MRI of the human brain
MRI of the human brain
Prof. Dr. Daniel Topgaard
Department of Chemistry, Lund University
Wednesday, 18 October 2023, 16:00
Diffusion MRI is used in clinical routine for detecting stroke and grading prostate tumors, as well as in clinical research studies of neurological diseases and normal brain development. The overwhelming majority of diffusion MRI studies are performed with motion encoding by the most basic form of the pulsed-gradient spin echo sequence from the mid-60s, which is sensitive to local diffusivities, restrictions, anisotropy, flow, and exchange. While it may be convenient to have a single experiment to detect a wide range of different diffusion properties, the lack of selectivity becomes a nuisance when attempting to assign the experimental observations for a complex, heterogeneous, and anisotropic material like the living brain to a specific diffusion mechanism. In particular, fiber-tracking based on “off-the-shelf” diffusion MRI methods faces problems in heterogeneous white matter regions containing not only myelinated axons but also unknown amounts of gray matter, cerebrospinal fluid, or tumor tissue.
This lecture will give an overview of our recent work in redesigning diffusion MRI using principles that are well known in multidimensional solid-state NMR spectroscopy and low-field NMR of porous materials. The key features of this new “massively multidimensional diffusion-relaxation correlation MRI” approach are gradient waveforms targeting specific motion mechanisms and multidimensional acquisition and analysis protocols wherein the different mechanisms are separated and correlated. Monte Carlo data inversion yields ensembles of nonparametric relaxation-diffusion tensor distributions in which the fiber signals are cleanly resolved from other tissue components. Additionally, values of relaxation rates and diffusivities are estimated for each distinct fiber bundle, potentially giving tract-specific information on chemical composition and microstructure. Clinical application examples include studies of microstructure in brain tumors as well as white matter degeneration in schizophrenia and multiple sclerosis.
The lecture will be held in sitem-insel (Room O2.211), Freiburgstr. 3, Bern