bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐763: Towards the Mechanical Doping of Plastic Scintillators
Authors: Nusrat H , Pang G , Au P , Sarfehnia A 
Published: June 2015

Purpose:The doping of plastic scintillators with high‐Z elements changes the radiation interaction cross section of the medium and therefore changes the intrinsic response of the detector. The selection of doped plastic scintillators available commercially is limited. This research aims to develop a novel methodology for the mechanical doping of plastic scintillating materials. The ultimate goal of this project is to use doped scintillators of varying intrinsic behavior to unfold the LET (energy) spectrum of any radiation beam.Methods:Commercially available BC408 plastic scintillator was obtained and crushed into uniform powder (using ball mill). Two separate materials were tested for light output signal: uncrushed scintillator and scintillating powder bound by glue. Commercially available U301 UV‐hardening glue was used. Scintillation response was measured by creating a thin housing of black acrylic that allowed light from each scintillator to be guided to an optical fiber via a taper. The optical fiber was connected to a PMT; signal was measured using an electrometer. Tests were conducted to determine if crushing+bonding distorted linearity and energy dependence of detector response. Linearity was tested for by irradiating (uncrushed and crushed+glued) for varying durations ensuring signal scaled accordingly; this was done using 300kV x‐rays and 6MeV electrons. The effect on energy dependence was examined by obtaining a signal ratio (100kV vs. 300kV; 6MeV vs. 18MeV) for both uncrushed and crushed+glued scintillating material.Results:Crushing and binding with U301 glue did not have an effect on linearity. Energy dependence was changed by 20.3%; crushing+bonding decreased the sensitivity at low energy radiation.Conclusion:This work indicates that crushing and binding of plastic scintillating material does not change the linearity of its response to radiation but does have an effect on the energy dependence. Future work involves addition of high‐Z dopants (W, Mo, Pb) and characterization of the detector response.
SU‐E‐T‐767: Treatment Planning Study of Prostate Cancer by CyberKnife with Respect to the Urethral Dose
Authors: Mizuno H , Mizuno H , Sumida I , Otani Y , Yagi M , Takashina M , Suzuki O , Yoshioka Y , Koizumi M , Ogawa K 
Published: June 2015

Purpose:Hypo‐fractionated stereotactic body radiation therapy (SBRT) with intensity modulated radiation therapy (IMRT) is nowadays one of the treatment strategies for prostate cancer. There are few reports on planning study of prostate cancer by CyberKnife with respect to the urethral dose because of the invisibility in CT. We have investigated a planning method using fixed collimators with considering dose homogeneity, conformity and urethral dose.Methods:Radiotherapy treatment planning of prostate cancer were under a clinical trial approved by the institutional review board. The prescription dose of 35 Gy were delivered to the PTV in five fractions with the urethral catheter. Urethra position was identified by pretreatment CT and catheter, which was inserted before treatment planning CT and released after the treatment. All plans agreed to the criteria as shown in table 1, and the following constraints were recommended as well: the prescribed iso‐dose line should be from 70% to 90%; the total MU should be below 50,000 MU; the minimum MU per beam should be larger than 15 MU; the estimated delivery time (excluding patient setup time) by Multiplan with image time interval of 60 s should be less than 35 min. Collimator size and position were decided as shown in figure 1. Fixed collimator of 15 mm was positioned around urethra and PTV for avoiding high dose of urethra and achieving conformity, and fixed collimator of 30 or 40 were positioned around PTV for achieving dose homogeneity.Results:With this method, all constraints were achieved. (Table 1, Figure 2) Max dose of urethra was ranging from 103.9% to 114.2%, because urethra position was identified by pretreatment CT and urethral catheter.Conclusion:Hypo‐fractionated SBRT with IMRT utilizing urethral catheter could be a promising new treatment option for prostate cancer.This work was supported by JSPS Core‐to‐Core program Number 23003.
SU‐E‐T‐772: Uncertainties in Treatment Planning for IROC‐Houston Proton Phantom QA Program Due to Variable CT Technique and Proton Energy
Authors: McInnis M , Taylor P , Poenisch F , Court L , Guindani M , Followill D 
Published: June 2015

