Susceptibility Mapping and Phase Contrast Imaging
Group headed by Dr. Sina Straub
The group works in the field of quantitative susceptibility mapping (QSM) including phase processing algorithms and the investigation of underlying mechanisms in phase contrast.
Quantitative susceptibility mapping [1,2] can be thought of as an extension of susceptibility weighted imaging (SWI) and is a rather new technique in magnetic resonance imaging (MRI). Both techniques, QSM and SWI, use MR phase data, whereas for QSM, its processing is a much more delicate process, since QSM is a quantitative technique and inverse problem solving is needed.
Various algorithms are used to process and invert phase data to compute susceptibility maps.
QSM is especially well-suited for applications in neuro-degenerative (Parkinson’s, Alzheimer’s, etc.) and neuro-inflammatory (multiple sclerosis) diseases where iron accumulation (Fig. 1a) or iron-depletion seem to be involved in the pathological process. Moreover, changes in blood oxygenation can be observed using QSM as well as hemorrhagic events (Fig. 2). Susceptibility contrast is dependent on orientation and tissue microstructure which poses challenges to the calculation of susceptibility maps, but may also provide useful information in pathological transformations of tissue.
In the brain, it is possible to obtain susceptibility maps of high quality. However, achieving the same quality in the abdomen is hampered by the presence of fat and often extensive motion by respiration or intestinal movement. We have successfully used QSM to detect prostatic calcifications (Fig. 3) [3] and are currently working on liver QSM. In the liver, QSM has recently been shown to be a quite promising technique for iron quantification [4].
There are various open research questions concerning all aspects of QSM in data acquisition, data processing and promising fields of application.
References
- Haacke ME, Liu S, Buch S, et al. Quantitative susceptibility mapping: current status and future directions. MRM 2015, 33:1–25.
- Yi W, Liu T. Quantitative Susceptibility Mapping (QSM): Decoding MRI Data for a Tissue Magnetic Biomarker. MRM 2015, 73:82-101.
- Straub S, Laun FB, Emmerich J, et al. Potential of quantitative susceptibility mapping for detection of prostatic calcifications. JMRI 2016, 10.1002/jmri.25385
- Sharma SD, Fischer R, Schoennagel BP, et al. MRI-Based Quantitative Susceptibility Mapping (QSM) and R2* Mapping of Liver Iron Overload: Comparison With
Research Topics and Projects
- Phase processing for QSM
- Inverse-problem solving/ dipole inversion
- Alternative acquisition (non-Fourier, non-Cartesian, …) and reconstruction schemes
- Evaluation: phantoms and software phantoms
- Application of QSM in the brain (metastases (Fig. 1c, 2)), white matter properties, iron accumulation in healthy brain and disease (Fig. 1a), intracranial hemorrhage (Fig. 1b), arteriovenous malformations (Fig. 4))
- Application of QSM in the body (prostatic calcifications (Fig. 3), liver)
