Radiology: Volume 249: Number 2—November 2008
Denis Tack, MD, PhD Pierre Alain Gevenois, MD, PhD
In this issue of Radiology, Brink et al (1) contribute an article addressing the effect of arm position on the radiation dose delivered at computed tomography (CT) in trauma patients. In their study, these authors evaluated a method that they developed to estimate radiation dose independently of automatic exposure control (ARC). This method was used to calculate the additional dose incurred when the arm is positioned along the torso or raised away from the torso. Radiation dose is a crucial aspect of radiology, and we commend any efforts to reduce the dose and provide new methods of investigation. As the adequate method for estimating the radiation dose delivered at CT is still a matter of debate (2), we would like to comment on the issue of CT dose measurement, with particular focus on CT dose index (CTDI) and dose-length product (DLP) methods.
As addressed by Brink et al (1), the concern regarding radiation dose is not really new in the literature, despite the recent interest in CT-induced radiation and its measurement. In the early 1990s, when CT examinations were based exclusively on incremental—as opposed to helical—scanning, the issue of CT-induced carcinogenesis came up as a potential problem. It has since been suggested that thousands of patients around the world could potentially die from diagnostic CT-induced cancers every year (3). Since that time, the continuously increasing number of CT examinations performed each year—three times as many examinations were performed in 2004 than in 1994 — has increased the collective carcinogenetic risk (4-7). This risk has been further heightened by the advent of multidetector CT scanners that deliver higher doses of radiation than single-detector scanners (8). (At least, this was the case in the early 2000s.) Technologic improvements on one hand and dose optimization and reduction on the other hand have become essential. Manufacturers have been making substantial efforts to improve technology and have delivered advances such as solid-state detectors, new filters (such as bow tie filters), AEC devices, dose shields that eliminate overranging, and prospective electrocardiographic gating (9). While these improvements have, in principle, enabled substantial dose reductions, estimating the radiation dose has become substantially more complex.