Measurements and assessment of radiation levels at the radiotherapy site of the first domestic single-vault proton therapy system
Objective To measure and assess relevant radiation doses at the radiotherapy site of the first domestic single-vault proton therapy system.Methods The radiation levels of the therapy system during and after beam irradiation were measured,and annual effective doses were assessed for personnel at the site.Results During beam irradiation,the highest radiation dose was detected at the shielded door of the equipment floor,with a gamma radiation level of 2.140 μSv/h and a neutron radiation level of 0.850 μSv/h.Neutron radiation disappeared immediately once the beams stopped.In contrast,the radiation activated originated mostly from gamma rays.A longer time after beams stopped was associated with lower induced radiation intensity at the same location.Furthermore,a farther distance from the irradiated object corresponded to lower induced radiation intensity at the same time.The assessment result reveal that the annual effective doses to the personnel were at the safe level,with physicists exposed to the highest dose of 2.138 mSv.Conclusions The radiation level at the studied proton therapy site meets the safety requirement,and the treatment can be performed safely at this site.
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