Article

Magnetic Resonance Imaging-guided Vascular Interventions

Cardiovascular Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA.
Topics in Magnetic Resonance Imaging 11/2005; 16(5):369-81. DOI: 10.1097/00002142-200510000-00004
Source: PubMed

ABSTRACT Magnetic resonance imaging (MRI), which provides superior soft-tissue imaging and no known harmful effects, has the potential as an alternative modality to guide various medical interventions. This review will focus on MR-guided endovascular interventions and present its current state and future outlook. In the first technical part, enabling technologies such as developments in fast imaging, catheter devices, and visualization techniques are examined. This is followed by a clinical survey that includes proof-of-concept procedures in animals and initial experience in human subjects. In preclinical experiments, MRI has already proven to be valuable. For example, MRI has been used to guide and track targeted cell delivery into or around myocardial infarctions, to guide atrial septal puncture, and to guide the connection of portal and systemic venous circulations. Several investigational MR-guided procedures have already been reported in patients, such as MR-guided cardiac catheterization, invasive imaging of peripheral artery atheromata, selective intraarterial MR angiography, and preliminary angioplasty and stent placement. In addition, MR-assisted transjugular intrahepatic portosystemic shunt procedures in patients have been shown in a novel hybrid double-doughnut x-ray/MRI system. Numerous additional investigational human MR-guided endovascular procedures are now underway in several medical centers around the world. There are also significant hurdles: availability of clinical-grade devices, device-related safety issues, challenges to patient monitoring, and acoustic noise during imaging. The potential of endovascular interventional MRI is great because as a single modality, it combines 3-dimensional anatomic imaging, device localization, hemodynamics, tissue composition, and function.

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Available from: Cengizhan Öztürk, Nov 16, 2014
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    • "Clinical-grade interventional catheter devices for use during MR, such as catheters and guidewires, remain the most significant obstacle to wider clinical translation. Current non-clinical implementations tend to offer reduced visibility under MR or excessive size and reduced mechanical performance [15,16]. "
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    ABSTRACT: Background Catheter visualization and tracking remains a challenge in interventional MR. Active guidewires can be made conspicuous in "profile" along their whole shaft exploiting metallic core wire and hypotube components that are intrinsic to their mechanical performance. Polymer-based catheters, on the other hand, offer no conductive medium to carry radio frequency waves. We developed a new "active" catheter design for interventional MR with mechanical performance resembling braided X-ray devices. Our 75 cm long hybrid catheter shaft incorporates a wire lattice in a polymer matrix, and contains three distal loop coils in a flexible and torquable 7Fr device. We explored the impact of braid material designs on radiofrequency and mechanical performance. Results The incorporation of copper wire into in a superelastic nitinol braided loopless antenna allowed good visualization of the whole shaft (70 cm) in vitro and in vivo in swine during real-time MR with 1.5 T scanner. Additional distal tip coils enhanced tip visibility. Increasing the copper:nitinol ratio in braiding configurations improved flexibility at the expense of torquability. We found a 16-wire braid of 1:1 copper:nitinol to have the optimum balance of mechanical (trackability, flexibility, torquability) and antenna (signal attenuation) properties. With this configuration, the temperature increase remained less than 2°C during real-time MR within 10 cm horizontal from the isocenter. The design was conspicuous in vitro and in vivo. Conclusion We have engineered a new loopless antenna configuration that imparts interventional MR catheters with satisfactory mechanical and imaging characteristics. This compact loopless antenna design can be generalized to visualize the whole shaft of any general-purpose polymer catheter to perform safe interventional procedures.
    Journal of Cardiovascular Magnetic Resonance 08/2009; 11(1):1-10. DOI:10.1186/1532-429X-11-29 · 5.11 Impact Factor
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    • "However, in dynamic studies, where the device is moving within the field of view, it may be possible to remove such artifacts with image subtraction (Buecker et al 2000). Finally, all passive device visualization methods suffer from reduced temporal resolution since multiple images must be acquired to locate and track the device in 3D space, a task that is less cumbersome with active approaches (Ozturk et al 2005). However, whether this perceived limitation severely hampers imageguided intervention remains to be investigated. "
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    ABSTRACT: The use of off-resonance methods in interventional MRI may be valuable since active devices that provide positive signal enhancements are currently not approved for human use. This study investigated the capacity of a low flip angle steady-state free precession (FLAPS) method for generating off-resonance positive contrast surrounding a susceptibility-shifted endomyocardial Stiletto catheter in excised swine hearts and in live swine. Consistent with theory, discernable positive contrast surrounding the interventional device was visualized under ex-vivo (CNR of 24 +/- 2.1 in the left ventricular (LV) chamber and 18 +/- 2.7 in LV myocardium) and in-vivo conditions (CNR of 22 +/- 3.9 in aorta, 16 +/- 4.1 in the LV chamber and 13 +/- 0.9 in LV myocardium). The findings show that off-resonance imaging with the FLAPS method may be used for passive device visualization with positive contrast. Further studies are necessary prior to clinical translation.
    Physics in Medicine and Biology 08/2008; 53(13):N249-57. DOI:10.1088/0031-9155/53/13/N02 · 2.92 Impact Factor
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    ABSTRACT: This study presents a system designed to assist the surgeon during interventional procedures performed by Magnetic Resonance Imaging (MRI). In order to reach the target during guidance in a double obliquity trajectory, this system provides accurate information about both the entry point and the orientation of the needle.
    Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2007; 2007:2748-51. DOI:10.1109/IEMBS.2007.4352897
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