Parametric Binding Images of the TSPO Ligand 18F-DPA-714

F-18-labeled N,N-diethyl-2-(2-[4-(2-fluoroethoxy)phenyl]-5,7-dimethylpyrazolo[1,5-alpha]pyrimidine-3-yl)acetamide (DPA-714) is a radio-ligand for the 18-kDa translocator protein. The purpose of the present study was to identify the best method for generating quantitative parametric images of F-18-DPA-714 binding. Methods: Ninety-minute dynamic F-18-DPA-714 PET scans with full arterial sampling from 6 healthy subjects and 9 Alzheimer disease (AD) patients were used. Plasma-input based Logan graphical analysis and spectral analysis were used to generate parametric volume of distribution (V-T) images. Five versions of Ichise, reference Logan, and 2 basis function implementations (receptor parametric mapping and simplified reference tissue model 2 [SRTM2]) of SRTM, all using gray matter cerebellum as the reference region, were applied to generate nondisplaceable binding potential (BPND) images. Results: Plasma-input Logan analysis (r(2) = 0.99; slope, 0.88) and spectral analysis (r(2) = 0.99, slope, 0.93) generated estimates of VT that correlated well with values obtained using nonlinear regression. BPND values generated using SRTM2 (r(2) = 0.83; slope, 0.95) and reference Logan analysis (r(2) = 0.88; slope, 1.01) correlated well with nonlinear regression based estimates. Conclusion: Both Logan analysis and spectral analysis can be used to obtain quantitatively accurate VT images of F-18-DPA-714. In addition, SRTM2 and reference Logan analysis can provide accurate BPND images. These parametric images could be used for voxel-based comparisons.