Jun 10, 2021

Radiofrequency-Induced Heating of Broken and Abandoned Implant Leads During Magnetic Resonance Examinations

Aiping Yao, Tolga Goren, Theodoros Samaras, Niels Kuster, and Wolfgang Kainz, Magnetic Resonance in Medicine, October 2021, Volume 86, Issue 4, Pages 2156–2164, online 03 June 2021; doi: 10.1002/mrm.28836

The risks of radiofrequency (RF-)induced heating of active implantable medical device (AIMD) leads during magnetic resonance (MR) examinations must be well understood and realistically assessed. In this study, we evaluate the potential additional risks of broken and abandoned (cut) leads. First, we defined a generic AIMD with a metallic implantable pulse generator and a 100-cm long lead containing one or two wires. Next, we numerically estimated the deposited in vitro lead-tip power for an intact lead, as well as with wire breaks placed at 10 cm intervals. We studied the effect of the break size (wire gap width), as well as the presence of an intact wire parallel to the broken wire, and experimentally validated the numeric results for the configurations with maximum deposited in vitro lead-tip power. Finally, we performed a Tier 3 assessment of the deposited in vivo lead-tip power for the intact and broken lead in four high resolution Virtual Population anatomical models for over 54,000 MR examination scenarios. The enhancement of the deposited lead-tip power for the broken leads, compared to the intact lead, reached 30-fold in isoelectric exposure, and 16-fold in realistic clinical exposures. The presence of a nearby intact wire, or even a nearby broken wire, reduced this enhancement factor to <7-fold over the intact lead. Broken and abandoned leads can pose increased risk of RF-induced lead-tip heating to patients undergoing MR examinations. The potential enhancement of deposited in vivo lead-tip power depends on location and type of the wire break, lead design, and clinical routing of the lead, and should be carefully considered when performing risk assessment for MR examinations and MR conditional labeling.

The scientific and technical impact of the study can be summarized as:

  • RF-induced heating of generic AIMD with damaged, broken or cut (abandoned) leads were numerically studied and experimentally validated
  • Potential enhancement of RF-induced heating of the damaged AIMD during MR examinations was found to reach up to 16-fold in realistic clinical exposures
  • Enhancement depends on location and type of the wire break, lead design, and clinical routing of the lead
  • The presence of nearby intact wires, or even nearby damaged wires, mitigated the worst-case enhancement factor
  • The potential and probability of each damage type should be considered when performing risk assessment for MR examinations or device labeling
  • Mitigating efforts such as impedance checks for lead damage, or CT scans to identify abandoned (capped or cut) leads, should be considered by the community