bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐19A‐11: Retrospective Evaluation of Thermal Coverage by Thermobrachytherapy Seed Arrangements of Clinical LDR Prostate Implants
Authors: Warrell G , Shvydka D , Chen C , Parsai E 
Published: July 2014

Purpose:The superiority of a properly‐administered combination of radiation therapy and hyperthermia over radiation alone in treatment of human cancers has been demonstrated in multiple studies examining radiobiology, local control, and survival. Unfortunately, hyperthermia is not yet a common modality in oncology practice, due in part to the technical difficulty of heating a deep‐seated target volume to sufficient temperature. To address this problem, our group has invented a thermobrachytherapy (TB) seed based on a commonly‐used low dose‐rate permanent brachytherapy seed for implant in solid tumors. Instead of the tungsten radiographic marker of the standard seed, the TB seed contains one of a self‐regulating ferromagnetic alloy. Placement of a patient implanted with such seeds in an oscillating magnetic field generates heat via induction of eddy currents. We present the results of studies of the capability of clinically‐realistic TB seed arrangements to adequately heat defined target volumes.Methods:Seed distributions for several past LDR prostate permanent implant brachytherapy patients were reproduced in the finite element analysis software package COMSOL Multiphysics 4.4, with the difference that TB seeds were modelled, rather than the radiation‐only seeds actually used for their treatments. The implant geometries were mainly of the modified peripheral loading type; a range of prostatic volumes and blood perfusion rates likely to be seen in a clinical setting were examined.Results:According to the simulations, when distributed to optimize radiation dose, TB seeds also produce sufficient heat to provide thermal coverage of the target given proper selection of the magnetic field strength. However, the thermal distributions may be improved by additional use of hyperthermia‐only seeds.Conclusion:A dual‐modality seed intended as an alternative to and using the same implantation apparatus and technique as the standard LDR permanent implant seed has been successfully evaluated for its ability to provide sufficient hyperthermia in clinically‐realistic implants.This work was partially supported by the National Institutes of Health (NIH) STTR Grant No. R41 CA153631‐01A1.
SU‐F‐19A‐12: Split‐Ring Applicator with Interstitial Needle for Improved Volumetric Coverage in HDR Brachytherapy for Cervical Cancer
Authors: Sherertz T , Ellis R , Colussi V , Mislmani M , Traughber B , Herrmann K , Podder T 
Published: July 2014

Purpose:To evaluate volumetric coverage of a Mick Radionuclear titanium Split‐Ring applicator (SRA) with/without interstitial needle compared to an intracavitary Vienna applicator (VA), interstitial‐intracavitary VA, and intracavitary ring and tandem applicator (RTA).Methods:A 57 year‐old female with FIGO stage IIB cervical carcinoma was treated following chemoradiotherapy (45Gy pelvic and 5.4Gy parametrial boost) with highdose‐ rate (HDR) brachytherapy to 30Gy in 5 fractions using a SRA. A single interstitial needle was placed using the Ellis Interstitial Cap for the final three fractions to increase coverage of left‐sided gross residual disease identified on 3T‐MRI. High‐risk (HR) clinical target volume (CTV) and intermediate‐risk (IR) CTV were defined using axial T2‐weighted 2D and 3D MRI sequences (Philips PET/MRI unit). Organs‐at‐risks (OARs) were delineated on CT. Oncentra planning system was used for treatment optimization satisfying GEC‐ESTRO guidelines for target coverage and OAR constraints. Retrospectively, treatment plans (additional 20 plans) were simulated using intracavitary SRA (without needle), intracavitary VA (without needle), interstitial‐intracavitary VA, and intracavitary RTA with this same patient case. Plans were optimized for each fraction to maintain coverage to HR‐CTV.Results:Interstitial‐intracavitary SRA achieved the following combined coverage for external radiation and brachytherapy (EQD2): D90 HR‐CTV =94.6Gy; Bladder_2cc =88.9Gy; Rectum_2cc =65.1Gy; Sigmoid_2cc =48.9Gy; Left vaginal wall (VW) =103Gy, Right VW =99.2Gy. Interstitial‐intracavitary VA was able to achieve identical D90 HR‐CTV =94.6Gy, yet Bladder_2cc =91.9Gy (exceeding GEC‐ESTRO recommendations of 2cc<90Gy) and Left VW =120.8Gy and Right VW =115.5Gy. Neither the SRA nor VA without interstitial needle could cover HR‐CTV adequately without exceeding dose to Bladder_2cc. Conventional RTA was unable to achieve target coverage for the HR‐CTV >80Gy without severely overdosing OARs.Conclusion:The Ellis Interstitial Cap for the SRA offered superior dosimetric coverage as compared to the interstitialintracavitary VA. This represents the first reported use for this devise, and further investigation is warranted.
SU‐F‐BRE‐01: A Rapid Method to Determine An Upper Limit On a Radiation Detector's Correction Factor During the QA of IMRT Plans
Authors: Kamio Y , Bouchard H 
Published: July 2014

