title: An optically coupled sensor for the measurement of currents induced by MRI gradient fields into endocardial leads.
abstract: OBJECTIVE
  The gradient fields generated during magnetic resonance imaging (MRI) procedures have the potential to induce electrical current on implanted endocardial leads. Whether this current can result in undesired cardiac stimulation is unknown.
  
  
  METHODS
  This paper provides a detailed description of how to construct an optically coupled sensor for the measurement of gradient-field-induced currents into endocardial leads. The system is based on a microcontroller that works as analog-to-digital converter and sends the current signal acquired from the lead to an optical high-speed, light-emitting diode transmitter. A plastic fiber guides the light outside the MRI chamber to a photodiode receiver and then to an acquisition board connected to a PC laptop.
  
  
  RESULTS
  The performance of the system has been characterized in terms of power consumption (8 mA on average), sampling frequency (20.5 kHz), measurement range (-12.8 to 10.3 mA) and resolution (22.6 µA). Results inside a 3 T MRI scanner are also presented.
  
  
  CONCLUSIONS
  The detailed description of the current sensor could permit more standardized study of MRI gradient current induction in pacemaker systems. Results show the potential of gradient currents to affect the pacemaker capability of triggering a heartbeat, by modifying the overall energy delivered by the stimulator.
authors.affiliation: Department of Technology and Health, Italian National Institute of Health, Viale Regina Elena 299, 00161, Rome, Italy, eugenio.mattei@iss.it.
authors.forename: Eugenio
authors.initials: E
authors.lastname: Mattei
authors.forename: Federica
authors.initials: F
authors.lastname: Censi
authors.forename: Michele
authors.initials: M
authors.lastname: Triventi
authors.forename: Antonio
authors.initials: A
authors.lastname: Napolitano
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Genovese
authors.forename: Vittorio
authors.initials: V
authors.lastname: Cannatà
authors.forename: Giovanni
authors.initials: G
authors.lastname: Calcagnini
mesh_terms: D004567:Electrodes, Implanted; D004574:Electromagnetic Fields; D004699:Endocardium / Q000601:surgery*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D055096:Optical Devices; D010138:Pacemaker, Artificial; D011874:Radiometry / Q000295:instrumentation; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014159:Transducers