bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐FF‐T‐156: Multi‐Institutional Retrospective Analysis of IMRT QA Measurements
Authors: Sontag M , Chen X , Qin L , Ottino F , Chen H , Li F , Loper A , Komanduri K , Lalonde R , Yue N , Heron D , Huq M
Published: June 2005

Purpose: To review IMRT QA measurements from several of the 50+ institutions for which we provide IMRT treatment plans and determine if institutional, anatomic site, or measurement biases exist. Method and Materials: For each patient receiving IMRT, the treatment plan is delivered to a solid water phantom and the dose measured using a small volume ion chamber and with a single EDR film placed 1 cm above the chamber plane. Of the almost 3000 IMRT treatment plans calculated and delivered in 2004, more than 1000 random, de‐identified plans were reviewed. Ratios of chamber/calculated and film‐center/calculated doses were tabulated for six anatomic sites (breast, prostate, pelvis, head & neck, brain, and other). Film dose distributions were compared to calculations using one of several commercially available QA packages. Results: The institutions with the best results had average errors of less than ±0.5% (i.e. randomly distributed about zero) with standard deviations of 1.25–1.50%. A few centers had average errors and standard deviations approaching 3%, indicating a bias in which a systematic dose measurement error was found. Agreement between chamber and film center dose was also institution specific with the best results found for those centers that had the lowest errors compared to calculation. One institution had excellent agreement between chamber and calculation (−0.2±1.7%), but 2–3% lower film dose. Although exceptions were found, little variation in the agreement between chamber measurement and calculation occurred as a function of anatomical site. Conclusion: Since all treatment plans were calculated in one central location and many centers had excellent agreement between measurement and calculation, it is likely that the higher errors were due to measurement technique rather than errors in the dose calculation. Error was not anatomic site dependent possibly due to the purposeful placement of the ion chamber in a region of relatively uniform dose.
SU‐FF‐T‐159: Patient Quality Assurance Analysis for Tomotherapy
Authors: Papanikolaou N. , Shi C.Y. , Yan Y. , Weng X.
Published: June 2005

Purpose: IMRT plans developed for conventional Linac equipped with dynamic MLC can be independently verified using a number of commercially available software packages. For the HiArt TomoTherapy unit however, the only dose verification mechanism is by measurement. The purpose of this investigation is to analyze the patient specific quality assurance results for the HiArt TomoTherapy intensity modulated radiotherapy treatment planning and delivery system in our clinic. Method and Materials: We have developed a systematic patient specific IMRT QA program that was implemented in April of 2004. Once a QA plan is calculated, the dose to a phantom is measured using ion chamber and film. The ion chamber is placed 5 mm below the film which in turn is placed in the equator of a cylindrical solid water phantom. After the plan is delivered to the phantom, the point dose is recorded and the film is processed. Film calibration is performed daily using an in‐house developed protocol and software tool. Dosimetric analysis is performed after the film and planar dose are co‐registered in the TomoTherapy planning station. In total, 63 patients were analyzed. Results: Dosimetric analysis was performed based on both film and ion chamber measurements. The median and mode discrepancy is below 2% for the point measurements. Similar results are found for the film analysis which provides not only absolute dosimetry but also isodose distribution and profile comparison between measured and calculated planar dose distributions. The plane and points of calculation can introduce small errors in the analysis. Conclusion: A comprehensive patient QA program has been developed and the results of 63 patients are analyzed in this paper. Given the novel approach of TomoTherapy towards IMRT, it is important to see that for the majority of the patients the deviation between planned and delivered doses is less than 2%.
SU‐FF‐T‐161: Practical Gap‐Width Threshold for MLC Quality Assurance for IMRT
Authors: Burmeister J , McDermott P , Desai P
Published: June 2005

Purpose: A standard IMRT quality assurance test for Multi Leaf Collimator (MLC) leaf position accuracy is the Memorial Sloan‐Kettering (MSK) leaf test. This test involves inspecting the widths of five 1 mm wide fields delivered 2 cm apart. A maximum error tolerance of 0.2 mm in the gap‐width between sets of opposing leaves is recommended. In a preliminary informal visual test performed with an independent observer, the observer detected all deliberately introduced errors greater than or equal to 0.5 mm, but not all 0.2 mm errors. Method and Materials: We investigated the use of the MSK leaf test on a Varian Clinac 2300C/D and Clinac 2300EX, with Mark I (52 leaf) and Millennium (120 leaf) MLCs, respectively. Kodak XV film was irradiated with 6 MV photons at an SSD of 100 cm, using 1000 monitor units for the delivery of the five segments. The film was scanned using a Vidar VXR‐16DP scanner, and subsequently analyzed with the RIT113 Version4 software. The RIT software recommends using a 3×3 median filter to remove background noise, which effectively reduces the image resolution. Since the smallest baseline resolution of the scanner is 0.089 mm, a 0.2mm error will be difficult to observe after a 3×3 filtration. Separate films were irradiated under the same conditions and scanned to determine if the scanner software combination was consistent in assessment of the magnitude of errors in the gap‐width. Results: The reproducibility of leaf positions on multiple films was found to be within one pixel. However, not all artificially introduced errors that were visually observable were detected by this software technique. Conclusion: It may not be feasible to reliably measure gap‐width errors of 0.2 mm, either by eye or by quantitative analysis using the technique presented here.
SU‐FF‐T‐168: The Evaluation of Several Commercial IMRT Treatment Planning Systems Heterogeneity Dose Calculation Algorithms Using An Anthropomorphic Thorax Phantom
Authors: Davidson S , Followill D , Ibbott G , Prado K
Published: June 2005

