Assessment of Perfusion Volumes by a New Automated Software for Computed Tomography Perfusion

Abstract

Introduction: To compare the perfusion volumes assessed by a new automated CT perfusion (CTP) software iStroke with the circular singular value decomposition software RAPID and determine its predictive value for functional outcome in patients with acute ischaemic stroke (AIS) who underwent endovascular treatment (EVT).

Methods: Data on patients with AIS were collected from four hospitals in China. All patients received CTP followed by EVT with complete recanalisation within 24 hours of symptom onset. We evaluated the agreement of CTP measures between the two softwares by Spearman's rank correlation tests and kappa tests. Bland-Altman plots were used to evaluate the agreement of infarct core volume (ICV) on CTP and ground truth on diffusion-weighted imaging (DWI). Logistic regression models were used to test the association between ICV on these two softwares and functional outcomes.

Results: Among 326 patients, 228 had DWI examinations and 40 of them had infarct volume >70 mL. In all patients, the infarct core and hypoperfusion volumes on iStroke had a strong correlation with those on RAPID (ρ=0.68 and 0.66, respectively). The agreement of large infarct core (volume >70 mL) was substantial (kappa=0.73, p<0.001) between these two softwares. The ICV measured by iStroke and RAPID was significantly correlated with independent functional outcome at 90 days (p=0.009 and p<0.001, respectively). In patients with DWI examinations and those with an ICV >70 mL, the ICV of iStroke and RAPID was comparable on individual agreement with ground truth.

Conclusion: The automatic CTP software iStroke is a reliable tool for assessing infarct core and mismatch volumes, making it clinically useful for selecting patients with AIS for acute reperfusion therapy in the extended time window.

Keywords: CT perfusion; Perfusion; Stroke; automated software; computed tomography perfusion; infarct core.

Figure 1. Agreement of infarct core volume between iStroke, RAPID and ground truth in patients with diffusion-weighted imaging. Volume difference between iStroke and ground truth in each patient was present as red dots (the mean volume difference is 14.0 mL, 95% CI −40.6 to 68.7 mL). Volume difference between RAPID and ground truth was present as blue dots (the mean volume difference is 21.8 mL, 95% CI −24.8 to 68.4 mL).

Figure 2. Agreement of infarct core volume between iStroke, RAPID and ground truth in patients with diffusion-weighted imaging infarct volume >70 mL. Volume difference between iStroke and ground truth in each patient was present as red dots (the mean volume difference is 51.8 mL, 95% CI −9.2 to 112.8 mL). Volume difference between RAPID and ground truth was present as blue dots (the mean volume difference is 53.6 mL, 95% CI −7.1 to 114.2 mL).