Document Type

Thesis

Date of Degree

Summer 2015

Degree Name

MS (Master of Science)

Degree In

Biomedical Engineering

First Advisor

Vincent A. Magnotta

Abstract

Spin-lattice relaxation in the rotating frame (T1ρ) is a relaxation parameter measured in nuclear magnetic resonance studies. This parameter has been found to be sensitive to chemical exchange processes occurring in diseased tissue associated with abnormal metabolism when measured in magnetic resonance imaging (MRI). Metabolic changes in tissue affected by abnormal metabolism can be quantified with good spatial and temporal resolution using T1ρ, better than a similar method of assessment known as CEST and current methods such as spectroscopic (1H- and 31P-MRS) and nuclear medicine (PET) methods used in clinical settings. Though T1ρ has these advantages, there is no consensus as to which metabolic changes T1ρ is most sensitive. The metabolic changes may be pH related, or due to changes in concentration of metabolites like glucose and glycogen. This work is tries to identify which metabolite evokes the greatest change in T1ρ by studying the response of three spin relaxation measures (T1ρ, T2 and T1) at different temperatures. It was found that T1ρ is more sensitive to pH changes than glucose and lysine at 3T. Also at body temperature, the pH results showed an exponential decay trend for T1ρ signifying the limited range of sensitivity in the pH range of 6.9 to 7.5. The T2 results can be used to explain this trend.

Public Abstract

Diseases such as Huntington’s disorder, Bipolar disorder I, cancer and epilepsy have a common factor of abnormal metabolism linking them. The abnormal metabolism can alter the molecular composition of functioning tissue and cause the tissue to no longer function as it would. Clinical assessment of such diseases is usually done either with proton or phosphorus spectroscopy as well as positron emission tomography (PET). Each of these assessment tools has their advantages but their disadvantages need to be overcome to gain better image quality and minimize possible adverse effects. Recent imaging tools developed assess the abnormal metabolism by measuring certain quantities in the interaction of protons in aqueous environments. One of these tools is T1ρ and it provides some advantages over currently used imaging tools. There are questions as to what T1ρ is measuring in biological tissue and my work tries to address those questions. It was found that T1ρ is more sensitive to pH changes than glucose and lysine at 3T. Also at body temperature, the pH results showed a non-linear trend for T1ρ signifying the limited range of sensitivity in the pH range of 6.9 to 7.5. The T2 results can be used to explain this trend.

Keywords

publicabstract, glucose, lysine, pH, T1rho

Pages

x, 67 pages

Bibliography

Includes bibliographical references (pages 65-67).

Copyright

Copyright 2015 Nana Owusu

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