A Novel Catheter Tracking Method Using Reversed Polarization

INTRODUCTION: Accurate visualization of guidewires and catheters during a vascular intervention(1,2) procedure is critically important. With this aim, many tracking techniques have been developed. Automatic identification of the position of the catheter in passive tracking techniques(3) is difficult, but in active catheter tracking techniques(1,2,4), it is possible to obtain a catheter and background image simultaneously. However, the catheters need to be electrically connected to the scanner and this causes both RF safety problems and creates difficulties in device handling. Recently, Quick et.al.proposed wireless active catheter visualization(4) by using an inductively coupled RF (ICRF) coil; this can be classified as an intermediate method between active and passive techniques. The design is a good compromise that reduces the heating problems and decreases the handling issues. However, as in the passive tracking techniques, it is impossible to see both catheter and background images simultaneously. In our study, we propose a novel technique for catheter tracking using an inductively coupled RF coil that enables simultaneous acquisition of background and catheter images thus allowing real-time, color-coded display of the RF coil on the background image. Reverse circular polarization is used to obtain an image of ICRF. We also demonstrated the feasibility of the proposed method with an in-vivo animal experiment. THEORY: Polarization is a description of how the direction of the magnetic field vector changes with time at a fixed point in space. Assuming phasor representation of –z directed