bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐FF‐T‐404: Dosimetric Effect of a Small Air Cavity for Clinical Electron Beams: A Monte Carlo Study
Authors: Chow J , Grigorov G
Published: April 2010

Purpose: This study investigated dosimetric changes in a water phantom when a small air cavity was presented at the central axis of a clinical electron beam. 6, 9 and 16 MeV electron beams with a 10×10 cm2 applicator and cutout produced by a Varian 21EX linear accelerator were used. Methods and Materials: Percentage depth doses (PDDs) for different depths (0.5–7 cm), thicknesses (2–10 mm) and widths (1–5 cm) of air cavities were calculated using Monte Carlo simulations (EGSnrc code) validated by film measurements. Results: When the depth or thickness of the air cavity was changed, the PDD below the cavity was shifted with a distance equal to the thickness of cavity. However, when the width of the air cavity was changed, both the PDD and its slope within and below the cavity were changed. A larger width of the air cavity resulted in a shallower PDD within the cavity. The dependence of the depth dose on the width of the air cavity is due to the contribution of the electron side‐scattering in the water surrounding the cavity. Neglecting an air cavity of 1 cm thickness in the build up region of a 6 MeV electron beam resulted in a delivered dose 10%–12% larger than the original prescription. Delivered doses 3% and 6% higher than the prescribed dose were observed when doses were prescribed at R80 for a 16 MeV electron beam. These results were obtained by neglecting air cavities with thicknesses equal to 2 and 4 mm at a depth of 5 cm, respectively. Conclusions: The dosimetry data in this study can help radiotherapy staff estimate and predict the deviation between the prescribed and delivered dose, when inevitablely neglecting the small air cavity or inhomogeneous correction in the dose calculation and output measurement.
SU‐FF‐T‐408: Tissue Inhomogeneities in Monte Carlo Treatment Planning for Proton Therapy
Authors: Beaulieu L , Bazalova M , Furstoss C , Verhaegen F
Published: April 2010

Purpose: To investigate the effect of tissue segmentation and metal streaking artifacts for Monte Carlo (MC) dose calculations in proton therapy. Method and Materials: CT images of a phantom with 9 tissue equivalent inserts were segmented into material and mass density maps using the conventional single‐energy CT and a more accurate dual‐energy (DECT) material extraction. MC dose calculations for a broad 200 MeV proton beam were performed in the exact geometry and in the single‐energy and dual‐energy CT geometries in the MCNPX code. The dose calculation errors for the two tissue segmentation approaches were quantified. MC dose calculations were performed for a 147 MeV proton beam treatment plan of a patient with metal bilateral hip prostheses based on water‐only geometry, on original CT images with severe streaking artifacts and based on artifact corrected images. The effect of the artifacts and their correction on MC dose distribution was evaluated. Results: The materials of three inserts were incorrectly assigned using the conventional approach. The conventional tissue segmentation yielded dose calculation errors below 2%. In both the single‐energy CT and DECT geometry, there was a 0.7 cm shift in the position of the Bragg peak suggesting that density assignment is more important than correct tissue segmentation in proton beam MC dose calculations. The patient dose calculations using CT images with streaking artifacts showed large statistical errors in the artifact corrupted voxels and differences up to 1.5 cm in the 20% and 30% isodose lines due to the artifacts. Conclusions: The shift in the Bragg peak demonstrates the need for careful mass density assignment in proton beam MC dose calculations. The use of DECT tissue segmentation might therefore have only a small added benefit. The patient study shows that a metal artifact correction is necessary for patients with bilateral hip prostheses.
SU‐FF‐T‐420: A Track Repeating Algorithm for Carbon Therapy Dose Calculation
Authors: Veltchev I , Li J , Fan J , Ma C
Published: April 2010

Purpose: In radiation therapy, the use of heavy charged particles offers numerous advantages (narrow Bragg peak and sharp penumbra) over electron and X‐ray beams. Conventional dose algorithms are fast but less accurate for heterogeneous patient anatomy for small fields and beam scanning. Accurate dose calculations based Monte Carlo simulations are time consuming. Our goal is to develop a fast Monte Carlo dose calculation algorithm using a track repeating method for carbon therapy treatment planning and dose verification. Method and Materials: Using the GEANT 4 Monte Carlo code we recorded the tracks of mono‐energetic (300MeV/nuclon) carbon ions in a homogeneous water phantom. For every carbon history, the incident carbon ion and all secondary particles are transported in discrete steps and all parameters for each step are recorded in a database. A program is developed to adjust the step length and energy deposition in different materials along the particle path in a heterogeneous phantom. Based on the energy and angle of an incident carbon either the whole history or parts of tracks will be repeated with proper angular rotation. Results: We first demonstrated the applicability of the track repeating method for mono‐energetic carbon beams (100–300 MeV/nucleon) by comparing the calculated dose distributions in homogeneous and heterogeneous phantoms with those simulated by two established Monte Carlo codes (GEANT 4 and FLUKA). As a second step we confirmed that the Bragg peak shift and energy deposition changes in bone and soft tissue are accurately reproduced. As a final test we applied the algorithm to calculate the dose distribution in patient geometry built from CT data. Conclusion: Our track repeating technique for carbon ions is extremely efficient (11‐100 times faster than FLUKA) opening the possibility for both fast and clinically accurate dose calculations for advanced carbon therapy using beam scanning and intensity modulation.
SU‐FF‐T‐421: Acceleration of Photon Monte Carlo Dose Calculation Using Multi‐Resolution Voxel Transport Geometry
Authors: Sheu R , Chui C , Yang J , Jackson A
Published: April 2010

