Real-time catheter-directed MRA with effective background suppression and persistent rendering

Purpose: To develop an imaging and visualization technique for real-time magnetic resonance angiography (rt-MRA) fully integrated with a real-time interactive imaging environment on a clinical MR scanner. Materials and Methods: Intraarterial injections of contrast agent and imaging processing techniques were employed for rapid catheter-directed assessment of vessel patency and regional tissue perfusion, Operators can image multiple thin slices to maximize anatomic detail or use thick slice or projection imaging to maximize vessel coverage. Techniques in both pulse sequence and image processing were employed to ensure background suppression. Accumulation of maximum pixel values allows persistent display of bolus signal as it passes through the vessels and into tissues. Automatic brightness adjustment was used to ensure visibility at all stages of bolus passage. Results: Experimental intraarterial rtMRA of coronary, renal, and carotid arteries show that vessel trajectories and perfusion territories are well visualized in swine. Switching between standard real-time imaging and rtMRA imaging after contrast injection was easy to perform during a procedure without stopping the scanner. Conclusion: The proposed technique facilitates visualization of intraarterial contrast injections using real-time MRI. Although designed for rapid deployment during rtMRI-guided interventional procedures, the technique may also be useful to supplement the study of vessel anatomy, flow, or perfusion.