Patient doses in multi-slice CT and the importance of optimisation

Abstract

Substantive surveys of patient doses arising from CT examinations have been conducted in our Hospital. In the first instance doses were measured on a single-slice Siemens Plus 4 scanner. A similar survey was conducted initially following commissioning of a Siemens multi-slice Sensation scanner and subsequently after some effort was made to optimise scanning protocols. Doses are reported in terms of dose-length products (DLPs) and as effective doses. The optimisation process on the multi-slice scanner resulted in a reduction in DLP values by between 14% and 58%. With two exceptions, significantly lower or comparable DLP values were obtained when meaningful comparisons were made with results previously obtained with the single-slice scanner. Specific results for the multi-slice scanner in terms of the median DLP in mGy.cm (and median effective dose in mSv) are: routine brain, 660 (1.5); routine chest, 195 (4.0); chest with portal liver phase, 370 (7.2); routine chest with high resolution component, 250 (5.1); chest/abdomen/pelvis with contrast, 560 (11.0); routine abdomen without contrast, 145 (2.4); routine abdomen with contrast 215 (3.6); routine abdomen/pelvis without contrast, 230 (4.4); routine abdomen/pelvis with contrast, 345 (6.3); abdomen/pelvis triple phase, 715 (13.3); renal scan, 260 (4.6); lumbar spine, 445 (7.2); cerebral angiography, 240 (0.58); pulmonary angiography, 165 (3.4); aortic angiography, 305 (5.7). Based on the survey findings possible values for CT examination local diagnostic reference levels (LDRLs) are suggested.

Patient dose considerations in computed tomography examinations

“…In the literature, there are many papers on patient doses in CT reporting results of small or large scale surveys carried out in CT facilities throughout the world [6,12,22,23,[31][32][33][34][35] . When comparing the DLP values given in these reports for typical CT examinations, it can be seen that large differences exist among CT facilities.…”

Radiation protection in Australia: a thirty year perspective

“…In Victoria, the Radiation Safety Unit of the Department of Human Services used the results that they had obtained in dose surveys to establish guidance levels (the term used by the IAEA for DRLs) for common procedures (both paediatric and adult) in terms of the skin entrance dose or CTDI w 44 . Heggie 45 has surveyed the patient doses in multi-slice CT and derived DRLs for a range of common examinations based on the dose-length product.…”

Technical developments in radiology in Australasia dating from 1977

“…The term exposure creep has been coined to describe this behaviour 5,49,50 . CT is probably the most crucial, in that respect, given the magnitude of the organ doses that patients may receive, most particularly from multi-phasic procedures and techniques for optimization have been discussed in the literature [51][52][53][54][55][56] .…”