Comparison of Accuracy of Arrival-Time-Insensitive and Arrival-Time-Sensitive CTP Algorithms for Prediction of Infarct Tissue Volumes

Abstract

the purpose of this study was to compare the performance of arrival-time-insensitive (Ati) and arrivaltime-sensitive (AtS) computed tomography perfusion (ctp) algorithms in philips intelliSpace portal (v9, ISP) and to investigate optimal thresholds for ATI regarding the prediction of final infarct volume (FIV). Retrospective, single-center study with 54 patients (mean 67.0 ± 13.1 years, 68.5% male) who received Stroke-CT/CTP-imaging between 2010 and 2018 with occlusion of the middle cerebral artery in the M1-/proximal M2-segment or terminal internal carotid artery. FIV was determined on shortterm follow-up imaging in two patient groups: A) not attempted or failed mechanical thrombectomy (Mt) and B) successful Mt. AtS (default settings) and Ati (full-range of threshold settings regarding FIV prediction) maps were coregistered in 3D with FIV using voxel-wise overlap measurement. Based on an average imaging follow-up of 2.6 ± 2.1 days, the estimation regarding penumbra (group A, ATI: r = 0.63/0.69, ATS: r = 0.64) and infarct core (group B, ATI: r = 0.60/0.68, ATS: r = 0.63) was slightly higher in ATI but the effect was not significant (p > 0.05). Regarding ATI, Tmax (AUC 0.9) was the best estimator of the penumbra (group A), CBF relative to the contralateral hemisphere (AUC 0.80) showed the best estimation of the infarct core (group B). there was a broad range of thresholds of optimal Ati settings in both groups. prediction of fiV with Ati was slightly better compared to AtS. However, this difference was not significant. Since ATI showed a broad range of optimal thresholds, exact thresholds regarding the Ati algorithm should be evaluated in further prospective, clinical studies. Computed tomography perfusion (CTP) represents a valuable adjunct to unenhanced CT and CT-angiography (CTA) in the diagnosis of acute ischemic stroke (AIS), playing a vital role in clinical decision making 1-3. By generating a four-dimensional dataset of the brain, tissue perfusion parameters derived from CTP allow to differentiate between ischemic core and penumbra using selected combinations and thresholds 4. If CTP shows a prevalent mismatch between ischemic core and penumbra, patients can benefit from mechanical thrombectomy (MT) up to 24 hours after AIS onset 1. Moreover, an ischemic core volume of 70 ml is regarded as the critical threshold above which patients show a significantly worse clinical outcome; therefore, accurate core and penumbra measurements derived from CTP are essential 5,6. For many years, the arrival-time-sensitive (ATS) post-processing algorithm represented the standard for CTP, which was thoroughly tested during the last two decades 4,7-9. A potential limitation of ATS is its sensitivity to contrast agent arrival delay and dispersion 7,10 , which can be problematic in patients with reduced cardiac output,

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