bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐378: Radiochromic Film Based Reference Dosimetry System for 192Ir Brachytherapy Sources
Authors: Aldelaijan S , Mohammed H , Tomic N , Liang L , Deblois F , Sarfehnia A , Abdel‐Rahman W , Seuntjens J , Devic S 
Published: November 2011

Purpose: Comparison between radiochromic film reference dosimetry system calibration curves established in water and Solid Water(TM) for high dose rate (HDR) 192‐Iridium brachytherapy source is described and assessed. Accordingly, a new reference dosimetry system protocol for HDR 192‐Iridium using the latest EBT‐2 model GAFCHROMIC(TM) film is suggested. Methods: Calibration curves were established in water and Solid Water(TM) using pieces of EBT‐2 GAFCHROMIC(TM) film irradiated with HDR 192‐Iridium brachytherapy source for a dose range from 0 to 50 Gy. A parallel‐opposed beam setup was specially designed to allow the positioning of the HDR source into two channels (catheters) with the film piece positioned mid‐way between them. This setup increases the dose homogeneity region over the film piece and reduces the positional uncertainty with respect to the radiation source. Responses of dosimetry systems were compared for irradiations in water and Solid Water(TM) by scaling the dose between media through Monte Carlo‐calculated conversion factor simulated for the two setups.Results: Monte Carlo calculated conversion factor, which converts dose delivered to the sensitive layer of the film in water to a dose delivered to the sensitive layer of the film in Solid Water(TM), was found to be 0.9941±0.0007. The EBT‐2 GAFCHROMIC(TM) film based reference dosimetry system described in this work can provide an overall one‐sigma uncertainty in measured dose of 2% for doses above 1 Gy Conclusions: Experimental confirmation of the Monte Carlo‐calculated factor that shows dose difference between measurements in water and Solid Water(TM) was provided. The remaining 0.6% difference between measurements in both media shows that Solid Water(TM) is a viable alternative to water as a reference medium in establishing the calibration curve at 192‐Iridium energy. Response curves utilizing green color channel only has shown superior precision if used alone in dosimetry for dose range that extends up to 50 Gy.This work was supported by the Natural Sciences and Engineering Research Council of Canada contract No. 386009. Saad Aldelaijan would like to acknowledge Saudi Food & Drug Authority for financial support during his graduate studies.
SU‐E‐T‐393: A Novel 4D Dosimetric Characterization of a Common 103‐Pd Brachytherapy Source with Mobile Internal Components
Authors: Baradaran‐Ghahfarokhi M , Mosleh‐Shirazi M , Faghihi R , Hadad K , Bagheri M , Naghshnezhad Z , Meigooni A 
Published: November 2011

Purpose: A new method, based on the Finite Element (FE) modeling, has been introduced for dosimetric assessment of the brachytherapy sources with mobile internal component. Methods: Dosimetric characteristic of a commercially available brachytherapy source, Best Double‐Wall Model 2335 103Pd seed, were calculated by Monte Carlo (MC) simulation using the MCNP4c2 and MCNP5 codes according to the updated AAPM Task Group 43 (TG43U1) protocol, following finite element (FE) modeling to predict displacements of the seedˈs internal radioactive components in different orientations of the seed encountered in clinical practice (4D dosimetry). The complete seed geometry and materials together with a published 103Pd spectrum were used to perform finite‐element modeling using ABAQUS v.6.8.1 software and dosimetric characterization of the source using MCNP4c2 and MCNP5 codes. Results: Using FE modeling, change of seed orientation resulted in displacements of the seedˈs internal components. For the case of the Model 2335 103Pd seed, this has a negligible effect on the dose rate constant and radial dose function (<1%) but the consequences on the 2D anisotropy function was greater (up to 16.2% at small angles). Conclusions: There are no clinically significant variations in the dose rate constant and radial dose function due to the uncertainty of the internal position of the structures for the Model 2335 103Pd seed. However, the uncertainty in the 2D anisotropy function at smaller angles is larger than what has been reported, due to the motion of the internal components. Using this 4D dosimetry method is suggested to determine the dosimetric characteristics of each new brachytherapy seed with mobile internal components.Keywords: Palladium‐103, Brachytherapy, Monte Carlo simulation, Finite Element modeling, TG43U1
SU‐E‐T‐415: Investigation of VMAT Patient Specific Quality Assurance Action Levels
Authors: Mancuso G , Fontenot J , Parker B , Neck D , González G , Gibbons J 
Published: November 2011

