The catheter-driven MRI scanner: A new approach to intravascular catheter tracking and imaging parameter adjustment for interventional MRI

OBJECTIVE. Our aim was to test the feasibility of a hands-free approach to MRI that allows the interventionalist to track an angiographic catheter in real time throughout the procedure and to automatically change imaging parameters by catheter manipulation. MATERIALS AND METHODS. A tracking method that is based on an active device localization was implemented on a 1.5-T MRI scanner. The system determines the current position and orientation of a catheter in 3D space in an endless feedback loop. Automatic scanning planeadjustment procedures written in the software of the MRI system ensure image acquisition at the location of the catheter tip. The system calculates the device velocity to automatically adjust parameters such as field of view (FOV) and resolution. To evaluate the feasibility and performance in vivo and ex vivo, we performed experiments in two vessel phantoms and on six pigs. RESULTS. The system collected the tracking data within 40 msec; an additional 10-20 msec was then required to perform the localization and velocity calculations and to update the image parameters. The system could localize a motionless catheter in the aorta in 100% and a moving catheter in 98% of measured attempts. The system responded in real time to changes in device velocity by dynamically adjusting spatial resolution and FOV in both phantom and porcine trials. Using this technique, we successfully catheterized the renal artery in two pigs. CONCLUSION. Active tracking, combined with automatic scanning plane and imaging parameter adjustment, provides an intuitive MRI scanner interface for the guidance of the vascular procedure.