title: Detection of RF unsafe devices using a parallel transmission MR system.
abstract: OBJECTIVE
  The permanent presence of devices (pacemakers) inside a patient, or the need to use other devices (catheters), for diagnosis and treatment, usually represents a contraindication for a magnetic resonance examination. To help overcome this problem, a novel and noninvasive magnetic resonance system-based concept is proposed to detect potentially unsafe radio frequency (RF) conditions of such devices to ensure patient safety.
  
  
  METHODS
  This concept makes use of parallel transmit technology by monitoring currents in individual RF transmit coil elements during RF transmission using suitable current sensors. For interventional devices, current changes can be directly measured, whereas for implanted devices, the use of reference signals is proposed, which cannot be measured in the patient.
  
  
  RESULTS
  Coupling of unsafe devices to transmit coils led to detectable current changes in the elements because of energy absorption into the device. The concept was successfully tested on interventional and implantable devices and turned out to be so sensitive that even very weak RF coupling to these devices was detectable.
  
  
  CONCLUSIONS
  In this study, basic feasibility to detect RF unsafe conditions was successfully demonstrated. In the future, RF patient safety may be improved in the presence of implanted devices, as well as during interventions using this concept.
authors.affiliation: Philips Research, Department Tomographic Imaging Systems, Hamburg, Germany.
authors.forename: Ingmar
authors.initials: I
authors.lastname: Graesslin
authors.forename: Sascha
authors.initials: S
authors.lastname: Krueger
authors.forename: Peter
authors.initials: P
authors.lastname: Vernickel
authors.forename: Johannes
authors.initials: J
authors.lastname: Achtzehn
authors.forename: Kay
authors.initials: K
authors.lastname: Nehrke
authors.forename: Steffen
authors.initials: S
authors.lastname: Weiss
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis / Q000295:instrumentation* / Q000379:methods; D004869:Equipment Safety / Q000295:instrumentation* / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D019736:Prostheses and Implants; D011874:Radiometry / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014159:Transducers