Browsing by Author "Karmarkar, P."
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Item Open Access Intracoronary MR imaging using a 0.014-inch MR imaging-guidewire: Toward MRI-guided coronary interventions(John Wiley & Sons, Inc., 2008) Qiu, B.; Gao, F.; Karmarkar, P.; Atalar, Ergin; Yang, X.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.Item Unknown Simultaneous radiofrequency (RF) heating and magnetic resonance (MR) thermal mapping using an intravascular MR imaging/RF heating system(John Wiley & Sons, 2005-06) Qiu, B.; El-Sharkawy, A.-M.; Paliwal, V.; Karmarkar, P.; Gao, F.; Atalar, Ergin; Yang, X.Previous studies have confirmed the possibility of using an intravascular MR imaging guidewire (MRIG) as a heating source to enhance vascular gene transfection/expression. This motivated us to develop a new intravascular system that can perform MR imaging, radiofrequncy (RF) heating, and MR temperature monitoring simultaneously in an MR scanner. To validate this concept, a series of mathematical simulations of RF power loss along a 0.032-inch MRIG and RF energy spatial distribution were performed to determine the optimum RF heating frequency. Then, an RF generator/amplifier and a filter box were built. The possibility for simultaneous RF heating and MR thermal mapping of the system was confirmed in vitro using a phantom, and the obtained thermal mapping profile was compared with the simulated RF power distribution. Subsequently, the feasibility of simultaneous RF heating and temperature monitoring was successfully validated in vivo in the aorta of living rabbits. This MR imaging/RF heating system offers a potential tool for intravascular MR-mediated, RF-enhanced vascular gene therapy.