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Title:Quantitative lactate-specific magnetic resonance imaging and proton spectroscopy of muscle and brain
Author(s):Kmiecik, Joseph Anthony
Doctoral Committee Chair(s):Dawson, M. Joan
Department / Program:Biophysics and Computational Biology
Discipline:Biophysics and Computational Biology
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Biology, Animal Physiology
Health Sciences, Radiology
Biophysics, Medical
Abstract:The techniques of magnetic resonance (MR) imaging and spectroscopy have recently garnered much attention as tools for detecting and localizing metabolic changes in living tissues in various pathologic states and during physiologic activation. For example, in studies employing localized MR spectroscopy (MRS) or spectroscopic imaging (MRSI), increases in lactate levels above those in normal, resting tissues have been shown to be associated with disease states such as stroke and tumors, as well as with activated states such as muscular exercise and neural activity. Using different principles, the technique of functional MRI (fMRI) can reveal, in studies of normal brain, neural activation based upon differences, between resting and activated states, of local blood flow, blood volume, and deoxyhemoglobin concentration, which change the apparent NMR relaxation times T$\sb1$ and T$\sb2$ of water around the area of activation.
These now-standard MR techniques, however, have limitations. For example, although its sensitivity allows rapid acquisition, fMRI reports changes in secondary characteristics which may be removed, in an unknown way, spatially and temporally from the precise area and time of activation. Localized spectroscopy conveys more specific biochemical information about the status of the activated tissues, but is limited, because of low sensitivity, to large single volumes of interest or coarse and imprecise multiple volumes in the case of spectroscopic imaging.
Presented in this thesis is the design of a protocol capable of producing, at high resolution and with acceptably short acquisition time, images reporting lactate distribution and concentration in living tissues. Included is the adaptation of a zero-quantum coherence/double-quantum coherence-based lactate-editing pulse sequence which eliminates the signals of other metabolites as well as those of water and lipid, allowing three-dimensional full-sensitivity lactate imaging with a significant reduction of acquisition time. Also, capable analytic algorithms, namely spectral localization by imaging (SLIM) and generalized SLIM (GSLIM), are used to quantitate localized concentrations of lactate and to produce high-resolution maps of lactate distribution with few spatial encodings.
The optimization of the sequence and verification of accurate acquisition and analysis on phantoms, using two MR imaging systems, is discussed. The application of the technique to the imaging of the lactate distribution in stimulated frog skeletal muscle at macroscopic and microscopic resolutions, and in gerbil brain in which unilateral stroke is induced, is presented. A description of the limitations and further possibilities for applying the technique, such as the feasibility of quantitative lactate imaging in human brain during photic stimulation, is included.
Issue Date:1996
Rights Information:Copyright 1996 Kmiecik, Joseph Anthony
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9712334
OCLC Identifier:(UMI)AAI9712334

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