bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐580: On the Significance of Model Based Dosimetry for Breast and Head and Neck 192Ir HDR Brachytherapy
Authors: Peppa V , Pappas E , Pantelis E , Major T , Polgar C , Papagiannis P 
Published: June 2015

Purpose:To assess the dosimetric and radiobiological differences between TG43‐based and model‐based dosimetry in the treatment planning of 192Ir HDR brachytherapy for breast and head and neck cancer.Methods:Two cohorts of 57 Accelerated Partial Breast Irradiation (APBI) and 22 head and neck (H&N) patients with oral cavity carcinoma were studied. Dosimetry for the treatment plans was performed using the TG43 algorithm of the Oncentra Brachy v4.4 treatment planning system (TPS). Corresponding Monte Carlo (MC) simulations were performed using MCNP6 with input files automatically prepared by the BrachyGuide software tool from DICOM RT plan data. TG43 and MC data were compared in terms of % dose differences, Dose Volume Histograms (DVHs) and related indices of clinical interest for the Planning Target Volume (PTV) and the Organs‐At‐Risk (OARs). A radiobiological analysis was also performed using the Equivalent Uniform Dose (EUD), mean survival fraction (S) and Tumor Control Probability (TCP) for the PTV, and the Normal Tissue Control Probability (N TCP) and the generalized EUD (gEUD) for the OARs. Significance testing of the observed differences performed using the Wilcoxon paired sample test.Results:Differences between TG43 and MC DVH indices, associated with the increased corresponding local % dose differences observed, were statistically significant. This is mainly attributed to their consistency however, since TG43 agrees closely with MC for the majority of DVH and radiobiological parameters in both patient cohorts. Differences varied considerably among patients only for the ipsilateral lung and ribs in the APBI cohort, with a strong correlation to target location.Conclusion:While the consistency and magnitude of differences in the majority of clinically relevant DVH indices imply that no change is needed in the treatment planning practice, individualized dosimetry improves accuracy and addresses instances of inter‐patient variability observed.Research co‐financed by the ESF and Greek funds through the Operational Program Education and Lifelong Learning Investing in Knowledge Society of the NSRF. Research Funding Program Aristeia. Nucletron, an Elekta company (Veenendaal, The Netherlands) is gratefully acknowledged for providing Oncentra Brachy v4.4 for research purposes.
SU‐E‐T‐582: On‐Line Dosimetric Verification of Respiratory Gated Volumetric Modulated Arc Therapy Using the Electronic Portal Imaging Device
Authors: Schaly B , Xhaferllari I , Gaede S 
Published: June 2015

Purpose:To investigate the clinical utility of on‐line verification of respiratory gated VMAT dosimetry during treatment.Methods:Portal dose images were acquired during treatment in integrated mode on a Varian TrueBeam (v. 1.6) linear accelerator for gated lung and liver patients that used flattening filtered beams. The source to imager distance (SID) was set to 160 cm to ensure imager clearance in case the isocenter was off midline. Note that acquisition of integrated images resulted in no extra dose to the patient. Fraction 1 was taken as baseline and all portal dose images were compared to that of the baseline, where the gamma comparison and dose difference were used to measure day‐to‐day exit dose variation. All images were analyzed in the Portal Dosimetry module of Aria (v. 10). The portal imager on the TrueBeam was calibrated by following the instructions for dosimetry calibration in service mode, where we define 1 calibrated unit (CU) equal to 1 Gy for 10×10 cm field size at 100 cm SID. This reference condition was measured frequently to verify imager calibration.Results:The gamma value (3%, 3 mm, 5% threshold) ranged between 92% and 100% for the lung and liver cases studied. The exit dose can vary by as much as 10% of the maximum dose for an individual fraction. The integrated images combined with the information given by the corresponding on‐line soft tissue matched cone‐beam computed tomography (CBCT) images were useful in explaining dose variation. For gated lung treatment, dose variation was mainly due to the diaphragm position. For gated liver treatment, the dose variation was due to both diaphragm position and weight loss.Conclusion:Integrated images can be useful in verifying dose delivery consistency during respiratory gated VMAT, although the CBCT information is needed to explain dose differences due to anatomical changes.
SU‐E‐T‐585: Optically‐Stimulated Luminescent Dosimeters for Monitoring Pacemaker Dose in Radiation Therapy
Authors: Apicello L , Riegel A , Jamshidi A 
Published: June 2015

