title: Positive contrast MR-lymphography using inversion recovery with ON-resonant water suppression (IRON).
abstract: OBJECTIVE
  To investigate the utility of inversion recovery with ON-resonant water suppression (IRON) to create positive signal in normal lymph nodes after injection of superparamagnetic nanoparticles.
  
  
  METHODS
  Experiments were conducted on six rabbits, which received a single bolus injection of 80 mumol Fe/kg monocrystalline iron oxide nanoparticle (MION-47). Magnetic resonance imaging (MRI) was performed at baseline, 1 day, and 3 days after MION-47 injection using conventional T(1)- and T(2)*-weighted sequences and IRON. Contrast-to-noise ratios (CNR) were measured in blood and in paraaortic lymph nodes.
  
  
  RESULTS
  On T(2)*-weighted images, as expected, signal attenuation was observed in areas of paraaortic lymph nodes after MION-47 injection. However, using IRON the paraaortic lymph nodes exhibited very high contrast enhancement, which remained 3 days after injection. CNR with IRON was 2.2 +/- 0.8 at baseline, increased markedly 1 day after injection (23.5 +/- 5.4, P < 0.01 vs. baseline), and remained high after 3 days (21.8 +/- 5.7, *P < 0.01 vs. baseline). CNR was also high in blood 1 day after injection (42.7 +/- 7.2 vs. 1.8 +/- 0.7 at baseline, P < 0.01) but approached baseline after 3 days (1.9 +/- 1.4, P = NS vs. baseline).
  
  
  CONCLUSIONS
  IRON in conjunction with superparamagnetic nanoparticles can be used to perform 'positive contrast' MR-lymphography, particularly 3 days after injection of the contrast agent, when signal is no longer visible within blood vessels. The proposed method may have potential as an adjunct for nodal staging in cancer screening.
authors.affiliation: University of Heidelberg, Department of Cardiology, Heidelberg, Germany.
authors.forename: Grigorios
authors.initials: G
authors.lastname: Korosoglou
authors.forename: Lijun
authors.initials: L
authors.lastname: Tang
authors.forename: Dorota
authors.initials: D
authors.lastname: Kedziorek
authors.forename: Kenyatta
authors.initials: K
authors.lastname: Cosby
authors.forename: Wesley D
authors.initials: WD
authors.lastname: Gilson
authors.forename: Evert-Jan
authors.initials: EJ
authors.lastname: Vonken
authors.forename: Michael
authors.initials: M
authors.lastname: Schär
authors.forename: David
authors.initials: D
authors.lastname: Sosnovik
authors.forename: Dara L
authors.initials: DL
authors.lastname: Kraitchman
authors.forename: Robert G
authors.initials: RG
authors.lastname: Weiss
authors.forename: Ralf
authors.initials: R
authors.lastname: Weissleder
authors.forename: Matthias
authors.initials: M
authors.lastname: Stuber
mesh_terms: D000005:Abdomen; D000704:Analysis of Variance; D000818:Animals; D003287:Contrast Media / Q000008:administration & dosage / Q000493:pharmacokinetics*; D003911:Dextrans; D052203:Ferrosoferric Oxide; D007091:Image Processing, Computer-Assisted; D007267:Injections; D007501:Iron / Q000008:administration & dosage / Q000493:pharmacokinetics*; D008198:Lymph Nodes / Q000378:metabolism*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D058185:Magnetite Nanoparticles; D008297:Male; D053758:Nanoparticles; D010087:Oxides / Q000008:administration & dosage / Q000493:pharmacokinetics*; D011817:Rabbits
chemical_list: D003287:Contrast Media; D003911:Dextrans; D058185:Magnetite Nanoparticles; D010087:Oxides; D007501:Iron; C065507:ferumoxides; D052203:Ferrosoferric Oxide