The elderly population (those aged 65 years or older) in Hong Kong is expected to increase from approximately 13% in 2009 to 28% by 2039. With this rapid growth of elders, it raises attention to prevent and treat chronic diseases of aging. Dementia is particularly concerned because the short term memory loss and other cognitive malfunctions lead to a loss of independent function that has a extensive impact on individuals, families, health and social welfare systems. Currently over 70,000 people endure dementia in Hong Kong and expect quadruple rises by 2036. In order to cope with these diseases, accurate diagnosis is very useful, particular at early stage when treatment outcomes are most effective. Numerous studies have found that AD and other dementias could alter brain metabolism significantly. AD patients usually present the posterior cingulated and parietotemporal cortices hypometabolism and spread into the frontal lobes in advanced disease. In contrast, FTD patients show manifestly hypometabolism in the frontal and anterior temporal cortices, while DLB patients present hypometabolism in the posterior brain comprising primarily the parietoocipital regions. Theoretically, 18F-FDG PET scan can help in the early diagnosis of AD and other dementias by highlighting these decreased FDG uptake cortex regions before MRI or CT scans can detect any structural damage. This is a retrospective chart review study. Patients who had received FDG brain PET-CT scan previously had their regional brain metabolism quantitated using a software call Cortex-ID and clinical laboratory tests. The study is * To develop a Neural Network (NN) that can diagnose the various types of dementia using Brain PET-CT scan, testing accuracy of NN versus an expert and, * To see if the NN can correlate with the clinical severity of the disease as reflected by MMSE score. Finally, three neural networks have been designed and they all fulfill all the required specifications. / published_or_final_version / Diagnostic Radiology / Master / Master of Medical Sciences

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published_or_final_version / Medicine / Master / Doctor of Medicine

published_or_final_version / Medicine / Master / Doctor of Medicine

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

The Nazca-South America convergent margin is marked by the presence of the Andean mountain belt, which stretches along the 8000-km long western margin of the South American plate. The subduction zone is characterized by significant along-strike changes in both upper plate structure and slab geometry that make it an ideal region to study the relationship between the subducting slab, the surrounding mantle, and the overriding plate. This dissertation summarizes the results of three finite frequency teleseismic tomography studies of the central Nazca-South America subduction zone which improve our understanding of how along-strike variations in the Andean mountain belt and the subducting Nazca plate interact with each other and with the surrounding mantle. This is accomplished by first focusing on two smaller adjacent regions of the central Andes to explore upper mantle variations and then by using a combined dataset, which covers a larger region, to image the deeply subducted Nazca slab to investigate the fate of the slab. The first study focuses on the central Andean upper mantle under the Altiplano-Puna Plateau where normally dipping subduction of the Nazca plate is occurring (18° to 28°S). The shallow mantle under the Eastern Cordillera is generally fast, consistent with either underthrusting of the Brazilian cratonic lithosphere from the east or a localized "curtain" of delaminating material. Additional evidence for delamination is seen in the form of high amplitude low velocities under the Puna Plateau, consistent with proposed asthenospheric influx following lithospheric removal. In the second study, we explore the transition between normal and flat subduction along the north edge of the Altiplano Plateau (8° to 21°S). We find that the Peruvian flat slab extends further inland along the projection of the Nazca Ridge than was previously proposed and that when re-steepening of the slab occurs, the slab dips very steeply (~70°) down through the mantle transition zone (MTZ). We also tentatively propose a ridge parallel tear along the north edge of the Nazca Ridge. Both of these observations imply that the presence of the Nazca Ridge is at least locally influencing the geometry of the flat slab. The final study investigates along-strike variations in the deeply subducted Nazca slab along much of the central Nazca-South America subduction zone (6° to 32°S). Our results confirm that the Nazca slab continues subducting into the lower mantle rather than remaining stagnant in the MTZ. Thickening of the slab in the MTZ north of 16°S is interpreted as folding or buckling of the slab in response to the decreased slab sinking velocities in the lower mantle.