Change in patient doses from radiological examinations at the Vancouver General Hospital, 1991-2002

Much concern has been expressed over the radiation doses and potential harm from x-ray examinations. However, there have been few longitudinal studies in North America. A survey of doses from radiological examinations in Canada was last carried out in 1995. This study was undertaken to estimate the change in the number of patient examinations and patient dose since this last Canadian survey.

The number of radiological examinations and numbers of patients for the years 1991 to 2002 were obtained from workload statistics, which are reported to the Canadian government each year. Radiological examinations were of the following type: general, gastrointestinal or genitourinary, angiography, and computed tomography (CT). Average doses were calculated for each group of examinations.

From 1991 to 2002 there was an increase of 28% in the total number of x-ray examinations performed. The proportion of most types of examination has stayed fairly constant, except for CT, which has increased fourfold in the last 8 years. The striking change is the increased contribution to patient effective dose from CT since 1996, these examinations now comprising nearly 60% of the total patient dose. The average annual effective dose per patient has nearly doubled-from 3.3 mSv in 1991 to 6.0 mSv in 2002.

This paper provides a simple method for any Canadian hospital to estimate the radiation dose to its patients. At the Vancouver General Hospital (VGH), the number of patient examinations has increased by 28%, but the average annual patient effective dose has almost doubled. CT is now by far the largest contributor to patient dose in diagnostic radiology. Efforts need to be made to reduce patient dose by such methods as reduction in unnecessary exams, substitution of nonionizing techniques where possible, and optimization of dose.