双源CT主动脉夹层扫描方案探讨

Scanning protocol of dual-source computed tomography for aortic dissection

目的探讨双源CT主动脉夹层大范围扫描方案,寻找一种影像质量高、辐射剂量低的扫描方案。方法连续收集临床怀疑主动脉夹层的病人120例,随机分为3组,每组40例。A组采用前瞻性心电触发大螺距扫描(FLASH方案)进行CTA检查,B组采用回顾性心电触发螺旋扫描,C组采用常规非心电触发螺旋扫描方式进行扫描,评价3种扫描方案的影像质量及辐射剂量。结果 A组影像质量评为1、2、3级者分别为17例、22例和1例,无评为4级者;B组影像质量评为1、2级者分别为33例、7例,无评为3、4级者;C组影像质量评为3级、4级者分别为14例和26例;无评为1、2级者。A、B组影像质量评分无差别;A、B组均较C组有明显优势。A、B、C3组平均有效辐射剂量分别为(7.70±0.40)mSv、(33.11±3.38)mSv、(7.60±0.68)mSv。B组明显高于其他两组(P均<0.05),其他两组比较差异无统计学意义(P=0.826)。结论主动脉夹层大范围扫描首选前瞻性心电触发大螺距扫描(FLASH方案),影像质量高,辐射剂量低;常规非心电触发螺旋扫描方式可选择性地用于StanfordB型主动脉夹层。

Objective To find a dual-source CT scanning protocol whice can obtain high image quality with low radiation dose for diognosis of aortic dissection. Methods Total 120 patients with suspected aortic dissection were randomly and equally assigned into three groups. Patients in Group A were performed CTA exam with prospectively electrocardiogramgated high pitch spiral mode （FLASH）. Patients in Group B were performed CTA exam with retrospective electrocardiogramgated spiral mode. Patients in Group C were performed CTA exam with conventional mode which no electrocardiogram-gated. The image quality, radiation dose, advantages and disadvantages among the three scan protocol were analyzed. Results For image quality, seventeen, twenty two and one patients in group A were granted to grade 1, 2, 3 respectively, and none was in grade 4; thirty three and seven patients in group B were granted to grade 1, 2, respectively, and none was in grade 3 and 4; fourteen and twenty six patients in group C were granted to grade 3, 4, respectively, and none was in grade 1 and 2. There was no significant difference between group A and B in image quality. Compared with the image quality, Group A and B were significantly higher than Group C. Mean effective radiation dose of Group A, B and C were 7.7±0.4 mSv, 33.11±3.38 mSv, and 7.6±0.68 mSv, respectively. Group B was significantly higher than Groups A and C （P＆lt;0.05, P＆lt;0.05, respectively）, and there was no significant difference between Group A and C （P=0.826）. Conclusions Prospectively electrocardiogram-gated high pitch spiral mode can be the first line protocol for evaluation of aortic dissection. It can achieve high image quality with low radiation dose. Conventional mode with no electrocardiogram-gated can be selectively used for Stanford B aortic dissection.