Purpose: A multi‐resolution voxel geometry transport scheme was introduced to improve the efficiency of Monte Carlo dose calculation for photon beams. Method and Materials: Dual resolution voxel geometries were established with the coarse voxel size defined as a multiple of the finest voxel dimension. For each sub‐step of secondary photons, if the step size is greater than the nearest coarse voxel boundary, the particle is transported in coarse resolution voxel geometry. When the residual step size is less than the nearest coarse voxel boundary, the transport of the particle is switched back to the fine resolution voxel geometry. Electrons are always transported in fine resolution geometry. Timing was compared with the full Monte Carlo carried out on the fine voxel geometry, using fine voxel size of 4, 2, 1 mm and different coarse voxel size up to 2 cm. This multi‐resolution scheme was implemented in our in‐house photon Monte Carlo code (pMC2) and was assessed for accuracy using three heterogeneous phantom test cases. Results: For the 4‐mm, 2‐mm and 1‐mm voxel resolutions, the calculation time for the same particle histories can be decreased by 14%, 26%, and 42% respectively by using the dual resolution voxel transport geometry (for coarse voxel dimension of 2 cm). For the inhomogeneous test problems, the multi‐resolution transport scheme agrees with the analog Monte Carlo dose calculation within 1%, even when there is high density material such as iron involved. The inter‐resolution transport geometry swapping over head is negligible. Conclusion: This multi‐resolution transport scheme proposed in this study is more efficient than regular photon Monte Carlo dose calculation. The efficiency gain is more significant when the finer calculation resolution is required. This acceleration scheme doesn't affect the accuracy and can be applied in any Monte Carlo dose calculation system.
SU‐FF‐T‐425: The Causes of the Lateral Envelop of Low Doses in Scanning Proton Beamlets
Authors: Sawakuchi G , Tit U , Ciangaru G , Mirkovic D , Zhu X , Mohan R
Published: April 2010

Purpose: A known phenomenon in scanned proton beams is a low dose envelope, namely halo dose, which laterally extends far away from the beamlet axis. This effect leads to a dependence of the total delivered dose on the size of the target volume hence must be considered in dose calculation algorithms used by treatment planning systems (TPSs). In this work we investigated the causes of the halo dose using the Monte Carlo (MC) technique. Method and Materials: A validated MC model of the Proton Therapy Center, Houston (PTCH) scanning nozzle was used to investigate the contribution to the halo dose due to: i) secondary particles created in phantom; and ii) particles scattered in the beam line components. Results: For high energy beams, secondary particles produced by nuclear interactions (NIs) in the water phantom are the major contributors to the halo dose. For low energy beams, the halo dose is dictated by particles undergoing multiple Coulomb scattering in the beam line components. Conclusion: The halo dose is caused by two major effects, which depend on the beam energy and beam line components. On one hand, secondary particles produced in the water phantom are the major cause of the halo dose for high beam energies. On the other hand, particles scattered in the beam line components are the major cause of the halo dose for low beam energies. In the latter situation the halo dose depends directly on design features of the beam line. This is an important fact to consider because this effect is beam line specific and adds a challenging problem to analytical dose models used by TPSs. Furthermore, this work suggests that features in the design of the beam line can minimize the halo dose for low proton beam energies.
SU‐FF‐T‐435: Dosimetry Performance Comparison of Proton IMPT Versus Photon IMRT for Ocular Tumors Using Monte Carlo Simulation and Pinnacle3® TPS
Authors: Massingill B , Liu Y , Diaz A , Esquivel C , Papanikolaou N
Published: April 2010

Purpose: We aim to provide accurate proton dose calculations for ocular tumors and adjacent critical organs using intensity modulated proton therapy (IMPT) using a human anatomy‐based Monte Carlo model. Dose is simulated using Monte Carlo code MCNPX and compared to standard photon IMRT planning using Pinnacle3® TPS. Method and Materials: The human anatomy model was adapted from the Visible Human Project from the National Library in Medicine. Sectioned images were assigned physical properties. Two independent trials delivering 90% prescription dose to 100% tumor volume were developed using IMRT and IMPT, respectively. Dose profiles for each transverse, sagittal and coronal view of the model were provided for evaluation. Both treatment plans were optimized to deliver maximum dose to the tumor and minimize dose elsewhere. The dose volume histograms for the PTV (tumor), eye, lens, optic nerve, lacrimal gland, brain, chiasm, and pituitary gland were compared between IMRT and IMPT, respectively. Results: IMPT delivered superior isodose coverage to all tissues. Comparing IMRT and IMPT, the mean dose was 4499 cGy and 4750 cGy‐Eq (PTV), 2334 cGy and 1700 cGy‐Eq (eye), 2705 cGy and 1330 cGy‐Eq (lens), 156 cGy and 181 cGy‐Eq (optic nerve), 142 cGy and 23 cGy‐Eq (lacrimal gland), 21 cGy and 0.0 cGy‐Eq (brain), 31 cGy and 0.0 cGy‐Eq (chiasm), and 43 cGy and 0.00 cGy‐Eq (pituitary gland), respectively. The PTV was well covered by 90% isodose to 100% of the tumor volume with an average % prescription dose of 99.9% and 105.6 % for IMRT and IMPT, respectively. Conclusions: IMPT provided conformal dose to the ocular tumor and significantly spared dose to critical organs compared to IMRT. The human‐anatomy dose model performs very well in dose calculation; however, further validation using additional human anatomy‐based models and more specified proton source configuration is needed for optimization purposes.
SU‐FF‐T‐438: Modeling 6 MeV Electron Beam From Medical Linear Accelerator Using Monte Carlo Simulation
Authors: Dechsupa P , Tannanonta C , Phaisangittisakul N
Published: April 2010

