Dose distribution of scattered X-rays in computed tomography

Scattered X-ray doses and distribution in mandible- and maxillo-facial CT scanning were examined using phantoms. Scattered X-ray doses ranged from 9.87 mR at 50 cm away from the center of the gantry rotation to 0 mR just at the lateral margin of the gantry. They became lower with distance away from the center of the gantry rotation. They were relatively lower in the direction corresponding to the longitudinal axis of the patient's table, and tended to be higher in the direction 45 deg C to the horizontal plane. They tended to be larger in the anterior than posterior parts of the gantry. The thinner the slices were, the lower scattered X-ray doses were. (Namekawa, K)