Methodological Projects
In vivo MR spectroscopy is limited by an insufficient signal-to-noise ratio and spectral resolution which results in a small number of detectable metabolites and a low spatial specificity if the standard clinical field strength of 1.5T is applied. The higher the field strength the higher are spectral separation and signal-to-noise ratio, which gives a completely new perspective for the future of in vivo MRS in physiological research and clinical diagnostics. However, the advantages of high (3T) and ultra-high (7T) field strength for human MR scanners come along with extensive technical challenges such as inhomogeneous B1 fields due to standing wave effects, an increased impact of microscopic and macroscopic susceptibility differences on B0 inhomogeneity, shortened T2 and lengthened T1 relaxation times, lower effective B1 field strength and scan time prolongation due to specific-absorption-rate restrictions. In addition flow, motion and time dependent B0 fields limit the application of in vivo MRS to very few organs.
The aim of our method development projects is to overcome technical challenges related to high and ultra-high field MRS in humans in order to extend the number of quantifiable metabolites and to increase spatial resolution and hence specificity. All confounding factors need to be considered and artifact sources controlled in order to achieve quantitative results. In order to suppress artifacts, techniques that compensate for flow, motion or time dependent Bo fields need to be developed along with coherence pathway selection methods and advanced hardware concepts. Preparation steps such as power optimization or shimming have to be reproducible and quantification has to be based on reliable fitting algorithms and stable reference standards. In addition, acquisition times need to be shortened by different acceleration techniques for clinical use, spectroscopic imaging with whole organ coverage at high spatial resolutions and functional magnetic resonance spectroscopy.
Specific on-going projects are: