Magnetic resonance imaging (MRI) is generally regarded as a macroscale imaging technique and often used to visualize anatomical details within whole organs such as the brain. However, quantitative MRI (qMRI) can be used to probe physical, chemical and physiologic features within each volume element or “voxel” of the image. Diffusion MRI (dMRI) is one such qMRI technique in which the MRI signal can be sensitized to the microscale displacement of water molecules in order to probe the structural features (e.g. shapes and sizes) of cells and tissues. Over many decades, a host of frameworks have been developed to quantify microstructure using this paradigm. We will discuss several of the most prominent dMRI frameworks for mapping brain microstructure including diffusion tensor imaging (DTI), mean apparent propagator MRI (MAP-MRI) and diffusion tractography. The use of physical and biophysical modeling will be considered along with the assumptions and equations that relate the MRI signal with water displacement and biological features. Finally, examples of how these methods are applied toward discovery of new markers of Alzheimer’s Disease pathology will be presented.

Reference textbook (optional) via UA library

https://arizona-primo.hosted.exlibrisgroup.com/permalink/f/evot53/01UA_ALMA51557913720003843

Additional techniques not mentioned in the textbook:

MAP-MRI https://pubmed.ncbi.nlm.nih.gov/23587694/

NODDI https://pubmed.ncbi.nlm.nih.gov/22484410/