3D localizer for ultrasound endoscope by an outside-body marker

In this paper, we describe a method which we can identify 3D position and direction of ultrasound scanning probe inserted into inside of the body, which gives endoscopic images. We use marker transducers placed on surface of the body, which transmit pulses synchronized to the ultrasound scanner. The method of measuring position (direction and distance between scanning probe inside of body and transducer outside of body) of marker on the scanned image obtained with ultrasound endoscope by using adaptive threshold and robust algorithm is described. This system can be extended to for body-inside navigation by localizing body-outside transducers and visualizing the position and trace of the body-inside ultrasound probe. The final goal of the system is to reduce the x-ray dose in the endoscopic examination and to give direct 3D localization instead of the conventional 2D x-ray fluoroscopy.