bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐T‐193: Evaluation of a GPU‐Based Fast Monte Carlo Code for Proton Therapy Biological Optimization
Authors: Taleei R , Peeler C , Qin N , Jiang S , Jia X 
Published: July 2016

Purpose:Biological treatment plan optimization is of great interest for proton therapy. It requires extensive Monte Carlo (MC) simulations to compute physical dose and biological quantities. Recently, a gPMC package was developed for rapid MC dose calculations on a GPU platform. This work investigated its suitability for proton therapy biological optimization in terms of accuracy and efficiency.Methods:We performed simulations of a proton pencil beam with energies of 75, 150 and 225 MeV in a homogeneous water phantom using gPMC and FLUKA. Physical dose and energy spectra for each ion type on the central beam axis were scored. Relative Biological Effectiveness (RBE) was calculated using repair‐misrepair‐fixation model. Microdosimetry calculations were performed using Monte Carlo Damage Simulation (MCDS).Results:Ranges computed by the two codes agreed within 1 mm. Physical dose difference was less than 2.5 % at the Bragg peak. RBE‐weighted dose agreed within 5 % at the Bragg peak. Differences in microdosimetric quantities such as dose average lineal energy transfer and specific energy were < 10%. The simulation time per source particle with FLUKA was 0.0018 sec, while gPMC was ∼ 600 times faster.Conclusion:Physical dose computed by FLUKA and gPMC were in a good agreement. The RBE differences along the central axis were small, and RBE‐weighted dose difference was found to be acceptable. The combined accuracy and efficiency makes gPMC suitable for proton therapy biological optimization.
SU‐F‐T‐196: Hypo‐Fractionation with Intensity Modulated Proton Therapy for Unilateral Metallic Prosthesis Prostate Cancer Patients
Authors: Rana S , Zheng Y , Zhang Y , Pokharel  , Cheng C , Park S 
Published: July 2016

Purpose:The purpose of this study is to investigate the dosimetric feasibility of hypo‐fractionated intensity modulated proton therapy (IMPT) for unilateral metallic prosthesis prostate cancer patients based on proton collaborative group (PCG)‐GU002‐10 (NCT01230866) protocol criteria.Methods:A total of five unilateral metallic prosthesis prostate cancer cases were included in this retrospective study. For each case, IMPT plans were generated for treatment to be delivered with 7.6 Gy[RBE] per fraction in 5 fractions per week for a total dose of 38 Gy(RBE). Each plan was generated using two anterior‐oblique beams and one lateral beam. Treatment plans were optimized with an objective meeting PCG‐GU002‐10 (NCT01230866) protocol criteria: (i) planning target volume (PTV): D99.5% > 36.1 Gy[RBE], (ii) rectum: V24 < 35%, V33.6 < 10%, (iii) bladder: V39 < 8 cc, and (iv) femoral head: V23 < 1cc.Results:All five cases satisfied PTV D99.5% (average=36.82 Gy[RBE]; range, 36.36–37.13 Gy[RBE]). PTV D95% ranged from 36.66 Gy[RBE] to 38.65 Gy[RBE] and PTV V100 ranged from 95.47% to 97.95%. For the rectum, V24 was less than 35% (average=14.07 Gy[RBE]; range, 6.22–18.42%, whereas V33.6 Gy[RBE] was less than 10% (average=6.83; range, 3.06 – 9.15%). Rectal mean dose ranged from 4.22 Gy[RBE] to 9.97 Gy[RBE]. For the bladder, V39 was found to be less than 8 cc (average=3.69 cc; range, 0.19–7.68 cc). Bladder mean dose ranged from 4.22 Gy[RBE] to 18.83 Gy[RBE]. For the femoral head, V23 was 0 in all five cases.Conclusion:All five unilateral metallic prosthesis prostate cancer IMPT plans generated with one lateral and two anterior‐oblique beams satisfied the dosimetric criteria of PCG‐GU002‐10 (NCT01230866) protocol.
SU‐F‐T‐204: A Preliminary Approach of Reducing Contralateral Breast and Heart Dose in Left Sided Whole Breast Cancer Patients Utilizing Proton Beams
Authors: Islam M , Algan O , Jin H , Ahmad S , Hossain S 
Published: July 2016

