Standardized Expression of super(18)F-NAV4694 and super(11)C-PiB beta -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- super( 18)F-fluoro-6-(methylamino)-3-pyridinyl]-1-benzofuran- 5-ol ( super(18)F-NAV4694) and super(11)C-Pittsburgh compound B ( super(11)C-PiB) A beta images to derive the scaling factor required to express tracer binding in centiloids. Fifty-five participants, including 10 young controls (33 plus or minus 7 y old), underwent both super( 11)C-PiB and super(18)F-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. SUV ratios (SUVRs) showed a strong correlation in tracer binding ( super(18)F-NAV4694 SUVR = 1.09 x super(11)C-PiB SUVR - 0.08, R super(2) = 0.99). The equation to convert super(18)F-NAV4694 to centiloids [100 x ( super(18)F-NAV4694 SUVR - 1.028)/1.174] was similar to a published equation for super(11)C-PiB [100 x ( super(11)C-PiB SUVR - 1.009)/1.067]. In the young controls, the variance ratio ( super(18)F-NAV4694 centiloid SD divided by super(11)C-PiB centiloid SD) was 0.85. The results for both super( 11)C-PiB and super(18)F-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 super(18)F-NAV4694 has slightly higher A beta binding and lower variance than super(11)C-PiB, important properties for detecting early A beta deposition and change over time.