Published ahead of print on February 12, 2009
doi: 10.3174/ajnr.A1495
Sodium MR Imaging Detection of Mild Alzheimer Disease: Preliminary Study
E.A. Mellona,
D.T. Pilkintona,
C.M. Clarkb,
M.A. Elliotta,
W.R. Witschey, 2nda,
A. Borthakura and
R. Reddya
a Department of Radiology, MMRRCC, University of Pennsylvania, Philadelphia, Pa
b Department of Neurology, University of Pennsylvania, Philadelphia, Pa
View larger version (37K):
[in this window]
[in a new window]
|
Fig 1. A, Representative coronal control (control C2) and AD (patient AD4) images are shown from the sections for region-of-interest analysis. The proton images demonstrate the anatomy of the brain in the corresponding sodium sections and were part of the dataset used for hippocampal volume determination. The sodium images are normalized to the ventricular signal intensity, scaled as shown with the color bar on the right, which is also used for B. The images were normalized to the brightest areas of intensity in the center of the image, seen clearly in these images as the lateral ventricles. The hippocampal volumes from the proton sets were coregistered to the sodium images and used to mask the hippocampuses as described in the methods. B, Shown is the corresponding section from a B1 map calculated from a spherical sodium phantom with contour lines added for each 10th percentile. This indicates excellent homogeneity over the areas of interest. The units are in B1 relative to the maximum in that section scaled to the same color bar. The maximum is found at the edges of the phantom near the struts of the birdcage.
| |
View larger version (47K):
[in this window]
[in a new window]
|
Fig 2. For each subject, the proton images underwent 3D co-registration and resectioning to match the sodium position for that subject and sodium voxel size. The top 3 images show from left to right: 1 section of the original proton volume, the corresponding section of the co-registered and resectioned (Morphed) proton volume, and the corresponding section of the sodium volume for that subject. The hippocampal volumes were computed from manual hippocampal masking on a section-by-section basis. The middle left image shows the hippocampal mask for the section of brain shown above. The transformation matrix obtained from the co-registration and resection of the proton volume was applied to the hippocampal mask to yield the mask in the center image for that morphed section. This was performed on a 3D basis, and the bottom line shows that transformation in 3D. The entire hippocampal volume mask is shown as a 3D rendering of the surface from a tilted superior-inferior perspective. The morphed hippocampal volume mask (bottom center) was applied to the sodium volume, and those pixels were averaged to obtain sodium enhancement.
| |
View larger version (7K):
[in this window]
[in a new window]
|
Fig 3. Compared is sodium enhancement with diagnosis (r2 = 0.53; P = .006). Sodium enhancement is taken as the average sodium enhancement of the right and left medial temporal lobes relative to ventricle. The vertical error bars represent the 95% confidence interval.
| |
View larger version (7K):
[in this window]
[in a new window]
|
Fig 4. Compared is diagnosis with mean hippocampal volume per subject normalized to total intracranial volume (r2 = 0.42; P = .034). The vertical error bars represent the 95% confidence interval.
| |
View larger version (13K):
[in this window]
[in a new window]
|
Fig 5. Plotted is unnormalized hippocampal volume against sodium enhancement for each brain hemisphere (20 hemispheres from 10 subjects; overall r2 = 0.50; P < .01). The square data points represent control hemispheres, and the circles represent AD hemispheres. The center solid line indicates the linear overall regression. The dashed lines indicate the linear regressions for the control (left: r2 = 0.24; P < .01) and AD (right: r2 = 0.40; P < .01) data points. Although a moderate correlation is observed for all groups, sodium enhancement still correlates with disease state even when controlling for hippocampal volumes.
| |
