Surgeons can hardly perform manually complex tasks under ultrasound (US) imaging. Visual servoing appears as a possible solution to assist the surgeon in such an operation. The idea of the proposed system is to allow the surgeon to select a desired position on a US image and then program a robot to automatically move the instrument towards the location indicated by the surgeon. This approach requires robust tracking of the instrument in the US image, modeling of the overall system and implementation of a visual servoing loop. This paper presents geometrical and kinematic models of the system, as well as the control loop design, which is validated through both numerical simulations, and results of in vitro experiments.
The comanipulation paradigm, in which a user and a robot simultaneously hold a tool, allows for gesture guidance. In particular, virtual fixtures, which are geometrical constraints imposed to the tool by the robot, have received a great interest in the domain of surgical applications. So far, this concept has been implemented in the context of open surgery. This paper explores the application of virtual fixtures for minimally invasive surgery, where the tool is inserted in the patient through a fulcrum. Here, a key issue is to return to the surgeon forces that are virtually applied at the instrument distal tip, while the robot is physically attached to the instrument proximal handle. To this aim, two approaches are investigated. A first approach consists in applying a full wrench at the proximal end of the instrument that is equal to the wrench constituted by a pure force applied to the instrument's distal tip. A second approach consists in applying a pure force to the instrument proximal end, thanks to a lever model about the fulcrum. The two approaches are compared through experiments during which naive subjects blindly perform virtual object palpation and robot guided movements. During experiments, indicators involving motion and force analysis are computed. The user capacity to distinguish between several virtual objects is evaluated as well. Although drastically different, the two approaches provide assistance with a similar level of efficiency.
Minimally invasive surgery (MIS) challenges the surgeon's skills due to his separation from the operation area which can be reached with long instruments only. Therefore, the surgeon loses access to the manipulation forces inside the patient. This reduces his dexterity when performing the operation. A new compact and lightweight robot for MIS is presented which allows for the measurement of manipulation forces. The main advantage of this concept is that no miniaturized force sensor has to be integrated into surgical instruments and inserted into the patient. Rather, a standard sensor is attached to a modified trocar outside the patient, which allows for the measurement of manipulation forces. This approach reduces costs and sterilizability demands. Results of first force control experiments are presented to show the feasibility of the concepts.
Abstract-This paper presents a robust visual servoing approach for automatic guidance of an instrument. The visual sensor is an ultrasound probe that observes an instrument which is inserted into the beating heart of a patient and manipulated by a robot. The present paper provides stability analysis, robustification of the control law and an in vivo experiment.
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