TH-A-BRC-03: AAPM TG218: Measurement Methods and Tolerance Levels for Patient-Specific IMRT Verification QA.

AAPM TG-135U1 QA for Robotic Radiosurgery - Sonja Dieterich Since the publication of AAPM TG-135 in 2011, the technology of robotic radiosurgery has rapidly developed. AAPM TG-135U1 will provide recommendations on the clinical practice for using the IRIS collimator, fiducial-less real-time motion tracking, and Monte Carlo based treatment planning. In addition, it will summarize currently available literature about uncertainties.

LEARNING OBJECTIVES: 1. Understand the progression of technology since the first TG publication 2. Learn which new QA procedures should be implemented for new technologies 3. Be familiar with updates to clinical practice guidelines AAPM TG-178 Gamma Stereotactic Radiosurgery Dosimetry and Quality Assurance - Steven Goetsch PURPOSE: AAPM Task Group 178 Gamma Stereotactic Radiosurgery Dosimetry and Quality Assurance was formed in August, 2008. The Task Group has 12 medical physicists, two physicians and two consultants.

METHODS: A round robin dosimetry intercomparison of proposed ionization chambers, electrometer and dosimetry phantoms was conducted over a 15 month period in 2011 and 2012 (Med Phys 42, 11, Nov, 2015). The data obtained at 9 institutions (with ten different Elekta Gamma Knife units) was analyzed by the lead author using several protocols.

RESULTS: The most consistent results were obtained using the Elekta ABS 16cm diameter phantom, with the TG-51 protocol modified as recommended by Alfonso et al (Med Phys 35, 11, Nov 2008). A key white paper (Med Phys, in press) sponsored by Elekta Corporation, was used to obtain correction factors for the ionization chambers and phantoms used in this intercomparison. Consistent results were obtained for both Elekta Gamma Knife Model 4C and Gamma Knife Perfexion units as measured with each of two miniature ionization chambers.

CONCLUSION: The full report gives clinical history and background of gamma stereotactic radiosurgery, clinical examples and history, quality assurance recommendations and outline of possible dosimetry protocols. The report will be reviewed by the AAPM Working Group on Recommendations for Radiotherapy External Beam Quality Assurance and then by the AAPM Science Council before publication in Medical Physics 1. Survey of possible calibration protocols for calibration of Gamma Stereotactic Radiosurgery (GSR) devices 2. Overview of modern Quality Assurance techniques for GSR AAPM TG-218 Tolerance Levels and Methodologies for IMRT Verification QA - Moyed Miften Patient-specific IMRT QA measurement is a process designed to identify discrepancies between calculated and delivered doses. Error tolerance limits are not well-defined or consistently applied across centers. The AAPM TG-218 report has been prepared to improve the understanding and consistency of this process by providing recommendations for methodologies and tolerance limits in patient-specific IMRT QA.

LEARNING OBJECTIVES: 1. Review measurement methods and methodologies for absolute dose verification 2. Provide recommendations on delivery methods, data interpretation, the use of analysis routines and choice of tolerance limits for IMRT QA Sonja Dieterich has a research agreement with Sun Nuclear Inc. Steven Goetsch is a part-time consultant for Elekta.