title: Ultra high-field magnetic resonance imaging of a glaucoma microstent.
abstract: OBJECTIVE
  The aim of the present study was to use 7.1T magnetic resonance imaging (MRI) to determine the correct anatomical position of a non-metallic glaucoma microstent following implantation in rabbit eyes.
  
  
  METHODS
  In an in vitro experiment three microstents (made from silicone, polyurethane, and nickel titanium) were embedded in a standard vial filled with agar. In a second series of experiments a prefabricated polyurethane microstent connecting the anterior chamber with the suprachoroidal space (SCS) was implanted in rabbit eyes (n = 12). High-resolution images were acquired ex vivo (n = 6) and in vivo (n = 6) on an ultra high-field MRI unit using a 2-channel coil with four coil elements and T2-weighted turbo spin-echo sequences. Finally, the eyes were dissected and processed for histology.
  
  
  RESULTS
  Artifact-free MR imaging of silicone and polyurethane microstents was achieved in vitro, with slightly higher contrast for silicone stents. Image quality for the nickel titanium stent was greatly reduced due to artifacts. MRI examination of rabbit eyes ex vivo and in vivo following polyurethane microstent implantation presented no problems in terms of the size and placement of the coil. The sequences showed good image quality; the full length of the microstent was visualized in cross-section and longitudinal section, and correct anatomical placement was demonstrated from the anterior chamber into the SCS. These findings were verified by histology.
  
  
  CONCLUSIONS
  The excellent image quality obtained with both of the non-metallic materials generates detailed information about microstent placement, including the surrounding tissues. High-resolution MRI can be used to monitor the anatomical position of a microstent after glaucoma surgery in animal experiments and is therefore a valuable tool for documenting experimental research findings ex vivo and in vivo.
authors.affiliation: Department of Ophthalmology, University of Rostock, Germany. reto.allemann@med.uni-rostock.de
authors.forename: Reto
authors.initials: R
authors.lastname: Allemann
authors.forename: Sönke
authors.initials: S
authors.lastname: Langner
authors.forename: Martin
authors.initials: M
authors.lastname: Witt
authors.forename: Wolfram
authors.initials: W
authors.lastname: Schmidt
authors.forename: Klaus-Peter
authors.initials: KP
authors.lastname: Schmitz
authors.forename: Norbert
authors.initials: N
authors.lastname: Hosten
authors.forename: Rudolf
authors.initials: R
authors.lastname: Guthoff
authors.forename: Oliver
authors.initials: O
authors.lastname: Stachs
mesh_terms: D000818:Animals; D000867:Anterior Chamber / Q000473:pathology* / Q000601:surgery; D001672:Biocompatible Materials; D002829:Choroid / Q000473:pathology* / Q000601:surgery; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005110:Extracellular Space; D020327:Glaucoma Drainage Implants; D008279:Magnetic Resonance Imaging; D009532:Nickel; D011140:Polyurethanes; D011817:Rabbits; D012826:Silicone Elastomers; D015607:Stents; D013524:Surgical Flaps; D014025:Titanium
chemical_list: D001672:Biocompatible Materials; D011140:Polyurethanes; D012826:Silicone Elastomers; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium