<title>Modeling the internal and external constraints of a flexible endoscope for calculating its workspace: application in transbronchial needle aspiration guidance</title>

Abstract

In robotics, the term workspace denotes that volume of space which the end-effector of a robot can reach. Similarly we denote the workspace of a flexible endoscope as the volume of space that can be occupied by the entire endoscope. From the endoscope's perspective, the workspace is determined by its internal (mechanical) constraints, as well by its external constraints, like organ geometry and gravity. In this paper we show how to calculate the workspace of a given endoscope under insertion into a patient specific organ model. We propose a model of an endoscope that takes the internal constraints into account. We also propose an algorithm which simulates the insertion of an endoscope into an organ. This algorithm calculates the workspace by recursively building a spatial tree whose growth is constrained by a series of filter functions. As Kukuk et al. showed, knowing a real endoscope's workspace can be used to significantly increase the success rate of a blind biopsy. We have built an experimental setup (lung phantom) that allows us to assess the accuracy of our model by comparing it to a real endoscope.