高心率患者640层CT冠状动脉成像窄窗技术可行性研究及其对辐射剂量的影响

Feasibility Study of Coronary Artery Angiography and Impact of Radiation Dose in Patients with High Rate by 640-slice CT Narrow Window Technology

目的探讨高心律患者640层CT冠状动脉成像使用前瞻性心电门控窄窗技术的可行性及其对辐射剂量的影响。方法搜集静息心率≥80次/分的30例患者按厂家设定的标准扫描方案(心率≥80次/分的采集时相为R-R间期30%～80%之间,采集3～4个心动周期)进行扫描,所得数据以CT机自动设置75%R-R间期作为相对重建时相,自动选择最佳时相进行容积重建所得冠脉图像作为对照组(A组)。另对A组CT机扫描采集数据进行回顾性心电门控重建,以2%为间期,重建R-R间期30%～50%数据所得冠脉图像作为研究组(B组)。A组辐射剂量值由CT机自动计算得出,B组辐射剂量值以A组相同扫描参数输入CT机后模拟获得。最终由2名高年资医师选择最佳时相按4级质量评分法对两组冠脉节段图像质量进行评价并分析模拟窄窗技术对辐射剂量的影响。结果 A,B两组平均图像质量评分随扫描心率增加呈线性增加(y=0.451+0.012x,t=3.174,P=0.004),当实时扫描心率>91次/分时,B组的图像质量优于A组图像质量。A,B两组平均图像质量评分随扫描中心率波动增加呈线性增加(y=1.308+0.039x,t=3.737,P=0.001),当扫描中心率波动<5次时,B组的图像质量优于A组图像质量。A组与B组之间总冠状动脉图像质量的优良率无统计学差异(χ2=2.611,P=0.135),两组之间的冠脉节段可评价数无统计学差异(χ2=0.078,P=0.789)。A组与B组辐射剂量指标CTDLvol、DLP、ED对比差异有统计学意义(t=5.036、5.347、5.347,P<0.001)。研究组的CTDLvol、DLP较对照组分别下降29.39%和32.62%,A组与B组平均辐射剂量分别为13.15±3.28、8.86±2.92mSv,B组辐射剂量值较A组下降32.62%。结论 640层CT在对高心率患者冠脉CT检查中运用前门控窄窗技术能保证冠状动脉图像的诊断需求,同时能有效降低患者吸收剂量,值得推广。

Objective To investigate the feasibility of coronary artery angiography and impact of radiation dose in patients with high rate by ECG - gated 640 - slice CT narrow window technology prospectively. Methods Thirty patients with heart rate 〉i 80bpm were collected. Three cardiac cycle beat during 30% to 80% of the R - R interval were scanned according to standard protocols by the vendor. The obtained data were automatically reconstructed at 75% R - R interval phase. The absolute time method was then adopted for automatically selecting the best phase to reconstruct volume and the obtained coronary images as the control group （Group A）. The data in group A were retrospectively reconstructed and then they were reconstructed by 5% steps from 30% to 50% of the R - R interval. The obtained images of coronary arteries were considered as study group （ Group B）. The radiation dose of Group A were automatically calculated by the CT, while the radiation dose of Group B were obtained by simulating the same type of CT scanning parameters of Group A. Finally, the best phase was selected by two senior physicians. The two groups of coronary artery images were then evaluated according to four segments methods. The impacts of narrow window technology on the radiation dose values were analyzed and simulated. Results The image quality was significantly affected by real time heart rate（y =0.451 ＋0.012x,t = 3. 174 ,P 〈0.01 ）. The image quality of the group B was better than the A group when the real -time scanning heart rate 〉 91bpm. The image quality was significantly affected by heart rate fluctuations （ y = 1. 308 ＋ 0. 039x, t = 3. 737,P 〈 0.01 ）. The image quality of the group B was better than group A when the scan fluctuations in heart rate 〈 5. No significant difference was found for image quality scale of coronary artery between Group A and Group B （χ2 = 2. 611, P = 0. 135）. No significant difference was found for score of coronary artery segments between Group A and Group B （χ2 = 0. 078, P = 0. 789）. A statistically significant difference was shown in radiation dose index CTDLvol, DLP, ED between Group A and Group B （ t = 5. 036, 5. 347, 5. 347 respectively, P 〈 0. 001 ）. The CTDLvol and DLP values of Group B were decreased by 29.39% and 32.62% compared with the control group A respectively. Group A and Group B had the average radiation dose of 13.15 ± 3.28mSv and 8.86 ±2.92mSv, respectively. The radiation dose in Group B was decreased 32.62% compared with group A. Conclusion Prospetively ECG - gated scan of narrow window technology in 640 - slice CT for patients with high rate can significantly reduce radiation dose and the image quality can fulfill the routine diagnosis, which is highly recommended.