256层CT心电前置门控及回顾门控冠状动脉成像质量及辐射剂量比较

目的 比较256层CT前置门控冠状动脉CTA与回顾门控检查方法的成像质量及辐射剂量,探讨256层CT前置门控冠状动脉扫描方法的临床应用价值及局限性.方法 回顾分析177例冠状动脉256层CTA检查患者,其中前置门控86例,回顾门控91例.将冠状动脉主要分支分为9个节段评价,采用4分法评价图像质量,≥3分为可评价节段.采用t检验比较两种方法组可评价节段的百分比、患者的有效辐射剂量及图像噪声.结果 前置门控组86例中98.8%节段(765/774)为可评价节段.回顾门控组91例中99.6%节段(816/819)可评价.2组图像质量差异有统计学意义(t=2.51,P=0.01).心率<75次/min时,前置门控与回顾门控组的可评价节段分别为99.8%(647/648),99.7%(718/720),图像质量的差异无统计学意义(t=1.90,P>0.05).≥75次/min时,2组的可评价节段分别为93.6%(118/126)和99.0%(98/99).2组的可评价率差异有统计学意义(t=3.57,P<0.05).前置门控组及回顾门控组的有效辐射剂量分别为(4.4±0.5)和(10.3±1.5)mSv(t=33.4,P<0.00),前置门控扫描的剂量明显小于回顾门控扫描,下降幅度达60.0%.结论 256层CT前置门控冠状动脉扫描方法较回顾门控方法剂量显著降低,两种扫描方法得到的图像质量均较好.在低心率组图像质量两种方法相近,而高心率组前置门控较回顾门控法有差距.

Assessment of image quality and radiation dose with prospective versus retrospective electrocardiography gated 256-slice coronary CT angiography

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.