Brownian motion of water molecules provides an essential length scale, the diffusion length, commensurate with cell dimensions in biological tissues. Measuring the diffusion coefficient and other diffusion metrics (e.g., kurtosis) as a function of diffusion time makes in vivo diffusion MRI uniquely sensitive to the cellular features about three orders of magnitude below imaging resolution. The sensitivity of time-dependent diffusion to micro-geometry of the brain tissue potentially serves as a marker for pathological changes in neurodegenerative diseases.
Chapter 1 introduces the diffusion time-dependence in tissue microstructure and how to measure it with MRI.
Chapter 2 explains the theoretical background of diffusion time-dependence in the brain white matter.
Chapter 3 reconstructs electron microscopy images in the mouse brain, segments individual axons, and quantifies the white matter micro-geometry.
Chapter 4 and Chapter 5 validate the biophysical modeling of the brain white matter via Monte Carlo simulations in realistic tissue microstructure for diffusion transverse to and along axons, respectively.
Chapter 6 demonstrates the time-dependent diffusion MRI measurement in a fiber phantom and the human brain.
Chapter 7 concludes the findings of the thesis and outlines future directions based on this body of work.
|Advisor:||Novikov, Dmitry S., Fieremans, Els|
|School:||New York University|
|Department:||Basic Medical Science|
|School Location:||United States -- New York|
|Source:||DAI-B 81/5(E), Dissertation Abstracts International|
|Subjects:||Medical imaging, Neurosciences|
|Keywords:||Biophysical modeling, Diffusion MRI, Diffusion time dependence, Microstructure, Monte Carlo simulation, White matter|
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