Purpose:To understand the uncertainties in proton therapy treatment planning for the IROC‐ Houston proton phantom QA program due to variations in CT technique and proton energy.Methods:A CT phantom used by IROC‐H during therapy site visits was scanned using three CT techniques (80, 120, 140kV) with a CT scanner used for proton therapy simulations and irradiated with a passively scattered beam at three energies (140, 200, 250 MeV) to measure, respectively, HU and Relative Linear Stopping Power (RLSP) in order to create HU to RLSP calibration curves for comparison with reference curves used by current proton treatment planning systems. The phantom has proton equivalent materials with a wide variety of HU and RLSPs to allow for the creation of a calibration curve for common tissue equivalent materials. Treatment plans were created for a lung phantom using the various CT technique/ beam energy calibration curves to determine the differences in the dose distributions by performing a gamma analysis.Results:Comparison of the calibration curves created using the phantom materials showed a maximum difference of 12% for a given material between the custom curve and the reference curve currently used by the treatment planning system. The highest differences were a Result of using an 80 kV CT technique and a 250 MeV high proton energy. A comparison of the completed treatment plans will be presented.Conclusion:These results indicate the possibility of differences in proton HU to RLSP calibration curves caused by varying CT technique and proton energy that could manifest as differences in planned and delivered dose distributions, particularly at high proton energies and low kV CT techniques. These differences could Result in discrepancies not accounted for by IROC‐Houston and could possibly affect proton institutions’ pass rate when irradiating the proton phantoms.
SU‐E‐T‐778: Use of the 2D MatriXX Detector for Measuring Scanned Ion Beam Parameters
Authors: Anvar M Varasteh , Giordanengo S , Donetti M , Marchetto F , Ciocca M , Panizza D , Monaco V , Sacchi R , Vignati A , Guarachi L Fanola , Cirio R 
Published: June 2015

Purpose:The quality assurance (QA) procedure has to check the most relevant beam parameters to ensure the delivery of the correct dose to patients. Film dosimetry, which is commonly used for scanned ion beam QA, does not provide immediate results. The purpose of this work is to answer whether, for scanned ion beam therapy, film dosimetry can be replaced with the 2D MatriXX detector as a real‐time tool.Methods:MatriXX, equipped with 32×32 parallel plate ion‐chambers, is a commercial device intended for pre‐treatment verification of conventional radiation therapy.The MatriXX, placed at the isocenter, and GAFCHROMIC films, positioned on the MatriXX entrance, were exposed to 131.44 MeV proton and 221.45 MeV/u Carbon‐ion beams.The OmniPro‐I'mRT software, applied for the data taking of MatriXX, gives the possibility of acquiring consecutive snapshots. Using the NI LabVIEW, the data from snapshots were logged as text files for further analysis. Radiochromic films were scanned with EPSON scanner and analyzed using software programs developed in‐house for comparative purposes.Results:The field dose uniformity, flatness, beam position and beam width were investigated. The field flatness for the region covering 6×6 cm2 square field was found to be better than 2%. The relative standard deviations, expected to be constant over 2×2, 4×4 and 6×6 pixels from MatriXX measurement gives a uniformity of 1.5% in good agreement with the film results.The beam center position is determined with a resolution better than 200 µm for Carbon and less than 100 µm for proton beam.The FWHM determination for a beam wider than 10 mm is satisfactory, whilst for smaller beams the determination is uncertain.Conclusion:Precise beam position and fast 2D dose distribution can be determined in real‐time using MatriXX detector. The results show that MatriXX is quick and accurate enough to be used in charged‐particle therapy QA.
SU‐E‐T‐781: Using An Electronic Portal Imaging Device (EPID) for Correlating Linac Photon Beam Energies
Authors: Yaddanapudi S , Cai B , Sun B , Noel C , Goddu S , Mutic S 
Published: June 2015