Purpose:To investigate the plan quality and feasibility of a hybrid plan utilizing proton and photon fields for superior coverage in the internal mammary (IM) and supraclavicular (S/C) regions while minimizing heart and contralateral breast dose for the left‐sided whole breast cancer patient treatment.Methods:This preliminary study carried out on single left‐sided intact breast patient involved IM and S/C nodes. The IM and S/C node fields of the 5‐Field 3DCRT photon‐electron base plan were replaced by two proton fields. These two along with two Field‐in‐Field tangential photon fields were optimized for comparable dose coverage. The treatment plans were done using Eclipse TPS for the total dose of 46Gy in 23 fractions with 95% of the prescription dose covering 95% of the RTOG PTV. The 3DCRT photon‐electron and 4‐Field photon‐proton hybrid plans were compared for the PTV dose coverage as well as dose to OARs.Results:The overall RTOG PTV coverage for proton‐hybrid and 3DCRT plan was comparable (95% of prescription dose covers 95% PTV volume). In proton‐hybrid plan, 99% of IM volume received 100% dose whereas in 3DCRT only 77% received 100% dose. For S/C regions, 97% and 77% volume received 100% prescription dose in proton‐hybrid and 3DCRT plans, respectively. The heart mean dose, V3Gy(%), and V5Gy(%) was 2.2Gy, 14.4%, 9.8% for proton‐hybrid vs. 4.20 Gy, 21.5%, and 39% for 3DCRT plan, respectively. The maximum dose to the contralateral breast was 39.75Gy for proton‐hybrid while 56.87Gy for 3DCRT plan. The mean total lung dose, V20Gy(%), and V30Gy(%) was 5.68Gy, 11.3%, 10.5% for proton‐hybrid vs. 5.90Gy, 9.8%, 7.2% for 3DCRT, respectively.Conclusion:The protonhybrid plan can offer better dose coverage to the involved lymphatic tissues while lower doses to the heart and contralateral breast. More treatment plans are currently in progress before being implemented clinically.
SU‐F‐T‐208: An Efficient Planning Approach to Posterior Fossa Tumor Bed Boosts Using Proton Pencil Beam Scanning in Fixed‐Beam Room
Authors: Ju N , Chen C , Gans S , Hug E , Cahlon O , Wolden S , Chon B , Yeh B , Tsai H , Sine K , Mah D 
Published: July 2016

Purpose:A fixed‐beam room could be underutilized in a multi‐room proton center. We investigated the use of proton pencil beam scanning (PBS) on a fixed‐beam as an alternative for posterior fossa tumor bed (PF‐TB) boost treatments which were usually treating on a gantry with uniform scanning.Methods:Five patients were treated with craniospinal irradiation (CSI, 23.4 or 36.0 Gy(RBE)) followed by a PF‐TB boost to 54 Gy(RBE) with proton beams. Three PF‐TB boost plans were generated for each patient: (1) a uniform scanning (US) gantry plan with 4–7 posterior fields shaped with apertures and compensators (2) a PBS plan using bi‐lateral and vertex fields with a 3‐mm planning organ‐at‐risk volume (PRV) expansion around the brainstem and (3) PBS fields using same beam arrangement but replacing the PRV with robust optimization considering a 3‐mm setup uncertainty.Results:A concave 54‐Gy(RBE) isodose line surrounding the brainstem could be achieved using all three techniques. The mean V95% of the PTV was 99.7% (range: 97.6% to 100%) while the V100% of the PTV ranged from 56.3% to 93.1% depending on the involvement of the brainstem with the PTV. The mean doses received by 0.05 cm3 of the brainstem were effectively identical: 54.0 Gy(RBE), 53.4 Gy(RBE) and 53.3 Gy(RBE) for US, PBS optimized with PRV, and PBS optimized with robustness plans respectively. The cochlea mean dose increased by 23% of the prescribed boost dose in average from the bi‐lateral fields used in the PBS plan. Planning time for the PBS plan with PRV was 5–10 times less than the US plan and the robustly optimized PBS plan.Conclusion:We have demonstrated that a fixed‐beam with PBS can deliver a dose distribution comparable to a gantry plan using uniform scanning. Planning time can be reduced substantially using a PRV around the brainstem instead of robust optimization.
SU‐F‐T‐213: Commissioning Results of the Prototype Active Scanning Irradiation System of Korea Heavy Ion Medical Accelerator
Authors: Kim C , Seduk J , Yang T 
Published: July 2016

