The use of localizers, robots and synergistic devices in CAS

There are many roles for electromechanical devices in image guided surgery. One is to help a surgeon accurately follow a preoperative plan. Devices for this purpose may be localizers, robots, or recently, synergistic systems in which surgeon and mechanism physically share control of the surgical tool. This paper discusses available technologies, and some emerging technologies, for guiding a surgical tool. Characteristics of each technology are discussed, and related to the needs which arise in surgical procedures. Three different approaches to synergistic systems, under study by the authors (PADyC, ACROBOT, and Cobots), are highlighted. An electromechanical device of some sort is needed in image-guided surgery, in order to connect the "information world" of images, plans, and computers, to the physical world of surgeons, patients, and tools. That is the situation in which a surgical plan has been created based on diagnostic images, and it is the job of the surgical system to guide the surgeon in the accurate execution of his own preoperative plan. The surgeon is again in direct contact with the surgical tool, but an interface device must also be connected to that tool, so that the computer may in some way provide guidance. Thought of as human interfaces, the perceptual quality of such a device is often the most prominent factor in the performance of surgical systems. We appreciate a quality that is sometimes called transparency - the quality of being perceptually absent. One purpose of this paper to describe the measures of interface device performance which determine their suitability for use in various surgical situations. We give examples of surgical situations that particularly depend on one or another of these measures. Another purpose is to describe several classes of interface devices, with examples. Previous descriptions of such devices relied on a decomposition in passive, active and semi-active systems (1) in which the degree of passivity was often associated with a type of technology. We prefer to define a new classification based on function rather than mechanism including localizers, robots, and also a new class which we call synergistic devices. Synergistic devices are intended for direct physical guidance of a surgical tool which is also held and controlled directly by a surgeon. Each of the authors is pursuing a different approach to synergistic devices, and these approaches are outlined. The paper concludes with a discussion of the applicability of the technologies to various surgical purposes.