bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐194: Commissioning of Monaco Treatment Planning System On An Elekta VersaHD Linear Accelerator
Authors: Narayanasamy G , Bosse C , Saenz D , Cruz W , Mavroidis P , Papanikolaou N , Stathakis S 
Published: June 2015

Purpose:The Monaco treatment planning system (TPS) uses a Monte‐Carlo algorithm based dose computation engine to model the photon beams of a linear accelerator. The aim is to perform verification of Monaco TPS beam modeling of a Elekta VersaHD linac with 6MV, 6MV FFF, 10 MV, 10MV FFF, 18MV photon beams and 160 multileaf collimators (MLC) with a projected width of 5‐mm at the isocenter.Methods:A series of dosimetric tests were performed to validate Monaco calculated beams including point dose measurement in water with and without heterogeneity and 2‐dimensional dose distributions on a Delta4 bi‐planar diode dosimeter array (Scandidos, Uppsala, Sweden). 3D conformal beams of different field sizes, source‐to‐surface distances, wedges, and gantry angles were delivered onto a phantom consisting of several plastic water and Styrofoam slabs. Point dose measurements were verified with a PTW 31013 Semiflex 0.3 cc ionization chamber (PTW, Freiburg, Germany). In addition, 8 step and shoot intensity modulated radiotherapy (IMRT) and volumetric modulated arc radiotherapy (VMAT) beams included in the Monaco TPS commissioning suite were verified against measurements on Delta4 to test and fine tune parameters in the beam model. IMRT verification was computed using gamma analysis with dose difference and distance‐to‐agreement criteria of 3%/3mm with a dose threshold of 10%.Results:Point dose measurements agreed within 2% in the homogeneous phantom and within 3% in the heterogeneous phantom for all photon energies. IMRT beams yielded a passing percentage of 99.1±1.1% in the gamma analysis which is well above the institutional passing threshold of 90%.Conclusion:Monaco TPS commissioning was successfully performed for all the photon energies on the Elekta VersaHD linac prior to clinical usage.
SU‐E‐T‐196: Comparative Analysis of Surface Dose Measurements Using MOSFET Detector and Dose Predicted by Eclipse ‐ AAA with Varying Dose Calculation Grid Size
Authors: Badkul R , Nejaiman S , Pokhrel D , Jiang H , Kumar P 
Published: June 2015

