Jonathan McNulty, Presenter: Nothing to Disclose

Pádraig Ivory BSc, Abstract Co-Author: Nothing to Disclose

A phantom based investigation into the potential of direct radiography (DR) to reduce patient dose for abdominal and pelvic radiography examinations. Previous DR studies have shown dose reductions for chest and extremity radiography. Despite this there remains a lack of studies investigating DR abdominal and pelvic examinations or indeed studies comparing regions of low inherent contrast to regions of high inherent contrast.

For each region 42 images were produced using an anthropomorphic phantom and an amorphous silicon flat-panel detector system (84 in total) over a range of kVp and mAs values. The individual dose-area product (DAP) readings were recorded over the entire exposure range. All images were scored by three experienced viewers using a range of image quality criteria following a well-established system. Intra-observer and inter-observer variability/consistency were tested statistically (Mann-Whitney U). Mean effective dose (ED) values were calculated from the recorded DAPs. Both the image quality scores and ED values were analysed in order to investigate the potential dose reduction.

When compared with the maximum Commission of European communities effective dose values, dose reductions approaching 85% for both the pelvic and abdominal examinations were found. Appropriate kVp and mAs selection allowed lower doses to be utilised while maintaining image quality. Dose reductions for the pelvis were found to exceed those of the abdomen by 20%. This percentage difference was demonstrated both for images of high diagnostic efficacy and for images of lower diagnostic efficacy.

The potential for direct radiography to reduce ED varied between the abdomen and pelvis. It is suggested that this is due to the differences in their inherent anatomical subject contrast (pelvis - inherently high contrast; abdomen - inherently low contrast) and varying image contrast requirements. A further clinical study should be developed prior to addressing current recommendations.

This study demonstrates the importance of dose-image optimising for DR and highlights the need for systems to be optimised on a region-by-region basis in order maximise potential dose reductions.

McNulty, J, Ivory, P, Dose-Image Optimisation of Pelvic and Abdominal Examinations Using Direct Radiography: A Phantom-based Study.  Radiological Society of North America 2007 Scientific Assembly and Annual Meeting, November 25 - November 30, 2007 ,Chicago IL. http://archive.rsna.org/2007/5006819.html