MRI in Alzheimer's disease: beyond exclusion

Brain imaging has been mainly used to exclude other secondary causes of dementia, the past decade has highlighted a wider potential role of magnetic resonance imaging in the diagnosis and monitoring progression of Alzheimer's disease. Using a cohort of subjects with autosomal dominant Alzheimer's disease, I found that atrophy rate of the hippocampus, a medial temporal lobe structure crucially involved in memory processing, to be increased at least 5.5 years prior to the onset of the clinical diagnosis of Alzheimer's disease. Rates of whole brain atrophy lagged behind by 2 years. I compared focal and global measures of atrophy on magnetic resonance imaging with decline in performance on cognitive and functional scales in the context of a realistic multi-centre clinical trial. In mild-tomoderate stages of Alzheimer's disease, measures of global atrophy (rate of whole brain atrophy and ventricular enlargement) were associated more closely ~ith decline in performance on cognitive and functional scales than was rate of hippocampal atrophy. Measures of medial temporal lobe atrophy conventionally rely either on manual volumetric measurement, which is time consuming, or on a visual rating scale, which is not designed to track disease progression. I describe an automated technique - the Automated Temporal Lobe Atrophy Scale, relying on intensity measurement using volumetric Tl-weighted imaging as a measure of medial temporal atrophy. The method is quick, simple, and may have potential to track disease progression. Few studies have demonstrated the value of novel magnetic resonance imaging techniques that reflect the microstructural pathological changes magnetization transfer imaging a'nd diffusion-weighted imaging.. Here, I demonstrate that certain quantitative parameters of such techniques are altered by the disease process over-and-above atrophy measurements. This suggests that such imaging techniques may provide complementary information to conventional volumetric measurement in detecting the Alzheimer's disease process.EThOS - Electronic Theses Online ServiceGBUnited Kingdo