Özet:

OBJECTIVES We aimed to measure entrance-exit doses using in-vivo dosimetry for head and neck cancer patients and to compare with planning system doses, to facilitate determination of treatment accuracy. METHODS Three diodes were calibrated using water equivalent phantom. Correction factors had been previously assessed for in-vivo diodes and applied to the readings. Dose measurements were performed on 30 treatment setups for 3 patients treated with isocentric, asymmetric left-right two lateral and supraclavicular fields using 6MV. Measured doses were compared with expected doses. RESULTS The results indicated a small acceptable deviation from expected doses. It was found that the mean deviations for entrance and exit doses were 2.3% and 1.9%, respectively. The deviation in the delivered dose is well within the 5% International Commission on Radiation Units and Measurements (ICRU) recommendation, and thus treatment doses are determined to be in accordance with the planning system doses. CONCLUSION It has been shown that in-vivo dosimetry performed using diodes is a reliable and high-precision method for patient dose control.

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