Purpose:Electronic portal imaging devices (EPIDs) have proven to be useful for measuring several parameters of interest in linear accelerator (linac) quality assurance (QA). The purpose of this project was to evaluate the feasibility of using EPIDs for determining linac photon beam energies.Methods:Two non‐clinical Varian TrueBeam linacs (Varian Medical Systems, Palo Alto, CA) with 6MV and 10MV photon beams were used to perform the measurements. The linacs were equipped with an amorphous silicon based EPIDs (aSi1000) that were used for the measurements. We compared the use of flatness versus percent depth dose (PDD) for predicting changes in linac photon beam energy. PDD was measured in 1D water tank (Sun Nuclear Corporation, Melbourne FL) and the profiles were measured using 2D ion‐chamber array (IC‐Profiler, Sun Nuclear) and the EPID. Energy changes were accomplished by varying the bending magnet current (BMC). The evaluated energies conformed with the AAPM TG142 tolerance of ±1% change in PDD.Results:BMC changes correlating with a ±1% change in PDD corresponded with a change in flatness of ∼1% to 2% from baseline values on the EPID. IC Profiler flatness values had the same correlation. We observed a similar trend for the 10MV beam energy changes. Our measurements indicated a strong correlation between changes in linac photon beam energy and changes in flatness. For all machines and energies, beam energy changes produced change in the uniformity (AAPM TG‐142), varying from ∼1% to 2.5%.Conclusions:EPID image analysis of beam profiles can be used to determine linac photon beam energy changes. Flatness‐based metrics or uniformity as defined by AAPM TG‐142 were found to be more sensitive to linac photon beam energy changes than PDD.Research funding provided by Varian Medical Systems. Dr. Sasa Mutic receives compensation for providing patient safety training services from Varian Medical Systems, the sponsor of this study.
SU‐E‐T‐783: Using Matrixx to Determine Transit Dose Contribution Over Clinically Useful Limits of HDR Source Activity
Authors: Bhagwat M , O'Farrell D , Wagar M , Buzurovic I , Friesen S , Damato A , Devlin P , Cormack R 
Published: June 2015

Purpose:Most HDR brachytherapy treatment planning systems (TPS) use TG‐43 formalism to calculate dose without including transit dose corrections. Historically, measurement of this contribution has required sophisticated apparatus unavailable in most hospitals. We use Matrixx to investigate several scenarios where transit dose contribution may effect a clinical treatment.Methods:Treatment plans were generated using Oncentra Brachy TPS (Version 4.3.0.410, Nucletron ) on a CT scan of a 24‐catheter Freiburg applicator (Nucletron ) laid flat on the MatriXX (IBA) detector. This detector is an array of 1020 parallel plate ion chambers. All 24 catheters were digitized and dwells within a central square region of 5×5cm of the applicator were activated. Each of the active catheters had 6 dwells in increments of 1.0cm. The plans were normalized to 10mm. This places the 100% isodose line at the correct effective point of measurement, which lies half‐way between the parallel plates of the ion chambers. It is also within the clinically relevant treatment depth for superficial applications. A total of 6 plans were delivered for 3 prescription doses, 1Gy, 2Gy and 4Gy using source activities of 2.9Ci and 11.2Ci. The MatriXX array was operated to capture dosimetric snaps every 500ms and yielded an integral dose at the end of treatment.Results:A comparison of integral dose from 2 different source activities shows that the transit dose contribution is larger when the source activity is higher. It is also observed that the relative transit dose contribution decreases as prescription dose increases. This is quantified by the Gamma analysis.Conclusion:We have demonstrated that the Matrixx detector can be used to evaluate the contribution for a HDR source during transit from the HDR afterloader to a dwell location, and between adjacent dwell locations.
SU‐E‐T‐787: Utility of the Two Candidate 192‐Ir and 169‐Yb HDR Sources for Use with a Novel Direction Modulated Brachytherapy Tandem Applicator for Cervical Cancer Treatment
Authors: Safigholi H , Han D , Soliman A , Meigooni A Soleimani , Song W 
Published: June 2015

