| Objective: The metabolites (NAA, Lac, Cho, Cr) in the infarction core zone, peripheral zone and surrounding zone during different stages after infarction were detected by1H proton magnetic resonance spectroscopy (1H-MRS) to analyze the dynamic changes of acute cerebral infarction metabolites and to explore the injury mechanism of infracted tissue.Materials and Methods:40healthy adults who underwent multi-voxel1H-MRS examination by3.0T MR system were divided into two groups by age:20cases in youth groups, including9males and11females, aged25to49years, mean age32.9±6.34years old;20cases in elderly group, including12males and8females, aged50to80years, mean age62.0±6.29years old. The basal ganglia section was selected as interest level on axial T2WI.The volume of interest(VOI) was bilaterally symmetrical, including bilateral caudate head, putamen, dorsal thalamus, cingulated gyrus gray matter and white matter in frontal lobe. N-acetyl aspartate (NAA), choline compounds (Cho)and creatine (Cr) concentration in areas mentioned above was measured with a software package,while the computer calculated the NAA/Cr, Cho/Cr ratios automatically by using Cr as a reference. The difference of metabolites between different age healthy adults and different regions of the brain were compared to analyze the distribution of metabolites.30cases with acute basal ganglia infarction at different stages were enrolled in this study, including18males and12females, age range44-81years, mean age62.6years old. Patients were divided into four groups by the time of onset:7hyperacute (<6h) cases,10acute phase (6-24h) cases,8early subacute (1～3d) cases and5late subacute (3～7d) cases.20age-matched healthy adults without any cerebral ischemic symptoms and signs were selected as control group. All patients underwent conventional MRI and two-dimensional multi-voxel1H-MRS examination.The metabolites(NAA, Lac, Cho, Cr, Lac/NAA) content in infarction core zone, peripheral zone and surrounding zone during different stages were measured and recorded,as well as the metabolites content in contralateral mirror area and corresponding brain regions of healthy adults. Metabolite contents of contralateral brain tissue and the corresponding brain areas in control group were compared,as well as the metabolite contents in different infarction regions during different periods. All data were analyzed by SPSS17.0software package, and P<0.05was considered statistically significant.Results: Compared with the youth group, frontal lobe gray and white matter caudate head, putamen and dorsal thalamus NAA in the elderly group were significantly lower (P<0.05), while Cho in frontal white matter, caudate head putamen and thalamus significantly increased (P<0.05). The left frontal white matter, caudate head, putamen and thalamus NAA, Cho were significantly higher than those in the right side (P<0.05),while no significant difference was found between the bilateral frontal lobe gray matter. NAA/Cr was highest in the dorsal thalamus and Cho/Cr was highest in the frontal white matter. Compared with the corresponding brain regions of healthy adults, metabolite contents (NAA,Cho, Cr) in infarction contralateral mirror area did not change significantly during any phases after infarction (P>0.05). NAA in infarction core zone was significantly lower than contralateral mirror area at each phase (P<0.001).NAA in peripheral zone during hyperacute phase slightly reduced compared with the contralateral mirror area (P>0.05), and reduced further after acute phase until there is no significant statistical differences with infarction core zone(P>0.05). NAA in peripheral zone during each phase were not significantly reduced (P>0.05). Lac in infaction core zone was significantly higher than that in the peripheral and surrounding zone during hyperacute phase (P<0.05), while there was no significant difference during acute and subacute phase (P>0.05). More and more voxels with NAA reduction and Lac were detected from hyperacute to acute phase,while no increase after early subacute phase. Lac/NAA in infarction core zone was significantly higher than that in the peripheral zone(P<0.05), while no significant difference between the two regions during subacute period(P>0.05). Cho in the infarction core was significantly reduced during subacute phase (P<0.05), Cr was significantly reduced during hyperacute, acute and early subacute phase(P<0.05), and Cr in the peripheral zone was reduced transiently during acute phase (P<0.05). Conclusions:1.The concentration of metabolites was different in different age healthy adults, the elder population have a lower brain tissue NAA level and a higher Cho level.2.The metabolites distribution in different anatomical regions of healthy adults was different, NAA and Cho concentration of right-handed people was higher in the left hemisphere than that in the right side. NAA/Cr tended to increase while Cho/Cr tended to reduce from ventral to dorsal.3.Reduced NAA and obvious Lac peak could be detected in infarction core zone during hyperacute phase. Lac peak appeared in peripheral zone during hyperacute phase, while reduced NAA was detected during acute phase; Lac in surrounding zone increased transiently during hyperacute phase and no NAA reduction during each phase.4.IP existed in peripheral zone during acute phase and disappeared during subacute phase.5.Both the infarction core and the peripheral zone were heterogenous during the hyperacute and acute phase.6.Cho and Cr level in ischemic brain tissue is not constant.Therefore,it’s not reliable to calculate metabolite ratios using Cho, Cr as a reference.7.Metabolites in contralateral brain did not change significantly at each infaction phase.As a consequence,it can be reference for evaluating the metabolite change in infarction side. |
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