Single-loop coil concepts for intravascular magnetic resonance imaging

Abstract

Compared with other coil designs that have been investigated for intravascular use, the single‐loop coil can be designed with a very small diameter for insertion into small vessels and with a longitudinal extent over several centimeters for multislice imaging. If it designed to be expandable inside the target vessel, then it combines these features with increased signal‐to‐noise ratio (SNR) and penetration depth. Expandable single‐loop coils that are capable of meeting these requirements were developed and integrated into two different commercial catheter‐based delivery systems: a self‐expandable, single‐loop made from NiTinol and a single‐loop coil mounted on an inflatable balloon. The influence of a small‐diameter coaxial cable for remote tuning and matching on the coil performance was investigated. Calculations showed the dependence of the signal on the separation between the conductors. The comparison of both catheter approaches in in vitro flow experiments and in an in vivo pig experiment revealed the influence of pulsatile flow on image quality during intravascular imaging with these designs. Magn Reson Med 41:751–758, 1999. © 1999 Wiley‐Liss, Inc.

MR imaging of the vessel wall

“…For in vivo use, features such as the suppression of flow artefacts, a small diameter of the receiver coil system and a non-rigid, flexible catheter-based design for easy insertion into small vessels have to be considered essential prerequisites [53]. With these prerequisites in mind, single-loop catheter coils with self-expanding loops made from Nitinol were developed for intravenous [54] as well as for intraarterial use (Fig.…”

“…With these prerequisites in mind, single-loop catheter coils with self-expanding loops made from Nitinol were developed for intravenous [54] as well as for intraarterial use (Fig. 8a) [53]. During delivery, the loop is compressed within a sheath and upon release allowed to expand.…”

“…The EKG triggering, gradient moment nulling and saturation bands cannot compensate adequately for these artefacts (Fig. 8b) [53]. An alternative is to mount a single-loop coil inside a conventional percutaneous transluminal angioplasty balloon catheter (Fig.…”

Interventional MRA and intravascular imaging

“…Unfortunately, even though the loop adheres to the artery wall, such devices are still subject to flow and pulsation-related artifacts since the vessel wall itself is moving and deforming over time. Electrocardiographic (ECG) trigger- ing, gradient moment nulling, and saturation bands cannot compensate adequately for these artifacts (53,60) (Fig. 6c).…”

“…The outstanding resolution of the intravascular images might be used to characterize various plaque components, thereby providing guidance for choice of the optimal therapeutic strategy to pursue (60,61,63,64). While intravascular ultrasound can currently be used to characterize plaques, the advantages of MR imaging lie in its superior soft tissue contrast, its ability to see behind calcified plaques and the struts of intravascular stents, and the ease with which tomographic or 3D data with a known relation to other anatomic landmarks can be generated.…”