bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐CAMPUS‐T‐03: Four‐Dimensional Dose Distribution Measurement Using Plastic Scintillator
Authors: Hashimoto M , Nishio T , Haga A , Hanada T , Kabuki S , Kozuka T , Oguchi M 
Published: July 2014

Purpose:To develop the detector for the four‐dimensional dose distribution measurement.Methods:We made the prototype detector for four‐dimensional dose distribution measurement using a cylindrical plastic scintillator (5 cm diameter) and a conical reflection grass. The plastic scintillator is used as a phantom. When the plastic scintillator is irradiated, the scintillation light was emitted according to absorbed dose distribution. The conical reflection grass was arranged to surround the plastic scintillator, which project to downstream the projection images of the scintillation light. Then, the projection image was reflected to 45 degree direction by flat reflection grass, and was recorded by camcorder. By reconstructing the three‐dimensional dose distribution from the projection image recorded in each frame, we could obtain the four‐dimensional dose distribution. First, we tested the characteristic according to the amount of emitted light. Then we compared of the light profile and the dose profile calculated with the radiotherapy treatment planning system.Results:The dose dependency of the amount of light showed linearity. The pixel detecting smaller amount of light had high sensitivity than the pixel detecting larger amount of light. However the difference of the sensitivity could be corrected from the amount of light detected in each pixel. Both of the depth light profile through the conical reflection grass and the depth dose profile showed the same attenuation in the region deeper than peak depth. In lateral direction, the difference of the both profiles was shown at outside field and penumbra region. We consider that the difference is occurred due to the scatter of the scintillation light in the plastic scintillator block.Conclusion:It was possible to obtain the amount of light corresponding to the absorbed dose distribution from the prototype detector. Four‐dimensional dose distributions can be reconstructed with high accuracy by the correction of the scattered light.
SU‐E‐CAMPUS‐T‐04: Measurement of Proton Pencil Beam Spot Profile Using Cherenkov Radiation in Two Dimensional Optical Fiber Arrays
Authors: Kim M , Son J , Hwang U , SHIN D , Park J , Lim Y , Lee S , Kim J 
Published: July 2014

Purpose:Proton therapy aims to deliver a high dose in a well‐defined target volume while sparing the healthy surrounding tissues thanks to their inherent depth dose characteristic (Bragg peak). In proton therapy, several techniques can be used to deliver the dose into the target volume. The one that allows the best conformity with the tumor, is called PBS (Pencil Beam Scanning). The measurement of the proton pencil beam spot profile (spot size) and position is very important for the accurate delivery of dose to the target volume with a good conformity.Methods:We have developed a fine segmented detector array to monitor the PBS. A prototype beam monitor using Cherenkov radiation in clear plastic optical fibers (cPOF) has been developed for continuous display of the pencil beam status during the therapeutic proton Pencil Beam Scanning mode operation. The benefit of using Cherenkov radiation is that the optical output is linear to the dose. Pedestal substraction and the gain adjustment between channels are performed. Spot profiles of various pencil beam energies(100 MeV to 226 MeV) are measured. Two dimensional gaussian fit is used to analyze the beam width and the spot center. The results are compared with that of Lynx(Scintillator‐based sensor with CCD camera) and EBT3 Film.Results:The measured gaussian widths using fiber array system changes from 13 to 5 mm for the beam energies from 100 to 226 MeV. The results agree well with Lynx and Film within the systematic error.Conclusion:The results demonstrate good monitoring capability of the system. Not only measuing the spot profile but also monitoring dose map by accumulating each spot measurement is available. The x‐y monitoing system with 128 channel readout will be mounted to the snout for the in‐situ real time monitoring.
SU‐E‐CAMPUS‐T‐05: Preliminary Results On a 2D Dosimetry System Based On the Optically Stimulated Luminescence of Al2O3
Authors: Ahmed M , Eller S , Schnell E , Ahmad S , Akselrod M , Hanson O , Yukihara E 
Published: July 2014