Purpose:A prototype actives scanning beam delivery system was designed, manufactured and installed as a part of the Korea Heavy Ion Medical Accelerator Project. The prototype system includes the most components for steering, modulating, detecting incident beam to patient. The system was installed in MC‐50 cyclotron beam line and tested to extract the normal operation conditions.Methods:The commissioning process was completed by using 45 MeV of proton beam. To measure the beam position accuracy along the scanning magnet power supply current, 25 different spots were scanning and measured. The scanning results on GaF film were compared with the irradiation plan. Also, the beam size variation and the intensity reduction using range shifter were measured and analyzed. The results will be used for creating a conversion factors for asymmetric behavior of scanning magnets and a dose compensation factor for longitudinal direction.Results:The results show asymmetry operations on both scanning × and y magnet. In case of scanning magnet × operation, the current to position conversion factors were measured 1.69 mm/A for positive direction and 1.74 mm/A for negative direction. The scanning magnet y operation shows 1.38mm/A and 1.48 mm/A for both directions. The size of incoming beam which was 18 mm as sigma becomes larger up to 55 mm as sigma while using 10 mm of the range shifter plate. As the beam size becomes large, the maximum intensity of the was decreased. In case of using 10 mm of range shifter, the maximum intensity was only 52% compared with no range shifter insertion.Conclusion:For the appropriate operation of the prototype active scanning system, the commissioning process were performed to measure the beam characteristics variation. The obtained results would be applied on the irradiation planning software for more precise dose delivery using the active scanning system.
SU‐F‐T‐216: Evaluating Dosimetry Accuracy of a Treatment Planning System On Small Proton Fields
Authors: Zhang M , Xiao Z , Zou J , Chen T , Yue N 
Published: July 2016

Purpose:This study is aiming to identify the smallest field size for which a treatment planning system (TPS) can accurately calculate the relative dose distribution. The finding would be used as a guideline to choose the smallest proton field for clinical treatment.Methods:Mevion S250™ double scattering proton delivery system and Eclipse™ TPS (Varian) with pencil beam convolution (PBC) dose algorithm were used in this study. Square sized fields of 1 cm, 2 cm, 3 cm, 4 cm, 5 cm, and 10 cm were planned on a cubical water phantom with iso‐center placed at 10 cm depth. All beams used the same proton beam option: range 15 cm and modulation 10 cm. Dose in water was calculated without any compensator. Gafchromic™ EBT3 film and diode detectors were used to measure the central axis dose distribution and lateral dose profiles at 5 cm, 10 cm, and 14 cm depth.Results:The preliminary film measurement shows good agreement between Eclipse calculated lateral dose profiles for all tested field sizes. The differences on full width half maximum were ≤ 1 mm while the differences on the penumbras were between 1 mm and 2 mm between Eclipse and film. For the depth dose, Eclipse results matched well with film measurements for field sizes down to 2 cm2. With smaller field size of 1 cm2, Eclipse was able to predict the decreasing of SOBP due to the lack of lateral charged particle equilibrium in depth. However, it did not match the film measurement. Diode measurement results will be available at the time of presentation.Conclusion:The PBC dose algorithm in Eclipse can accurately calculate relative dose distribution in double scattered proton system for field size down to 2 cm2.
SU‐F‐T‐217: A Comprehensive Monte‐Carlo Study of Out‐Of‐Field Secondary Neutron Spectra in a Scanned‐Beam Proton Therapy Treatment Room
Authors: Englbrecht F , Trinkl S , Mares V , Ruehm W , Wielunski M , Wilkens J , Hillbrand M , Parodi K 
Published: July 2016

