编码速率对大脑中动脉PC-MRI测量值的影响

Influence of Venc on PC-MRI Flow Velocity Measurements of Middle Cerebral Artery

目的 应用3.0 T相位对比磁共振成像（PC-MRI）测量正常成人大脑中动脉（MCA）的流速,探讨不同编码速率（Venc）对测量结果的影响。方法 对32名健康志愿者行MCA PC-MRI测量,选用TOF-MRA原始图像垂直MCA水平段定位,在PCA幅度像上沿边缘绘制ROI。每位志愿者预置Venc 50、100、150、200、250 cm/s对右侧MCA行5次扫描,同时预置Venc 100 cm/s对左侧MCA进行扫描。取峰值流速（PV）、平均流速（MV）及平均流量（MF）进行参数分析。采用SPSS 17.0进行数据统计分析,P〈0.05为差异有统计学意义。结果 Venc预置50cm/s均出现相位混淆现象。Venc预置100~200 cm/s各指标均数间差异无统计学意义（FPV=0.43,FMV=0.075,FMF=0.18,P值均〉0.05）;Venc预置50~200 cm/s、Venc 100~250 cm/s各指标均数间差异有统计学意义（FPV=37.2,FMV=57.9,FMV=34.7;FPV=11.8,FMV=7.3,FMF=9.0;P值均〈0.01）。取Venc100 cm/s比较左右MCA各指标均数差异有统计学意义（tPV=5.89,tMV=6.59,tMF=4.90;P值均〈0.05）。结论 （1）大脑中动脉PC-MRI测量可行的Venc区间为100~200 cm/s。（2）左侧MCA流速、流量高于右侧。

Objective To evaluate the normal flow velocity measurements of middle cerebral artery （MCA） by using 3T MR cine phase-contrast technique, and to explore the influences of different Venc on the PC-MR flow measurements of MCA. Methods A total of 32 healthy volunteers were enrolled in this study. A localizer was placed on TOF-MRA image and the region of interest （ROI） was drawn in the PCA amplitude image when the MCA could be seen optimally. For every volunteer, the localizer was placed perpendicular to ampulla region of the MCA, with the Venc being 50, 100, 150, 200 and 250 em/s separately. The evaluated parameters included the peak velocity （PV） , mean velocity （MV） and the mean flow （MF）. Using SPSS 17.0 software, statistical analysis was made, and P 〈0.05 was considered to be statistically significant. Results When Vent was set at 50cm/s, all phase images appeared phase confusion; when Venc was set at 100 200 cm/s, all parameters did not show any statistical difference （FPV =0.43, FMV = 0. 075, FMF = 0. 18, P 〉 0.05 ）. When Vene was set at 50 -200 cm/s or 100 -250 cm/s all parameters showed prominent statistical difference （FPV = 37.2, FMV = 57.9, FMF = 34.7 ; FPV = 11.8, FMV = 7.3, FMF = 9.0 ; P 〈 0.01 ）. Setting Venc at 100cm/s to compare parameters difference between right MCA and left MCA, the results indicated that all parameters did not show any statistical difference （tPV = 5.89,tMV = 6. 59,tMF = 4. 90 ; P 〈 0.05 ）. Conclusion （ 1 ） The feasible Venc range for PC-MR measurement of MCA was 100 -200 cm/s. （2） Both the velocity and/low of right MCA are higher than those of left MCA.