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Correction for Partial-Volume Effects on Brain Perfusion SPECT in Healthy Men

¹ Department of Radiology, National Center Hospital for Mental, Nervous, and Muscular Disorders, National Center of Neurology and Psychiatry, Tokyo, Japan
² Department of Neuropsychiatry, Institute of Clinical Medicine, University of Tsukuba, Ibaraki, Japan
³ Department of Nuclear Medicine, The Second Clinical Hospital of China Medical University, Shen-Yang City, China
⁴ Department of Geriatric Medicine, National Center Hospital for Mental, Nervous, and Muscular Disorders, National Center of Neurology and Psychiatry, Tokyo, Japan

View larger version (30K): [in a new window]   FIGURE 1. Procedures of correction algorithm for PVEs in SPECT data using MR images. Original SPECT image (B) was coregistered to MRI after scalp editing (D) of original MR image (A) using binary mask for whole brain (C). Original MRI was segmented into white matter (F) and gray matter (G). Segmented images were convoluted with point spread function of SPECT device. White-matter SPECT image (H) was then simulated from convoluted white-matter MR image (H). For this simulation, maximum count for white matter of SPECT, ROI was automatically determined by setting threshold to >95% of maximum count density of white-matter MR images (J). Gray-matter SPECT images (K) were obtained by subtraction of simulated white-matter SPECT image from original SPECT image coregistered to MRI (E). Lastly, gray-matter SPECT image (K) was divided by convoluted gray-matter MR image (I) on voxel-by-voxel basis. Gray-matter SPECT image with PVE correction (M) was finally obtained from application of binary mask for gray matter (L) to divided image.

View larger version (48K): [in a new window]   FIGURE 2. Phantom study for validation of correction algorithm for PVEs. (A–D) SPECT images for Hoffman phantom before and after PVE correction. Division of original SPECT image (A) for Hoffman 3D brain phantom by MR image convoluted with point spread function of SPECT scanner (B) provided SPECT image corrected for PVEs (C). Correction map (D) was created by division of SPECT image corrected for PVEs (C) by original SPECT image (A). PVE correction provided much more homogeneous tracer distribution throughout phantom than that in original SPECT. (E and F) Relationship between regional SPECT counts and regional gray-matter volume in Hoffman phantom. (E) Regional SPECT counts showed linear correlation with regional volume obtained from convoluted MRI before PVE correction in scatter plots. (F) After PVE correction, linear relationship became flat, which indicates independence of SPECT counts from regional volume.

View larger version (48K): [in a new window]   FIGURE 3. Spatially normalized gray-matter SPECT images for average and SDs in 52 healthy men before and after PVE correction. Note more homogeneous distribution and less SD of rCBF after PVE correction.

View larger version (140K): [in a new window]   FIGURE 4. SPM99 results for differences of absolute rCBF before and after PVE correction. Warm color bar and cool color bar represent increase and decrease of rCBF after PVE correction, respectively.

View larger version (42K): [in a new window]   FIGURE 5. Maximum intensity projections of SPM99 results for negative correlation of adjusted rCBF with advancing age before (top) and after (bottom) PVE correction. Height threshold <0.001, corrected for multiple comparisons.

View larger version (40K): [in a new window]   FIGURE 6. Maximum intensity projections of SPM99 results for positive correlation of adjusted rCBF with advancing age before (top) and after (bottom) PVE correction. Height threshold <0.001, corrected for multiple comparisons.

View larger version (53K): [in a new window]   FIGURE 7. Maximum intensity projections of SPM99 results for positive (top) and negative (bottom) correlation of regional gray-matter volume with advancing age. Height threshold <0.001, corrected for multiple comparisons.