Computed Tomography

Radiation constraint in Multidetector CT: What can we learn from moving from single to 16 slice CT?

 CM Alvey1 , SJ Mutch2, S Meeson1, and SJ Golding1

1Radiology Group, Nuffield Department of Surgery, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU. 2Department of Medical Physics & Clinical Engineering, Churchill Hospital, Oxford OX3 7LJ, UK.

Superior image quality afforded by newer generations of CT scanners can be used to reduce radiation exposure. CT accounts for nearly 47% of the collective dose and dose constraint is important. Historical dose audit is important guidance as technology advances. The Dose Length Product (DLP) of common uses of CT were compared for four configurations of CT scanners to determine whether the exposure constraint potential of advancing technology was being achieved in practice. These systems were made by the same manufacturer and the aim of the study was to investigate the local DLP implications associated with the replacement of equipment. Upgrading from a single to an 8 slice system led to significant decreases in all examination types except CTPA (CT Pulmonary Angiogram), which had increased DLP. However, upgrading from 4 to 16 slice produced a more varied set of changes, with decreases for Chest and CTPA. Comparing the 8 and 16 slice systems, where the exposure factors and conditions under investigation were the same, DLPs were equivalent. Results show that changing the technology in itself does not automatically reduce the DLP and further work is required to optimise examinations with the aim of further dose constraint.

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