Comparing touch-based and head-tracking navigation techniques in a virtual reality biopsy simulator

Abstract

Recently, virtual reality (VR) technologies started gaining momentum in surgical simulation-based training by allowing clinicians to practice their skills before performing real procedures. The design of such simulators is usually focused on the primary operative tasks to be taught, but little attention is paid to secondary tasks that the user needs to perform, such as changing his/her point of view when manipulating the surgical instruments. More particularly, it is not clear how to design appropriate interaction techniques for those tasks, and how the fidelity of these interactions can impact the user’s performance on such systems. In this paper, we compare two viewpoint changing techniques having two different levels of interaction fidelity during needle insertion in a semi-immersive VR (SIVR) biopsy trainer. These techniques were designed based on observing clinicians performing actual biopsy procedures. The first technique is based on tracking the user’s head position (high interaction fidelity), while the second technique is touch-based with the user utilizing his/her non-dominant hand fingers to manipulate the point of view on a touch screen (moderate interaction fidelity). A user study was carried out to investigate the impact of the interaction fidelity of the viewpoint changing task (secondary task) on the user’s performance during the needle insertion task (main task). Twenty-one novice participants were asked to perform several trials of a needle insertion task while using the navigation techniques (within-subject design). Objective and subjective measures were recorded to compare the task performance (time to accomplish the task, precision of the tumor sampling, and errors) and user experience for both techniques. The results show that the touch-based viewpoint changing technique improves the users’ task completion performance during needle insertion while maintaining a similar level of needle manipulation accuracy as compared to the head-tracking technique. These results suggest that high interaction fidelity is not always necessary when designing surgical trainers. This also highlights the importance of designing appropriate interactions for secondary tasks because they can influence the user’s primary task performance in VR simulators.