bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐E‐T‐222: Contribution Of In Vivo Dose Measurement To The Intensity Modulated Radiotherapy Technique In The Treatment Of Prostate Cancer
Authors: Akbas C , Tuncel N , Aksu M , Selek S , Koca G , Unal N
Published: July 2013

Purpose: The contribution of in‐vivo dose measurement of organs at risk by TLD and semiconductor detectors during Intensity‐modulated radiotherapy technique in treatment of prostate cancer was studied. Methods: Appropriate prostate cancer patients target and organs at risk contours that managed for IMRT planning were fusion on CT images of Rando phantom. For PTV1 and 2 the equally angel nine fields (within 200°− 160°)IMRT plans were designed using 6MV photon energy with 180cGy per fraction to total dose of 45 and 72Gy respectively. The point dose and two‐dimensional dose measurements for the quality control evaluation of IMRT plans were done and found in appropriate limits. The 3 sub‐slab of Rando phantom were re‐made from paraffin and rectum cavity was created in accordance with the probe for measuring rectal dose. Based on dosimetric method each dosimeter was selected and located on measurement region. Prostate IMRT plans were applied to the phantom. In‐vivo dose measurements were repeated several times by TLD and diode, obtained dose values for rectum and bladder compared with TPS. Results: Both semiconductor and TLD dose measurement values for bladder and rectum is generally in agreement with the TPS. The rectum dose measurement values were differing from TPS up to 30% in intense dose gradient regions. This is because when the coordinates of the reference points are in intense dose gradient regions, +/− 1 mm changes in position create +/− 3–10% difference between the calculated and measured doses. Conclusion: The intracavitary rectum and bladder probes used for brachytherapy dosimetry applications could be applicable in external radiation treatments. In‐vivo dosimetry has an important role in the quality assurance of radiotherapy, especially to preventing errors which may occur in every stage of treatment. In this context,for more complex treatment techniques like IMRT the traditional in‐vivo dosimetric methods using TLD and semiconductor diodes was found to be reliable.
SU‐E‐T‐224: A Study of Real‐Time Treatment Quality Assurance
Authors: Pan X , Bradley W , Boyd C , Kennedy K , Robertson L , Jones D , Wauqua M , Smith L , Ochran T
Published: July 2013

Purpose: The purpose of this work is to investigate real‐time radiation treatment quality assurance (QA) in radiation therapy. Methods: An ArcCheck phantom was selected as a patient named patient_AC for this study. CT simulation was performed for patient_AC and 2 treatment plans, i.e., a sliding window (S_IMRT_Plan) and a step‐and‐shoot (SS_IMRT_Plan) IMRT plan, were designed using Eclipse treatment planning system (TPS). Pre‐treatment QA was done prior to treating patient_AC using an ArcCheck phantom (Sun Nuclear Corporation) and electronic portal imaging device (EPID) (portal dosimetry, Varian Medical System). Integrated image was taken for each beam during the treatment by EPID at the source‐detector distance of 150cm. Absolute intensity of the image was measured in an area of 1cmx1cm centered at the crosshair position. The cumulative intensity in the treatment was used to verify the dose delivered along the treatment course. The variation of the intensity was measured by taking the first treatment data as a reference. Exit dose of the patient_AC was calculated in the Eclipse TPS and was compared to the measured intensity by EPID relatively. Results: 12 and 11 treatments were finished using the SS_IMRT_Plan and the S_IMRT_Plan, respectively. The cumulative intensity of the first treatment is 21.36CU for the ss_IMRT_Plan, and 24.55CU for the s_IMRT_Plan, respectively. The variation of the absolute intensity during the treatments for both plans is within 0.5 CU [range −0.10 to 0.29 CU, average 0.05CU for SS_IMRT_Plan; range −0.20 to 0.05 CU, average −0.09CU for S_IMRT_Plan], and the relative difference is within 2% [range −0.45% to 1.38%, average 0.23% for SS_IMRT_Plan; range −0.81% to 0.21%, average −0.36% for S_IMRT_Plan]. Exit dose calculated in the Eclipse TPS for both plans agreed well relatively with the intensity measured by EPID. Conclusion:The proposed method can provide a way to real‐time monitor the dose delivered to the patient.
SU‐E‐T‐226: SRT/SBRT Patient Specific QA with a New High Resolution 2D Detector Array
Authors: Stathakis S , Mavroidis P , Markovic M , Esquivel C , Myers P , Crownover R , Li Y , Papanikolaou N
Published: July 2013

Purpose: To evaluate the performance of a new commercially available device for patient specific SBRT pretreatment QA.Materials and Methods: The PTW OCTAVIUS1000SRS was used in this study for patient specific QA measurements for patient undergoing SBRT treatments. Forty five (n=45) individual field and five (n=5) composite plans were measured. All plans were optimized and calculated using Eclipse v8.9. All measurements were performed with the gantry static at the upright orientation. The detector array was placed inside the PTW Octavius II phantom and the source to detector plane distance was set to 100cm. The gamma index was the metric of choice in order to quantify the agreement between measurements and calculations. The tolerance criteria used for the evaluation were 3% dose difference and 3mm distance to agreement and also 2%/2mm. Results: The results of the comparison using 3%/3mm were inconclusive. The number of detectors included in the comparison and the rather loose criteria used caused most comparisons to yield a gamma index of 100%. Comparing the measured and calculated planar dose distributions using 2%/2mm as gamma index tolerances, the average gamma index was 95.9% (min:90.9, max:99.2%). The agreement was also reflected while comparing profiles and isodose distributions. Conclusion: The new PTW Octavius 1000SRS device is able to provide a reliable solution for the patient specific QA of SBRT and SRS plans where small fields are commonly used. Project was partially funded by PTW, NY
SU‐E‐T‐227: Feasibility of Collision Avoidance Using In Room 3D Camera
Authors: Cardan R , Popple R , Wu X , Duan J , Shen S , Brezovich I
Published: July 2013

