bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐FF‐J‐151: Fabrication and Testing of An Agar‐Based Heat‐Sensitive Gel for Thermal Dosimetry
Authors: Siddiqi A , Cho S 
Published: April 2010

Purpose: To develop a novel heat‐sensitive gel made of non‐toxic materials that can be used to measure heat resulting from illumination of gold nanoshells/nanorods with near‐infrared (NIR) 808 nm laser. Method and Materials: The heat‐sensitive gel is made by mixing 1.5 weight percent agar in distilled water and the solution is allowed to mix completely while heating it to 90 °C. Once the agar has completely melted and the solution becomes clear, it is allowed to cool to 50 °C, when 20–30 weight percent bovine serum albumin (BSA) is added to the agar mixture. The gel can be poured into any container or mold and allowed to solidify to become various shapes of phantoms. BSA is a heat sensitive protein that will undergo denaturing and result in an optical density change at the areas where temperature exceeds 70 °C. The phantom made of this gel can contain a small cavity where gold nanoshells and nanorods will be concentrated to simulate the tumor. The phantom can be read with T2 weighted magnetic resonance imaging (MRI) for quantification and visualization of heat damage around the cavity due to NIR laser illumination. Results: The agar based gel has shown to be heat‐sensitive and T2 weighted MRI imaging can be used to visualize the permanent heat damage. The average T2 value corresponding to the damaged areas was 90.2 ms compared to 78.9 ms to non‐damaged sites. Conclusion: The agar based heat‐sensitive gel has the thermal stability to withstand relatively high temperatures. It also can be made easily for the experimental verification of various clinical applications without using any toxic chemicals which are required for many existing heat‐sensitive gel recipes.This work has been supported by the US Department of Defense, Breast Cancer Research Program, Concept Award, W81XWH‐08‐1‐0686.
SU‐FF‐T‐55: A Novel Applicator System for HDR Treatment of Endometrial and Cervical Cancer
Authors: Zhang Z , Parsai E , Feldmeier J 
Published: April 2010

Purpose: A new HDR applicator system has been designed to treat gynecological cancers with following specific goals in mind: 1) ability to do volumetric image based patient specific dosimetry, 2) ability to significantly spare the surrounding critical structures, 3) Performing volumetric dosimetry based on delineated target volume and moving away from Manchester point calculation, and 4) provide patient comfort during the implant. It is expected that this system will provide all the functionality of a Fletcher‐Suit‐Delclos (FSD) device and has more versatility in treatment of these cancers. Method and Materials: A disposable applicator manufactured* from plastic material with inflatable partitioned sections to displace rectum and bladder away from the radiation source has been designed. Monte Carlo simulations were performed to compare dosimetry with conventional Manchester system and show superiority of this device in delivering dose to the target volume while sparing rectum and bladder. Comparable optimized plans with conventional FSD system were made using BrachyVision system. Results: Preliminary trials of this applicator used on cadavers revealed superiority in inserting the system in cervical canal through stent, filling the vaginal cavity with liquid contrast for proper CT/MRI imaging. The unaccounted attenuation from the Stainless Steel tubing in FSD applicator is no longer an issue when this applicator is implemented. This new applicator manufactured from all disposable plastic materials, is CT & MR friendly, allows 3‐D treatment planning executable to accurately deliver dose to the target volume as prescribed, allows sparing the normal tissue structure at any desirable level. Our dosimetric studies indicate superior volumetric dose coverage to PTV and easy detachment from the conventional Manchester system. Conclusions: The new applicator once applied will overcome most of the disadvantages from the conventional FSD device and offers numerous superior clinical advantages for patients with gynecological cancer.*Project supported by Varian Medical‐system
SU‐FF‐T‐269: Comparison of Out‐Of‐Field Doses in Pediatric Patients From Craniospinal Irradiations Using Photon, Electron and Proton Spinal Fields
Authors: Georgiev G , Followill D , Ibbott G , Kry S , Fontenot J , White A , Mahajan A 
Published: April 2010

