Ultra-High Field Metabolic Imaging Lab
Shortly after the introduction of anatomical in vivo magnetic resonance imaging (MRI) also first localized in vivo magnetic resonance spectra (MRS) were acquired in the early 1980s and presented the foundation of metabolic MRI. In vivo 1H MRS and spectroscopic imaging (MRSI), non-proton MRS, MRSI and MRI exploiting 31P, 13C, 2H and 23Na nuclei and chemical exchange saturation transfer (CEST) imaging have evolved during the last 30 years in terms of spatial resolution, acquisition speed, artifact suppression, number of detectable metabolites, ions and compounds and quantification accuracy and precision. All metabolic MRI methods have largely profited from the significant increase of magnetic field strength of > 7T that became available for in vivo investigations. Today, metabolic MRI allows for non-invasive and non-ionizing determination of tissue concentrations and metabolic turn-over rates of various metabolites, ions and compounds in animals or humans, are applied for clinical diagnostics and has established as an important tool for physiological research.
1. Metabolic Imaging Methodology
2. Ultra-High Field MRI Methodology
3. Multimodal high-field MRS and MRI for clinical research
1. Metabolic Imaging Methodology
To draw physiologically meaningful conclusions metabolic imaging results need to be spatially and metabolically specific and all confounding factors related to acquisition, reconstruction and quantitative analysis need to be considered and artifact sources controlled to obtain reliable and reproducible results. To that a high localization accuracy and efficiency including coherence pathway selection and motion compensation methods need to be developed for spectroscopic methods. Calibration steps such as flip angle optimization or B0 shimming have to be robust for all metabolic MRI methods. Quantification has to be based on spectral fitting or chemical exchange modelling algorithms exhibiting robust convergence and include comprehensive prior-knowledge and stable reference standards. In addition, acquisition times need to be shortened by different acceleration techniques to enable metabolic imaging with whole organ coverage at high spatial resolutions in clinically applicable scan time. Finally, time resolved metabolic imaging is desirable to measure metabolic flux rates, response to environmental stimuli, exercise and pharmacological intervention.
Current projects of specific interest include
- robust single voxel spectroscopy localization methods
- accelerated MRSI / MRI encoding and reconstruction using artificial intelligence
- motion and frequency correction methods
- 2D J - resolved and J - edited 1H MRS
- spectral fitting
- spectral processing, fitting and quantification software development
- amino acid imaging
- functional 1H MRS
- 31P MRS / MRSI including the assessment of metabolic rates
- measuring metabolic turnover rates using 13C and 2H labelled isotopes
- CEST analysis strategies for high-resolution data from 7T
2. Ultra-high field magnetic resonance imaging methodology
The higher the static magnetic field strength the higher are spectral separation, exchange effects and signal-to-noise ratio, which results in an increased number of detectable metabolites, ions and macromolecules at high spatial and temporal resolution. However, the advantages of high (3T) and ultra-high (7T) field strength come along with substantial technical challenges such as inhomogeneous transmit (B1+) fields due to standing wave effects, an increased impact of microscopic and macroscopic susceptibility differences on static magnetic field (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, respiratory motion induces time dependent B0 field fluctuations which need to be addressed. The aim of our ultra-high field methods development projects is hence to overcome these technical challenges in order to extend the number of quantifiable metabolites and to increase spatial resolution and hence specificity. In general related methodology can be transferred to additional MR imaging modalities.
Current projects of specific interest include
- radiofrequency coil design
- parallel transmit radiofrequency pulse and sequence design
- static magnetic B0 shim technology
- motion and field drift correction methods
3. Multimodal high-field MRS and MRI for clinical research
Newly developed magnetic resonance metabolic imaging methodology may enable a more profound understanding of healthy and pathological physiology. Hence these methods are evaluated with respect to their relevance for clinical diagnostics and combined with structural and functional MRI modalities such as high resolution anatomical imaging, resting-state functional connectivity imaging, perfusion imaging, diffusion weighted imaging or complementary imaging methodology such as PET for clinical studies. Clinical, neuroscientific or physiology studies are typically joint projects with collaborators with clinical, neuroscience or physiology background and/or expertise in a complementary imaging method.
Current and previous clinical studies focus on the following topics:
- Psychiatric Disorders:
- Major Depressive Disorder
- Schizophrenia
- Addiction
- Neurological Disorders:
- Mild cognitive impairment and Alzheimer’s Disease
- Spinal cord injury
- Multiple sclerosis
- Inborn metabolic defects
- Migraine
- Muscle and heart physiology:
- influence of training and nutrition on fatty acid and energy metabolism in skeletal muscle and myocardium
- Tako-Tsubo Cardiomyopathy, Hypertrophic Cardiomyopathy
- Heart Failure with preserved ejection fraction (HFpEF)
- Diabetes & Metabolic Syndrome