Purpose: To determine the initial electron beam parameters those are mean energy and its full width at half maximum of 6 MeV electron beam from Varian Clinac 2100C and to calculate output factors. Method and Materials: Measurements of the central‐axis and off‐axis dose distributions were made using diode detector in a 3D water phantom. The output factors were measured in a 2D water phantom using ROOS chamber. In simulation, the EGSnrc code was used to simulate the linac treatment head and calculated dose distribution. The parameters selection procedure was to adjusting the initial electron beam parameter until the simulated data agree with measured data. After the appropriate initial beam parameters are achieved, these parameters were used to calculated output factors and compared to the measured data. Results: The appropriate mean energy and its full width at half maximum are 7.2 MeV and 4.0 mm. For the output factors, it was found that the difference between the measured and the calculated data were within ±2% in most of the investigated field sizes except for the field sizes of 6×6 and 9.5×4.2 cm2. The percent difference for field sizes 6×6 and 9.5×4.2 cm2 are 2.05% and 2.68% respectively. The error may be due to the inaccuracy in model of scattering foil and cutout. Conclusions: The results have shown that the Monte Carlo simulation can be used to calculate electron beam data accurately at the 2% level in the most cases for a limited set of data (energy, field size, SSD). In order to apply this model to fully calculated dose distribution for electron mode, further investigation is required in a wide range of configurations such as high energy and irregular field size.
SU‐FF‐T‐445: Changes in Clinical Practice Due to Electron Monte Carlo Implementation
Authors: Sansourekidou P
Published: April 2010

Purpose: To identify changes in target coverage when clinical practice advances from the GGPB algorithm to the electron Monte Carlo algorithm in Eclipse. Method and Materials: Sixteen patients were planned with electron Monte Carlo. Prescriptions were set to cover percentage of target volume, as clinically acceptable by the physicians, on a case by case basis. Dose volume histogram coverages were noted for PTV and CTV, where applicable. MUs were recorded. The same plan was run with GGPB. Prescription point and line was set to achieve similar dose volume histograms to the electron Monte Carlo plans. Dose volume histogram coverages were noted for PTV and CTV, where applicable. MUs were recorded. The MU derived form the GGPB model were used to calculate an “inverse electron Monte Carlo” plan, namely a plan using the electron Monte Carlo algorithm but calculated with fixed MUs, as they were calculated from the GGPB. Dose volume histogram coverages were noted for PTV and CTV, where applicable. MUs were recorded. Results: The inverse electron Monte Carlo plans give a representative image of clinical practice before the electron Monte Carlo clinical implementation. The overall target coverage was significantly less than previously thought while using the GGPB. This trend increases with the increase in angle of incidence and is more prominent for angles > 15degrees. Further study is necessary in order to evaluate the effects of inhomogeneity. Conclusion: The use of electron Monte Carlo leads to increasingly better tumor coverage. The MUs used are also increasing in the range of 4%–13%, in order to achieve the true desired coverage.
SU‐FF‐T‐447: A Monte Carlo Study for Characterization of Solid Brass Compensators Used for IMRT
Authors: Zhai Y , Stathakis S , Jin X , Papanikolaou N
Published: April 2010

Purpose: A Monte Carlo study for characterization of solid brass compensators used for IMRT is performed, to investigate their dosimetric properties. Method and Materials: A group various solid brass compensators with different shapes were constructed and simulated by Monte Carlo code EGSnrc (BEAMnrc/DOSXYZnrc). A Varian 2100Ex linear accelerator was commissioned prior to the simulation of the compensators. The simulation included five solid slab brass compensators with thicknesses ranging from 1 to 7cm and solid brass compensators of varying thickness within the field. The same fluences as the ones produced by the compensators were created using Varian Millennium MLC collimator. Phase‐space files were scored after the compensators and after the MLC collimator. The phase space files were used as sources in DOSXYZnrc and the dose was calculated in a solid 30×30×30cm3 water phantom. Dose distribution profiles and PDD were obtained from the dose simulations. Particle fluence, energy fluence, energy spectrum and angular distributions were obtained from the phase space files. Results: Dosimetric data analysis of the PDDs and profiles showed that beam hardening does not have a significant effect on the PDD as it does on the energy spectrum. The PDDs are more penetrating than their open‐field counterparts. Comparing results from MLC‐based IMRT fields and compensators, we find them to be consistently dosimetrically equivalent for all the fields we studied. Conclusion: This study shows that the compensator is an inexpensive and reliable dose delivery device for IMRT and produces an optimized dose profile similar to the ones obtained with the MLC based IMRT delivery.

Research sponsored by .decimal Incorporation.
SU‐FF‐T‐449: A Monte Carlo Study of Stray Neutron Background Produced in Ocular Therapy
Authors: Randeniya S , Newhauser W , Koch N , Yepes P
Published: April 2010

Purpose: To study the neutron spectral fluence and neutron dose equivalent as a function of the off axis distance to isocenter in an ocular therapy beam line using the Monte Carlo technique and to compare the simulated neutron dose equivalent values with the measurements presented in X. Yan et al, Nuclear Instruments and Methods A 476, 2002. Methods and Materials: A Monte Carlo simulation of an ocular nozzle (Newhauser et al, Physics in Medicine and Biology, 2005) and a cylindrical Lucite phantom were carried out using the FLUKA radiation transport code. Mean initial kinetic energy of protons was 159 MeV. The range of the proton beam was 2.5 cm in water. The neutron track length fluencies were tallied in 8 spherical cells of air of diameter 25.4 cm. The off axis distance to the tallies from the isocenter were between 25 cm and 75 cm. The neutron track length fluencies were converted in to ambient dose equivalent using the conversion coefficient given in ICRP 74. Results: The energy weighted neutron fluence spectra demonstrated characteristic low energy evaporation peak and high energy peak. The strengths of both peaks decreased as the distance from the isocenter increased. The neutron dose equivalent values decreased as the off axis distance from the isocenter increased. At a distance of 65 cm away from the isocenter, the neutron dose equivalent value was about 50% of that of at 25 cm. The neutron dose equivalent values from this study are roughly factor of 2 higher than that of measurements from Yan et al (Reported uncertainty of the measured data is 40%). Contribution to total neutron dose equivalent from high energy neutrons is higher than that from low energy neutrons. Conclusions: A detailed study of neutron background produced in ocular proton therapy is presented.
SU‐FF‐T‐453: An Electronic Database for Radiation Oncology Physics Quality Assurance (DROP QA)
Authors: Jones A
Published: April 2010

Purpose: Electronic charting has become a standard of care in the Radiation Oncology community. Electronic records for quality assurance however, are not commonly available. Most clinics rely on either paper records or customized spreadsheets for quality assurance and compliance. Any changes in the QA program need to be made across several different areas (printouts, spreadsheets, institutions) increasing the chances of mistakes. By creating a database which includes all sites and equipment, our physicists make efficient use of combined resources and time in completing the required quality assurance tests. Method and Materials: The Database for Radiation Oncology Physics Quality Assurance (DROP QA) has been developed and implemented in our system (3 sites, 6 linacs, 2 HDR). The database is located on the network making it available at any computer in the system. Each clinical site is defined with their linacs and/or HDR. The database is adaptable to any linac and has all of the TG‐40 recommended tests included. HDR tests as required by state and NRC regulations are also included. Chambers and electrometers can be used at any site and in any combination. Direct communication with the MAX 4000 electrometer (Standard Imaging, Madison, WI) and the RMD‐200 remote motor drive system (CNMC Inc, Nashville, TN) are built into the database. Results: Quality assurance data for linacs and HDR units are readily available from any computer in the health system without the need to locate printed records. QA procedures are done rapidly with the built in communication to electrometers and depth dose apparatus. Machine outputs for all energies can be done without reentering the room. Conclusions: DROP QA is an efficient program to centralize and standardize QA within a health system. Future versions will increase efficiency by including automated tests (table, gantry, collimator, light field, MLC) linked directly to the database.
SU‐FF‐T‐464: Field in Filed Technique for Total Body Irradiation
Authors: Ozawa S , Miura K , Furuya T , Kawashima M , Toramatsu C , Sugimoto S , Kurokawa C , Karasawa K
Published: April 2010

Purpose: To evaluate a technique for total body irradiation (TBI) developed and adopted in our institution. Method and Materials: This technique has left and right lateral opposing field. The patient lies on the couch made by Stylofoam with legs semi‐collapsed. The arms are folded and positioned on the chest. Three types of fields are used for this technique, one whole body open field and 2 subfields. One subfield covers from chest to pelvis, and another subfield covers pelvis part. MLCs are only used for the former subfield to cover lung. The source to axis distance (SAD) is set to be 470 cm. The dose rate at the 470 cm SAD of three locations (head, abdomen, and pelvis) had measured directly by Farmer chamber with varying the thickness of solid water in advance. These measurements were performed for the following three reference points in the body, head, abdomen, and pelvis. This procedure enables us to calculate the value of cGy/MU at 470 cm SAD with any depth beforehand. We have implemented this technique to two patients. Both are prescribed 3Gy × 4 fx (BID) = 12 Gy. To evaluate the dose uniformity and to crosscheck the MU number calculated by the above method, Eclipse Ver. 6.5 with AAA 7.5.18 was used to calculate the dose distribution in the patient body. Results: Average dose at the midline was 11.99 ± 0.84 Gy, error shows 1 standard deviation. The MU difference between MU calculation and Eclipse was less than 4 %. Both cases has mean lung dose of 20% less than the prescription. Conclusion: It was found that reliable MU and acceptable dose distribution is able to be achieved without any special TBI devices or techniques, such as compensators on the gantry head or couch movement.
SU‐FF‐T‐470: Head Leakage, Collimator Scatter, and Patient Scatter Contributions to Out‐Of‐Field Dose
Authors: Kry S , Howell R , Stovall M
Published: April 2010

