Support of visual interpretation of amyloid-ß PET by co-registration to the early uptake image

Ziel/Aim Visual interpretation of amyloid-ß (Aß) PET is challenging in 10-20Ĩ % of the cases, often due to brain atrophy. Co-registration with individual T1 w-MRI is useful in these cases, but MRI is not always available. This study tested co-registration of the Aß PET image with an early uptake image to support interpretation of Aß PET.

Methodik/Methods 31 patients were included retrospectively: 6 patients with florbetaben (FBB) PET including an early uptake image from clinical routine and 25 ADNI MCI patients with FBB PET and FDG PET (as replacement of early FBB uptake image). Both PET images were co-registered to the individual high-resolution MRI. Cortical tracer uptake in Aß PET was interpreted (Aß-negative or Aß-positive) in 4 ROIs: temporal, frontal, parietal cortex, posterior cingulate cortex/precuneus (PC2). Visual interpretation was performed by a nuclear medicine resident in the following settings (randomized order): (A) late Aß image alone, (B) late and early Aß image combined, (C) late Aß image and MRI combined. Certainty about the interpretation was scored from 0 (very uncertain) to 5 (very certain).

Ergebnisse/Results 52  % of the patients were interpreted Aß-positive (setting A). The rate of discrepancy between setting B and setting A was 13  %, both on patient and ROI base. The rate of discrepancy was smallest in PC2 (6  %) and largest in the parietal cortex (23  %). The certainty of the binary ROI Aß interpretation was 3.74 ± 0.95, 4.59 ± 0.60, and 4.26 ± 0.82 in setting A, B, and C, respectively (all paired t-test p < 0.0005). The increase in certainty in setting B relative to setting A was largest in temporal cortex and PC2.

Schlussfolgerungen/Conclusions These findings suggest that co-registration with an early uptake image supports visual interpretation of Aß PET. The small improvement of certainty by co-registration with the early PET image compared to individual MRI is due to better matching of spatial resolution between the two PET images.