Design and control of a teleoperated palpation device for minimally invasive thoracic surgery

Minimally invasive surgery (MIS) consists in operating through small incisions in which a camera and adapted instruments are inserted. It allows to perform many interventions with reduced trauma for the patient. One of these is the ablation of peripheral pulmonary nodules.Nevertheless, the means for detecting nodules during MIS are limited. In fact, because of the lack of direct contact, the surgeon cannot palpate the lung to find invisible lesions, as he would do in classical open surgery. As a result, only clearly visible nodules can be treated by MIS presently.This work aims at designing, building and controlling a teleoperated palpation instrument, in order to extend the possibilities of MIS in the thoracic field. Such an instrument is made of a master device, manipulated by an operator, and a slave device which is in contact with the patient and reproduces the task imposed by the master. Adequate control laws between these two parts allow to restore the operator's haptic sensation. The goal is not to build a marketable prototype, but to establish a proof of concept.The palpation device has been designed in collaboration with thoracic surgeons on the basis of the study of the medical gesture. The specifications have been deduced through experiments with experiencied surgeons from the Erasmus Hospital and the Charleroi Civil Hospital.A pantograph has been built to be used as the master of the palpation tool. The slave is made of a 2 degrees of freedom (dof) clamp, which can be actuated in compression and shear. The compression corresponds to vertical moves of the pantograph, and the shear to horizontal ones. Force sensors have been designed within this project to measure the efforts along these directions, both at the master and the slave side, in order to implement advanced force-feedback control laws and for validation purposes.Teleoperation control laws providing a suitable kinesthetic force feedback for lung palpation have been designed and validated through simulations. These simulations have been realized using a realistic model of lung, validated by experienced surgeons. Among the implemented control schemes, the 3-Channel scheme, including a local force control loop at the master side, is the most efficient for lung palpation. Moreover, the increased efficiency of a 2 dof device with respect to a 1 dof tool has been confirmed. Indeed, a characteristic force profile due to the motion in 2 directions appeared in the compression force tracking, making the lesion easier to locate.