Purpose: To examine the appropriateness of patient specific IMRT quality assurance (QA) action levels for use in VMAT QA. Methods: QA measurements were evaluated for the test geometries provided in AAPM Task Group Report 119. The structure sets were copied onto a cylindrical water‐equivalent phantom. Using the Philips Pinnacle treatment planning system, IMRT and VMAT treatments were planned. The plans were delivered and the resulting dose distributions were measured (1) in 2 planes and at 3–4 points in the cylindrical phantom using radiochromic film and ion chamber, respectively, and (2) using a commercial 2D diode array. Ion chamber and diode array measurements were taken five times each, and film measurements were taken three times. Measured planar doses were analyzed using gamma analysis with criteria of 3%/3mm. Measured point doses were analyzed using percent difference. Differences between IMRT QA and VMAT QA results were tested for significance using a Studentˈs t‐test. Results: The radiochromic film results showed averages of 98.9%±1.0% and 99.1%±0.9% (p=0.47) of measured doses within 3%/3mm of calculated doses for IMRT and VMAT plans, respectively. Ion chamber results showed average differences between measured and calculated point doses of − 0.95%±1.5% and −1.8%±1.8% (p<0.01) for IMRT and VMAT plans, respectively. The diode array results showed averages of 98.7%±0.5% and 98.6%±0.7% (p=0.70) of measured doses within 3%/3mm of calculated doses for IMRT and VMAT plans, respectively. Conclusion: Differences between IMRT QA and VMAT QA results were not statistically significant for planar doses measured with radiochromic film and 2D diode array. The average difference between measured and calculated point doses was smaller in IMRT plans (p<0.01); however, the average point dose differences for both IMRT and VMAT were less than 2%. These results suggest that current action levels used in our clinic for evaluating IMRT QA may be applicable to VMAT QA.This work is supported in part by a sponsored research agreement with Elekta, Inc.
SU‐E‐T‐424: Clinical Validation of a GammaBeam Tomotherapy System Using the Octavius Pre‐Treatment QA Device
Authors: Adnani N , Rudraraju V , Xu L , Smith L P , Cernica G , Romesberg M 
Published: November 2011

Purpose: Verify and validate the clinical viability of a GammaBeam Tomotherapy system Methods: A full commissioning of the GammaBeam Tomotherapy unit is performed. This novel radiotherapy system integrates the Co‐60 Equinox machine (Best Theratronics, Canada), MIMiC MLC, AutoCrane and nomoSTATM software (Best Nomos, PA). PDDs, output factors and profiles was acquired and entered into the Corvus GammaBeam treatment planning system. Patient treatment plans for H&N, Pelvis, Brain and Brain SRS were generated. Corresponding pre‐treatment QA plans were calculated and delivered on the Octavius QA phantom (PTW, NY). As acceptance criteria, we applied a gamma analysis with a DTA ranging from 3 mm to 5 mm and a dose difference from 1% to 4% (of local dose). Plan quality is also analyzed in terms of target coverage, organ at risk sparing, skin dose, hot spots, etc., in comparison to serial tomotherapy plans generated on the same CT sets using linac based photon beams. Results: for the H&N plan, acceptance criteria were set to 4%, 5 mm DTA to meet the minimum requirement of more than 90% of points passing. For the Pelvis, 91.6% of points pass the 3%, 3 mm DTA. For Brain and Brain SRS, a gamma analysis based on 2%, 2 mm DTA resulted in 98% and 90.9% of points passing. In the most complex case of H&N, constraints were met with 10% hot spot (within the target) and a skin dose ∼50% of the prescribed dose. Conclusions: investigation has demonstrated that the GammaBeam Tomotherapy system is clinically viable. At maximum source activity (∼15000 Ci), a 2 Gy fraction of the H&N plan took 20 minutes to deliver. Although this time is expected to slowly increase, due to source decay, to reach ∼30 minutes three years later, it remains comparable to linac based tomotherapy treatment times.Financial support for this work was obtained from Best Medical International.
SU‐E‐T‐657: Quantitative Tumour Control Predictions for the Radiotherapy of Non‐Small‐Cell Lung Tumours
Authors: Nahum A , Uzan J , Jain P , Malik Z , Fenwick J , Baker C 
Published: November 2011

