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Three-Dimensional Stereotactic Surface Projection Analysis of Macaque Brain PET: Development and Initial Applications

Department of Internal Medicine (Nuclear Medicine) and Neuroscience Graduate Program, University of Michigan Medical School, Ann Arbor, Michigan; Medical and Pharmacological Research Center Foundation, Hakui City; and Central Research Laboratory, Hamamatsu Photonics K.K., Hamamatsu, Japan

View larger version (125K): [in this window] [in a new window]   FIGURE 1. Effects of anatomic standardization. Top row represents stereotactic reference MR image set (REF) averaged across 6 monkeys. Second through bottom rows represent SD maps created from MR images (scalp and skull removed) across 6 monkeys with stereotactic realignment alone and no linear scaling (NS), with linear scaling (LS), and with linear scaling and nonlinear warping (LS+NW), respectively. Millimetric scales represent slice levels from anteroposterior commissures (ACPC) in stereotactic space. Areas of higher SDs indicate greater anatomic mismatches. Dramatic reduction of mismatches is seen from NS to LS, and further improvement is seen from LS to LS+NW.

View larger version (21K): [in this window] [in a new window]   FIGURE 2. Histogram comparing effects of anatomic standardization. Horizontal axis represents SD for each individual pixel for T1-weighted summed MR images across 6 monkeys. Vertical axis represents percentage of brain volume, calculated as number of pixels in each range divided by total number of pixels in brain. Curves illustrate stereotactic realignment alone with no linear scaling (NS), with linear scaling (LS), and with linear scaling and nonlinear warping (LS+NW).

View larger version (114K): [in this window] [in a new window]   FIGURE 3. Metabolic variances of aged conscious monkey brains. Images were created from calculation of coefficient of variation (COV) at each pixel in 3-dimensional SSP format across 5 monkeys. Top row shows right lateral (RT.LAT), left lateral (LT.LAT), and superior (SUP) aspects of brain, and bottom row represents right medial (RT.MED), left medial (LT.MED), and posterior (POST) aspects of brain. Highest metabolic variance is seen bilaterally in region of central sulcus.

View larger version (73K): [in this window] [in a new window]   FIGURE 4. Metabolic comparison between aged and young monkeys. Top row represents 3-dimensional SSP of mean pixel values of cerebral metabolic rate of glucose (CMRglc, µmol/100 g/min) averaged across 6 young monkeys. Middle row represents 3-dimensional SSP mean pixel values of CMRglc across 5 aged monkeys. Bottom row represents 3-dimensional SSP of statistical z scores (Z) representing significance of regional metabolic reduction of aged group compared with young group. Images are shown as right lateral (RT.LAT), left lateral (LT.LAT), right medial (RT.MED), and left medial (LT.MED) aspects of brain. Higher pixel intensities in first 2 rows represent greater metabolic activities, and higher pixel intensities in bottom z score map indicate greater metabolic reductions associated with aging.

View larger version (94K): [in this window] [in a new window]   FIGURE 5. Metabolic comparison between aged monkeys and humans. Images represent 3-dimensional SSP of mean pixel values of normalized cerebral metabolic rate of glucose (Norm CMRglc) across 5 aged healthy humans (top row) and 5 aged monkeys (middle row) in left lateral (LT.LAT), left medial (LT.MED), superior (SUP), and inferior (INF) aspects of brain. Bottom row represents actual size of rhesus monkey brain compared with human brain. Images in middle row are magnified (x2.25) for better clarity.