Purpose:To simulate secondary neutron radiation‐fields produced at different positions during phantom irradiation inside a scanning proton therapy gantry treatment room. Further, to identify origin, energy distribution and angular emission as function of proton beam energy.Methods:GEANT4 and FLUKA Monte‐Carlo codes were used to model the relevant parts of the treatment room in a gantry‐equipped pencil beam scanning proton therapy facility including walls, floor, metallic gantry‐components, patient table and the homogeneous PMMA target. The proton beams were modeled based on experimental beam ranges in water and spot shapes in air. Neutron energy spectra were simulated at 0°, 45°, 90° and 135° relative to the beam axis at 2m distance from isocenter, as well as 11×11 cm2 fields for 75MeV, 140MeV, 200MeV and for 118MeV with 5cm PMMA range‐shifter. The total neutron energy distribution was recorded for these four positions and proton energies. Additionally, the room‐components generating secondary neutrons in the room and their contributions to the total spectrum were identified and quantified.Results:FLUKA and GEANT4 simulated neutron spectra showed good general agreement in the whole energy range of 10−9 to 102 MeV. Comparison of measured spectra with the simulated contributions of the various room components helped to limit the complexity of the room model, by identifying the dominant contributions to the secondary neutron spectrum. The iron of the bending magnet and counterweight were identified as sources of secondary evaporation‐neutrons, which were lacking in simplified room models.Conclusion:Thorough Monte‐Carlo simulations have been performed to complement Bonner‐sphere spectrometry measurements of secondary neutrons in a clinical proton therapy treatment room. Such calculations helped disentangling the origin of secondary neutrons and their dominant contributions to measured spectra, besides providing a useful validation of widely used Monte‐Carlo packages in comparison to experimental data.Cluster of Excellence of the German Research Foundation (DFG) “Munich‐Centre for Advanced Photonics (MAP)”
SU‐F‐T‐219: Verification of the Accuracy of a Relative Stopping Power (RSP) to Hounsfield Unit (HU) Calibration Curve Produced for Proton Treatment Planning Using EBT3‐Gafchromic Film Dosimetry
Authors: Schnell E , Ferreira C , Ahmad S , De La Fuente Herman T 
Published: July 2016

Purpose:Accuracy of a RSP‐HU calibration curve produced for proton treatment planning is tested by comparing the treatment planning system dose grid to physical doses delivered on film by a Mevion S250 double‐scattering proton unit.Methods:A single batch of EBT3 Gafchromic film was used for calibration and measurements. The film calibration curve was obtained using Mevion proton beam reference option 20 (15cm range, 10cm modulation). Paired films were positioned at the center of the spread out Bragg peak (SOBP) in solid water. The calibration doses were verified with an ion chamber, including background and doses from 20cGy to 350cGy. Films were scanned in a flatbed Epson‐Expression 10000‐XL scanner, and analyzed using the red channel. A Rando phantom was scanned with a GE LightSpeed CT Simulator. A single‐field proton plan (Eclipse, Varian) was calculated to deliver 171cGy to the pelvis section (heterogeneous region), using a standard 4×4cm aperture without compensator, 7.89cm beam range, and 5.36cm SOBP. Varied depths of the calculated distal 90% isodose‐line were recorded and compared. The dose distribution from film irradiated between Rando slices was compared with the calculated plans using RIT v.6.2.Results:Distal 90% isodose‐line depth variation between CT scans was 2mm on average, and 4mm at maximum. Fine calculation of this variation was restricted by the dose calculation grid, as well as the slice thickness. Dose differences between calibrated film measurements and calculated doses were on average 5.93cGy (3.5%), with the large majority of differences forming a normal distribution around 3.5cGy (2%). Calculated doses were almost entirely greater than those measured.Conclusion:RSP to HU calibration curve is shown to produce distal depth variation within the margin of tolerance (±4.3mm) across all potential scan energies and protocols. Dose distribution calculation is accurate to 2–4% within the SOBP, including areas of high tissue heterogeneity.
SU‐F‐T‐222: Dose of Fetus and Infant Following Accidental Intakes of I‐131 by the Mother
Authors: Wang Y , Hu P 
Published: July 2016

