Post-processing of computed tomography perfusion in patients with acute cerebral ischemia. Variability of inter-reader, inter-region of interest, inter-input model, and inter-software

To determine the reproducibility of quantitative computed tomography perfusion (CTP) parameters generated using different post-processing methods and identify the relative impact of subjective factors on the robustness of CTP parameters in acute ischemic stroke (AIS). A total of 80 CTP datasets from patients with AIS or transient ischemic attack (TIA) were retrospectively post-processed by two observers using different regions of interest (ROI) types, input models, and software. The CTP parameters were derived for 10 parenchymal ROIs. The intra-class correlation coefficients (ICCs) were used to assess the reproducibility of the CTP parameters for various post-processing methods. The Spearman correlation test was used to detect potential relationships between software and input models. The ICCs with 95% confidence intervals (CIs) were 0.94 (0.93–0.96), 0.94 (0.92–0.96), 0.82 (0.79–0.86), and 0.87 (0.85–0.90) for inter-reader agreement by using elliptic ROI, irregular ROI, single-input model, and dual-input model, respectively. The ICCs with 95% CI were 0.98 (0.98–0.98), 0.46 (0.43–0.50), and 0.25 (0.20–0.30) for inter-ROI type, inter-input model, and inter-software agreement, respectively. Although the CTP parameters were stable when measured using different readers with different ROI types, they varied for different input models and software. The standardization of CTP post-processing is essential to reduce variability of CTP values.