One-step needle pose estimation for ultrasound guided biopsies.

A pose estimation method is proposed for measuring the position and orientation of a needle. The technique is to be used as a touchless needle guide system for guidance of percutaneous procedures with 4D ultrasound. A pair of uncalibrated, light-weight USB cameras is used as inputs. A database is prepared offline, from the needle line estimated from camera-captured images and from the true needle line recorded from an independent tracking device. A non-parametric learning algorithm determines the best fit model from the database. This model can then be used in real-time to estimate the true position of the needle with inputs from only the camera images. Simulation results confirm the feasibility of the method and show how a small, accurately made database can provide satisfactory results. In a series of tests with cameras, we achieved an average error of 2.4mm in position and 2.61 degrees in orientation. A study of the results shows that the overall accuracy of the method is affected by the system designed to make the database.