Purpose: To determine the feasibility of detecting potential collisions between hardware and patient without the need of a CT scan. Methods: A 3D camera (Kinect for Windows, Microsoft) was mounted onto an on board imaging arm and 3 depth images at different angles were taken of an anthropomorphic phantom in a treatment position. A convex hull was then calculated from the depth vertices for use in a computer collision simulation. Positive collisions were then determined by manually moving the couch and gantry over a sample of their motion ranges. The results were compared with a computer simulation that calculated the positive collisions from the scanned geometry. Results: The simulation calculated 64,620 collision potential configurations of the phantom/couch and gantry at 1 degree increments in 4.36 sec using an Intel Core i3 processor with 8GB of ram. The accuracy of the calculation was assessed by dividing up the results into four different groups: true positive (correctly predicted collision), true negative (correctly predicted no collision), false positive (wrongly predicted collision), false negative (wrongly predicted no collision). There were 3949 measured data points, which resulted in TP = 1131, TN = 2437, FN = 275, and FP = 106 points. The receiver operating curve accuracy metric (TP+TN)/(TP+TN+TN+FN)) was then calculated from these groups as 90.35 %. Conclusion: We have successfully demonstrated a framework that could be used to scan patient geometry on the treatment table for use in collision avoidance. This could also be used in the simulation step of treatment to avoid planning geometrically infeasible setups. Collision prediction inaccuracies are attributed to inadequate point cloud data to accurately describe phantom geometry. Better sampling with improved reconstruction software should enable the ability to completely avoid planning of non‐deliverable beams or collisions during treatment.
SU‐E‐T‐229: Adopting Toyota Production System Principles & Tools to Improve Radiation Therapy Processes
Authors: Boddu S , Neba N , Palaniswaamy G , Massingill B , Tseng T , Morrow A , Deb N , Mutyala S , Rangaraj D
Published: July 2013

Purpose: To implement Toyota Production System (TPS) lean tools and techniques in the Department of Radiation Oncology to maximize the individual productivity, process efficiency, deliver high level of quality and safe patient treatments. Methods: To continuously and relentlessly improve the performance of individuals and processes to an acceptable level of operation we have categorized the departmental operations into safety, quality, deliverability, cost and morale. We had issues with all aspects of the radiation therapy process that affect the quality and deliverability of treatment to our patients. To address these areas we adopted TPS lean principles and tools with existing resources such as gemba walk, visual controls and daily huddle where therapists, dosimeterists, physicists and physicians participate towards the lean management of the processes until the requested resources are available. These issues are addressed with clear communication through simple tools and with individuals in the department. To make this process and progress transparent, we have placed a huddle boards consisting of daily update of issues, actions needed to address the issues, and progress in safety, quality, deliverability, cost and morale, and effects of these progressions to the department. Results: With the implementation of simple, direct and effective TPS lean techniques in the department and hard stop policy of postponing IMRT patients not ready by the noon of the day before the first treatment, the work flow has become more streamlined and has helped in timely start of the patient treatments. With the availability of an assigned physicist to answer questions during the clinical hours, physicians, dosimeterists, and therapists concerns were also addressed in timely and orderly fashion and boosted the morale among the departmentConclusion: TPS lean techniques have been effective in decreasing the patient delays while increasing quality and safety to the patients with same cost and improved staff morale.
SU‐E‐T‐230: Patient Safety Improvement Related to Changes in Ongoing Radiation Treatment Plan Identified with Near‐Miss Incidents Reporting
Authors: Zeng J , Nyflot M , Sponseller P , Kusano A , Novak A , Jordan L , Carlson J , Ermoian R , Kane G , Ford E
Published: July 2013

Purpose: A significant portion of patients undergoing radiation experience a change in the treatment plan during the treatment course for a variety of reasons, including adaptive planning due to tumor response and change in fractionation due to patient clinical status. This study tests whether mid‐course changes to treatment plans increase risk of errors through the use of a large institutional near‐miss incident reporting system. Methods: We analyzed incidents from a departmental near‐miss incident reporting system launched in 2/2012. All incidents were prospectively reviewed weekly by a multi‐disciplinary team including physicians, therapists, dosimetrists, physicists, nurses, and administrative staff. Incidents were assigned a near‐miss severity score ranging from 0 to 4 (no impact/mild/moderate/severe/critical), reflecting the potential harm of the incident if it had reached the patient. Monthly root‐case‐analysis is performed on incidents with the highest severity. Incidents related to change‐in‐plan were flagged, and severity score for these were compared to other incidents via t‐test. Results: From 2/2012 through 12/2012, 662 incidents were submitted through the departmental near‐miss incident reporting system. On multi‐disciplinary review, 59(9%) incidents were directly attributable to a change‐in‐plan. Average severity score for the 59 change‐in‐plan incidents was 1.9, significantly higher than score of 1.5 for other incidents not related to change‐in‐plan (p=0.02). Three(5%) near‐miss incidents were assigned the highest severity score of 4, with issues including: wrong isocenter, wrong fields assigned to new plan, and wrong information in new treatment plan due to existing plan. Conclusion: Changes in treatment plan are sometimes required to provide highest quality of care for patients receiving radiation. Although near‐miss incidents related to change‐in‐plan are relatively uncommon, when they do occur they are more severe than other types of incidents that are observed in the course of clinical operations. Development is underway for new safety process specifically tailored to this identified high‐risk patient group.
SU‐E‐T‐232: Safety and Quality Improvements in a Pediatric Total Body Irradiation Procedure
Authors: Cao N , Ford E , Nyflot M , Ermoian R , Young L , Hendrickson K
Published: July 2013