Purpose: Radiotherapy of non‐small‐cell lung tumours (NSCLC) is undergoing significant advances due to conformal planning, respiration‐ motion strategies, hypofractionation and isotoxic prescription‐dose individualisation (Fenwick et al 2009; Panettieri et al 2011). In order to maximise the efficacy of these various approaches a model for predicting local‐control probability as a function of the (absolute, total) dose distribution, number of fractions, tumour volume and overall treatment time is essential. Methods: We have taken three contrasting dose and fraction regimens (CHART; the Martel data; our own Clatterbridge clinical experience: 55 Gy in 20 fractions) together with the published (and our won unpublished) local control data and modelled all these data using the Marsden quasi‐mechanistic, LQ‐based, population TCP model (Nahum, Webb, Sanchez‐Nieto 1993, 2000). ‘Best‐fit’ model parameters were derived using a Matlab optimisation routine. Results: The fit is virtually “exact” as the figure demonstrates; the ‘best‐fit’ parameters are alpha = 0.307 per Gy, sigma_alpha = 0.037 Gy‐1, T_K = 20.9 days, Td = 3.7 days with alpha/beta&#61472;= 10 Gy and rho_clon =&#61488;10̂7 cm‐3 as the fixed parameters. Conclusions: The Marsden TCP model together with the above ‘best‐fit’ parameters is now ready to be used, togetrher with our in‐ house BioSuite software (Uzan et al 2011) to design radiobiologically optimised NSCLC protocols such as twice‐a‐day fractionation for larger, centrally located tumours and intermediate fraction number (8 to 15) schedules for tumours too large for the 3–5 fraction SBRT approach.This work was partially supported by Cancer Research UK
SU‐E‐T‐659: Maximizing the Therapeutic Effect of a Fractionated Treatment with Delivery of Inhomogeneous Daily Dose Distributions
Authors: Trofimov A , Niemierko A , Efstathiou JA 
Published: November 2011

Purpose: To evaluate potential gain in therapeutic effect from delivery of daily inhomogeneous fractional dose distributions in proton therapy, using pencil beam scanning. Methods: For a sample case of prostate cancer, we consider a standard course of 39 fractions of 2 Gy (78 Gy total), and a hypofractionated course of 20 fractions of 3 Gy (assuming alpha/beta=1.5, the equivalent dose in 2 Gy fractions (ED2Gy) is 77.1 Gy). Two sets of dose distributions were planned: (1) the standard approach, with a uniform dose (100% of prescription) delivered in every fraction to the entire target; (2) delivery of inhomogeneous fractional dose (IFD) distributions, which varied within the target volume between 65% and 135% of the nominal prescription. For IFD, the daily distributions were optimized in such a way that the two hemispheres of the prostate (split sagittally through the urethra) received, in alternating fractions, either 65% or 135% of the nominal fractional dose (e.g., 1.3 and 2.7 Gy), while the urethra received approximately 100% (e.g., 2 Gy) daily. The equivalent uniform dose (EUD), and ED2Gy were compared for different plans. Results: In the IFD course, the whole prostate received a nearly uniform dose over every 2 fractions, however ED2Gy was higher than with standard uniform dose: 81.9 Gy (5% increase) for the conventional, and 82.6 Gy (7% increase) for the hypofractionated course. Rectal and bladder EUD increased by <5%, while urethral EUD was unchanged. Conclusions: In treatment of prostate and other sites, improved therapeutic outcome can be expected with delivery of inhomogeneous daily dose distributions, while administering the prescribed uniform dose to target over the entire course of treatment. The extent of expected gain is dependent on model parameters (alpha/beta, EUD‐a, etc.), and dose distributions may potentially be designed to maximize the gain specifically for a certain assumed range of parameters.No disclosures or conflict of interest. Supported by the Federal Share of program income earned on C06‐CA059267, Proton Therapy Research and Treatment Center.
SU‐E‐T‐663: Extended TrueBeam Patient‐Independent Phase Space Library for the 6X, 6XFFF, 10X and 10XFFF Radiotherapy Beams
Authors: Constantin M , Sawkey D , Mansfield S , Salop A , LoSasso T , Svatos M 
Published: November 2011

