Dr. Jing-Huei Lee, Professor and Graduate Program Director, Biomedical Engineering, University of Cincinnati, USA

Speech Title: Dynamic Spatially Selective Dephasing for Magnetic Resonance Spectroscopy

Abstract: Attributing to the early invention of the slice selection technique, single-voxel magnetic resonance spectroscopy (MRS) is a widely used tool for biomedical research in vivo since the launch of the MR Imaging (MRI). The results of MRS studies often report the ratios of certain chemical compounds in tissues. Because of the nature of the slice selection technique (i.e. the spatial and frequency relationship), the voxel positions of the chemical compounds will not be the same if their chemical shifts are different. Therefore, the reporting data may not be ideal since the ratios are not from the same volume of interest. This error is amplified as chemical shift dispersion increases, which is evident in the ultra-high filed MRSI and ¹³C and ³¹P MRS.

In this work, we present a novel approach using dynamic spatially selective dephasing for single voxel MRS and MRSI. Unlike the tradition slice selection technique, this approach does not require a radiofrequency pulse for spatial selection. Instead, it utilizes a combination of several high-orders (e.g. 3rd and 4th) shim gradient pulses to create a volume of interest (i.e. voxel) such that the signal outside of voxel is dephased due to a large field gradient while that inside is not. Since the volume selection does not require a radiofrequency pulse, therefore all singles come from the same voxel of interest. In this presentation, we will demonstrate results from both simulations and experimental results.

Keywords: MRSI, dynamic shimming, spatially selective dephasing, ¹³C MRS, ³¹P MRS