Purpose:Skin dose can be the limiting factor and fairly common reason to interrupt the treatment, especially for treating head‐and‐neck with Intensity‐modulated‐radiation‐therapy(IMRT) or Volumetrically‐modulated ‐ arc‐therapy (VMAT) and breast with tangentially‐directed‐beams. Aim of this study was to investigate accuracy of near‐surface dose predicted by Eclipse treatment‐planning‐system (TPS) using Anisotropic‐Analytic Algorithm (AAA)with varying calculation grid‐size and comparing with metal‐oxide‐semiconductor‐field‐effect‐transistors(MOSFETs)measurements for a range of clinical‐conditions (open‐field,dynamic‐wedge, physical‐wedge, IMRT,VMAT).Methods:QUASAR™‐Body‐Phantom was used in this study with oval curved‐surfaces to mimic breast, chest wall and head‐and‐neck sites.A CT‐scan was obtained with five radio‐opaque markers(ROM) placed on the surface of phantom to mimic the range of incident angles for measurements and dose prediction using 2mm slice thickness.At each ROM, small structure(1mmx2mm) were contoured to obtain mean‐doses from TPS.Calculations were performed for open‐field,dynamic‐wedge,physical‐wedge,IMRT and VMAT using Varian‐21EX,6&15MV photons using twogrid‐sizes:2.5mm and 1mm.Calibration checks were performed to ensure that MOSFETs response were within ±5%.Surface‐doses were measured at five locations and compared with TPS calculations.Results:For 6MV: 2.5mm grid‐size,mean calculated doses(MCD)were higher by 10%(±7.6),10%(±7.6),20%(±8.5),40%(±7.5),30%(±6.9) and for 1mm grid‐size MCD were higher by 0%(±5.7),0%(±4.2),0%(±5.5),1.2%(±5.0),1.1% (±7.8) for open‐field,dynamic‐wedge,physical‐wedge,IMRT,VMAT respectively.For 15MV: 2.5mm grid‐size,MCD were higher by 30%(±14.6),30%(±14.6),30%(±14.0),40%(±11.0),30%(±3.5)and for 1mm grid‐size MCD were higher by 10% (±10.6), 10%(±9.8),10%(±8.0),30%(±7.8),10%(±3.8) for open‐field, dynamic‐wedge, physical‐wedge, IMRT, VMAT respectively.For 6MV, 86% and 56% of all measured values agreed better than ±20% for 1mm and 2.5mm grid‐sizes respectively. For 18MV, 56% and 18% of all measured‐values agreed better than ±20% for 1mm and 2.5mm grid‐sizes respectively.Conclusion:Reliable Skin‐dose calculations by TPS can be very difficult due to steep dose‐gradient and inaccurate beam‐modelling in buildup region.Our results showed that Eclipse over‐estimates surface‐dose.Impact of grid‐size is also significant,surface‐dose increased up to 40% from 1mm to 2.5mm,however, 1mm calculated‐values closely agrees with measurements. Due to large uncertnities in skin‐dose predictions from TPS,outmost caution must be exercised when skin dose is evaluated,a sufficiently smaller grid‐size(1mm)can improve the accuracy and MOSFETs can be used for verification.
SU‐E‐T‐198: Comparison Between a PTW MicroDiamond Dosimeter and a Markus Chamber in a 62 MeV/n Carbon Ion Beam
Authors: Rossomme S , Hopfgartner J , Delor A , Vynckier S , Palmans H 
Published: June 2015

Purpose:To investigate the linear energy transfer (LET) dependence of a PTW Freiburg microDiamond dosimeter, we compared its response to the response of a plane‐parallel Markus chamber in a 62 MeV/n mono‐energetic carbon ion beam.Methods:The response of both detectors has been studied as a function of depth in graphite by adding or removing graphite plates in front of the detectors. To account for fluctuations of the beam, we used two setups with different monitor chambers. The depth of the effective point of measurement of both detectors has been converted into a graphite equivalent depth using ICRU Report 73 data. As recommended by IAEA TRS‐398, the response of the Markus chamber has been corrected for temperature, pressure, polarity effects and ion recombination. The latter required an additional experiment; to quantify the effect of volume recombination and initial recombination, measurements have been performed at different voltages and different dose rates.Results:As expected, the dominant process leading to ion recombination for carbon ion beam is the initial recombination. At the entrance, the ion recombination correction equals 1.1% and the value is approximately constant in the plateau region. Due to the increase of the LET in the Bragg peak region, we observe a strong increase of the ion recombination correction, up to 6.1% at the distal edge. Comparison between the microDiamond response and the Markus chamber response shows good agreement in the plateau region. However, we observe a 13.6% under response of the microDiamond in the Bragg peak.Conclusion:Increasing between 1% and 6%, the depth dependent ion recombination correction has to be applied to the Markus response. The comparison between the microDiamond and the Markus chamber indicates that there is an under‐response of the microDiamond in the vicinity of the Bragg peak due to the increased LET.
SU‐E‐T‐203: Comparison of a Commercial MRI‐Linear Accelerator Based Monte Carlo Dose Calculation Algorithm and Geant4
Authors: Ahmad S , Sarfehnia A , Paudel M , Sahgal A , Hissoiny S , Keller B 
Published: June 2015

