Abstract
Potential risks from radiation exposure on the development of cardiovascular and cerebrovascular disease are indicated by epidemiological studies. Medical exposures give the largest dose to the population from artificial sources, with cumulative doses from multiple CT scans being significant. Data on doses from scans performed on 12 CT scanners in three hospitals over a period of 5½ years, derived using RadimetricsTM software, have been reviewed for 105 757 patients. Data have been downloaded for heart, brain, thyroid, and effective doses, and cumulative doses analysed using ExcelTM spreadsheets. 2.4% of patients having body CT scans received cumulative doses to the heart over 100 mSv, 9% of whom were under 50 years. 9.6% of patients having head CT scans received cumulative doses to the brain over 100 mSv with 0.08% over 500 mSv from whom 41% were under 50 years, but only 1.3% of patients scanned had thyroid/carotid artery doses over 100 mSv. An approximate evaluation of potential risks from exposures of the heart above 100 mSv and brain over 500 mSv for patients under 60 years would suggest that at most only one patient would demonstrate any excess risk from vascular disease resulting from the exposures. 0.67% of patients scanned received effective doses over 100 mSv, in line with results from European studies, with 8.4% being under 50 years. The application of age and sex specific risk coefficients relating to excess cancer incidence suggests that two or three patients with effective doses over 100 mSv and five patients with effective doses between 50 and 100 mSv, from those examined, might develop cancer as a result of exposure. However, this will be an overestimate, since it does not take patients’ health into account. Exposure management software can aid in evaluating cumulative doses and identifying individual patients receiving substantial doses from repetitive imaging.
Highlights
Heart and circulatory diseases account for just over 25% of deaths in the UK each year
Doses to the relevant organs from all scans performed were summed for each patient, and separate sets for each organ were ordered according to dose levels so that numbers of patients receiving doses within given ranges could be identified for each organ. 5609 patients received cumulative doses to the brain of over 100 mGy from computed tomography (CT) head scans, 1545 received cumulative heart doses over 100 mGy from body scans, and 1426 received thyroid doses over 100 mGy
The cumulative effective doses received by patients were analysed to allow comparison with studies performed in other parts of the world
Summary
Heart and circulatory diseases account for just over 25% of deaths in the UK each year. Examples from recent studies include increases in ischaemic heart disease in women treated for breast cancer [5], in coronary heart disease for patients receiving treatment for Hodgkins lymphoma [6], in cardiac mortality among patients receiving radiotherapy for treatment of the oesophagus [7], and in the incidence of grade 3 cardiac events, namely acute coronary syndrome events or congestive heart failure, among patients receiving radiotherapy for lung cancer [8] These studies report that risks are significantly higher among individuals with pre-existing cardiac disease. Based on the evidence available, ICRP 118 concluded that there are excess risks of heart disease for patients given radiotherapy that results in acute heart doses of 1 to 2 Gy with the excess risks becoming apparent 10–20 years after exposure, but there may not be a dose threshold below which no effect occurs [2]
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