Automated CT Perfusion Detection of the Acute Infarct Core in Ischemic Stroke: A Systematic Review and Meta-Analysis

Abstract

<b><i>Introduction:</i></b> In patients with acute ischemic stroke, the location and volume of an irreversible infarct core determine prognosis and treatment. We aimed to determine if automated CT perfusion (CTP) is non-inferior to diffusion-weighted imaging (DWI) or fluid-attenuated inversion recovery (FLAIR) in predicting the acute infarct core. <b><i>Methods:</i></b> In this systematic review and meta-analysis, we searched MEDLINE and EMBASE from 1960 to December 2020. Five outcome measures were examined: volumetric difference, volumetric correlation, sensitivity and specificity at the patient level, Dice coefficient, and sensitivity and specificity at the voxel level. A random-effects meta-analysis was performed for volumetric difference and correlation. <b><i>Results:</i></b> From 3,986 studies retrieved, 48 studies met our inclusion criteria with 46 studies on anterior circulation, one study on posterior circulation, and one study on lacunar infarct strokes. In anterior circulation stroke, there were no significant mean volumetric differences between CTP and acute DWI (cerebral blood flow [CBF] 0.52 mL, 95% CI [−0.07, 1.11], <i>I</i><sup>2</sup> 0.0%; relative CBF [rCBF] 3.01 mL, 95% CI [−0.46, 6.48], <i>I</i><sup>2</sup> 82.6%; relative cerebral blood volume [rCBV] −12.84 mL, 95% CI [−38.56, 12.88], <i>I</i><sup>2</sup> 96.2%) and between CTP and delayed DWI or FLAIR (rCBF −1.29 mL, 95% CI [−6.49, 3.92], <i>I</i><sup>2</sup> 91.8%; rCBV −5.80 mL, 95% CI [−16.20, 4.60], <i>I</i><sup>2</sup> 84.2%). Mean correlation between CTP and acute DWI was 0.90 (95% CI [0.80, 0.95], <i>I</i><sup>2</sup> 60.0%) for rCBF and 0.84 (95% CI [0.58, 0.94], <i>I</i><sup>2</sup> 93.5%) for rCBV. Mean correlation between CTP and delayed DWI or FLAIR was 0.74 (95% CI [0.57, 0.85], <i>I</i><sup>2</sup> 94.6%) for rCBF and 0.90 (95% CI [0.69, 0.97], <i>I</i><sup>2</sup> 93.1%) for rCBV. Sensitivity and specificity at the patient level were reported by three studies and Dice coefficient by four studies. Statistical analysis could not be performed for sensitivity and specificity at the voxel level. Limited evidence was available for posterior circulation or lacunar infarct strokes. <b><i>Conclusion:</i></b> Due to significant heterogeneity and insufficient high-quality studies reporting each outcome, there is insufficient evidence to reliably determine the accuracy of CTP prediction of the infarct core compared to DWI or FLAIR.

CT Perfusion as a Predictor of the Final Infarct Volume in Patients with Tandem Occlusion

“…However, in spite of the availability of different techniques and progresses in mathematical models, ischemic core detection and its spatiotemporal dynamic evolution still presents several challenges in the neuroimaging field [ 38 , 39 , 40 , 41 , 42 , 43 , 44 ]. CTP is a widely accepted tool to predict FIV [ 9 , 10 , 11 , 12 , 13 , 14 ] in LVO by estimating CBV, CBF, or different Tmax depending on the mathematical model used by the software. Such parameters grossly rely upon the time–density curves generated by the scanning contrast bolus passage in different arterial vessels [ 45 , 46 , 47 ].…”

“…In acute ischemic stroke (AIS) due to large vessel occlusion (LVO) of the anterior brain circulation, endovascular treatment (EVT) is considered effective both alone or in combination with intravenous rTPA administration in the first 6 h [ 1 , 2 , 3 , 4 , 5 , 6 ]. After 6 h, the combined use of CT perfusion (CTP) and multiphasic CT angiography (mCTA) enables the selection of patients with LVO who may still benefit from EVT by discriminating among definitive ischemic core volume and still salvageable brain tissue (penumbra) [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ], finally predicting functional outcome [ 15 ].…”

Assessing the diagnostic accuracy of CT perfusion: a systematic review

“…Consequently, the results varied even when published by the same group. The use of time-dependent thresholds for ischemic core, such as rCBF and Tmax, which are impacted by time to reperfusion, and highly effective reperfusion therapies such as thrombectomy may also impact variability ( 18 , 47 , 48 ) ( 8 , 10 ). Additionally, 15 studies defined a single threshold for all brain regions irrespective of collaterals and the gray and white matter.…”

“…Previous systematic reviews investigating parameters and thresholds have included studies using magnetic resonance perfusion-weighted imaging (MR-PWI) ( 8 , 9 ) or positron emission tomography (PET) ( 9 ) as well as CT perfusion (CTP). A recent meta-analysis ( 10 ) examining volumetric and spatial accuracy of CTP for identifying core did not account for the multiple thresholds reported for each parameter ( 11 ) and included several studies that failed to perform co-registration of CTP to the reference standard. Co-registration is essential to ensure the accuracy of volumetric analysis as images are aligned in the same coordinate space ( 12 ).…”

Comparison of two automated CT perfusion software packages in patients with ischemic stroke presenting within 24 hours of onset

“…5 To streamline the analysis of perfusion and minimize variations among different observers, various commercial CTP software solutions have been introduced. 6 These solutions automatically identify the ischemic core and penumbral regions. Nonetheless, there has been considerable inconsistency in the parameters of CTP and the quantitative benchmarks set for delineating the ischemic core and penumbra.…”