Purpose:An MRI‐linear accelerator is currently being developed by the vendor Elekta™. The treatment planning system that will be used to model dose for this unit uses a Monte Carlo dose calculation algorithm, GPUMCD, that allows for the application of a magnetic field. We tested this radiation transport code against an independent Monte‐Carlo toolkit Geant4 (v.4.10.01) both with and without the magnetic field applied.Methods:The setup comprised a 6 MeV mono‐energetic photon beam emerging from a point source impinging on a homogeneous water phantom at 100 cm SSD. The comparisons were drawn from the percentage depth doses (PDD) for three different field sizes (1.5 × 1.5 cm2, 5 × 5 cm2, 10 × 10 cm2) and dose profiles at various depths. A 1.5 T magnetic field was applied perpendicular to the direction of the beam. The transport thresholds were kept the same for both codes.Results:All of the normalized PDDs and profiles agreed within ± 1 %. In the presence of the magnetic field, PDDs rise more quickly reducing the depth of maximum dose. Near the beam exit point in the phantom a hot spot is created due to the electron return effect. This effect is more pronounced for the larger field sizes. Profiles selected parallel to the external field show no effect, however, the ones selected perpendicular to the direction of the applied magnetic field are shifted towards the direction of the Lorentz force applied by the magnetic field on the secondary electrons. It is observed that these profiles are not symmetric which indicates a lateral build up of the dose.Conclusion:There is a good general agreement between the PDDs/profiles calculated by both algorithms thus far. We are proceeding towards clinically relevant comparisons in a heterogeneous phantom for polyenergetic beams.Funding for this work has been provided by Elekta.
SU‐E‐T‐204: Comparison of Absorbed‐Dose to Water in High‐Energy Photon Beams Based On Addendum AAPM TG‐51, IAEA TRS‐398, and JSMP 12
Authors: Kinoshita N , Oguchi H , Kita A , Yoshioka C , Sasamoto K , Nishimoto Y , Adachi T , Shioura H , Kimura H 
Published: June 2015

Purpose:Several clinical reference dosimetry protocols for absorbed‐dose to water have recently been published: The American Association of Physicists in Medicine (AAPM) published an Addendum to the AAPM's TG‐51 (Addendum TG‐51) in April 2014, and the Japan Society of Medical Physics (JSMP) published the Japan Society of Medical Physics 12 (JSMP12), a clinical reference dosimetry protocol, in September 2012. This investigation compared and evaluated the absorbed‐dose to water of high‐energy photon beams according to Addendum TG‐51, International Atomic Energy Agency Technical Report Series No. 398 (TRS‐398), and JSMP12.Methods:Differences in the respective beam quality conversion factors with Addendum TG‐51, TRS‐398, and JSMP12 were analyzed and the absorbed‐dose to water using 6‐ and 10‐MV photon beams was measured according to the protocols recommended in Addendum TG‐51, TRS‐398, and JSMP12. The measurements were conducted using two Farmer‐type ionization chambers, Exradin A12 and PTW 30013.Results:The beam quality conversion factors for both the 6‐ and 10‐MV photon beams with Addendum TG‐51 were within 0.6%, in agreement with the beam quality conversion factors with TRS‐398 and JSMP12. The Exradin A12 provided an absorbed‐dose to water ratio from 1.003 to 1.006 with TRS‐398 / Addendum TG‐51 and from 1.004 to 1.005 with JSMP 12 / Addendum TG‐51, whereas the PTW 30013 provided a ratio of 1.001 with TRS‐398 / Addendum TG‐51 and a range from 0.997 to 0.999 with JSMP 12 / Addendum TG‐51.Conclusion:Despite differences in the beam quality conversion factor, no major differences were seen in the absorbed‐dose to water with Addendum TG‐51, TRS‐398, and JSMP12. However, Addendum TG‐51 provides the most recent data for beam quality conversion factors based on Monte Carlo simulation and greater detail for the measurement protocol. Therefore, the absorbed‐dose to water measured with Addendum TG‐51 is an estimate with less uncertainty.
SU‐E‐T‐209: Comparison of Plan Quality Between Arm Avoidance (AA) Vs. Non Arm Avoidance VMAT Planning Techniques for Breast Cancer Patients with Bilateral Implant Reconstructions Receiving Postmastectomy Radiation
Authors: Kuo L , Ballangrud A , Ho A , Mechalakos J , Li G , Hong L 
Published: June 2015

