Intracoronary MR imaging using a 0.014-inch MR imaging-guidewire: Toward MRI-guided coronary interventions

Purpose: To validate the feasibility of using a newly designed MR imaging-guidewire (MRIG) to guide angioplasty balloon placement in coronary arteries. Materials and Methods: A custom gold/sliver/Nitinol/MP35N-based, 0.014-inch MRIG was manufactured. To test its mechanical performance we used the new MRIG to catheterize the left coronary arteries of three dogs under x-ray fluoroscopy. To further validate the feasibility of using the MRIG to generate intracoronary MR imaging, we positioned the MRIG, along with a dilation-perfusion balloon catheter, into the left coronary arteries of an additional three dogs. Longitudinal and four-chamber views of cine cardiac MR images were obtained using a fast gradient recalled echo (FGRE) sequence (TR/TE/FA = 5.2 msec/1.6 msec/20°, field of view [FOV] = 32 x 32 cm, thickness = 5 mm, space = 2 mm, matrix = 256 x 160, number of excites [NEX] = 0.5, and bandwidth [BW] = 32 kHz). Then three-dimensional (3D) MR coronary angiography of the left coronary arteries was obtained using a last imaging employing steady-state acquisition (FIESTA) sequence. We subsequently used the MRIG, at a receive-only mode, to generate intracoronary MR images using FGRE (TR/TE/FA = 7.2 msec/3.5 msec/20°, FOV = 18 x 18cm, thickness = 3 mm, space = 0.5 mm, matrix = 256 x 256, NEX = 0.5, and BW = 32 kHz). Results: In all six animals the left main coronary arteries were successfully catheterized. 3D MR imaging displayed left coronary artery branches. Intracoronary MR imaging demonstrated the inflated balloons as a "train track" or a bright, thick ring at different views. Conclusion: This study demonstrates the potential of using this newly designed gold/silver/Nitinol/MP35N-based, 0.014-inch MRIG to catheterize coronary arteries and, thus, generate intracoronary MR imaging with balloon inflation.