COMPARISON OF ANATOMICALLY-DEFINED VERSUS PHYSIOLOGICALLY-BASED REGIONAL LOCALIZATION - EFFECTS ON PET-FDG QUANTITATION

The potential of anatomic imaging to improve the quantitative accuracy of functional brain imaging through refined regional definition is wi dely accepted. However, there are little data addressing the impact of approach to regional localization on quantitation of metabolic images in the absence of gross structural pathology. We compared MRI-based v ersus PET-based approaches to the analysis of PET F-18-fluorodeoxygluc ose (FDG) images using a standard adjustable template based on simple geometric regions. For the MRI-based approach, templates and individua l regions were adjusted to each individual's anatomy, whereas the PET- based definition involved only global proportional adjustment of the s tandard templates. Metabolic rates for glucose and volume-to-whole bra in ratios were determined by two operators for 78 volumes of interest in five subjects. Pairwise correlations indicated high interoperator a greement for each approach and high intraoperator agreement for MRI-ba sed Versus PET-based metabolic values. The stability of the metabolic rates and ratios among operators and analysis approaches was supported by low coefficients of variation across measurements and small averag e differences in paired comparisons. Thus, within the current spatial resolution of PET imaging, quantitation of metabolic images is relativ ely robust to image analysis approach in the absence of gross structur al abnormality. To take advantage of the greater quantitative accuracy promised by high-resolution anatomic and functional imaging, more ref ined delineation of anatomic images will be necessary.