| Objective:To detect the changes of cerebral metabolism and water molecules diffusion state in patients with diabetic retinopathy using the magnetic resonance spectroscopy (MRS) and diffusion weighted imaging (DWI).Methods:(1)29patients with type2diabetes and DR (DR group),30subjects with type2diabetes without DR (DM group), and30age-and gender-matched control individuals (NC group) were implemented MRS and DWI examination using3.0T MR imager. Voxels were placed in the left frontal white matter, left lenticular nucleus, and left optic radiation for the detection of the levels of NAA/Cr, Cho/Cr, MI/Cr, NAA/Cho and apparent diffusion coefficient (ADC). All statistical analysis was performed with SPSS version13.0and compared with One-Way ANOVA and Independent-Samples t test. Pearson or Spearman’s rank correlation was used to calculated the correlation.(2) Fasting plasma glucose (FPG) level was measured via hexokinase method, glycated hemoglobin (HbA1C) was measured by high-performance liquid chromatography method, triglyceride (TG) was measured using glycerol phosphate oxidase method, total cholesterol (TC) was measured by cholesterol oxidase method, high density lipoprotein (HDL) and low density lipoprotein (LDL) were measured by chemically modified enzymatic assay.(3) This study was performed on Germany Siemens3.0T system (MAGNETOM Verio Tim). T1-weighted images were obtained in the axial plane. T2-weighted images were obtained in the axial, sagittal and coronal planes. Participants who had normal cerebral conventional magnetic resonance images were taken the single-voxel MRS examination. Single-voxel MRS was performed in the participants using a point-resolved spectroscopy sequence (PRESS; TR/TE:2000/30ms). Regions of interest (ROI) were placed in the brain left frontal white matter (15x15x15mm3), left lenticular nucleus (15×15×15mm3), and left optic radiation (15x15×15mm3). Receiving/transmitting gain control, uniform field, water suppression were completed by the automatic scanning program beforehand. All data post-processing such as baseline correction and phase correction were performed after receiving the spectra. Metabolites were identified automatically by MRI scanner and the integrals of the various metabolites and relative metabolite ratios such as NAA/Cr, Cho/Cr, MI/Cr and NAA/Cho were calculated. For DWI, a single shot echoplanar pulse sequence (TR/TE=3000/95ms, field of view=24cm×24cm, matrix size=128×128, number of acquisitions=2, slice thickness=6mm, interslice gap=1mm) was used in all patients and controls with two different b values (0and1000s/mm2). The ADC values were measured in all the ROI. The areas of ROI were80mm2.Results:(1) Age, sex, blood lipids, blood pressure have no obvious difference among the three groups. There was no statistically significant difference in fasting plasma glucose (FPG) and HbA1C between DR group and DM group.(2) Frontal white matter:NAA/Cr ratios in the DR group were significant lower than those of the DM and NC group. NAA/Cho ratios in DR group were significant lower when compared with the NC group. MI/Cr, Cho/Cr levels have no significant difference among the three groups. Lenticular nucleus:MI/Cr ratios in the DM group were significant higher as compared to the NC group, while MI/Cr ratios of the DR group were significant lower as compared to the DM group. NAA/Cr, Cho/Cr and NAA/Cho levels have no significant difference among the three groups. Optic radiation:NAA/Cr ratios were also significantly decreased in the DR group as compared to the NC group. MI/Cr, Cho/Cr and NAA/Cho levels have no significant difference among the three groups.(3) Frontal white matter:ADC values in the DR group were significantly higher than those in the DM group and NC group. Lenticular nucleus:ADC values in the DR group were significantly higher than those in the NC group. Optic radiation:ADC values in the DR group were significantly higher than those in the DM group and NC group.(4) No significant correlation was observed in the DM and DR group between cerebral parameters such as NAA/Cr, Cho/Cr, MI/Cr and NAA/Cho, ADC values and clinical characteristics including FPG and HbA1C. In the frontal white matter, NAA/Cr values were negatively correlated with ADC values in the DR group (r=-0.566,p=0.001). In the optic radiation, NAA/Cr values were negatively correlated with ADC values in the DR group (r=-0.656, p=0.000). A negative correlation of NAA/Cr ratios with DR severity (rs=-0.511;p=0.005) were found in the frontal white matter. In the meantime, NAA/Cr ratios were negative correlated with DR severity (rs=-0.474; p=0.009) in the optic radiation.Conclusion:Patients with diabetic retinopathy were accompanied with early brain tissue damage, though they showed normal appearance in the conventional magnetic resonance imaging. MRS and DWI can detect early brain tissue changes in patients with diabetic retinopathy. |
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