bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐189: Commission Range Shifter On a Spot Scanning Proton System Using Raystation Treatment Planning System
Authors: Ding X , Rosen L , Wu H 
Published: June 2015

Purpose:To treat superficial target e.g. chest wall, head&neck or cranial cases, we commissioned two range shifter(RS) in Raystation4.0 with 7.37cm(RS1) and 4.1cm(RS2) Water Equivalent Thickness(WET) respectively. However, current beam model has limitations due to the secondary scattered proton. This study provides a detailed and critical commission data and provides suggestions for using RS in clinic.Methods:RS’ WET was verified by Multi‐Layer Ionization Chamber from 120MeV to 226.7MeV before TPS modeling. Spot characteristics were measured using 2D scintillate detector at ISO with different air gap. A 8×8×10cm3 cube is created in 8cm depth of water to verify the absolute dose accuracy. Plans were created with different air gap using both RS. Absolute dose verification was measured along the central axis from distal end to surface using PPC05. 10 clinical RS2 plans were measured using MatriXXPT in 3 planes (proximal, distal and midSOBP).Results:RS material's proton stopping power is energy dependent(from 70MeV to 226.7MeV) ranging from 7.42 to 7.31cm and from 4.10 to 4.03cm respectively. We chose 7.37cm (RS1) and 4.10cm (RS2) to favor the low and median proton energy. With different air gap(3cm to 32cm), spot size expands from 3.2mm to 5.5mm(RS1) and from 3.1mm to 4.1mm(RS2) respectively(226.7MeV in air, 1‐sigma). For the absolute dose verification, the larger air gap and shallower depth causes larger discrepancy between TPS and measurements. All 10 clinical plans with 5–10cm air gap passed gamma index 95% with 3%/3mm criteria and outputs differences were within 3%.Conclusion:We strongly recommend each institution to verify the WET independently and choose the value to fit the clinical needs. To minimize the output difference in Raystation4.0 while avoid potential collision to the patient, we recommend to use 5–10cm air gap to minimize the output difference within 2% and preferably use RS with smaller WET if possible.
SU‐E‐T‐191: Commissioning and Dosimetric Characteristics of Elekta Agility for Total Skin Electron Beam (TSEB) Therapy
Authors: Sayler E , Charpentier P , Micaily B , Miyamoto C , Li S 
Published: June 2015

PurposeThe purpose of this work is to publish beam data from Elekta Synergy(R) linear accelerators with Agility(TM) MLC for total skin electron beam (TSEB) therapy using the HDRE1 (High Dose Rate Electron 6MeV) energy.Method & MaterialsThe optimal gantry angles for TSEB were determined using ion chamber measurements along a vertical profile at 450cm SSD. After gantry angles were chosen, field uniformity was measured over the entire treatment area. Uniformity was measured with and without the patient support device, allowing the dosimetric effect of the support device to be determined. Beam output and PDD were measured at the calibration point (450cm SSD) for a dual beam using a parallel plate chamber in solid water. These measurements were repeated with the chamber and phantom rotated about the patient isocenter at various angles, in order to measure the contribution from oblique beams. This technique provides a precise measurement of the treatment skin dose (TSD). Lastly, ion chamber measurements were verified by film and diodes.ResultsThe optimal gantry angle for 450 cm SSD was determined to be 90±16°. This achieved uniformity better than 96% on the vertical axis, and 92% along the horizontal axis. HDRE1 was calibrated to deliver 10 cGy/MU at standard geometry (100 cm SSD, 1.2 cm depth). Thus at TSEB geometry (450 cm SSD, 0.1 cm depth) the output of the AP dual field was measured to be 0.35 cGy/MU. The TSD of a 20 cm radius cylinder for six (equally, 60° spaced) dual fields was measured to be 1.19 cGy/MU. Percent Depth Dose data for the AP dual field and TSD are shown in Figure 2.ConclusionThis paper provides a modern procedure for commissioning TSEB therapy on a linear accelerator, and clinical beam data for the Elekta Synergy(R) with Agility(TM) MLC.
SU‐E‐T‐197: Comparing Quality Assurance Strategies for Single Isocenter Treatments of Multiple Brain Metastases
Authors: Maurer J , Liu H , Wiant D , Koch K , Manning M , Sintay B 
Published: June 2015

