Performance evaluation of 2D sensors for medical navigation camera systems

• Main Author: Panse, Frederik
• Format: Others
• Language: English
• Published: KTH, Skolan för teknik och hälsa (STH) 2014
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-158881

Abstract Stryker’s FP6000 is the currently most accurate medical navigation camera on the market. This high-performance system consists of three one-dimensional sensors. An evaluation is presented, that analyzes, if it is possible to design a camera based on 2D sensors, that satisfies the same accuracy as the FP6000 camera, but is designed of smaller dimensions, reduced weight and lower cost. For the LED localization a glass-substrate with a certain pattern is placed in front of the 2D sensor. Within the glass-material there are always local inhomogeneities present, that influence the measurements. One hypothesis is, that the influence of those inhomogeneities can be lowered by increasing the number of pattern elements. In this way, the accuracy of the 2D sensors may be improved up to a certain level. Furthermore, a medical navigation camera, that is designed with multiple 2D sensors, represents an overdetermined system. It is analyzed, how strongly the RMS error for a camera based on multiple 2D sensors can be decreased by exploiting the concept of system over-determination. On a test bench the influence of different pattern elements on the accuracy of various 2D sensors was evaluated. A Matlab code simulated the RMS error of a camera system, that localizes LED positions with the tested 2D sensors. In this implementation, overdetermined problems were solved through a combination of linear triangulation and bundle adjustment. The accuracy tests confirmed, that the part of the systematic error, that results from local inhomogeneities within the glass-material, could be diminished with 30 holes inside the pattern. As a result of this, the accuracy of the 2D sensors was improved. However, none of the tested sensors was accurate enough for the design of a camera of small dimensions and low cost, that localizes LED positions with the same accuracy than the FP6000.