Purpose:Breast cancer patients with bilateral implant reconstructions who require postmastectomy radiotherapy can pose unique treatment planning challenges. The use of VMAT may provide advantages over conventional tangent or multi‐beam IMRT techniques. Moreover, daily setup uncertainly of the arm position, however, could have significant impact on accurate dose delivery. This study compares the plan qualities between non‐AA and AA VMAT techniques.Methods:Three breast cancer patients receiving left chest wall and regional nodal irradiation with bilateral implant reconstructions were studied. PTV included chest wall and IMNs (PTV‐CW), and supraclavicular and axillary lymph nodes (PTV‐SCV). For each patient, one non‐AA VMAT plan (VMAT‐S) with 4 partial arcs encompassing the ipsilateral arm and three AA VMAT plans where no arcs were entering or existing through the ipsilateral arm were generated. VMAT‐AA1 uses 2 arcs for PTV‐CW and 2 arcs for PTV‐SCV. VMAT‐AA2 used two static fields for PTV‐SCV with 2 arcs for PTV‐CW. VMAT‐AA3 used 2 narrow arcs for PTV‐CW and 2 long arcs for all PTVs. Prescription dose (PD) was 50 Gy (25 fractions). All plans were normalized to have 95% of PD to 95 % of PTV. PTV dose inhomogeneity and dose to the heart, left lung, right thyroid dose and left humerus were evaluated.Results:For VMAT‐S, VMAT‐AA1, VMAT‐AA2 and VMAT‐AA3, respectively, the average and standard deviation (in Gy unless specified otherwise) of PTV D05 are 54.7±0.9, 55.9±0.4, 56.7±0.7 and 55.7±0.4; mean Heart dose: 7.1±0.7, 7.2±0.8, 7.3±0.9 and 6.9±1.0; left lung V20Gy (in %): 28.1±1.0, 28.8+2.2, 32.2±4.1 and 27.8±2.0; mean right thyroid dose: 8.1±0.6, 5.1±2.1, 2.1±0.4 and 5.0±2.0; mean left humerus dose: 20.0±4.4,15.6±4.4, 15.2±8.2 and 15.3±4.6.Conclusion:AA VMAT can produce acceptable clinical plans while eliminating dosimetric impact related to arm setup uncertainty. These data require validation in larger planning studies prior to routine clinical implantation.
SU‐E‐T‐219: Comprehensive Validation of the Electron Monte Carlo Dose Calculation Algorithm in RayStation Treatment Planning System for An Elekta Linear Accelerator with AgilityTM Treatment Head
Authors: Wang Yi , Park Yang‐Kyun , Doppke Karen P. 
Published: June 2015

Purpose:This study evaluated the performance of the electron Monte Carlo dose calculation algorithm in RayStation v4.0 for an Elekta machine with Agility™ treatment head.Methods:The machine has five electron energies (6–8 MeV) and five applicators (6×6 to 25×25 cm 2). The dose (cGy/MU at dmax), depth dose and profiles were measured in water using an electron diode at 100 cm SSD for nine square fields ≥2×2 cm2 and four complex fields at normal incidence, and a 14×14 cm2 field at 15° and 30° incidence. The dose was also measured for three square fields ≥4×4 cm2 at 98, 105 and 110 cm SSD. Using selected energies, the EBT3 radiochromic film was used for dose measurements in slab‐shaped inhomogeneous phantoms and a breast phantom with surface curvature. The measured and calculated doses were analyzed using a gamma criterion of 3%/3 mm.Results:The calculated and measured doses varied by <3% for 116 of the 120 points, and <5% for the 4×4 cm2 field at 110 cm SSD at 9–18 MeV. The gamma analysis comparing the 105 pairs of in‐water isodoses passed by >98.1%. The planar doses measured from films placed at 0.5 cm below a lung/tissue layer (12 MeV) and 1.0 cm below a bone/air layer (15 MeV) showed excellent agreement with calculations, with gamma passing by 99.9% and 98.5%, respectively. At the breast‐tissue interface, the gamma passing rate is >98.8% at 12–18 MeV. The film results directly validated the accuracy of MU calculation and spatial dose distribution in presence of tissue inhomogeneity and surface curvature ‐ situations challenging for simpler pencil‐beam algorithms.Conclusion:The electron Monte Carlo algorithm in RayStation v4.0 is fully validated for clinical use for the Elekta Agility™ machine. The comprehensive validation included small fields, complex fields, oblique beams, extended distance, tissue inhomogeneity and surface curvature.
SU‐E‐T‐220: Computational Accuracy of Adaptive Convolution (AC) and Collapsed Cone Convolution (CCC) Algorithms in the Presence of Air Gaps
Authors: Oyewale S , Pokharel S , Rana S 
Published: June 2015

