Notes on quantitative susceptibility mapping reconstruction accuracy under challenging conditions: Phantom measurements and simulations

Lundberg A, Lind E, Knutsson L, Wirestam R

Pdf Page Numbers :- 111-117

Anna Lundberg¹, Emelie Lind¹, Linda Knutsson^1,2,3 and Ronnie Wirestam^1,*

¹Department of Medical Radiation Physics, Lund University, Lund, Sweden

²Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA

³F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA

*Corresponding author: Ronnie Wirestam, Department of Medical Radiation Physics, Lund University, Skåne University Hospital, SE-22185 Lund, Sweden. Telephone: +4646177159; Email: ronnie.wirestam@med.lu.se

Received 12 April 2022; Revised 13 June 2022; Accepted 21 June 2022; Published 29 June 2022

Citation: Lundberg A, Lind E, Knutsson L, Wirestam R. Notes on quantitative susceptibility mapping reconstruction accuracy under challenging conditions: Phantom measurements and simulations. J Med Sci Res. 2022; 10(3):111-117. DOI: http://dx.doi.org/10.17727/JMSR.2022/10-21

Copyright: © 2022 Lundberg A et al. Published by KIMS Foundation and Research Center. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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Abstract

Magnetic susceptibility can be assessed by quantitative susceptibility mapping (QSM), based on measured magnetic resonance imaging (MRI) phase data. The QSM reconstruction process is, however, mathematically challenging and still not fully robust. A signal-generating holmium [Ho(III)] aqueous solution with air-equivalent magnetic susceptibility was prepared, and used as a surrounding medium in a water phantom with tubes filled with a solution of gadolinium contrast agent at various concentrations. Extended analyses under controlled conditions were accomplished by simulations of the phantom construction. Without surrounding holmium solution, a gadolinium tube positioned centrally, parallel with B₀, showed a susceptibility difference that agreed well with theoretical values, whereas a peripheral parallel tube position showed larger deviation. Orientation perpendicular to B₀ resulted in less variation between the internal tube positions. Air-equivalent magnetic susceptibility corresponded to 16.5 mM Ho(III) solution. With surrounding holmium solution, several post-processing steps became challenging. Simulations indicated higher degree of underestimation when the theoretical susceptibility difference increased. Details in the mathematical implementation, for example, background field removal can strongly influence the result. Simulated results were, in part, unexpected, and provided awareness of limitations in the reconstruction technique, mainly related to conditions with large susceptibility differences between compartments.

Keywords: magnetic resonance imaging; magnetic phenomena; magnetometry; computer simulation; contrast media