Purpose: To measure the accuracy of heterogeneity dose calculation algorithms from several commercial IMRT treatment planning systems using an anthropomorphic thorax phantom. Method and Materials: Four planning trials were designed to characterize heterogeneity dose calculation algorithms. The four trials were 1) evaluation of ADAC Pinnacle's conventional 3D algorithm as a baseline, 2) evaluation of Pinnacle IMRT, 3) evaluation of Corvus IMRT and 4) evaluation of a hybrid plan consisting of the Pinnacle dose calculation optimized by Corvus. The accuracy of the algorithms was determined by delivering the clinically relevant treatment plans to the Radiological Physics Center's anthropomorphic thorax phantom. The phantom contained radiochromic film in the three major planes and TLDs in the center of the tumor target. The film data were normalized to the TLD readings. Point doses and planar dose distributions were extracted from the treatment planning system and compared to TLD and film measurements. Dose profiles and planar dose distributions were compared point by point using criteria of ±5% and 3mm distance to agreement. Results: Preliminary results for Pinnacle reveal TLD‐to‐calculation dose ratios of 0.994 and 0.990 for 3D and IMRT, respectively. Points on dose profiles through the target and adjacent lung met the agreement criteria 96% and 84% of the time for the respective treatment techniques. The 3D TPS planar dose distribution agreed with measurements to within the criteria at 74% of the points, while the IMRT TPS agreed at 73% of the points. Conclusion: The Pinnacle conventional and IMRT heterogeneous dose calculation algorithms agree well with measured data in an anthropomorphic thorax phantom.
SU‐FF‐T‐172: Verification of Whole‐Body Dosimetry in An IMRT Treatment Planning System
Authors: Wuu C , Elliston C , Xu Y , Brenner D
Published: June 2005

Purpose: IMRT has been widely used in radiation therapy, since this technique shows potential for further improving the therapeutic ratio and reducing complications. On the other hand, it has been suggested that IMRT presents a potential impact on the induction of second malignancies, because it can result in a higher whole‐body dose due to leakage radiation. In the routine treatment planning process, complete information on the whole‐body dose‐volume histogram is not available due to the limited patient body volume imaged in the CT treatment planning process. In addition, for IMRT, larger volumes of normal tissues are being exposed to low doses, and the dosimetric uncertainties of a treatment planning system at these doses are relatively large. In this study, whole‐body dosimetry calculated from the Eclipse‐Helios planning system was verified using a whole‐body anthropomorphic phantom and MOSFET detectors, as well as polymer gels. Method and Materials: The “ATOM” whole‐body anthropomorphic phantom was CT‐ scanned into the Eclipse‐Helios system. An IMRT prostate plan was designed for the ATOM phantom. Each MOSFET detector was calibrated at various angles based on ion chamber dosimetry. The MOSFET detectors were precisely placed in relocatable dosimeter positions corresponding to various internal organs, allowing point‐dose measurements and comparison. BANG® polymer gel, prepared in a cylindrical container, was placed at the phantom head position to measure the 3D dose distribution. The DVH in the gel cylinder, analyzed with an optical CT scanner, was compared with that from the planning system. Results: Preliminary results show that the agreement between the MOSFET measurements and the calculated results is within 5% for points within the target. At low‐dose regions (0.1–60%), discrepancies are larger but reasonable. DVH comparison between gels and the treatment planning will be presented. Conclusion: Anthropomorphic phantom with MOSFET detectors and polymer gels can provide whole‐body dosimetry verification for IMRT.
SU‐FF‐T‐174: A New Device for the Verification of Temporal Function of the 4DCT and Gating Delivery System
Authors: Chen H , Brandner E , Wu A , Komanduri K , Shou Z
Published: June 2005