Purpose: Head leakage, collimator scatter, and patient scatter all contribute to dose outside of the treatment field during radiation therapy, which may lead to sequelae such as second cancers. In order to minimize out‐of‐field dose, it is essential to quantify the sources of this undesired radiation, particularly in the era of evolving radiation therapy. Method and Materials: The out‐of‐field dose was calculated with a previously benchmarked model of a Varian 2100 linac that was equipped with a 120 leaf MLC and was developed in MCNPX. The total out‐of‐field dose was calculated as a function of distance from the field edge for different field sizes, treatment energy, and linac configurations. In particular, the impact of removing the MLC, removing the flattening filter, and modulating the treatment field (IMRT) were evaluated. For each field and linac configuration, the head leakage, collimator scatter, and patient scatter components were resolved by repeating simulations but eliminating particles either leaving the MLC opening (thereby isolating for head leakage), or entering the phantom within the primary field (thereby isolating for head leakage plus collimator scatter). Results: In general, patient scatter dominated within ∼20 cm of the treatment field, while head leakage dominated at distances beyond ∼20 cm from the field edge. Collimator scatter typically made up 20% of the out‐of‐field dose, regardless of distance from the field edge. Removal of the MLC increased head leakage, while removal of the flattening filter decreased head leakage and collimator scatter, but increased patient scatter. Field modulation increased head leakage and collimator scatter, while patient scatter was unchanged. Conclusion: Different linear accelerator configurations changed the relative importance of head leakage, collimator scatter, and patient scatter contributions to the out‐of‐field dose. These differences should be considered when evaluating the out‐of‐field dose and techniques to reduce the out‐of‐field dose.
SU‐FF‐T‐471: Incident Learning in Radiation Therapy: A Tale of Two Cities
Authors: Clark B , Ploquin J , Brown R , Gackle M , Dunscombe P
Published: April 2010

Purpose: To compare experience with a comprehensive incident learning system implemented in two radiation treatment programs and assess utility in reducing the probability of repeat adverse occurrences and improving patient safety. Method and Materials: An incident learning system specifically tailored to a radiation therapy program and based on published principles was implemented in two large academic cancer centers. In the adopted system, every incident, whether or not there is a resulting direct impact on patient treatments, is recorded, investigated to determine basic causes and strategies developed to correct system weaknesses. The two centers are closely matched in size with both centers being tertiary comprehensive clinical and academic centers and both having the same number of treatment units. Incidents are categorized into one of 5 types: clinical, operational, occupational, environmental and security/other. Four levels of severity are defined — critical, major, serious and minor. Results: Our analysis is based on 392 and 658 incidents reported by Centers A and B respectively. The majority of incidents in both centers were classified as clinical as distinct from operational or other categories. Both centers reported more clinical incidents during the treatment planning process than in other work domains. The distribution of incident severity shows remarkable agreement between the centers with 92% of all incidents at both centers classified as minor. Additionally, the distribution of the primary basic causes assigned to each incident also shows similarities between the two centers with 52% and 82% of the incidents reported at Centers A and B respectively assigned the same basic cause, i.e., that standards, procedures or practices were not followed, developed or adequately communicated. Conclusions: Our results indicate that an effective incident learning system implementation will strongly encourage the reporting of potential incidents as a proactive means of enhancing safety and quality.
SU‐FF‐T‐472: Quality Assurance for MR Guided Focused Ultrasound as a Multi‐Modality Platform for Cancer Therapy
Authors: Ma C , Chen L , Pollack A , Konski A , Freedman G , Buyyounouski M
Published: April 2010

Purpose: The purpose of this work is to develop an effective and efficient quality assurance (QA) program for the application of MR guided focused ultrasound (MRgFUS) as a multi‐modality platform for cancer therapy. Materials and Method: An MRgFUS system has been installed in our institution, which consists of an InSightec ExAblate 2000 high‐intensity focused ultrasound (HIFU) system and a 1.5T GE MR scanner. This system has been FDA approved for the treatment of uterine fibroids clinically and is being investigated under local IRB approval for treating bone metastases, prostate and breast cancers and the enhancement of drug delivery for gene therapy and chemotherapy. In addition to the daily, monthly and annual calibration and commissioning measurements for the MRI unit special QA procedures were developed for the HIFU system including the mechanical motion of the couch and transducer, the safety system and patient panic buttons, the functionality of the temperature mapping and treatment software, the acoustic power output and the localization of the treatment focal spot. Results: The MRgFUS system has been operational since the fall of 2006. Successful experiments have been performed on in vitro bio‐samples and in vivo animal models for pre‐clinical studies and for drug enhancement experiments. Patients with bone metastases have been treated successfully using the MRgFUS system for pain relief with a pre‐treatment QA procedure. Patients tolerated the HIFU treatment well. No skin damage was observed after treatment. The pain scale was significantly reduced within 24 hours and further reduced at later follow‐ups. Conclusions: Comprehensive QA procedures have been developed for the safe and successful operation of the MRgFUS system as a multi‐modality platform for breast surgery, bone palliation, and prostate boost in combination with radiotherapy clinically and for drug delivery enhancement investigations for gene therapy and chemotherapy using animal models.
SU‐FF‐T‐475: DICOM‐RT Data Transfer From Odyssey Treatment Planning System to Siemens Linear Accelerators Using ARIA Record and Verify Software: A Multi‐Vendor Environment
Authors: Lingampally V , Ghebremedhin A , Leeds S , Patyal B
Published: April 2010

