Claudia Hillenbrand PhD, PRESENTER: Nothing to Disclose

Abstract: HTML Purpose: To develop and test a phased-array RF antenna mounted on a catheter to fulfill the 2 critical roles for MRI guided endovascular therapies: 1) MR guidance of the interventional device to the target region, and 2) high resolution vessel wall imaging at the target location. Methods and Materials: A phased-array configuration was designed and built, consisting of 2 independent solenoid coils (30 AWG wire, coil Æ 5F, 5 windings, length 4.5mm) wound in opposite direction and mounted on a catheter (gap 1cm). Each coil was individually tuned, matched and connected to a separate receive channel of a clinical 1.5T MR scanner, and could therefore be turned on/off independently during the scan, allowing for individual or combined processing of the received signals. Tracking and imaging capabilities of the coil configuration were tested in vivo in 7 pigs. Procedures were performed in accordance with approved IACUC protocols. For active device localization, a global excitation was performed, and projection signals from the scanner's 3 orthogonal axes were acquired using the coil array only. Simultaneous signal reception via the 2 independent receiver channels provided unambiguous determination of each coil position in 3D. These positions were used to calculate position and orientation of a subsequent imaging plane and execute a guidance scan (real time TrueFISP). After guiding the device to a remote site in the abdominal aorta, high resolution vessel wall images (TrueFISP, TR/TE 13/6.5ms, SL 2.5mm, resolution 240μm, TA 15sec) were acquired. Signals from both channels were combined in order to calculate images that provide an extended length of radial homogeneity between the coils. Results: During tracking, each coil produced a high amplitude peak in the projection data sets; unique peaks were observed in data sets from both RF channels. This allowed the catheter advancement and retraction to be successfully tracked. Device tracking and automated slice positioning worked very reliable and accurately. High resolution vessel wall images were acquired within less than 15sec. No artifacts compromising the appearance of the vessel wall were observed. Conclusion: The proposed catheter array proved successful for guidance and imaging phases of in vivo intravascular interventions. The independent coils could be used individually for tracking or combined for high resolution imaging, without seriously compromising coil sensitivity. Therefore, this new device simultaneously performs the two main tasks required for future MRI guided endovascular therapies.     (C.M.H. received a grant from DFG. J.S.L., J.L.D. are consultants for Siemens Medical Solutions and received grants from NIH.)

Hillenbrand PhD, C, Active Device Tracking and High-Resolution Intravascular MRI Using a Multi-Channel Catheter Coil.  Radiological Society of North America 2003 Scientific Assembly and Annual Meeting, November 30 - December 5, 2003 ,Chicago IL. http://archive.rsna.org/2003/3107399.html