Purpose:To develop a precise 2D dose mapping technique based on the optically stimulated luminescence (OSL) from Al2O3 films for medical applications.Methods:A 2D laser scanning reader was developed using fast F+‐center (lifetime of <7 ns) and slow F‐center (lifetime of 35 ms) OSL emission from newly developed Al2O3 films (Landauer Inc.). An algorithm was developed to correct images for both material and system properties. Since greater contribution of the F??‐center emission in the recorded signal increases the readout efficiency and robustness of image corrections, Al2O3:C,Mg film samples are being investigated in addition to Al2O3:C samples. Preliminary investigations include exposure of the films to a 6 MV photon beam at 10 cm depth in solid water phantom with an SSD of 100 cm, using a 10 cm × 10 cm flat field or a 4 cm × 4 cm field with a 60° wedge filter. Kodak EDR2 radiographic film and EBT2 Gafchromic film were also exposed for comparison.Results:The results indicate that the algorithm is able to correct images and calculate 2D dose. For the wedge field irradiation, the calculated dose at the center of the field was 0.9 Gy for Al2O3:C and 0.87 Gy for Al2O3:C,Mg, whereas, the delivered dose was 0.95 Gy. A good qualitative agreement of the dose profiles was obtained between the OSL films and EDR2 and EBT2 films. Laboratory tests using a beta source suggest that a large dynamic range (10−2−102 Gy) can be achieved using this technique.Conclusion:A 2D dosimetry system and an in‐house image correction algorithm were developed for 2D film dosimetry in medical applications. The system is in the preliminary stage of development, but the data demonstrates the feasibility of this approach. This work was supported by Landauer, Inc.
SU‐E‐CAMPUS‐T‐06: Radiochromic Film Analysis Based On Principal Components
Authors: Wendt R 
Published: July 2014

Purpose:An algorithm to convert the color image of scanned EBT2 radiochromic film [Ashland, Covington KY] into a dose map was developed based upon a principal component analysis. The sensitive layer of the EBT2 film is colored so that the background streaks arising from variations in thickness and scanning imperfections may be distinguished by color from the dose in the exposed film.Methods:Doses of 0, 0.94, 1.9, 3.8, 7.8, 16, 32 and 64 Gy were delivered to radiochromic films by contact with a calibrated Sr‐90/Y‐90 source. They were digitized by a transparency scanner. Optical density images were calculated and analyzed by the method of principal components. The eigenimages of the 0.94 Gy film contained predominantly noise, predominantly background streaking, and background streaking plus the source, respectively, in order from the smallest to the largest eigenvalue. Weighting the second and third eigenimages by −0.574 and 0.819 respectively and summing them plus the constant 0.012 yielded a processed optical density image with negligible background streaking. This same weighted sum was transformed to the red, green and blue space of the scanned images and applied to all of the doses. The curve of processed density in the middle of the source versus applied dose was fit by a twophase association curve. A film was sandwiched between two polystyrene blocks and exposed edge‐on to a different Y‐90 source. This measurement was modeled with the GATE simulation toolkit [Version 6.2, OpenGATE Collaboration], and the on‐axis depth‐dose curves were compared.Results:The transformation defined using the principal component analysis of the 0.94 Gy film minimized streaking in the backgrounds of all of the films. The depth‐dose curves from the film measurement and simulation are indistinguishable.Conclusion:This algorithm accurately converts EBT2 film images to dose images while reducing noise and minimizing background streaking.Supported by a sponsored research agreement from IsoTherapeutics Group, LLC.
SU‐E‐CAMPUS‐T‐01: Analysis of the Precision of Patient Set‐Up, and Fidelity of the Delivered Dose Distribution in Proton Therapy of Ocular Tumors
Authors: Trofimov A , Carpenter K , Shih HA 
Published: July 2014