Purpose: Compare the out‐of‐field secondary doses to critical organs in pediatric patients resulting from three different craniospinal irradiation (CSI) treatments. Methods and Materials: A pediatric anthropomorphic Rando phantom was CT scanned for planning purposes following MDACC protocols. Based on the images three different treatment plans employing photon, electron and proton spinal fields, were designed. A common dose prescription for pediatric patients with CNS disease of 36 Gy to the cerebrospinal axis was used for all three plans. The photon and electron spinal fields plans were each delivered three times and the doses at several critical organ sites were measured with TLD. The proton delivery was simulated with MCNPX to calculate the out‐of‐field secondary neutron contribution to the doses at the same critical organ sites. Measured doses for all three treatments were compared. Results: In the majority of the investigated critical organ sites, the doses from the photon spinal fields were higher than from the electron spinal fields. Many of the critical organ doses beyond the spinal target were greater for the photon delivery than for the electron delivery by several orders of magnitude. The entrance doses, as well as the doses lateral to and outside of the target, were up to a factor of two greater for the electron delivery. The expectation for the proton delivery is that the out‐of‐field doses from the secondary neutrons will be less than the conventional electron and photon treatments. Conclusions: An improved clinical treatment decision for pediatric patients can be made using the comparisons between the out‐of field doses for three different treatment methods.Work supported by CA010953 awarded by NCI, DHHS
SU‐FF‐T‐270: The Neutron Dose in the Maze and at the Maze Door
Authors: Krmar M , Kuzmanovic Z , Ganezer K 
Published: April 2010

The Neutron dose was measured at the maze door of a 15 MV therapy accelerator room for three different gantry positions. Two techniques for evaluation of the neutron dose at the maze door the first by Kersey and the second by McGinley, as described in NCRP 151, were compared with measurements. Kersey's method overestimated the dose at the maze door by factors that vary from 2.8 to 5.3, depending on the gantry angle. McGinley's method showed better agreement, although it systematically underestimated the dosage by factors of 0.69 to 0.87, and is also dependent upon the gantry position.The Neutron dose was measured in the maze, at a distance from the door of up to 5.35 m. The difference between the calculated and measured values increases systematically with the distance to the maze door. McGinley's results are much closer to the measured dosages but the rate of increase in the calculated dosages using Kersey's method is much closer to the corresponding rate of increase in the measured neutron dosages.
SU‐FF‐T‐320: The Radiological Physics Center's Annual TLD Machine Calibration Audit and Its Impact On Clinical Trials
Authors: Followill D , Lowenstein J , Palmer L , Ibbott G 
Published: April 2010

Purpose: Demonstrate the importance of the annual TLD machine calibration audit for clinical trial patient dosimetry. Material and Methods: The RPC TLD postal audit program, begun in 1977, currently monitors ∼14,000 megavoltage beams at ∼1700 institutions that participate in NCI sponsored cooperative group clinical trials. This TLD audit uses capsules containing LiF powder and mini‐phantoms that are shipped to institutions annually. The TLD are irradiated, returned to and read by the RPC. The TLD dose is compared to the institution's stated dose. The RPC's acceptance criterion is ±5% and results falling outside the ±5% criterion are investigated to resolve potential dosimetry errors. Results: At the 770 institutions that contribute the majority of the clinical trial patients, ∼5% of the beams audited fall outside the 5% criterion. Correspondingly, 15–20% of the institutions have one or more beams with a potential calibration error. The standard deviation of the RPC/Inst. TLD results is 2.1% about a mean of 0.999. Most institutions rarely have dosimetry errors in two consecutive years. If the frequency of the audit were to occur biennially then the number of potential errors detected would nearly double during that time period (700 vs. 1200 beams) to include ∼33% of the institutions. As the number of uncorrected calibration errors increases, the uncertainty in dose delivered to trial patients also increases. An increase in clinical trial patient dose uncertainty, even at the 2–3% level, can reduce a trial's ability to show differences between experimental arms. Conclusions: Megavoltage beam calibration is the one dosimetry parameter that is unique to each machine and highly dependent on personnel. An independent TLD annual audit serves to detect potential calibration errors. These errors can be resolved, reducing the uncertainty in the doses delivered to clinical trial patients.Work supported by CA010953, CA081647 awarded by NCI, DHHS
SU‐FF‐T‐374: Dynamic Anthropomorphic Eye Phantoms for Targeting and Dose Verification of a Novel Ophthalmic Radiosurgical Device
Authors: Firpo M , Chell E , Herron M 
Published: April 2010

