Measurements of computed tomography dose index for clinical scans

Abstract

Dose assessment in computed tomography is nowadays based on indicators such as the weighted computed tomography dose index (CTDIw) and the volume-weighted computed tomography dose index (CTDIvol), both measured only on single-axial scans. The aim of this study is to extend the set of CT protocols suitable in CTDIvol,w evaluation and therefore to perform measurements directly on clinical CT scans. With this purpose, the present work follows the methodology proposed by the American Association of Physicists in Medicine in the Report No. 111 and focuses on the central cumulative dose DL(0), which predicts CTDIvol,w values for scan length equal to 100 mm. All measurements performed with ion chamber and gafchromic films suggest that it is possible to achieve accurate CTDIvol,w values without selecting single-axial scans tailored to dosimetry. Therefore, it is not always necessary to split dosimetric and clinical CT scanner set-up.