SPECT bone scanning requires patients with injection of 99m Tc radioactive drug. Patients stayed in SPECT drawing room for three hours after injection to protect the public safety. But discharged patients could bring radiation impact to public if there was no pro_tection measures. So it’s necessary to estimate the radiation effective dose of public. 451P radiation dosimeter was used to measure external air absorption dose rate for discharged pa_tients. Then Mountford method to estimate the radiation effective dose of public. The esti_mation re...