Purpose:To demonstrate a new quality assurance (QA) technique for single isocenter volumetric modulated arc therapy (VMAT) plans for stereotactic radiosurgery of multiple brain metastases and to compare quantitative QA results using this method with results using a cylindrical diode array and full field coronal films.Methods:This study employs a phantom built of 28 thin slabs to accommodate radiochromic film insertions near all planning target volume (PTV) locations, providing target specific data for individual PTVs. Single isocenter VMAT plans were designed for two patients with 5 and 11 intra‐cranial metastases. Both plans were modified three times to create plans that overdosed a target by 10%, and underdosed a target by 10 % and 20%. Gamma analyses were performed for full field coronal films, the diode array measurements and for individual PTVs with the proposed film stack method using square ROIs centered on the PTVs, measuring twice the length of the PTV's equivalent sphere diameter. Passing gamma criteria was 95% of points passing at 5%/1mm and a threshold of 10% of the prescription dose.Results:Of the 6 introduced errors, 1 was detected by the diode array gamma test (93.1% pass rate). Pass rates for the other 5 ranged from 95.4–98.8%. None of the errors were detected using the full field film gamma test (pass rates: 98.7–99.9%). Using the proposed film stack method, 5 of 6 errors were detected by failed gamma tests (pass rates: 51, 53, 71, 87.3, 93.9 and 97.8%). The two high pass rates were due to attempts to underdose a PTV that measured too high in the original plan.Conclusion:The results suggest that current methods may be lacking quantitative value and rely heavily on challenging qualitative evaluation, while the proposed method offers a much needed practical method for meaningful quantitative results.
SU‐E‐T‐199: Comparison Between Acuros XB and AAA in Homogeneous Phantoms for Volumetric Modulated Arc Therapy Plans
Authors: Lu J‐Y , Huang B‐T , Zhang J‐Y 
Published: June 2015

Purpose:To investigate the differences among Acuros XB (AXB) with dose‐to‐water report mode (AXBw), AXB with dose‐to‐medium report mode (AXBm) and Anisotropic Analytical Algorithm (AAA), in homogeneous phantoms and for volumetric modulated arc therapy (VMAT) plans.Methods:Nineteen clinically applied VMAT plans were transplanted to a Delta4 phantom and an I'mRT phantom to generate phantom plans, respectively. Each plan was calculated using AXBw, AXBm and AAA, respectively, utilizing the distributed calculation framework (DCF), and the calculation times were recorded. Each plan was delivered by the TrueBeam linear accelerator and measured using the Delta4 phantom and ionization chamber, respectively. The 3D gamma pass rates and point dose deviations were compared among AXBw, AXBm and AAA.Results:In terms of the gamma pass rates with both the criteria of 3 mm/3% (3 mm distance‐to‐agreement, 3% dose difference) and 2 mm/2%, AXBm demonstrated the significantly worst results, and no significant difference was found between AXBw and AAA. In terms of the point dose, AXBw was slightly closer to the measured dose compared with AAA, and AXBm demonstrated the maximum dose deviation from the measured dose. Moreover, AXB calculation consumed comparable time when the DCF was not busy, and consumed significantly less time when the DCF was busy.Conclusion:In the homogeneous phantoms and for the VMAT plans, AXBw has the best dose accuracy, and AAA is comparable to or slightly worse than AXBw, wheras AXBm has the worst dose accuracy. Furthermore, AXB has higher calculation efficiency than AAA.
SU‐E‐T‐200: Comparison Between HybridARC and Sliding Windows IMRT for Spine SBRT Tumors
Authors: Venencia C , Vacca N , Garrigo E , Caussa L 
Published: June 2015

