Structural and metabolic imaging after mechanical thrombectomy for acute ischemic stroke: A hybrid 18F-FDG PET/MRI pilot study

Abstract

Hybrid 2-[18F]-fluoro-2-deoxy-D-glucose positron emission tomography/magnetic resonance imaging (18F-FDG PET/MRI) enables simultaneous, single-session assessment of structural and metabolic stroke damage. We prospectively studied 10 consecutive patients (6 women; mean age 71.6 ± 11.2 years) with anterior-circulation stroke due to middle cerebral artery (MCA) occlusion who underwent successful mechanical thrombectomy (MT). Structural damage was graded with the Alberta Stroke Program Early CT Score (ASPECTS) on admission and 24-h non-contrast CT and on diffusion-weighted imaging (DWI) and fluid-attenuated inversion recovery (FLAIR) at 72 hours; metabolic damage was graded with a PET-adapted ASPECTS on simultaneously acquired 18F-FDG PET at 72 hours. A between-modality difference of ≥3 ASPECTS points was considered significant. Baseline ASPECTS was 10 in 9 patients, and all achieved successful recanalization (modified Thrombolysis in Cerebral Infarction 2c-3). 18F-FDG PET showed severe hypometabolism in every infarcted territory, often extending beyond structural changes: ASPECTS differences were present in 7/10 patients for CT, 6/10 for DWI and 6/10 for FLAIR versus 18F-FDG PET/MRI, reaching the predefined 3-point threshold in 3/10 for CT versus PET/MRI. Because DWI, FLAIR and PET were acquired simultaneously at 72 hours (CT at 24 hours), the DWI/FLAIR-versus-PET comparisons are free of temporal confounding. Ipsilateral thalamic and crossed cerebellar diaschisis were each identified in 4/10 patients at 72 hours. Despite this more extensive hypometabolism, 9/10 patients achieved a favorable outcome (modified Rankin Scale ≤2) at 3 months. Hybrid 18F-FDG PET/MRI maps metabolic abnormality and remote network dysfunction invisible to structural imaging alone, adding a physiological dimension to ASPECTS-based evaluation of the reperfused brain.