Purpose:A sufficient amount of ionizing radiation can cause failure to components of pacemakers. Studies have shown that permanent damage can occur after a dose of 10 Gy and minor damage to functionality occurs at doses as low as 2 Gy. Optically stimulated thermoluminescent dosimeters (OSLDs) can be used as in vivo dosimeters to predict dose to be deposited throughout the treatment. The purpose of this work is to determine the effectiveness of using OSLDs for in vivo dosimetry of pacemaker dose.Methods:As part of a clinical in vivo dosimetry experience, OSLDs were placed at the site of the pacemaker by the therapist for one fraction of the radiation treatment. OSLD measurements were extrapolated to the total dose to be received by the pacemaker during treatment. A total of 79 measurements were collected from November 2011 to December 2013 on six linacs. Sixty‐six (66) patients treated in various anatomical sites had the dose of their pacemakers monitored.Results:Of the 79 measurements recorded, 76 measurements (96 %) were below 2 Gy. The mean and standard deviation were 50.12 ± 76.41 cGy. Of the 3 measurements that exceeded 2 Gy, 2 measurements matched the dose predicted in the treatment plan and 1 was repeated after an unexpectedly high Result. The repeated measurement yielded a total dose less than 2 Gy.Conclusion:This analysis suggests OSLDs may be used for in vivo monitoring of pacemaker dose. Further research should be performed to assess the effect of increased backscatter from the pacemaker device.
SU‐E‐T‐586: Optimal Determination of Tolerance Level for Radiation Dose Delivery Verification in An in Vivo Dosimetry System
Authors: Chen Y , Souri S , Gill G , Rea A , Kuruvilla A , Riegel A , Cao Y , Jamshidi A 
Published: June 2015

Purpose:To statistically determine the optimal tolerance level in the verification of delivery dose compared to the planned dose in an in vivo dosimetry system in radiotherapy.Methods:The LANDAUER MicroSTARii dosimetry system with screened nanoDots (optically stimulated luminescence dosimeters) was used for in vivo dose measurements. Ideally, the measured dose should match with the planned dose and falls within a normal distribution. Any deviation from the normal distribution may be redeemed as a mismatch, therefore a potential sign of the dose misadministration. Randomly mis‐positioned nanoDots can yield a continuum background distribution. A percentage difference of the measured dose to its corresponding planned dose (ΔD) can be used to analyze combined data sets for different patients. A model of a Gaussian plus a flat function was used to fit the ΔD distribution.Results:Total 434 nanoDot measurements for breast cancer patients were collected across a period of three months. The fit yields a Gaussian mean of 2.9% and a standard deviation (SD) of 5.3%. The observed shift of the mean from zero is attributed to the machine output bias and calibration of the dosimetry system. A pass interval of −2SD to +2SD was applied and a mismatch background was estimated to be 4.8%. With such a tolerance level, one can expect that 99.99% of patients should pass the verification and at most 0.011% might have a potential dose misadministration that may not be detected after 3 times of repeated measurements. After implementation, a number of new start breast cancer patients were monitored and the measured pass rate is consistent with the model prediction.Conclusion:It is feasible to implement an optimal tolerance level in order to maintain a low limit of potential dose misadministration while still to keep a relatively high pass rate in radiotherapy delivery verification.
SU‐E‐T‐588: Optimization of Imaging Following 223Ra Administration in Targeted Alpha‐Emitting Radionuclide Therapy of Bone Metastases
Authors: Benabdallah N , Bernardini M , Desbree A , de Labriolle‐Vaylet C , Franck D 
Published: June 2015