Purpose:Discrepancies in the verification of the absorbed dose to water from an IMRT plan using a radiation dosimeter can be wither caused by 1) detector specific nonstandard field correction factors as described by the formalism of Alfonso et al. 2) inaccurate delivery of the DQA plan. The aim of this work is to develop a simple/fast method to determine an upper limit on the contribution of composite field correction factors to these discrepancies.Methods:Indices that characterize the non‐flatness of the symmetrised collapsed delivery (VSC) of IMRT fields over detector‐specific regions of interest were shown to be correlated with IMRT field correction factors. The indices introduced are the uniformity index (UI) and the mean fluctuation index (MF). Each one of these correlation plots have 10 000 fields generated with a stochastic model. A total of eight radiation detectors were investigated in the radial orientation. An upper bound on the correction factors was evaluated by fitting values of high correction factors for a given index value.Results:These fitted curves can be used to compare the performance of radiation dosimeters in composite IMRT fields. Highly water‐equivalent dosimeters like the scintillating detector (Exradin W1) and a generic alanine detector have been found to have corrections under 1% over a broad range of field modulations (0 – 0.12 for MF and 0 – 0.5 for UI). Other detectors have been shown to have corrections of a few percent over this range. Finally, a full Monte Carlo simulations of 18 clinical and nonclinical IMRT field showed good agreement with the fitted curve for the A12 ionization chamber.Conclusion:This work proposes a rapid method to evaluate an upper bound on the contribution of correction factors to discrepancies found in the verification of DQA plans.
SU‐F‐BRE‐02: Characterization of a New Commercial Single Crystal Diamond Detector in Photon, Electron and Proton Beams
Authors: Akino Y , Das I 
Published: July 2014

Purpose:Diamond detectors even with superior characteristics have become obsolete due to poor design, selection of crystal and cost. Recently, microDiamond using synthetic single crystal diamond detector (SCDD) is commercially available which is characterized in various radiation beams in this study.Methods:The characteristics of a commercial SCDD model 60019 (PTW) to a 6‐ and 15‐MV photon beams, 6‐ and 20‐MeV electron beams, and 208 MeV proton beams were investigated and compared to the pre‐characterized detectors: TN31010 (0.125 cm3) and TN30006 (pinpoint) ionization chambers (PTW), EDGE detector (Sun Nuclear Corp), and SFD Stereotactic Dosimetry Diode Detector (IBA). The depth‐dose and profiles data were collected for various field sizes and depths. The dose linearity and dose rate dependency were also evaluated. To evaluate the effects of the preirradiation, the diamond detector which had not been irradiated on the day was set up in the water tank and the response to 100 MU was measured every 20 s. The temperature dependency was tested for the range of 4–60 °C. Angular dependency was evaluated in water phantom by rotating the SCDD.Results:For all radiation types and field sizes, the depth‐dose data of the diamond chamber showed identical curve to those of ionization chambers. The profile of the diamond detector was very similar to those of the Edge and SFD detectors, although the 0.125 cm3 and pinpoint chambers showed averaging effects in the penumbrae region. The temperature dependency was within 0.7% in the range of 4–41°C. A dose of 900 cGy and 1200 cGy were needed to stabilize the chamber to the level within 0.5% and 0.2%, respectively.Conclusion:The type 60019 SCDD detector showed suitable characteristics for depth‐dose and profile measurements for wide range of field sizes. However, at least 1000 cGy of pre‐irradiation is needed for accurate measurements.
SU‐F‐BRE‐03: Consideration of a Track‐Interaction Model for Radiochromic Film Response
Authors: Rosen B , DeWerd L 
Published: July 2014

