An automated access management system to the controlled sickrooms for 125I brachytherapy was developed. The system consists of access control and video surveillance units. The patients implanted 125I seeds were isolated for about 20 h after surgery in the controlled sickrooms. The maximum doses and dose rates of the nurses and visitors were estimated by using the legal upper limit activity of 1, 300 MB q, the measured longest staying time, and the shortest distance between the patients and individuals. Video analysis revealed activities of the nurses, patients, and visitors in the controlled sickroom, and relationships between the access frequency and staying time. The nurses' measured doses ranged from 1 to 3, μ S v, and averaged 1.6 μ Sv. The nurses' maximum dose and dose rate were 16, μ Sv and 5.6 nSv·h-1·EMBq-1. The visitors' maximum dose and dose rate were 6 μ Sv and 2.6 n Sv·Eh-1·EMBq-1. The nurses and visitors' exposure doses per patient were estimated to be negligible compared with the annual limit of the public.
We investigated the response function of a Schottky CdTe detector with a guard-ring cathode through Monte Carlo calculation using the MCNP code and measurement in order to apply the detector for the analysis of X-and γ-Aray spectra in medical radio-iagnostic units for quality assurance and quality control of the systems. The CdTe detector has high potential as an X-dand γ-A-ray spectrometer owing to compactness due to a large photon absorption cross section and high energy resolution. We measured the detector response function for various operating conditions, i. e., bias voltage and shaping time using an 241Am source to find the optimum operating condition, and then measured the detector responses and full energy absorption efficiency for 241Am, 152Eu, 133Ba and finally compared with the calculation. The experimental response functions are well reproduced by the MCNP code except for the part of the low energy tail due to charge trapping effect.
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