Purpose:With a growing demand of alpha‐emitting radiopharmaceuticals, especially Xofigo (223RaCl2) which is used in the treatment of metastatic bone disease, the optimization of dosimetry becomes necessary. Indeed, in Europe, as stated on the council directive 2013/59/euratom, exposures of target volumes for radiotherapeutic purposes shall be individually planned taking into account that doses to non‐target volumes and tissues shall be as low as reasonably achievable. To that aim, the possibility of imaging 223Ra was first investigated.Methods:The experiments were conducted at the Hopital Europeen Georges Pompidou with an Infinia Hawkeye 4 gamma camera, equipped with a medium‐energy collimator. Imaging parameters, such as sensibility, spatial resolution and energy spectrum, were determined using several physical phantoms with a source of 6 MBq of 223Ra. Bone metastases were modeled with a NEMA Body Phantom to investigate image degradation based on the concentration of 223Ra.Results:The acquired energy spectrum allowed to visualize several photon peaks: at 85, 154 and 270 keV. Camera sensitivity measured from the phantom study was 102.3 cps/MBq for the 85 keV ± 20 %, 89.9 cps/MBq for the 154 ± 20 % window and 65.4 cps/MBq for the 270 ± 10 % window. The spatial resolution (full‐width at half‐maximum) was respectively 1.7, 1.9 and 1.8 cm for the three energy windows. SPECT/CT images of NEMA Body Phantom without and with attenuation have permitted to determine the best reconstruction parameters.Conclusion:This study has demonstrated that it is possible to obtain clinically relevant information from images of 223Ra. All these results will be valuable to analyze biodistribution imaging of the radiopharmaceutical in the patient body and go further in the reconstruction of patient images in order to personalize the dosimetry.
SU‐E‐T‐590: Optimizing Magnetic Field Strengths with Matlab for An Ion‐Optic System in Particle Therapy Consisting of Two Quadrupole Magnets for Subsequent Simulations with the Monte‐Carlo Code FLUKA
Authors: Baumann K , Weber U , Simeonov Y , Zink K 
Published: June 2015

Purpose:Aim of this study was to optimize the magnetic field strengths of two quadrupole magnets in a particle therapy facility in order to obtain a beam quality suitable for spot beam scanning.Methods:The particle transport through an ion‐optic system of a particle therapy facility consisting of the beam tube, two quadrupole magnets and a beam monitor system was calculated with the help of Matlab by using matrices that solve the equation of motion of a charged particle in a magnetic field and field‐free region, respectively. The magnetic field strengths were optimized in order to obtain a circular and thin beam spot at the iso‐center of the therapy facility. These optimized field strengths were subsequently transferred to the Monte‐Carlo code FLUKA and the transport of 80 MeV/u C12‐ions through this ion‐optic system was calculated by using a user‐routine to implement magnetic fields. The fluence along the beam‐axis and at the iso‐center was evaluated.Results:The magnetic field strengths could be optimized by using Matlab and transferred to the Monte‐Carlo code FLUKA. The implementation via a user‐routine was successful. Analyzing the fluence‐pattern along the beam‐axis the characteristic focusing and de‐focusing effects of the quadrupole magnets could be reproduced. Furthermore the beam spot at the iso‐center was circular and significantly thinner compared to an unfocused beam.Conclusion:In this study a Matlab tool was developed to optimize magnetic field strengths for an ion‐optic system consisting of two quadrupole magnets as part of a particle therapy facility. These magnetic field strengths could subsequently be transferred to and implemented in the Monte‐Carlo code FLUKA to simulate the particle transport through this optimized ion‐optic system.
SU‐E‐T‐592: OSL Response of Al2O3:C Detectors Exposed to Therapeutic Proton Beams
Authors: Granville DA , Flint DB , Sawakuchi GO 
Published: June 2015