Purpose: To interface radiotherapy equipment across three different vendor products. Methods and Materials: Our treatment planning is system Odyssey by Permedics, treatment machines are by Siemens and the software interfacing between these two is ARIA by Varian. Although all three products came with DICOM standard conformance, we encountered many problems during the commissioning of this interface. Some of the issues were inability to transfer a plan with multiple prescriptions, exporting a plan with virtual wedges or manual apertures and exporting electron beams. Most of the issues were resolved by working with the vendor of our treatment planning system. ARIA did not support Siemens MLC, because it looked for a tertiary collimation of Varian linac. Treatment planning system had to be modified to supply X1 and X2 jaw information to ARIA before MLC data could be transferred from treatment planning system to the Siemens linac through ARIA. To run IMRT software on Siemens Primus through ARIA, Primus had to be upgraded with an IM‐MAXX software. Results: The issues related to interfacing from different vendors were best handled by working with individual vendors. All vendors were willing and happy to work on solving these problems. Odyssey treatment planning system is now successfully interfaced to Siemens linear accelerators through Varian ARIA record and verify software. The DICOM RT data transfer from Odyssey treatment planning system to treatment machines through ARIA was tested and implemented for routine clinical use. Conclusions: Even though all radiotherapy equipment from different vendors is supposedly in conformance with DICOM standard, one will encounter problems while interfacing equipment from different vendors. To resolve these problems one has to work with various vendors. Extra care is needed during commissioning the interface across multiple vendors and its clinical implementation.
SU‐FF‐T‐476: Dose‐Sparing Effects of a Rectal Balloon in Proton Therapy of the Prostate
Authors: Lee D , Yoon M , Shin D , Lim Y , Kim D , Park S , Lee S , Lee J , Suh T
Published: April 2010

Purpose; The normal organ (bladder, rectum) sparing is very important for radiation therapy of the pelivis. Many people are studying with the effort for rectal and bladder spearing, however the actual circumstances to are satisfied which can not find the method. In this study, the decrease used the balloon to order the rectal dose. The aim of the study was to investigate the dose volume effects of a water‐filled rectal balloon in the rectum. Materials and Methods; We inserted the balloon(100cc water filled, 10cm length, 3cm diameter) in rectum for 10 proton therapy patients with prostate cancers. The systems were loaded with Eclipse proton planning system(Ver. 7.5) and Two sets of CT images before and after ballooning were acquired. Rectum and bladder volumes were delineated on 3‐mm‐thick CT images. A comparison between dose volume histogram(DVH) with and without balloon in rectum for proton therapy of the prostate cancers. Results; More organ and target volume changes with shape because inserted the balloon in rectum. Mean dose of rectal difference between with and without balloon was about 20%, because volume of rectum escape from a radiation area due to the balloon. Mean dose of bladder difference between with and without balloon was about 6%. Conclusion; The rectal ballon is very useful for bladder and rectal sparing with proton therapy of the prostate cancers. This research is believed to be sufficiently accurate and clinically useful.
SU‐FF‐T‐482: Extension of An Informatics Architecture to Compare and Analyze 3D Dosimetric Data
Authors: Brown W , Deasy J , Khullar D , Apte A , Thomas A , Oldham M
Published: April 2010

Purpose: Novel 3D dosimetry techniques illustrate the urgent clinical need for tools for the comparison and visualization of dose data from various dosimeters. We present results from a collaborative effort to develop clinically useful methods to view, compare, and analyze dose data from a variety of dosimeters. Method and Materials: The development of a high‐resolution 3D dosimetry system (PRESAGE™ and optical‐CT) has motivated the re‐tooling of a previously existing informatics system — the Computational Environment for Radiotherapy Research (CERR) — to enable it to compare 3D dose data. Three different types of clinical dose distributions measured/calculated in PRESAGE dosimeters, EBT Gaf‐Chromic films and the Eclipse Treatment Planning System were used in this investigation. An intuitive and clinically relevant process for the comparison of these dose distributions has been developed. All volumetric (PRESAGE and Eclipse) and planar (EBT film) dose data was linked to the DICOM data and metadata of the irradiation. This allowed all doses to be registered to the relevant CT scan and viewed in 3D in standard, easily navigable, anatomic orientations. Results: Gamma analyses, line profiles, and dose‐difference plots were generated using the CERR platform. Relevant discrepancies amongst measured and calculated doses from different dosimeters were assessed and addressed from a single open‐source software platform. Conclusions: A comprehensive and flexible tool for 3D dosimetry, plan specific QA, and research is needed. CERR, with appropriate extensions, was found to be valuable as a tool for the comparison of doses measured using various techniques. Newer developments being implemented involve the integration of more advanced film calibration functionality, the ability to calculate 3D gamma volumes, and the ability to produce a dosimetry report including relevant information for patient specific plan evaluation.
SU‐FF‐T‐484: Late Survival Post Acute Total Body Irradiation in the Rhesus Macaque With Bone Marrow Sparing
Authors: Lerma F , MacVittie T , Farese A , Wang Z , Amin P
Published: April 2010