Purpose:Spine SBRT treatments require high dose to PTV, located close to OAR. Treatment time should be short due to patient condition. The objective of this work is to compare HybridARC (HA) with sliding windows IMRT treatment modalityMethods:A 6MV photon beam with 1000MU/min (SRS beam) produced by a NovalisTX (Varian/BrainLAB) equipped with HDMLC was used. The TPS was iPlan v4.5.3 (BrainLAB). Treatment plans comparison was done for 5 patients. Dose prescription was 27Gy in 3 fractions. HA used 1 arc plus 3 (HA), 5 (HA5) and 8 (HA8) IMRT fields. HA plans used OAR high. Between 60–40% of the prescribed dose was given by the arc. IMRT plans used 15 beams. Treatment times, MU, CI, V50% and V20% was used for plans comparisons.Results:Assuming IMRT plan as reference, the treatment time was reduced by −14.6% with HA8, −8.6% with HA5 and −23% with HA3. Increasing arc dose proportion in HA (arc MU > 2000) requires 2 or more arcs which increments treatment time. HA3 and HA5 exhibits beam hold off for fixed IMRT fields which in some cases need to be split in 2 segments. MU varied +4% with HA8, +3.7% with HA5 and −5% with HA3. CI increased +5% with HA8, +23% with HA5 and +37% with H3. V50% increased +5% with HA8, +43% with HA5 and +62% with HA3. V20% increased +13.2% with HA8, +7.6% with HA5 and +1% with HA3. OARs doses were keep within tolerances in all plans.Conclusion:HybridARC for spine SBRT with 8 fix IMRT gantry angle shows a treatment time reduction, comparable MU and similar dose conformation to dMLC IMRT. HybridARC with 5 or 3 fix IMRT fields produce undesirable beam hold off, worse dose conformation and increments the total volume with 50% of the prescribed dose.
SU‐E‐T‐202: Comparison of 4D‐Measurement‐Guided Dose Reconstructions (MGDR) with COMPASS and OCTAVIUS 4D System
Authors: Leung R , Wong M , Blanck O , Lee V , Law G , Lee K , Tung S , Chan M 
Published: June 2015

Purpose:To cross‐validate the MGDR of COMPASS (IBA dosimetry, GmbH, Germany) and OCTAVIUS 4D system (PTW, Freiburg, Germany).Methods:Volumetric‐modulated arc plans (5 head‐and‐neck and 3 prostate) collapsed to 40° gantry on the OCTAVIUS 4D phantom in QA mode on Monaco v5.0 (Elekta, CMS, Maryland Heights, MO) were delivered on a Elekta Agility linac. This study was divided into two parts: (1) error‐free measurements by gantry‐mounted EvolutionXX 2D array were reconstructed in COMPASS (IBA dosimetry, GmbH, Germany), and by OCTAVIUS 1500 array in Versoft v6.1 (PTW, Freiburg, Germany) to obtain the 3D doses (COM4D and OCTA4D). COM4D and OCTA4D were compared to the raw measurement (OCTA3D) at the same detector plane for which OCTAVIUS 1500 was perpendicular to 0° gantry axis while the plans were delivered at gantry 40°; (2) beam steering errors of energy (Hump=‐2%) and symmetry (2T=+2%) were introduced during the delivery of 5 plans to compare the MGDR doses COM4D_Hump (COM4D_2T), OCTA4D_Hump (OCTA4D_2T), with raw doses OCTA3D_Hump (OCTA3D_2T) and with OCTA3D to assess the error reconstruction and detection ability of MGDR tools. All comparisons used Υ‐criteria of 2%(local dose)/2mm and 3%/3mm.Results:Averaged Υ passing rates were 85% and 96% for COM4D,and 94% and 99% for OCTA4D at 2%/2mm and 3%/3mm criteria respectively. For error reconstruction, COM4D_Hump (COM4D_2T) showed 81% (93%) at 2%/2mm and 94% (98%) at 3%/3mm, while OCTA4D_Hump (OCTA4D_2T) showed 96% (96%) at 2%/2mm and 99% (99%) at 3%/3mm. For error detection, OCTA3D doses were compared to COM4D_Hump (COM4D_2T) showing Υ passing rates of 93% (93%) at 2%/2mm and 98% (98%), and to OCTA4D_Hump (OCTA4D _2T) showing 94% (99%) at 2%/2mm and 81% (96%) at 3%/3mm, respectively.Conclusion:OCTAVIUS MGDR showed better agreement to raw measurements in both error‐ and error‐free comparisons. COMPASS MGDR deviated from the raw measurements possibly owing to beam modeling uncertainty.
SU‐E‐T‐206: Comparison of EBT and EBT3 RadioChromic Films in Radiation Field of Parotid Cancer Radiotherapy
Authors: Toosi T Bahreyni , Mianaei F Khorshidi , Ghorbani M , Khabbaz Kazemi N Mohammadian , Mohammadi M , Meigooni A Soleimani 
Published: June 2015

