Perfusion Changes In Early Alzheimer's Disease With Arterial Spin Labeling On 4T MR

Background and objective:Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive cognitive impairments and is the most common reason for dementia. The histological changes are characterized by senile plaque, neurofibrillary tangles, neuron loss and granulovacuolar degeneration. Brain damage begins in the medial temporal lobe in the early stage of AD and extends gradually to the entire neocortex. Neuroimaging techniques have played an important role in diagnosing AD, especially in finding functional abnormalities in early stage of the disease. The purpose of this study was to detect brain hemodynamic and functional changes in subjects with AD at both resting state and during cognitive tasks.Methods:Twelve subjects with early AD (mean age=72.3±7.9 yrs, females=5) and 12 age-matched cognitively normal (CN, mean age=73.7±5.5yrs, females=9) subjects were recruited for this study. Perfusion-weighted imaging with arterial spin labeling (ASL) was employed to study the hemodynamic abnormalities in AD at resting state. ASL-based fMRI was used to investigate brain functional changes during cognitive states including both encoding and retrieval tasks in AD. Blood oxygenation level dependent (BOLD)-functional MRI (fMRI) was also conducted for comparison. Data post-processing was performed with SPM and FSL software package. SPSS versoin19.0 was used for statistics.Results:During the resting state, brain perfusion was located in AD in the right frontal lobe, left temporal and occipital lobes, and anterior cingulate cortex (ACC). In comparison with the CN group, hypoperfusion occurred in AD in the bilateral prefrontal cortex, left precuneus and posterior cingulate cortex. Hyperperfusion was also found in the bilateral prefrontal cortex (including the dorsolateral prefrontal cortex (DLPFC), ventrolateral prefrontal cortex (VLPFC) and ACC in subjects with AD. During the memory task performance, the AD group showed significantly greater perfusion/activation than the normal controls in bilateral prefrontal cortex (including the DLPFC and VLPFC), as well as the ACC under both encoding and retrieval tasks.Conclus i on:Hypoperfusion occurred in multiple areas in AD at both resting state and under memory tasks, reflecting perfusion damage in early AD. Meanwhile, hyperperfusion/hyperactivation was also found in bilateral prefrontal cortex in subjects with AD in both resting state and under task performance, suggesting the neurocompensatory response in these areas. ASL and BOLD are comparable in detecting brain hemodynamic changes in AD with 4T MR.