Purpose: To develop a patient‐independent IAEA‐compliant phase space database using accurate geometry representation of the treatment head components imported from CAD (Computer‐Aided‐Design) drawings and a physics list exploration for the specific materials of the linac treatment head. Methods: Geant4.9.4 was employed to simulate the TrueBeam 6X, 6XFFF, 10X and 10XFFF photon beams. Electron beam transport in the linac was simulated with Parmela and used as input into dose calculations. Geometry components were tessellated solids, i.e. Generalized‐Dynamic‐Markup‐Language files, extracted from mechanical CAD drawings. A phase space scorer was implemented above the upper jaws on a cylindrical surface. The simulations were run on the Amazon Elastic Compute Cloud. Dose calculations in a water phantom (with 6×6×4 mm3 voxels) were performed using two physics lists, Standard Option‐0 and Low‐Energy Livermore/Penelope, with a 10um range‐cut. The Urban93 and Goudsmit‐Saunderson models were considered for electron multiple‐scattering, while Tsai and 2BN models for electron Bremsstrahlung angular generators. Results: The maximum dose difference between simulation and experiment was <1% for the percent depth dose curves and <3% for in‐field dose profiles. For large fields, the simulated dose profile horns were smaller by 2% for the 6X beam and larger by 3% for the 10X beam compared to the experiment. Simulations using the Goudsmit‐Saunderson model reproduced the experiment with higher accuracy than Urban93, causing a 3x CPU increase. No CPU penalty or accuracy differences were observed in simulations using the Tsai versus the 2BN angular generators. The Standard Option‐0 list has the advantage of providing 2x CPU speedup and can be used with a range cut of 0.1mm for medical physics applications above 1MeV, ensuring the same accuracy as the Low‐Energy Livermore/Penelope list. Conclusions: We developed an extended TrueBeam phase space database using high precision geometry implementation from CAD that can be used for future medical physics user applications.Work supported by Varian Medical Systems
SU‐E‐T‐665: Analytical Source Model for Modulated Electron Radiation Therapy
Authors: Papaconstadopoulos P , Alexander A , Connell T , Seuntjens J 
Published: November 2011

Purpose: To implement a dynamic, analytical source model for fast and accurate derivation of the beam characteristics on the exit plane of a linear accelerator for modulated electron radiation therapy using a Few Leaf Electron Collimator (FLEC). Methods: An analytical source model (SM) is derived for modulated electron radiation therapy (MERT) by the use of source fluence kernels directly on the linear acceleratorˈs exit plane. The BEAMnrc code was used to identify the most significant radiation sources in MERT. “Virtual” BEAM models were then created, where the different components of the sources were isolated to each other. Monte Carlo simulations of these models were performed to derive the fluence and energy electron distributions on the exit plane. The data were then stored as histograms on a 2D fluence grid (source kernels). Since the source kernels were derived by simulation of a precise accelerator model it is expected that the scattered particles would be accurately predicted. An arbitrary rectangular field can be recreated by superposition of the appropriate source kernels directly on the output plane. Results: Fluence and energy distributions were derived for three field sizes (8 × 8, 2 × 2 and 2 × 8 cm2) and 20 MeV electron beam energy with the SM and compared with the PH‐SP data. Scattered particles from the FLEC agreed well in all cases, while moderate discrepancies were encountered for the primary beam and scattered particles from the jaws. The total reconstructed beam deviation between PH‐SP and SM was less than 1.5% for all cases. Conclusions: The proposed method has shown to reproduce the fluence and energy distributions of small and/or arbitrary rectangular fields within acceptable tolerance. The model is expected to help significantly improve MERT optimization speed while maintaining accuracy in the dose calculations.Alexander S. Onassis Public Benefit Foundation
SU‐E‐T‐669: Clinical Implementation of a Commercial Monte Carlo Treatment Planning System for Electron Beams
Authors: Vandervoort E , Cygler J 
Published: November 2011

Purpose: Several Monte Carlo (MC) based treatment planning systems are commercially available for electron beams and more users are implementing them in the clinical setting. In the case of MC based treatment planning systems in addition to the dose calculation accuracy one also needs to define the additional calculation parameters, such as the calculation voxel size, the choice between the computation of dose‐to‐medium or dose‐to‐water, and the number of histories and/or acceptable level of statistical uncertainty for the voxelized dose distribution. Methods: We report on the influence of these parameters on both calculation time and on the accuracy of calculated dose distributions for the XiO electron Monte Carlo (XiO eMC) software, a new treatment planning system for electron beams developed and commercialized by CMS incorporated. A comparison of radiochromic film measurements with simulated data using different parameters was performed for a complex heterogeneous phantom. Results: Dose calculations in a heterogeneous phantom are in very good agreement with film measurements, provided that appropriate simulation parameters are used (1% average statistical uncertainty, voxel size=2×2×2 mm cubed and dose‐ to‐water is computed). The rapid three‐dimensional dose gradients exhibited for these data highlight the need for a fully 3D dose comparison tool (currently under development) for electron beams treating complex heterogeneous geometries. Using a clinical XiO Linux workstation (8 processors each 3 GHz, 8.29 GB RAM), high resolution (2.5×2.5×2.5 mm cubed) low noise (<1% MRSU) simulations can be obtained in less than 4 and 8 minutes respectively for 9 and 17 MeV beams with a 10×10 cm squared applicator. Conclusions: XiO eMC calculated dose distributions agree very well with the experimental ones in both water tank and heterogeneous phantoms. More investigation may be required, however, to determine the optimal trade off between dosimetric accuracy and clinically acceptable computation times.Financial support has been provided from Elekta CMS incorporated.
SU‐E‐T‐672: Macro Monte Carlo for Protons: Proof of Principle
Authors: Fix MK , Frei D , Volken W , Born EJ , Manser P 
Published: November 2011

