The task group (TG) for quality assurance for robotic radiosurgery was formed by the American Association of Physicists in Medicine's Science Council under the direction of the Radiation Therapy Committee and the Quality Assurance (QA) Subcommittee. The task group (TG-135) had three main charges: (1) To make recommendations on a code of practice for Robotic Radiosurgery QA; (2) To make recommendations on quality assurance and dosimetric verification techniques, especially in regard to real-time respiratory motion tracking software; (3) To make recommendations on issues which require further research and development. This report provides a general functional overview of the only clinically implemented robotic radiosurgery device, the CyberKnife V R . This report includes sections on device components and their individual component QA recommendations, followed by a section on the QA requirements for integrated systems. Examples of checklists for daily, monthly, annual, and upgrade QA are given as guidance for medical physicists. Areas in which QA procedures are still under development are discussed.
The scope of this study was to estimate total scatter factors ͑s c,p ͒ of the three smallest collimators of the Cyberknife radiosurgery system ͑5-10 mm in diameter͒, combining experimental measurements and Monte Carlo simulation. Two microchambers, a diode, and a diamond detector were used to collect experimental data. The treatment head and the detectors were simulated by means of a Monte Carlo code in order to calculate correction factors for the detectors and to estimate total scatter factors by means of a consistency check between measurement and simulation. Results for the three collimators were: s c,p ͑5 mm͒ = 0.677± 0.004, s c,p ͑7.5 mm͒ = 0.820± 0.008, s c,p ͑10 mm͒ = 0.871± 0.008, all relative to the 60 mm collimator at 80 cm source-to-detector distance. The method also allows the full width at half maximum of the electron beam to be estimated; estimations made with different collimators and different detectors were in excellent agreement and gave a value of 2.1 mm. Correction factors to be applied to the detectors for the measurement of s c,p were consistent with a prevalence of volume effect for the microchambers and the diamond and a prevalence of scattering from high-Z material for the diode detector. The proposed method is more sensitive to small variations of the electron beam diameter with respect to the conventional method used to commission Monte Carlo codes, i.e., by comparison with measured percentage depth doses ͑PDD͒ and beam profiles. This is especially important for small fields ͑less than 10 mm diameter͒, for which measurements of PDD and profiles are strongly affected by the type of detector used. Moreover, this method should allow s c,p of Cyberknife systems different from the unit under investigation to be estimated without the need for further Monte Carlo calculation, provided that one of the microchambers or the diode detector of the type used in this study are employed. The results for the diamond are applicable only to the specific detector that was investigated due to excessive variability in manufacturing.
The dosimetry of the fields usually employed in radiosurgery requires the use of small detectors to measure Total Scatter Factor (Sc,p), Tissue Maximum Ratio (TMR), Percentage Depth Dose (PDD), and Off Axis Ratio (OAR). In this paper new dosimeters are investigated: a new type of radiochromic film, a micro parallel-plate chamber (filled with both air and tetramethylsilane, TMS), MOSFETs, and TLD-800 microcubes. Their behavior has been compared with the response of radiographic film and with the values obtained with BEAM Monte Carlo simulation. The experimental data confirm that dosimetry with radiochromic films and TLDs gives consistent results for all beam diameters. The parallel-plate micro chamber underestimates the Sc,p for the smallest field diameters (4.4 mm and 6.7 mm); MOSFETs show an over-estimation for the Sc,p of the 4.4 mm, 6.7 mm, and 10.5 mm field diameters. BEAM Monte Carlo simulation employing a parallel beam and a standard 6 MV x-ray spectrum has been used to obtain a correction factor as a function of the field size for both the parallel-plate micro chamber and MOSFETs. High accuracy measurements of PDD and TMR have been made in a water phantom both with radiochromic film and with the micro parallel-plate chamber and have been compared with the data computed by BEAM Monte Carlo simulation. The latter dosimeter is preferred because of the quicker and simpler use and because it gives immediate readout. Measurements of OAR made with radiochromic films and with radiographic films give differences in the 80%-20% penumbra width within 0.6 mm for field diameters ranging from 4.4 mm to 19 mm.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.