Quality assurance of imrt delivery systems thomas losasso, phd 3 is exposed with 6mv xrays at isocenter without buildup in order to obtain a sharp image. Commissioning and quality assurance of volumetric modulated arc radiotherapy with rapidarc european medical physics and engineering conference 2011 trinity college dublin, ireland adriana. Dosimetric evaluation of mobiusfx in the rapidarc delivery. The imsure qa 3source model for imrt calculations is more accurate than the modified clarkson method used by all of the other solutions. Ionization chamber statistics all 6mv dmlc beams per patient 00 1 7 17 27 22. Quality assurance of imrt delivery systems thomas losasso, phd. To ensure that imrt services consistently meet the highest clinical standards, each institution must invest in a comprehensive qa program for imrt planning and delivery. Software quality assurance and control has taken many forms over the years, from it being the responsibility of the development team alone through to it being a separate function all together and. The imsure qa user interface is designed so all of the.
Our software is also effective for the qa of srs, sbrt and vmat procedures. Several methods for quality assurance qa of mlc position in imrt have been proposed. Imrt for conventional radiotherapy, thompson et al. However, all these activities have not yet resulted in a comprehensive set of practical guidelines for the verification of imrt. In lung cancer patients, the accuracy of dose calculation by radiotherapy treatment planning systems may be reduced by the presence of tissue inhomogeneities. Comprehensive quality assurance for the delivery of. Quality assurance qa procedures for a linear accelerator linac and multi. A comparison of the quality assurance of four dosimetric. A clinical objective imrt qa method based on portal dosimetry and electronic portal imager device epid measurement. It begins at the time of installation of new equipment or at the time an existing mlc is upgraded for use with imrt in order to affirm the capability for accurate imrt with the specific mlc. Paper open access picket fence test of agility mlcs using. Imrt treatment plan independent software algorithm geometrymlc mumodality data comparison of dose distributions. Department of radiation oncology, university of florida, gainesville, fl. Comparisons of volumetric modulated arc therapy vmat.
The quality assurance of volumetric modulated arc therapy. Although this method is generally performed with radiographic film, it is timeconsuming and analysis is costly. The aim of this study was to investigate the sensitivity of three vmat qa systems to machine errors. For this collimator opening, the new mlc scatter algorithm increased the dose by 1% over the previous method. As radiation therapy transitions from intensity modulated radiation therapy imrt to volumetric modulated arc therapy vmat it is important to consider the quality assurance qa of. Omni pro imrt software to obtain measured dose distributions. The delta4 3d dose verification device was commissioned in the current work for pretreatment quality assurance qa of intensity modulated radiotherapy imrt and volumetric modulated arc therapy. Qa of intensitymodulated beams using dynamic mlc log. Quality assurance of imrt delivery systems varian aapm. The garden fence test is traditionally used to verify the actual versus planned mlc stop position 5, 6. The delta4 3d dose verification device was commissioned in the current work for pretreatment quality assurance qa of intensity modulated radiotherapy imrt and volumetric modulated arc therapy vmat plans. We chose to base our work on the foundations laid in previous ncs reports. This study was designed to compare the quality assurance qa results of four dosimetric tools used for intensity modulated radiation therapy imrt and to suggest universal criteria for the passing rate in qa, irrespective of the dosimetric tool used.
In intensitymodulated radiation therapy imrt, the radiation fluence of. Local implementation of planspecific quality assurance qa methods for intensitymodulated radiotherapy imrt and volumetric modulated arc therapy vmat treatment plans may vary because of dissimilarities in procedures, equipment and software. Quality control of intensity modulated radiation therapy. Comprehensive quality assurance for the delivery of intensity modulated radiotherapy with a multileaf collimator used in the dynamic mode thomas losasso, chenshou chui, and c. If these problems are rectified or at least understood by the physicist, quality assurance can be simplified. Guidance document on delivery, treatment planning, and clinical implementation of imrt. Quality assurance of imrt delivery systems thomas losasso, phd 2 impact in this case. Local implementation of planspecific quality assurance qa methods for intensitymodulated radiotherapy imrt and volumetric modulated arc therapy vmat treatment plans may vary because. Quality assurance criteria, often carried over from static fields, do not reflect the. It begins at the time of installation of new equipment or at the time an. May 01, 2008 for intensitymodulated radiotherapy imrt, dose delivery throughout the target volume is sensitive to leaf positioning and leaf transmissions because of the relatively small subfields and the increased monitor units mus characteristic of imrt plans. Volumetric modulated arc therapy linkedin slideshare. The purpose of this work is detecting possible differences between local qa findings and those of an audit, using the same set of treatment plans.
