Radioactivity in Blood Induced by a Medical Betatron

Quantitative Analysis Using a Monte Carlo Method

Abstract

The radioactivity in the blood induced by 17.9MeV and 24.5MeV electron beams from a medical betatron was investigated from the point of view of considering the effect of the radioactivation of patients on the patients themselves. It was evaluated by gamma ray spectrometry using a NaI(Tl) detector. The full-energy peak efficiency for 511keV gamma rays from thick cylindrical blood sources was calculated using a Monte Carlo method. From it and the full-energy peak area of the blood spectrum, the radioactive concentration of the blood was obtained for the irradiation of 30min. The activity reduced to half the value at the end of the irradiation after about 138sec. The estimate of the whole body dose from the blood suggested that the activity in the patients induced by the betatron will cause very little harm to the patients.