Usability and Performance : Comparative Evaluation of Surgeon Interfaces in Laser Phonomicrosurgery

State-of-the-art Laser Phonomicrosurgery (LP) is a set of complex otolaryngological surgical techniques used in the treatment of laryngeal abnormalities, including cysts and tumors. The complexity of this surgical procedure influences its own outcome because of its peculiar issues: (i) the surgical site access can be difficult, (ii) the setting can cause surgeon discomfort, (iii) the outcome quality is totally dependent on the skills of the surgeon and is prone to errors, (iv) the operation methods require extensive training, and (v) the equipment characteristics themselves affect all the previous aspects [8]. The importance of the role of robot-assisted surgical systems is increasing in the operating room [7]. They provide significant advantages in effectiveness, efficiency and safety of surgery through, for instance, increased task precision, reduced tremor in gestures, and timely execution of repetitive tasks. Nevertheless, such recent advances still require an ergonomic approach for a user-centered design and evaluation of surgeonmachine interfaces [12]. The cognitive limits of human beings can become critical factors in excessive mental workload (the amount of cognitive resources used to accomplish a task) [10] and in human error [11]. Thus, human factor-oriented approach is required in user interface design and evaluation to increase both safety (for the surgeon and the patient) and performance of the system. It permits the analysis of the issues of user interface design in terms of human-machine interaction constructs like usability (a complex set of behavioural concepts, like execution time, user satisfaction and ease of learning, [1]) and the objective performance of the user (according to quantitative data automated collection, [4]). Such constructs are considered in this paper for the comparison of 2 user interfaces for LP, in the context of the European project μRALP. At the Istituto Italiano di Tecnologia (IIT), this research has already resulted in new and improved computer-assisted LP systems. Mattos et al. [8] presented a novel surgeon interface, the Virtual Scalpel system, which replaces the traditional manual micromanipulator interface [6] with a motorized micromanipulator, controlled through a graphics stylus and a touch-screen tablet with live video of the surgical area. The immediate advantage offered by the new interface is that both the aiming and the activation of the laser are controlled by the graphics stylus. The analysis of this novel solution indicated that this system offers greater precision along with better ergonomics over the traditional laser micromanipulator [3], [8], [9]. Through a series of field trials involving a sample of potential users, the new Virtual Scalpel laser control interface [8] was compared with the AcuBlade [6], the traditional, state-of-the-art laser control interface with the manual micromanipulator for LP. This study defines the perceived usability of each interface and the performance of the users in surgery-like tasks. The subjective evaluation of the usability of the interface has been measured by means of questionnaires, and the objective evaluation of the performance of the interface by means of an imaging-based feature extraction method [4].