Proton MR Spectroscopy in Patients with Complex Partial Seizures: Single-Voxel Spectroscopy versus Chemical-Shift Imaging
Yuan-Yu Hsu,a,
Chen Changa,
Chen-Nen Changa,
Nai-Shin Chua,
Kun-Eng Lima and
Jee-Ching Hsua
a From the Departments of Radiology (Y-Y.H., K-E. L), Neurosurgery (C-N. C.), Neurology (N-S. C.), and Anesthesia (J-C. H.), Chang Gung Memorial Hospital; and the Institute of Biomedical Sciences (C. C.), Academia Sinica; Taipei, Taiwan, Republic of China.
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FIG 1. Proton SVS study of the left hippocampus of a healthy adult.
A, This coronal T2-weighted image (3000/85/1) is the central section for voxel positioning, about 1 to 2 mm anterior to the ipsilateral internal acoustic canal. The voxel is 20 x 20 x 20 mm3. Part of the hippocampal head and body are included for measurement.
B, There are three major peaks in this proton spectrum: NAA at 2.0 ppm, Cr at 3.0 ppm, and Cho at 3.2 ppm. The NAA peak is usually, but not necessarily, higher than the other two.
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FIG 2. Proton CSI study of the right hippocampus of a healthy adult.
A, This transverse T2-weighted MR image (6.32/3.00/2), approximately parallel to the long axis of the hippocampus, illustrates the position of the VOI (about 40 x 20 mm2) inside the field of view (160 x 160 mm2), which has 16 x 16 phase encoding. The section thickness is 15 mm, the in-plane resolution is 10 x 10 mm2, and the voxel size is 10 x 10 x 15 mm3. The lateral margin of the VOI is about 0 to 2 mm lateral to the lateral border of the ipsilateral temporal horn, and the anterior margin is 5 to 10 mm anterior to the peduncles.
B, The resultant spectral map has eight voxels arranged in a two by four matrix. The spectral profile is similar to that of a single-voxel study. Owing to field inhomogeneity caused by anatomic complexity, in many cases the spectral resolution is worse in the more anterior voxels than in the posterior ones.
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FIG 3. Distribution of hippocampal NAA/(Cho+Cr) ratios in control subjects (white bars) and in patients with complex partial seizures (black bars).
A, Proton SVS study.
B, Proton CSI study: anterior hippocampus.
C, Proton CSI study: posterior hippocampus.
A significant decrease in the NAA/(Cho+Cr) ratio of the patient group is seen in all three data sets (P = .00003, P = .001, and P = .002, respectively).
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FIG 4. 28-year-old man with complex partial seizures for 11 years.
A, The proton SVS study of the right hippocampus shows a low NAA peak, a high Cho peak, and a small NAA/(Cho+Cr) ratio (0.45).
B, The study of the left hippocampus has a normal spectral profile and a normal NAA/(Cho+Cr) ratio (0.58).
The T2-weighted MR images, 3000/85/1, also reveal abnormal hyperintensity in the right hippocampus.
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FIG 5. 20-year-old woman with complex partial seizures for 14 years.
A, Proton CSI study of the right hippocampus shows a normal NAA/(Cho+Cr) ratio in both anterior and posterior portions (0.59 and 0.55, respectively).
B, Conversely, the study of the left hippocampus shows a reduced NAA/(Cho+Cr) ratio in both anterior and posterior portions (0.39 and 0.48, respectively). The MR imaging study (not shown) revealed atrophy of the left hippocampus.
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