A Catheter Posture Recognition Method in Three Dimensions by Using RF Signal Computation

Minimally invasive surgery (MIS) has widely been performed at clinical sites to avoid the deficiencies of open surgery. During catheterization, which is a representative procedure, a medical device is inserted through a hole or the like to minimize the incision area. When the catheter is steered into the human body, the clinician must monitor its movement in real time. In this paper, we propose a new localization method that tracks the position and direction of the catheter with radio frequency (RF) signals. Because the catheter has a cylindrical structure, two signal-receiving coils (Rx) are attached to the end tip of the catheter and three signal-transmitting coils (Tx) are mounted on the subject’s bed for procedure compatibility. The magnetic field generated by the Tx coils was modeled with the Biot–Savart and Faraday's laws based on the overall structure. In addition, a position tracking algorithm was derived by comparing the theoretical induced electromotive force (EMF) calculated with the magnetic model and the measured signal from the receiving coil. A novel geometry calibration algorithm was developed via optimization to find the nearest set of an actual structure that can reduce geometric errors. The initial value problem of the position estimation algorithm was solved by filtering the results with a Kalman filter to minimize the error of the estimated position. Finally, the proposed method was validated with simulations and experiments. It is expected to be applicable to catheters and for similar minimally invasive medical device recognition and position tracking processes as well as advanced electromagnetic sensor technology.