Butcher Ken, Parsons Mark, Allport Louise, Lee Sang Bong, Barber P Alan, Tress Brian, Donnan Geoffrey A, Davis Stephen M
Department of Neurology, Royal Melbourne Hospital, University of Melbourne, Melbourne, Australia.
Stroke. 2008 Jan;39(1):75-81. doi: 10.1161/STROKEAHA.107.490524. Epub 2007 Dec 6.
For MR perfusion-diffusion (PWI-DWI) mismatch to become routine in thrombolysis patient selection, rapid and reliable assessment tools are required. We examined interrater variability in PWI/DWI volume measurements and developed a rapid assessment tool based on the Alberta Stroke Program Early CT Scores (ASPECTS) system.
DWI and PWI were performed in 35 patients with stroke <6 hours after symptom onset. DWI lesion and PWI (time to peak) volumes were measured with planimetric techniques by 4 raters and the 95% limits of agreement calculated. ASPECT scores were assessed separately by 4 investigators (2 experienced and 2 inexperienced) for DWI (MR DWI scores) and PWI (MR time to peak scores). MR mismatch scores were calculated as MR DWI-MR time to peak scores.
Interobserver variability was much greater for PWI (95% limit of agreement=+/-72.3 mL) than for DWI (95% limit of agreement=+/-12.6 mL). A semiautomated PWI volume (time to peak+2 s) was therefore used to calculate mismatch volume. MR mismatch scores >or=2 predicted 20% PWI-DWI mismatch by volume with mean 78% sensitivity (range, 72% to 84%) and 88% specificity (range, 83% to 90%). There was excellent agreement on mismatch classification using MR mismatch scores between experienced raters (weighted kappa scores of 0.94) with agreement in 34 of 35 cases. Agreement was less consistent between inexperienced raters (weighted kappa=0.49, 28 of 35 cases).
Variability in planimetric mismatch measurements arises primarily from differences in PWI volume assessment. High specificity and interrater reliability may make MR mismatch scores an ideal rapid screening tool for potential thrombolysis patients.
为使磁共振灌注 - 扩散成像（PWI - DWI）不匹配在溶栓患者选择中成为常规方法，需要快速且可靠的评估工具。我们研究了PWI/DWI体积测量的观察者间变异性，并基于阿尔伯塔卒中项目早期CT评分（ASPECTS）系统开发了一种快速评估工具。
对35例症状发作后<6小时的卒中患者进行DWI和PWI检查。由4名评估者采用面积测量技术测量DWI病变和PWI（达峰时间）体积，并计算95%一致性界限。4名研究者（2名经验丰富者和2名经验不足者）分别对DWI（MR DWI评分）和PWI（MR达峰时间评分）进行ASPECT评分。MR不匹配评分计算为MR DWI - MR达峰时间评分。
PWI的观察者间变异性（95%一致性界限 = ±72.3 mL）远大于DWI（95%一致性界限 = ±12.6 mL）。因此，使用半自动PWI体积（达峰时间 + 2秒）来计算不匹配体积。MR不匹配评分≥2预测20%的PWI - DWI体积不匹配，平均敏感性为78%（范围72%至84%），特异性为88%（范围83%至90%）。经验丰富的评估者使用MR不匹配评分对不匹配分类的一致性极佳（加权kappa评分0.94），35例中有34例一致。经验不足的评估者之间的一致性较差（加权kappa = 0.49，35例中有28例一致）。
面积测量不匹配的变异性主要源于PWI体积评估的差异。高特异性和观察者间可靠性可能使MR不匹配评分成为潜在溶栓患者理想的快速筛查工具。
