Radiation exposure and image quality in staged low-dose protocols for coronary dual-source CT angiography: a randomized comparison

To evaluate staged low-dose approaches for coronary CT angiography (CTA) in which a standard sequence was added if the low-dose sequence did not allow reliable rule-out of coronary stenosis. A total of 176 consecutive patients referred for dual-source CTA were randomized to three protocols: group 1 using prospective ECG-triggering (100 kV, 330 mAs), group 2 a retrospectively gated "MinDose" sequence (100 kV, 330 mAs) and group 3 a standard spiral sequence (120 kV, 400 mAs). If image quality in low-dose groups 1 or 2 was non-diagnostic, an additional standard CT examination (as in group 3) was performed. Non-diagnostic image quality was found in 11/56, 4/55, and 2/65 patients (46/896, 4/880 and 3/1,040 coronary segments) in groups 1, 2 and 3, respectively. Median (interquartile ranges) volumes of contrast material, CTDI(vol), DLP and effective dose for low-dose groups 1 and 2 and for standard group 3 were 92.5 (11.3), 75.0 (2.5) and 75.0 (9.0) ml; 8.0 (1.4), 16.8 (4.8) and 48.1 (14.2) mGy; 108.0 (27.3), 246.0 (93.0) and 701.0 (207.8) mGy cm; and 1.5 (0.4), 3.4 (1.3) and 9.8 (2.9) mSv, respectively. A staged coronary CTA protocol with an initial low-dose approach and addition of a standard sequence-should image quality be too low-can lead to a substantial reduction in radiation exposure.