The revolutionary development of neuroimage technology allows for the generation of large-scale neuroimage data in modern medical studies. For example, structural magnetic resonance imaging (sMRI) is widely used in segmenting neurodegenerative regions in the brain and positron-emission tomography (PET) is commonly used by clinicians and researchers to quantify the severity of Alzheimer's disease.
In the first part of this dissertation, we build “OASIS-AD”, which is a supervised learning model based on a well-validated automated segmentation tool “OASIS” in multiple sclerosis (MS). OASIS-AD considers the specific challenges raised by WMH in Alzheimer's Disease (AD) to reduce false discoveries. We show that OASIS-AD performs better than several existing automated white matter hyperintensity segmentation approaches.
In the second part of this dissertation, we develop an interpretable penalized multivariate high-dimensional method for image-on-scalar regression that can be used for association studies between high-dimensional PET images and patients' scalar measures. This method overcomes the lack of interpretability in regularized regression after reduced-rank decomposition through a novel encoder-decoder based penalty to regularize interpretable image characteristics. Empirical properties of the proposed approach are examined and compared to existing methods in simulation studies and in the analysis of PET images from subjects in a study of Alzheimer's Disease.
In the third part of this dissertation, we developed ACU-Net, an efficient convolutional network for medical image segmentation. The proposed deep learning network overcomes the small sample size problem of training a deep neural network when used for medical image segmentation. It also decreases computation cost by increasing the effective degrees of freedom through data augmentation and the novel use of convolutional layers blocks to compress the model. We show that ACU-Net can achieve competitive performance while dramatically decreases the computation cost compared with modern CNNs.
Public health significance: This dissertation proposes new statistical and machine learning methods for two aging-related problems: (1) automatically segmenting white matter hyperintensity (WMH), a biomarker of neurodegenerative pathology, and (2) estimating the association between neurodegeneration pathology and vascular measures, which are important to aging population living quality and can be studied by clinical neuroimage data
