Phase-sensitive signal processing for improved usability of the DiffMag handheld probe

Sentinel lymph node biopsy (SLNB) is the standard method for surgical lymph node (LN) staging, typically using a radioactive tracer and handheld detector. Superparamagnetic iron oxide nanoparticles (SPIONs) with magnetic readout offer an alternative, but their clinical utility is hindered by low specificity and interference from surgical instruments. The DiffMag handheld (DMH) probe, based on differential magnetometry, improves SPION sensitivity but remains vulnerable to motion artefacts caused by nearby metal. To address this, we developed a phase-sensitive detection algorithm capable of distinguishing SPION signals from motion artefacts. The algorithm was integrated into the DMH and validated through benchtop experiments and a usability study. Results demonstrate enhanced detection accuracy in metal-rich surgical environments, supporting its potential for more reliable SLNB.Clinical relevance-This establishes a detection algorithm to increase usability of handheld magnetometers in metal-rich surgical environments.