Purpose:Conventional methods for characterizing the energy response of radiochromic film (RCF) typically involve assessing changes in response when exposed to various beam qualities and use Monte Carlo to determine absorbed dose. These methods represent RCF as a dose integrator of a homogeneous energy deposition volume. Apparent film saturation, nonlinearity, and intrinsic energy dependence are unpredicted with conventional methods. Recent work has shown significant RCF intrinsic energy dependence, which limits its use in absolute dosimetry. This work introduces a track‐interaction model (TIM) for RCF and assesses its ability to predict total energy response.Methods:A TIM based on Katz single‐hit theory was developed to accumulate energy flux along particle tracks within active crystals, represented as (1×1×20)um3 prisms about the Gafchromic™ EBT3 active volume using MCNP5 and Matlab. Energy flux contributed to film response only if near the threshold energy for polymerization in polydiacetylenes (2.5eV/monomer). Energy deposition in excess of maximum efficiency represented crystal saturation and did not contribute to film response. The TIM was applied to RCF exposed in air to various monoenergetic photon beams and Co‐60. Geometric distribution of energy flux was found for each beam quality in a (1×1)mm2 RCF area. RCF response relative to Co‐60 absorbed dose‐to‐water (S_TIM) was determined and compared to published values (S_PUB).Results:TIM successfully predicted that lower energy radiation is less effective at inducing polymerization, though the magnitude of the phenomenon was overpredicted. S_TIM was −29% and +20% for 20 and 40 keV, respectively. This agreed qualitatively with S_PUB of −27% and +16%. TIM‐generated sensitometric curves contained the non‐linearity and saturation apparent in RCF.Conclusion:This work indicates the possibility for TIMs to predict changes in RCF response to various energies. Future work will refine TIM by considering size distributions of active elements, other RCF formulations, and response in complex treatment fields.Acknowledgements: The authors wish to thank Dr. Christopher Soares at NIST (Gaithersburg, MD) for performing film measurements and Dr. David Lewis of Ashland, Inc. (Wayne, NJ) for making the EBT3 film available to us.
SU‐F‐BRE‐04: Construction of 3D Printed Patient Specific Phantoms for Dosimetric Verification Measurements
Authors: Ehler E , Higgins P , Dusenbery K 
Published: July 2014

Purpose:To validate a method to create per patient phantoms for dosimetric verification measurements.Methods:Using a RANDO phantom as a substitute for an actual patient, a model of the external features of the head and neck region of the phantom was created. A phantom was used instead of a human for two reasons: to allow for dosimetric measurements that would not be possible in‐vivo and to avoid patient privacy issues. Using acrylonitrile butadiene styrene thermoplastic as the building material, a hollow replica was created using the 3D printer filled with a custom tissue equivalent mixture of paraffin wax, magnesium oxide, and calcium carbonate. A traditional parallel‐opposed head and neck plan was constructed. Measurements were performed with thermoluminescent dosimeters in both the RANDO phantom and in the 3D printed phantom. Calculated and measured dose was compared at 17 points phantoms including regions in high and low dose regions and at the field edges. On‐board cone beam CT was used to localize both phantoms within 1mm and 1° prior to radiation.Results:The maximum difference in calculated dose between phantoms was 1.8% of the planned dose (180 cGy). The mean difference between calculated and measured dose in the anthropomorphic phantom and the 3D printed phantom was 1.9% ± 2.8% and −0.1% ± 4.9%, respectively. The difference between measured and calculated dose was determined in the RANDO and 3D printed phantoms. The differences between measured and calculated dose in each respective phantom was within 2% for 12 of 17 points. The overlap of the RANDO and 3D printed phantom was 0.956 (Jaccard Index).Conclusion:A custom phantom was created using a 3D printer. Dosimetric calculations and measurements showed good agreement between the dose in the RANDO phantom (patient substitute) and the 3D printed phantom.
SU‐F‐BRE‐05: Development and Evaluation of a Real‐Time Robotic 6D Quality Assurance Phantom
Authors: Belcher AH , Liu X , Grelewicz Z , Wiersma RD 
Published: July 2014

