Production of magnetic probe field using quantum sensor and ferromagnetic materials for lymph node detection

Abstract—We have developed a magnetic probe with a diamond quantum sensor and electromagnetic coils for detection of sentinel lymph nodes (SLNs) as a medical application of diamond quantum sensing. The probe magnetizes the magnetic nanoparticles (MNPs) accumulated in the SLNs and detects the magnetic fields of the magnetic MNPs. We designed a ferromagnetic core that has a unique shape and optimized the magnetic field generation system to improve detection performance, such as magnetic sensitivity and detectable distance. The proposed magnetic core increases the excitation magnetic field strength over a longer distance and suppresses the bias field strength at the location of the diamond quantum sensor. The increase of the excitation field is approximately 370% and the decrease of the bias field is approximately 45%. In addition to the proposed magnetic core, even with the application of a removal coil, the excitation field strength is tenfold compared to the single-coil structure, indicating that further magnetization of MNPs produces a large magnetic field for a longer detectable distance.