Standardized Expression of 18F-NAV4694 and 11C-PiB β-Amyloid PET Results with the Centiloid Scale

A common quantitative output value for PET measures of beta-amyloid (A beta) binding across tracers and methods would allow better comparison of data across sites and application of universal diagnostic and prognostic values. A method has recently been developed that generates a unit of measurement called the centiloid. We applied this method to 2-[2-F-18-fluoro-6-(methylamino)-3-pyridinyl]-1-benzofuran-5-ol (F-18-NAV4694) and C-11-Pittsburgh compound B (C-11-PiB) A beta images to derive the scaling factor required to express tracer binding in centiloids. Methods: Fifty-five participants, including 10 young controls (33 +/- 7 y old), underwent both C-11-PiB and F-18-NAV4694 imaging no more than 3 mo apart, with the images acquired 50-70 min after tracer injection. The images were spatially normalized and analyzed using the standard centiloid method and regions (cortex and whole-cerebellum reference) downloaded from the Global Alzheimer Association Interactive Network website. Results: SUV ratios (SUVRs) showed a strong correlation in tracer binding (F-18-NAV4694 SUVR = 1.09 x C-11-PiB SUVR - 0.08, R-2 = 0.99). The equation to convert F-18-NAV4694 to centiloids [100 x (F-18-NAV4694 SUVR - 1.028)/1.174] was similar to a published equation for C-11-PiB [100 x (C-11-PiB SUVR - 1.009)/1.067]. In the young controls, the variance ratio (F-18-NAV4694 centiloid SD divided by C-11-PiB centiloid SD) was 0.85. Conclusion: The results for both C-11-PiB and F-18-NAV4694 can now be expressed in centiloids, an important step that should allow better clinical and research use of A beta imaging. The standard centiloid method also showed that F-18-NAV4694 has slightly higher A beta binding and lower variance than C-11-PiB, important properties for detecting early A beta deposition and change over time.