Peripheral dose measurement with a MOSFET detector.

The accuracy of a MOSFET dosimetry system with respect to peripheral therapeutic doses from high-energy X-rays has been evaluated. The results have been compared with ionisation chamber measurements in the same peripheral regions of the beam. For 6 MV and 18 MV X-ray beams, the MOSFET system in the high-sensitivity mode produces reproducibility of dose measurement with relative standard deviations within 1% of the maximal dose in the beam, if the measurement is made upto 15 cm away from the beam edge. The results have shown that the MOSFET device can adequately measure peripheral doses, which would be beneficial for in vivo dose assessments in radiotherapy.