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In recent years, the rapid development of magnetic particle imaging technology has provided a good imaging tool for many preclinical applications. Open-sided field free line magnetic particle imaging (FFL-MPI) is not only highly sensitive to magnetic nanoparticles (MNPs), but also suitable for applications such as interventional therapy. When the image is reconstructed based on the system matrix, the system matrices need to be measured at all angles by rotating FFL magnetic field (rFFL), which is complicated and time-consuming. In this paper, We find that the system function of open-sided FFL-MPI is rotation invariant. Then, a method for fast estimating the system matrices at other angles by rotating system function (rSF) at the initial angle is proposed. Finally, the simulation experiments show that the reconstructed results of rSF and rFFL are highly consistent under ideal fields, which proves that our research can greatly reduce the time required for system matrices calibration in open-sided FFL-MPI.
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