MRI-guided endovascular intervention: current methods and future potential

Abstract

Introduction: Image-guided endovascular interventions, performed using the insertion and navigation of catheters through the vasculature, have been increasing in number over the years, as minimally invasive procedures continue to replace invasive surgical procedures. Such endovascular interventions are almost exclusively performed under x-ray fluoroscopy, which has the best spatial and temporal resolution of all clinical imaging modalities. Magnetic resonance imaging (MRI) offers unique advantages and could be an attractive alternative to conventional x-ray guidance, but also brings with it distinctive challenges.

Areas covered: In this review, the benefits and limitations of MRI-guided endovascular interventions are addressed, systems and devices for guiding such interventions are summarized, and clinical applications are discussed.

Expert opinion: MRI-guided endovascular interventions are still relatively new to the interventional radiology field, since significant technical hurdles remain to justify significant costs and demonstrate safety, design, and robustness. Clinical applications of MRI-guided interventions are promising but their full potential may not be realized until proper tools designed to function in the MRI environment are available. Translational research and further preclinical studies are needed before MRI-guided interventions will be practical in a clinical interventional setting.

Keywords: MRI safety; MRI-guided; endovascular intervention; interventional MRI; interventional radiology; minimally invasive surgery; real-time MRI; robot-assisted.

Figure 1.

Current interventional MRI suites often combine with other imaging modalities. a) The Brigham and Women’s Hospital’s AMIGO Suite combines a PET/CT, x-ray fluoroscopy table, and a 3.0T (image from https://ncigt.org/amigo), b) Rendering of Zuckerberg San Francisco General Hospital’s AMR Suite Magnetom Skyra 3.0T MRI and Artis Q biplane angiographic system (image courtesy of Siemens Healthcare GmbH).

Figure 2.

MRI-guided iliac artery stent placement using Dy-doped catheters. a) Visualization of Dy markers (arrows) along the nonmetallic wire. b) The catheter-mounted ZA stent (arrows) positioned in the aorta c) The stent withdrawn to the position of deployment, and d,e) Stent deployment in real-time. f) Fully deployed stent (arrows) is shown [49]. Dy = Dysprosium

Figure 3.

Wireless resonant marker tracking in vivo at 3.0T. Markers placed in the right (dashed arrow) and left (solid arrow) carotid arteries of a single swine are shown in a coronal scan plane under a) MRI and b) x-ray, which are more easily seen under c) magnification (left artery with contrast, and the right artery without contrast). d) A sagittal B1+ map quantifies signal amplification. Low background signal and high marker signal amplification was demonstrated at a flip angle of e) 5°. Surrounding tissue signal becomes higher and over-flipping near the marker are shown as the flip angle increases to f) 10° and g) 45° [74].

Figure 4.

Passive marker tracking sequences. Visualization of three paramagnetic markers with a) a conventional gradient echo sequence (slice 30 mm, TE/TR = 4.6/60 ms, duration 22 sec) and b) dephased positive contrast gradient echo imaging (white marker sequence with 1.9 cycles of phase across the slice) with similar acquisition parameters. In vivo application of white marker tracking with significant obscuring of the makers for conventional c) unsubtracted and d) subtracted tracking. White marker tracking permits easy detection of the markers for both e) unsubtracted and f) subtracted positive contrast tracking [93].