Purpose:To compare the percentage depth dose (PDD) computational accuracy of Adaptive Convolution (AC) and Collapsed Cone Convolution (CCC) algorithms in the presence of air gaps.Methods:A 30×30×30 cm3 solid water phantom with two 5cm air gaps was scanned with a CT simulator unit and exported into the Phillips Pinnacle™ treatment planning system. PDDs were computed using the AC and CCC algorithms. Photon energy of 6 MV was used with field sizes of 3×3 cm2, 5×5 cm2, 10×10 cm2, 15×15 cm2, and 20×20 cm2. Ionization chamber readings were taken at different depths in water for all the field sizes. The percentage differences in the PDDs were computed with normalization to the depth of maximum dose (dmax). The calculated PDDs were then compared with measured PDDs.Results:In the first buildup region, both algorithms overpredicted the dose for all field sizes and under‐predicted for all other subsequent buildup regions. After dmax in the three water media, AC under‐predicted the dose for field sizes 3×3 and 5×5 cm2 and overpredicted for larger field sizes, whereas CCC under‐predicted for all field sizes. Upon traversing the first air gap, AC showed maximum differences of –3.9%, −1.4%, 2.0%, 2.5%, 2.9% and CCC had maximum differences of −3.9%, −3.0%,–3.1%, −2.7%, −1.8% for field sizes 3×3, 5×5, 10×10, 15×15, and 20×20 cm2 respectively.Conclusion:The effect of air gaps causes a significant difference in the PDDs computed by both the AC and CCC algorithms in secondary build‐up regions. AC computed larger values for the PDDs except at smaller field sizes. For CCC, the size of the errors in prediction of the PDDs has an inverse relationship with respect to field size. These effects should be considered in treatment planning where significant air gaps are encountered.
SU‐E‐T‐221: Computational Evaluation of Proton Induced Gain in a Portable Faraday Cup
Authors: Marshall S , Hodgdon A , Currier B 
Published: June 2015

Purpose:The design of a new Portable Faraday Cup (PFC) used to calibrate proton accelerators was evaluated for energies between 50 and 220 MeV. Monte Carlo simulations performed in Geant4–10.0 were used to evaluate experimental results and reduce the relative detector error for this vacuum‐less and low mass system, and invalidate current MCNP releases.Methods:The detector construction consisted of a copper conductor coated with an insulator and grounded with silver. Monte Carlo calculations in Geant4 were used to determine the net charge per proton input (gain) as a function of insulator thickness and beam energy. Kapton was chosen as the insulating material and was designed to capture backscattered electrons. Charge displacement from/into Kapton was assumed to follow a linear proportionality to the origin/terminus depth toward the outer ground layer. Kapton thicknesses ranged from 0 to 200 microns, proton energies were set to match empirical studies ranging from 70 to 250 MeV. Each setup was averaged over 1 million events using the FTFP_BERT 2.0 physics list.Results:With increasing proton energy, the gain of Cu+KA gradually converges to the limit of pure copper, with relative error between 1.52% and 0.72%. The Ag layer created a more diverging behavior, accelerating the flux of negative charge into the device and increasing relative error when compared to pure copper from 1.21% to 1.63%.Conclusion:Gain vs. beam energy signatures were acquired for each device. Further analysis reveals proportionality between insulator thickness and measured gain, albeit an inverse proportionality between beam energy and in‐flux of electrons. Increased silver grounding layer thickness also decreases gain, though the relative error expands with beam energy, contrary to the Kapton layer.
SU‐E‐T‐222: Computational Optimization of Monte Carlo Simulation On 4D Treatment Planning Using the Cloud Computing Technology
Authors: Chow J 
Published: June 2015

