3D Ultrasound System Calibration using Stylus

Three-dimensional ultrasonic scanning has recently being applied to aid clinical procedures because of its ability to extract information from within the body harmlessly. One way of achieving this is to attach markers to the ultra-sound's probe, enabling simultaneous recording of its position and images. This system must be calibrated before it can be used. This work presents a procedure to calibrate it using a stylus similar to the Cambridge design, in conjunction with a Vicon motion capture system and a device to synchronize the data. The ultrasound images are recorded with a video capture system and software running on a PC, while another PC records the positional information of the ultrasound sensor and the stylus markers. An algorithm is applied to extract the position of the stylus from within each image, then an optimization procedure is performed to match the position of the stylus from the spatial data and the ultrasound images to generate a model of the probe in the Vicon system. Results indicate a mean error of 1.45 mm and a standard deviation of 0.91 mm. Errors in each coordinate are also analyzed, revealing mean values below 1 mm. These findings demonstrate the precision and suitability of the approach for clinical applications. However, further improvements are necessary to reduce maximum errors.