Evaluation of brain metabolism in steno-occlusive carotid artery disease by proton MR spectroscopy: a correlative study with oxygen metabolism by PET.
Carotid occlusive diseases may cause ischemic changes in both the gray matter and the white matter as a result of hemodynamic compromise. To validate the use of proton magnetic resonance spectroscopy (MRS) in evaluating the carotid occlusive diseases, we compared changes in peaks of choline, in the sum of creatine and phosphocreatine, and in N-acetyl-aspartate (NAA) of the white matter with cortical oxygen metabolism measured by PET.


METHODS
Eleven patients with unilateral steno-occlusive carotid artery disease underwent PET and MRS. Ten age-matched healthy volunteers underwent MRS. No subjects had cortical infarction. MRS was performed bilaterally in the centrum semiovale. Regional blood flow, regional metabolic rate of oxygen (rCMRO2), and regional oxygen extraction fraction (rOEF) of the cerebral cortex were measured by the steady-state method with 15O gas.


RESULTS
The asymmetry index of the ratio of NAA to the sum of creatine and phosphocreatine (NAA/Cr) correlated positively with the asymmetry index of rCMRO2 (r = 0.77; P < 0.01). Because rCMRO2 is a marker of tissue viability, the NAA/Cr of the centrum semiovale may reflect viable neuronal cells. The asymmetry index of the ratio of choline to the sum of creatine and phosphocreatine (Cho/Cr) showed a significant positive correlation with the asymmetry index of rOEF (r = 0.65; P < 0.05). All but 1 patient with an increased Cho/Cr (>1.03) showed an increase in rOEF of the ipsilateral cortex (>0.56). This finding may indicate membrane damage caused by ischemia, because the centrum semiovale is the deep watershed zone.


CONCLUSIONS
The metabolic changes in the centrum semiovale detected by proton MRS reflect a hemodynamically compromised state and are useful in evaluating tissue viability.
Tsuchida
C
C
Department of Radiology and Biomedical Imaging Research Center, Fukui Medical University, Japan.
Kimura
H
H
Sadato
N
N
Tsuchida
T
T
Tokuriki
Y
Y
Yonekura
Y
Y
D000368:Aged; D000369:Aged, 80 and over; D001157:Arterial Occlusive Diseases / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000378:metabolism*; D001921:Brain / Q000000981:diagnostic imaging / Q000378:metabolism*; D002340:Carotid Artery Diseases / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000378:metabolism*; D002343:Carotid Artery, Internal; D016893:Carotid Stenosis / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000378:metabolism*; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption; D010103:Oxygen Isotopes; D012044:Regression Analysis; D015203:Reproducibility of Results; D014055:Tomography, Emission-Computed
D010103:Oxygen Isotopes