title: Safety of retained microcatheters: an evaluation of radiofrequency heating in endovascular microcatheters with nitinol, tungsten, and polyetheretherketone braiding at 1.5 T and 3 T.
abstract: BACKGROUND
  The use of ethylene-vinyl alcohol copolymer for liquid embolization of cranial vascular lesions has resulted in microcatheter fragments entrapped in patients following endovascular procedures. Undergoing subsequent diagnostic MRI examinations poses a safety concern due to the possibility of radiofrequency heating of the metallic braid incorporated into the microcatheter. Heating of nitinol, tungsten, and polyetheretherketone (PEEK) braided microcatheters was assessed and compared using a phantom model.
  
  
  METHODS
  Microcatheters coupled with fluoroptic temperature probes were embedded in a polyacrylamide gel within a head and torso phantom. Experiments were performed at 1.5 T and 3 T, analyzing the effects of different catheter immersion lengths, specific absorption rate (SAR) levels, short clinical scans, long clinical scans, and microcatheter fragment lengths.
  
  
  RESULTS
  The maximal increase in temperature for the nitinol braided microcatheter during a 15 min scan was 3.06°C using the T1 fast spin echo sequence at 1.5 T and 0.45°C using the balanced steady state free precession sequence at 3 T. The same scans for fragment lengths of 9, 18, 36, and 72 cm produced maximal temperature rises of 0.68, 0.80, 1.70, and 1.07°C at 1.5 T, respectively. The temperature changes at 3 T for these fragment lengths were 0.66, 0.83, 1.07, and 0.72°C, respectively. The tungsten and PEEK braided microcatheters did not demonstrate heating.
  
  
  CONCLUSIONS
  Substantial heating of nitinol braided microcatheters occurred and was a function of SAR level and geometric considerations. SAR and time limitations on MR scanning are proposed for patients with this microcatheter entrapped in their vasculature. In contrast, tungsten and PEEK braided microcatheters showed potential safe use in MRI.
authors.affiliation: Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California, USA.
authors.forename: Aaron D
authors.initials: AD
authors.lastname: Losey
authors.forename: Prasheel
authors.initials: P
authors.lastname: Lillaney
authors.forename: Alastair J
authors.initials: AJ
authors.lastname: Martin
authors.forename: Van V
authors.initials: VV
authors.lastname: Halbach
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Cooke
authors.forename: Christopher F
authors.initials: CF
authors.lastname: Dowd
authors.forename: Randall T
authors.initials: RT
authors.lastname: Higashida
authors.forename: David A
authors.initials: DA
authors.lastname: Saloner
authors.forename: Mark W
authors.initials: MW
authors.lastname: Wilson
authors.forename: Maythem
authors.initials: M
authors.lastname: Saeed
authors.forename: Steven W
authors.initials: SW
authors.lastname: Hetts
mesh_terms: D000497:Alloys / Q000528:radiation effects*; D001577:Benzophenones; D060733:Electromagnetic Radiation; D004621:Embolization, Therapeutic / Q000009:adverse effects*; D006358:Hot Temperature / Q000009:adverse effects*; D006801:Humans; D007659:Ketones / Q000528:radiation effects*; D008279:Magnetic Resonance Imaging / Q000009:adverse effects*; D011092:Polyethylene Glycols / Q000528:radiation effects*; D011108:Polymers; D014414:Tungsten / Q000528:radiation effects*; D062666:Vascular Access Devices / Q000009:adverse effects*
chemical_list: D000497:Alloys; D001577:Benzophenones; D007659:Ketones; D011108:Polymers; C013616:nitinol; C063834:polyetheretherketone; D011092:Polyethylene Glycols; D014414:Tungsten
keywords: Catheter; Intervention; Liquid Embolic Material; MRI; Material