Effect of CT scan protocols on x-ray-induced DNA double-strand breaks in blood lymphocytes of patients undergoing coronary CT angiography

To compare in vivo DNA lesions induced during helical and sequential coronary computed tomography angiography (CTA) and to evaluate the effect of CT parameters on double-strand break (DSB) levels. Thirty-six patients were examined with various CT protocols and modes (helical scan, n = 27; sequential scan, n = 9) either using a 64-slice dual-source or a 128-slice CT system. Blood samples were obtained before and 30 min after CT. Lymphocytes were isolated, stained against the phosphorylated histone variant gamma-H2AX, and DSBs were visualised by using fluorescence microscopy. DSB yields 30 min after CTA ranged from 0.04 to 0.71 per cell and showed a significant correlation to DLP (rho = 0.81, p < 0.00001). Median DSB yield and median DLP were significantly lower after sequential compared to helical CT examinations (0.11 vs. 0.37 DSBs/cell and 249 vs. 958 mGy cm, p < 0.00001). Additional calcium scoring led to an increase in DLP (p = 0.15) and DSB levels (p = 0.04). DSB levels normalised to the DLP showed a significant correlation to the attenuation of the blood (rho = 0.53, p = 0.01) and a negative correlation to the body mass index of the patients (rho = -0.37, p = 0.06). gamma-H2AX immunofluorescence microscopy allows one to determine dose-related effects on x-ray-induced DSB levels and to consider individual factors which cannot be monitored by physical dose measurements.