Radiation exposure in computed tomography

The axial dose profile of various scans of different CTs was determined to obtain specification on radiation geometry by collimation. The dose was measured "free-in-air" by thermoluminescent dosimeters at the axis of rotation. Considerable differences between the various CTs were observed. The scans of different CTs had narrow and wide fields. It seems to be possible to reduce the energy transmitted to the body by appropriate collimation.