| Objective: Cerebral oxygen metabolism plays an important role in maintaining the normal function of the brain, and also is the basic source of energy to maintain the nervous functions. The single-shot asymmetric spin-echo echo-plannar-imaging(ASE EPI) and three-dimensional pseudo Continuous Arterial Spin Labeling imaging(p CASL)were performed to analysis cerebral blood flow(CBF) and oxygen extraction fraction(OEF) of normal subjects changes by age, and provide a reference for the further study of cerebral oxygen metabolism and cerebral disease. Meanwhile, using the p CASL combined with the ASE EPI to observe the OEF and CBF’s change in acute cerebral infarction, and explore its application value in clinical practice.Subjects and Methods: The 75 normal subjects were performed using GE SIGNA HDX 3.0T MRI for T1 WI, T2 WI, DWI, p CASL and ASE EPI scanning. After Images scanned, SPM8 based on Matlab were used for CBF and OEF data processing and statistical analysis. Preprocessing consists of slice timing, eddy current and motion correction,the calculated of CBF and OEF image registering to MNI standard space index and images smoothing. After data preprocessing, in the SPM8 software, a Multiple Regression controlling for age effect was used for CBF and OEF in all normal subjects. Take the whole brain tissue as a mask to do the correlation analysis based on the voxel level,to evaluate the brain CBF and OEF changed with age. The statistical significance level was set as P < 0.05 by the false discovery rate correction. The 13 cases of acute cerebral infarction patients were performed using GE SIGNA HDX 3.0T MRI for T1 WI, T2 WI, DWI, p CASL and ASE EPI scanning. The CBF and OEF images were derived from the original image of ASL and ASE EPI sequence in the Functool software of ADW 4.5 workstation. The aimed images were selected from the level of maximum size of infracted lesion in the ASE EPI sequence, we select the background image to draw up ROI by “+” shape to achieve the CBF and OEF.The size of ROIs were variable among different individuals(range 30–50mm2). ROI1 was the infarct center, ROIs2-4 were from the other 4 directions(a, b, c, d) separately, the total of 10. However, the lesions in five patients were close to the lateral ventricle, we took ROI1 as infarct center, each of 3 ROIs from three directions(b, c, d)separately, the total of 10. And the ROIs of normal brain were selected at the mirror region relative to the ROIs of ischemic regions. The relative ratios between the infarct lesions and contralateral normal brain were calculated,including relative cerebral blood flow(r CBF) and relative oxygen extraction fraction(r OEF). we averaged the values of the all series of ROI to observe the region of 0.3 < r CBF < 0.4, r OEF > 1.4.(according to the literature, r OEF > 1.4and0.3 < r CBF < 0.4 regions suggested the presence of IP).Results: The study found that the CBF of bilateral thalamus had strongly positive correlation with age. The OEF of local normal brain tissue were negatively correlated with age, including the bilateral head of caudate nucleus, bilateral posterior cingulated, the white matter region around the lateral ventricle and bilateral centrum semiovale. In OEF measurements, we found that 1 of 13 cases patients with acute cerebral infarction(08) could be observed r OEF > 1.4 in ROI1, 6 cases(01, 02, 03, 07, 10, 11) could be observed r OEF > 1.4 in ROI2, 7 cases(01, 03, 06, 08, 10, 11, 12) could be observed r OEF > 1.4 in ROI3, 1 case(06) could be observed r OEF > 1.4 in ROI4. 4 patients(04, 05, 09, 13) could not be observed r OEF > 1.4 in all ROIs. In CBF measurements, we found that 13 cases of acute cerebral infarction could not be observed 0.3 < r CBF < 0.4 in all ROIs.Conclusion: 1. The CBF and OEF of local brain tissue has the trend of changing with age in the different brain regions; 2. In acute cerebral infarction patients,we could find that OEF increased around the core of lesion, suggesting that there may exist ischemic penumbra. |
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