注射流率对脑CT灌注成像血流动力学的影响

Effect of contrast medium injection rate on cerebral hemodynamics study by using multislice CT perfusion imaging

目的比较不同注射流率下脑CT灌注成像的血流动力学参数,确定1个既能保证数据的准确性,操作上又相对安全的对比剂注射流率。方法24名健康志愿者按对比剂注射流率(4.5、6.0、7.5 m l/s)分为3组,肘前静脉团注对比剂4 s后行CT灌注扫描,利用灌注分析软件进行处理,生成大脑前动脉和上矢状窦的时间-密度曲线(TDC),计算脑灰、白质的血流量(rCBF1、rCBF2)。比较3组间脑血流动力学指标,包括输出静脉起始增强与输入动脉增强达到峰值的时间差(tV0-tAP)、rCBF1、rCBF2,并进行统计学分析。结果3组间的tV0-tAP分别为-3.5 s、-1.5 s、0.2 s,组间差异有统计学意义(F=18.25,P<0.01),两两比较差异均有统计学意义(P<0.05),仅7.5 m l/s组的tAP较tV0提前约0.2 s;3组间的rCBF1、rCBF2差异均有统计学意义(P<0.05);7.5 m l/s组rCBF1、rCBF2分别为(52.8±3.1)m l.m in-1.100 g-1、(21.9±2.4)m l.m in-1.100 g-1。结论使用7.5 m l/s的注射流率能够满足最大斜率模型的前提条件,得到的脑血流量与单光子发射型计算机体层成像(SPECT)非常接近。

Objection To explore a practical injection rate at which the assumption of maximal slope model can be guaranteed and at which quantitative assessment of regional cerebral blood flow （rCBF） is accurate. Methods Twenty-four healthy adult volunteers matched with sexes and years were averagely divided into three groups. All volunteers received intravenous administration of 50 ml contrast medium at different injection rates （4. 5,6.0 ml/s and 7.5 ml/s ）. Dynamic scans were made at the level of the basal ganglia slice and its adjacent slices and started 4 s after the administration of contrast medium, then repeated every 1.0 s for 4 images, and performed for 50 s. These 200-slice dynamic images were processed with the dedicated perfusion software. Firstly, time-concentration curves （TDCs） were constructed from every volunteer＇s perfusion CT series in pixels of the anterior cerebral artery, in pixels of the sagittal venous sinus, respectively. Secondly, the rCBFs of the gray matter and the white matter（ rCBF1 ,rCBF2 ）were acquired with a maximal-slope-model-based algorithm. Comparisons of parameters of cerebral hemodynamics [ the difference between the point of the venous starting enhancement and the point of arterial peak enhancement （tvo-tAp）, rCBF1, rCBF2 ] were determined between the different groups and then statistically analyzed. Results The tsp arrived before the tvo only for 7.5 ml/s. （tvo-tAp） was -3.5 s,-1.5 s,0.2 s, respectively for 4. 5 ml/s, 6.0 ml/s and 7.5 ml/s. The difference of （ tvo-tAp） among the three groups was significant （ F = 18.25, P 〈 0. 01 ）. The rCBF1 and rCBF2 had significant differences between 4. 5 ml/s, 6.0 ml/s and 7.5 ml/s; they were （52.8 ±3. 1） ml·min^-1·100g^-1, （21.9 ±2.4）ml ml·min^-1·100g^-1, respectively for 7.5 ml/s. Conclusion The injection rate of 7.5 ml/s, at which the assumption of maximal slope model can be guaranteed and at which CT-rCBF values are considerably close to those obtained by SPECT, is a practical and promising one.