The use of the focus of expansion for automated steering of flexible endoscopes

Colon cancer screening remains a time-consuming and expensive clinical process. Automating flexible endoscopy has the potential to increase screening efficiency. In this research the images captured by the camera at the endoscope tip are used to find the heading direction of the endoscope. Comparing the current heading direction to the desired target direction in a computer algorithm is expected to allow automated steering of the endoscope. Heading direction determination is achieved using an estimation of the focus of expansion (FOE) from the optical flow field. The resulting heading direction is compared to results obtained manually by several human observers. From our experiments it becomes clear that the FOE can be used as a reliable estimator for heading direction in human colonoscopy images. Additionally, the automated results have an intraclass correlation of 89% with the manual results, demonstrating that the algorithm works as expected. It is anticipated that the final steering algorithm can be used in a variety of motorized flexible endoscope applications.