Introduction: Determining MRI RF heating safety is a complex process which requires complete understanding of the potential interactions between the MRI system, lead behavior, and individual patient characteristics. (Reference 1) A comprehensive analysis was performed to evaluate a new MR-compatible SCS lead.
Methods: Anesthetized porcine (n=5) were implanted with leads and temperature probes in the spinal canal (Figure 1) and scanned in a 1.5T MRI system at multiple landmarks. MRI RF heating predictions from animal model simulations were compared to in vivo electrode temperature measurement in order to confirm model accuracy. Multiple human models were combined with several MRI coils to simulate the electromagnetic effects due to variations in human morphology. Simulations were performed for hundreds of clinical lead paths in each human model and combined with lead characterization analyses to predict the temperature rise at the electrodes in the spinal cord for each patient situation.
Results: A comparison of in vivo tissue temperatures during actual MRI with predicted temperatures from animal models (Figure 2) depicts model accuracy and provides confidence in predicting patient RF electrode heating across the range of clinical scenarios. (Reference 2) Calculation of electrode temperatures across 10,000 different patient/device/MRI scenarios shows highly variable temperature rise. The resulting temperature predictions demonstrated that a lead designed for reduced RF heating produced temperatures below 43C for the full range of implant scenarios.
Conclusions: Safety of an MRI compatible spinal cord stimulation lead was demonstrated with validated models that account for the full complexity of MRI environment and variables.
Patient Care: This testing contributes to our understanding of heating risks during MRI.
Learning Objectives: MRI scanning risks with implantable devices, Testing methods for MR compatibility
References: Reference #1:
ISO. 2012. ISO TS 10974: Assessment of the safety of magnetic resonance imaging for
patients with an active implantable medical device. Geneva, Switzerland: International
Organization for Standardization.
Orser, et al "Analysis and In-Vivo Results of MRI Radiofrequency Heating Due to
Neuromodulation Systems," International Neuromodulation Society 11th World