Purpose: Through the use of incident learning, safety‐critical areas were identified in our current procedure for pediatric patients undergoing total body irradiation (TBI) for bone‐marrow transplant. These are relatively rare and complex procedures requiring non‐standard setups and administration of anesthesia. The purpose of this study is to simplify and standardize the simulation and planning procedure for pediatric TBI to improve the safety and quality of care. Methods: Motivated by near‐miss incidents, a systematic review of current TBI procedures was conducted, and the following issues were identified: unclear communication describing variations in setup at simulation versus treatment related to anesthesia requirements, confusion about measurement units, unclear criteria for various setup options to accommodate patients ranging in age from infancy to 7 years, and variations in compensator design methods. To address these issues, a simulation form was designed with detailed instructions and documentation requirements. Dose calculation and tissue compensation procedures were redesigned to remove set‐up variations. Calculations were performed on 28 previously‐treated patients to determine the dose uniformity with the new vs. old method. Results: Feedback from clinical staff indicates that the new simulation form improves interdepartmental communication and decreases the risk of treating patients in a setup that differs from that used during the simulation. The new compensator design significantly improved patient dose uniformity: 0.8±0.4% (new method) vs. 4.2±2.3% (old method) (p < 0.01). The data indicates the new compensator design will Results in fewer out‐of‐tolerance in vivo dosimetry readings and reduce associated re‐planning efforts, which is especially critical for single‐fraction treatment. Conclusion: For an institution averaging one pediatric TBI case per month, standardization of the procedure simplifies the planning process and improves patient safety. Since there are few technical reports about pediatric TBI, this experience may be especially beneficial for other centers with low volumes of pediatric TBI patients.
SU‐E‐T‐236: Checklists — A Powerful Error Mitigation Tool in Radiation Therapy
Authors: Palaniswaamy G , Morrow A , Boddu S , Mutyala S , Deb N , Rangaraj D
Published: July 2013

Purpose: In our clinic, we treat a variety of patients with external beam radiation therapy, linac‐based SRS, SBRT and Brachytherapy — HDR and LDR. With limited resources and being a learning and teaching environment, we have implemented checklists at several steps in the clinic in order to reduce errors and also as a tool to guide new staff to get oriented to the clinic specific processes in a quick and efficient way. To portray the importance and significance of use of checklists as a powerful tool in mitigating errors in radiation therapy clinics. Also, checklists provide robust means of bringing new staff on‐board and cross‐training. Methods: The initial work of creating checklists for a process requires a clear and deep understanding of the process, significant steps/items, most commonly missed steps/items and their impact on patient care, safety and quality. Checklists have to be created with patient care, comfort and quality in mind. After creating checklists, they have to be critically scrutinized and constantly evaluated and updated during the initial testing phase before it can be standardized in the clinic. Results: In our clinic, we were able to implement checklists for several processes such as frame‐based SRS treatments, frame‐less SRS treatments, SBRT treatments, LDR Pre‐implant checklist, LDR post‐implant checklist, HDR treatments, HDR weekly chart checks and billing. Implementing checklists required physicist time and several iterations of critical review and modifications before standardization. Billing issues were resolved and there were fewer charges missed. Errors such as identifying the appropriate cones before treatments, completion of appropriate chart checks, documents and approvals before treatment were all resolved which resulted in smooth operation during patient treatment. Conclusion: Implementing checklists helped us streamline the processes and eliminate some of the common errors in daily operation. Both HDR and stereotactic services benefitted most from implementing checklists.
SU‐E‐T‐238: Investigation of Heuristic Checks for Treatment Beam Data
Authors: Chang J , Heaton R , Islam M
Published: July 2013