Purpose:The aim of the current study is to compare EBT and EBT3 RadioChromic films in dosimetry of radiotherapy fields for treatment of parotid cancer.Methods:The calibrations of EBT and EBT3 films were performed with the same setups for doses ranging from 0.2 Gy to 5 Gy using 6 MV photon beam of a Siemens Primus linac. These films were scanned in color mode (RGB) by a Microtek (1000XL) scanner and the red color channel data was extracted. Treatment planning for parotid cancer radiation therapy was performed on a RANDO phantom. Skin dose was measured at different points in the right anterior oblique (RAO) and right posterior oblique (RPO) fields by EBT and EBT3 films.Results:Dosimetry was performed with the same conditions for the two film types for calibration and in‐phantom in parotid cancer radiotherapy. The measured net optical density (NOD) in EBT film was in some extent higher than that from EBT3 film. The minimum difference between these two films under calibration conditions was about 2.9% (for 0.2 Gy). However, the maximum difference was 35.5% (for 0.5 Gy). In the therapeutic fields of parotid cancer radiotherapy at different points, the measured dose from EBT film was higher than the EBT3 film. In these fields the minimum and maximum measured dose differences were 16.0% and 25.5%, respectively.Conclusion:With the same irradiation and reading conditions, EBT film demonstrates higher NOD than the EBT3 film. This effect may be related to the higher sensitivity of EBT film over EBT3 film. However, the obtained dose differences between these two films in low dose range can be due to the differences in fitting functions applied following the calibration process.
SU‐E‐T‐212: Comparison of TG‐43 Dosimetric Parameters of Low and High Energy Brachytherapy Sources Obtained by MCNP Code Versions of 4C, X and 5
Authors: Zehtabian M , Zaker N , Sina S , Meigooni A Soleimani 
Published: June 2015

Purpose:Different versions of MCNP code are widely used for dosimetry purposes. The purpose of this study is to compare different versions of the MCNP codes in dosimetric evaluation of different brachytherapy sources.Methods:The TG‐43 parameters such as dose rate constant, radial dose function, and anisotropy function of different brachytherapy sources, i.e. Pd‐103, I‐125, Ir‐192, and Cs‐137 were calculated in water phantom. The results obtained by three versions of Monte Carlo codes (MCNP4C, MCNPX, MCNP5) were compared for low and high energy brachytherapy sources. Then the cross section library of MCNP4C code was changed to ENDF/B‐VI release 8 which is used in MCNP5 and MCNPX codes. Finally, the TG‐43 parameters obtained using the MCNP4C‐revised code, were compared with other codes.Results:The results of these investigations indicate that for high energy sources, the differences in TG‐43 parameters between the codes are less than 1% for Ir‐192 and less than 0.5% for Cs‐137. However for low energy sources like I‐125 and Pd‐103, large discrepancies are observed in the g(r) values obtained by MCNP4C and the two other codes. The differences between g(r) values calculated using MCNP4C and MCNP5 at the distance of 6cm were found to be about 17% and 28% for I‐125 and Pd‐103 respectively. The results obtained with MCNP4C‐revised and MCNPX were similar. However, the maximum difference between the results obtained with the MCNP5 and MCNP4C‐revised codes was 2% at 6cm.Conclusion:The results indicate that using MCNP4C code for dosimetry of low energy brachytherapy sources can cause large errors in the results. Therefore it is recommended not to use this code for low energy sources, unless its cross section library is changed. Since the results obtained with MCNP4C‐revised and MCNPX were similar, it is concluded that the difference between MCNP4C and MCNPX is their cross section libraries.
SU‐E‐T‐215: Comparison of VMAT‐SABR Treatment Plans with Flattened Filter (FF) Beam and Flattening Filter‐Free (FFF) Beam for Localized Prostate Cancer
Authors: Chung J , Kim J , Kang S , Suh T 
Published: June 2015

