title: Real-time MR-guided retrieval of inferior vena cava filters: an in vitro and animal model study.
abstract: OBJECTIVE
  To develop interventional magnetic resonance (MR) guidance techniques for inferior vena cava (IVC) filter retrieval in vitro and demonstrate feasibility in vivo.
  
  
  METHODS
  Three optional IVC filters and their retrieval systems were investigated. Experiments were performed on a 1.5-T MR system. Real-time MR imaging was optimized by using a custom-built IVC phantom. A three-dimensional (3D) contrast-enhanced MR venography sequence was optimized in vitro for improved detection of thrombus trapped within the filters. Filters were then retrieved in vitro and in vivo in a swine model under MR guidance. In-vivo retrieval procedure time was measured.
  
  
  RESULTS
  The combination of one of the nitinol filters and a loop snare was suitable for real-time MR procedures. With a 90° flip angle, 3D MR venography allowed detection of simulated thrombus within the filter. A radial true fast imaging sequence with steady-state precession allowed visualization of the loop snare and IVC filter hook and successful retrieval of the filter in vivo and in vitro. In-vivo MR fluoroscopy time for retrieval was 97 seconds ± 51 (mean ± SD).
  
  
  CONCLUSIONS
  MR-guided retrieval of a nitinol-based IVC filter by using a loop snare is feasible with the use of optimized sequences and passive device tracking.
authors.affiliation: Department of Radiology and Medical Imaging, University of Virginia Health System, Lee Street, Charlottesville, VA 22908, USA.
authors.forename: Ming-Chen Paul
authors.initials: MC
authors.lastname: Shih
authors.forename: Walter J
authors.initials: WJ
authors.lastname: Rogers
authors.forename: Hugo
authors.initials: H
authors.lastname: Bonatti
authors.forename: Klaus D
authors.initials: KD
authors.lastname: Hagspiel
mesh_terms: D000818:Animals; D003287:Contrast Media; D020878:Device Removal; D005240:Feasibility Studies; D019786:Gadolinium DTPA; D053783:Magnetic Resonance Imaging, Interventional / Q000295:instrumentation; D008422:Materials Testing; D023421:Models, Animal; D019047:Phantoms, Imaging; D011474:Prosthesis Design; D034421:Sus scrofa; D013997:Time Factors; D016306:Vena Cava Filters; D020246:Venous Thrombosis / Q000473:pathology / Q000628:therapy*
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA