A Simple Analytical Model of B1+ for MRI Measurement of RF Currents in Wire-like Medical Devices

Safe access to MRI for patients with active implants may be possible by measuring RF currents in implants in individual patients with low-SAR sequences. We present a simple theoretical model of the B1+-field close to a locally straight wire at any angle to B0. MRI signals fitted by our model closely match magnitude and complex signals from electromagnetic simulations with a wire parallel to B0 or tilted at 45° and magnitude experimental signals with parallel wire. RF currents reconstructed from simulated data match ground-truth values to within 6% and current profiles reconstructed from experimental signals follow simulated currents in shape.