High-resolution Brain Imaging with Spirals
In this talk, I will give an overview on our journey using spiral k-space trajectories for high resolution brain imaging in the context of structural and functional MRI. I will highlight which recent advancements in MR system characterization and reconstruction have led to "next generation" image quality compared to the classical stereotype of "blurry, low resolution" spirals. I will introduce the major correction techniques for trajectory imperfections (field monitoring, gradient impulse response function (GIRFs)) and static B0 off-resonance that have traditionally limited spiral imaging performance, and show how they can be combined with the general parallel imaging reconstruction framework provided by conjugate gradient (cg)-SENSE. Finally, I will touch upon our latest ventures into spiral diffusion imaging on a clinical MR system. Here, we aim at setting up an open source system characterization and image reconstruction pipeline in the modern programming language Julia, that might allow to deploy spiral imaging to a larger user community.
Discussion points of the webinar:
- Kasper, L., Engel, M., Barmet, C., Haeberlin, M., Wilm, B.J., Dietrich, B.E., Schmid, T., Gross, S., Brunner, D.O., Stephan, K.E., Pruessmann, K.P., 2018. Rapid anatomical brain imaging using spiral acquisition and an expanded signal model. NeuroImage 168, 88–100. https://doi.org/10.1016/j.neuroimage.2017.07.062
- Kasper, L., Engel, M., Heinzle, J., Mueller-Schrader, M., Graedel, N.N., Reber, J., Schmid, T., Barmet, C., Wilm, B.J., Stephan, K.E., Pruessmann, K.P., 2022. Advances in spiral fMRI: A high-resolution study with single-shot acquisition. NeuroImage 246, 118738. https://doi.org/10.1016/j.neuroimage.2021.118738
- Engel, M., Kasper, L., Barmet, C., Schmid, T., Vionnet, L., Wilm, B., Pruessmann, K.P., 2018. Single-shot spiral imaging at 7 T. Magnetic Resonance in Medicine 80, 1836–1846. https://doi.org/10.1002/mrm.27176
- Graedel, N.N., Kasper, L., Engel, M., Nussbaum, J., Wilm, B.J., Pruessmann, K.P., Vannesjo, S.J., 2021. Feasibility of spiral fMRI based on an LTI gradient model. NeuroImage 245, 118674. https://doi.org/10.1016/j.neuroimage.2021.118674
- Wilm, B.J., Barmet, C., Pavan, M., Pruessmann, K.P., 2011. Higher order reconstruction for MRI in the presence of spatiotemporal field perturbations. Magnetic Resonance in Medicine 65, 1690–1701. https://doi.org/10.1002/mrm.22767
Lars Kasper, PhD, Scientific Associate
BRAIN-TO lab (“Brain Research in Advanced Imaging and Neuromodeling – Toronto”)
Lars received his PhD in Biomedical Engineering from ETH Zurich in 2014, with a work on "Noise Reduction in fMRI Utilizing Concurrent Magnetic Field Monitoring". During his postdoctoral research in the MR Methods and Technology Group (Klaas Pruessmann) and Translational Neuromodeling Unit (Klaas Stephan) in Zurich, Lars was working at the interface between cutting-edge imaging concepts and their applications in computational neuroscience and psychiatry. In particular, Lars' projects included ultra-high field spiral MRI and NMR-probe based field monitoring in the context of fMRI, as well as laminar fMRI applications to investigate prediction error signaling according to the Bayesian Brain hypothesis. Since 2020, Lars is a scientific associate in Kamil Uludag's lab for Brain Research in Advanced Imaging and Neuromodeling - Toronto (BRAIN-TO), focusing on the translation of promising MR sequence and reconstruction concepts into the clinics, e.g., for spiral diffusion MRI. Lars' core interest is improving image and time series quality in MRI through understanding both numerator and denominator of the signal-to-noise ratio, i.e., optimizing sampling in MRI, as well as characterizing and correcting for the various physiological and system-induced noise sources. Lars is a fervent supporter of open and accessible neuroscience, and contributes through clean code in the form of usable toolboxes (PhysIO for physiological noise correction in fMRI, UniQC for unified image quality control in MR development), as well as the family committee of the ISMRM.