Assessment of image quality and radiation dose with prospective versus retrospective electrocardiography gated 256-slice coronary CT angiography / 中华放射学杂志

ABSTRACT

Objective To retrospectively compare the image quality and radiation dose for coronary CT angiography obtained with a prospectively gated transverse (PGT) CT technique and a retrospectively gated helical (RGH) CT technique. Methods Coronary CT angiography obtained with 256-slice CT were retrospectively evaluated in 177 patients. The main branches of coronary arteries were divided into 9 segments. The image quality was evaluated with a four-point grading scale. The assessability of coronary artery segment, image quality score and radiation dose for prospective and retrospective CT angiography were compared with student t test. Results The PGT technique was used in 86 patients. The routine RGT technique was used in 91 patients. The percentage of assessable coronary artery segments was 98. 8% (765 of 774)with PGT technique versus 99. 6% (816 of 819) with RGH technique (t = 2. 51, P = 0. 01 ). In patients with heart rates under 75 beats per minute, the image quality of coronary artery branches was similar between PGT and RGH techniques (99. 8% versus 99. 7%, t = 1.90, P > 0. 05 ) . In patients with heart rates above 75 beats per minute, the image quality with RGH technique was better than that with PGT technique (99.0% versus 93. 6%, t = 3.57, P < 0. 05 ). Effective dose with prospective CT angiography was 60. 0% lower than that with retrospective CT angiography [ (4. 4 ± 0. 5 ) vs ( 10. 3 ± 1.5 ) mSv, t = 33.4,P <0. 05 ]. Conclusions Prospective CT angiography can reduce effective radiation dose obviously. The PGT technique offers the similar image quality with RGH technique in patients with heart rates under 75 beats per minute and RGH technique has better image quality in patients with heart rates above 75 beats per minute.