The radiation protection system for an operator in percutaneous coronary intervention (PCI) was examined bymeasuring scattered radiation in two X-ray projections (LAO (left anterior oblique) -60; RAO (right anterior oblique) -30) while a movable radiation shield being used for protection. The dose reduction rate and the scattered radiation doserate at the operator's standing position were determined.The effects and problems of the movable radiation shieldwere identified. Use of the movable radiation shield was demonstrated to be effective in decreasing the radiationexposure to the operator.However, experimental results confirmed the following new findings, which differ from theconventional understandings. 1) At the standing position of the operator, the scattered radiation dose rate in an areaadjacent to the floor increases with use of the movable radiation shield. This dose increase is greater in the LAO-60 projection than in the RAO-30 projection. 2) The scattered radiation dose rate around the head and neck is higher atthe standing position of an assistant than at that of the operator. 3) Even at distant positions from the water phantom, high scattered radiation dose rates are observed in areas which are not blocked by the movable radiation shield. Theresults indicated that the manager of medical facilities should first comprehensively grasp the positional relationshipof a protection board, an X-ray tube, and an operator of PCI, and then take the reasonable radiation protection systemwhich is based on the dose reduction rate and the scattered radiation dose rate.

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A high sensitive ¹²³I thyroid uptake measurement method was devised by using an imaging plate and a bio imaginganalyzer system (IP system).The IP system gives an image reflecting thyroid outline.The IP system can detectthe thyroid activity of 600 Bq corresponding to 5% uptake 24 hr after administration of 42 kBq within an uncertaintyof 5%.The thyroid uptake study using IP system can be conducted by administrating the 1.1% activity of 3.7 MBqrequired for the NaI system in accordance with the guideline recommended by The Society of Nuclear Medicine.Thethyroid-absorbed dose for a normal adult administered 42 kBq was 0.13 mGy, that is comparable to the equivalentdose of the thyroid of 0.1 mGy due to the chest X-ray examination at the guidance level of 0.4 mGy recommended by IAEA.The PSL value-activity conversion coefficient was 6.0×10^-3±0.15×10^-3 PSL.sec^-1.Bq^-1.

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