Interleaved Imaging and Actuation for Real-Time MRI during Active Control of a Magnetically-Actuated Robotic Catheter

Magnetic Resonance Imaging (MRI)-guided robotic catheter interventions offer improved safety, visualization and control. Catheter actuation with current-carrying microcoils offers fast and responsive actuation without friction and backlash. However, actuation of this type of catheter leads to large void artifacts in MR images. We propose an interleaving method to reduce these artifacts without compromising the catheter's actuation capability.

Interleaving is accomplished by synchronizing and interleaving catheter actuation and MR image acquisition at a high switching frequency using a TTL trigger from the MR scanner that triggers an Interrupt Service Routine in the catheter firmware. Reduction in catheter duty cycle is compensated using effective currents.

Image artifact analysis showed that there is not a statistically significant difference (at 0.05 significance level) between the artifacts associated with the catheter actuating with the proposed actuation-imaging interleaving and with the catheter at rest. Catheter trajectory tracking experiments showed that the error between pure actuation trajectories and interleaved actuation-imaging trajectories is generally within the error of the tracking algorithm. These results hold for both traditional MR imaging and accelerated imaging suitable for cardiac intervention.

The proposed interleaving scheme effectively removes the artifact generated by current-carrying actuation coils while preserving the actuation capability of the catheter. The method can be used with an accelerated imaging sequence that is relevant for interventional imaging.

The proposed scheme enables simultaneous/interleaved MR visualization and catheter actuation during intervention.