Magnetic Field Strength Encoded Handheld Magnetic Particle Imaging System With Multiwaveform Excitation

Magnetic particle imaging (MPI) is an innovative medical imaging modality with tremendous potential for various clinical applications. The handheld MPI device, due to its high biosafety and portability, holds promise for use in intraoperative diagnosis and other clinical settings. The handheld MPI system has all its hardware components located on one side of the imaged object, enabling convenient mobile detection. However, this single-sided construction leads to a reduced magnetic field gradient of the selection field, resulting in a compromised imaging field of view (FOV) and resolution. To address these challenges, this study proposes a handheld MPI system that utilizes excitation field intensity encoding. By gradually increasing the calibrated excitation field, spatial encoding is achieved throughout the FOV. To improve the imaging resolution of the system, three different excitation waveforms are applied to the excitation coil to expand the available harmonic signals. In addition, a bidirectional adjustable external compensation strategy is introduced to achieve more precise direct feedthrough suppression, restoring the baseband signal. Experimental results demonstrate that the proposed handheld MPI achieves a spatial resolution of 1 mm within a depth range of 30 mm while maintaining imaging FOV, resolution, and detection sensitivity of 50-ng Fe, laying a foundation for future clinical applications.