Digital subtraction MR angiography roadmapping for magnetic steerable catheter tracking

Abstract

Purpose To develop a high temporal resolution MR imaging technique that could be used with magnetically assisted remote control (MARC) endovascular catheters. Materials and Methods A technique is proposed based on selective intra-arterial injections of dilute MR contrast at the beginning of a fluoroscopic MR angiography acquisition. The initial bolus of contrast is used to establish a vascular roadmap upon which MARC catheters can be tracked. The contrast to noise ratio (CNR) of the achieved roadmap was assessed in phantoms and in a swine animal model. The ability of the technique to permit navigation of activated MARC catheters through arterial branch points was evaluated. Results The roadmapping mode proved effective in phantoms for tracking objects and achieved a CNR of 35.7 between the intra- and extra-vascular space. In vivo, the intra-arterial enhancement strategy produced roadmaps with a CNR of 42.0. The artifact produced by MARC catheter activation provided signal enhancement patterns on the roadmap that experienced interventionalists could track through vascular structures. Conclusion A roadmapping approach with intra-arterial contrast-enhanced MR angiography is introduced for navigating the MARC catheter. The technique mitigates the artifact produced by the MARC catheter, greatly limits the required specific absorption rate, permits regular roadmap updates due to the low contrast agent requirements, and proved effective in the in vivo setting.