Purpose:The purpose of this study is to access VMAT‐SABR plan using flattening filter (FF) and flattening filter‐free (FFF) beam, and compare the verification results for all pretreatment plans.Methods:SABR plans for 20 prostate patients were optimized in the Eclipse treatment planning system. A prescription dose was 42.7 Gy/7 fractions. Four SABR plans for each patient were calculated using Acuros XB algorithm with both FF and FFF beams of 6‐ and 10‐MV. The dose‐volume histograms (DVH) and technical parameters were recorded and compared. A pretreatment verification was performed and the gamma analysis was used to quantify the agreement between calculations and measurements.Results:For each patient, the DVHs are closely similar for plans of four different beams. There are small differences showed in dose distributions and corresponding DVHs when comparing the each plan related to the same patient. Sparing on bladder and rectum was slightly better on plans with 10‐MV FF and FFF than with 6‐MV FF and FFF, but this difference was negligible. However, there was no significance in the other OARs. The mean agreement of 3%/3mm criteria was higher than 97% in all plans. The mean MUs and deliver time employed was 1701±101 and 3.02±0.17 min for 6‐MV FF, 1870±116 and 1.69±0.08 min for 6‐MV FFF, 1471±86 and 2.68±0.14 min for 10‐MV FF, and 1619±101 and 0.98±0.04 min for 10‐MV FFF, respectively.Conclusion:Dose distributions on prostate SABR plans using FFF beams were similar to those generated by FF beams. However, the use of FFF beam offers a clear benefit in delivery time when compared to FF beam. Verification of pretreatment also represented the acceptable and comparable results in all plans using FF beam as well as FFF beam. Therefore, this study suggests that the use of FFF beam is feasible and efficient technique for prostate SABR.
SU‐E‐T‐223: Computed Radiography Dose Measurements of External Radiotherapy Beams
Authors: Aberle C , Kapsch R 
Published: June 2015

Purpose:To obtain quantitative, two‐dimensional dose measurements of external radiotherapy beams with a computed radiography (CR) system and to derive volume correction factors for ionization chambers in small fields.Methods:A commercial Kodak ACR2000i CR system with Kodak Flexible Phosphor Screen HR storage foils was used. Suitable measurement conditions and procedures were established. Several corrections were derived, including image fading, length‐scale corrections and long‐term stability corrections. Dose calibration curves were obtained for cobalt, 4 MV, 8 MV and 25 MV photons, and for 10 MeV, 15 MeV and 18 MeV electrons in a water phantom. Inherent measurement inhomogeneities were studied as well as directional dependence of the response. Finally, 2D scans with ionization chambers were directly compared to CR measurements, and volume correction factors were derived.Results:Dose calibration curves (0.01 Gy to 7 Gy) were obtained for multiple photon and electron beam qualities. For each beam quality, the calibration curves can be described by a single fit equation over the whole dose range. The energy dependence of the dose response was determined. The length scale on the images was adjusted scan‐by‐scan, typically by 2 percent horizontally and by 3 percent vertically. The remaining inhomogeneities after the system's standard calibration procedure were corrected for. After correction, the homogeneity is on the order of a few percent. The storage foils can be rotated by up to 30 degrees without a significant effect on the measured signal. First results on the determination of volume correction factors were obtained.Conclusion:With CR, quantitative, two‐dimensional dose measurements with a high spatial resolution (sub‐mm) can be obtained over a large dose range. In order to make use of these advantages, several calibrations, corrections and supporting measurements are needed.This work was funded by the European Metrology Research Programme (EMRP) project HLT09 MetrExtRT Metrology for Radiotherapy using Complex Radiation Fields.
SU‐E‐T‐224: Considerations for the Proper Treatment of Multiple Cranial Metastases with Single Isocenter Volumetric Modulated Arc Therapy
Authors: Audet C , Poffenbarger B , Hwang A 
Published: June 2015

