title: USPIO-enhanced direct MR imaging of thrombus: preclinical evaluation in rabbits.
abstract: OBJECTIVE
  To test the hypothesis that ultrasmall superparamagnetic iron oxide (USPIO) particles may diffuse into nonendothelialized fresh thrombi and thus allow for direct magnetic resonance (MR) imaging of a thrombus.
  
  
  METHODS
  Stagnation thrombi of different thrombus ages (1, 3, 5, 7, and 9 days) were induced in the external jugular veins of 25 rabbits. Direct MR imaging of thrombi was performed by using a fat-saturated T1-weighted gradient-echo sequence (three-dimensional [3D] magnetization prepared rapid acquisition gradient echo) before and 24 hours after intravenous administration of USPIO (particle size, 25 nm; 200 micromol per kilogram of body weight). Thrombus length on 3D reconstruction images was compared with that depicted on a radiographic venogram and with histologic findings (joint reference standard). In addition, T2*-weighted gradient-echo images were acquired and scored semiquantitatively.
  
  
  RESULTS
  The hyperintensity of the thrombus segment depicted on T1-weighted images (thrombus length determined with 3D reconstruction images divided by true thrombus length) increased significantly after administration of contrast medium at a thrombus age of 3 days (0.6 +/- 0.4 [SD] to 0.8 +/- 0.4; P =.02), 5 days (0.1 +/- 0.1 to 1.0 +/- 0.1; P <.001), and 7 days (0 to 0.6 +/- 0.4; P =.02), but not at an age of 1 and 9 days. No significant change in the thrombus signal intensity was observed on T2*-weighted images.
  
  
  CONCLUSIONS
  The animal model showed that direct MR imaging of the thrombus improved 24 hours after USPIO administration with a T1-weighted sequence. No improvement was seen with the T2*-weighted sequence.
authors.affiliation: Department of Radiology and Nuclear Medicine, Universitätsklinikum Benjamin Franklin, Freie Universität Berlin, Hindenburgdamm 30, 12200 Berlin, Germany. s.schmitz@medizin.fu-berlin.de
authors.forename: S A
authors.initials: SA
authors.lastname: Schmitz
authors.forename: S
authors.initials: S
authors.lastname: Winterhalter
authors.forename: S
authors.initials: S
authors.lastname: Schiffler
authors.forename: R
authors.initials: R
authors.lastname: Gust
authors.forename: S
authors.initials: S
authors.lastname: Wagner
authors.forename: M
authors.initials: M
authors.lastname: Kresse
authors.forename: S E
authors.initials: SE
authors.lastname: Coupland
authors.forename: W
authors.initials: W
authors.lastname: Semmler
authors.forename: K J
authors.initials: KJ
authors.lastname: Wolf
mesh_terms: D000818:Animals; D003287:Contrast Media; D003911:Dextrans; D004195:Disease Models, Animal; D005260:Female; D052203:Ferrosoferric Oxide; D007501:Iron; D008279:Magnetic Resonance Imaging / Q000379:methods*; D058185:Magnetite Nanoparticles; D008297:Male; D010087:Oxides; D010690:Phlebography; D011817:Rabbits; D013927:Thrombosis / Q000473:pathology*
chemical_list: D003287:Contrast Media; D003911:Dextrans; D058185:Magnetite Nanoparticles; D010087:Oxides; C097921:ferumoxtran-10; D007501:Iron; D052203:Ferrosoferric Oxide