The Application Of Radionuclide Imaging In Mild Cognitive Impairment

Purpose:Patients with mild cognitive impairment(MCI) are at risk for developing Alzheimer disease(AD).To diagnose AD at an early stage,one must develop highly specific and sensitive tools to identify it among at-risk subjects.The purpose of this study was to evaluate and compare the ability of FDG-PET,SPECT,and structural MR imaging to predict conversion to AD in patients with MCI.Materials and Methods:Relevant studies were identified with MEDLINE from January 1990 to April 2008.Meta-analysis and meta-regression were done on the diagnostic performance data for each technique from eligible studies.We estimated and compared the weighted summary sensitivities,specificities,likelihood ratios(LRs), and summary receiver operating characteristic curves of each imaging technique.Results:Twenty-four eligible studies were included,with a total of 1112 patients. FDG-PET performed statistically better in LR+ and OR,whereas no statistical difference was found in pooled sensitivity,specificity,and LR- for each technique. No statistical difference was confirmed between SPECT and MR imaging.The Q* index estimates for FDG-PET,SPECT,and structural MR imaging were respectively 0.86,0.75,and 0.76.In meta-regression,statistical significance was found only between technique and log OR,with a regression coefficient of-0.575.Conclusion: This meta-analysis showed that FDG-PET performs slightly better than SPECT and structural MR imaging in the prediction of conversion to AD in patients with MCI; parallel performance was found between SPECT and MR imaging. Purpose:Mild cognitive impairment(MCI) represents a transitional phase between normal aging and Alzheimer's disease(AD).The amnestic subtype(aMCI) is the most predictive of progression to AD.The aim of this activation likelihood estimation (ALE) meta-analysis was to quantitatively analyze functional neuroimaging(PET, SPECT and fMRI) studies that estimated brain functional alteration of aMCI at rest condition and during episodic memory performance.Materials and Methods: Nineteen relevant articles from January 1998 to May 2008 were identified.Three main meta-analyses were conducted by comparing aMCI with normal control(NL) at the rest state,aMCI with NL during episodic memory performance,and aMCI alone during episodic memory performance versus the rest state.For each cluster,locations of voxels with peak probabilities were generated.ALE maps were masked and overlaid onto anatomical template using MRIcroN software.Results:The results largely conformed to previous studies and further confirmed the role of hippocampus, precuneus and posterior cingulate cortex(PCC) in aMCI patients at rest,as well as that of the frontal lobe and medial temporal lobe(MTL) structures in episodic memory.Aside from the same areas in the left cerebrum which were activated in aMCI both during encoding and retrieval,increased activation was found in the right medial frontal gyrus during retrieval task.Conclusion:These ALE findings provided the average location and extent of functionally impaired brain region of aMCI patients and generated regions of interest for the testing of new hypotheses.Purpose:To investigate the characteristics of cerebral blood perfusion in the patients with mild cognitive impairment(MCI) by comparing to normal controls and to evaluate the potential roles of SPECT in identifying subjects with MCI from normal aging.Materials and Mehtods:Tewnty patients,who were diagnosed as having MCI, and 20 normal aging subjects each underwent a ⁹⁹Tc^m-ECD SPECT cerebral blood perfusion imaging.We processed SPECT images with SPM5b software and performed a voxel-based statistical analysis comparing MCI patients and normal aging subjects.Results:In comparison with normal controls,subjects with MCI showed asymmetry hypoperfusion in the posterior cingulate gyrus,inferior and superior parietal lobule,cingulate gyrus,inferior and superior frontal gyrus.Conclusion:The results were consistent with previous research,which further confirmed the specific regions with decreased blood perfusion in patients with MCI.