Graphic plot analysis for estimating binding potential of translocator protein (TSPO) in positron emission tomography studies with [18F]FEDAA1106

Purpose[18F]FEDAA1106 is expected to be used for evaluating the regional density of the peripheral benzodiazepine receptor (also called TSPO) in several neurodegenerative disorders. Regarding the quantification, direct binding potential (BPND) has been reported to be preferable because of the variation of nondisplaceable distribution volume (VND) among individuals. However, the precise calculation of BPND is difficult in small regions or at voxel levels due to noise. Recently, a new graphical analysis (GA) was proposed to estimate VND in a direct way. In this paper, we evaluated two types of GA for reliable quantification of BPND in PET study with [18F]FEDAA1106 using computer simulations and human data.\nMethodsIn the simulations, time-activity curves were generated with various rate constants and noise levels, and the errors of BPND estimated by GA were analyzed by comparing with true values calculated from rate constants given for the simulations. Thereafter, in a human study with [18F]FEDAA1106 for healthy volunteers, BPND was estimated by two types of GA for region-of-interest (ROI) data. Parametric images of BPND were generated by two types of GA with or without wavelet-denoising.\nResultsSimulations showed that BPND by GA was well correlated with true values, despite an underestimation. GA reduced unreasonable estimates compared with a conventional nonlinear least-square fitting (NLS), although larger variation of BPND estimates was observed. In a ROI-based analysis of data obtained in a human study, BPNDs estimated by GA were well correlated with those generated by NLS, though they were underestimated. Parametric BPND images by GA could be improved with wavelet-denoising.\nConclusionGraphical analysis could provide BPND values with high stability and simple calculation in both ROI-based and voxel-based analyses of [18F]FEDAA1106 data