PhD student Tobey Haluptzok successfully defends dissertation

October 25, 2025 — University of Minnesota Biomedical Engineering PhD student Tobey Haluptzok successfully defended his dissertation, "Development of Technologies to Enable Clinical 7T Body MRI" this month. He was advised by Professor Greg Metzger.

Following is the dissertation abstract:

Magnetic resonance imaging (MRI) has become an indispensable tool in both clinical and foundational research settings. As time has progressed the bounds of the main magnetic field have continued to be expanded, both lower and higher, with the current highest field strength used for body imaging sitting at 10.5 Tesla (T). However, FDA approval for clinical MRI is currently limited to 7T with only head and knee imaging being approved. This is because 7T body imaging has multiple challenges that must be addressed before clinical approval can be given. The first and foremost challenging aspect of 7T body imaging is electromagnetic (EM) field inhomogeneity. At 7T, the Larmor frequency of protons is around 297MHz which translates to an in-vivo wavelength of ~11cm. Since the dimension of the human torso is multiple times larger than this, EM interference patterns are prevalent and require careful management. The first issue related to these interference patterns is spatially varying B1+ which results in variable excitation profiles; leading to images with variable contrast and signal dropout. The second challenge resulting from the short in-vivo wavelength is constructive E-field interference which can lead to high local specific absorption rate (SAR10g). The third challenge that comes with 7T imaging is the absence of remote transmit arrays. At lower fields, the transmit coils are placed behind the bore cover of the MRI machine and typically use a birdcage geometry. However, at 7T these birdcage coils have been found to be suboptimal. Instead, 7T MRI systems typically utilize local transceiver elements that both generate the transmit B1+ field to create the MR signal and measure the MR signal from the sample. In response to these challenges, this thesis aims to develop technologies that enable clinical 7T body imaging. One of the technologies developed for this thesis was a 32-channel shielded loop-dipole body array which was validated for in-vivo use in multiple anatomies. A second technology developed for this thesis is a new radio frequency (RF) shimming method which enables large field of view (FOV) turbo-spin echo (TSE) imaging with lower scan times. In addition, an analysis of local coil placement, which introduced new coil performance metrics, was conducted to inform the design of next generation body imaging arrays for 7T MRI. Lastly, a database consisting of whole-body, fat-water reconstructed human body models was acquired and processed into segmented models which lays the groundwork for subpopulation and patient specific SAR monitoring for applications at 7T and above.