Purpose: A quality assurance device was developed for 4DCT (GE Medical System, Waukesha, Wisconsin) and the Real‐Time Position Management Respiratory Gating System (Varian Medical Systems, Palo Alto, CA). It verifies the temporal‐phase function of the 4DCT and the gated delivery function of the Linac. Method and Materials: The QA device is composed of a mobile phantom, static phantom, acrylic lobe, AC motor, power transformer and transmission mechanism. There are eight radio‐opaque lines embedded in the static phantom, which are used as reference indicators. A “Z” shape radio‐opaque marker is fixed on the top of the mobile. This phantom moves periodically with a maximum displacement of 3 cm in a horizontal direction. It was scanned under our 4DCT at a period of 5 seconds. The collected images were divided into 10 groups representing 10 phases of the moving cycle. The digitally reconstructed radiograph of each phase was generated for the verification of the temporal‐phase function of the 4DCT. To verify the gated delivery function of the Linac, a radiographic film was attached to the surface of the mobile phantom and a 0.5 cm by 10 cm X‐ray field was used to expose the film at certain phases. The expected position of 0% phase was marked by punching 2 small holes on the film. Results: The “Z” mark was correctly shown and aligned with the reference lines at each phase. The film exposed under the Linac has shown that the radiation had been delivered to the correct position. Conclusion: A reliable quality assurance device for 4DCT and respiratory gating system is necessary to ensure that the radiation dose is accurately delivered to the patient's target volume. This QA device is effective and convenient for checking temporal‐phase function on the 4DCT and RPM gating system.
SU‐FF‐T‐186: Commissioning of Tissue Inhomogeneity Correction of Eclipse Radiation Treatment Planning System Using a Lung Phantom
Authors: Yoo S , Yin F , Ajlouni M , Movsas B
Published: June 2005

Purpose: It has been noted that dosimetric difference due to tissue inhomogeneity is significant for a lung patient. If there is no tissue inhomogeneity correction (IC) made, the treatment plan could mislead treatment. Commercial radiation treatment planning (RTP) systems have the capability to include tissue IC. To utilize IC, each correction method should be reviewed and verified in advance. This study presents the commissioning of tissue IC in the Eclipse RTP system for three methods; Batho power law (Batho), Modified batho (Mo‐Batho), and Equivalent TAR (E‐TAR). Method and Materials: Treatment plans were mapped onto CT images of a lung phantom. Dose was calculated once without IC and three times with different correction methods each time. Doses were measured at three different locations, one inside of the lung in the phantom, one in the body in between lungs, and the last one in the bone. Results: The results demonstrate that the calculated without tissue IC could be significantly different from the measured dose in the treatment room. This difference varies depending on the extent to which each radiation field passes through inhomogeneous tissues. This study proves that the currently available correction methods reduce the error made due to tissue inhomogeneity. The calculated dose without IC was 5 – 10 % from the measured dose at the point inside of the lung or in between the lungs. The difference ranges 2 – 3 % using Batho, 1 – 3 % using Mo‐Batho, and 0 – 4% using E‐TAR. However, the calculated dose to the point inside of the bone was about 2 – 5 % different from the measured dose regardless of the use of IC. Conclusion: This study overall favors the use of inhomogeneity correction for treatment plans. Among all correction methods in Eclipse, Modified batho is recommended based on this study.
SU‐FF‐T‐190: Daily Quality Assurance (QA) Procedure of On‐Board Imager (OBI)
Authors: Hammoud R , Guan H , Yin F , Pradhan D , Movsas B
Published: June 2005

Purpose: Developed a daily QA procedure for checking; 1) the accuracy of the imager isocenter and 2) the auto couch motion accuracy of the On‐Board Imager (OBI) device developed by Varian. This QA procedure will assure that the imager isocenter matches the mechanical isocenter and that the positional difference detected by the imager software can be reliably transferred to couch motion. Method and Materials: The Cube Isocenter Phantom provided by Varian was used for this daily QA procedure. Two sets of bb were used to define 2 separate spatial locations (points.) In each set, one bb is on the anterior side (AP bb) and the other (Lat bb) is on the lateral side of the phantom. The first set defines the isocenter (at the phantom center) and the second set defines a point 1.5 cm anterior, inferior, and lateral from the isocenter. An axial CT scan was acquired with a slice thickness of 2 mm. A plan with an AP MV and a Lat KV fields was created in Eclipse with the corresponding DRRs attached. The QA procedure starts with setting up the phantom center at the mechanical isocenter and taking AP MV and Lat KV images. The locations of the central bbs were first checked to get the accuracy of the imager isocenter. If that accuracy is acceptable, the central bbs in the KV/MV images were then manually moved to overlay to the off‐axis bbs in the DRR images. The shifts obtained will be applied to remotely move the couch. All data will be recorded. Results: This OBI QA procedure is simple and easy to implement. It usually takes 10–15 min to do the QA. The_accuracy the procedure can detect is better than 2mm. Conclusion: The suggested QA procedure is clinically robust and reliable.
SU‐FF‐T‐199: Heterogeneity Effects in Small‐Field Macular Irradiation
Authors: Chern S , Leavitt D , Gibbs F , Waterman G
Published: June 2005

