IMPROVED 3D CORRECTION FOR PARTIAL VOLUME EFFECTS IN BRAIN SPECT

An improved method for correction of partial volume effects (PVE) in b rain SPECT is proposed. It is fully three-dimensional, does not requir e particular patient positioning, and works with scans only partially covering the brain. The location of functionally inactive brain region s (primarily cerebrospinal fluid) is extracted from high-resolution MR I. An automatic 3D registration algorithm then determines the geometri c transformation between MRI and SPECT. Correction consists of: 1) cou nting the volumetric active/inactive ratio in each volume element of t he functional scan using the measured SPECT point spread function; 2) correcting the functional measures according to these ratios; 3) fusin g functional and anatomical information at the resolution of MRI. Quan titative validation was performed using a phantom containing a test re gion in which multiple parallel acrylic plates thinner than SPECT reso lution created high PVE, as well. as a large reference region not suff ering from PVE. Reference activity was recovered in the test region wi th an accuracy of 1-3%. The method was applied to clinical images demo nstrating a combination of hypoperfusion and cortical atrophy. The com posite anatomical-functional corrected images, in which the main sulci are visible, yield better differentiation between decreased function and focal atrophy. (C) 1997 Wiley-Liss, Inc.