Image-guided cardiovascular interventions, like stent-supported angioplasty, are currently performed using x-ray fluoroscopy. Though x-ray fluoroscopy has enabled these procedures to be executed safely and successfully, MRI may provide additional valuable capabilities. These additional capabilities allow the interventionalist to inspect structures in the vessel wall and surrounding tissue during the procedure, instead of being limited to information about the size of the vessel lumen. This may be critical when assessing the vulnerability of atherosclerotic plaque.
Since MRI is capable of imaging an arbitrarily positioned slice or volume, it is necessary to make continual adjustments to ensure that the current image is positioned so that it includes the important anatomy and/or catheter tip. Similarly, the multitude of adjustable MR parameters that control image properties like tissue contrast, spatial resolution, and temporal resolution also need to be updated intra-procedurally.
This research addresses these aforementioned challenges. A real-time catheter tracking system has been developed and coupled with rapid imaging techniques to allow the image position to be automatically updated so that it follows the catheter as it is advanced through the vasculature. Additionally, a novel adaptive imaging system has been created to control various MR parameters during the intervention. This adaptive imaging system continually monitors variables like the catheter’s insertion speed and reacts by automatically adjusting specified image parameters.
To evaluate this interventional technology a porcine disease model of renal stenosis was created. Stent-supported renal angioplasty was then performed in six pigs using real-time imaging, active catheter tracking, and the adaptive imaging parameter system. In all experimental trials, the intervention was a technical success. The stents were deployed with an accuracy of 0.98±0.69mm.
Elements of the catheter tracking system have also been used to enable augmented reality (AR) surgical systems to compensate for the motion of abdominal organs due to respiration. These systems are employed so pre-operative medical imaging can guide a percutaneous intervention (e.g. biopsy) when intra-operative imaging is not available or impractical. The catheter tracking technology, along with a mathematical technique called principal component analysis, allows the AR system to predict the location of internal anatomical targets with an accuracy of 1.8mm.