linear transformation matrices between the coordinate systems with and without gimbal swings were constructed using the combination of translation and rotation matrices. The coordinate system where the radiation source is at the origin and the beam axis along the z axis was adopted. The transformation can be divided into the translation from the radiation source to the gimbal rotation center, the two rotations around the center relating to the gimbal swings, and the translation from the gimbal center to the radiation source. After operating the transformation matrix to the phantom or patient image, the dose calculation can be performed as the no gimbal swing. The algorithm was implemented in the treatment planning system, PlanUNC (University of North Carolina, NC). The convolution/superposition algorithm was used. The dose calculations with and without gimbal swings were performed for the 3 × 3 cm2 field with the grid size of 5 mm.Results:The calculation time was about 3 minutes per beam. No significant additional time due to the gimbal swing was observed.Conclusions:The dose calculation algorithm for the finite gimbal swing was implemented. The calculation time was moderate.
SU‐E‐T‐466: Dosimetric Assessment of the Salivary Glands in Head and Neck Tumour Patients Treated with Radiation Therapy
Authors: Peixoto Xavier C , Costa Ferreira B , Khouri L , Lopes M , Stathakis S , Papanikolaou N , Mavroidis P 
Published: July 2014

Purpose:To estimate the correlation between different dosimetric indices and the clinical outcome, which was recorded at different time points after the treatment, regarding the structure of salivary glands in head & neck cancer radiotherapy.Methods:218 salivary glands from patients with head and neck tumours treated at IPOCFG from 2007 to 2013 were included in this study. The follow up of those patients consisted on weekly medical visits during the treatment that take about seven weeks. After that the patients had consults every three months. Treatment complications were graded using the RTOG/EORTC guidelines. The response of the salivary glands (both parotids, oral cavity and both submandibular glands) was analyzed for six time periods: 7th week, 3rd, 7th, 12th, 18th and 24th months after the start of the radiotherapy. The total dose distributions, converted to a fractionation scheme of 2Gy fractional doses, were used to calculate the DVHs and dose‐response plots of salivary glands.Results:The small differences obtained between the mean DVHs showed that patients should be grouped into: with complications (G1+G2) and without complications (G0). The mean dose/2Gy was 22.2±13.2 Gy (G0) and 33.2±8.0 Gy (G1+G2) for the 7th week, 31.9±9.6 Gy (G0) and 34.6±6.8 Gy (G1+G2) for the 12th month and, 32.9±9.3 Gy (G0) and 37.2±8.5 Gy (G1+G2) for the 24th month. The dose‐response plots for the 7th week and 24th month were similar to the dose‐response curves published in the literature.Conclusion:In some cases, there were not major differences between the mean DVHs of the groups with and without complications in the salivary glands, when comparing them at different time periods. More radiobiological analysis should thus be made to estimate the clinical impact of those differences.
SU‐E‐T‐467: Definition of the Proper Tolerances for Beam‐Position Accuracy and Beam Width for Quality Assurance in Active Proton Pencil Beam Scanning
Authors: Safai S 
Published: July 2014

Purpose:To estimate the correlation between different dosimetric indices and the clinical outcome, which was recorded at different time points after the treatment, regarding the structure of salivary glands in head & neck cancer radiotherapy.Methods:218 salivary glands from patients with head and neck tumours treated at IPOCFG from 2007 to 2013 were included in this study. The follow up of those patients consisted on weekly medical visits during the treatment that take about seven weeks. After that the patients had consults every three months. Treatment complications were graded using the RTOG/EORTC guidelines. The response of the salivary glands (both parotids, oral cavity and both submandibular glands) was analyzed for six time periods: 7th week, 3rd, 7th, 12th, 18th and 24th months after the start of the radiotherapy. The total dose distributions, converted to a fractionation scheme of 2Gy fractional doses, were used to calculate the DVHs and dose‐response plots of salivary glands.Results:The small differences obtained between the mean DVHs showed that patients should be grouped into: with complications (G1+G2) and without complications (G0). The mean dose/2Gy was 22.2±13.2 Gy (G0) and 33.2±8.0 Gy (G1+G2) for the 7th week, 31.9±9.6 Gy (G0) and 34.6±6.8 Gy (G1+G2) for the 12th month and, 32.9±9.3 Gy (G0) and 37.2±8.5 Gy (G1+G2) for the 24th month. The dose‐response plots for the 7th week and 24th month were similar to the dose‐response curves published in the literature.Conclusion:In some cases, there were not major differences between the mean DVHs of the groups with and without complications in the salivary glands, when comparing them at different time periods. More radiobiological analysis should thus be made to estimate the clinical impact of those differences.
SU‐E‐T‐468: A New 3D Gamma Analysis Algorithm for Better VMAT/IMRT QA Results
Authors: Cao D , Ye J , Shepard D 
Published: July 2014

