第二代双源CT前门控FLASH扫描与序列扫描冠状动脉成像比较

Comparison of prospectively ECG-triggered high-pitch spiral and sequential acquisition for coronary CT angiography using the second generation of dual-source CT

目的:比较第二代双源CT前门控大螺距螺旋扫描(FLASH扫描)与序列扫描模式在冠状动脉CT成像中的图像质量及辐射剂量。方法:回顾性分析采用第二代双源CT行前门控FIASH扫描(A组)与序列扫描(B组)冠状动脉CTA连续各50例患者,入组标准为心率70次/min以下,窦性心律,心率波动范围在10次/min以内。评价这2种成像模式的图像质量及辐射剂量。扫描参数:2组均采用Z轴飞焦点技术采集,探测器准直宽度0.6 mm,重建层厚0.75 mm,扫描时间0.28 s/r,单扇区时间分辨率75 ms,根据患者体质量指数(BMI)值设定管电压:100kV(BMI<24 kg/m^2)、120 kV(BMI≥24 kg/m^2),参考管电流370 mAs,采用管电流调制方案;FLASH扫描前门控心电触发选在60%R-R间期,螺距3.4;序列扫描采集时相为35%～75%R-R间期,步进采集宽度34.5 mm。冠状动脉图像质量分为4级(1级为优异,1～3级为可评价血管,4级为不可评价血管),相应评为1～4分。应用秩和检验比较2组患者冠状动脉段图像质量评分,应用两独立样本t检验比较2组患者所接受的辐射剂量。结果:A、B 2组患者的年龄及BMI差异无统计学意义。A、B 2组可评价的冠状动脉节段百分比分别为98.21%和98.56%,差异无统计学意义(χ~2=0.244,P=0.621),平均图像质量评分分别为1.30±0.60和1.28±0.56,差异无统计学意义(Z=-0.489,P=0.625)。A、B 2组扫描的平均有效辐射剂量分别为(0.99±0.34)mSv和(4.80±2.21)mSv,差异有统计学意义(t=-12.048,P=0.000),FLASH扫描剂量明显低于序列扫描。结论:在心率低于70次/min、心律稳定的情况下,第二代双源CT前门控FLASH扫描可获得与序列扫描相似的高质量图像,但辐射剂量明显降低。

Objective： Prospective high pitch acquisition in cardiac imaging allows to obtain the images with lose dose, which however has not been studied comprehensively. The aim of this study was to compare prospective high-pitch spiral （FLASH） and the sequential acquisitions in coronary CT angiography using the 2nd generation of dual-source CT. Methods： One hundred subjects with suspected coronary artery disease with heart rate ≤70 bpm and heart rate fluctuation less than 10 bpm underwent coronary CTA on the 2nd generation of dual-source CT. Subjects were divided into two groups with different acquisitions randomly. Prospective ECG-triggering coronary CT angiography protocol： Using a z-flying focal spot; the simultaneous acquisition of data in 0.6 mm; reconstruction slice thickness 0.75 mm; rotation time 0.28 s; Using single-cycle reconstruction, a temporal resolution of 75 ms; tube settings were 100 kV（BMI（24 kg/m^2） and 120 kV（BMI≥24 kg/m^2 ）. The additional parameters for FI.ASH was data acquisition obtained at 60%of the R-R interval, whereas 35% -75% of the R-R interval for sequential scan. Image quality （IQ） was evaluated using a four-point scale （1 = excellent, 4= unevaluable） by two experienced radiologists by consensus. The rank sum test was used to compare the image quality between two groups. T-test was used to compare the radiation dose between two groups. Results： All subjects performed scans successfully. FLASH yielded good IQ in 98.21%, and sequential in 98.56 %. There was no significant difference in mean IQ score between groups （1.30±0.60 vs. 1.28!0.56, P =0. 625）. While there was significant difference in the mean effective radiation dose （0.99±0.34 vs. 4.80±2.21 mSv, P =0. 000）. Conclusion： Compared with the sequential acquisition, the prospective high-pitch spiral scan can remarkably reduce radiation dose while preserving good image quality in patients with a low and stable heart rate （≥70 bpm）.