title: An RF-induced voltage sensor for investigating pacemaker safety in MRI.
abstract: OBJECTIVE
  Magnetic resonance imaging (MRI) is inadvisable for patients with pacemakers, as radiofrequency (RF) voltages induced in the pacemaker leads may cause the device to malfunction. Our goal is to develop a sensor to measure such RF-induced voltages during MRI safety tests.
  
  
  METHODS
  A sensor was designed (16.6 cm(2)) for measuring voltages at the connection between the pacemaker lead and its case. The induced voltage is demodulated, digitized, and transferred by optical fibres. The sensor was calibrated on the bench using RF pulses of known amplitude and duration. Then the sensor was tested during MRI scanning at 1.5 T in a saline gel filled phantom.
  
  
  RESULTS
  Bench tests showed measurement errors below 5% with a (-40 V; +40 V) range, a precision of 0.06 V, and a temporal resolution of 24.2 μs. In MRI tests, variability in the measured voltages was below 3.7% for 996 measurements with different sensors and RF exposure. Coupling between the sensor and the MRI electromagnetic environment was estimated with a second sensor connected and was below 6.2%. For a typical clinical MRI sequence, voltages around ten Vp were detected.
  
  
  CONCLUSIONS
  We have built an accurate and reproducible tool for measuring RF-induced voltages in pacemaker leads during MR safety investigations. The sensor might also be used with other conducting cables including those used for electrocardiography and neurostimulation.
authors.affiliation: IADI, Université de Lorraine, Nancy, France, t.barbier@chu-nancy.fr.
authors.forename: Thérèse
authors.initials: T
authors.lastname: Barbier
authors.forename: Roberto
authors.initials: R
authors.lastname: Piumatti
authors.forename: Bertrand
authors.initials: B
authors.lastname: Hecker
authors.forename: Freddy
authors.initials: F
authors.lastname: Odille
authors.forename: Jacques
authors.initials: J
authors.lastname: Felblinger
authors.forename: Cédric
authors.initials: C
authors.lastname: Pasquier
mesh_terms: D000075202:Contraindications; D004867:Equipment Design; D019544:Equipment Failure Analysis; D004869:Equipment Safety / Q000295:instrumentation* / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D055100:Optical Fibers; D010138:Pacemaker, Artificial; D011846:Radio Waves; D011874:Radiometry / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014159:Transducers