International Journal on Magnetic Particle Imaging IJMPI
Vol. 9 No. 1 Suppl 1 (2023): Int J Mag Part Imag

Short Abstracts

The pitfalls of receive path calibration

Main Article Content

Florian Thieben (Section for Biomedical Imaging, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; Institute for Biomedical Imaging, Hamburg University of Technology, Hamburg, Germany), Tobias Knopp (Section for Biomedical Imaging, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; Institute for Biomedical Imaging, Hamburg University of Technology, Hamburg, Germany), Marija Boberg (Section for Biomedical Imaging, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; Institute for Biomedical Imaging, Hamburg University of Technology, Hamburg, Germany), Fynn Foerger (Section for Biomedical Imaging, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; Institute for Biomedical Imaging, Hamburg University of Technology, Hamburg, Germany), Matthias Graeser (Section for Biomedical Imaging, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; Institute for Biomedical Imaging, Hamburg University of Technology, Hamburg, Germany; Fraunhofer Research Institute for Individualized and Cell-based Medicine and the Institute for Medical Engineering, University of Lübeck, Lübeck, Germany), Martin Möddel (Section for Biomedical Imaging, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; Institute for Biomedical Imaging, Hamburg University of Technology, Hamburg, Germany)

Abstract

In Magnetic Particle Imaging (MPI) and magnetic particle spectroscopy (MPS) magnetic nanoparticles (MNPs) are exposed to static and dynamic fields. These cause a dynamic magnetization response that is typically measured with inductive coils. The signal acquisition generally occurs in parallel with the excitation. This has the consequence that the excitation field couples into each receive path. The feed-through signal is commonly dampened by advanced passive filtering, at the cost of a distorted particle signal. Consequently, the measurement signals of different MPI or MPS devices will differ, even if the underlying magnetization response of the MNPs is the same. Receive path calibration can be used to address this issue by reverting these distortions and transforming the signal into a device independent domain. The authors of this abstract studied a general calibration procedure for multi-channel, non-orthogonal and non-homogeneous receive coils along with an analytical calibration model. Furthermore, method and model uncertainties were investigated and a systematic model error that had not been accounted for in previous calibration methods has been identified. This systematic model error could be attributed to the approximation of the mutual inductance between receive and calibration coil and it becomes non-negligible in experimental setups with small inductive receivers. Suggestionswere made for estimating and reducing its influence. Finally, the method was used to calibrate the receive path of an MPS system and of a multi-channel, non-orthogonal MPI receive coil setup.

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