Multinuclear magnetic resonance techniques for the study of brain metabolism in vivo / David B. Clayton.

Format:

Book

Manuscript

Microformat

Thesis/Dissertation

Author/Creator:

Clayton, David B.

Contributor:

Lenkinski, Robert R., advisor.

University of Pennsylvania.

Language:

English

Subjects (All):

Penn dissertations--Biochemistry and molecular biophysics.

Biochemistry and molecular biophysics--Penn dissertations.

Biochemistry and Molecular Biophysics.

Academic Dissertations as Topic.

Medical Subjects:

Biochemistry and Molecular Biophysics.

Academic Dissertations as Topic.

Local Subjects:

Penn dissertations--Biochemistry and molecular biophysics.

Biochemistry and molecular biophysics--Penn dissertations.

Physical Description:

xi, 178 pages : illustrations ; 29 cm

Production:

2000.

Summary:

Magnetic resonance imaging (MRI) and spectroscopy (MRS) have gained wide acceptance as powerful, noninvasive tools for investigating the structure and function of the human brain in vivo. While proton (1H) MRI has become well-established for clinical diagnosis, the majority of conventional techniques acquire signals dominated by the magnetization of nuclei in water molecules. The aim of this dissertation is to develop methods for detecting signals from other nuclear species more closely associated with metabolic processes.

Localized proton MRS and chemical shift imaging (CSI) offer ways of detecting several dilute macromolecules known to play part in cerebral metabolic processes. To acquire and quantitate these signals, it has become common practice to selectively attenuate the much larger solvent signal to reduce the dynamic range prior to digitization. The results presented here demonstrate that spectra without solvent suppression can be acquired and quantitated as accurately as solvent-suppressed spectra offering several advantages: the solvent signal can be used as an internal concentration, frequency, and homogeneity standard; any partial saturation of off-resonance signals resulting from selective irradiation of the solvent is eliminated; and strict homogeneity requirements for successful suppression can be relaxed allowing for CSI acquisitions that do not require spatial preselection.

In vivo single voxel and CSI data acquired at 4 T with long and short echo times (TE) are presented. At short TEs, parasitic signal modulations of the water resonance can hinder accurate estimation of the metabolite signals. Investigations suggest that these sidebands originate from transient oscillations in gradient coils. Methods for their removal are presented.

Sodium (23Na) plays a vital role in cellular homeostasis and electrochemical activity. Detection of its signal is hindered by fast relaxation, low concentration, and small gyromagnetic ratio (compared to protons). This work presents the development of: a tailored 3D gradient echo sequence for acquiring short TE (1.6 ms) images with minimum RF power deposition; a custom-built birdcage coil; and modifications to scanner electronics allowing acquisition of the 45 MHz sodium signal through the 64 MHz transmit/receive channel. Results show that signal-to-noise ratios of 21 can be achieved in white matter with 3 x 3 x 11 mm resolution in a 15 minute scan.

Notes:

Supervisor: Robert R. Lenkinski.

Thesis (Ph.D. in Biochemistry and Molecular Biophysics) -- University of Pennsylvania, 2000.

Includes bibliographical references.

Local Notes:

University Microfilms order no.: 9989578.

OCLC:

187481774