Design of optimized shimming coils for human brain imaging

Master thesis project

Background

Magnetic resonance imaging (MRI) is a non-invasive medical imaging method used for studying various aspects of the human body. The central and crucial component of an MRI machine is the magnet, responsible for generating a strong and stable static magnetic field, commonly known as B0. Ensuring the uniformity of this magnetic field is essential for many imaging techniques, yet achieving perfect homogeneity in practice remains a challenge. B0 inhomogeneity leads to the presence of artifacts in the resulting images.

Shimming, the process of homogenizing the B0 field, aims to mitigate inhomogeneity by introducing an additional magnetic field with a corresponding pattern of inhomogeneity but opposite polarity. To accomplish this, specialized hardware known as a shim setup is designed and utilized. In the High-Field Magnetic Resonance department at the Max Planck Institute for Biological Cybernetics, we have designed and made prototype of several local shim coils to tackle this issue.

Project Description

The project involves a multi-step approach. Initially, one should gain a basic understanding of MRI theory. Subsequently, the focus will shift towards the application of algorithms in the development of a specialized shim coil tailored for human brain shimming at a 9T MRI scanner. Given that a significant portion of the B0 field perturbation originates from the imaged subject, it is anticipated and observed that B0 inhomogeneity within the human brain follows a consistent pattern. This serves as the primary motivation for designing a shim coil that is anatomically matched with the human brain.
Throughout this work, a range of algorithms and optimization techniques will be employed to generate shim coils that are optimized for their intended purpose. These optimizations will offer flexibility in adjusting various parameters. The effectiveness of these optimization techniques will be evaluated using a dataset of B0 maps acquired at the 9T scanner.
The development and simulation aspects of this project will be implemented using Python and/or MATLAB.

Qualifications: We are looking for highly motivated candidates with a background in engineering, mathematics, physics, life science, or similar. Programming skills in Python and/or MATLAB are desired.

Application: For further information or to apply, please contact Dr. Ali Aghaeifar (ali.aghaeifar@tuebingen.mpg.de).

References:

Stockmann, J. P., & Wald, L. L. (2018). In vivo B0 field shimming methods for MRI at 7T. NeuroImage, 168, 71–87. https://doi.org/10.1016/j.neuroimage.2017.06.013

Aghaeifar, A., Mirkes, C., Bause, J., Steffen, T., Avdievitch, N., Henning, A., & Scheffler, K. (2018). Dynamic B0 shimming of the human brain at 9.4 T with a 16-channel multi-coil shim setup. Magnetic resonance in medicine, 80(4), 1714–1725. https://doi.org/10.1002/mrm.27110

Aghaeifar, A., Zhou, J., Heule, R., Tabibian, B., Schölkopf, B., Jia, F., Zaitsev, M., & Scheffler, K. (2020). A 32-channel multi-coil setup optimized for human brain shimming at 9.4T. Magnetic resonance in medicine, 83(2), 749–764. https://doi.org/10.1002/mrm.27929

Jia, F., Elshatlawy, H., Aghaeifar, A., Chu, Y. H., Hsu, Y. C., Littin, S., Kroboth, S., Yu, H., Amrein, P., Gao, X., Yang, W., LeVan, P., Scheffler, K., & Zaitsev, M. (2020). Design of a shim coil array matched to the human brain anatomy. Magnetic resonance in medicine, 83(4), 1442–1457. https://doi.org/10.1002/mrm.28016