Accelerating implant RF safety assessment using a low-rank inverse update method

Accelerating implant RF safety assessment using a low-rank inverse update method

Stijnman, P.R.S. (University Medical Center Utrecht; Eindhoven University of Technology)
Tokaya, Janot P. (University Medical Center Utrecht)
van Gemert, J.H.F. (TU Delft Microwave Sensing, Signals & Systems; Leiden University Medical Center)
Luijten, Peter R. (University Medical Center Utrecht)
Pluim, Josien P.W. (Eindhoven University of Technology)
Brink, Wyger M. (Leiden University Medical Center)
Remis, R.F. (TU Delft Signal Processing Systems)
van den Berg, Cornelis A.T. (University Medical Center Utrecht)
Raaijmakers, Alexander J. E. (University Medical Center Utrecht; Eindhoven University of Technology)

2019

Purpose: Patients who have medical metallic implants, e.g. orthopaedic implants and pacemakers, often cannot undergo an MRI exam. One of the largest risks is tissue heating due to the radio frequency (RF) fields. The RF safety assessment of implants is computationally demanding. This is due to the large dimensions of the transmit coil compared to the very detailed geometry of an implant. Methods: In this work, we explore a faster computational method for the RF safety assessment of implants that exploits the small geometry. The method requires the RF field without an implant as a basis and calculates the perturbation that the implant induces. The inputs for this method are the incident fields and a library matrix that contains the RF field response of every edge an implant can occupy. Through a low-rank inverse update, using the Sherman–Woodbury–Morrison matrix identity, the EM response of arbitrary implants can be computed within seconds. We compare the solution from full-wave simulations with the results from the presented method, for two implant geometries. Results: From the comparison, we found that the resulting electric and magnetic fields are numerically equivalent (maximum error of 1.35%). However, the computation was between 171 to 2478 times faster than the corresponding GPU accelerated full-wave simulation. Conclusions: The presented method enables for rapid and efficient evaluation of the RF fields near implants and might enable situation-specific scanning conditions.

FDTD
implant safety
minimization problems
RF Safety
simulations

http://resolver.tudelft.nl/uuid:ab94bedd-c2d1-4263-b8c1-9fd8783c606f

https://doi.org/10.1002/mrm.28023

0740-3194

Magnetic Resonance in Medicine, 83 (2020) (5), 1796-1809

Institutional Repository

journal article

© 2019 P.R.S. Stijnman, Janot P. Tokaya, J.H.F. van Gemert, Peter R. Luijten, Josien P.W. Pluim, Wyger M. Brink, R.F. Remis, Cornelis A.T. van den Berg, Alexander J. E. Raaijmakers