Measurement and theoretical estimation of bremsstrahlung doses in selective internal radiation therapy using 90Y resin microspheres
Objective To determine the external bremsstrahlung doses and doses to radiation workers in selective internal radiation therapy using 90Y resin microspheres(90Y-SIRT).Methods Using an AT1123 X-ray and gamma radiation dosimeter,the ambient dose equivalent rates of bremsstrahlung at distances of 30 and 100 cm from the 90Y drug with and without lead shielding were measured.The attenuation factors of 90Y bremsstrahlung attributed to lead cans and lead aprons were calculated.Furthermore,the dose rates at corresponding sites were theoretically estimated using formula.Finally,the annual doses to radiation workers were estimated based on estimated and measured bremsstrahlung doses.Results The measured dose rates of 90 Y bremsstrahlung ranged from 0.19 to 0.26 μSv·h-1·GBq-1 at a distance of 1 m from the surface of the lead shield and from 1.00 to 1.60 μSv·h-1·GBq-1 at a distance of 1 m from the surface of the unshielded penicillin bottle,plexiglass transport container,injection delivery box,and the patient.The deviations between the calculated and measured bremsstrahlung doses were mostly close to or less than±20％.Under conditions of 200 patients treated annually,3 GBq for each bottle of 90Y resin microspheres,and a maximum dose of 2 GBq per patient,the estimated annual effective doses to nuclear medicine technologists,interventional injection physicians,and ward-round physicians were 2.24,1.04 and 0.22 mSv,respectively,and the annual equivalent doses to their hands were 49.9,25.5 and 2.06 mSv,respectively.The measured attenuation factors of 90Y bremsstrahlung attributed to the lead can of 6.4 mmPb equivalent and the lead apron of 0.5 mmPb equivalent ranged from 0.13 to 0.15 and from 0.45 to 0.50,respectively.Conclusions Under normal working conditions,the annual effective doses to the radiation workers in 90Y-SIRT will not exceed 5 mSv.Wearing personal protective equipment(PPE)or covering the injection sites of patients using a lead apron during 90Y injection can reduce the doses to the workers by approximately 50％.
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