Figure 2.

A PET-based subtyping of PPA, PNFA, CBS and PSP. (A) Representative axial (left) and coronal (right) images of radioactivity SUVRs at 90–110 min after ¹⁸F-florzolotau administration. The arrowheads of normal size indicate enhanced parenchymal radioligand retentions characteristic of each putative tau topology subtype. The smaller arrowheads denote radioactivity accumulations in the choroid plexus supposedly unrelated to tau depositions. Radio signal intensification primarily in the frontotemporal regions and less involvement of posterior and subcortical areas are suggestive of Pick’s disease–type 3RT aggregations in a case with PPA (PPA1), while negativity for tau depositions is indicated in another case with PPA (PPA2). Radio signal increases predominantly in subcortical regions implying PSP- or CBD-type 4RT deposits in a case with PNFA (PNFA4). A case with Aβ-PET–positive CBS (CBS3) exhibited widespread and highly intensified limbic and neocortical radioligand accumulations involving temporo-parietal regions, which is indicative of CBS due to Alzheimer’s disease pathologies. (B) The characterization of putative brain pathologies in three PPA (PPA1–3), four PNFA (PNFA1–4), three CBS (CBS1–3) and one PSP (PSP1) patients by the visual read of tau PET images. Cases with PPA were characterized as 3RT-like (PPA1) and tau-negative (PPA2 and 3), whereas all cases with PNFA were categorized as 4RT-like. Image findings in cases with CBS were either 4RT-like (CBS1, 2) or Alzheimer’s disease–like (CBS3), and radio signal distribution in the PSP-FTD case was consistent with 4RT-like pathology. In each subject, three axial, one coronal and one sagittal section providing characteristic information are presented from the left. A, anterior; L, left, P, posterior; R, right.