Rapid TAURUS for Relaxation-Based Color Magnetic Particle Imaging

Magnetic particle imaging (MPI) is a rapidly developing medical imaging modality that exploits the non-linear response of magnetic nanoparticles (MNPs). Color MPI widens the functionality of MPI, empowering it with the capability to distinguish different MNPs and/or MNP environments. The system function approach for color MPI relies on extensive calibrations that capture the differences in the harmonic responses of the MNPs. An alternative calibration-free x-space-based method called TAURUS estimates a map of the relaxation time constant, τ , by recovering the underlying mirror symmetry in the MPI signal. However, TAURUS requires a back and forth scanning of a given region, restricting its usage to slow trajectories with constant or piecewise constant focus fields (FFs). In this work, we propose a novel technique to increase the performance of TAURUS and enable τ map estimation for rapid and multi-dimensional trajectories. The proposed technique is based on correcting the distortions on mirror symmetry induced by time-varying FFs. We demonstrate via simulations and experiments in our in-house MPI scanner that the proposed method successfully estimates high-fidelity τ maps for rapid trajectories that provide orders of magnitude reduction in scanning time, while preserving the calibration-free property of TAURUS. ∗This work was supported by the Scientific and Technological Council of Turkey (TUBITAK) under Grants 120E208 and 217S069. †M. T. Arslan, A. A. Özaslan, and E. U. Saritas are with the Department of Electrical and Electronics Engineering, Bilkent University, 06800 Ankara, Turkey, and also with the National Magnetic Resonance Research Center (UMRAM), Bilkent University, 06800 Ankara, Turkey. E. U. Saritas is also with the Neuroscience Program, Sabuncu Brain Research Center, Bilkent University, 06800 Ankara, Turkey (corresponding author e-mail: mtarslan@ee.bilkent.edu.tr). ‡Y. Muslu is with the Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, USA, and also with the Department of Radiology, University of Wisconsin-Madison, Madison, WI, USA. §S. Kurt is with the Department of Electrical Engineering and Computer Science, KTH Royal Institute of Technology, Stockholm, Sweden, and also with the Science for Life Laboratory, Stockholm, Sweden. 1 ar X iv :2 11 2. 04 88 0v 1 [ ee ss .S P] 9 D ec 2 02 1