Purpose:To quantify daily set‐up variations in fractionated proton therapy of ocular melanomas, and to assess the effect on the fidelity of delivered distribution to the plan.Methods:In a typical five‐fraction course, daily set‐up is achieved by matching the position of fiducial markers in orthogonal radiographs to the images generated by treatment planning program. A patient maintains the required gaze direction voluntarily, without the aid of fixation devices. Confirmation radiographs are acquired to assess intrafractional changes. For this study, daily radiographs were analyzed to determine the daily iso‐center position and apparent gaze direction, which were then transferred to the planning system to calculate the dose delivered in individual fractions, and accumulated dose for the entire course. Dose‐volume metrics were compared between the planned and accumulated distributions for the tumor and organs at risk, for representative cases that varied by location within the ocular globe.Results:The analysis of the first set of cases (3 posterior, 3 transequatorial and 4 anterior tumors) revealed varying dose deviation patterns, depending on the tumor location. For anterior and posterior tumors, the largest dose increases were observed in the lens and ciliary body, while for the equatorial tumors, macula, optic nerve and disk, were most often affected. The iso‐center position error was below 1.3 mm (95%‐confidence interval), and the standard deviation of daily polar and azimuthal gaze set‐up were 1.5 and 3 degrees, respectively.Conclusion:We quantified interfractional and intrafractional set‐up variation, and estimated their effect on the delivered dose for representative cases. Current safety margins are sufficient to maintain the target coverage, however, the dose delivered to critical structures often deviates from the plan. The ongoing analysis will further explore the patterns of dose deviation, and may help to identify particular treatment scenarios which are at a higher risk for such deviations.
SU‐E‐CAMPUS‐T‐02: Can Pre‐Treatment 4DCT‐Based Motion Margins Estimates Be Trusted for Proton Radiotherapy?
Authors: Seco J , Koybasi O , Mishra P , James S St. , Lewis J 
Published: July 2014

Purpose:Radiotherapy motion margins are generated using pre‐treatment 4DCT data. The purpose of this study is to assess if pre‐treatment 4DCT is sufficient in proton therapy to provide accurate estimate of motion margins. A dosimetric assessment is performed comparing pre‐treatment margins with daily‐customized margins.Methods:Gold fiducial markers implanted in lung tumors of patients were used to track the tumor. A spherical tumor of diameter 20 mm is inserted into a realistic digital respiratory phantom, where the tumor motion is based on real patient lung tumor trajectories recorded over multiple days. Using “Day 1” patient data, 100 ITVs were generated with 1 s interval between consecutive scan start times. Each ITV was made up by the union of 10 tumor positions obtained from 6 s scan time. Two ITV volumes were chosen for treatment planning: ITVmean‐σ and ITVmean+σ. The delivered dose was computed on i) 10 phases forming the planning ITV (“10‐phase” – simulating dose calculation based on 4DCT) and ii) 50 phantoms produced from 100 s of data from any other day with tumor positions sampled every 2 s (“dynamic” – simulating the dose that would actually be delivered).Results:For similar breathing patterns between “Day 1” and any other “Day N(>1)”, the 95% volume coverage (D95) for “dynamic” case was 8.13% lower than the “10‐phase” case for ITVmean+σ. For breathing patterns that were very different between “Day 1” and any other “Day N(>1)”, this difference was as high as 24.5% for ITVmean‐σ.Conclusion:Proton treatment planning based on pre‐treatment 4DCT can lead to under‐dosage of the tumor and over‐dosage of the surrounding tissues, because of inadequate estimate of the range of motion of the tumor. This is due to the shift of the Bragg peak compared to photon therapy in which the tumor is surrounded by an electron bath.
SU‐E‐CAMPUS‐T‐03: Development and Implementation of An Anthropomorphic Pediatric Spine Phantom for the Assessment of Craniospinal Irradiation Procedures in Proton Therapy
Authors: Lewis D , Summers P , Followill D , Sahoo N , Mahajan A , Stingo F , Kry S 
Published: July 2014

Purpose:To design an anthropomorphic pediatric spine phantom for use in the evaluation of proton therapy facilities for clinical trial participation by the Imaging and Radiation Oncology Core (IROC) Houston QA Center (formerly RPC).Methods:This phantom was designed to perform an end‐to‐end audit of the proton spine treatment process, including simulation, dose calculation by the treatment planning system (TPS), and proton treatment delivery. The design incorporated materials simulating the thoracic spinal column of a pediatric patient, along with two thermoluminescent dosimeter (TLD)‐100 capsules and radiochromic film embedded in the phantom for dose evaluation. Fourteen potential materials were tested to determine relative proton stopping power (RSP) and Hounsfield unit (HU) values. Each material was CT scanned at 120kVp, and the RSP was obtained from depth ionization scans using the Zebra multilayer ion chamber (MLIC) at two energies: 160 MeV and 250 MeV. To determine tissue equivalency, the measured RSP for each material was compared to the RSP calculated by the Eclipse TPS for a given HU.Results:The materials selected as bone, tissue, and cartilage substitutes were Techron HPV Bearing Grade (Boedeker Plastics, Inc.), solid water, and blue water, respectively. The RSP values did not differ by more than 1.8% between the two energies. The measured RSP for each selected material agreed with the RSP calculated by the Eclipse TPS within 1.2%.Conclusion:An anthropomorphic pediatric proton spine phantom was designed to evaluate proton therapy delivery. The inclusion of multiple tissue substitutes increases heterogeneity and the level of difficulty for institutions to successfully treat the phantom. The following attributes will be evaluated: absolute dose agreement, distal range, field width, junction match and right/left dose profile alignment. The phantom will be tested at several institutions using a 5% dose agreement criterion, and a 5%/3mm gamma analysis criterion for the film planes.Work supported by grants CA10953, CA059267, and CA81647 (NCI, DHHS).
SU‐E‐CAMPUS‐T‐04: Statistical Process Control for Patient‐Specific QA in Proton Beams
Authors: LAH J , SHIN D , Kim G 
Published: July 2014

