Evaluation of ISO/IEC JWG Tier 3 Approach for RF Heating in 1.5 MRI with Implantable Cardiac Rhythm Devices

Yan Liu¹, Kevin Feng, Ji Chen, Xiaoyi Min², Shiloh Sison², Gabriel Mouchawar², Jon Dietrich²

The ISO/IEC Joint Working Group developed tiers to establish the worst case RF heating for active implantable devices. Tier 3 utilizes the maximum simulated tangential electric field (Etan) along lead paths. Tier 3 was evaluated in five human body models by comparing Etan and maximum of rms tangential electrical fields over lead paths (Erms). Tier 3 can overestimate the effective E by more than a factor of 2 (factor of 4 in heating). Knowing tier 1 and tier 2 are more stringent than tier 3 indicates that the ISO/IEC JWG tiers 1-3 are over conservative for implantable cardiac rhythm devices.