Purpose: To evaluate the effects of bone heterogeneities on the dose distribution to the macula in small‐field macular irradiation. Method and Materials: An elliptical aperture measuring 8 mm × 10 mm on the major axes was constructed to project a circular field onto the macula through each of six fields focused on the macula and angled 28 degrees relative to the central axis of the eye. Using a stereotactic diode, the Tissue‐Maximum‐Ratio was measured for this aperture to a depth beyond the macula. These measurements were repeated using bone‐density material in order to approximate the attenuation through the cartilage of the nose and the supra‐orbital ridge. The beam profile at the depth of the macula was determined by film densitometry and the profiles for strictly soft tissue overlay were compared with the profiles for given thicknesses of bone density phantom added to the soft tissue. Lastly, the profile was determined for bone‐density phantom covering only half the field to simulate a treatment situation where the supra‐orbital ridge might intersect only half the incident field. Results: The excess attenuation of the bone material representing cartilage or supra‐orbital ridge is easily described by a simple exponential. The beam profile at the depth of the macula appears unchanged from the beam profile for soft tissue overlay, while the beam profile as modified by bone density material covering half the field shows a measurable attenuation through the bone. However, there is no widening of the profile in any of these situations. Conclusion: These results suggest that a small‐field pencil beam photon algorithm should be sufficient to calculate the radiation dose distribution for macular irradiation. Pencil beam and Monte Carlo dose calculation algorithms will be compared against these measurements. Conflict of Interest: This work supported by an SBIR grant to DIACOR, Inc.
SU‐FF‐T‐210: Performance Evaluation and Quality Assurance of Enhanced Dynamic Wedges
Authors: Alaei P , Higgins P
Published: June 2005

Purpose: Enhanced dynamic wedges have been used in clinical practice for many years. Obvious superiority of dynamic over physical wedges is accompanied by the increased overhead involved in verifying the accuracy and reliability of their use. Contrary to very limited quality assurance (QA) required to ensure proper functioning of the physical wedges, dynamic wedges, like any other dynamic treatment, require a robust quality assurance program. This work expands upon previous suggestions and describes a comprehensive QA program for Varian Enhanced Dynamic Wedges (EDW) and presents the results of a sixteen‐month evaluation of these wedges. Method and Materials: Daily, monthly, and annual QA procedures were devised for enhanced dynamic wedges on a dual energy Varian 21ex linear accelerator with seven wedge angles. These include daily constancy checks of the wedge performance as part of the morning QA procedure, monthly evaluation of wedge factors and profiles, and an analysis of dynamic log files generated by linac. Yearly performance evaluation includes measurement of a larger sample of wedge angles and profiles. In addition, individual treatment verification or “per patient” QA consists of visual inspection of the wedge direction at the conclusion of each treatment. Results: The daily constancy checks show a stable delivery of the wedged field with a variation of less than 1%. The monthly wedge factors measured have been within 1.5 % of the commissioning values. A comparison of beam profiles over the same time period shows a stable delivery of the wedged beams and good agreement with the expected segmented treatment tables (STT). Conclusion: An expended comprehensive QA of enhanced dynamic wedges is presented. Results of a sixteen‐month evaluation demonstrate stable and accurate delivery of these fields. Due to the dynamic nature of enhanced dynamic wedge deliveries, a comprehensive QA program is necessary to verify proper delivery of these fields.
SU‐FF‐T‐390: A New Linac QA Procedure for the Characterization of Radiation Isocenter and Room Lasers Position
Authors: Rosca F , Zygmanski P , Lorenz F , Hacker F , Chin L , Friesen S , Petsuksiri J , Shanmugham L , Ramakrishna N
Published: June 2005

Purpose: We have designed and implemented a new stereotactic machine QA test. The method is used to characterize gantry sag, couch wobble, cone placement, MLC offset and room lasers position relative to radiation isocenter. An image containing a series of test patterns is generated in a direct and integrated fashion. Method and Materials: Two MLC star patterns, a cone pattern and the laser lines are recorded on the same imaging medium, enabling 0.1 mm accuracy measurements. Phosphor plates are used as the imaging medium due to their unique property that the red light of wall laser erases the radiation information stored on phosphor plates. The room lasers position relative to the radiation isocenter can be measured. The developed QA method consists of four images that measure the gantry sag between 00 and 1800 gantry angles, the position and stability of couch rotational axis, the sag between 900 and 2700 gantry angles, the accuracy of cone placement on the collimator and the position of laser lines relative radiation isocenter. Results: The inherent precision of the numerical algorithms developed is +/− 0.05mm. The inherent accuracy of the method as a whole is +/− 0.1mm. The total irradiation/illumination time is about 10 min per image. Automating the generation of collimator star patterns can reduce this time. The data analysis (including the phosphor plate scanning) is less than 5min. Conclusion: The presented method reproducibly characterizes the radiation isocenter geometry with the high accuracy required for stereotactic surgery. It can replace the standard ball test and it can provide a highly accurate QA procedure for the non‐stereotactic machines.
SU‐FF‐T‐403: Evaluation of Doses Delivered by SBRT to the Lung of An Anthropomorphic Thorax Phantom
Authors: Alvarez P , Molineu A , Hernandez N , Followill D , Ibbott G
Published: June 2005

