Magnetic Field Generation System of the Magnetic Probe With Diamond Quantum Sensor and Ferromagnetic Materials for the Detection of Sentinel Lymph Nodes With Magnetic Nanoparticles

We have developed the magnetic probe with a diamond quantum sensor and electromagnetic coils to detect sentinel lymph nodes (SLNs), as the medical application of diamond quantum sensing. The probe magnetizes magnetic nanoparticles (MNPs) accumulated in SLNs and detect the magnetic fields of magnetized MNPs. In this study, we designed a ferromagnetic core that has a unique shape and optimized the magnetic field generation system for improving the detection performance such as the magnetic sensitivity and detectable distance. The proposed magnetic core enhances an excitation magnetic field strength at a longer distance and suppresses a bias field strength at a location of the diamond quantum sensor. The increment of the excitation field is approximately 370% and the decrement of the bias field is approximately 45%. In addition to the proposed magnetic core, even applying a cancellation coil, the excitation field strength is tenfold compared with the coil only structure, suggesting the larger magnetization of MNPs generates the large magnetic field for longer detectable distance.