Tolerance limits and methodologies for imrt measurement. Importance of testing the mlcs and understanding their physical and dosimetric aspects has. Qa of intensitymodulated beams using dynamic mlc log files m dinesh kumar, n thirumavalavan, d venugopal krishna. The software environment could also remove objects from the ct scan such as immobilization masks, bolus, etc in order to use the actual patient devices in the imrt qa measurements. The accuracy and usefulness of mobiusfx in clinical cases was evaluated by comparing the dose calculated by mobiusfx with that calculated by the conventional measurement dose based. Qa of intensitymodulated beams using dynamic mlc log files. Standard imaging provides a wide range radiotherapy qa software, from epid qa to imrt qa, to tg142 imaging and machine qa. Commissioning and quality assurance of rapidarc radiotherapy delivery system. Built for pretreatment imrt qa sunpoint 2 diode detectors placed uniformly throughout the array offer high sensitivity and proven stability in a large active field size 26 cm x 32 cm. It is the main purpose of this report to provide groups starting with imrt, as well as groups that have already some experience with imrt, guidance in the performance of verification tests, as part of an imrt qa. Filmqa pro software is a sophisticated, quantitative analysis tool specifically designed to simplify and streamline the intensitymodulated radiation therapy quality assurance imrt qa. A multipurpose quality assurance tool for mlcbased imrt.
Composite images testing the alignment of the mlc using the leaf patterns of the. The purpose of this work was to develop an endtoend patientspecific quality assurance qa technique for spotscanned proton therapy that is more sensitive and efficient than traditional approaches. This study was designed to compare the quality assurance qa results of four dosimetric tools used for intensity modulated radiation therapy imrt and to suggest universal. To investigate the sensitivity of various gamma criteria used in the gammaindex method for patientspecific volumetric modulated arc therapy vmat quality assurance qa for stereotactic. Dosimetric and qualitative analysis of kinetic properties of. Cancer care service, royal brisbane and womens hospital herstonau.
However, the mechanical and software designs of mlcs from the different manufacturers distinguish them. Quality assurance of intensity modulated radiation therapy. Burman c, chui c s, kutcher g, leibel s, zelefsky m, losasso t, spirou s, wu q, yang j, stein j, mohan r, fuks z, ling c c 1997 planning, delivery, and quality assurance of intensitymodulated radiotherapy. Planned, delivered and measured dose distributions are analyzed by gamma evaluation method in scanditronix. Imrt delivery system qa thomas losasso, phd memorial sloan kettering cancer center imrt dose delivery acceptance testing commissioning quality assurance verification q a static imrt leaf affects borders only affects dose within target position 12 mm ok 0. In the broad sense, qa for imrt delivery encompasses acceptance testing, commissioning, routine mlc qa, and patientspecific qa. Department of medical physics, memorial sloan kettering cancer center, new york, new york 10021. Course of actions to check and evaluate failed or marginal imrt qa results 8. The dosimetric characteristics of mobiusfx, which uses the treatment machine log file to calculate the dose inside the patient body, were analyzed for use in the rapidarc delivery quality assurance dqa. For larger imrt fields, mlc scatter could alter the calculated dose by up to 5%. Clinical implementation of dynamic intensitymodulated radiotherapy.
Clinical implementation of volumetric modulated arc therapy. For intensitymodulated radiotherapy imrt, dose delivery. Correct reporting and handling of the plan and measured data. To investigate the sensitivity of various gamma criteria used in the gammaindex method for patientspecific volumetric modulated arc therapy vmat quality assurance qa for stereotactic body radiation therapy sbrt using a flattening filter free fff photon beam. The use of a multileaf collimator mlc for intensitymodulated radiotherapy poses unique. Although these guidelines are primarily focused on imrt treatments in belgian and dutch clinics, other institutes. Our experience in commissioning of imrt and qa tests for clinical. A realtime electrometer measures every pulse with 50millisecond updates. Clifton ling department of medical physics, memorial sloan kettering cancer center, new york, new york 10021 received 5 february 2001. Monitoring daily mlc positional errors using trajectory.
