Feasibility of 18F‐florzolotau Quantification in Patients with Alzheimer’s Disease Based on an MRI‐free Tau PET Template

Abstract

AbstractBackgroundQuantification of tau accumulation using positron emission tomography (PET) is critical for the diagnosis of Alzheimer’s disease (AD). This study aimed to evaluate the feasibility of 18F‐florzolotau quantification in patients with AD using a magnetic resonance imaging (MRI)‐free tau PET template, since individual high‐resolution MRI is costly and not always available in practice.Method 18F‐florzolotau PET and MRI scans were obtained in a discovery cohort including 1) patients within the AD continuum (n = 87), 2) cognitively impaired patients with non‐AD (n = 32), and 3) cognitively unimpaired subjects (n = 24). The validation cohort comprised 24 patients with AD. Following MRI‐dependent spatial normalization (standard approach) in randomly selected subjects (n = 40) to cover the entire spectrum of cognitive function, selected PET images were averaged to create the 18F‐florzolotau‐specific template. Standardized uptake value ratios (SUVRs) were calculated in five predefined regions of interest (ROIs) including entorhinal cortex, inferior temporal cortex, temporal meta‐ROI, temporoparietal cortex, and neocortical areas. MRI‐free and MRI‐dependent methods were compared in terms of continuous and dichotomous agreement, diagnostic performances, and associations with specific cognitive domains.ResultMRI‐free SUVRs had high continuous and dichotomous agreement with MRI‐dependent measures for all ROIs (intraclass correlation coefficient ≥ 0.980; agreement ≥ 94.5%). Similar findings were observed for AD‐related effect sizes, diagnostic performances with respect to categorization across the cognitive spectrum, and associations with cognitive domains. The robustness of the MRI‐free approach was confirmed in the validation cohort.ConclusionThe use of an 18F‐florzolotau‐specific template is a valid alternative to MRI‐dependent spatial normalization, improving the clinical generalizability of this second‐generation tau tracer.