Purpose: While radiotherapy treatment is accurately delivered in most cases, errors do occur with potentially fatal consequences. Many procedures have been developed over the years to minimize radiation therapy errors. However most of these procedures involve costly time consuming tasks and yet are not realistically fool‐proof. Errors can still percolate through the process due to human errors or system malfunctions. We have investigated the development of an automated heuristic check of the beam data prior to transfer to the delivery system. The primary objective of this check is to identify any gross error without significantly impacting costs. Methods: The total energy fluence in a treatment plan contributes mainly to the integral dose to the targeted volumes. To a first approximation, a simple correlation should exist between the integral dose to the target volume and the total energy fluence of the treatment beams. This correlation was investigated for clinical IMRT plans targeting the prostate and head & neck regions. Correlations between the summation of (Monitor Unit(MU)*Segment area) and integral CTV dose per fraction were investigated. Results: The sum, ΣMU* Segment area, used as a surrogate for the total energy fluence, was found to correlate with the integral dose, approximated as the CTV*prescribed dose. A linear fit of total energy fluence vs. integral dose for prostate and head & neck plans yielded a correlation coefficient of 0.99, with a slope of 3.3*10 6J*cm 2*MU ' . Of the plans investigated, 90% of these were contained with in a region defined by ±5% of this slope. Conclusion: A useful correlation between the ΣMU*Segment area and integral target dose was identified. This correlation can be used to automatically identify gross treatment errors and provide a low cost barrier to some types of catastrophic treatment errors.
SU‐E‐T‐242: A Gateway for GPU Computations in Radiotherapy
Authors: Shi F , Sivagnanam S , Folkerts M , Gautier Q , Jia X , Majumdar A , Jiang S
Published: July 2013

Purpose: Graphics Processing Unit (GPU) has become increasingly important in radiotherapy. However, it is still difficult for general clinical researchers to access GPU codes developed by other researchers with GPU expertise, and also for developers to benchmark their codes. It is quite often to see repeated efforts spent on developing GPU codes with low quality. The goal of this project is to establish an infrastructure for sharing GPU codes in the community. Methods: We deployed a GPU code sharing infrastructure on a GPU cluster. A number of codes developed in our group can be accessed via a web interface. To use the services, researchers first upload their test data or use the data provided by our system. Then they have to select the GPU device they are going to run the codes. Our system offers all mainstream GPU hardware for code benchmarking purpose. After the code running is complete, the system will automatically summarize and display the computing results. We will also release a SDK to allow the developers to build their own algorithm implementation and submit their binary codes to the system. The submitted code will be systematically benchmarked using a variety of GPU hardware and representative clinical data provided by our system. Results: This project provides a platform to the public to access a variety of GPU codes for radiotherapy research via a web interface. With the help of this platform, researchers are able to focus their efforts on clinical research. Developers will also benefit from this platform by benchmarking their codes on various GPU platforms and clinical data sets and comparing with other people's codes for the same application. Conclusion: The gateway for GPU code developers and clinical research users can greatly facilitate the adoption of GPU codes in radiotherapy.
SU‐E‐T‐243: Analysis of Planner Dependence in IMRT
Authors: Roy A , Das I , Srivastava S , Nohadani O
Published: July 2013

Purpose: To establish trends in the observed variations within large sets of IMRT treatment plans. Past data of comparable treatments are statistically analyzed to identify clinical preferences and establish best practices for future decision‐making processes. Methods: We propose three statistical measures of variations in the DVH of 100 head and neck cancer patients from IU‐Simon Cancer Center: a) Standard deviation for delivered dose, std(D), to specific volumes, b) standard deviation for volume, std(V), receiving a specific of dose, and c) a steepness measure for DVH and 1‐standard deviation at specific dose points as a measure for falloff preference. Results: The three methods show considerable variation amongst DVHs: a) Negligible dose deviation until 70% volume, a steady increase to std(D)=22% at 100% volume, followed by a steady decrease to std(D)=0% at 115% volume. On the other hand, b) standard deviation of volume is rather constant at 3% until at high volumes (100%), where it increases to 15%. c) Average steepness of DVH over the 100 patients is negligible until 94% dose, after which it falls steadily to −13 at 104% dose. It then steadily climbs back to 0 at 110% dose. This change depicts the dose falloff on a typical DVH. The 1 standard deviation spread is most evident between 96% and 110% dose, with a maximum of 7.2 at 103% dose. Furthermore, there is a ripple effect at 85% dose with a standard deviation of 1.8 that is distinct from the usual trend. Conclusion: Unanimous decisions for DVHs exist only at lower values of volume and dose. However, significant variations are found in the falloff region of the DVH. For this region, the increased variations in the steepness suggest that individual preferences are more divergent. A closer unanimity in future decision‐making may lead to enhanced planner independence of IMRT treatments. Joint Purdue‐IU Seed Grant
SU‐E‐T‐247: Design and Implement of the Radiation Therapy Case Conference Multi‐Media System Based On Windows Remote Desktop Feature
Authors: Wu Q , Li G
Published: July 2013

Purpose: To explore a method of using a computer system for multi‐media cases conference in clinical radiation oncology, in order to replace the traditional use of film images and paper. Methods: In a conference room without any treatment planning system(TPS), on a dedicated networked computer, we use Remote Desktop feature of Windows XP to remote access an Varian Eclipse TPS and the radiation therapy information management system (RTIMS), which is an in‐house developed system based on the flow of radiation therapy. Then in this room, we can online read the information of CT images, target volumes, treatment plans, electronic medical records and etc, and project it on the screen. Results: There has been half a year since we successfully set up a radiation therapy case conference multi‐media system(RTCCMMS) in the department. With this method, we can share the TPS in another room, and do not need buy another TPS. It is convenient and effective that the oncologists and physicists conduct a collective case discussion. Conclusion: This method required equipments are simple, and it is a safe and reliable technology, greatly improving the clinical efficiency and quality of medical care. Project supported by the National Natural Science Foundation of China (Grant No.81101694).
SU‐E‐T‐250: Measurements of Surface and Interface Dose for 6 MV Photons in a Parallel Magnetic Field
Authors: Ghila A , Fallone B , Rathee S
Published: July 2013