Burman c, chui c s, kutcher g, leibel s, zelefsky m, losasso t, spirou s, wu q, yang j, stein j, mohan r, fuks z, ling c c 1997 planning, delivery, and quality assurance of intensitymodulated radiotherapy using dynamic multileaf collimator. The quality assurance qa system should be able to catch the planning and machine errors. The cross calibration and relative array calibration were performed to enable absolute dose comparison. Gamma evaluation for seven field step and shoot imrt prostate case 1.
Guidelines for the development of imrt suggested that individual patientspeci. The imsure qa user interface is designed so all of the information you need to make a decision about your plan is presented on a single screen. The dosimetric characteristics of mobiusfx, which uses the treatment machine log file to calculate the dose inside the patient body, were analyzed for use in the rapidarc delivery quality assurance dqa process. The semiweekly test is performed by our therapists preferably at the end of the treatment day, but at least 6 hours following initialization. The linearity of response with dose and temperature sensitivity tests were also. Commissioning and quality assurance of rapidarc delivery system. Highly efficient and sensitive patientspecific quality. Clinical objective imrt qa is a new approach to conduct patient specific imrt qa by evaluating the qa result based on metrics like the structure dose volume histograms dvh on the planning ct imag.
Ionization chamber statistics all 6mv dmlc beams per patient 00 1 7 17 27 22 9 10 3 00 0 5 10 15 20 25 30. Jul 10, 2012 several methods for quality assurance qa of mlc position in imrt have been proposed. Finally, a software environment to streamline the customization of the patient geometry to include detectors i. A multicentre dosimetry audit on advanced radiotherapy in. In addition to a large initial investment in the imrt hardware and software, adequate qualified personnel resources are necessary for the initial commissioning and ongoing qa.
The quality assurance qa system should be able to catch. Quality assurance of intensitymodulated radiation therapy. Mobius fx, an addon software module from mobius medical systems for intensitymodulated radiation therapy imrt quality assurance qa, uses linac treatment logs to efficiently calculate and. A clinical objective imrt qa method based on portal. The two software are both user friendly and straight forward. For intensitymodulated radiotherapy imrt, dose delivery throughout the target volume is sensitive to leaf positioning and leaf transmissions because of the relatively small subfields and the. Mlc quality assurance techniques for imrt applications. Physical and dosimetric aspects of a multileaf collimation. Mlc positional accuracy evaluation through the picket. Three types of intentional misalignments were introduced to original highdefinition multileaf collimator hdmlc plans. It allows you to scan or open images of exposed film and calculate the optimized. The detailed dosimetric comparison between planned and measured planar dose distribution is the cor e of imr t. Although these guidelines are primarily focused on imrt treatments in belgian and dutch clinics, other institutes should also be able to benefit from the report. In terms of dosimetry, intensity modulated radiation therapy imrt treatments utilising a linear accelerator linac with dynamic multi.
Other imrtvmat commissioning ezzel ga, galvin jm, low d et al. The delivery of intensity modulated radiation therapy imrt. The patientspecific methodology relies on independently verifying the accuracy of the delivered proton fluence and the dose calculation in the heterogeneous patient volume. Quality assurance of mlc leaf position accuracy and. Physical and dosimetric aspects of a multileaf collimation system used in the dynamic mode for implementing imrt. Comprehensive quality assurance for the delivery of intensity modulated radiotherapy with a multileaf collimator used in the dynamic mode.
Recheck values used for dose and dta tolerance, dose threshold, and registration of the measured and calculated dose distributions. The detailed imrt qa is described by losasso et al. It is the main purpose of this report to provide groups starting with imrt, as well. Imrt delivery performance with a varian multileaf collimator. Intensity modulated radiation therapy imrt represents one of the major technical innovations in modern radiation therapy rt. Clinical implementation of a 3d dosimeter for accurate. Several types of potential linac machine errors unique to vmat delivery were. Recheck values used for dose and dta tolerance, dose threshold, and registration of the measured and calculated. Patient specific 3d printed phantom for imrt quality assurance. The delta4pt and its software provides the ability to perform a linac qa check for both the. Code of practice for the quality assurance and control for.
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