Purpose:This study evaluated the efficiency of 4D lung radiation treatment planning using Monte Carlo simulation on the cloud. The EGSnrc Monte Carlo code was used in dose calculation on the 4D‐CT image set.Methods:4D lung radiation treatment plan was created by the DOSCTP linked to the cloud, based on the Amazon elastic compute cloud platform. Dose calculation was carried out by Monte Carlo simulation on the 4D‐CT image set on the cloud, and results were sent to the FFD4D image deformation program for dose reconstruction. The dependence of computing time for treatment plan on the number of compute node was optimized with variations of the number of CT image set in the breathing cycle and dose reconstruction time of the FFD4D.Results:It is found that the dependence of computing time on the number of compute node was affected by the diminishing return of the number of node used in Monte Carlo simulation. Moreover, the performance of the 4D treatment planning could be optimized by using smaller than 10 compute nodes on the cloud. The effects of the number of image set and dose reconstruction time on the dependence of computing time on the number of node were not significant, as more than 15 compute nodes were used in Monte Carlo simulations.Conclusion:The issue of long computing time in 4D treatment plan, requiring Monte Carlo dose calculations in all CT image sets in the breathing cycle, can be solved using the cloud computing technology. It is concluded that the optimized number of compute node selected in simulation should be between 5 and 15, as the dependence of computing time on the number of node is significant.
SU‐E‐T‐229: Craniospinal Radiotherapy Planning with VMAT, Two First Years Experience
Authors: Lliso F , Carmona V , Gimeno J , Candela‐Juan C , Bautista J , Richart J , Perez‐Calatayud J 
Published: June 2015

Purpose:To describe how we moved to VMAT in the craniospinal radiotherapy planning process, the actual procedure details, and the results for the patients treated.Methods:Twelve patients underwent craniospinal irradiation with the new procedure, based on the paper by Lee et al. (IJROBP 82, 2012), with some additional modifications. Patients were treated in supine position in Varian Clinac iX linacs with 6 MV RapidArc; prescription doses ranged from 23.4 to 40 Gy (13 to 20 fractions); depending on the PTV length, 2 or 3 isocenters were used, all coordinates being equal except the longitudinal one, setting a few centimeter‐long overlapping region; 2 arcs (RA) sharing isocentre for the cranial region, RA1 encompassing cranium and superior spinal region, and RA2 intended to improve conformity, only for cranium; for spine, 1 or 2 isocenters were employed; optimization was performed with Eclipse (V 13.0) using AAA algorithm, establishing sets of optimization parameters to give high conformity while sparing OAR. In pediatric patients, homogeneous irradiation of the vertebrae was also required.Conformity (CI) and heterogeneity (HI) indices (same as Lee et al.), and mean and maximum doses for OAR were calculated. Several pre‐treatment verification methods were used: Octavius4D (PTW) for each isocentre, point dose at the junction region, Portal Dosimetry (when possible), and independent MU verification software (Diamond, PTW).Results:CI median value was 1.02 (0.99–1.07) and HI, 1.07 (1.06–1.09); a great reduction was observed for CI and OAR mean doses with respect to Lee et al. data; median maximum eye lens dose was 7.3 Gy (4.0–12.0); mean LungV20Gy was 1.9%; in children, vertebrae were homogeneously irradiated (D95%=20.8 Gy, Dmean= 23.2 Gy).All pre‐treatment verifications were found within our action levels except for Portal Dosimetry.Conclusion:A RapidArc planning process for craniospinal axis irradiation has been implemented with significant advantages on conformity, homogeneity, feasibility and efficiency. and increase brain tissue sparing. Variations in volume decrease may be related to shape or location of the tumor.