Purpose: Evaluation of SBRT through the use of a thorax phantom. Method and Materials: A new protocol evaluates stereotactic body radiation therapy for patients with lung cancer. Institutions must be credentialed before enrolling patients. Successful irradiation of a thorax phantom is one of the steps. The thorax phantom is a plastic shell incorporating structures that represent the spinal cord, the heart and the lungs. A structure representing a tumor is positioned in the left lung. TLDs and radiochromic films measure the delivered dose distribution. Institutions were instructed to image the phantom, plan a treatment following specific constraints and deliver the treatment as if to a patient. The measured dose distributions were compared to the institutions' calculated isodose distributions. Results: Institutions were instructed to deliver a treatment calculated without heterogeneity corrections and submit both corrected and uncorrected isodose distributions. Results from seven institutions established a baseline for this test. The average of the ratio between measured and calculated target dose was 0.97 ± 3% with corrections on and 1.14 ± 3% with corrections off. The displacement between measured and calculated dose distributions in the vicinity of the target did not exceed 5 mm. Conclusion: Criteria for the evaluation of this test were defined for heterogeneity‐corrected dose calculations. A range of 0.97 ± 7% was established for the ratio of measured and calculated target doses. A maximum of 5 mm displacement between the calculated dose distribution and the film profile was considered acceptable. Additional criteria are under consideration. This work was supported by PHS grants CA 10953 and CA 81647 awarded by NCI, DHHS.
SU‐FF‐T‐404: Fractionated Radiosurgery by Adaptation of Resources
Authors: Batchelar D , Bauman G , Fisher B , Taylor J , Wong E
Published: June 2005

Purpose: Our goal was to integrate broadly accessible, multi‐purpose tools to form a system for non‐invasive MLC‐based fractionated radiosurgery. We investigated the use of a Varian Millennium MLC (mMLC, 5mm‐leaf resolution) in conjunction with an aSi electronic portal imaging device (EPID) and Varian ZMed RadioCamera system for this purpose. Method and Materials: Pinpoint and RK chambers were used to measure data from small fields (mMLC shaped). Profiles for field sizes ranging from 4×4 to 1×1‐cm were measured in water, while output measurements were taken in a MedTec IMRT phantom. These data were used to commission an mMLC radiosurgery (fRS) beam in Theraplan Plus v3.8. Dose distributions created with this beam were compared both to measurement and circular collimator‐based SRS distributions. The RadioCamera system consists of an infrared camera and customized biteblock equipped with infrared markers. This detects motion in real time and allows the beam to be halted when a threshold is reached. The radio‐opaque markers are also used as a fiducial system for EPID. The motion sensitivity threshold and consistency of the biteblock‐mounted fiducials were both examined. Finally, the full system was tested using a film phantom outfitted with a biteblock. Results: Planning system predictions using the fRS beam match measured profiles, depth doses and output factors. Plans created with this beam were shown to approach those created using radiosurgery cones, based on DVH, homogeneity and conformity analyses. The IR camera system is sensitive to 0.2mm motion in all directions. Overall system test indicated that we can treat 1cm lesions with 0.3cm PTV and MLC margins. Conclusion: Our studies indicate that the combination of mMLC, infrared motion tracking, and EPID verification is sufficient to form a practical system for non‐invasive, fractionated radiosurgery, comparable to conventional linac‐based radiosurgery. This system is being used clinically at our institution.
MO‐D‐I‐618‐04: A Cost‐Effectiveness Model for New Radiation Oncology Technologies
Authors: Mills M , Spanos W , Esterhay R
Published: June 2005

Purpose: The additional equipment and personnel costs of supplying Intensity Modulated Radiation Therapy (IMRT) technology have caused many to question if the marginal gains in patient health‐related quality of life are worth the additional cost. A novel IMRT technology, helical tomotherapy, provides the opportunity to study cost and effectiveness for patients. Method and Materials: This methodological study proposes to evaluate the cost and effectiveness of treating conventional radiotherapy versus tomotherapy IMRT patients prospectively, among several institutions. The cost of treating patients varies between institutions, depending on personnel, equipment and overhead costs; however, the nature and quality of services provided are expected to be consistent. Results: The methodology study tracks cost information at a single institution, and simultaneously as the median from multiple institutions. Effectiveness measures include both standard quality adjusted life year instruments completed by patients and performance status measures completed by institutional personnel. In addition, disease specific effectiveness measures are accommodated in the study. Each participating institution uses the same effectiveness measures to track patients with similar disease. Conclusion: The resulting cost and effectiveness data is available to investigators at any point during the study, immediately upon the completion of a trial, or when statistical acceptability is achieved.
MO‐D‐I‐618‐05: Needs in Ionizing Radiation Measurements and Standards
Authors: Yoder R , Ibbott G
Published: June 2005

Purpose: The Council on Ionizing Radiation and Measurements and Standards (CIRMS) of which the American Association of Physicists in Medicine is an Organizational Member, has recently issued its triennial report identifying needs for standards in four primary areas: Radiation Protection, Medical Applications, Industrial Applications and Materials Effects, and Homeland Security. The report is used by the National Institute of Standards and Technology (NIST) and other government agencies to formulate and prioritize work in the development of appropriate standards. Method and Materials: Standards needs in the form of Measurement Program Descriptions (MPD) are formulated in a series of breakout sessions held during CIRMS annual meeting at NIST. Scientists from academia, government and industry collaborate in drafting the MPD's. Results: Twenty‐one MPD's appear in the Fourth Needs Report with four relating to Medical Applications, one for Computational Methods, eight for Radiation Protection and three for Homeland Security. The remainder address the special situations encountered in industrial radiation processing. Conclusion: CIRMS represents an important vehicle by which NIST interfaces with the combined interests of the academic and industrial community. CIRMS involvement influenced the development of radiation standards pertinent to calibrating radiation measurement instruments used in mammography.
MO‐E‐T‐618‐04: Treatment Planning Approach for Elongated Linear Sources for Prostate Implants
Authors: Awan S , Koona R , Rachabatthula V , Meigooni A
Published: June 2005

