title: Transparent thin shield for radio frequency transmit coils.
abstract: OBJECTIVE
  To identify a shielding material compatible with optical head-motion tracking for prospective motion correction and which minimizes radio frequency (RF) radiation losses at 7 T without sacrificing line-of-sight to an imaging target.
  
  
  METHODS
  We evaluated a polyamide mesh coated with silver. The thickness of the coating was approximated from the composition ratio provided by the material vendor and validated by an estimate derived from electrical conductivity and light transmission measurements. The performance of the shield is compared to a split-copper shield in the context of a four-channel transmit-only loop array.
  
  
  RESULTS
  The mesh contains less than a skin-depth of silver coating (300 MHz) and attenuates light by 15 %. Elements of the array vary less in the presence of the mesh shield as compared to the split-copper shield indicating that the array behaves more symmetrically with the mesh shield. No degradation of transmit efficiency was observed for the mesh as compared to the split-copper shield.
  
  
  CONCLUSIONS
  We present a shield compatible with future integration of camera-based motion-tracking systems. Based on transmit performance and eddy-current evaluations the mesh shield is appropriate for use at 7 T.
authors.affiliation: Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstrasse 1a, 04103, Leipzig, Germany, debsrivera@gmail.com.
authors.forename: Debra S
authors.initials: DS
authors.lastname: Rivera
authors.forename: Jessica
authors.initials: J
authors.lastname: Schulz
authors.forename: Thomas
authors.initials: T
authors.lastname: Siegert
authors.forename: Verena
authors.initials: V
authors.lastname: Zuber
authors.forename: Robert
authors.initials: R
authors.lastname: Turner
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D055096:Optical Devices; D011835:Radiation Protection / Q000295:instrumentation*; D011846:Radio Waves; D014159:Transducers