Purpose:To evaluate and improve the reliability of proton QA process, to provide an optimal customized level using the statistical process control (SPC) methodology. The aim is then to suggest the suitable guidelines for patient‐specific QA process.Methods:We investigated the constancy of the dose output and range to see whether it was within the tolerance level of daily QA process. This study analyzed the difference between the measured and calculated ranges along the central axis to suggest the suitable guidelines for patient‐specific QA in proton beam by using process capability indices. In this study, patient QA plans were classified into 6 treatment sites: head & neck (41 cases), spinal cord (29 cases), lung (28 cases), liver (30 cases), pancreas (26 cases), and prostate (24 cases).Results:The deviations for the dose output and range of daily QA process were ±0.84% and ±019%, respectively. Our results show that the patient‐specific range measurements are capable at a specification limit of ±2% in all treatment sites except spinal cord cases. In spinal cord cases, comparison of process capability indices (Cp, Cpm, Cpk ≥1, but Cpmk ≤1) indicated that the process is capable, but not centered, the process mean deviates from its target value. The UCL (upper control limit), CL (center line) and LCL (lower control limit) for spinal cord cases were 1.37%, −0.27% and −1.89%, respectively. On the other hands, the range differences in prostate cases were good agreement between calculated and measured values. The UCL, CL and LCL for prostate cases were 0.57%, −0.11% and −0.78%, respectively.Conclusion:SPC methodology has potential as a useful tool to customize an optimal tolerance levels and to suggest the suitable guidelines for patient‐specific QA in clinical proton beam.
SU‐E‐CAMPUS‐T‐05: Validation of High‐Resolution 3D Patient QA for Proton Pencil Beam Scanning and IMPT by Polymer Gel Dosimetry
Authors: Cardin A , Avery S , Maryanski M , Ding X , Kassaee A , Lin L 
Published: July 2014

Purpose:Validation of high‐resolution 3D patient QA for proton pencil beam scanning and IMPT by polymer gel dosimetry.Methods:Four BANG3Pro polymer gel dosimeters (manufactured by MGS Research Inc, Madison, CT) were used for patient QA at the Robert's Proton Therapy Center (RPTC, Philadelphia, PA). All dosimeters were sealed in identical thin‐wall Pyrex glass spheres. Each dosimeter contained a set of markers for 3D registration purposes. The dosimeters were mounted in a consistent and reproducible manner using a custom build holder. Two proton pencil beam scanning plans were designed using Varian Eclipse™ treatment planning system: 1) A two‐field intensity modulated proton therapy (IMPT) plan and 2) one single field uniform dose (SFUD) plan. The IMPT fields were evaluated as a composite plan and individual fields, the SFUD plan was delivered as a single field plan.Laser CT scanning was performed using the manufacturer's OCTOPUS‐IQ axial transmission laser CT scanner using a 1 mm slice thickness. 3D registration, analysis, and OD/cm to absorbed dose calibrations were perfomed using DICOM RT‐Dose and CT files, and software developed by the manufacturer. 3D delta index, a metric equivalent to the gamma tool, was used for dose comparison.Results:Very good agreement with single IMPT fields and with SFUD was obtained. Composite IMPT fields had a less satisfactory agreement. The single fields had 3D delta index passing rates (3% dose difference, 3 mm DTA) of 98.98% and 94.91%. The composite 3D delta index passing rate was 80.80%. The SFUD passing rate was 93.77%. Required shifts of the dose distributions were less than 4 mm.Conclusion:A formulation of the BANG3Pro polymer gel dosimeter, suitable for 3D QA of proton patient plans is established and validated. Likewise, the mailed QA analysis service provided by the manufacturer is a practical option when required resources are unavailable.We fully disclose that the subject of this research regards a production of MGS Research, Inc.
SU‐E‐CAMPUS‐T‐06: Initial Experience of Patient‐Specific QA Using a Pencil Beam Scanning Proton Therapy System
Authors: Piskulich F , Zhang Y , Perles L , Mascia A , Lepage R , Giebeler A , Dong L 
Published: July 2014