Purpose:The gamma dose distribution comparison method is used in VMAT QA to score the agreement between planned and measured dose distributions. Unfortunately, this dose comparison technique can Resultin compromised passing rates when the treatment plan includes a high dose gradient perpendicular to the measurement plane. To address this, we have developed and tested a 3D gamma analysis tool.Methods:An in‐house 3D‐gamma analysis algorithm was developed. Five VMAT patient specific QA plans were delivered and measured using a MatriXX 2D ion chamber array. A 3D dose volume was generated in the Pinnacle TPS, and exported to the analysis software. Both 2D and 3D gamma analysis were performed. The results determined using a 3%/3mm passing criteria were then evaluated and compared.Results:Cases that did not include a high dose gradient perpendicular and adjacent to the detector plane showed only minor differences between the 2D and 3D gamma analysis results. Cases including a high dose gradient (e.g. as a means to avoid an adjacent sensitive structure), the use of 3D gamma analysis resulted in improved passing rates with lower gamma values. For the five cases tested, the average gamma index value was reduced from 0.361 to 0.345 when 3D analysis was used. The average passing rate increased from 94.7% to 96%.Conclusion:A 3D gamma analysis tool has been developed and tested. For patient specific IMRT/VMAT QA performed using the composite dose measurement method, the use of 3D gamma analysis can effectively reduce the uncertainty in QA results due to factors such as setup errors. This technique can more effectively account for a high dose gradient perpendicular to the measurement plan. Consequently, improved and more meaningful QA results can be achieved using this technique.
SU‐E‐T‐469: A Practical Approach for the Determination of Small Field Output Factors Using Published Monte Carlo Derived Correction Factors
Authors: Calderon E , Siergiej D 
Published: July 2014

Purpose:Output factor determination for small fields (less than 20 mm) presents significant challenges due to ion chamber volume averaging and diode over‐response. Measured output factor values between detectors are known to have large deviations as field sizes are decreased. No set standard to resolve this difference in measurement exists. We observed differences between measured output factors of up to 14% using two different detectors. Published Monte Carlo derived correction factors were used to address this challenge and decrease the output factor deviation between detectors.Methods:Output factors for Elekta's linac‐based stereotactic cone system were measured using the EDGE detector (Sun Nuclear) and the A16 ion chamber (Standard Imaging). Measurements conditions were 100 cm SSD (source to surface distance) and 1.5 cm depth. Output factors were first normalized to a 10.4 cm × 10.4 cm field size using a daisy‐chaining technique to minimize the dependence of field size on detector response. An equation expressing the relation between published Monte Carlo correction factors as a function of field size for each detector was derived. The measured output factors were then multiplied by the calculated correction factors. EBT3 gafchromic film dosimetry was used to independently validate the corrected output factors.Results:Without correction, the deviation in output factors between the EDGE and A16 detectors ranged from 1.3 to 14.8%, depending on cone size. After applying the calculated correction factors, this deviation fell to 0 to 3.4%. Output factors determined with film agree within 3.5% of the corrected output factors.Conclusion:We present a practical approach to applying published Monte Carlo derived correction factors to measured small field output factors for the EDGE and A16 detectors. Using this method, we were able to decrease the percent deviation between both detectors from 14.8% to 3.4% agreement.
SU‐E‐T‐470: Beam Performance of the Radiance 330 Proton Therapy System
Authors: Nazaryan H , Nazaryan V , Flanz J , Alexandrov V , Wang F 
Published: July 2014

