目的 评估不同标记延迟时间(post labeling delay,PLD)状态下脑血流灌注的差异及临床价值.材料与方法 搜集单侧大脑中动脉(middle cerebral artery,MCA)严重狭窄或闭塞患者30例,行常规MRI、三维时间飞跃法磁共振血管成像(three-dimensional time of flight magnetic resonance angiography,3D-TOF-MRA)、扩散加权成像(diffusion weighted imaging,DWI)以及三维准连续动脉自旋标记技术(three-dimensional pulsed continuous arterial spin labeling,3D pCASL)(PLD=1.5 s,2.5 s)序列扫描.根据表观扩散系数(apparent diffusion coefficient,ADC)信号改变分为DWI(+)组和DWI(-)组.2名观察者测量DWI(+)组梗死灶及DWI(-)组责任侧MCA供血区脑血流量(cerebral blood flow,CBF)值、ADC值,低灌注及DWI高信号面积相对值,16例患者具有NIHSS评分.使用ICC检验结果 一致性,χ2检验分析低灌注检出率差异;独立样本t检验、配对样本t检验分析组间CBF值、组内CBF值及面积相对值差异;Pearson及Spearman相关法分析CBF值与ADC值、NIHSS评分的相关性.结果2名观察者的测量结果一致性良好(ICC=0.98,P<0.05).所有患者、DWI(+)组、DWI(-)组CBF1.5值均低于CBF2.5值(t=-7.207,P=0.000;t=-7.071,P=0.000;t=-3.641,P=0.004).DWI(+)组CBF1.5值、CBF2.5值、ADC值均低于DWI(-)组(t=-8.243,P=0.000;t=-5.536,P=0.000;t=-10.764,P=0.000).PLD=1.5 s低灌注检出率高于PLD=2.5 s(χ2=7.239,P=0.007),低灌注面积相对值大于PLD=2.5 s(0.59±0.11,0.21±0.09,t=4.200,P=0.006).DWI(+)组高信号面积相对值为0.12±0.05,小于PLD=1.5 s低灌注面积相对值,但与PLD=2.5 s时无显著差异(t=4.622,P=0.001;t=2.282,P=0.71).DWI(+)组CBF2.5值和ADC值呈中度正相关,CBF1.5值和NIHSS评分呈中度负相关(r=0.50,P=0.035;r=-0.55,P=0.028).结论 PLD=1.5 s对低灌注敏感,显示缺血面积较大,与临床状态具有较好的一致性;PLD=2.5 s、PLD=1.5 s联合应用能更好地评估侧支循环.%Objective: To assess the differences of different postlabeling delay (PLD) state of cerebral blood perfusion and clinical value. Materials and Methods: Patients with unilateral middle cerebral artery stenosis or occlusion were collected (n=30), who underwent MRI, three-dimensional time of flight magnetic resonance angiography (3D-TOF-MRA), diffusion weighted imaging (DWI) and three-dimensional pulsed continuous arterial spin labeling (3D pCASL) (PLD=1.5 s, PLD=2.5 s) scanning. All patients were divided into DWI (+) and DWI (-) according to ADC value. Cerebral blood flow (CBF) values (CBF1.5, CBF2.5) and ADC values of lesions in DWI (+) and MCA territory in responsible side in DWI (-) were measured by two observers, the relative areas of low perfusion and high DWI signal region were further calculated and NIHSS scores were recorded (n=16). ICC was used to assess the consistency between the two measurers; the difference of low perfusion detection rate was analyzed by Chi-square test, the differences of CBF values between two groups were analyzed by independent sample t test, the differences of CBF values in a group and then the relative areas were analyzed by paired sample t test. Pearson and Spearman correlation analysis were used to analyze the correlation between CBF values vs. ADC values and NIHSS scores. Results: The good consistency was acquired between the two measurers (ICC=0.98, P<0.05). CBF1.5 values were lower than those of CBF2.5 in all patients or DWI (+) or DWI (-) (t=-7.207, P=0.000. t=-7.071, P=0.000. t=-3.641, P=0.004). Compared with DWI (-), CBF1.5 values and CBF2.5 values and ADC values of DWI (+) were decreased (t=-8.243, P=0.000. t=-5.536, P=0.000, t=-10.764, P=0.000). The detection rate of low perfusion was higher and the relative area value of low perfusion was larger with PLD=1.5 s than 2.5 s (χ2=7.239, P=0.007. 0.59±0.11, 0.21±0.09, t=4.20, P=0.006). The relative areas of high signal was 0.12±0.05 in DWI (+), which was lower than those of low perfusion with PLD= 1.5 s, but not differed to those with PLD=2.5 s (t=4.622, P=0.001. t=2.282, P=0.71). There was moderate positive correlation between CBF2.5 values and ADC values in DWI (+) group, moreover there was a moderate negative correlation between CBF1.5 values and NIHSS scores (r=0.50, P=0.035. r=-0.547, P=0.028). Conclusions: PLD of 1.5 s is sensitive to hypoperfusion and shows large ischemic area, which is in good consistency with clinical status. The combined application of PLD of 2.5 s and 1.5 s is better to assess collateral circulation.
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