The Application Of MRI In Alzheimer's Disease

Part 1 Phase value and R2* value evaluate the changes of iron deposition in patients with Alzheimer's diseasePurpose:The aim of this study was to investigate the change of iron deposition in the brain of AD patients noninvasively and quantitively by using SWI phase value and R2* value, and to assess the correlation of phase value and R2* value with the severity of cognitive impairment in AD patients.Materials and Methods:23 patients with AD,18 age-and sex-matched healthy controls underwent SWI and T2* imaging at Siemens Magnetom Verio 3.0T system. Oblique coronal images perpendicular to the long axis of hippocampus were obtained ranging from bilateral temporal poles to dentate nuclei. The phase values of the bilateral hippocampus (HP), globus pallidus (GP),putamen (PUT), caudate nucleus(CAU), thalamus(TH), substantia nigra(SN),red nucleus(RN), dentate nucleus(DN) and frontal cortex(FC) were evaluated by a software called SPIN.The T2* values of the bilateral HP, GP, PUT, CAU, TH, SN,RN, DN were measured at T2* imaging,and R2* values were obtained from the formula as follows:R2*=1/ T2*×1000.The phase values and R2* values in the two groups were compared using a nonparametric Mann-Whitney U test. A partial Spearman rank correlation coefficient,controlling by the age-related bias was used to assess the correlation between phase values as well as R2* values in each ROI(region of interests) and MMSE scores in AD group.Result:The phase values of bilateral HP,GP,CAU,SN,right FC and left PUT in AD group were significantly higher than that in the control group. The R2* values of bilateral HP,PUT,CAU and right GP in AD group were significantly higher than that in the control group (P<0.05). The phase values of bilateral GP,PUT,left HP,left FC,right CAU and right DN in AD patients were correlated with MMSE scores respectively, and the R2* values of left HP and PUT were negatively correlated with MMSE scores. The phase value and R2* value of the left PUT had the most significant correlation with the MMSE scores in AD patients,the correlation coefficient was 0.526 and-0.521 respectively. The correlation coefficient between the phase value of the left HP and the MMSE score, the R2* value of the left HP and the MMSE score in AD patients was 0.435 and-0.424 respectively.Conclusion:1 Phase value and R2* value are proved to be effective methods to measure regional iron changes in AD patients,and phase value is more sensitive than R2* value in detecting the changes of iron deposition in AD patients.2 Phase value shows a greater correlation coefficient with MMSE score, and the phase value of left PUT has a close correlation with the progression of AD.Part 2 Metabolic changes in patients with Alzheimer's disease assessed by Magnetic Resonance SpectroscopyObjective:To investigate the metabolic changes in patients with Alzheimer's disease (AD) by proton magnetic resonance spectroscopy (1H-MRS).Methods:T1WI-3D scan and three dimensional MPR reconstruction of hippocampus were used to ensure accurate positioning,so as to reduce interference artifacts and improve image quality as well as reliability.1H-MRS was performed in 14 patients with AD and 10 normal controls by PRESS sequence.Regions of interests were drawn in bilateral hippocampus to detect the NAA/Cr, Cho/ Cr,Glx/Cr and mI/Cr ratio. Statistical analysis was performed by using SPSS for Windows(version 17.0).Results:The bilateral NAA/Cr and Glx/Cr ratios in AD patients were significantly declined compared to the ratios in normal controls (P<0.05).The bilateral ml/Cr ratios in AD patients were elevated compared to that in normal controls,but only the ratio on the right side showed a statistical significance (P<0.05).The Cho/Cr ratios in bilateral hippocampus didn't show significant difference between the two groups.Conclusions:1,1H-MRS PRESS sequence can detect changes of NAA/Cr, Cho/ Cr, Glx/Cr and ml/Cr ratios in bilateral hippocampus.2,Bilateral NAA/Cr and Glx/Cr ratios were declined,while bilateral ml/Cr ratios were elevated in AD group.3,T1WI-3D scan and three dimensional reconstruction of hippocampus helps for accurate positioning,so as to reduce interference artifacts and improve image quality as well as reliability.4,Under 3.0T field strength,PRESS sequence can demonstrate an unobstructed Glx signal that is resolved from NAA at 2.0 ppm.