Purpose: There are several sequelae consequent to acute high‐dose radiation exposure. The sequelae, in order of occurrence, are the acute radiation syndrome (ARS) composed of the two subsyndromes responsible for early mortality, the hematopoietic and gastrointestinal, followed by delayed effects. The delayed effects expected are pneumonitis and subsequent lung fibrosis and respiratory failure. We investigate these delayed effects in rhesus macaques surviving acute total body irradiation with bone marrow (TBI‐BM) sparing at 11.5 to 12 Gy. Method and Materials: A varian 21EX linear accelerator is used to irradiate non‐human primates (NHP) at 153 SSD using a 40 × 40 cm field size at isocenter. The irradiation takes place at approximately 80 cGy / min at midplane. The fields are in the AP and PA directions and sparing of the primates is achieved from the knee cap down. CT imaging is conducted at intervals of 30 days to evaluate the gut and lungs. Results: Three survivors are obtained from a cohort of 16 NHP undergoing TBI‐BM at 11.5–12.0 Gy, in a single exposure. CT scans are evaluated for defects in the gut and lung at 30 day intervals, showing radiographical evidence of a late GI syndrome, pleural effusion, ascites and pneumonitis. The pleural effusion and ascites are associated with pericardial irradiation. Conclusion: These result confirm that sufficient active bone marrow sparing drastically improves long term survival at doses greater than 7.5 Gy. Notably, the longest surviving NHP in this cohort has presented with ascites and pleural effusion that have led to cause of death at day 100. This result confirms an important late effect, pericardial injury as a possible cause of death in late survivors that may override other lung‐injury associated mortality.

This work supported by NIAID Contract ♯ HHSN266200500043C
SU‐FF‐T‐490: The Effect of Daily Cone Beam CT Imaging Dose On the Secondary Cancer Risk for Patients Receiving Prostate IMRT Treatments
Authors: Altunbas C , Zheng D , Weiss E , Williamson J
Published: April 2010

Purpose: The impact of daily kilovoltage cone beam CT (CBCT) imaging dose on the radiation induced cancer risk (RICR) was evaluated for patients receiving prostate IMRT treatments. Materials and Methods: Increased secondary cancer risk was modeled by employing effective dose concept described in ICRP report 103 as basis. A prostate IMRT plan was generated in the treatment planning software to calculate dose to organs within the treatment volume. Scattered and leakage dose to organs outside the treatment volume, and CBCT imaging dose were obtained from data in published literature. Both linear and nonlinear risk‐dose response models were considered to establish a relationship between RICR and absorbed dose in the therapeutic dose range. ICRP 103 tissue weighting factors were assumed to stay the constant as a function of absorbed dose. Results: We calculated the relative increase in RICR for various RICR‐dose response models. If the secondary cancer risk was assumed to be proportional to absorbed dose, the increase in RICR due to daily CBCT imaging was in the order of 5%. If the secondary cancer risk was assumed to fall off exponentially at therapeutic doses (beyond 4 Gy), RICR increased by 21%. If RICR was assumed to be constant at therapeutic doses, the increase in RICR was 13%. Finally, if only out‐of‐treatment field organs are considered for risk estimations, RICR increased only 2%. Conclusion: Based on the risk‐dose response models that we evaluated, increased secondary cancer risk due to daily CBCT imaging during prostate IMRT treatments was in the 2% to 21% range. Although such models were known to contain inherently large uncertainties, our study might be a plausible starting point to evaluate the effect of CBCT imaging dose on the secondary cancer risk for radiation therapy patients.
SU‐FF‐T‐491: Cell Survival Curve Fitting Techniques in High Dose Region for Use in Stereotactic Body Radiation Therapy (SBRT)
Authors: McKenna F , Ahmad S
Published: April 2010

Purpose: To select a cell survival curve model that is capable of fitting cell survival at high dose region used in stereotactic body radiation therapy. Materials and Methods: Data from fourteen cell lines were examined. These include a Chinese hamster cell line, a human glioblastoma cell line, two prostate cell lines and ten lung cancer cell lines. Each of these cell lines were fitted to eight different models (4 with 2 parameters and 4 with three parameters) for cell survival. These models included among others the well known linear quadratic model and the single hit multi target model; and the more recent McKenna‐Ahmad repair model, Kavanagh‐Newman model and universal survival curve model. The χ2/df of each fit was compared to determine the model most appropriate for that survival curve. Results: No single model provided the best fit for all the cell lines. For all cell lines there were models that were superior to the linear quadratic. Two recent models (McKenna‐Ahmad repair model, Kavanagh‐Newman model) provided the best fits for many cell lines. These models have low dose quadratic behavior which changes to linear behavior at high doses. The McKenna‐ Ahmad and Kavanagh‐Newman formulas for cell survival are respectively as follows:
urn:x-wiley:00942405:media:mp1989:mp1989-math-0001 Conclusion: We recommend that one of the two recent two parameter models be used for fitting cell survival curves if one is primarily interested in cell survival into or past the shoulder region of the cell survival curve.
SU‐FF‐T‐499: Quantitative Analysis of Normal Tissue Effects in the Clinic (QUANTEC): Limits and Recommendations for Use in Treatment Planning
Authors: Haken R Ten , Bentzen S , Constine L , Eisbruch A , Deasy J , Jackson A , Marks L , Yorke E
Published: April 2010