Purpose: Age‐related Macular Degeneration (AMD) is the leading cause of blindness in people over 65 in the U.S. It is a neovascular disease that can result in profound and rapid loss of central vision and has been shown to be susceptible to radiotherapy. A 100kVp tabletop stereotactic radiosurgical (SRS) device has recently been developed to treat AMD. Here we evaluate a new set of anthropomorphic eye phantoms for verifying the targeting and dosimetric accuracy of the device. Method and Materials: A series of eye phantoms were developed to match human eyes in size and shape. The phantoms are made of Solid Water, have a post at the cornea to attach to the clinical fixation assembly, and at the retina have a cutout with fiducial posts that support the precise mounting of laser‐cut pieces of radiochromic film. After irradiation of the phantom, a flatbed scanner and image analysis software are used to assess the accuracy of beam targeting using the fiducial holes in the film. Multiple “treatments” were repeated on stationary phantoms to assess system precision and accuracy. A dynamic eye was also created by attaching set of stepper motors to a phantom. While irradiating the phantom, the motors were driven with clinically‐measured human eye motions to simulate actual treatment and test the automatic beam shut‐off of the system when motion exceeded an established threshold. Results: Phantom measurement precision of 0.1mm was achieved. Static repeated delivery of the therapy showed a system precision of 0.2mm and an accuracy of 0.4mm. Analysis of films irradiated while the eye phantom was being driven with clinically‐measured human motion verified the gating algorithm was capable of protecting radiosensitive structures. Conclusion: The eye phantoms demonstrate that a specialized ophthalmic SRS device can accurately target the back of the eye.Research Supported by Oraya Therapeutics
SU‐FF‐T‐377: Liquid Scintillation Detector System for Real‐Time IMRT Quality Assurance
Authors: Poenisch F , Archambault L , Briere T , Gillin M , Beddar S 
Published: April 2010

Purpose: A liquid scintillation (LS) detector system has been developed to verify dose delivered to a 3D volume. The feasibility of such a system as an IMRT quality assurance device is demonstrated. Method and Materials: The LS detector system consists of an opaque tank (20cm × 20cm × 23cm), a light‐tight conduit and an air‐cooled CCD type camera (Luca, Andor Technology, South Windsor, CT) placed 80 cm away from the center of the tank to minimize stray radiation. The Liquid Scintillator used in this system is BC‐531 (Saint‐Gobain, Newbury, OH). The detector system was irradiated with a 6‐MV photon beam in step‐and‐shoot IMRT delivery mode from a Varian Clinac 21EX. A series of light images were acquired during beam‐on time over all segments of one treatment field. The measured light was compared with the predicted light signal, which was calculated from forward projection of the convolved 3D dose volume obtained from the treatment planning system. Results: An integration time of 150 ms was adequate to provide a resolution of 1 cGy at a dose rate of 400 cGy/min. Frame‐by‐frame acquisition demonstrated the advantage of reduced noise over a single long‐time acquisition. Images acquired during irradiation could easily be distinguished from dark images, since their standard deviation was higher by at least a factor of three. The measured light signal showed good agreement with the predicted light image. Differences occurred due to the light scattering and light reflection. Conclusion: We have validated the LS detector system during step‐and‐shoot IMRT delivery. Further improvements are required to optimize the blurring filter kernel, improve the efficiency of the workflow and add a quantitative analysis of the light output.Supported by the NCI (1R01CA120198‐01A2)
SU‐FF‐T‐426: Fast 4D Monte Carlo Dose Calculations in Deforming Anatomies
Authors: Heath E , Kawrakow I 
Published: April 2010

