Abstract TP039: Comparative Utility of CT and MRI in Initial Imaging for Mechanical Thrombectomy in Patients with Large Vessel Occlusion

Background: Computed tomography (CT) is the internationally accepted standard for initial imaging in mechanical thrombectomy for large vessel occlusion (LVO), whereas magnetic resonance imaging (MRI) is widely used in Japan. This study compared treatment outcomes according to initial imaging modality using data from the Kanagawa Intravenous and Endovascular Treatment (K-NET) registry. Methods: The K-NET registry is a prospective multicenter study of thrombolytic therapy for LVO across 40 Japanese institutions. We analyzed 3,182 patients enrolled between 2018 and 2021: 1,265 underwent MRI alone (MRI group), 830 underwent CT alone (CT group), and 1,087 underwent both (Combined group). The primary endpoint was favorable outcome, defined as modified Rankin Scale (mRS) score 0–2 at 90 days. Secondary endpoints included door-to-puncture time (DTP), puncture-to-recanalization time (PTR), intracranial hemorrhage (ICH), symptomatic ICH, and mortality. Outcomes were assessed by univariate analyses stratified by occlusion site, followed by propensity score analysis. Results: Median age was 77, 79, and 79 years in the MRI, CT, and Combined groups, respectively; corresponding NIHSS scores were 17, 19, and 18. MRI patients were younger and had lower baseline severity. Occlusion sites were ICA 26%, MCA 65%, and BA/VA 5% in the MRI group; ICA 31%, MCA 59%, and BA/VA 8% in the CT group; and ICA 25%, MCA 62%, and BA/VA 10% in the Combined group. Median DTP was 52, 62, and 97 minutes, and PTR was 37, 53, and 56 minutes, showing significant differences. ICH was more frequent in the MRI group (21%), while symptomatic ICH did not differ. The proportion of patients achieving an mRS score of 0-2 at 90 days was significantly higher in the MRI group (43%) compared to the CT (39%) and Combined (39%) groups. Subgroup analyses showed significantly better outcomes with MRI in MCA (M2/M3) and BA occlusions, but not ICA or M1. After propensity score matching, no significant outcome differences were observed among groups. Conclusions: Compared with CT and Combined groups, MRI patients were younger, with lower NIHSS scores. Although MRI was associated with longer onset-to-door time, it was associated with shorter DTP and PTR. The MRI group showed superior crude outcomes, but these differences were not significant after adjustment for baseline characteristics.