title: Comparison of three magnetic nanoparticle tracers for sentinel lymph node biopsy in an in vivo porcine model.
abstract: BACKGROUND
  Breast cancer staging with sentinel lymph node biopsy relies on the use of radioisotopes, which limits the availability of the procedure worldwide. The use of a magnetic nanoparticle tracer and a handheld magnetometer provides a radiation-free alternative, which was recently evaluated in two clinical trials. The hydrodynamic particle size of the used magnetic tracer differs substantially from the radioisotope tracer and could therefore benefit from optimization. The aim of this study was to assess the performance of three different-sized magnetic nanoparticle tracers for sentinel lymph node biopsy within an in vivo porcine model.
  
  
  METHODS
  Sentinel lymph node biopsy was performed within a validated porcine model using three magnetic nanoparticle tracers, approved for use in humans (ferumoxytol, with hydrodynamic diameter d H =32 nm; Sienna+(®), d H =59 nm; and ferumoxide, d H =111 nm), and a handheld magnetometer. Magnetometer counts (transcutaneous and ex vivo), iron quantification (vibrating sample magnetometry), and histopathological assessments were performed on all ex vivo nodes.
  
  
  RESULTS
  Transcutaneous "hotspots" were present in 12/12 cases within 30 minutes of injection for the 59 nm tracer, compared to 7/12 for the 32 nm tracer and 8/12 for the 111 nm tracer, at the same time point. Ex vivo magnetometer counts were significantly greater for the 59 nm tracer than for the other tracers. Significantly more nodes per basin were excised for the 32 nm tracer compared to other tracers, indicating poor retention of the 32 nm tracer. Using the 59 nm tracer resulted in a significantly higher iron accumulation compared to the 32 nm tracer.
  
  
  CONCLUSIONS
  The 59 nm tracer demonstrated rapid lymphatic uptake, retention in the first nodes reached, and accumulation in high concentration, making it the most suitable tracer for intraoperative sentinel lymph node localization.
authors.affiliation: MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, the Netherlands.
authors.forename: Joost J
authors.initials: JJ
authors.lastname: Pouw
authors.affiliation: Research Oncology, Division of Cancer Studies, King's College London, Guy's Hospital, London, UK.
authors.forename: Muneer
authors.initials: M
authors.lastname: Ahmed
authors.affiliation: Research Oncology, Division of Cancer Studies, King's College London, Guy's Hospital, London, UK.
authors.forename: Bauke
authors.initials: B
authors.lastname: Anninga
authors.affiliation: MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, the Netherlands.
authors.forename: Kimberley
authors.initials: K
authors.lastname: Schuurman
authors.affiliation: Research Oncology, Division of Cancer Studies, King's College London, Guy's Hospital, London, UK.
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Pinder
authors.affiliation: Cancer Epidemiology Group, Division of Cancer Studies, King's College London, London, UK.
authors.forename: Mieke
authors.initials: M
authors.lastname: Van Hemelrijck
authors.affiliation: Healthcare Biomagnetics Laboratory, University College London, London, UK ; Institute of Biomedical Engineering, University College London, London, UK.
authors.forename: Quentin A
authors.initials: QA
authors.lastname: Pankhurst
authors.affiliation: Research Oncology, Division of Cancer Studies, King's College London, Guy's Hospital, London, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Douek
authors.affiliation: MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, the Netherlands.
authors.forename: Bennie
authors.initials: B
authors.lastname: Ten Haken
mesh_terms: D000818:Animals; D058185:Magnetite Nanoparticles; D060306:Magnetometry; D010316:Particle Size; D021701:Sentinel Lymph Node Biopsy / Q000379:methods*; D013552:Swine
chemical_list: D058185:Magnetite Nanoparticles
keywords: Sienna+®; breast cancer; ferumoxide; ferumoxytol; magnetic tracer; superparamagnetic iron oxide