Purpose: For electron beams the macro Monte Carlo (MC) technique is well‐established. This work describes the proof of principle of a new macro MC method for proton beams in order to gain computational efficiency. Methods: The proof of principle is performed for the transport of primary protons in water. Pre‐simulations of mono‐energetic proton pencil beams ranging from 10 to 250 MeV impinging perpendicularly on water slabs of different thicknesses (1–10 mm) have been carried out using Geant4. The lateral displacement, the energy‐loss and the direction of all exiting primary protons have been scored and converted into probability density functions (PDFs). The macro MC method consists of stepwise transporting protons by selecting appropriate slab thicknesses and by means of sampling from corresponding PDFs. The sampled energy‐loss is deposited along the path between the entrance and exit positions of the proton for the current step. For validation purposes, different mono‐energetic proton pencil beams impinging on a water phantom, the dose distributions for the primary protons have been calculated using the macro MC transport and Geant4. The resulting integral depth dose curves and dose profiles have been compared. Results: The calculated integral depth dose curves agree better than 1% or 1 mm for all pencil beams considered. The agreement between the dose profiles at several depths in water is within 1% or 1 mm for all energies and depths. The computational efficiency for the macro MC method is about 200 times higher than for Geant4. Conclusions: The results of the dose comparisons demonstrate the very accurate and efficient dose calculation of primary protons using the macro MC method. In future, the macro MC method will be extended to include patient materials and the secondary particle transport in order to allow patient dose calculations for proton beams.This work was supported by Varian Medical Systems.
SU‐E‐T‐673: Development of Monte Carlo Dose Calculation System for Tumor‐Tracking Irradiation with a Gimbaled X‐Ray Head
Authors: Ishihara Y , Sawada A , Nakamura M , Mukumoto N , Kaneko S , Takayama K , Mizowaki T , Kokubo M , Hiraoka M 
Published: November 2011

Purpose: To propose dose calculation model of tumor‐tracking irradiation by gimbals mechanism for MHI‐TM2000 (Vero). Methods: Our MC simulation for a 6 MV photon beam delivered by the MHI‐TM2000 system was performed using EGSnrc. First, the lateral doses (5 × 5 cm2 at 100 mm depth) with pan/tilt rotation were simulated under the SSD of 900 mm. Rotation angles along pan/tilt directions were set in the range of −2.5 to +2.5° at intervals of 0.5°. The corresponding measurements were performed using EDR2 films with water‐equivalent phantoms. Differences between simulated and measured doses were calculated. Furthermore, difference of output characteristic without setup error was estimated using the simulated lateral doses under the reference condition at the maximum and minimum rotation angles. Next, the moving phantom was driven at frequency of 0.25 Hz with amplitude of 10 mm along tilt direction. From the infrared marker positions, the corresponding pan/tilt angles were calculated. Time, phantom position by laser displacement gauge, current angle of pan/tilt, and MU were recorded in the log file. A phase space data at any angles was created from the log file and particle data under the MLC. Finally, both stationary X‐ray head and tumor‐tracking irradiation were simulated under the SSD of 950 mm (4 × 4 cm2 at 50 mm depth). Each of them was compared with the corresponding measurement using EDR2 film. Results: The lateral doses within flat region showed agreement of within 1.1% in any angles. The differences between doses at the minimum angle and at the maximum were within 0.5% and 4.5% in flat and penumbra region, respectively. The averaged differences between the simulated and the measured doses with stationary and tumor‐tracking irradiation were 1.9%. Conclusions: We have developed dose calculation model of tumor‐tracking irradiation for MHI‐TM2000. This study demonstrated our proposed model has acceptable accuracy.Research sponsored in part by Mitsubishi Heavy Industries, Ltd