Purpose:To illustrate patient QA results for the first 10 patients treated at Scripps Proton Center by comparing point dose measurement using an ion chamber and in‐house developed secondary MU program, and the measurement of 2D dose distribution using an ion chamber array.Methods:At the time of writing, 10 patient plans were approved for treatment using Varian ProBeam pencil beam scanning system and Eclipse treatment planning software. We used the IBA CC04 0.04 cm3 ion chamber and PTW Unidos E electrometer for point dose measurement in a small water tank (Sun Nuclear 1D scanner). We developed independent MU check software based on measured pencil beam dose profiles for various energies. We used PTW Octavius 729 XDR array to evaluate 2D planar dose distribution. The 3D gamma at 3%/3 mm local dose was used to compare a 3D calculated dose plan with a 2D measured dose distribution using PTW Verisoft software. All fields were exported to a verification phantom plan and delivered at 0 degrees for simplicity.Results:Comparisons between the CC04 ion chamber measurement and calculated dose agree well within 1%. The PTW Octavius 729 XDR array exhibited some dose rate dependence in high dose rate pencil beam delivery. Nevertheless, the results, used as a relative measurement, passed the gamma criteria of 3%/3mm for greater than 90% of area in all patient fields. Visual inspection showed good agreement between ion chamber dose profile and the calculated plan. The in‐house secondary check for MU agreed very well with the plan dose and measurement. The results will be updated with more patients treated.Conclusion:The initial patient specific QA results are encouraging for a new pencil beam scanning only proton therapy system.
SU‐E‐CAMPUS‐I‐01: Nanometric Organic Photovoltaic Thin Film X‐Ray Detectors for Clinical KVp Beams
Authors: Elshahat Bassem , Filipyev Ilya , Shrestha Suman , Hesser Jurgen , Gill Hardeep , Kumar Jayant , Karellas Andrew , Zygmanski Piotr , Sajo Erno 
Published: July 2014

Purpose:To fabricate and test nanometric organic photovoltaic (OPV) cells made of various active‐layer/electrode thicknesses and sizes; to determine the optimal material combinations and geometries suitable for dose measurements in clinical kilovoltage x‐ray beams.Methods:The OPV consisted of P3HT:PCBM photoactive materials sandwiched between aluminum and Indium Tin Oxide (ITO) electrodes. Direct conversion of xrays in the active layer composed of donor and acceptor semiconducting organic materials generated signal in photovoltaic mode (without external voltage bias). OPV cells were fabricated with different active layer thicknesses (150, 270, 370 nm) and electrode areas (0.4, 0.7, 0.9, 1.4, 2.6 cm2). A series of experiments were preformed in the energy range of 60–150 kVp. The net current per unit area (nA/cm2) was measured using 200 mAs time‐integrated beam current.Results:The net OPV current as function of beam energy (kVp) was proportional to ∼E0,4 5 when adjusted for beam output. The best combination of parameters for these cells was 270 nm active layer thicknesses for 0.7 cm2 electrode area. The measured current ranged from 0.69 to 2.43 nA/cm2 as a function of x‐ray energy between 60 and 150 kVp, corresponding to 0.09 – 0.06 nA/cm2/mGy, respectively, when adjusted for the beam output.Conclusion:The experiments indicate that OPV detectors possessing 270 nm active layer and 0.7 cm2 Al electrode areas have sensitivity by a factor of 2.5 greater than commercial aSi thin film PV. Because OPV can be made flexible and they do not require highvoltage bias supply, they open the possibility for using as in‐vivo detectors in radiation safety in x‐ray imaging beams.