(Sunday, 7/14/2019)
Room: ePoster Forums
Purpose: To compare different dose rate calibration methods with Elekta ABS plastic phantom and certified therapy grade solid water phantom in setting up dose-to-water reference for GammaKnife ICON machine.
Methods: Calibrations for absolute dose rate using the Elekta ABS plastic phantom (gray phantom) and the Leksell Gamma Knife Dosimetry Phantom (a certified therapy grade spherical solid water phantom) were conducted for a Leksell GammaKnife ICON machine. The TG-21 protocol was followed in the calibration with the spherical plastic phantom, while the TG-51 and a modified TG-51 protocols were followed with the solid water phantom. An Extradin A16 ion chamber and PTW Unidos Webline dosimeter were used in the measurements. The results of the three protocols were compared. The machine output was also verified with the Radiological Physics Center (RPC) TLDs in the gray phantom.
Results: Table 1 listed the results from measurements with the two phantoms and three protocols. Compared to the TG-51 protocol in the solid water phantom, the dose rate measured with TG-21 in the gray phantom and modified TG-51 in the solid water phantom were 1.4% higher and 0.5% lower, respectively. The dosed rate reading provided by the RPC was 1.6% higher than the TG-21 protocol dose. The difference between the measurements with TG-21 in the gray phantom and TG-51 in the solid water phantom were within 1.5%.
Conclusion: The TG-21 protocol in the gray phantom and either TG-51 or the modified TG-51 protocols in the solid water phantom can be used for setting up dose-to-water reference for the GammaKnife ICON machine.
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