Abstract

Health hazards are associated with medical exposures to ionizing radiation, including during Computed Tomography (CT) procedures. Rapidly increasing number of CT facilities worldwide is accompanied by enhanced staff, patient and public radiation doses and these needs to be controlled to minimize health risks. This paper reviews the relevant patient and CT scanning parameters that influence patient dose during the common diagnostic procedures. These include scanning geometry, tube current, applied high potential (kVp), scanning mode and length, collimation, couch speed and pitch, gantry rotation speed and radiation shielding. The paper also presents some strategies for limiting patient dose through modulation of exposure parameters and design of technical devices for image processing. These include collimation, filtration, automated modulation of tube current, use of adaptive reconstruction and noise filters. Patient weight and size of the scanned anatomical part influence the absorbed dose, x-ray beam collimation and filtration can reduce dose by 17% to 50%, tube current modulation can lead to 10% to 60% reduction, projection adaptive reconstruction filter can reduce dose by 30% to 60% while noise filters can produce 17% reduction in noise variance compared with the conventional filters.

Key phrases: Computerized Tomography, Patient Dose Reduction; Scanning Parameters Modulation.