Purpose: Via a workshop and the concerted efforts of many investigators (and with support from the AAPM and ASTRO) the dose‐volume relationships for many normal tissues sites have been examined and pulled together within the QUANTEC initiative. Here the summary recommendations of those studies are critiqued by members of the QUANTEC steering committee from a “physicist/treatment planner” perspective. Method and Materials: Sixteen site‐specific articles (written by knowledgeable physicians and physicists) have been submitted for simultaneous publication. Part of each report was a review of (where available) published dose volume histogram (DVH) point metrics and normal tissue complication model (NTCP) parameters associated with complications. Each report also provided information related to the quality of the data/results and their applicability for clinical use. The QUANTEC steering committee has summarized the site‐specific results together with a critical assessment of their strengths and shortcomings. Results: All reported values are apropos to the circumstances under which they were measured (primarily 3DCRT with conventional fractionation) and should be used with caution for other treatment schemes. The reported metrics generally fall into the categories of DVH points (e.g., Vxx, the volume of the normal tissue in excess of dose level xx associated with a complication threshold) and Lyman NTCP model parameters. The quality of the data/results ranges from combined analyses among several institutions (or combined analysis of literature values) to single institution experiences. In general, the recommended parameters and limits are more differential (separating safe from unsafe domains) rather than universal (spanning a continuous range of complications). However, clinically useful summaries can be made. Conclusion: The QUANTEC effort has been largely successful in updating the available dose/volume data. However, the resulting recommendations for clinical use need to be carefully assessed and cautiously applied as the quality of these data varies. Future QUANTEC initiatives are in progress.
SU‐GG‐BRC‐04: Electronic Versus HDR Ir‐192 Brachytherapy: Organ Dose Comparisons for Breast Cancer Using a Monte Carlo Patient Phantom
Authors: Mille M , Zhang J , Xu X , Rivard M
Published: April 2010

Purpose: To quantify and compare the dose delivered to multiple organs‐at‐risk (OARs) in a female patient undergoing Xoft Axxent electronic (KVB) and high‐dose rate Ir‐192 (IBB) intracavitary balloon brachytherapy for breast cancer. Materials and Methods: A previous study has indicated that the dose to OARs such as the lungs and heart play a critical role in treatment planning. The anatomy of a female patient was represented by an adult female computational phantom which consists of over 140 organs. A balloon was inserted into a lumpectomy cavity in the left breast of the virtual patient. The Monte Carlo N‐Particle eXtended (MCNPX) code was used to simulate photon transport through the patient for hypothetical KVB and IBB scenarios. MCNPX's F6 tally was used to calculate the absorbed dose in organs distant from the treatment site. Results: In general, the KVB organ doses were more than a factor of 2 smaller than those of IBB because the low‐energy x‐rays are less penetrating. The distribution of organ doses shows a profound pattern depending on the distance, location, and organ shape. The largest doses were observed for organs such as the left lung and heart which are closest to the radiation source. For KVB, the doses received by the left lung and heart wall were 9.0% and 5.5% of that received by the planning target volume. These values were 11.0% and 11.3% for the IBB scenario. Conclusions: This paper reports, for the first time, a systematic comparison of multiple organ doses received from KVB and IBB. KVB may have safety advantages because its dose rate falls off faster than for IBB. As a previous clinical study found the target dose to be similar for these two methods, information on how healthy organs are irradiated will help decide when each modality is appropriate.
SU‐GG‐BRC‐05: The Role of Hypoxia in Radiation Treatment Planning. A Simulation Study
Authors: Axente M , Lin P , Pugachev A
Published: April 2010

Purpose: To assess the importance of hypoxia imaging for radiation treatment planning by evaluation of the effectiveness of modulated radiation treatments targeting hypoxia with increased doses. Method and Materials: Starting with a two‐dimensional diffusion model of tissue oxygenation, a planar tumor model was developed to simulate chronic and acute hypoxia as well as oxygenation/reoxygenation effects on the microscopic scale. Tumor cell radiation response was evaluated using linear quadratic model taking into account individual cell oxygenation levels. Cell repopulation/tumor shrinkage was not considered, as to represent a slow‐growing tumor. Using this model, we evaluated the effectiveness of intensity modulated radiation therapy treatments targeting hypoxia with increased radiation doses. We compared different approaches to targeting hypoxia, including fixed dose modulation based on the pre‐treatment imaging of hypoxia and adaptive dose modulation based on interfraction imaging of hypoxia. Furthermore, to study the importance of hypoxia imaging resolution we compared two scenarios: 1. microscopic, where cell‐by‐cell imaging of hypoxia and dose delivery is possible, 2. macroscopic, where both imaging and irradiation can be conducted with 1mm resolution. Results: For a total tumor dose of 30Gy, the adaptive hypoxia‐targeting therapy provided the best tumor control for the microscopic scenario with compared to for the treatment with uniform dose of 2Gy per fraction. However, for a more realistic macroscopic scenario, the finite resolution of hypoxia imaging and dose delivery significantly reduced the therapeutic advantage of adaptive hypoxia targeted therapy resulting in compared to 7.09⋅10−5 for the uniform dose treatment. Conclusion: We have demonstrated that the adaptive dose modulation based on oxygenation map acquired before each fraction does results in slightly better tumor control compared to uniform dose delivery. However, the tumor control improvement is yet to be proven significant enough to justify the clinical implementation of hypoxia‐targeting dose modulation.