Comparison between the μ-maps of different PET tracers: 18F-FDG and 18F-flutemetamol, generated by the attenuation correction method without external radiation source

Introduction: Currently, external radiation sources such as CT are widely used for attenuation correction in PET scans. On the other hand, increased radiation exposure to the lens and other parts has been a problem to consider. We evaluated the attenuation correction method using the dedicated brain PET scanner, which generates attenuation maps from emission data without external radiation sources (Mizuta T, et. al. ANM, 2022, in press).

Methods: For this study, the TOF dedicated brain PET (SET-5002: prototype of BresTome, Shimadzu Corp., Japan) was used. The μ-maps obtained with two different PET tracers (18F-FDG and 18F-Flutemetamol) in the same subjects were compared. Two types of μ-maps were produced by PET imaging with different PET tracers in the same six subjects. We measured the μ-values by setting the regions of interest in three regions: extracranial (air), intracerebral (white matter and gray matter), and bone on each μ-maps.

Results: The mean μ-values for all cases of μ-maps from the two tracers was 0.0936±0.0018 for 18F-FDG and 0.0974±0.0024 for 18F-flutemetamol in the intracerebral, while in bone was 0.123±0.0142 and 0.123±0.0218, respectively. There was no significant difference between these two areas (p>.05). Moreover, the μ-value in the extracerebral (air) region was 0 in both subjects.

Conclusions: These results suggest that the obtained μ-maps may be comparable even when generated by different PET tracers. However, since the number of cases in this study is small, we need to increase the number of cases in the future, and we also need to evaluate regional difference.