Purpose:A 6 degree‐of‐freedom robotic phantom capable of reproducing dynamic tumor motion in 6D was designed to more effectively match solid tumor movements throughout pre‐treatment scanning and radiation therapy. With the abundance of optical and x‐ray 6D real‐time tumor tracking methodologies clinically available, and the substantial dosimetric consequences of failing to consider tumor rotation as well as translation, this work presents the development and evaluation of a 6D instrument with the facility to improve quality assurance.Methods:An in‐house designed and built 6D robotic motion phantom was constructed following the so‐called Stewart‐Gough parallel kinematics platform archetype. The device was then controlled using an inverse kinematics formulation, and precise movements in all six degrees of freedom (X, Y, Z, pitch, roll, and yaw) as well as previously obtained cranial motion, were effectively executed. The robotic phantom movements were verified using a 15 fps 6D infrared marker tracking system (Polaris, NDI), and quantitatively compared to the input trajectory. Thus, the accuracy and repeatability of 6D motion was investigated and the phantom performance was characterized.Results:Evaluation of the 6D platform demonstrated translational RMSE values of 0.196 mm, 0.260 mm, and 0.101 mm over 20 mm in X and Y and 10 mm in Z, respectively, and rotational RMSE values of 0.068 degrees, 0.0611 degrees, and 0.095 degrees over 10 degrees of pitch, roll, and yaw, respectively. The robotic stage also effectively performed controlled 6D motions, as well as reproduced cranial trajectories over 15 minutes, with a maximal RMSE of 0.044 mm translationally and 0.036 degrees rotationally.Conclusion:This 6D robotic phantom has proven to be accurate under clinical standards and capable of reproducing tumor motion in 6D. Consequently, such a robotics device has the potential to serve as a more effective system for IGRT QA that involves both translational and rotational dimensions.Research was partially funded by NIH Grant T32 EB002103‐21 from NIBIB. Contents are solely the responsibility of the authors and do not necessarily represent the official views of the NIBIB or NIH.
SU‐F‐BRE‐06: Evaluation of Patient CT Dose Reconstruction From 3D Diode Array Measurements Using Anthropomorphic Phantoms
Authors: Huang M , Faught A , Benhabib S , Cardan R , Brezovich I , Followill D , Popple R 
Published: July 2014

Purpose:To compare 3D reconstructed dose of IMRT plans from 3D diode array measurements with measurements in anthropomorphic phantoms.Methods:Six IMRT plans were created for the IROC Houston (RPC) head and neck (H&N) and lung phantoms following IROC Houston planning protocols. The plans included flattened and unflattened beam energies ranging from 6 MV to 15 MV and both static and dynamic MLC tecH&Niques. Each plan was delivered three times to the respective anthropomorphic phantom, each of which contained thermoluminescent dosimeters (TLDs) and radiochromic films (RCFs). The plans were also delivered to a Delta4 diode array (Scandidos, Uppsala, Sweden). Irradiations were done using a TrueBeam STx (Varian Medical Systems, Palo Alto, CA). The dose in the patient was calculated by the Delta4 software, which used the diode measurements to estimate incident energy fluence and a kernel‐based pencil beam algorithm to calculate dose. The 3D dose results were compared with the TLD and RCF measurements.Results:In the lung, the average difference between TLDs and Delta4 calculations was 5% (range 2%–7%). For the H&N, the average differences were 2.4% (range 0%–4.5%) and 1.1% (range 0%–2%) for the high‐ and low‐dose targets, respectively, and 12% (range 10%‐13%) for the organ‐at‐risk simulating the spinal cord. For the RCF and criteria of 7%/4mm, 5%/3mm, and 3%/3mm, the average gamma‐index pass rates were 95.4%, 85.7%, and 76.1%, respectively for the H&N and 76.2%, 57.8%, and 49.5% for the lung. The pass‐rate in the lung decreased with increasing beam energy, as expected for a pencil beam algorithm.Conclusion:The H&N phantom dose reconstruction met the IROC Houston acceptance criteria for clinical trials; however, the lung phantom dose did not, most likely due to the inaccuracy of the pencil beam algorithm in the presence of low‐density inhomogeneities.Work supported by PHS grant CA10953 and CA81647 (NCI, DHHS).
SU‐F‐BRE‐07: Experimental Validation of a Lung SBRT Technique Using a Novel, True Volumetric Plenoptic‐Plastic‐Scintillator Detector
Authors: Goulet M , Rilling M , Gingras L , Beddar S , Beaulieu L , Archambault L 
Published: July 2014