Purpose:The ProTom Radiance 330 proton radiotherapy system is a fully functional, compact proton radiotherapy system that provides advanced proton delivery capabilities. It supports three‐dimensional beam scanning with energy and intensity modulation. A series of measurements have been conducted to characterize the beam performance of the first installation of the system at the McLaren Proton Therapy Center in Flint, Michigan. These measurements were part of the technical commissioning of the system. Select measurements and results are presented.Methods:The Radiance 330 proton beam energy range is 70–250 MeV for treatment, and up to 330 MeV for proton tomography and radiography. Its 3‐D scanning capability, together with a small beam emittance and momentum spread, provides a highly efficient beam delivery. During the technical commissioning, treatment plans were created to deliver uniform maps at various energies to perform Gamma Index analysis. EBT3 Gafchromic films were irradiated using the Planned irradiation maps. Bragg Peak chamber was used to test the dynamic range during a scan in one layer for high (250 MeV) and Low (70 MeV) energies. The maximum and minimum range, range adjustment and modulation, distal dose falloff (80%–20%), pencil beam spot size, spot placement accuracy were also measured. The accuracy testing included acquiring images, image registration, receiving correction vectors and applying the corrections to the robotic patient positioner.Results:Gamma Index analysis of the Treatment Planning System (TPS) data vs. Measured data showed more than 90% of points within (3%, 3mm) for the maps created by the TPS. At Isocenter Beam Size (One sigma) < 3mm at highest energy (250 MeV) in air. Beam delivery was within 0.6 mm of the intended target at the entrance and the exit of the beam, through the phantom.Conclusion:The Radiance 330 Beam Performance Measurements have confirmed that the system operates as designed with excellent clinical performance specifications.Hovakim Nazaryan, Vahagn Nazaryan and Fuhua Wang are employees of ProTom International, Inc. who contributed to the development and completed the technical commissioning of the Radiance 330 proton therapy delivery system manufactured by ProTom International.
SU‐E‐T‐471: Small Field Jaw/MLC Reference Data
Authors: Kerns J , Alvarez P , Followill D , Lowenstein J , Molineu A , Summers P , Kry S 
Published: July 2014

Purpose:In recent years the need for small field data of MLCs has increased due to the use of intensity‐modulated radiation (IMRT), but moreover the use of stereotactic body radiation (SBRT) has increased, which uses not simply small field sizes, but small jaw and field sizes together. Having reference data for these small fields that is reliable would be invaluable to the physics community. Our study has gathered these values and the data distributions from the Radiological Physics Center's (RPC) site visits between 1990 and the present.Methods:For all measurements, the RPC used a 25 × 25 × 25cm water phantom placed at 100cm SSD. All measurements were made with an Exradin A16 cylindrical ion chamber at an effective depth of 10 cm. A total of 42 Varian machine measurements were used to compose the data for a 6 MV beam and 5 TrueBeam 6 MV flattening filter free (FFF) beams were used for FFF data.Results:Jaw/MLC fields were measured for both 6 MV and 6 MF FFF beams with the jaws and MLCs both at the following field sizes: 6×6, 4×4, 3×3, and 2×2cm. Measurements were normalized to the 10×10 field readings (defined by the jaws and MLC). Spread in the data was minimal and demonstrates a high level of accuracy of acquired data.Conclusion:Small field Jaw/MLC reference data for Varian 6MV and 6 MV FFF beams has been analyzed and presented here, composed of the aggregation of numerous RPC site visits. Obtaining reliable small field data remains difficult, however the RPC has collected high fidelity small field Jaw/MLC data. The data are presented as a reference along with their distributions, in such a way that the physicist can act based upon their own desired agreement with the reference data.