Purpose: Recently pseudo and true elongated linear brachytherapy sources have become available for prostate implants. These sources were designed to eliminate the problems associated with loose seed type implants such as seed migration and embolization. However, majority of the commercially available prostate treatment planning systems are not capable to perform dose calculations with the elongated linear source types. In this project an intermediate solution for prostate treatment planning with elongated linear sources has been introduced using commercially available treatment planning systems. Method and Materials: Two new models have been introduced for calculating dose distribution around linear sources greater than 1.0 cm in length. Dose distributions around elongated linear source were obtained either by super position of 0.5 cm or 1.0 cm long source segments using line (LSS) or point (PSS) source approximation in treatment planning systems. These models have been validated by calculating dose distribution around RadioCoil™ sources using Prowess™ and VariSeed™ treatment planning systems and comparing the results with Monte Carlo Simulated data. Clinical application of these models for a multi source implant has been validated by treatment planning for a sample prostate patient. Results: Results of LSS and PSS models are found to be in good agreement with of Monte Carlo simulated data (within 4%) for the points within the active length of the source. Discrepancy is noted for the points out side the active length of the source and is under investigations. Moreover, ABS recommended parameters obtained with these models for a sample prostate patient are in good agreement to that of “seed” type implant using Model 200. Conclusion: These results show that the new models can easily be adapted for dose calculations with commercially available treatment planning systems for elongated linear sources. These models provide an intermediate solution for the treatment planning with elongated sources.
MO‐E‐T‐618‐06: Correcting LDR Spectroscopy for Fine Energy Resolution Applications
Authors: Beach S , DeWerd L
Published: June 2005

Purpose: To use high purity Germanium spectrometry to measure output energy spectra of LDR brachytherapy seeds in order to provide better dosimetric information than what is currently available. Such spectral information can provide a platform for energy based dosimetry of LDR seeds as well as provide ‘energy output’ benchmarks for Monte Carlo simulation of these sources. Method and Materials: Low energy Germanium spectroscopy suffers from several inherent defects of the spectrum collection process. Peak energy broadening and generation of fluorescence escape peaks are two defects, both of which can complicate and contaminate measured spectra. A correction algorithm is presented to overcome these defects and reproduce the true energy spectra without detector produced artifacts and without a priori assumptions as to the internal LDR seed structures. Collection of output spectra from various LDR seeds was obtained using an n‐type Germanium spectrometer. A detector response function matrix (8037 element square) was constructed via detailed MCNP Monte Carlo simulations to characterize the detection process from the detector's entrance window to particle termination, spanning interactions from 1352 keV down to 3.75 keV. The correction algorithm is based upon an iterative algorithm used in high‐ to moderate‐energy physics, as detailed in the literature for Germanium spectroscopy. This modified algorithm in conjunction with the response matrix reconstructs the spectrum as it was prior to interaction with the detector. Results: Corrected results have shown excellent agreement with expected theoretical spectral outputs, and spectral peak resolutions of less than 0.5 keV have been achieved. High resolution output spectra have been catalogued for multiple seed designs. Spectral Air Kerma Strength calculations, utilizing corrected spectra, agree with NIST traceable calibrated Air Kerma Strengths to within 3%. Conclusion: This technique allows corrections to be made to acquired spectra thus yielding data for high resolution applications of non‐energy‐integrated dosimetry of LDR seeds.
MO‐E‐T‐617‐04: An Efficient Adjoint Monte Carlo Method for Radiation Treatment Planning
Authors: Wang B , George Xu X. , Goldstein M , Xing L
Published: June 2005

Purpose: Adjoint Monte Carlo methods were originally developed for optimizing nuclear reactor designs, but have recently shown to be useful in radiation treatment planning. This study evaluates the efficiency of the AMC method and addresses several issues on implementing it into the MCNP code for potential IMRT treatment planning. Method and Materials: We compare the difference between an adjoint and a forward Monte Carlo calculations for computing time and dose. By exploring a tally feature (FT card) of MCNP, we then describe a source sampling scheme for multiple ROIs of the patient body in a single adjoint simulation. Two methods are used in this study to speedup the Monte Carlo simulations, which includes a mesh tally speedup and a variant reduction technique (VRT) using importance functions from the adjoint Monte Carlo calculations. Results and Discussions: The doses calculated by the forward and the adjoint MC are in a good agreement within statistical uncertainties. After normalized to the same statistical uncertainties, the computing time of the forward run is about 9 times of that of the adjoint run, which clearly demonstrates the computing efficiency of an adjoint simulation over a forward run. We also successfully implemented a source sampling scheme for different ROIs in only one simulation. This facilitates future implementation of an automatic AMC‐based radiation treatment planning system. The VRT reduces the forward MC calculation time by approximately 26.7% for the prostate case. The reduction for the urinary bladder and the rectum is 24.8% and 13.6%, respectively. Conclusion: The efficacy and efficiency of the AMC method in achieving optimized dose objective have been demonstrated. The potential for the AMC method to be useful in treatment planning of IMRT procedures is particularly attractive because the large number of beam parameters involved.
TU‐C‐J‐6B‐01: From Morphological to Functional Definition of Organs at Risk: The Role of FMRI in Radiosurgery
Authors: Stancanello J , Cavedon C , Francescon P , Avanzo M , Cora S , Scalchi P
Published: June 2005

