第3代双源CT在大螺距主动脉CT血管成像扫描中的初步应用

Initial Experience of the Application of Third-generation Dual-source CT Scanner in High-pitch Angiography of Aorta

目的评价第3代双源CT在大螺距主动脉CT血管成像(CTA)扫描中的应用价值。方法采用简单随机分组方法将59例临床行全主动脉CTA扫描的患者随机分为两组:(1)组1(n=28):在第3代双源CT上进行扫描,探测器宽度为2×192×0.6 mm,旋转时间为0.25 s。(2)组2(n=31):在第2代双源CT上进行扫描,探测器准直为2×128×0.6 mm,旋转时间为0.28 s。两组患者均采用大螺距心电门控扫描方式进行扫描,螺距3.0,管电压100 kV,管电流采用自动调节技术,参考管电流为288 m A。患者均静脉团注370 mg I/ml的对比剂45 ml,注射速度4.5 ml/s,后续50 ml生理盐水,注射速度5.0 ml/s。扫描采用自动团注跟踪触发技术,选取主动脉起始部放置感兴趣区(ROI),ROI内平均CT值达到100 HU时自动触发扫描,延迟时间6 s。分别计算两组患者主动脉扫描的有效剂量(ED)、图像信噪比(SNR)、对比噪声比(CNR),并对图像质量进行主观评价。结果组1扫描ED为(3.15±0.86)m Sv,较组2的(3.91±0.60)m Sv降低了19.44%(t=-3.989,P=0.000)。两组主动脉各部位的SNR及CNR差异均无统计学意义(P均>0.05)。两组图像主观质量评分差异也无统计学意义[(1.39±0.50)分比(1.45±0.51)分;W=814.5,P=0.651]。结论与第2代双源CT相比,第3代双源CT进行大螺距主动脉CTA扫描能够在保证图像质量的同时,显著降低放射剂量。

Objective To evaluate the value of third-generation dual-source CT scanner in application of high-pitch aorta CT angiography（ CTA）. Methods Totally 59 patients clinically indicated for whole aorta angiography were divided into 2 groups using a simple random method： in group 1 there were 28 patients who underwent the examination on a third-generation dual-source CT device, with a collimation of 2 × 192 × 0. 6 mm and a rotation time of 0. 25 s; in group 2 there were 31 patients who underwent the examination on a second generation dual-source CT device, with a collimation of 2 × 128 × 0. 6 mm and a rotation time of 0. 28 s. Both groups were given the examination operated in dual-source high-pitch ECG-gating mode with a pitch of 3. 0, a tube volt-age of 100 kV, and automated tube current modulation using a reference tube current of 288 m A. A contrast material bolus of 45 ml with a flow of 4. 5 ml / s followed by a 50 ml saline chaser in 5. 0 ml / s was used. CTA scan was automatically started using a bolus tracking technique at the level of the original part of aorta after a trigger threshold of 100 HU was reached. The start delay was set to 6 s in both groups. Effective dose（ ED）,signal to noise ratio（SNR）,contrast to noise ratio（CNR）,and subjective diagnostic quality of both groups were evaluated. Results The mean ED were 19. 44% lower（ t =- 3. 989,P = 0. 000） in group 1 [（ 3. 15 ± 0. 86） m Sv] than in group 2[（3. 91 ± 0. 60） m Sv]. These two groups showed no significant differences in SNR or CNR（all P〉0. 05）.The subjective diagnostic quality values also showed no significant difference between two groups [（ 1. 39 ± 0. 50）scores vs.（ 1. 45 ± 0. 51） scores; W = 814. 5, P = 0. 651]. Conclusion Compared with the second-generation dual-source CT scanner, the third-generation dual-source CT scanner in whole aorta CTA can remarkably reduce the radiation dose without affecting image quality.