Purpose: The patients treated using Linac‐MR systems, being developed for real time MR guided radiotherapy, will be irradiated in the presence of a magnetic field. The present study presents the entrance surface, buildup and interface doses measured in a 6 MV beam in the presence of a parallel magnetic field. Methods: A set of phantoms with one angled surface, and a phantom with an adjustable air gap were constructed out of polystyrene. These phantoms were designed to measure both the percent depth dose and the surface dose at the same time using Gafchromic film. Two solenoid electromagnets, placed on top of each other, were used to generate a magnetic field along their vertical bore (26.5 cm deep x 17.5 cm diameter) and a decreasing fringe field outside. The magnetic field strength is variable from 0 T to 0.2 T at the bore's center. The phantoms were placed inside the bore and irradiated using field sizes that avoided irradiation of the magnetic coils. Results: The parallel magnetic field was found to focus the contaminating electrons produced in the linac head and in the air column above the phantom, within the beam area. The surface dose, for all the surface angles investigated, increased by ∼15% of the Dmax dose at 0.2 T magnetic field. For the air gap phantom the concentration of electrons inside the beam area by the parallel magnetic field is clearly visible inside the air gap on the depth dose film and in the percent depth dose curve. Conclusion: We have devised an experimental system to measure the radiation dose of a clinical linac in a parallel magnetic field. We are currently performing Monte Carlo simulations that include magnetic fields replicating the measurement system. The verified Monte Carlo system will make the dose calculation engine for future linac‐MR systems.
SU‐E‐T‐251: 3D Collision Viewer for Proton Therapy Treatment Planning
Authors: Hojo Y , Gillin M , Suzuki K , Wu R , Zhu X
Published: July 2013

Purpose: In proton treatment, in order to reduce beam penumbra, it is desirable to place the treatment snout as close as possible to the patient skin. However, collision between treatment couch/patient and snout is not predicted by current treatment planning system. We developed and validated an interactive 3D Collision Viewer for patient clearance check during treatment planning. Methods: The 3D Collision Viewer calculates the shortest distance between two major groups of objects, couch group and nozzle group. The couch group includes a couch and a patient and the nozzle group includes a nozzle, a snout and extensions for snout. The software displays the object coordinates and the shortest distance in the 3D Viewer. The tool was developed with a video game development framework to realize 3D interactive performance. Surface coordinates of equipment including the patient were defined relative to the iso‐center and created by commonly used CAD software. The equipment coordinates and the shortest distance are interactively updated on any change of equipment setting by the user. The video game framework takes care of equipment surface coordinate motion according to each equipment setting. The shortest distance was obtained by comparing distances between all combination of nozzle meshes and couch meshes. To confirm the numerical accuracy of the shortest distance calculation, the distance between nozzle and 2 cm diameter sphere was compared with the expected distance. Results: Numerical accuracy of the distance calculation is better than about 1/40 of mesh size of the sphere. The accuracy mainly depends on the surface data preparation. Average calculation time for a sample configuration, which had 156 vertices and 94 meshes for the nozzle and 2707 vertices and 3758 meshes for couch, was less than 0.6 seconds. Conclusion: 3D Collision Viewer is capable of detecting potential collision during treatment planning.
SU‐E‐T‐254: Tissue Specific Characteristics of Prompt Gamma in Proton Radiotherapy: A GEANT4 Simulation Study
Authors: Lau A , Chen Y , Ahmad S
Published: July 2013

Purpose: An in‐vivo range verification system for proton radiotherapy utilizes prompt gamma photon emitted from the de‐excitation of daughter fragments (e.g. 12C, 16O) produced in an interaction of incident proton in materials with time scales in the range of nano seconds. The goal of the present investigation is to study depth dependency of the yield of emitted prompt gamma rays from energetic proton interactions in different materials. Methods: A coincidence detector system for identifying prompt gamma was simulated with Geant4 Monte Carlo toolkit version 9.4.9 p02. The interaction of 110 MeV protons with target phantom (5 cm × 5 cm × 50 cm) was used. A virtual detector (5 cm × 5 cm × 1 mm) was replicated 500 times to form a bank of detectors. A lower bank was placed 1 cm above the phantom while another bank was placed 1 cm above the lower bank. A coincidence requirement was met when a gamma had passed through both a bottom detector and the corresponding top detector segments directly above it. Our investigation used built‐in physics list consisting of electromagnetic and nuclear interactions. Three different types of phantom materials (Water, PMMA and Bone) were used. Results: The emitted prompt gamma yields from 12C (energy range 4.21 to 4.59 MeV) and 16O (energy range 5.79 to 6.31 MeV) versus depth showed similar distributions irrespective of materials. The depths of the maximum yields from 12C were superficial to that from 16O and Bragg peak depths. The yields from 12C were greater to that from 16O up to 5 mm superficial to Bragg peak; whereas around Bragg peak the yields of 16O dominated. Distal to Bragg peak, the yields from 12C started to dominate. Conclusion: A depth dependent relationship may exist between the characteristic prompt gamma production and Bragg peak. More careful analysis has now been planned.
SU‐E‐T‐260: Risk of Second Cancer From Scattered Dose During the Radiation Therapy with Lung Cancer
Authors: Kim D , Chung W , Shin D , Park S , Chung K , Yoon M
Published: July 2013