Purpose:To investigate some limitations of single isocenter VMAT for cranial multiple met cases.Methods:A single isocenter VMAT plan (Varian, Eclipse AAA10 commissioned down to 1 cm) was designed for two 7mm diameter spherical targets in a rectangular Solid Water (Gammex) phantom. The targets were separated by a distance of 6cm and the isocenter was centered in one of the targets. The plan was delivered (Varian, Truebeam STx) three separate times with different artificial couch angle errors of 0, 0.5 and 1 degree. The coronal dose distributions were measured with calibrated EBT3 film placed at mid‐phantom. EBT3 film dosimetry was also performed on the delivery of separate multiple arc vmat plans to targets below 6mm in diameter.Results:Measurements of the sup/inf dose profiles through the high dose distributions show no movement of the central axis high dose region and shifts of the high dose region intended for the off‐axis target. For the 1 degree rotation error, the high dose region was shifted 1.04mm from the target. This corresponds to the shift expected from triangulation (60mmxTan(1deg)=1.047mm). Furthermore, a streak of 10% interleaf leakage dose was observed and is likely a Result of the off axis target traveling a wide path such that a long length of MLC is exposed for the whole arc. The calculated dose was about 10% to 15% low compared to that measured on film for a 5mm diameter target.Conclusion:Judicious use of additional margin for off axis targets or limits on the span of multiple mets treated with one isocenter is recommended. The magnitude of the margin should be based on the rotational errors evaluated for the positioning system and the distance of the target from the isocenter. A lower limit of lesion size that can be accurately treated with VMAT should be determined.
SU‐E‐T‐230: Creating a Large Number of Focused Beams with Variable Patient Head Tilt to Improve Dose Fall‐Off for Brain Radiosurgery
Authors: Chiu J , Ma L 
Published: June 2015

Purpose:To develop a treatment delivery and planning strategy by increasing the number of beams to minimize dose to brain tissue surrounding a target, while maximizing dose coverage to the target.Methods:We analyzed 14 different treatment plans via Leksell PFX and 4C. For standardization, single tumor cases were chosen. Original treatment plans were compared with two optimized plans. The number of beams was increased in treatment plans by varying tilt angles of the patient head, while maintaining original isocenter and the beam positions in the x‐, y‐ and z‐axes, collimator size, and beam blocking. PFX optimized plans increased beam numbers with three pre‐set tilt angles, 70, 90, 110, and 4C optimized plans increased beam numbers with tilt angles increasing arbitrarily from range of 30 to 150 degrees. Optimized treatment plans were compared dosimetrically with original treatment plans.Results:Comparing total normal tissue isodose volumes between original and optimized plans, the low‐level percentage isodose volumes decreased in all plans. Despite the addition of multiple beams up to a factor of 25, beam‐on times for 1 tilt angle versus 3 or more tilt angles were comparable (<1 min.). In 64% (9/14) of the studied cases, the volume percentage decrease by >5%, with the highest value reaching 19%. The addition of more tilt angles correlates to a greater decrease in normal brain irradiated volume. Selectivity and coverage for original and optimized plans remained comparable.Conclusion:Adding large number of additional focused beams with variable patient head tilt shows improvement for dose fall‐off for brain radiosurgery. The study demonstrates technical feasibility of adding beams to decrease target volume