title: The active magnetic resonance imaging stent (AMRIS): initial experimental in vivo results with locally amplified MR angiography and flow measurements.
abstract: OBJECTIVE
  Magnetic resonance (MR) is limited by artifacts in vessels after stenting. An active MR imaging stent (AMRIS) allows for artifact-free imaging with local improvement in signal-to-noise ratio (SNR). In a rabbit model, we evaluated the imaging properties by MR angiography (MRA) and flow measurements.
  
  
  METHODS
  The AMRIS was placed in the abdominal aorta of five rabbits. At 1.5 T, MRA (three-dimensional fast low-angle shot) was performed before and after intravenous injection of an iron oxide-based, blood-pool contrast medium (dose, 50 micromol Fe/kg), and flow measurements were performed (electrocardiographically triggered phase-contrast cine gradient-echo sequence). Mean SNRs were calculated and flow volume curves were generated.
  
  
  RESULTS
  The SNR was 6.0 +/- 0.6 (outside the stent) versus 12.3 +/- 1.1 (inside the stent, P < 0.05) for plain MRA, 21.2 +/- 0.6 versus 40.6 +/- 5.2 (P < 0.05) for contrast-enhanced MRA, and 5.4 +/- 0.4 versus 13.7 +/- 2.1 (P < 0.05) for the magnitude images of flow measurements. Flow volume curves within and distal to the stent were comparable.
  
  
  CONCLUSIONS
  By using the AMRIS as a vascular stent, the stented vessel segment can be examined with enhanced signal intensity on MRI.
authors.affiliation: Institut für Radiologie, Charité, Medizinische Fakultät, Humboldt-Universität zu Berlin, Schumannstrasse 20/21, 10098 Berlin, Germnay. dietmar.kivelitz@charite.de
authors.forename: D
authors.initials: D
authors.lastname: Kivelitz
authors.forename: S
authors.initials: S
authors.lastname: Wagner
authors.forename: J
authors.initials: J
authors.lastname: Hansel
authors.forename: J
authors.initials: J
authors.lastname: Schnorr
authors.forename: R
authors.initials: R
authors.lastname: Wetzler
authors.forename: M
authors.initials: M
authors.lastname: Busch
authors.forename: A
authors.initials: A
authors.lastname: Melzer
authors.forename: M
authors.initials: M
authors.lastname: Taupitz
authors.forename: B
authors.initials: B
authors.lastname: Hamm
mesh_terms: D000818:Animals; D001012:Aorta, Abdominal / Q000473:pathology* / Q000601:surgery; D016477:Artifacts; D001783:Blood Flow Velocity; D003287:Contrast Media / Q000008:administration & dosage; D005290:Ferric Compounds; D052203:Ferrosoferric Oxide; D007275:Injections, Intravenous; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D011817:Rabbits; D015607:Stents
chemical_list: D003287:Contrast Media; D005290:Ferric Compounds; C427127:superparamagnetic blood pool agent; D052203:Ferrosoferric Oxide