Purpose:To estimate the calculation of absorbed dose to the fetus and infants from intakes of I‐131 by the mother. Thus provide some advice to the radioprotection of radioactive accident.Methods:In this clinical case, a staff of nuclear medicine accidently intake I‐131 during (10–12 weeks) and after pregnancy. The infant was born at full term, but both lobes of the thyroid gland were found to be absent (bilobar thyroid agenesis). It was suspected that the fetal thyroid agenesis may be related with mother's contamination of I‐131 during pregnancy. Urine samples for 24h were collected at different times after administered and radioactivity were measured to calculate the dose of intake I‐131. Calculate the intake I‐131 by the results of personal TLD dosimeter. We adopted the mean of two calculated results as the I‐131 intake. According to the dose of intake I‐131 by the mother, effective dose and absorbed dose of thyroid for mother, fetus and infant were calculated.Results:The intake of I‐131 was estimated for 8.18 mCi. I‐131 intake was calculated for 7.9 mCi based on data of TLD dosimeter. We adopted the mean of two results as the I‐131 intake. The final result was 8.0 mCi. Effective dose and absorbed dose of thyroid for mother were 7.3Sv and 164 Gy, effective dose and absorbed dose of thyroid for fetus were 2.035 Sv and 40.7 Gy, effective dose and absorbed dose of thyroid for infant were 16.25 Sv and 355Gy.Conclusion:The intake during pregnancy was about 1mCi. The absorbed dose of thyroid of the mother was 19.5Gy, whereas the effective of infant was estimated for 40.7Gy. The function of the mother's thyroid was normal after diagnosis. But the infant was diagnosed as bilobar thyroid agenesis.
SU‐F‐T‐228: Analysis of Multi‐Leaf Collimator Leaf Position Errors in Volumetric Modulated Arc Therapy for Nasopharyngeal Carcinoma
Authors: Li C , Yin Y 
Published: July 2016

Purpose:The purpose of this study was evaluate the position error of multileaf collimator in volumetric modulated arc therapy of nasopharyngeal carcinoma via MLC logs from Varian machines and to provide a method for detecting the leaf position accuracy.Methods:Thirty one patients with nasopharyngeal carcinoma were randomly selected. Each patient was created with two 358° arcs. The MLC errors for all arcs, arc1 and arc2, left‐bank and right‐bank leafs of each arc were evaluated.Results:99.99% of the leaf position errors of all plans were within ± 2mm. The proportion of the leaf position errors within ± 1.5mm,± 1mm and ± 0.5mm were 99.90%, 98.98% and 94.17%,respectively. The leaf position errors range of ARC1 and ARC2 were −2.95 ∼ 2.99mm and −0.22 ∼ 0.23mm (t = 2.35, P = 0.00), The proportion of the leaf position errors within ± 1mm were 98.08% and 100% for ARC1 and ARC2. The leaf position errors range of Bank A and Bank B were −2.95 ∼ 2.68mm and −2.92 ∼ 2.99mm (t = 1.64, P = 0.31), The proportion of the leaf position errors within ± 1mm were 98.97% and 99.01%.Conclusion:During the VMAT treatment for NPC, it was found that the leaf positions were in control, the Dynalog files can be used as an effective way to analysis the leaf position errors.
SU‐F‐T‐229: A Novel Method for EPID‐Based In‐Vivo Exit Dose Verification for Intensity Modulated Radiotherapy
Authors: Wu Z , Wang J , Peng J , Wang J , Hu W 
Published: July 2016

