A CT system-free Approach for Brain CT Perfusion Assessment: Temporal Perfusion Index Estimation

Real-time brain perfusion would be highly beneficial to fully leverage interventional procedures such as endovascular thrombectomy in treating ischemic stroke. However, the existing standard of care is constrained due to the absence of intra-operative real-time perfusion imaging. We propose an intra-interventional perfusion with no C-arm rotation (IPEN)based method to perform quantitative perfusion analysis using x-ray angiography (XA) images in the interventional suite. IPEN is built using tomographic principles, where the value of N homogeneous regions-of-interests (ROI) of known shape can be estimated using N x-ray beams from a single projection. The objective of IPEN for brain perfusion is to provide dynamic time-enhancement curve (TEC) and temporal perfusion indices (PI's) for ROIs within the brain. The proposed algorithm was assessed using XCAT phantoms developed for dynamic CT perfusion. Eight ischemic stroke cases were simulated and for each of them intra-arterially enhanced XA images were acquired. Using these XA images IPEN was employed to estimate TEC and PI such as time-to-maximum (Tmax) and mean-transit-time (MTT) for ROIs defined. The accuracy of the estimated values was quantitatively evaluated using the normalized root-mean-square error weighted by ROI's fraction-by-volume (NRMSE) and the linear correlation coefficient (R). The estimated TEC, and PI's showed good agreement with ground truth values. The NRMSE values were 15.5% ± 1.2% for TEC, 14.5% ± 5.7% for Tmax, and 12.2% ± 5.1% for MTT. The R values (P < 0.01) across eight cases ranged 0.82-0.95 for TEC, 0.70-0.99 for Tmax, and 0.67-0.96 for MTT.