Purpose: To compare the organ equivalent doses (OEDs) from scattered and leakage doses following intensity‐modulated radiotherapy (IMRT), volumetric arc therapy (VMAT) and tomotherapy (TOMO) in patients with lung cancer. Methods: IMRT, VMAT and TOMO were planned for the lung cancer patients. The OEDs are estimated from the measured corresponding secondary doses during irradiation at various points 20 to 80 cm from the iso‐center by using the radio‐photoluminescence glass dosimeter (RPLGD) on the surface. Results: The secondary dose per Gy from IMRT, VMAT and TOMO for lung cancer, measured 20 to 80 cm from the iso‐center, are less than 2.0, 1.5 and 1.0 cGy, respectively. The normalized mean values of relative OED of secondary dose of IMRT, VMAT and TOMO are 100%, 89% and 42% for thyroid, 100%, 82% and 42% for pancreas, 100%, 78% and 49% for bowel, 100%, 73% and 73% for rectum, 100%, 74% and 82% for prostate. The secondary dose and OED from TOMO became similar to those from IMRT and VMAT as the distance from the field edge increased. Conclusion: OED based estimation suggests that the secondary cancer risk from TOMO is less than or comparable to the risks from conventional IMRT and VMAT in patients with lung cancer.
SU‐E‐T‐262: Comparing Linear Accelerator Gantry Angle Measurements Using An EPID and Spirit Level
Authors: Treas J , Jones A , Higgins K
Published: July 2013

Purpose: To compare the precision and consistency of measuring Linear Accelerator Gantry Angles between an Electronic Portal Imaging Device (EPID) and a Spirit Level. Methods: A cubical phantom was created by placing radio opaque markers therein at precise positions. The phantom was placed on the treatment table and aligned with the lasers in the treatment room. Using the Linear Accelerators EPID, images of the phantom were taken at the four primary gantry angles 0. 90. 180 and 270 degrees. Over a period of 1 month, 25 images were acquired at each primary gantry angle. The images of the phantoms were analyzed to calculate the gantry angle using a macro created with Image J (NIH). In the same time period, 13 gantry angle measurements were made using a spirit level at the four primary angles. Results: The average and standard deviations of gantry angles for the EPID based method at the four primary gantry angles 0, 90, 180 and 270 were −0.1(0.011), 90.0(0.011), 180.2(0.015) and 270.0(0.006) degrees respectively. In comparison, the spirit level based measurements yielded average gantry angles of 0.2 (0.03), 90.2 (0.04), 180.1(0.01) and 269.9(0.05). Results of each method similar and are within +/− 0.2 degrees of the intended angle. There is however a noteworthy difference in standard deviations between each method. Conclusion: The precision of each method yielded results within the linac specifications. Improvements to the materials and construction of the phantom could improve gantry angle accuracy by reducing positioning errors in the markers. More data needs to be acquired to determine which method is more accurate. However, the EPID gantry angle measurements strongly suggest an advantage over the spirit level results with more reproducible results as demonstrated by smaller deviations from the mean.
SU‐E‐T‐263: MRI‐Guided Targeted Prostate Cancer Radiation Therapy: Multi‐Image Co‐Registration
Authors: Bao A , Zheng Y , Ellis R , Fabien J , Rhodes C , Colussi V , Wessels B
Published: July 2013

Purpose: MRI has been used for guiding treatment planning and post‐treatment evaluation in prostate cancer targeted radiation therapy. However, the co‐registration of MR images to CT or ultrasound images needs manual adjustment due to the motion of the pelvic organs. To improve the accuracy of the co‐registration of MR images to CT or ultrasound images, we investigated the use of simultaneous image co‐registration of multiple MR images to CT or ultrasound images utilizing MIM™ software. Methods: Multiple MR images, including T1 without and with Gd‐contrast agent, T2, and diffusion weighted images were acquired using the same preview image allowing MR images to be inherently co‐registered. By using MIM™ image fusion software, multiple MR images were simultaneously fused with either CT or ultrasound image. Adjustment of CT/MR image co‐registration uses the best contrast information from one or multiple MR images at each micro‐structure location. The alignment of individual MR image was then adjusted to account for their individual contrast characteristics. Results: Thirty seven prostate cancer patients were studied using this image co‐registration method. By using this strategy, T2‐weighted MR images can be accurately matched to CT images with <2 mm of the prostate margin. Newly acquired T1‐weighted MR images can be fused accurately to pelvic bones, prostate and pelvic lymph nodes. However, the alignment of the rectum, bladder, and bowel can vary. Conclusion: The simultaneous multiple MR image co‐registration technique provides a strategy of efficient multiple MR image co‐registration, while improving the accuracy of image co‐registration. This image co‐registration technique has also been used in other locations, such as the spine.
SU‐E‐T‐266: New Improved Methods to Read Output Factors for Small Fields
Authors: Smith C , Bacala A , Pella S
Published: July 2013