Purpose: The voxel warping approach to 4D dose calculation calculates the dose deposition on a deformed dose grid in order to determine the contribution of dose deposited at one anatomical state to a reference state. The current implementation of this method in the defDOSXYZnrc Monte Carlo code resulted in a significant increase in computation times. The purpose of this work was an efficient implementation of the voxel warping method in the VMC++ Monte Carlo. Three alternative deformed voxel geometry definitions were investigated to see how they influence the remapped dose calculation efficiency and accuracy. Method and Materials: A set of new deformable geometry classes was created for VMC++ which were compiled as dynamic shared libraries that could be loaded at run time. We implemented three different deformable geometries: a deformed dodecahedron geometry and two geometries based on tetrahedral elements with alternate divisions of the voxel faces. Dose calculations using the new deformable VMC++ geometry were validated by comparison with defDOSXYZnrc by calculating remapped dose in a deforming water phantom and a lung patient deformed from Inhale to Exhale. Dose distributions were compared using the gamma index as well as the Kawrakow‐Fippel test to distinguish systematic discrepancies from dose differences due to random statistical uncertainties. Results: Efficiency gains of the order of 100 were obtained relative to defDOSXYZnrc. A further factor of 1.2 gain in efficiency was realized with the tetrahedral geometries. VMC++ and defDOSXYZnrc calculations were found to agree within 1% in the deforming phantom. Although it could be demonstrated that different folding of the voxel faces influences the dose calculation no differences were found in the patient dose distributions calculated using the different geometries.Conclusion: We have implemented a new deformed geometry class in the VMC++ Monte Carlo code which makes possible efficient and accurate 4D dose calculations.
SU‐FF‐T‐444: Validation and Benchmark of a Source Model for a Varian 6 MV Photon Beam Using Monte Carlo Calculations
Authors: Davidson S , Cui J , Kry S , Vicic M , Deasy J , White R , Ibbott G , Followill D 
Published: April 2010

Purpose: Validation and benchmarking of a newly‐developed measurement‐driven source model based on Monte Carlo calculations. Method and Materials: A measurement‐driven model using the Dose Planning Method DPM dose calculation algorithm is being developed for use with Varian, Elekta, and Siemens 6 MV and 10 MV photon beams. The present work details the validation and benchmarking for the Varian 6 MV beam. The multi‐source model consists of a primary photon point source, an extra‐focal exponential disk source, and an electron contamination uniform disk source. The model accounts for fluence and off‐axis energy effects due to the flattening filter. Dose calculations for field sizes from 4 cm by 4 cm to 40 cm by 40 cm were performed and tested against the basic beam data measurements. In addition, an IMRT homogeneous plan, a stereotactic lung plan, and an IMRT lung plan were delivered to anthropomorphic phantoms housing TLD and radiographic film dosimeters for benchmark evaluations. Results: Comparisons between calculation and measurement of the PDD and dose profiles for all square field size configurations showed agreement within 2%/2 mm for 90% of the data tested. General agreement at the level of 3%/2mm for 85% of the data tested was found in both of the lung treatment plans. However, calculation of the highly modulated IMRT homogeneous plan showed an underestimation of dose of up to 8% locally in the center of the PTV. Conclusion: This work demonstrates a source model that is robust for the Varian 6 MV photon beam; however, only a simple MLC model that did not include the effects of the rounded leaf ends and interleaf leakage was used. We are currently evaluating a detailed MLC model to improve the agreement with measurement.Conflict of Interest: Work supported by PHS CA010953, CA081647, and R01 CA85181 awarded by NCI, DHHS
SU‐FF‐T‐479: Design of a Flexible, Web Accessible, Clinical Outcomes Database to Support Evidenced Based Radiation Treatment Planning
Authors: Mayo C , Riberdy C , Steadman B , Deegan R 
Published: April 2010

