Designs of novel RF coils for signal-to-noise ratio improvement in NMR

In this thesis, two different novel RF coils were designed to improve the available signal-to-noise ratio (SNR) in nuclear magnetic resonance (NMR) spectroscopy and imaging. One of them was an inductively coupled {dollar}sp{lcub}31{rcub}{dollar}P implanted coil. The other was an inductively coupled quadrature {dollar}sp1{dollar}H implanted coil.; The {dollar}sp{lcub}31{rcub}{dollar}P implanted coil was inductively coupled to an excitation/reception external coil and placed directly above the spinal cord of a rat to restrict the field of view (FOV) to the region of interest (ROI). The {dollar}sp{lcub}31{rcub}{dollar}P implanted coil had a resonant blocking circuit to decouple this coil from the external coil during transmission so that excitation was uniform in the ROI. A quadrature {dollar}sp1{dollar}H surface coil was mounted over the {dollar}sp{lcub}31{rcub}{dollar}P external coil for the acquisition of NMR images and shimming. Good quality {dollar}sp{lcub}31{rcub}{dollar}P spectra from ROI were obtained with the {dollar}sp{lcub}31{rcub}{dollar}P coil implanted over a rat's spinal cord. Therefore the {dollar}sp{lcub}31{rcub}{dollar}P implanted coil could be used to study changes in metabolites of a rat's spinal cord after injury and repair.; The first quadrature implanted coil, which was receive-only and inductively coupled to an excitation/reception external quadrature coil, was designed. The SNR of this implanted coil was measured on a cat phantom and compared with that of an optimized linear surface coil, a quadrature surface coil or an inductively coupled linear implanted coil. In the ROI (i.e., a cat spinal cord), the quadrature implanted coil exhibited a factor of 7.04 increase in SNR relative to the linear surface coil; a factor of 4.48 relative to the quadrature surface coil and a factor of 2.59 relative to the linear implanted coil. The improved SNR for an inductively coupled quadrature implanted coil was observed as a dramatic improvement in the clarity of the images of an excised rat spinal cord. The high SNR available with the inductively coupled quadrature implanted coil allows the acquisition of high resolution NMR images and opens up the possibility of measuring localized spectroscopy in vivo within the spinal cord.