Age-Dependent Normal Values Of R2' And T2' In Brain Parenchyma And The Early Clinical Use In Acute Ischemic Stroke On 3.0T MRI

PartⅠ:Age-dependent normal values of R2'and T2'in brain parenchyma on 3.0T MRIObjective In our study, R2, T2, R2*, T2*, R2' and T2'values of brain parenchyma were determined with 3.0T MRI in healthy subjects to determine standard values and to investigate the age-related pattern of them. The differences of two cerebral hemispheres and gender of the above values were also studied.Material and methods Total 59 healthy volunteers ranged 25-76 years of old (mean age 49.73±14.65 years) took part in our study.28 male volunteers with the mean age 50.25±15.07 years and 31 female with the mean age 49.26±14.51 years were studied.59 volunteers were divided into 6 groups according to each group 10 years. Leukoaraiosis was considered a regular aging process and was graded 0-Ⅵcorresponding to semioval center and periventricular high signal intensity on T2WI. The raw date including T2map and T2*map were transferred to ADW4.3 workstation. After calculation of R2, T2, R2*, T2*, R2',T2'maps, the values of deep gray matter (head of caudate nucleus, putamen, globus pallidus, thalamus) and white matter (frontal white matter, occipital white matter and subcortical white matter) were measured in distinct regions of interest (ROI).Results In general, there was a positive correlation between age and R2, R2* and R2'values in deep gray matter. Correspondingly, there was a negative correlation between age and T2, T2* and T2'values in gray matter. In general, there was no correlation between age and R2*,T2*, R2', T2'values except R2 and T2 which was respectively negative and positive correlation with age in white matter. R2 values of left side caudate nucleus and putamen was slightly higher than that of right side (t=11.16～3.659, P=0.000～0.001). T2 values of left frontal and occipital white matter were lower than that of right side (t=11.16～3.659, P=0.000-0.001).There was no statistic differences between male and female in all sequences (P>0.05). T2 and T2* values increased corresponding to the high degree of leukoaraiosis. Contrast to T2 and T2*, there was no association of T2'values with the degree of leukoaraiosis.Conclusion①The increase of T2, T2* and T2'values but decrease of R2, R2* and R2'values correlate with the progress of the brain aging in central gray matter.②In general, the increase of T2 values and decrease of R2 values in white matter correlate with the progress of brain aging. There is no correlation between R2', T2'values and aging.③R2 values of left side is higher than that of right side in both gray matter(head of caudate nucleus, putamen)and white matter(frontal white matter and occipital white matter) but the T2 values is lower.④There is no statistic differences between male and female in R2, T2, R2*, T2*, R2'and T2'sequences.⑤There is no association of T2'values with the degree of leukoaraiosis.PartⅡ:The early clinical use of BOLD imaging in acute ischemic strokeObjective To show the features of R2'and T2'in acute ischemic stroke. Compare them with diffusion weighted imaging (DWI) to estimate the value of them in judging the infarction core and ischemic penumbra (IP)Material and methods 14 patients (male 8 and female 6) with acute ischemic stroke within 24 hours of symptom onset underwent MRI examination. The mean age was 56.36±9.28 years old, with a rang of 44～75 years. The mean time from symptom onset to hospital was 16.73±4.65 hours (6-22 hours). The high signal intensity on DWI in first MRI examination was difined L0. Follow-up were performed on day 7 to 20 days. The final infarct size was defined on T2WI or T2-FLAIR imaging in follow 7-20 days. Lesion growth (LG)from day 1 to day 7-20 was derived by subtracting day 1 from day 7-20, and surviving tissue (ST)was calculated by subtracting day 7-20 from day 1. The MRI sequences include T1WI, T2WI, DWI, T2-FLAIR, T2map, T2*map and 3D-TOF MRA. The total time of examination was 20 minutes. Functool software in ADW4.3 workstation was used to overlap the pictures. The lesion shape were manually drawn in each picture and then compared them eachother.Results Three conditions were defined according to the area of abnormal signal intensity on DWI and R2'in first MRI:①R2'>DWI,4 cases;②R2'=DWI,6 cases; ③R2'DWI, R2'=DWI and R2'