HAI Book 2025 - Flipbook - Page 67
Bettcher, Brecca
Longitudinal amyloid burden with combined [11C]PiB and [18F]NAV4694 PET
Scans
Brecca Bettcher1, Max McLachlan1, Matthew Zammit1, Andrew McVea1, Alexandra DiFilippo1,
Dhanabalan Murali1, Ali Pirasteh1, Tobey Betthauser1, Sterling Johnson1, Bradley Christian1
1
University of Wisconsin-Madison School of Medicine and Public Health and Waisman Center, Madison, WI, US
Background: Amyloid tracer [18F]NAV4694 is a desirable alternative to [11C]PiB, possessing similar imaging
characteristics and favorable distribution logistics. While Centiloids have proven reliable in cross-sectional
studies, this work examines the accuracy of amyloid measures when transitioning from [11C]PiB to [18F]NAV4694
in longitudinal studies.
Methods: 24 Participants with g1 [11C]PiB scans, followed by a [18F]NAV4694 scan, were examined from ongoing
AD studies at the University of Wisconsin (Table 1). PET images were realigned, summed 50-70min, coregistered
to associated T1 weighted MRIs, normalized to MNI space, and smoothed by 6mm. Cortical SUVR and Centiloids
(CL) were calculated using a whole cerebellum reference region. Rate of amyloid accumulation (CL/year) in NAV
amyloid positive individuals was compared to published values. Longitudinal analyses were performed for
participants with at least two PiB scans, allowing for direct comparison of PiB1-to-PiB2 changes and PiB2-to-NAV
changes. An amyloid negative subset was defined as participants with > 1 PiB scan and who remained firmly
amyloid negative (CL < 15) across all observations.
Results: Within participant PiB and NAV images were virtually indistinguishable by visual inspection (Figure 1b).
The average rate of amyloid accumulation in amyloid positive participants is 5.3± 2.3 CL/year, consistent with
published amyloid accumulation rate of ~4-5 CL/year in the neurotypical population (Yi Su et al, 2018). In the
amyloid negative subset, rate of amyloid accumulation (CL/year) in PiB1-to-PiB2 vs PiB2-to-NAV demonstrated no
significant difference (p = 0.27) (Figure 2). In all participants with > 1 PiB scan, differences in PiB2-to-NAV white
matter signal exhibited higher variability than PiB1-to-PiB2 (p = 0.0003) but were not significantly different in
mean (p = 0.15).
Conclusion: This study has investigated a direct longitudinal within participant comparison of PiB-to-PiB vs PiBto-NAV amyloid accumulation. [18F]NAV4694 demonstrated both consistency in trending amyloid accumulation
and constancy in sustained amyloid negative participants compared to [11C]PiB.
HAI2025 - 67
