Qualitative versus automatic evaluation of CT perfusion parameters in acute posterior circulation ischaemic stroke

Raffaella Capasso,Stefano Vallone,Gabriele Zelent,Federico Sacchetti,Guido Bigliardi,Andrea Zini,Luca Verganti,Ferdinando Caranci,Nicola Serra,Livio Picchetto

doi:10.1007/s00234-020-02517-6

Abstract

PurposeTo compare the diagnostic accuracy (ACC) in the detection of acute posterior circulation strokes between qualitative evaluation of software-generated colour maps and automatic assessment of CT perfusion (CTP) parameters.MethodsWere retrospectively collected 50 patients suspected of acute posterior circulation stroke who underwent to CTP (GE “Lightspeed”, 64 slices) within 24 h after symptom onset between January 2016 and December 2018. The Posterior circulation-Acute Stroke Prognosis Early CT Score (pc-ASPECTS) was used for quantifying the extent of ischaemic areas on non-contrast (NC)CT and colour-coded maps generated by CTP4 (GE) and RAPID (iSchemia View) software. Final pc-ASPECTS was calculated on follow-up NCCT and/or MRI (Philips Intera 3.0 T or Philips Achieva Ingenia 1.5 T). RAPID software also elaborated automatic quantitative mismatch maps.ResultsBy qualitative evaluation of colour-coded maps, MTT-CTP4D and Tmax-RAPID showed the highest sensitivity (SE) (88.6% and 90.9%, respectively) and ACC (84% and 88%, respectively) compared with the other perfusion parameters (CBV, CBF). Baseline NCCT and CBF provided by RAPID quantitative perfusion mismatch maps had the lowest SE (29.6% and 6.8%, respectively) and ACC (38% and 18%, respectively). CBF and Tmax assessment provided by quantitative RAPID perfusion mismatch maps showed significant lower SE and ACC than qualitative evaluation. No significant differences were found between the pc-ASPECTSs assessed on colour-coded MTT and Tmax maps neither between the scores assessed on colour-coded CBV-CTP4D and CBF-RAPID maps.ConclusionQualitative analysis of colour-coded maps resulted more sensitive and accurate in the detection of ischaemic changes than automatic quantitative analysis.

Highlights

Posterior circulation (PC) stroke accounts for 20–25% of ischaemic strokes and is characterised by a wide range of clinical features that make its clinical diagnosis challenging [1,2,3,4,5,6,7,8,9,10,11,12]
cerebral blood flow (CBF) and to maximum (Tmax) assessment provided by quantitative RAPID perfusion mismatch maps showed significant lower SE and ACC than qualitative evaluation
No significant differences were found between the pc-ASPECTSs assessed on colour-coded mean transit time (MTT) and Tmax maps neither between the scores assessed on colourcoded cerebral blood volume (CBV)-CT Perfusion 4D (CTP4D) and CBF-RAPID maps

Summary

Introduction

Posterior circulation (PC) stroke accounts for 20–25% of ischaemic strokes and is characterised by a wide range of clinical features that make its clinical diagnosis challenging [1,2,3,4,5,6,7,8,9,10,11,12]. Visual inspection of CTP colour-coded maps can be an effective way to discriminate areas of core infarct and penumbra and may be enough to guide therapeutic choice. Neuroradiology (2021) 63:317–330 and simple to use but its strengths may be affected by variability in post-processing, broad range of imaging and computational approaches, selection of parametric maps, expertise skills and the generally qualitative nature of such approaches [23]. Quantitative CTP analysis has reported to be efficient in demonstrating acute ischaemia, distinguishing salvageable from unsalvageable ischaemic tissue and predicting therapeutic outcome, protocols and guidelines for quantitative thresholds vary [24,25,26,27,28,29,30,31,32,33]. Expert consensus has underlined the need for standardization in the acquisition, processing and analysis of perfusion imaging [23]

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