Purpose: functional magnetic resonance (fMRI) identifies areas related to different modality tasks. It is possible to identify particular areas in the brain which can be considered like “functional organs at risk” (fOARs). The aim of this study is to describe a method to exploit this functional information for the identification of fOAR in radiosurgery treatment planning. Method and Materials: for a patient who underwent radiosurgery treatment, CT and 60 EPI MR volumes were acquired for BOLD analysis of functional areas. Tasks were chosen on the base of the lesion location. The functional maps obtained by Statistical Parametric Mapping (SPM) software refer to the template volume: if one wants to exploit this information for patient treatment, it is necessary to calculate the deformation field which maps the template onto the CT. Treatment planning was performed using the CyberKnife radisourgery system. Results: the method has been applied to a patient with a right frontal metastasis of breast cancer. We have performed BOLD analysis of the motor function with self‐passed left hand and left foot tasks, and of language related areas using category generation task (CGT), letter generation task (LGT), and simple questions task (SQT). It has been found that the activation of the 2 motor tasks was very close to the lesion while for the CGT, LGT and SQT studies the most significant constraint deals with the language associative areas located in the dorso‐lateral frontal cortex (Brodman areas 8 –9). Conclusion: treatment plans studied with and without considering the fOARs were significantly different, in particular for the Dose Volume Histograms (DVH), while maintaining dose indices almost constant (homogeneity equal to 1.15 with fOARs and 1.18 without fOARs; conformity equal to 1 for both plans), proving a potential role of fMRI in radiosurgery.
TU‐C‐J‐6B‐07: 3DUS, MRI and CT Prostate Volume Definition: 3D Evaluation of Intra‐ and Inter‐Modality and Observer Variability
Authors: Smith W , Lewis C , Bauman G , Rodrigues G , D'Souza D , Ash R , Venkatesan V , Downey D , Fenster A
Published: June 2005

Purpose: To produce a complete three‐dimensional description of the accuracy, variability significance of differences in prostate volume estimation using 3DUS, MR and CT imaging. Method and Materials: Ten patients underwent 3DUS, MR (axial FSE T2‐weighted) and CT imaging 28–33d after I–125 implant (74–112 seeds, mean=93.3). MR prostate volume range was 22.6–50.8cc (mean=31.9cc). Seven experienced observers contoured prostate volumes in 2.5 mm slice increments, twice for each patient, while blind to image duplication within and between modalities. Regional trends in variability and absolute differences in volume estimation between modalities were examined in 3D. Results: The average volume ratio was 1.16 for CT/MR, 0.90 for US/MR and 1.30 for CT/US. The greatest variability of CT contours occurred at the posterior and anterior portions of the mid‐gland. On MR images, the overall variability was smaller, with a maximum in the anterior region. On 3DUS, high variability occurred in the anterior regions of the apex and base, while the prostate‐rectum interface had the smallest variability. 3DUS contours tended to be larger than CT and MR in the anterior and posterior aspects of some patients, likely due to gland deformation by the US probe. The average percent of surface area that was significantly different (95% confidence) was 4.1%, CT‐MR; 10.7% US‐MR; 6.3% CT‐US. Both center‐of‐mass registration and larger standard deviation of CT measurements increase statistical similarity of CT to other modalities. Using seeds as fiducial markers decreases this similarity. Deformation during insertion of the trans‐rectal ultrasound probe, rectum and bladder filling and breathing motion also have an effect. Conclusion: Our findings suggest that improved seed recognition algorithms for 3DUS or MR, or fusion with CT may improve the accuracy of post‐implant planning. Visualization of 3D trends between modalities may assist in improving the consistency of prostate delineation.
TU‐C‐P‐618‐01: Part I: Legislative and Regulatory Status
Authors: White G
Published: June 2005

Clinical Medical Physicists do not currently have provider status and thus do not bill patients or their third party payors directly for patient specific services. If Medical physicists were to participate in the direct billing process in the U.S. Healthcare system, both legislative and regulatory changes would be required. Changes to Federal statures and the Code of Federal Regulations that would be necessary to enable direct billing will be described. In addition, the process for modification of Current Procedural Terminology (CPT) codes and their associated valuation levels (maintained by a combination of voluntary professional Societies and the Center for Medicare and Medicaid Services) will be reviewed.
TU‐C‐T‐617‐08: Peripheral Doses in CyberKnife Radiosurgery
Authors: Petti P , Chuang C , Smith V , Larson D
Published: June 2005

