title: A vascular stent as an active component for locally enhanced magnetic resonance imaging: initial in vivo imaging results after catheter-guided placement in rabbits.
abstract: OBJECTIVE
  A vascular stent constructed as a high frequency resonator improves the local signal-to-noise ratio at magnetic resonance (MR) imaging. After catheter placement and intravascular expansion, the stent can be used as an inductively coupled coil for MRI. The imaging properties of this balloon-expandable active MRI stent (AMRIS) were evaluated after x-ray fluoroscopy guided placement in the abdominal aorta of five rabbits using MR angiography (MRA) and flow measurements.
  
  
  METHODS
  The AMRIS was implanted in the abdominal aorta of five rabbits using a balloon catheter inserted through the common carotid artery. The rabbits were examined by MRA (3D fast low-angle shot) at 1.5 tesla before and after intravenous injection of an iron-oxide-based blood pool contrast medium (dose 50 micro mol Fe/kg) and flow measurements (ECG-triggered phase contrast cine gradient-echo sequence). Signal-to-noise ratios (SNR) were calculated and flow volume curves were generated. The in-stent increase in temperature was measured in vitro using a fiberoptic thermometry system.
  
  
  RESULTS
  The SNR was 5.0 +/- 0.6 outside the stent and 23.2 +/- 14.1 within the stent ( < 0.0 5) in plain MRA, 19.5 +/- 5.0 outside and 30.7 +/- 8.2 within the stent ( < 0.05) in contrast enhanced MRA, and 5.8 +/- 1.6 and 13.9 +/- 5.9, respectively ( < 0.05) in the magnitude images of the flow measurements. Flow volume curves within and distal to the stent were comparable.
  
  
  CONCLUSIONS
  The expandable active MRI stent produces local signal enhancement in MRA and MR flow measurements after catheter placement and thus may improve assessment of the stented vessel segment by MR imaging.
authors.affiliation: Institut für Radiologie, Charité, Medizinische Fakultät, Humboldt-Universität zu Berlin, Berlin, Germany. dietmar.kivelitz@charite.de
authors.forename: Dietmar
authors.initials: D
authors.lastname: Kivelitz
authors.forename: Susanne
authors.initials: S
authors.lastname: Wagner
authors.forename: Jorg
authors.initials: J
authors.lastname: Schnorr
authors.forename: Rainer
authors.initials: R
authors.lastname: Wetzler
authors.forename: Martin
authors.initials: M
authors.lastname: Busch
authors.forename: Andreas
authors.initials: A
authors.lastname: Melzer
authors.forename: Matthias
authors.initials: M
authors.lastname: Taupitz
authors.forename: Bernd
authors.initials: B
authors.lastname: Hamm
mesh_terms: D000818:Animals; D001012:Aorta, Abdominal / Q000503:physiopathology*; D001783:Blood Flow Velocity; D003287:Contrast Media; D004867:Equipment Design; D005290:Ferric Compounds; D052203:Ferrosoferric Oxide; D007089:Image Enhancement / Q000295:instrumentation*; D018810:Magnetic Resonance Angiography; D008279:Magnetic Resonance Imaging; D008297:Male; D023421:Models, Animal; D010865:Pilot Projects; D011817:Rabbits; D012815:Signal Processing, Computer-Assisted; D015607:Stents
chemical_list: D003287:Contrast Media; D005290:Ferric Compounds; C427127:superparamagnetic blood pool agent; D052203:Ferrosoferric Oxide