Fast online magnetic particle imaging based on a hybrid framework combining signal demodulation and image reconstruction

Magnetic particle imaging (MPI) is a promising medical imaging technique with significant potential for biomedical applications. Fast online MPI is crucial, especially to vascular imaging, as it enables the capture of rich, dynamic details of superparamagnetic iron oxide nanoparticles (SPIONs). For system matrix-based MPI, images are usually obtained after sequential processing of signal acquisition, signal demodulation, and image reconstruction, leading to substantial imaging latency. This paper proposes a fast online imaging framework for system matrix-based MPI by combining signal demodulation and image reconstruction. The hybrid framework uses a newly defined hybrid matrix to represent the relationship between the received signals and the SPION distribution. By precomputing the hybrid matrix and storing it in memory, signal acquisition, demodulation, and image reconstruction can be processed synchronously. Theoretically, the proposed framework allows for the immediate output of the MPI image when the signal is sampled, enabling true real-time MPI. Dynamic phantom experiments were conducted to validate the performance of the proposed fast online imaging framework. Experimental results show that compared with the serial and parallel imaging frameworks, higher imaging speed of MPI can be obtained and the position of objects can be quickly and accurately determined in the field of view using the proposed framework.