Survey of clinical doses from computed tomography examinations in the Canadian province of Manitoba

The purpose of this study was to document CT doses for common CT examinations performed throughout the province of Manitoba. Survey forms were sent out to all provincial CT sites. Thirteen out of sixteen (81 ) sites participated. The authors assessed scans of the brain, routine abdomenpelvis, routine chest, sinuses, lumbar spine, low-dose lung nodule studies, CT pulmonary angiograms, CT KUBs, CT colonographies and combination chestabdomenpelvis exams. Sites recorded scanner model, protocol techniques and patient and dose data for 100 consecutive patients who were scanned with any of the aforementioned examinations. Mean effective doses and standard deviations for the province and for individual scanners were computed. The KruskalWallis test was used to compare the variability of effective doses amongst scanners. The t test was used to compare doses and their provincial ranges between newer and older scanners and scanners that used dose saving tools and those that did not. Abdomenpelvis, chest and brain scans accounted for over 70 of scans. Their mean effective doses were 18.06.7, 13.26.4 and 3.01.0 mSv, respectively. Variations in doses amongst scanners were statistically significant. Most examinations were performed at 120 kVp, and no lower kVp was used. Dose variations due to scanner age and use of dose saving tools were not statistically significant. Clinical CT doses in Manitoba are broadly similar to but higher than those reported in other Canadian provinces. Results suggest that further dose reduction can be achieved by modifying scanning techniques, such as using lower kVp. Wide variation in doses amongst different scanners suggests that standardisation of scanning protocols can reduce patient dose. New technological advances, such as dose-reduction software algorithms, can be adopted to reduce patient dose.