title: MRI of the Ex-PRESS stainless steel glaucoma drainage device.
abstract: OBJECTIVE
  To evaluate the magnetic properties of the Ex-PRESS stainless steel glaucoma drainage device during MRI.
  
  
  METHODS
  Experimental study.
  
  
  METHODS
  The Ex-PRESS glaucoma drainage device (316L stainless steel) was examined for magnetic field interactions under standard 1.5, 3.0, and 4.7 T MRI scanning protocols. Testing included measurements of translational and rotational motion of the device induced by static magnetic fields. In addition, the change in the temperature of the device was measured to assess the presence of radiofrequency heating of the stainless steel device.
  
  
  METHODS
  Degree of angular deflection, device displacement and rotation, and change in temperature.
  
  
  RESULTS
  During induced torque testing, displacement did not occur under 1.5 and 3.0 T conditions, although a significant amount of displacement occurred in the 4.7 T environment. Increasing amounts of angular deflection were demonstrated at all three field strengths. We did not record significant temperature changes during brain MRI sequences at any of the three MRI strengths.
  
  
  CONCLUSIONS
  The Ex-PRESS glaucoma drainage device, manufactured from grade 316L stainless steel, does move in the presence of high magnetic fields. The clinical significance of this finding and translation to in vivo conditions are not currently known. Further studies are needed to better understand how patients might be affected by the magnetic properties of this device post implantation and how patients should be counselled in regards to safety of MRI in the early and late postoperative period.
authors.affiliation: Department of Ophthalmology, Rocky Mountain Lions Eye Institute, University of Colorado at Denver, Aurora, CO 80045, USA.
authors.forename: Leonard K
authors.initials: LK
authors.lastname: Seibold
authors.forename: Ronald A L
authors.initials: RA
authors.lastname: Rorrer
authors.forename: Malik Y
authors.initials: MY
authors.lastname: Kahook
mesh_terms: D004574:Electromagnetic Fields; D004869:Equipment Safety; D020327:Glaucoma Drainage Implants / Q000009:adverse effects*; D005902:Glaucoma, Open-Angle / Q000628:therapy; D006801:Humans; D008279:Magnetic Resonance Imaging; D013193:Stainless Steel; D019415:Torque
chemical_list: D013193:Stainless Steel