PURPOSE: To investigate the clinical feasibility of a CT collateral map compared with an MRA collateral map, focusing on collateral perfusion (CP) estimation and baseline lesion assessment in acute ischemic stroke (AIS). MATERIALS AND METHODS: This retrospective analysis used selected data from a prospectively collected database. We generated CT collateral maps derived from CT perfusion, encompassing images of arterial, capillary, early venous (CMEV), late venous, and delay phases. Three raters assessed CP scores from MRA and CT collateral maps and CMEV lesion volumes. Lesion volumes of baseline diffusion-weighted imaging (bDWI) and cerebral blood flow rate (CBF) <
30% were automatically measured by the software. The agreement between MRA and CT collateral maps in CP estimation and the correlation between lesion volumes with a CBF <
30% and the CMEV for bDWI lesion volumes were analyzed. RESULTS: One-hundred ten patients (mean age ± standard deviation, 71 ± 14
60 women) with AIS due to steno-occlusion of the internal carotid and/or middle cerebral arteries were included. The agreement between the MRA and CT collateral maps in CP grading was excellent (weighted κ = 0.93
95% CI, 0.90-0.97). The concordance correlation coefficients (CCCs) of the CBF <
30% and CMEV for bDWI lesion volumes were 0.76 (95% CI, 0.60-0.91) and 0.97 (0.95-0.98), respectively. CONCLUSION: The clinical feasibility of the CT collateral map is demonstrated by its significant correlation with the MRA collateral map in CP estimation and baseline lesion assessment.