With the revision of the law in April, 2001, the effective dose at the boundary of the controlled area was set at 1.3 mSv/3M. Whether the shielding capability of the CT room satisfied the provisions ofthe law or not was confirmed by actual measurements. Both thermo luminescence dosemeter (TLD) and electronic dosemeter were used to measure the radiation doses. The shielding capability of the gantry was studied both inside andoutside the room for a week as a basic experiment. On the basis of the data thus obtained doses accumulated in 3 months were estimated. According to the results of 3 month-measurement, the doses outside the wall of the CT room were about 200μSv. This numerical value was comparable to the background level of the evaluation point.The results above assured that the shielding capability of the CT room satisfied the provisions of the law well.
