How does the camera assistant decide the zooming ratio of laparoscopic images? Analysis and implementation.

An important factor for defining a good image during laparoscopic surgery is the zooming ratio, which corresponds to the depth of insertion of the laparoscope along its longitudinal axis. However, it is not clear how surgeons (camera assistants) decide the zooming ratio of laparoscopic images during surgery. Conventional automatic camera positioning systems define the zooming ratio "uniformly" based on simple heuristics. However, because the most adequate zooming ratio varies widely during surgery, these conventional systems may not offer the specific view that the surgeon wants. Therefore, we first investigated how the camera assistant decides the zooming ratio of laparoscopic images by fully analyzing the positional relationship between the laparoscope and the surgical instrument during laparoscopic surgery. Then, we extracted the zooming behavior and implemented it in the robotic laparoscope positioner that we previously developed. As a result, the zooming behavior of our robotic system became very similar to that of the human camera assistant. It was found that the proposed zooming motion of our robotic system may be suitable for fast and compact operations during surgery.