Hands-free Adjustment of the Microscope in Microneurosurgery

In microneurosurgery, the operating microscope plays a vital role. The classical neurosurgical operation is bimanual, that is, the microsurgical instruments are operated with both hands. Often, operations have to be carried out in narrow corridors at the depth of several centimeters. With current technology, the operator must manually adjust the field of view during surgery-which poses a disruption in the operating flow. Until now, technical adjuncts existed in the form of a mouthpiece to move the stereo camera unit or voice commands and foot pedals to control other interaction tasks like optical configuration. However, these have not been widely adopted due to usability issues. This study tests 2 novel hands-free interaction concepts based on head positioning and gaze tracking as an attempt to reduce the disruption during microneurosurgery and increase the efficiency of the user.

Technical equipment included the Pentero 900 microscope (Carl Zeiss Microscopy GmbH, Jena, Germany), HTC Vive Pro (HTC, Taoyuan District (HQ), Taiwan), and an inbuilt 3D-printed target probe. Eleven neurosurgeons including 7 residents and 4 consultants participated in the study. The tasks created for this study were with the intention to mimic real microneurosurgical tasks to maintain applicative accuracy while testing the interaction concepts. The tasks involved visualization system adjustment to the specific target and touching the target. The first trial was conducted in a virtual reality setting applying the novel hands-free interaction concepts, and the second trial was conducted performing the same tasks on a 3D-printed target probe using manual field of view adjustment. The participants completed both trials with the same predetermined tasks, in order to validate the feasibility of the novel technology. The data collected for this study were obtained with the help of review protocols, detailed post-trial interviews, video and audio recordings, along with time measurements while performing the tasks.

The user study conducted at the Charité Hospital in Berlin found that the gaze-tracking and head-positioning- based microscope adjustment were 18% and 29% faster, respectively, than the classical bimanual adjustment of the microscope. Focused user interviews showed the users' proclivity for the new interaction concepts, as they offered minimal disruption between the simultaneous target selection and camera position adjustment.

The hands-free interaction concepts presented in this study demonstrated a more efficient execution of the microneurosurgical tasks than the classical manual microscope and were assessed to be more preferable by both residents and consultant neurosurgeons.