Department of Medicine, The Melbourne Brain Centre at Royal Melbourne Hospital, University of Melbourne, Parkville, Victoria, Australia.
Stroke. 2012 Oct;43(10):2648-53. doi: 10.1161/STROKEAHA.112.660548. Epub 2012 Aug 2.
Perfusion imaging has the potential to select patients most likely to respond to thrombolysis. We tested the correspondence of computed tomography perfusion (CTP)-derived mismatch with contemporaneous perfusion-diffusion magnetic resonance imaging (MRI).
Acute ischemic stroke patients 3 to 6 hours after onset had CTP and perfusion-diffusion MRI within 1 hour, before thrombolysis. Relative cerebral blood flow (relCBF) and time to peak of the deconvolved tissue residue function (Tmax) were calculated. The diffusion lesion (diffusion-weighted imaging) was registered to the CTP slabs and manually outlined to its maximal visual extent. Volumetric accuracy of CT-relCBF infarct core (compared with diffusion-weighted imaging) was tested. To reduce false-positive low CBF regions, relCBF core was restricted to voxels within a relative time-to-peak (relTTP) >4 seconds for lesion region of interest. The MR-Tmax >6 seconds perfusion lesion was automatically segmented and registered to CTP. Receiver-operating characteristic analysis determined the optimal CT-Tmax threshold to match MR-Tmax >6 seconds. Agreement of these CT parameters with MR perfusion-diffusion mismatch in coregistered slabs was assessed (mismatch ratio >1.2, absolute mismatch >10 mL, infarct core <70 mL).
In analysis of 49 patients (mean onset to CT, 213 minutes; mean CT to MR, 31 minutes), constraining relCBF <31% within the automated relTTP perfusion lesion region of interest reduced the median magnitude of volumetric error (vs diffusion-weighted imaging) from 47.5 mL to 15.8 mL (P<0.001). The optimal CT-Tmax threshold to match MR-Tmax >6 seconds was 6.2 seconds (95% confidence interval, 5.6-7.3 seconds; sensitivity, 91%; specificity, 70%; area under the curve, 0.87). Using CT-Tmax >6 seconds "penumbra" and relTTP-constrained relCBF "core," CT-based and MRI-based mismatch status was concordant in 90% (kappa=0.80).
Quantitative CTP mismatch classification using relCBF and Tmax is similar to perfusion-diffusion MRI. The greater accessibility of CTP may facilitate generalizability of mismatch-based selection in clinical practice and trials.
灌注成像是选择最有可能对溶栓治疗有反应的患者的一种有潜力的方法。我们测试了计算 CT 灌注（CTP）衍生的不匹配与同期灌注-弥散磁共振成像（MRI）之间的一致性。
急性缺血性脑卒中患者在发病后 3 至 6 小时内，在溶栓治疗前 1 小时内进行 CTP 和灌注-弥散 MRI。计算相对脑血流量（relCBF）和去卷积组织残留函数（Tmax）的峰值时间。将弥散病变（弥散加权成像）与 CTP 切片配准，并手动勾画到最大可视范围。CT- relCBF 梗死核心的容积准确性（与弥散加权成像相比）进行了测试。为了减少假阳性的低 CBF 区域，将 relCBF 核心限制在感兴趣区域的相对达峰时间（relTTP）>4 秒的体素内。MR-Tmax>6 秒的灌注病变通过自动分割并与 CTP 配准。受试者工作特征分析确定了匹配 MR-Tmax>6 秒的最佳 CT-Tmax 阈值。评估了这些 CT 参数与核心配准切片中的 MR 灌注-弥散不匹配的一致性（不匹配比>1.2，绝对不匹配>10 毫升，梗死核心<70 毫升）。
在对 49 例患者（发病至 CT 的平均时间为 213 分钟；CT 至 MR 的平均时间为 31 分钟）的分析中，在自动 relTTP 灌注病变感兴趣区域内将 relCBF<31%限制，可以将容积误差的中位数幅度从 47.5 毫升降低到 15.8 毫升（P<0.001）。匹配 MR-Tmax>6 秒的最佳 CT-Tmax 阈值为 6.2 秒（95%置信区间，5.6-7.3 秒；灵敏度为 91%，特异性为 70%，曲线下面积为 0.87）。使用 CT-Tmax>6 秒的“半影”和 relTTP 限制的 relCBF“核心”，CT 基于和 MRI 基于的不匹配状态在 90%（kappa=0.80）的情况下是一致的。
使用 relCBF 和 Tmax 的定量 CTP 不匹配分类与灌注-弥散 MRI 相似。CTP 的更大可及性可能会促进基于不匹配的选择在临床实践和试验中的推广。
