Investigation of RF spiral surface coils for NMR spectroscopy

Although used extensively in magnetic resonance imaging, radio frequency (RF), surface coils have not been applied widely to high-resolution spectroscopy. Inherent sensitivity limitations and potential field distortions primarily have hampered their utility. However, surface coils do offer several benefits that could prove useful in NMR spectroscopy. Easy to construct through the use of photolithography, these coils can be scaled and configured to the samples under investigation, especially cultured cells and other ex vivo biological samples. Surface coils also can be arrayed to improve coverage areas and signal-to-noise ratios (SNR). However, in designing microcoils, optimization of the geometrical parameters by taking the eddy current losses into account has considerable importance and can substantialy improve SNR. Here, the authors develop an semi-analytical model to estimate the losses for the spiral geometry that is valid for wide range of geometrical parameters.