Purpose: Lack of patient outcome data for use in retrospective examinations is a notorious problem both for large and small clinics wishing to gain insight on their control rates and morbidity statistics and to correlate these with DVH based endpoints. Often spread sheet based approaches are attempted, but these typically prove inadequate for addressing the department wide problem. Most clinics lack the resources to design databases sufficiently flexible to accommodate evolving determination of clinical endpoints and design of an interface that integrates easily into daily clinical practice. The object of this research was to develop a database and web based interface, to solve these problems and which could be shared as part of an open source effort among multiple institutions. Method and Materials: Objectives for SQL database design were 1) ability to store DVH data and analysis 2) ability to accommodate new or evolving studies without modification of table structure 3) ability to integrate with other department objectives e.g. QA 4) ability to import data from current record and verify system. Web based interface and database were used to conduct internal outcome studies for several anatomic target sites. Results: Meta data tables were used to define, and manage queries from independent endpoint data tables. Database and interface have proven clinical viability and become part of our program to improve documentation. Data reports can be web or spreadsheet based. Largest hurdle for implementation was staff time for data input from charts not yet structured to simplify locating endpoint data. Conclusion: Department databases for monitoring outcome are needed to support evidenced based approach to treatment design. The current application works, is inexpensive, and is promising as the basis of a multi‐institutional open source effort.Conflict of Interest: Work was supported in part by a grant from Varian Medical Systems
SU‐GG‐BRC‐07: 4DCT‐Based Measurement of Radiation Induced Changes in Pulmonary Function
Authors: Ding K , Reinhardt J , Bayouth J , Buatti J 
Published: April 2010

Purpose The present treatment‐planning dosimetry constraints for the lung are based on studies that assume lung tissue is homogeneous in its response to toxicity, irrespective of tissue location or underlying function. No human studies have investigated the relationships between local lung function, spatial radiation dose distribution, and radiation induced lung function changes. We are able to observe radiation‐induced changes in lung tissue function using 4DCT and image registration. Method and Materials Two 4DCT data sets before and after RT from one patient are used in this study. Nonlinear, 3D image registration was applied to register the maximum exhalation image to the maximum inhalation image for the calculation of local lung expansion as a measurement of regional pulmonary function. We compared the changes of pulmonary function before and after RT with planned radiation dose at different locations of the lung. Results The registration accuracy analysis indicated our registration error is on the order of 1 mm. The pulmonary function change in left lung where the tumor is located is larger than it is in right lung (maximum Jacobian change is respectively 0.23 and 0.15). The highest correlation of the pulmonary function change to the delivered radiation dose is in regions which are at the distance of 20 to 25 mm to the tumor region (linear regression, r = −0.73). Further plots between the radiation dose and the pulmonary function change suggest the lung tissue function change is not sole based on radiation dose. Conclusion We described a technique that uses 4DCT, image registration and biomechanical analysis to measure regional lung function. We compared the regional lung function before and after RT to the planned radiation dose distribution and examined the differences at the treatment location and in non‐treatment regions.Conflict of Interest VIDA Diagnostics, Inc (shareholder).
MO‐SAM‐BRB‐02: Proton Physics and Technology
Authors: Smith A 
Published: April 2010

The dose localization advantages of proton beams derive primarily from the Bragg peak in the proton stopping distribution. Therefore, the potential clinical gains expected form proton beams are based on physical, rather than biological, considerations. The rationale for proton therapy is based on the hypothesis that the superior dose distributions of proton beams will lead to increased local control; increased disease‐free survival; decreased treatment‐related morbidity; and improved quality of life. The degree to which each of these end‐points can be changed by proton therapy will depend upon the particular disease site, patient population, and other factors. In the last few years there has been a significant increase in interest in proton therapy and as a consequence, many new facilities are being planned and built. There are currently over 25 institutions worldwide treating patients with proton beams and over 55,000 patients have been treated. There are at least 25 new facilities in various stages of planning and building. We will discuss the rationale for proton therapy, the current status of proton therapy, proton physics and dosimetry, and technology for the acceleration and delivery of proton beams. We will also discuss new developments in proton therapy accelerators and treatment delivery systems. Technologies for carbon ion therapy will also be discussed. We will address issues related to the cost of proton treatments relative to the cost of photon treatments and discuss various ways in which the cost of proton therapy can be decreased.Learning Objectives:Understand1. rationale for proton therapy;2. current status of proton therapy;3. physical characteristics of proton beams;4. beam production and treatment delivery technology for proton beams;5. acceptance testing and clinical commissioning of proton therapy beams; and6. QA for proton treatments