Purpose:A novel tungsten alloy shielded, MRI‐compatible, direction modulated brachytherapy (DMBT) concept tandem applicator, which enables unprecedented intensity modulation, was used to evaluate treatment plan quality improvement over a conventional tandem. The utility of the 192‐Ir and 169‐Yb HDR sources, for use with the DMBT applicator, was evaluated.Methods:The total diameter of the DMBT tandem applicator is 6.0 mm, which consists of 5.4‐mm diameter tungsten alloy and 0.3 mm thick plastic sheath. The tandem has 6 symmetric peripheral 1.3‐mm diameter grooves for the source to travel. MCNPX v.2.6 was used to simulate the 192‐Ir and 169‐Yb sources inside the DMBT applicator. First, TG‐43 source parameters were evaluated. Second, 3D dose matrix with 1 mm3 resolution were imported into an in‐house‐coded inverse optimization treatment planning program to obtain optimal plans for 19 clinical cases. All plans were compared with the standard tandem and ring plans. Prescription dose was 15.0 Gy. All plans were normalized to receive the same HRCTV D90.Results:Generally, the DMBT tandem (and ring) plans were better than the conventional tandem and ring plans for 192‐Ir and 169‐Yb HDR sources. The mean data of D2cc for bladder, rectum, and sigmoid were 11.65±2.30 Gy, 7.47±3.05 Gy, and 9.84±2.48 Gy for Ir‐192 DMBT tandem, respectively. These data for Yb‐169 were 11.67±2.26 Gy, 7.44±3.02 Gy, and 9.83±2.38 Gy, respectively. The HR‐CTV D98 and V100 were 16.37±1.86 Gy and 97.37 ± 1.92 Gy for Ir‐192 DMBT, respectively. The corresponding values for Yb‐169 were 16.43±1.86 Gy, and 97.51 ± 1.91 Gy. Plans with the 169‐Yb source generally produced more favorable results where V100 increased by 13.65% while D2cc across all OARs reduced by 0.54% compared with the 192‐Ir plans.Conclusion:For the DMBT tandem applicator, 169‐Yb source seems to produce more directional beams resulting in increased intensity modulation capacity, thus resulting in more conformal plans
SU‐E‐T‐790: Validation of 4D Measurement‐Guided Dose Reconstruction (MGDR) with OCTAVIUS 4D System
Authors: Lee V , Blanck O , Leung R , Wong M , Law G , Lee K , Tung S , Chan M 
Published: June 2015

Purpose:To validate the MGDR of OCTAVIUS 4D system (PTW, Freiburg, Germany) for quality assurance (QA) of volumetric‐modulated arc radiotherapy (VMAT).Methods:4D‐MGDR measurements were divided into two parts: 1) square fields from 2×2 to 25×25 cm2 at 0°, 10° and 45° gantry, and 2) 8 VMAT plans (5 nasopharyngeal and 3 prostate) collapsed to gantry 40° in QA mode in Monaco v5.0 (Elekta, CMS, Maryland Heights, MO) were delivered on the OCTAVIUS 4D phantom with the OCTAVIUS 1500 detector plane perpendicular to either the incident beam to obtain the reconstructed dose (OCTA4D) or the 0° gantry axis to obtain the raw doses (OCTA3D) in Verisoft 6.1 (PTW, Freiburg, Germany). Raw measurements of OCTA3D were limited to < 45° gantry to avoid >0.5% variation of detector angular response with respect to 0° gantry as determined previously. Reconstructed OCTA4D and raw OCTA3D doses for all plans were compared at the same detector plane using γ criteria of 2% (local dose)/2mm and 3%/3mm criteria.Results:At gantry 0° and 10°, the γ results for all OCTA4D on detector plane coinciding with OCTA3D were over 90% at 2%/2mm except for the largest field (25×25 cm2 ) showing >88%. For square field at 45° gantry, γ passing rate is > 90% for fields smaller than 15x 15cm2 but < 80% for field size of 20 x20 cm2 upward. For VMAT, γ results showed 94% and 99% passing rate at 2%/2mm and 3%/3mm, respectively.Conclusion:OCTAVIUS 4D system has compromised accuracy in reconstructing dose away from the central beam axis, possibly due to the off‐axis softening correction and errors of the percent depth dose data necessary as input for MGDR. Good results inVMAT delivery suggested that the system is relatively reliable for VMAT with small segments.
SU‐E‐T‐791: Validation of a Determinant Based Photon Transport Solver in Dose Perturbed By Diverse Media
Authors: Kuo H , Tome W , Yaparpalvi R , Garg M , Bodner W , Kalnicki S 
Published: June 2015

