Phase-sensitive signal processing in DiffMag handheld probe

Abstract

Sentinel Lymph Node Biopsy (SLNB) is a surgical procedure that employs a tracer and a handheld detection device. Superparamagnetic iron oxide nanoparticles (SPIONs) show promise as tracers, while handheld magnetometers are utilized for detection. However, conventional magnetometers face interference from tissue and surgical instruments, complicating procedures. The DiffMag processing technique, assessing solely SPIONs, is prototyped as the DiffMag handheld (DMH) probe. However, movement of the DMH-probe near surgical instrumentation may generate inconvenient signal artefacts. This study provides an extension of the DiffMag sensing principle with phase-sensitive signal processing. In this study we evaluated the efficacy of phase-sensitive detection through assessment of system phase shift factors originating from the introduced phase from electrical components and we examined SPION phase lag within clinically relevant parameter ranges, such as low SPION concentrations and increased environmental viscosity for assessment of technique limitations. The DMH-probe was used for acquisition of phase data of various SPIONs (Magtrace®, Resotran®, Resovist®, Ferrotrace®) and compared to a baseline acquisition in the absence of SPIONs. System phase shift was observed to be a wide-sense stationarity signal with consistent values for consecutive days, highlighting the stability of the system. Probe heating is observed results in a relatively small non-linear increase in system phase shift. All SPIONs display a distinct phase difference from the baseline acquisition in both low concentrations, and relatively high environmental viscosities. In conclusion, the phase-sensitive signal processing utilised in the DMH-probe demonstrates strong potential for identifying signal artefacts.