Clinical application of 1H MRS in the human brain at 7T

Proton magnetic resonance spectroscopy (1H MRS) enables non-invasive biochemical sampling of tissues, potentially aiding diagnosis, prognosis and monitoring of various pathologies, and providing potential novel imaging biomarkers. Ultra-high-field (UHF) imaging at 7 tesla (7T) benefits from improved spectral dispersion, due to an increase in chemical shift differences increasesbetween metabolites, and higher signal-to-noise ratio (SNR) requiring a smaller amount of signal averaging, making 1H MRS at 7T a particularly promising diagnostic tool to identify and separate metabolites not clearly seen resolved at lower field strengths. 1H MRI and MRS at UHF presents technical challenges, however, related to the short RF wavelength at 7T resulting in B1 transmit field inhomogeneity, and the increased magnetic susceptibility gradients resulting in B0 field inhomogeneity. Tailored Appropriate MRS techniques methods are required to address these issues. In this article we describe technical aspects and challenges of 1H MRS at 7T, based on the experience in our centre, where single voxel 1H MRS has featured heavily in clinical 7T research applications for several years. We present data from six glial tumour patients, including in three who were post-operative patients, in whom post-surgical metalware affects specific absorption rate (SAR), along with two patients with neuroinflammatory conditions and two with neurodegenerative diseases. We describe promising clinical applications of MRS at 7T and development of imaging biomarkers. Clinical case examples are discussed with pictorial imaging review and integrated pathological diagnosis. This includes different pre-and post-operative glial tumours; neuroinflammatory, infective and neurodegenerative pathologies, including multiple sclerosis (MS), progressive multifocal leukoencephalopathy (PML), motor neuron disease (MND) and epilepsy. The potential clinical use of 1H MRS for these pathologies, and its possible integration of MRS as a promising imaging biomarker into advanced imaging pathways is discussed.