title: Real-time MR properties of particulate embolic agents tested in a dynamic flow model.
abstract: OBJECTIVE
  Interventional magnetic resonance (MR)-guided transcatheter embolization could potentially limit radiation exposure and improve visualization of target organs. The feasibility of monitoring injection and distribution of embolic agents was assessed in a dynamic flow model with real-time MR imaging.
  
  
  METHODS
  MR-compatible flow models were constructed with use of clear plastic chambers containing 170-microm polyethylene tubular filters. Gadolinium (Gd)-impregnated polyvinyl alcohol (PVA) particles (355-500 and 500-710 microm in size) and Gd-impregnated microspheres (Embospheres, 300-500 and 500-700 microm in size) were injected into the flow circuit under real-time dynamic T1-weighted fast field echo guidance at four images per second. A dynamic steady-state free precession sequence at four images per second was used to monitor the injection of unmodified Embo-Gold 700-900- microm particles. High-resolution scans were obtained before and after each particle injection.
  
  
  RESULTS
  MR signal enhancement on the dynamic T1-weighted fast field echo sequence was visible during the injection of Gd-impregnated microspheres. Gd-impregnated PVA particles were not detected by this sequence. After injection, microsphere and PVA localization to the filter chambers was confirmed by the high-resolution scans. On the high-resolution sequences, relative MR signal enhancement of the microspheres was higher than that of the PVA particles. The Embo-Gold particles were minimally detectable on the dynamic sequence and undetectable by the high-resolution scan. After particle injection, direct inspection of the filter chamber showed trapping of all particle types and sizes.
  
  
  CONCLUSIONS
  Real-time MR tracking of Gd-impregnated embolic agents is possible in vitro.
authors.affiliation: Department of Radiology, University of California, San Francisco, 505 Parnassus Avenue, Room M-361, San Francisco, California 94143-0628, USA.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Fidelman
authors.forename: Mark W
authors.initials: MW
authors.lastname: Wilson
authors.forename: Oliver M
authors.initials: OM
authors.lastname: Weber
authors.forename: Alastair J
authors.initials: AJ
authors.lastname: Martin
authors.forename: Robert K
authors.initials: RK
authors.lastname: Kerlan
authors.forename: Jeanne M
authors.initials: JM
authors.lastname: LaBerge
authors.forename: Roy L
authors.initials: RL
authors.lastname: Gordon
mesh_terms: D004621:Embolization, Therapeutic; D005682:Gadolinium; D066298:In Vitro Techniques; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008863:Microspheres; D008954:Models, Biological; D011142:Polyvinyl Alcohol
chemical_list: D011142:Polyvinyl Alcohol; D005682:Gadolinium