Perfusion-CT Assessment of Infarct Core and Penumbra

Abstract

Background and Purpose-Different definitions have been proposed to define the ischemic penumbra from perfusion-CT (PCT) data, based on parameters and thresholds tested only in small pilot studies. The purpose of this study was to perform a systematic evaluation of all PCT parameters (cerebral blood flow, volume [CBV], mean transit time [MTT], time-to-peak) in a large series of acute stroke patients, to determine which (combination of) parameters most accurately predicts infarct and penumbra. Methods-One hundred and thirty patients with symptoms suggesting hemispheric stroke Յ12 hours from onset were enrolled in a prospective multicenter trial. They all underwent admission PCT and follow-up diffusion-weighted imaging/fluid-attenuated inversion recovery (DWI/FLAIR); 25 patients also underwent admission DWI/FLAIR. PCT maps were assessed for absolute and relative reduced CBV, reduced cerebral blood flow, increased MTT, and increased time-to-peak. Receiver-operating characteristic curve analysis was performed to determine the most accurate PCT parameter, and the optimal threshold for each parameter, using DWI/FLAIR as the gold standard. Results-The PCT parameter that most accurately describes the tissue at risk of infarction in case of persistent arterial occlusion is the relative MTT (area under the curveϭ0.962), with an optimal threshold of 145%. The PCT parameter that most accurately describes the infarct core on admission is the absolute CBV (area under the curveϭ0.927), with an optimal threshold at 2.0 mlϫ100 g

Global and focal cerebral perfusion after aneurysmal subarachnoid hemorrhage in relation with delayed cerebral ischemia

“…[22] Our quantitative perfusion values were within the range described by other groups. [17,23] Also, our semiquantitative analyses were in the same line as the quantitative findings, which further supports the validity of our quantitative measures.…”

The Vascular Mean Transit Time: A Surrogate for the Penumbra Flow Threshold?

“…Our results suggesting that the MTT is indeed a reasonably reliable surrogate of the penumbra flow threshold provide support to time-based perfusion mapping using MR or CT in the clinical setting-provided appropriate stringent thresholds are used (Donnan et al, 2009). As with MR, the diffusion weighted imaging lesion may represent not only the core but also the penumbral tissue (Guadagno et al, 2006), whereas with CT perfusion, there are inconsistencies regarding a CBV threshold for the core tissue (Murphy et al, 2008;Wintermark et al, 2006), clinically reliable maps of the penumbra and core compartments are still awaited. Defining reliable core markers is therefore an important issue to address in future work.…”

“…Our AUCs were overall lower than the former, but higher than the latter two pMR studies. The fourth study, based on pCT (Wintermark et al, 2006), reported an inordinately high AUC of 0.96 for the MTT ratio. Overall, therefore, the AUCs found in this study are well within the range reported in earlier pMR or pCT studies, in turn further supporting the validity of MTT for predicting the penumbra flow threshold.…”

“…For instance, OTs for absolute MTT of 5.3 seconds (Zaro-Weber et al, 2010a), 7 seconds (Wintermark et al, 2006), and 10 seconds (Olivot et al, 2009) have been reported. One study reported an MTT delay threshold of 7.8 seconds (Grandin et al, 2002) and another (Thijs et al, 2001) of > 4 to 6 seconds, to be associated with diffusion weighted imaging lesion growth.…”

“…One study reported an MTT delay threshold of 7.8 seconds (Grandin et al, 2002) and another (Thijs et al, 2001) of > 4 to 6 seconds, to be associated with diffusion weighted imaging lesion growth. With regard to MTT ratio, optimal cutoffs of 145% (Wintermark et al, 2006) and 163% (Rohl et al, 2001) have been reported. Our OT values for absolute, delay, and ratio MTT (B8 seconds, 4 seconds, and 150% to 200%, respectively) are overall comparable with these earlier pMR-or pCT-derived thresholds.…”