Purpose: To measure doses delivered outside of the irradiated volume for typical CyberKnife treatments and to compare the results to peripheral doses arising from similar Gamma Knife (GK) and IMRT treatments. Method and Materials: CyberKnife treatment plans were developed for two hypothetical lesions in an anthropomorphic phantom, one in the thorax and another in the brain. In both cases, 500 cGy was prescribed to the 70% isodose line. Li‐F TLD‐100 capsules were placed within the phantom at various depths and distances from the irradiated volume. For the brain lesion, GK and 6‐MV IMRT treatment plans were also developed, and peripheral doses were measured. Results: Peripheral doses for the CyberKnife thorax treatment ranged from 3.3±0.13% to 1.2±0.06% of the prescribed dose (Dp) at distances between 15 and 43 cm from the edge of the target. For the target in the brain, CyberKnife peripheral doses ranged from 1.2±0.02% to 0.32±0.02% of Dp at distances between 18 and 71 cm from the target edge. In comparison, the GK peripheral dose ranged from 0.63±0.03% to 0.053±0.002% of Dp, and the IMRT plan resulted in doses between 0.19±0.004% and 0.043±0.002% of Dp over the same range of distances. Conclusion: Doses outside the irradiated volume for Cyberknife treatments are significantly higher than those encountered in standard radiation therapy. Peripheral doses given in AAPM Task Group Report No. 36 (Stovall, et al. Med. Phys. 22:63–82, 1995) for a 6‐MV beam are between 0.2% and 0.02% of the dose at dmax at a distances ranging from 20 to 70 cm from the edge of a 5×5cm2 field. Furthermore, for the same target in the brain, CyberKnife peripheral doses were a factor of 2 to 6 times larger than those for GK, and a at least a factor of 6 times larger than those for IMRT.
TU‐D‐J‐6B‐03: Physics and Applications of Preclinical Micro‐Ultrasound Imaging
Authors: Foster S
Published: June 2005

Bioresearch in functional genomics is poised to make major contributions to our understanding of normal development and human disease. This promise will, in part, rely on the development of new micro‐imaging technologies to provide quantitative longitudinal assessment of morphological and functional development of normal and abnormal tissues. In addition, imaging tools will need to be further refined to enable high throughput phenotypic assessment of the rapidly escalating numbers of targeted and random mouse mutations. This presentation will focus on the development of high frequency (20 to 70 MHz) ultrasound biomicroscopy (UBM) for mouse imaging. While UBM does not provide molecular specificity, it has the advantage of low cost, rapid imaging speed, portability and high resolution (30–100 microns). The physics of high frequency ultrasound will be reviewed and the latest developments in instrumentation will be presented. Applications of 2 and 3D imaging to mouse cardiovascular assessment, cancer and ocular diseases will be described. Recent advances in 3D UBM imaging now permit the volumes of growing experimental tumors to be assessed with relative ease. Examples of tumor growth studies will be presented. In particular, a human melanoma (MeWo) and a model of retinoblastoma will be examined. Further analysis of Doppler and other flow related data offers insight to microvascular development and its alteration during treatment. This is particularly relevant to angiogenesis and antiangiogenic treatments. As an example of antiangiogenic therapy, a study of DC101 (ImClone Systems), a monoclonal anti‐VEGFR2 antibody will be presented. The authors wish to acknowledge the financial support of the Canadian Institutes for Health Research, the National Cancer Institute of Canada with funds from the Terry Fox Foundation, the Ontario Research and Development Challenge Fund, and VisualSonics Inc. FSF also discloses a financial interest in VisualSonics Inc.
TU‐E‐T‐6E‐03: MDCB Perspective On “Teaching Physics to Dosimetrists”
Authors: Das I
Published: June 2005

Goal of the organization or project: The Medical Dosimetry Certification Board (MDCB) provides examination for competency in clinical and medical physics area for dosimetrist. The candidates who pass the examination are called Certified Medical Dosimetrist (CMD). Medical physics education and training curriculum is essential for a good patient care and qualifying the MDCB examination. Accomplishments: Since 1988, over 2200 dosimetrist are certified through MDCB examination. There are limited number of medical dosimetry programs that provide training and education. JRCERT accreditation is highly recommended for programs offering dosimetry training. The MDCB popularity has grown internationally. Last year Korea was added as MDCB examination site. Several other countries are being considered for MDCB test sites. Resources to help physicists know what to teach: There are nine categories in the examination; radiation physics, dose calculation methods, treatment planning, localization, brachytherapy, radiation protection, quality assurance, professional responsibility and computers with 20%, 25%, 30%, 8%, 5%, 2%, 3%, 2% and 5% questions, respectively. Proper medical physics education and training responsibility rests on medical physicists. A physicist who is planning to teach dosimetry course should visit www.MDCB.org and familiarize with the didactic and training requirements and other valuable information. Upcoming changes: The examinations are critically evaluated every year and at a regular interval through strategic planning that was conducted in 2003. The outcome is being implemented in 2005 examinations. Continuing education is being updated to maintain CMD certification. Formal training and accredited programs are given more importance.