Purpose:Electronic portal imaging device (EPID) can be used to acquire a two‐dimensional exit dose distribution during treatment delivery, thus allowing the in‐vivo verification of the dose delivery through a comparison of measured portal images to predicted portal dose images (PDI). The aim of this study was to present a novel method to easily and accurately predict PDI, and to establish an EPID‐based in‐vivo dose verification method during IMRT treatments.Methods:We developed a model to determine the predicted portal dose at the same plane of the EPID detector location. The Varian EPID (aS1000) positions at 150cm source‐to‐detector‐distance (SDD), and can be used to acquire in‐vivo exit dose using Portal Dosimetry (PD) function. Our model was generated to make an equivalent water thickness represent the buildup plate of EPID. The exit dose at extend SDD plane with patient CT data in the beam can be calculated as the predicted PDI in the treatment planning system (TPS). After that, the PDI was converted to the fluence at SDD of 150cm using the inverse square law coded in MATLAB. Five head‐and‐neck and prostate IMRT patient plans contain 32 fields were investigated to evaluate the feasibility of this new method. The measured EPID image was compared with PDI using the gamma analysis.Results:The average results for cumulative dose comparison were 81.9% and 91.6% for 3%, 3mm and 4%, 4mm gamma criteria, respectively. Results indicate that the patient transit dosimetry predicted algorithm compares well with EPID measured PD doses for test situations.Conclusion:Our new method can be used as an easy and feasible tool for online EPID‐based in‐vivo dose delivery verification for IMRT treatments. It can be implemented for fast detecting those obvious treatment delivery errors for individual field and patient quality assurance.
SU‐F‐T‐236: Comparison of Two IMRT/VMAT QA Systems Using Gamma Index Analysis
Authors: Dogan N , Denissova S 
Published: July 2016

Purpose:The goal of this study is to assess differences in the Gamma index pass rates when using two commercial QA systems and provide optimum Gamma index parameters for pre‐treatment patient specific QA.Methods:Twenty‐two VMAT cases that consisted of prostate, lung, head and neck, spine, brain and pancreas, were included in this study. The verification plans have been calculated using AcurosXB(V11) algorithm for different dose grids (1.5mm, 2.5mm, 3mm). The measurements were performed on TrueBeam(Varian) accelerator using both EPID(S1000) portal imager and ArcCheck(SunNuclearCorp) devices. Gamma index criteria variation of 3%/3mm, 2%/3mm, 2%/2mm and threshold (TH) doses of 5% to 50% were used in analysis.Results:The differences in Gamma pass rates between two devices are not statistically significant for 3%/3mm, yielding pass rate higher than 95%. Increase of lower dose TH showed reduced pass rates for both devices. ArcCheck's more pronounced effect can be attributed to higher contribution of lower dose region spread. As expected, tightening criteria to 2%/2mm (TH: 10%) decreased Gamma pass rates below 95%. Higher EPID (92%) pass rates compared to ArcCheck (86%) probably due to better spatial resolution. Portal Dosimetry results showed lower Gamma pass rates for composite plans compared to individual field pass rates. This may be due to the expansion in the analyzed region which includes pixels not included in the separate field analysis. Decreasing dose grid size from 2.5mm to 1.5mm did not show statistically significant (p<0.05) differences in Gamma pass rates for both QA devices.Conclusion:Overall, both system measurements agree well with calculated dose when using gamma index criteria of 3%/3mm for a variety of VMAT cases. Variability between two systems increases using different dose GRID, TH and tighter gamma criteria and must be carefully assessed prior to clinical use.