Interventional cardiovascular magnetic resonance imaging: a new opportunity for image-guided interventions

Abstract

Cardiovascular magnetic resonance (CMR) combines excellent soft-tissue contrast, multiplanar views, and dynamic imaging of cardiac function without ionizing radiation exposure. Interventional cardiovascular magnetic resonance (iCMR) leverages these features to enhance conventional interventional procedures or to enable novel ones. Although still awaiting clinical deployment, this young field has tremendous potential. We survey promising clinical applications for iCMR. Next, we discuss the technologies that allow CMR-guided interventions and, finally, what still needs to be done to bring them to the clinic.

Figure 1. CMR-Guided Transapical Aortic Valve Replacement

(A) Bioprosthesis mounted on a platinum iridium stent with a stainless-steel marker welded on the side of the stent between the commissures. (B) The marker is visible as a dark signal in the cardiovascular magnetic resonance (CMR) and indicates the orientation of the prosthesis. Short-axis view and long-axis view of the implanted prosthesis in a pig under real-time CMR are shown in C and D, respectively. Blue dots are digital markers indicating the coronary ostia whereas the yellow dot shows aortic annulus location. (E) Three-dimensional rendering snapshots show multiple image planes displayed at their relative 3-dimensional position. Images courtesy of Ming Li, PhD, and Keith A. Horvath, MD, Cardiothoracic Surgery Research Program, National Heart, Lung, and Blood Institute.

Figure 2. Electrophysiological Cardiac Mapping Under Real-Time CMR Guidance

(Top) Roadmap-based real-time 3-dimensional visualization of the catheter position during recording (red dot) on the magnetic resonance-electrophysiological workstation. The yellow dots in the 3-dimensional rendering of the heart indicate previous mapping positions. (Bottom) In-bore electrophysiological recordings at 2 selected positions showing an atrial signal (left) and a ventricular signal (right). Graphic courtesy of Steffen Weiss, PhD, Philips Healthcare.

Figure 3. X-Ray Fused With MRI

Representative X-ray fused with magnetic resonance imaging (MRI) display with contours from cardiovascular magnetic resonance (CMR) overlaid on live X-ray. Aorta (red), right ventricle (yellow), left endocardial (blue), and epicardial (green) surfaces from CMR shown in 3 dimensions with aortic annulus and ventricular septal defect locations outlined in blue and red, respectively. Multimodality external fiducial markers also are seen numbered.

Figure 4. Interventional CMR Suite

An interventional cardiovascular magnetic resonance (CMR) suite showing adjacent and interoperable magnetic resonance imaging scanner and X-ray angiography labs. A docking gurney allows rapid intermodality transfer. Courtesy of Alexander J. Dick, MD, Sunnybrook Health Sciences Centre, Toronto.

Figure 5. Real-Time Cardiac MR

Multiplanar real-time cardiac imaging at 4 to 5 frames/s (A) with pre-acquired static cardiac magnetic resonance (MR) image (B) and pulmonary vessel 3-dimensional MR angiography (C) roadmaps.

Figure 6. Real-Time MRI User Interface Showing MR-Guided Delivery and Biopsy of Encapsulated Human Islet Cells in a Pig

Example of a real-time magnetic resonance imaging (MRI) user interface from Siemens. Similar interfaces are available for Philips and GE systems. Features include scan plane manipulation, independent device channel coloring, 3-dimensional viewing window, static image roadmaps, and quick access to select slice orientations. Figure courtesy of Christine H. Lorenz, PhD, Siemens Corporate Research, Inc., and Aravind Arepally, MD, Johns Hopkins Medical Institutions, Baltimore, Maryland.

Figure 7. Interventional CMR Devices

Three representative approaches to catheters designed to be tracked using cardiovascular magnetic resonance (CMR). (A) Passive nonbraided balloon catheter filled with CO₂ in a right atrium. (B) Active tracking catheter in the right heart. Image courtesy of Michael Bock, PhD, German Cancer Research Center (DKFZ), Heidelberg, Germany. (C) Two-channel active guidewire in the aorta approaching the left heart.

Figure 8. Iliac Artery Navigation Using a Passive Guidewire

(Top) Polymer guidewire with a Nitinol tip. (Bottom) Magnetic resonance-guided probing of the contralateral iliac artery with the guide-wire (arrows) and a catheter. Susceptibility artifacts in cardiovascular magnetic resonance (CMR) images arise from the iron doped guide-wire, which is also visible under fluoroscopy. These artifacts partially obscure the target tissue. Images courtesy of Gabriele A. Krombach, MD, Department of Diagnostic Radiology, University Hospital Aachen, Aachen, Germany.