On the CT Dose Index: Are we Meeting the Challenge?

Abstract

The computed tomography dose index (CTDI), has long been recognised as a metric to quantify the radiation output from a CT examination that is easily measured and that captures the majority of the scatter tails for even wide X-ray beam widths. International standards now require manufacturers to display the pitch-normalised metric (CTDIvol) prior to scan initiation and the radiology community has become very familiar to typical values of this metric. However, it has been suggested that modern developments in CT technology permit patient doses to be determined in a more adequate way that allows representing the risks to patients, and that is now time to forgo the use of the CTDI (or variants) for CT dose optimisation. In this work, we explore the main problems concerning the use of the CTDIvol as a relevant dose index through a retrospective study of 20 of the most common CT examinations at a South American imaging centre including adult and paediatric patients using a total of three CT scanners. Applicable results were compared with diagnostic reference levels (DRL’s) from European and North American countries. Our research shows that although CT technology is changing at a quick pace, CTDIvol keeps being a practical and valuable method for the task of dose optimisation because is well established and uniformly adopted.