Modeling Endovascular MRI Coil Coupling with Transmit RF Excitation.

OBJECTIVE: To model inductive coupling of endovascular coils with transmit RF excitation for selecting coils for MRI-guided interventions.

METHODS: Independent and computationally efficient FEM models are developed for the endovascular coil, cable, transmit excitation and imaging domain. Electromagnetic and circuit solvers are coupled to simulate net B1+ fields and induced currents and voltages. Our models are validated using the Bloch Siegert B1+ mapping sequence for a series-tuned multimode coil, capable of tracking, wireless visualization and high resolution endovascular imaging.

RESULTS: Validation shows good agreement at 24, 28 and 34 μT background RF excitation within experimental limitations. Quantitative coil performance metrics agree with simulation. A parametric study demonstrates trade off in coil performance metrics when varying number of coil turns. Tracking, imaging and wireless marker multimode coil features and their integration is demonstrated in a pig study.

CONCLUSION: Developed models for the multimode coil were successfully validated. Modeling for geometric optimization and coil selection serves as a precursor to time-consuming and expensive experiments. Specific applications demonstrated include parametric optimization, coil selection for a cardiac intervention and an animal imaging experiment.

SIGNIFICANCE: Our modular, adaptable and computationally efficient modeling approach enables rapid comparison, selection and optimization of inductively-coupled coils for MRI-guided interventions.