DTI Study Of Alzheimer Disease And Mild Cognitive Impairment Patients

Alzheimer's disease (AD) is one the most common causes of dementia. It (AD) was a neurodegenerative disorder characterized by progressive dementia occurring in elder or pre-elder stage, and influenced the living quality of elders seriously. In the early stage of AD, the patient's short memory was worsen, then gradually decreased of long memory, reasoning, judging, counting and directional abilities. Patholo gi -cally,AD was characterized by the appearance of extracellular senile(amyloid) plaques, intracellular neurofibrillary tangles and nerve cells death or lost. The pathological changes originate in the medial temporal region, in the entorhinal cortex and hippocampus, subsequently spreading over the entire limbic cortex and then into neocortical association areas, which results in progressive cognitive decline. Accurate diagnosis of AD was dependent on biopsy or autopsy, diagnosis before death was mainly dependent on clinical examinations and neuropsychological tests, but because of lack of objective biololgical mark, the accuracy of diagnosis was not high, so it's necessary to offer some radiological diagnosis criteria to correctly diagnose. Although the progression of the disease is assessed primarily by neuropsychological tests, a more quantitative biological index for monitoring will be needed in order to develop and establish such new therapies. In the past, MR studies focused on the hippocampi and surrounding structure were morphologic studies, such as MR measurement of volum or transverse relaxation time(T2) of hippocampi and entorhinal cortex. But when there were obvious changes, it indicated that the course of AD was already in late or terminal stage. Otherwise morphologic changes of hippocampi and entorhinal cortex were not characteristic appearances of AD, they can also be seen in other diseases, such as temporal epilepsy, schizophenia. Conventional MRI is useful for excluding other causes of dementia but are rarely helpful in the diagnosis of AD. We applied a relatively new MR techniques Diffusion tensor imaging(DTI) to diagnose AD, mild cognitive impairment(MCI) in this study.Objective To study the WM changes of the appearent diffusion(ADC) and fractional anisotrpy(FA) detected by DTI technique in mild AD and MCI patients compared with normal coginitive(NC) volunteers,to find the radiological changes of the mild AD and MCI patients. And to investigate the relationship between the DTI paremeters in different regions and cognitive status.Methods and Materials DTI were obtained in 24 mild AD patients ,23 MCI patients,and 20 voluteers.And measure the FA values and ADC values of the WM indifferent regions,including the parietal ,temperal, frontal occipital lobes, anterior and posterior parts of corpus callusum and cigulate bundles.Results l.In NC,MCI and mild AD groups, The values of FA between the anterior and posterior parts of corpus callusum had significangly defference (/)<0.05).2.Compared with NC group,the FA,ADC values of the anterior parietal, temperal lobe,hippocampus, posterior parts of cigulate bundles show significantly difference in AD and MCI groups(P<0.05).and FA,ADC values of the posterior cigulate bundles also show significantly difference in AD group(P<0.05).4. FA,ADC valuse of posterior cigulate bundles differed significantly between.AD and MCI groups(.P<0.05).5 The reduction of the WM FA values and increase of ADC values in the anterior parietal ,temperal lobe,hippocampus.and posterior cigulate bundle were correleted with MMSE scores.conclusions l.Involvment of posterior cigulate bundle is the specific appearance in AD patients, which can lead to a diagnosis in the early stage of AD.2.The reduction of the WM FA values and increase of ADC values in the anterior parietal ,temperal lobe.hippocampus.and posterior cigulate bundle were correleted with MMSE scores.3.Compared to controls,the occurrence of regional changes of WM anisotropy in both AD and MCI groups, suggests that these reginonal anisotropy and diffusion changes in normal-appearing white matter of patients with MCI could occur before the onset of overt dementia and may play a role in the progresson towards ADAThe results of our study support the retrogenisis hyposis of AD pathological preocess.