Reliability of CT Perfusion in the Evaluation of the Ischaemic Penumbra

Abstract

CT perfusion (CTP) is part of the initial evaluation of stroke patients, allowing differentiation between infarcted tissue and the ischaemic penumbra and helping in the selection of patients for endovascular treatment. This study assessed the reliability of the qualitative evaluation CTP maps in defining the ischemic penumbra and identified potential pitfalls associated with this technique. We reviewed CTP scans of 45 consecutive patients admitted to our institution with anterior circulation acute ischaemic stroke. Two neuroradiologists performed qualitative evaluations of cerebral blood volume (CBV) and mean transit time (MTT) maps, using 24h follow-up non-contrast CT as surrogate marker for the area of definitive infarct. For each slice analyzed, the area of qualitative alteration in the CBV and MTT maps was classified as either being inferior, equal or superior to the area of infarct on the follow-up CT. Three out of 45 (7%) patients had admission CT CBV abnormalities larger than follow-up lesions; 34/45 (76%) patients had infarct areas smaller than initial MTT prolongation. In the group of patients with no recanalization 12/19 (63%) had infarct areas smaller than initial MTT lesion. CBV abnormality is a reliable marker for an irreversible ischaemic lesion, although rarely it may overestimate the ischaemic "core", possibly due to delay in contrast arrival to the brain. In the majority of patients without recanalization, MTT overestimated final infarct areas, probably because it does not differentiate true "at risk" penumbra from benign oligaemia. Qualitative evaluation of CBV and MTT maps may overestimate the real ischaemic penumbra.

“CT Angiography Source-Images and CT Perfusion: Are They Complementary Tools for Ischemic Stroke Evaluation?”

“…We appreciate Morelli et al's comment on our recent article 1 and we do agree that the interpretation of computed tomography angiography source images (CTA-SI) may be a valuable tool in the assessment of acute ischaemic stroke.…”

Infarct Core Reliability by CT Perfusion is a Time‐Dependent Phenomenon

“…The final infarct core volume was measured on the follow‐up 24‐hour CT scan using Carestream Vue PACS software manual volume measurements. We defined GIC as a final infarct smaller by at least 10 mL as compared to the initial ischemic core calculated by CTP . All clinical and radiological variables were analyzed to find possible relations to GIC.…”

Accuracy of “At Risk” Tissue Predictions Using CT Perfusion in Acute Large Vessel Occlusions

“…Raw CTP data performed at presentation were postprocessed for this analysis with a standard CTP software package. This experimental design was used to ensure consistency in the results as prior studies have shown that CTP results can vary by software algorithm used . Olea Sphere (Vital Images, Le Ciotat, France) was used to perform all the CTP analysis.…”