Purpose:To characterize the response of Al2O3:C optically stimulated luminescence (OSL) detectors (OSLDs) exposed to therapeutic proton beams of differing beam quality.Methods:We prepared Al2O3:C OSLDs from the same material as commercially available nanoDot dosimeters (Landauer, Inc). We irradiated the OSLDs in modulated proton beams of varying quality, as defined by the residual range. An absorbed dose to water of 0.2 Gy was delivered to all OSLDs with the residual range values varying from 0.5 to 23.5 cm (average LET in water from ∼0.5 to 2.5 keV/µm). To investigate the beam quality dependence of different emission bands within the OSL spectrum, we performed OSLD readouts using both continuous‐wave stimulation (CW‐OSL) and pulsed stimulation (P‐OSL) with two sets of optical filters (Hoya U‐340 and Kopp 5113). For all readout modes, the relative absorbed dose sensitivity (<i>Srel</i>) for each beam quality was calculated using OSLDs irradiated in a 6 MV photon beam as a reference.Results:We found that the relative absorbed dose sensitivity was highly dependent on both readout mode and integration time of the OSL signal. For CW‐OSL signals containing only the blue emission band, <i>Srel</i> was between 0.85 and 0.94 for 1 s readouts and between 0.82 and 0.93 for 10 s readouts. Similarly, for P‐OSL readouts containing only the blue emission band <i>Srel</i> ranged from 0.86 to 0.91, and 0.82 to 0.93 for 1 s and 10 s readouts, respectively. For OSLD signals containing only the UV emission band, <i>Srel</i> ranged from 1.00 to 1.46, and 0.97 to 1.30 for P‐OSL readouts of 1 s and 10 s, respectively.Conclusion:For measurements of absorbed dose using Al2O3:C OSLDs in therapeutic proton beams, dependence on beam quality was smallest for readout protocols that selected the blue emission band with small integration times.DA Granville received financial support from the Natural Sciences and Engineering Research Council of Canada
SU‐E‐T‐597: Parameterization of the Photon Beam Dosimetry for a Commercial Linear Accelerator
Authors: Lebron S , Lu B , Yan G , Kahler D , Li J , Barraclough B , Liu C 
Published: June 2015

Purpose:In radiation therapy, accurate data acquisition of photon beam dosimetric quantities is important for (1) beam modeling data input into a treatment planning system (TPS), (2) comparing measured and TPS modelled data, (3) a linear accelerator's (linac) beam characteristics quality assurance process, and (4) establishing a standard data set for data comparison, etcetera. Parameterization of the photon beam dosimetry creates a portable data set that is easy to implement for different applications such as those previously mentioned. The aim of this study is to develop methods to parameterize photon percentage depth doses(PDD), profiles, and total scatter output factors(Scp).Methods:Scp, PDDs and profiles for different field sizes (from 2×2 to 40×40cm2), depths and energies were measured in a linac using a three‐dimensional water tank. All data were smoothed and profile data were also centered, symmetrized and geometrically scaled. The Scp and PDD data were analyzed using exponential functions. For modelling of open and wedge field profiles, each side was divided into three regions described by exponential, sigmoid and Gaussian equations. The model's equations were chosen based on the physical principles described by these dosimetric quantities. The equations’ parameters were determined using a least square optimization method with the minimal amount of measured data necessary. The model's accuracy was then evaluated via the calculation of absolute differences and distance–to–agreement analysis in low gradient and high gradient regions, respectively.Results:All differences in the PDDs’ buildup and the profiles’ penumbra regions were less than 2 mm and 0.5 mm, respectively. Differences in the low gradient regions were 0.20 ± 0.20% and 0.50 ± 0.35% for PDDs and profiles, respectively. For Scp data, all differences were less than 0.5%.Conclusion:This novel analytical model with minimum measurement requirements proved to accurately calculate PDDs, profiles, and Scp for different field sizes, depths and energies.
SU‐E‐T‐601: Patient Specific QA Check for Radiotherapy with Carbon Beam at SAGA HIMAT
Authors: Himukai T , Tsunashima Y , Kanazawa M , Mizota M , Shioyama Y , Endo M 
Published: June 2015

Purpose:To verify a patient specific QA for a prescribed dose per monitor unit (MU) and range check of carbon ion radiotherapy with a beam wobbling method at SAGA HIMAT.Methods:The dose distribution in a water phantom was recalculated with a treatment plan made by XiO‐N (Mitsubishi Electric Corporation, Tokyo). The depth dose distributions at central axis were compared with measurements using pinpoint ionization chamber (PTW31014). Measured data were analyzed for dose and distance difference with criteria of 3% and 2mm. To check for the MU and range, analysis data were used at center and distal end of a spread out bragg peak (SOBP) depth, respectively.Results:Treatment plan of 1400 beams in 500 patients were used for analysis. The pass rate of the MU and range was about 98% and 74%, respectively. The rate of both was 73%. The plan data passed only the MU check were verified depth dose profile. The data passed only the range and failed of both were compared depth dose distributions at off axis. If it was failed, we discussed with physicians.Conclusion:Most of patient specific QA check for a prescribed MU and range check at SAGA HIMAT were passed.
SU‐E‐T‐604: Penumbra Characteristics of a New InCiseâ„¢ Multileaf Collimator of CyberKnife M6â„¢ System
Authors: Hwang M , Jang S , Ozhasoglu C , Lalonde R , Heron D , Huq M 
Published: June 2015

