title: Mapping of proton relaxation near superparamagnetic iron oxide particle-loaded polymer threads for magnetic susceptibility difference quantification.
abstract: OBJECTIVE
  Conventional radiological methods, including magnetic resonance imaging (MRI), fail to visualize polymeric surgical mesh implants because of small thread dimensions and material characteristics. For MRI delineation of such meshes, superparamagnetic iron oxide particles (SPIOs) are integrated in the mesh polymer. Usually, if SPIOs are used as an intravenous contrast agent, they increase the R1 and R2 of adjacent protons. It can be assumed that embedding SPIOs in polymers alters their molecular dynamics. The aim of this study was to investigate the influence of SPIO integration in polymer on the relaxation of adjacent protons.
  
  
  METHODS
  Polymer threads were placed in an agarose phantom. At 1.5 T, R1, R2, and R2* maps were calculated from multi inversion-recovery spin echo, multi-spin echo, and multi-gradient echo images, respectively. The threads were aligned parallel or orthogonal to B(0).
  
  
  RESULTS
  No impact of SPIO on proton R1 and R2 was observed. R2* was increased by the SPIO-loaded threads. R1 and R2 amplitude maps showed a magnetic susceptibility difference of 0.97 ppm/(mg SPIO/g polymer) around SPIO-loaded threads.
  
  
  CONCLUSIONS
  In contrast to SPIO in aqueous solutions, polymer-embedded SPIO do not affect proton R1 and R2. However, embedded SPIO generate strong local static magnetic field gradients. Thus, SPIO integration is suitable to control the magnetic susceptibility of polymer threads. This can be exploited to visualize implanted polymer-based meshes in MRI using R2* susceptible sequences. Because no impact on R1 and R2 of adjacent protons by SPIO embedded in mesh threads was observed, structures adjacent to implanted meshes will be observable in R1 and R2 maps.
authors.affiliation: Department of Diagnostic Radiology, University Hospital, RWTH Aachen University, Aachen, Germany. hank.donker@gmail.com
authors.forename: Hank C W
authors.initials: HC
authors.lastname: Donker
authors.forename: Nils A
authors.initials: NA
authors.lastname: Krämer
authors.forename: Jens
authors.initials: J
authors.lastname: Otto
authors.forename: Uwe
authors.initials: U
authors.lastname: Klinge
authors.forename: Ioana
authors.initials: I
authors.lastname: Slabu
authors.forename: Martin
authors.initials: M
authors.lastname: Baumann
authors.forename: Christiane K
authors.initials: CK
authors.lastname: Kuhl
mesh_terms: D005290:Ferric Compounds / Q000032:analysis* / Q000737:chemistry*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D011108:Polymers / Q000737:chemistry*; D011522:Protons; D013526:Surgical Mesh
chemical_list: D005290:Ferric Compounds; D011108:Polymers; D011522:Protons; C000499:ferric oxide