Muscle group specific quantification of unsaturated fatty acids by localized DEPT-enhanced 13C MRS and ERETIC

Introduction 13C MR spectroscopy in vivo enables to obtain metabolic information of humans not easily obtained by other non-invasive methods. The large chemical shift range of 13C MR spectra allows the resolution of resonances from a large number of substances, and thereby the study of some metabolites which are difficult to resolve in 1H MRS. One of them are unsaturated fatty acids, whose concentration is a valid tool to assess the dietary intake. In addition the ratio of polyand monounsaturated fatty acids indicates some physiological diseases like cystic fibrosis [1]. However, the major drawback of 13C MRS applied to humans is its low sensitivity, which is a consequence of the low natural abundance and the low gyromagnetic constant of the carbon nucleus. The attached protons cause multiplet structures which further decreases sensitivity. Under all these restrictions the quantification of metabolite concentrations of spatially specific localized 13C spectra is still questionable. In this work, we propose a combined SNR enhancement by proton decoupling and ISIS-localized DEPT (Distortionless Enhancement of Polarization Transfer), aiming at muscle-group specific detection of unsaturated fatty acid in the calf muscle. SNR-enhancement was performed with a shielded transmit/receive13C/1H dual-tune volume calf coil (RAPID Biomedical GmbH) equipped with ERETIC (Electric REference To access In vivo Concentration) [2]. With the chosen enhancement method in vivo calf muscle spectra from small volumes of interest in specific muscle fibre groups can be acquired and quantified using the ERETIC signal as reference.