In vivo intermolecular zero-quantum coherence MR spectroscopy in the rat spinal cord at 17.6 T: a feasibility study

Objective: The feasibility of in vivo magnetic resonance spectroscopy of the healthy rat spinal cord at 17.6T using conventional methods and intermolecular zero-quantum coherence (iZQC) spectroscopy is explored and the performance of both approaches is compared. Methods: Localised spectra were acquired at 17.6T from three healthy Fisher rats and phantoms with injected ironoxide particles using the PRESS and a modified HOMOGENIZED sequence. Results: Well-resolved in vivo spectra showing the four singlet resonances of creatine, choline, and N-acetyl aspartate were obtained with both approaches. iZQC spectra were acquired from larger voxels, but did not provide higher sensitivity or resolution in the healthy spinal cord. In the presence of paramagnetic iron-oxide particles, the quality of in vitro spectra acquired with PRESS declined and was strongly dependent on the quality of the local shim. iZQC spectra were not affected by the presence of ironoxide particles and provided narrow lines (9 Hz) independent of the shim. Conclusion: In vivo iZQC spectroscopy of the rat spinal cord is possible. The robustness in presence of local field distortions makes iZQC methods a promising alternative for the investigation of tissue containing labelled cells, implants, or clotted blood. New application of MRS to tissue inaccessible using conventional methods may thus become possible.