Cortical Brain Surface Mapping for Studying Partial Volume Effects in Brain Fdg Pet Images

Objectives Due to the small thickness of cortical gray matter in the brain, biological interpretation of image values in the cortical regions on FDG PET images is confounded by tissue atrophy and partial volume effects, especially in patients with Alzheimer Disease (AD). In this study, we developed a method that employs a well established MRI-based cortical brain surface mapping technique to account for partial volume effects on brain FDG PET images, and demonstrated the method in a group of normal elderly subjects. Methods 15 healthy elderly subjects without AD were included in this study. Both 3D MRI (SPGR) and FDG PET scans were performed on each subject. PET and MRI scans were mutually coregistered and aligned into the ICBM standard stereotaxic space, and cortical surface models were extracted from the MRIs. To better align data across subjects, each cortical model was elastically warped by aligning sulcal features in the 2D surface parameter space. The cortical thickness was computed from the distance between the gray matter/CSF and gray/white matter boundaries in the segmented MRI scan. At each cortical location the corresponding FDG value (normalized relative to the mean value for the whole brain)was evaluated. For each cortical point there is a distribution, across subjects, of FDG signal and cortical thickness. The correlation and the slope of a linear regression between FDG and cortical thickness were determined for each of these cortical voxels forming a correlation map across the cortex.