The use of positron emission tomography (PET) in quantitative fluorodeoxyglucose (FDG) studies of aging and dementia has been limited by partial volume effects, A general method for correction of partial volume effects (PVE) in PET involves the following common procedures: segmentation of MRI brain images into gray matter (GM), white matter (WM), cerebral spinal fluid (CSF), and muscle (MS) components; MRI PET registration; and generation of simulated PET images. Afterward, two different approaches tan be taken, The first approach derives first a pixel-by-pixel correction map as the ratio of the measured image to the simulated image [with realistic full-width at half-maximum (FWHM)]. The correction map was applied to the MRI segmentation image, Regions of interest (ROI's) can then be applied to give results free of partial volume effects. The second approach uses the ROI values of the simulated ''pure'' image (with negligible FWHM) and those of the simulated and the measured PET images to correct for the PVE effect, By varying the ratio of radiotracer concentrations for different tissue components, the in-plane FWHM's of a three-dimensional point spread function, and the ROI size,,ve evaluated the performance of these two approaches in terms of their accuracy and sensitivity to different simulation configurations, The results showed that both approaches are more robust than the approach developed by Muller-Gartner ef al., and the second approach is more accurate and more robust than the first. In conclusion, we recommend that the second approach should be used on FDG PET images to correct for partial volume effects and to determine whether an apparent change in GM radiotracer concentration is truly due to metabolic changes.