Purpose:To validate a determinant based photon transport solver in dose imparted within different transition zone between different medium.Methods:Thickness (.2cm,.5cm, 1cm, 3cm) from various materials (Air ‐ density=0.0012g/cm3, Cork‐0.19g/cm3, Lung‐0.26g/cm3, Bone‐1.85g/cm3, Aluminum (Al)‐2.7g/cm3, Titanium (Ti)‐4.42g/cm3, Iron (Fe)‐8g/cm3) were sandwiched by 10cm solid water. 6MV were used to study the calculation difference between a superposition photon beam model (AAA) and the determinant based Boltzmann photon transport solver (XB) at the upstream (I) and downstream boarder (II) of the medium, within the medium (III), and at far distance downstream away from medium (IV). Calculation was validated with available thickness of Air, Cork, Lung, Al, Ti and Fe. Results are presented as the ratio of the dose at the point with medium perturbation to the same point dose without perturbation.Results:Zone I showed different backscatter enhancement from high‐density materials within the 5mm of the upstream border. AAA showed no backscatter at all, XB showed good agreement beyond 1mm upstream (1.18 vs 1.14, 1.09 vs 1.10, and 1.04 vs 1.05 for Fe, Ti, and Fe, respectively). Zone II showed a re‐buildup after exiting high‐density medium and Air but no build up for density close to water in both of the measurement and XB. AAA yielded the opposite results in Zone II. XB and AAA showed in Zone III very different absorption in high density medium and the Air. XB and measurement had high concordance regarding photon attenuation in Zone IV. AAA showed less agreement especially when the medium was Air or Fe.Conclusion:XB compared well with measurement in regions 1mm away from the interface. Planning using XB should be beneficial for External Beam Planning in situations with large air cavity, very low lung density, compact bone, and any kind of metal implant.
SU‐E‐T‐794: Validation of the MCNPX Monte Carlo Model of the Ocular Beam Line at the Proton Therapy Center Houston
Authors: Titt U , Suzuki K 
Published: June 2015

Purpose:The PTCH is preparing the ocular proton beam nozzle for clinical use. Currently commissioning measurements are being performed using films, diodes and ionization chambers. In parallel, a Monte Carlo model of the beam line was created for integration into the automated Monte Carlo treatment plan computation system, MC2. This work aims to compare Monte Carlo predictions to measured proton doses in order to validate the Monte Carlo model.Methods:A complete model of the double scattering ocular beam line has been created and is capable of simulating proton beams with a comprehensive set of beam modifying devices, including eleven different range modulator wheels. Simulations of doses in water were scored and compare to ion chamber measurements of depth doses, lateral dose profiles extracted from half beam block exposures of films, and diode measurements of lateral penumbrae at various depths.Results:All comparison resulted in an average relative entrance dose difference of less than 3% and peak dose difference of less than 2%. All range differences were smaller than 0.2 mm. The differences in the lateral beam profiles were smaller than 0.2 mm, and the differences in the penumbrae were all smaller than 0.4%.Conclusion:All available data shows excellent agreement of simulations and measurements. More measurements will have to be performed in order to completely and systematically validate the model. Besides simulating and measuring PDDs and lateral profiles of all remaining range modulator wheels, the absolute dosimetry factors in terms of number of source protons per monitor unit have to be determined.
SU‐E‐T‐796: Variation of Surface Photon Energy Spectra On Bone Heterogeneity and Beam Obliquity Between Flattened and Unflattened Beam
Authors: Chow J , Owrangi A , Grigorov G 
Published: June 2015

Purpose:This study investigates the spectra of surface photon energy and energy fluence in the bone heterogeneity and beam obliquity using flattened and unflattened photon beams. The spectra were calculated in a bone and water phantom using Monte Carlo simulation (the EGSnrc code).Methods:Spectra of energy, energy fluence and mean energy of the 6 MV flattened and unflattened photon beams (field size = 10 × 10 cm2) produced by a Varian TrueBEAM linear accelerator were calculated at the surfaces of a bone and water phantom using Monte Carlo simulations. The spectral calculations were repeated with the beam angles turned from 0° to 15°, 30° and 45° in the phantoms.Results:It is found that the unflattened photon beams contained more photons in the low‐energy range of 0 – 2 MeV than the flattened beams with a flattening filter. Compared to the water phantom, both the flattened and unflattened beams had slightly less photons in the energy range < 0.4 MeV when a bone layer of 1 cm is present under the phantom surface. This shows that the presence of the bone decreased the low‐energy photons backscattered to the phantom surface. When the photon beams were rotated from 0° to 45°, the number of photon and mean photon energy increased with the beam angle. This is because both the flattened and unflattened beams became more hardened when the beam angle increased. With the bone heterogeneity, the mean energies of both photon beams increased correspondingly. This is due to the absorption of low‐energy photons by the bone, resulting in more significant beam hardening.Conclusion:The photon spectral information is important in studies on the patient's surface dose enhancement when using unflattened photon beams in radiotherapy.