Jongho Lee1
1Seoul National University, Seoul, Korea, Republic of
Synopsis
In this presentation, microstructural imaging using susceptibility induced magnitude and phase contrasts will be introduced. The sources of the phase contrast, which include tissue iron and myelin, and the contrast mechanisms will be discussed. Then, a few models and imaging methods such as quantitative susceptibility mapping, susceptibility tensor imaging, hollow cylinder fiber model, and myelin water imaging that explored the contrast mechanisms to extract microstructural information of the brain will be highlighted. Finally, a few emerging susceptiblity imaging methods and clinical applications will be addressed.
Syllabus
This presentation is targetted to provide an overview of microstructural imaging via magnetic susceptibility induced magnitude and phase contrasts. Magnetic susceptibility is an property of material and has been treated as a source for artifacts in MRI. At the same time, it served as a source for imaging contrasts (e.g. paramagnetic nature of deoxyhemoglobin utilized for functional MRI and susceptibility weighted imaging).
Over the last 10+ years, people have explored to the effects of various susceptiblity sources in the brain such as iron and myelin, which are known to be related to important neurological disorders including Alzheimer's and Parkinson's diseases. Based on the contrast mechanism studies, several models and imaging methods, some of which are listed below, have been developed.
In this presentation, I will cover the contrast mechanisms and the following imaging methods and models:
- Quantitative Susceptibility Mapping: Assuming isotropic susceptibility sources, the method perform deconvolution of dipole pattern to generate a susceptibliity map from a phase image.
- Susceptibility Tensor Imaging: Assuming both isotropic and anisotropic susceptibility in whitte matter, the method generate a fiber orientation map of the brain.
- Hollow Cylinder Model: Assuming white matter can be modeled as hollow cyliders with multiple water compartments (e.g., myelin water, axonal water, extracelullar water) of different T2* and include susceptiblity anisotropy, the model demonstrates a compartment specific field change based on the relative orientation of the cylinders to B0
- Myelin Water Imaging: Utilizing the hollow cylinder model, GRE complex data are fitted to a multi-compartment complex model that includes the compartment specific field terms, improving the myelin water fraction map.
After covering these topics, a brief introduction of emerging methods as well as potential limitations will be discussed. Finally, a few important clinical applications will be mentioned to complete the presentation. Acknowledgements
No acknowledgement found.References
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