Reference-Free Detection of RF Unsafe Conditions and Countermeasures for Implantable MR-Conditional Devices

Ingmar Graesslin¹, Johannes Achtzehn¹, Sascha Krueger¹, Peter Vernickel¹, Kay Nehrke¹, Steffen Weiss¹

The presence of implants mostly represents a contraindication for MR examinations. Here, a concept based on parallel transmit technology is used to detect potentially RF-unsafe conditions due to implants by monitoring the currents in transmit coils. The original method had required a reference scan without device. Here, the method was improved by exploiting the left-right symmetry of patients to avoid the reference scan. Hence, the method may be applied to patients with implants. Basic feasibility of this concept is shown in pseudo-in vivo and phantom studies by detecting coupling to pacemaker leads. Tip heating could be reduced by a factor of 6 by changing the transmit phases.