18MVX線治療室の誘導放射線による被ばく線量の推定

抄録

After certain amount of radiation dose were given radioactivity in the parts of the 10MV and 18MV linear accelarators (target, flattening filter and reserch window shield) and the treatment aids of a 18MV linear accelerator was measured using a Ge (Int) detector in a gamma radiation spectrometer system.
Immediately after a 18MV X-ray treatment, the decay curve of a dose equivalent rate a 50cm of distance from isocenter was observed using a survey meter with a X-ray recorder.
At the radiotherapy department in our hospital,8,142 fields were irradiate d in 1994 with a 18MV X-ray (total fields including 6MV and electron modes were 13,534). The exposure to one technologist around the treatment head was estimated to 9654 Sv/year or 19.3g Sv/week assuming 25 working weeks per year with a 18MV X-ray treatment. In a worst case, assuming 50 working weeks and 13,534 total fields with a 18MV X-ray, the exposure was estimated to 114.31.6v/week. This value was considered to be with in the dose limits (i. e.50mSv/year) of effective dose equivalent on ICRP publication 60.