X-ray induced DNA double-strand breaks in coronary CT angiography: Comparison of sequential, low-pitch helical and high-pitch helical data acquisition

Background: Aim of this study was to compare DNA double-strand breaks (DSBs) in blood lymphocytes of patients undergoing high-pitch helical, low-pitch helical and sequential coronary CT angiography. Methods and results: 66 patients were examined with various scan protocols and modes (low-pitch helical scan: 100-120 kV, 320-438 mAs/rot, pitch 0.18-0.39, with or without ECG-pulsing, n = 35; prospectively ECG-triggered high-pitch helical scan: 100-120 kV, 320-456 mAs/rotation, pitch 3.2-3.4, n = 19; prospectively ECG-triggered sequential scan: 100-120 kV, 150-300 mAs or 320-370 mAs/rotation, n = 12) either using a 64-slice or 128-slice dual-source CT or a 128-slice single source CT scanner. Blood samples were obtained before and 30 min after CT and DSBs were analyzed in isolated lymphocytes using gamma-H2AX immunofluorescence microscopy. A significant increase of DSBs was measurable 30 min after CTA (range 0.01-0.71/cell). CT induced DSBs showed a significant correlation with the estimated effective dose (rho = 0.90, p < 0.00001). Both prospectively ECG-triggered sequential (0.10 DSBs/cell, 176 mGy cm, p < 0.00001) and high-pitch helical scan protocols (0.03 DSBs/cell, 109 mGy cm, p < 0.00001) led to a significant reduction of median DLP and DSB levels compared to low-pitch helical scans (0.34 DSBs/cell, 828 mGy cm). A reduction of the tube voltage resulted in significantly lower whereas additional calcium scoring resulted in elevated DLP and DNA damages (p < 0.05 each). Conclusion: In coronary CTA, data acquisition protocols have a significant influence on the X-ray induced DSB levels. Using gamma-H2AX immunofluorescence microscopy different scan modes in different CT generations can be compared concerning their biological impact. (C) 2011 Elsevier Ireland Ltd. All rights reserved.