title: Magnetic particle imaging: kinetics of the intravascular signal in vivo.
abstract: BACKGROUND
  Magnetic particle imaging (MPI) uses magnetic fields to visualize superparamagnetic iron oxide nanoparticles (SPIO). Today, Resovist(®) is still the reference SPIO for MPI. The objective of this study was to evaluate the in vivo blood half-life of two different types of Resovist (one from Bayer Pharma AG, and one from I'rom Pharmaceutical Co Ltd) in MPI.
  
  
  METHODS
  A Resovist concentration of 50 μmol/kg was injected into the ear artery of ten New Zealand White rabbits. Five animals received Resovist distributed by I'rom Pharmaceutical Co Ltd and five received Resovist by Bayer Pharma AG. Blood samples were drawn before and directly after injection of Resovist, at 5, 10, and 15 minutes, and then every 15 minutes until 120 minutes after the injection. The MPI signal of the blood samples was evaluated using magnetic particle spectroscopy.
  
  
  RESULTS
  The average decline of the blood MPI signal from the two distributions differed significantly (P=0.0056). Resovist distributed by Bayer Pharma AG showed a slower decline of the MPI signal (39.7% after 5 minutes, 20.5% after 10 minutes, and 12.1% after 15 minutes) compared with Resovist produced by I'rom Pharmaceutical Co Ltd (20.4% after 5 minutes, 7.8% after 10 minutes, no signal above noise level after 15 minutes).
  
  
  CONCLUSIONS
  In MPI, the blood half-life of an SPIO tracer cannot be equalized to the blood half-life of its MPI signal. Resovist shows a very rapid decline of blood MPI signal and is thus not suitable as a long circulating tracer. For cardiovascular applications in MPI, it may be used as a bolus tracer.
authors.affiliation: Clinic for Radiology and Nuclear Medicine, University Hospital Schleswig Holstein, Lübeck, Schleswig-Holstein, Germany.
authors.forename: Julian
authors.initials: J
authors.lastname: Haegele
authors.affiliation: Clinic for Radiology and Nuclear Medicine, University Hospital Schleswig Holstein, Lübeck, Schleswig-Holstein, Germany.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Duschka
authors.affiliation: Institute of Medical Engineering, University Hospital Schleswig Holstein, Lübeck, Schleswig-Holstein, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Graeser
authors.affiliation: Clinic for Radiology and Nuclear Medicine, University Hospital Schleswig Holstein, Lübeck, Schleswig-Holstein, Germany.
authors.forename: Catharina
authors.initials: C
authors.lastname: Schaecke
authors.affiliation: Clinic for Radiology and Nuclear Medicine, University Hospital Schleswig Holstein, Lübeck, Schleswig-Holstein, Germany.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Panagiotopoulos
authors.affiliation: Institute of Medical Engineering, University Hospital Schleswig Holstein, Lübeck, Schleswig-Holstein, Germany.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Lüdtke-Buzug
authors.affiliation: Institute of Medical Engineering, University Hospital Schleswig Holstein, Lübeck, Schleswig-Holstein, Germany.
authors.forename: Thorsten M
authors.initials: TM
authors.lastname: Buzug
authors.affiliation: Clinic for Radiology and Nuclear Medicine, University Hospital Schleswig Holstein, Lübeck, Schleswig-Holstein, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Barkhausen
authors.affiliation: Clinic for Radiology and Nuclear Medicine, University Hospital Schleswig Holstein, Lübeck, Schleswig-Holstein, Germany.
authors.forename: Florian M
authors.initials: FM
authors.lastname: Vogt
mesh_terms: D000818:Animals; D003911:Dextrans / Q000008:administration & dosage / Q000097:blood / Q000737:chemistry* / Q000493:pharmacokinetics*; D005260:Female; D007700:Kinetics; D058185:Magnetite Nanoparticles / Q000008:administration & dosage / Q000737:chemistry*; D057054:Molecular Imaging / Q000379:methods*; D011817:Rabbits
chemical_list: D003911:Dextrans; D058185:Magnetite Nanoparticles; C065507:ferumoxides
keywords: Resovist®; blood half-life time; magnetic particle imaging; magnetic particle spectroscopy; superparamagnetic iron oxide nanoparticles