Magnetic resonance diffusion imaging and spectral localization: New methods and their quantitative applications
Yang, Yihong
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Permalink
https://hdl.handle.net/2142/20528
Description
Title
Magnetic resonance diffusion imaging and spectral localization: New methods and their quantitative applications
Author(s)
Yang, Yihong
Issue Date
1995
Doctoral Committee Chair(s)
Lauterbur, Paul C.
Department of Study
Biophysics
Discipline
Biophysics
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Biomedical
Biophysics, Medical
Biophysics, General
Language
eng
Abstract
There has been a growing interest, in recent years, in the measurement of diffusion of water and metabolites in living systems by magnetic resonance (MR) techniques. Knowledge of the diffusion coefficients of the molecules can yield unique information about microstructure and function of tissue. We have developed a method for the measurement of anisotropic diffusion by MR projection reconstruction imaging, which is inherently insensitive to motion artifacts and can have higher signal-to-noise ratio compared with conventional Fourier transform imaging. Anisotropic diffusion of water in skeletal and smooth muscle has been investigated using this method. In addition, the water diffusion coefficient in rat uterus has been correlated to the hormonal level, which suggests that diffusion measurements on the human uterus may be useful in detecting endometrial pathology. We have also developed a method for localized diffusion measurement with efficient acquisition in arbitrarily-shaped regions. Experiments on phantoms and biological tissues have been performed using this method.
The SLIM (spectral localization by imaging) technique was developed in this group in collaboration with a group at the University of Chicago. This technique has many advantages over the existing spectral localization techniques for in vivo studies. We have applied this technique to the quantitative analysis of regional phosphorus metabolite levels on human brain. The concentrations of the phosphorus metabolites have been measured in regions of human brain, such as cerebrum, cerebellum plus brain stem, and white and grey matter. In order to investigate the reliability of the SLIM technique in in vivo applications, we have developed a Bloch equation-based simulation method to carry out analyses on the combined effects of unavoidable experimental non-idealities and compartmental heterogeneity. For quantitative analysis in surface coil experiments, we have developed an optimized method for flip angle mapping by multiple echo imaging. The flip angle profile obtained from this method was used for compensation of signal intensity variations caused by the inhomogeneous B$\sb1$ field. Finally, we have developed a method to measure spatially localized 2D correlation spectroscopy (SLIM COSY), which could provide localized in vivo COSY spectra in regions of interest.
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