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.

最近，虚拟现实（VR）技术通过允许临床医生在执行实际程序之前练习其技能，从而开始在基于外科模拟的培训中获得发展势头。这种模拟器的设计通常集中在要教导的主要操作任务上，但是很少注意用户需要执行的次要任务，例如在操纵外科器械时改变他/她的观点。更具体地说，尚不清楚如何为这些任务设计适当的交互技术，以及这些交互的逼真度如何影响用户在此类系统上的性能。在本文中，我们比较了在半浸入式VR（SIVR）活检教练中将针插入过程中具有两种不同级别的交互逼真度的两种视点改变技术。这些技术是根据观察临床医生进行实际活检程序而设计的。第一种技术是基于跟踪用户的头部位置（高交互保真度），而第二种技术是基于触摸的，用户利用他/她的非惯用手指来操纵触摸屏上的视点（适度交互）保真）。进行了一项用户研究，以调查在针头插入任务（主要任务）过程中，视点更改任务（次要任务）的交互保真度对用户性能的影响。21名新手参与者被要求在使用导航技术（受试者内部设计）的情况下对针头插入任务进行几次试验。记录客观和主观测量以比较任务绩效（完成任务的时间，这两种技术的精确度，错误率和用户体验）。结果表明，与头部跟踪技术相比，基于触摸的视点改变技术提高了用户在针插入过程中的任务完成性能，同时保持了相似的针操作精度水平。这些结果表明，在设计手术训练员时，并非总是需要高交互保真度。这也凸显了为次要任务设计适当的交互的重要性，因为它们会影响用户在VR模拟器中的主要任务性能。结果表明，与头部跟踪技术相比，基于触摸的视点改变技术提高了用户在针插入过程中的任务完成性能，同时保持了相似的针操作精度水平。这些结果表明，在设计手术训练员时，并非总是需要高交互保真度。这也凸显了为次要任务设计适当的交互的重要性，因为它们会影响用户在VR模拟器中的主要任务性能。结果表明，与头部跟踪技术相比，基于触摸的视点改变技术提高了用户在针插入过程中的任务完成性能，同时保持了相似的针操作精度水平。这些结果表明，在设计手术训练员时，并非总是需要高交互保真度。这也凸显了为次要任务设计适当的交互的重要性，因为它们会影响用户在VR模拟器中的主要任务性能。