Purpose:Lung SBRT is being used by an increasing number of clinics, including our center which recently treated its first patient. In order to validate this technique, the 3D dose distribution of the SBRT plan was measured using a previously developed 3D detector based on plenoptic camera and plastic scintillator technology. The excellent agreement between the detector measurement and the expected dose from the treatment planning system Pinnacle3 shows great promise and amply justify the development of the technique.Methods:The SBRT treatment comprised 8 non‐coplanar 6MV photon fields with a mean field size of 12 cm2 at isocentre and a total prescription dose of 12Gy per fraction for a total of 48Gy. The 3D detector was composed of a 10×10×10 cm2 EJ‐260 water‐equivalent plastic scintillator embedded inside a truncated cylindrical acrylic phantom of 10cm radius. The scintillation light was recorded using a static R5 light‐field camera and the 3D dose was reconstructed at a 2mm resolution in all 3 dimensions using an iterative backprojection algorithm.Results:The whole 3D dose distribution was recorded at a rate of one acquisition per second. The mean absolute dose difference between the detector and Pinnacle3 was 1.3% over the region with more than 10% of the maximum dose. 3D gamma tests performed over the same region yield passing rates of 98.8% and 96.6% with criteria of 3%/1mm and 2%/1mm, respectively.Conclusion:Experimental results showed that our beam modeling and treatment planning system calculation was adequate for the safe administration of small field/high dose techniques such as SBRT. Moreover, because of the real‐time capability of the detector, further validation of small field rotational, dynamic or gated technique can be monitored or verified by this system.
SU‐F‐BRE‐08: Feasibility of 3D Printed Patient Specific Phantoms for IMRT/IGRT QA
Authors: Ehler E , Higgins P , Dusenbery K 
Published: July 2014

Purpose:Test the feasibility of 3D printed, per‐patient phantoms for IMRT QA to analyze the treatment delivery quality within the patient geometry.Methods:Using the head and neck region of an anthropomorphic phantom as a substitute for an actual patient, a soft‐tissue equivalent model was constructed with the use of a 3D printer. A nine‐field IMRT plan was constructed and dose verification measurements were performed for the 3D printed phantom. During the delivery of the IMRT QA on to the 3D printed phantom, the same patient positioning indexing system was used on the phantom and image guidance (cone beam CT) was used to localize the phantom, serving as a test of the IGRT system as well. The 3D printed phantom was designed to accommodate four radiochromic film planes (two axial, one coronal and one sagittal) and an ionization chamber measurement. As a frame of comparison, the IMRT QA was also performed on traditional phantoms. Dosimetric tolerance levels such as 3mm / 3% Gamma Index as well as 3% and 5% dose difference were considered. All detector systems were calibrated against a NIST traceable ionization chamber.Results:Comparison of results 3D printed patient phantom with the standard IMRT QA systems showed similar passing rates for the 3D printed phantom and the standard phantoms. However, the locations of the failing regions did not necessarily correlate. The 3D printed phantom was localized within 1 mm and 1° using on‐board cone beam CT.Conclusion:A custom phantom was created using a 3D printer. It was determined that the use of patient specific phantoms to perform dosimetric verification and estimate the dose in the patient is feasible. In addition, end‐to‐end testing on a per‐patient basis was possible with the 3D printed phantom. Further refinement of the phantom construction process is needed for routine clinical use.
SU‐F‐BRE‐09: Linac Isocenter Quality Assurance: A Stereotactic Approach
Authors: McCabe B , Li J 
Published: July 2014

Purpose:A quantitative method was designed to independently determine the couch/collimator/gantry isocenters, as well as the overall LINAC mechanical isocenter in 3D.Methods:Performed on both a Varian TrueBeam™ STx and Trilogy with the gold standard front pointer positioned at 100 cm SAD, and a Radionics XKnife™ (RX) attached to the couch. At gantry and couch 0°, the RX laser alignment attachment (RXLAA) was centered to the front pointer using the micrometers (0.1‐mm precision) on the RX. The 3D coordinates of the micrometers were recorded. The collimator was rotated to 90° and 270°. At each collimator rotation, the RXLAA was re‐centered to the front pointer and the micrometer coordinates recorded. At collimator and gantry 0°, the process was repeated for couch angles 0°/90°/270°. Finally, at collimator and couch 0°, the steps were repeated for gantry rotations 0°/90°/180°/270°. The centers/radii of the smallest bounding spheres for the collimator, couch and gantry walkout were calculated (using MatLab™). The smallest bounding sphere containing the collimator, couch and gantry walkout spheres was then calculated. The center of this all‐encompassing sphere is the overall mechanical isocenter of the LINAC. This position was dialed in on the RX. LINAC mechanical and radiation isocenter coincidence was determined by performing Winston‐ Lutz test at four cardinal gantry angles.Results:TrueBeam and Trilogy mechanical isocenters had overall walkout radii of 0.8 mm and 1.5 mm, respectively. For the TrueBeam and Trilogy 6‐MV beams, the radii of radiation isocenter were 0.3 mm and 0.4 mm, respectively, with distances between LINAC mechanical and radiation isocenters of 0.5 mm and 0.9 mm, respectively.Conclusion:This efficient and simple method allows for an independent and reliable quantitative assessment of LINAC isocenter in 3D with equipment typically available in a radiation oncology clinic. It can easily be performed for LINAC commissioning and annual QA.