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Catheter Visualization with Resonant Markers at MR Imaging–guided Deployment of Endovascular Stents in Swine¹

¹ From the Departments of Congenital Heart Disease and Pediatric Cardiology, German Heart Institute, Augustenburger Platz 1, Berlin 13037, Germany (T.K., S.Y., B.S., P.E., P.L.); Philips Research Laboratories, Hamburg, Germany (S.W.); Department of Pediatric Cardiology, University Hospital Eppendorf, Hamburg, Germany (F.B., J.W.); and Department of Diagnostic Radiology and Nuclear Medicine, Charité, Humboldt University, Berlin, Germany (M.G.). Received October 28, 2003; revision requested January 16, 2004; revision received March 11; accepted April 1. Supported in part by the German Bundesministerium für Bildung und Forschung and the Deutsche Forschungsgemeinschaft. Address correspondence to T.K. (e-mail: titus.kuehne@dhzb.de).

View larger version (68K): [in a new window]   Figure 1. SDS with RCs (arrows) positioned at the distal and proximal ends of the loaded stent.

View larger version (67K): [in a new window]   Figure 2. MR images acquired with interactive steady-state free precession (2.9/1.6; flip angle, 45°; section thickness, 8 mm; acquisition frame rate, 8 per second; field of view, 280 mm; matrix, 128 x 128) show SDS with RCs in saline bath. Note the intense signal of the RCs before (left) and after (right) delivery of the nitinol stent.

View larger version (126K): [in a new window]   Figure 3. Parasagittal interactive steady-state free precession (2.9/1.6; flip angle, 5°; section thickness, 8 mm; acquisition frame rate, 8 per second; field of view, 280 mm; matrix, 128 x 128) MR images of the thoracic aorta, carotid artery, and SDS with single RCs show good contrast between SI of RCs and SI of background anatomy achieved with flip angle of 5°. A, Advancement of the SDS through the aortic arch. B, SDS in the carotid artery immediately before stent delivery. C, Release of the nitinol stent accompanied by detuning of the distal RC (arrow). D, Retraction of the SDS into the descending aorta.

View larger version (162K): [in a new window]   Figure 4. Parasagittal interactive steady-state free precession (2.9/1.6; flip angle, 45°; section thickness, 8 mm; acquisition frame rate, 8 per second; field of view, 280 mm; matrix, 128 x 128) MR image of the thoracic aorta and SDS with single RCs (arrows).

View larger version (50K): [in a new window]   Figure 5. Bar graph shows in vivo SI measurements with two different flip angles over 4 pixels at the sites of single RCs and paired decoupled RCs and in blood within the vessel near the RC. Only SI of the blood pool (*) decreased significantly when the flip angle was changed from 45° to 5° (P < .001). No significant difference was found between SI measurements with the SDS lumen containing saline solution alone, saline solution and a nitinol guidewire, or saline solution and a polyester guidewire.

View larger version (65K): [in a new window]   Figure 6. Transverse interactive steady-state free precession (2.9/1.6; flip angle, 45°; section thickness, 8 mm; acquisition frame rate, 8 per second; field of view, 280 mm; matrix, 128 x 128) MR images of the inferior vena cava and SDS with paired decoupled RCs (arrows) show that SI of the RCs remained comparable in three different conditions: with the working lumen of the SDS filled with saline solution (A); with a 0.035-inch polyester guidewire advanced through the saline solution-filled lumen (B); and with a 0.035-inch nitinol guidewire inserted in the saline solution-filled lumen (C). Because the nitinol guidewire acts as an antenna, SI in the SDS is increased on C.

View larger version (174K): [in a new window]   Figure 7. Transverse balanced FFE (2.7/1.4; flip angle, 50°; section thickness, 8 mm; field of view, 260 mm; matrix, 256 x 256) MR image shows decreased SI in the lumen of a nitinol stent placed in the aorta (right arrow), compared with SI in the adjacent vena cava (left arrow).

View larger version (100K): [in a new window]   Figure 8. Contrast-enhanced MR angiograms (5.2/1.6; flip angle, 35°; section thickness, 1.6 mm; field of view, 380 mm; matrix, 512 x 512) before (left) and after (right) stent placement in the carotid artery (arrows).