DNA double-strand breaks as potential indicators for the biological effects of ionising radiation exposure from cardiac CT and conventional coronary angiography: A randomised, controlled study

Objectives To prospectively compare induced DNA doublestrand breaks by cardiac computed tomography (CT) and conventional coronary angiography (CCA). Methods 56 patients with suspected coronary artery disease were randomised to undergo either CCA or cardiac CT. DNA double-strand breaks were assessed in fluorescence microscopy of blood lymphocytes as indicators of the biological effects of radiation exposure. Radiation doses were estimated using dose-length product (DLP) and dose-area product (DAP) with conversion factors for CT and CCA, respectively. Results On average there were 0.12±0.06 induced doublestrand breaks per lymphocyte for CT and 0.29±0.18 for diagnostic CCA (P<0.001). This relative biological effect of ionising radiation from CCA was 1.9 times higher (P< 0.001) than the effective dose estimated by conversion factors would have suggested. The correlation between the biological effects and the estimated radiation doses was excellent for CT (r00.951, P<0.001) and moderate to good for CCA (r00.862, P<0.001). One day after radiation, a complete repair of double-strand breaks to background levels was found in both groups. Conclusions Conversion factors may underestimate the relative biological effects of ionising radiation from CCA. DNA double-strand break assessment may provide a strategy for individualised assessments of radiation. Key Points ̇ Radiation dose causes concern for both conventional coronary angiography and cardiac CT. ̇ Estimations of the biological effects of ionising radiation may become feasible. ̇ Fewer DNA double-strand breaks are induced by cardiac CT than CCA. ̇ Conversion factors may underestimate the relative effects of ionising radiation from CCA.