Purpose:The InCise™ Multileaf Collimator (MLC) of CyberKnife M6™ System has been released recently. The purpose of this study was to explore the dosimetric characteristics of the new MLC. In particular, the penumbra characteristics of MLC fields at varying locations are evaluated.Methods:EBT3‐based film measurements were performed with varying MLC fields ranging from 7.5 mm to 27.5 mm. Seventeen regions of interests (ROIs) were identified for irradiation. These are regions located at the central area (denoted as reference field), at the left/right edge areas of reference open field, at an intermediate location between central and edge area. Single beam treatment plans were designed by using the MultiPlan and was delivered using the Blue Phantom. Gafchromic films were irradiated at 1.5 cm depth in the Blue Phantom and analyzed using the Film Pro software. Variation of maximum dose, penumbra of MLC‐defined fields, and symmetry/flatness were calculated as a function of locations of MLC fields.Results:The InCise™ MLC System showed relatively consistent dose distribution and penumbra size with varying locations of MLC fields. The measured maximum dose varied within 5 % at different locations compared to that at the central location and agreed with the calculated data well within 2%. The measured penumbrae were in the range of 2.9 mm and 3.7 mm and were relatively consistent regardless of locations. However, dose profiles in the out‐of‐field and in‐field regions varied with locations and field sizes. Strong variation was seen for all fields located at 55 mm away from the central field. The MLC leakage map showed that the leakage is dependent on position.Conclusion:The size of penumbra and normalized maximum dose for MLC‐defined fields were consistent in different regions of MLC. However, dose profiles in the out‐field region varied with locations and field sizes.
SU‐E‐T‐615: Plan Comparison Between Photon IMRT and Proton Plans Incorporating Uncertainty Analysis
Authors: Cheng C , Wessels B , Jesseph F , Mattson D , Mansur D 
Published: June 2015

Purpose:In this study, we investigate the effect of setup uncertainty on DVH calculations which may impact plan comparison.Methods:Treatment plans (6 MV VMAT calculated on Pinnacle TPS) were chosen for different disease sites: brain, prostate, H&N and spine in this retrospective study. A proton plan (PP) using double scattering beams was generated for each selected VMAT plan subject to the same set of dose‐volume constraints as in VMAT. An uncertainty analysis was incorporated on the DVH calculations in which isocenter shifts from 1 to 5 mm in each of the ±x, ±y and ±z directions were used to simulate the setup uncertainty and residual positioning errors. A total of 40 different combinations of isocenter shifts were used in the re‐calculation of DVH of the PTV and the various OARs for both the VMAT and the corresponding PT.Results:For the brain case, both VMAT and PP are comparable in PTV coverage and OAR sparing, and VMAT is a clear choice for treatment due to its ease of delivery. However, when incorporating isoshifts in DVH calculations, a significant change in dose‐volume relationship emerges. For example, both VMAT and PT provide adequate coverage, even with ±3mm isoshift. However, +3mm isoshift results in increase of V40(Lcochlea, VMAT) from 7.2% in the original plan to 45% and V40(R cochlea, VMAT) from 75% to 92%. For protons, V40(Lcochlea, PT) increases from 62% in the initial plan to 75%, while V40(Rcochea, PT) increases from 7% to 26%.Conclusion:DVH alone may not be sufficient to allow an unequivocal decision in plan comparison, especially when two rival plans are very similar in both PTV coverage and OAR sparing. It is a good practice to incorporate uncertainty analysis on photon and proton plan comparison studies to test the plan robustness in plan evaluation.