Linear Accelerators represent big challenges in measuring output factors for small fields. Output factors are crucial for dose calculations in intensity modulated radiation therapy (IMRT) planning. The challenge comes from charged particle non‐equilibrium conditions and high dose gradients, type, and the detectors used. We analyze all available detectors and the output factors obtained with them. Based on this we come with recommendations in a protocol for accurately measuring the output factors for commissioning any linac that will perform IMRT. Advances in therapy equipment implicitly encourage the use of smaller treatment field sizes on equipment originally designed for treatments based on conventional, broad photon fields.Challenges at small fields: penumbra size vs. detector size, lack of lateral electronic equilibrium (LEE), photon energy and spectrum dependence on detector response, finite detector volume, detector density effect, detectors' polarity effects, physics at small fields: field perturbation, fluence. Method: Initial data gathered have led to necessity of using small detectors for small fields. We propose to use different detectors to measure the output factors for microMLC linacs using three detectors: a diode detector and two types of micro ionization chambers (for corroborative measurements and consistency). We compared the performance of the Edge detector, PTW pinpoint and Exradin A1 ionization chamber. The output factors are taken at three different depths: (dmax, 2cm, and 5.0cm) in SAD setup. Comparison of these data lead to precise measurement of the correction factor to provide 1%–2% variation in calculated doses for IMRT with the Treatment Planning System. DISCUSSION: From TG‐155 recommendations, dosimetric measurements should be taken with more than one detector system. Small detectors should be used that has minimum energy, dose and dose rate dependence. If field size is small compared to the detector, measurements should be taken at greater source to surface distance with proper correction. Advanced Radiation Physics Inc
SU‐E‐T‐268: Comparison of Dosimetry Characteristic Between Brass Mesh Bolus and Tissue Equivalent Bolus (conventional Bolus)
Authors: Gong J , Pavord D
Published: July 2013

Purpose: To compare the dose characteristic at surface and beneath between a mesh brass bolus and a conventional one, to determine equivalence between those two kinds of bolus. Methods: Measurements were made with 6MV photons on a Varian 2100C linear accelerator using a PTW parallel plate chamber. Data were collected on surface and beneath by use of various layers of brass mesh bolus against various layers, 0.5 cm increment, conventional bolus at 100 SSD in a solid water phantom perpendicular to the beam central axis. The measurement had identical setup. Surface dose and PDDs were created. Results: The surface dose is 15% lower using a mesh brass bolus compared with that using a conventional bolus. After 1.5 cm, the dose characteristic approaches the same for these two kinds of bolus. Our test also shows that three layers of the brass bolus has closest PDD profile to 0.5 cm conventional bolus. The different of the dose profile gets smaller at deeper. After 1.5 cm, they can be treated as equivalence(less 5% different). With a brass bolus, the percentage deep dose gets flatter from depth 0.8cm to dmax 1.5 cm. Conclusion: Mesh bolus does escalate the surface dose. But it is not equivalent to a conventional bolus in the intended area. If we use it as alternate to tissue equivalent bolus material, we would jeopardize 15 % under dose on the skin. More data needs to reveal the long term biological effect using brass mesh bolus before we make a decision for its clinical application.
SU‐E‐T‐270: Comparison of Different Methods of Iodine‐125 Fixation On Silver Substrate for a Brachytherapy Seed
Authors: de Souza C Daruich , Rostelato M Chuery Martins , Zeituni C , Moura J , de Mattos F Rodrigues , dos Santos Peleias F , de Moura E Santana , Feher A , da Costa O
Published: July 2013

Purpose: Brachytherapy treatment is a form of treatment in which source is in contact or placed within the patient. The iodine125 brachytherapy seeds can be used to treat prostate, brain and ophthalmic cancers. Most of the population has no access to this treatment because of its high cost ($ 60.00 each seed, 80 to 120 used for only one patient). For this reason, IPEN (Institute of Energy and Nuclear Research) develops new a seed.Methodology: Four different methods were compared: Method 1 and Method 2: Chemical deposition and eletrodeposition described in U.S. Pat. n. 4,323,055; Method 3: IPEN's new method presented in Development and production of radioactive sources used for cancer treatment in Brazil. Nukleonika, 2008; Method 4: New method developed in IPEN using oxidant agent that enforce the AgI formation. Results: Method 1: fixation efficiency 65.16%; process cost R $ 7.04Method 2: fixation efficiency 70.80%; process cost R $ 6.58 Method 3: fixation efficiency 55.80%; process cost R $ 8.24Method 4: fixation efficiency 90.11%; process Cost $ 5.00ConclusionThe fourth method achieved the efficiency, 90.11% and lowest cost $2,5. The results show that this is the best method to be implemented in IPENs new laboratory.
SU‐E‐T‐273: Investigation of Alopecia for Nasopharyngeal Carcinoma Patient Treated with IMRT and Tomotherapy
Authors: Kong WYC , Lee FKH , Chau RMC
Published: July 2013

