Advancing intraoperative magnetic tracing using 3D freehand magnetic particle imaging

Area of Science:

• Medical Imaging
• Surgical Navigation
• Nanotechnology

Background:

• Sentinel lymph node biopsy is crucial for penile cancer staging.
• Current guidance relies on radioactive tracers and fluorescence imaging.
• Magnetic approaches using superparamagnetic iron-oxide nanoparticles (SPIONs) offer an alternative.

Purpose of the Study:

• To investigate a novel freehand magnetic particle imaging and navigation (fhMPI) modality.
• To evaluate a hybrid approach combining magnetic and fluorescence guidance for sentinel lymph node localization.

Main Methods:

• Developed an fhMPI system with surgical navigation, optical tracking, and a magnetometer probe.
• Utilized a look-up-table method for 3D SPION distribution reconstruction.
• Incorporated indocyanine green (ICG) for fluorescence guidance and tested in phantoms, ex vivo skin, and in vivo porcine models.

Main Results:

• The fhMPI system demonstrated a sensitivity of 2.2 × 10⁻² mg/mL SPIONs, resolution of at least 7 mm, and depth penetration up to 1.5 cm.
• In vivo porcine surgery showed fhMPI provided augmented reality overlay and 3D virtual navigation.
• The hybrid approach with ICG enabled visual confirmation of lymph node localization.

Conclusions:

• Freehand magnetic particle imaging and navigation (fhMPI) is feasible in vivo for 3D imaging and navigation in the operating room.
• This technology expands guidance options for magnetic sentinel lymph node procedures.
• Integrating ICG allows for visual refinement and confirmation of localization, warranting further clinical evaluation.