A nonlinear averaging method to optimize the accuracy of optical tracking

摘要

In image-guided surgery, it is essential to be able to track the positions of instruments in physical space and relate these positions to preoperative or intraoperative images. The most common way of tracking the instruments is using optical tracking; a camera containing two charge-coupled devices (CCDs) calculates the three-dimensional position of infra-red light emitting diodes (IREDs), and uses this information to deduce the position and orientation of the instrument. Because the IREDs cannot be localized perfectly, the calculated pose of the instrument, and hence the overlay of the instrument on the image, undergoes continual small changes even when the instrument is stationary. This leads to the user interface of the image guidance system displaying rapid small movements of the probe; we call this phenomenon "jitter". Severe jitter can make the image guidance system difficult and bothersome to use and may reduce system accuracy. In this paper, we examine a novel method of overcoming the jitter problem. This method performs a nonlinear average of historical tracking information collected over a given time period. We show the disadvantages of a simpler linear averaging technique; we also use a phantom of known geometry to examine the overall effect that averaging has on system accuracy.