Purpose: A nasopharyngeal carcinoma patient treated with Tomotherapy was presented with severe alopecia in the follow up clinic 8 weeks post treatment. Dosimetric investigation was carried out on a group of NPC patients to look at scalp follicle doses using IMRT and Tomotherapy techniques. Methods: Scalp follicle and upper neck follicle structures were defined in treatment planning system. Total of 16 Tomotherapy and 16 IMRT NPC patients were investigated, all patients were at different stage through treatment. The median dose for each structure was compared between IMRT and Tomotherapy techniques. The degree of alopecia for each patient was graded with reference to Cancer Therapy Evaluation Program CTCAE V3.0. Results: The mean median dose for scalp follicle structure was recorded as 1635.6±213.4cGy for Tomotherapy, and 1604.4±448.9cGy for IMRT. The mean median dose for upper neck follicle was recorded as 3744.8±352.0cGy for Tomotherapy, and 3539.5±512.3cGy for IMRT. A 2 tailed t test was performed on the results, at 95% significant level, the results show no significant difference in median doses for both follicles regions between Tomotherapy and IMRT treatment for NPC patients. Most patients on treatment for NPC started to experience some degree of alopecia from the last 2 weeks of treatment. Patients from the follow up clinic who had completed treatment over 20 weeks were not presented with alopecia symptoms. These results suggest alopecia is a temporary side effect. Conclusion: There is no significant difference in median doses to the follicles regions between IMRT and Tomotherapy techniques. With reference to Lawenda BD study, and the results from this study suggests the risk of permanent alopecia is low for our current planning techniques.
SU‐E‐T‐276: Equivalent Dose in Children Receiving Craniospinal Irradiation with Photons in a Developing Country Or with Protons in a Developed Country
Authors: Taddei PJ , Khater N , Youssef B , Jalbout W , Howell RM , Mahajan A , Zhang R , Mirkovic D , Giebeler A , Geara FB , Newhauser WD
Published: July 2013

Purpose: Childhood cancer survivors who were treated with craniospinal irradiation (CSI) have a high risk of radiogenic late effects, for example second malignant neoplasms (SMNs). These effects can occur inside or outside of the therapeutic fields. Proton therapy, which is unavailable in developing countries, may offer the possibility to reduce the radiation dose in normal tissues and thereby reducing the risk of late effects. We quantified the equivalent dose in organs at risk for SMNs for 9 children ages 2 to 14 years who received proton CSI in a developed country and the doses they would have received from photon CSI in a developing country. Methods: For each child, 23.4‐Gy treatment plans were created according the standards of care of leading cancer centers in a developed country (proton CSI) and in a developing country (photon CSI). For each patient and clinic, equivalent dose was determined throughout the patients' bodies. In‐field dose was calculated using treatment planning systems of our clinics. Out‐of‐field dose was calculated using Monte Carlo simulations for proton CSI and applying a measurement‐based model for photon CSI. Mean equivalent dose was determined in organs at risk of SMNs‐‐red bone marrow, bladder, breasts, liver, lungs, ovaries, prostate, stomach, uterus, colon, skin, and remainder tissues. Results: Mean organ equivalent doses averaged over 9 all patients were less in proton CSI than in photon CSI in all organs and tissues except skin. We observed minor (<30%) reductions in equivalent dose in the lungs, red bone marrow, and remainder tissues and larger (>85%) reductions in all other organs. Conclusion: Equivalent dose was reduced for children receiving CSI with proton beams rather than photon beams. It may be possible to reduce the risk of radiogenic SMNs for children in developing countries needing CSI if proton therapy is made available to them. Fogarty International Center, National Institutes of Health, K01‐TW008409; National Cancer Institute, National Institutes of Health, R01‐CA131463‐01A1; Northern Illinois University through a subcontract of Department of Defense W81XWH‐08‐1‐0205; We do not have any conflicts of interest
SU‐E‐T‐336: Geometric Optimizations of a Directional High Dose Rate Brachytherapy Source Using Monte Carlo
Authors: Heredia A , Henderson D , Thomadsen B
Published: July 2013

Purpose: The purpose of this work is to present results from geometric optimizations of a directional high dose rate brachytherapy (d‐HDR) source using MCNP5. Three brachytherapy source designs are presented here; 1)cylindrical d‐HDR (Cyl.1), 2) D‐shaped d‐HDR version 1 (D.1), and 3) D‐shaped d‐HDR version 2 (D.2). Methods: The sources were modeled using MCNP5 version 1.51. Tally volumes (1mm3) were placed around the seed at radii ranging from 0.25–100cm and fifty polar and azimuthal angles, in 7.2° increments ranging from 0°–352.8°. A cylindrical mesh superimposed over the simulated geometry was also employed. The d‐HDR active volumes consisted of a palladium‐103 (Pd‐103) pellet ranging from 0.105–0.150 cm in diameter, with a 0.003 cm thick osmium foil for shielding, within a.001 cm titanium encapsulated volume. Results: The dose rate constant, ?, for the Cyl.1, D.1, and D.2 was 0.686 cGy h‐1 U‐1, 0.671 cGy h‐1 U‐1, and 0.657 cGy h‐1 U‐1, respectively. The optimized D.2 design showed an improvement over the Cyl.1 and D.1, having a flatter dose profile for a 165° span, where the relative dose at the radial distance was max. The Cyl.1 design had a rounder dose profile showing only a 60° plateau section, resulting in a lower dose conformality. The D.1 design showed the presence of two significant horns at 120° and 225°. This was attributed to the self attenuation within the active volume, resulting in a lower relative dose along the widest dimension. Conclusion: Geometric optimizations of a new directional high dose rate source have been presented. The results show an improved geometry in the D‐shaped d‐HDR version 2 (D.2) compared to both Cyl.1 and D.1 seed designs. The D.2 seed has the potential to improve dose conformality and current patient outcomes, having flexibility for use in both intracavitary and interstitial brachytherapy applications.