RT Journal Article SR Electronic T1 11C-DTBZ and 18F-FDG PET Measures in Differentiating Dementias JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 936 OP 944 VO 46 IS 6 A1 Robert A. Koeppe A1 Sid Gilman A1 Aniket Joshi A1 Suyu Liu A1 Roderick Little A1 Larry Junck A1 Mary Heumann A1 Kirk A. Frey A1 Roger L. Albin YR 2005 UL http://jnm.snmjournals.org/content/46/6/936.abstract AB Accurate, early differentiation of dementias will become increasingly important as new therapies are introduced. Differential diagnosis by standard clinical criteria has limited accuracy. PET offers the potential to increase diagnostic accuracy. 18F-FDG studies detect metabolic abnormalities in demented patients, but with limited specificity. PET also offers the ability to quantify other biochemical markers that can yield additional useful diagnostic information. We demonstrate that (+)-11C-dihydrotetrabenazine (11C-DTBZ) studies, which provide an index of nigrostriatal terminal density (distribution volume; DV), also provide a measure of transport (K1) that produces information comparable to the metabolic measure of 18F-FDG. Methods: Fifty-two patients and 19 control subjects underwent both 11C-DTBZ and 18F-FDG PET scans. Seven had the clinical diagnosis of frontotemporal dementia (FTD), 25 had Alzheimer’s disease (AD), and 20 had dementia with Lewy bodies (DLB). DTBZ scans provided maps of K1 and DV, whereas 18F-FDG scans provided maps of glucose metabolism. Correlation analyses were performed between the different PET measures both within and across subjects. Discriminant analysis using logistic regression compared the performance of 11C-DTBZ K1 and 18F-FDG in differentiating subject groups. Three experienced PET researchers participated in an interrater reliability study using both 11C-DTBZ K1 and 18F-FDG images. Results: Within-subject correspondence between 11C-DTBZ K1 and 18F-FDG measures was high, with correlations averaging 0.92. Correlations between the 11C-DTBZ DV and either K1 or 18F-FDG were far lower, averaging 0.37 and 0.31, respectively, indicating the much higher degree of similarity in information provided by K1 and 18F-FDG compared with the very different information provided by 11C-DTBZ DV. Discriminant analysis demonstrated that 11C-DTBZ K1 and 18F-FDG yielded similar levels of sensitivity and specificity for differentiating the subjects in this study. Including 11C-DTBZ DV in addition to either K1 or 18F-FDG improved discrimination between groups. The raters classified PET scans nearly equivalently using K1 and 18F-FDG. Conclusion: Multiple PET measures, whether 2 parameters from a single PET study such as 11C-DTBZ K1 and DV, or 2 parameters from different studies such as 18F-FDG and 11C-DTBZ DV, offer complementary information useful for diagnosing dementias. K1 and DV images generated from a single 11C-DTBZ scan provide as much diagnostic information as 2-scan studies using both 11C-DTBZ and 18F-FDG.