Nasel Christian, Klickovic Uros, Kührer Heike-Marie, Villringer Kersten, Fiebach Jochen B, Villringer Arno, Moser Ewald
Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.
Department of Radiology, University Hospital Tulln, Tulln, Austria.
Front Physiol. 2019 Jan 15;9:1945. doi: 10.3389/fphys.2018.01945. eCollection 2018.
Perfusion magnetic resonance imaging (P-MRI) is part of the mismatch concept employed for therapy decisions in acute ischemic stroke. Using dynamic susceptibility contrast (DSC) MRI the time-to-maximum (Tmax) parameter is quite popular, but its inconsistently defined computation, arterial input function (AIF) selection, and the applied deconvolution method may introduce bias into the assessment. Alternatively, parameter free methods, namely, standardized time-to-peak (stdTTP), z-score, and standardized-z (stdZ) are also available, offering consistent calculation procedures without the need of an AIF or deconvolution. Tmax was compared to stdTTP, z-, and stdZ to evaluate robustness of infarct volume estimation in 66 patients, using data from two different sites and MR systems (i.e., 1.5T vs. 3T; short TR (= 689 ms) vs. medium TR (= 1,390 ms); bolus dose 0.1 or 0.2 ml/kgBW, respectively). Quality factors (QF) for Tmax were 0.54 ± 0.18 (sensitivity), 0.90 ± 0.06 (specificity), and 0.87 ± 0.05 (accuracy). Though not significantly different, best specificity (0.93 ± 0.05) and accuracy (0.90 ± 0.04) were found for stdTTP with a sensitivity of 0.56 ± 0.17. Other tested parameters performed not significantly worse than Tmax and stdTTP, but absolute values of QFs were slightly lower, except for z showing the highest sensitivity (0.72 ± 0.16). Accordingly, in ROC-analysis testing the parameter performance to predict the final infarct volume, stdTTP and z showed the best performance. The odds for stdTTP to obtain the best prediction of the final infarct size, was 6.42 times higher compared to all other parameters (odds-ratio test; = 2.210-16). Based on our results, we suggest to reanalyze data from large cohort studies using the parameters presented here, particularly stdTTP and zf-score, to further increase consistency of perfusion assessment in acute ischemic stroke.
灌注磁共振成像（P-MRI）是用于急性缺血性中风治疗决策的不匹配概念的一部分。使用动态磁敏感对比（DSC）MRI时，最大时间（Tmax）参数很受欢迎，但其计算定义不一致、动脉输入函数（AIF）选择以及应用的去卷积方法可能会在评估中引入偏差。另外，也有无需参数的方法，即标准化峰值时间（stdTTP）、z分数和标准化z（stdZ），它们提供一致的计算程序，无需AIF或去卷积。使用来自两个不同地点和MR系统（即1.5T与3T；短TR（=689毫秒）与中TR（=1390毫秒）；团注剂量分别为0.1或0.2毫升/千克体重）的数据，将Tmax与stdTTP、z和stdZ进行比较，以评估66例患者梗死体积估计的稳健性。Tmax的质量因子（QF）为0.54±0.18（敏感性）、0.90±0.06（特异性）和0.87±0.05（准确性）。虽然没有显著差异，但stdTTP的最佳特异性（0.93±0.05）和准确性（0.90±0.04）的敏感性为0.56±0.17。其他测试参数的表现不比Tmax和stdTTP差，但QF的绝对值略低，除了z显示出最高的敏感性（0.72±0.16）。因此，在ROC分析中测试参数预测最终梗死体积的性能时，stdTTP和z表现最佳。与所有其他参数相比，stdTTP获得最终梗死大小最佳预测的几率高6.42倍（优势比检验；=2.2×10-16）。基于我们的结果，我们建议使用此处介绍的参数，特别是stdTTP和zf分数，重新分析大型队列研究的数据，以进一步提高急性缺血性中风灌注评估的一致性。
