Development of 1H NMR in vitro and in vivo spectral editing techniques

• Main Author: Hardy, David Leonard
• Published: University of Leicester 1998
• Subjects: 541
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.696457

The research which is contained in this thesis is in the area of the development of 1H spectral editing techniques for use in vitro and in vivo. The in vivo 1H NMR spectrum potentially contains a wealth of biological data. Information on the metabolic and physiological status of the "sample" can potentially be obtained non-invasively. However, due to the inhomogeneous environment encountered in vivo, most 1H NMR signals are indistinguishable, with only a few metabolites being observed. A number of techniques have previously been developed to try to edit the in vivo 1H spectrum, but with limited success. In this thesis new 1H editing sequences are developed by using a number of simple spectral editing techniques. Several spectral editing sequences have been developed around individual metabolites such as ethanolamine and taurine. In these cases the initial design of the editing sequence was the double-quantum filter. In each sequence, the selectivity of the experiment was increased by the introduction of chemical shift selective pulses. Two more general editing sequences which can edit for a number of metabolites have also been developed. The first sequence is called SELECTER and can be used to edit for the metabolites aspartate, myo-inositol and GABA. This editing sequence is based around the principle of magnetisation transfer. In the case of aspartate and myo-inositol, SELECTER gives greater edited signal intensity, than for other spectral editing techniques. The other more general spectral editing sequence edits for singlet resonances, namely N-acetyl-aspartate, choline and creatine in the in vivo 1H NMR spectrum. Although these metabolites are clearly visible, underlying metabolite resonances distort their measurement. Previous attempts to remove these unwanted resonances introduced errors such as transverse relaxation attenuation. The sequence developed removes underlying metabolite resonances from around singlets in a shorter time where transverse relaxation losses are much lower, thus minimising any errors.