A New Approach to Establish Tactility in Minimally Invasive Robotic Surgery Development, Design, and First Evaluation of a Haptic-Tactile Feedback System for Improved Localization of Arteries During Surgery such as Closed-Chest Revascularization

In conventional minimally invasive robotic surgery (MIRS) the physician is no longer in direct mechanical contact with the patient and the surgical instruments. The establishment of kinesthetic impressions shows promising results technically but tactile feedback is still a problem. Various attempts with full remote perception of tactile impressions did not prevail for a number of reasons. Above all, the tactile feedback actor commonly is a secondary device which hinders simultaneous perception of feedback signals and guidance of instruments. Human perception of tactile impressions, however, often is a result of active palpation which is hard to emulate in two separate devices; so far, interpretation of feedback signals was not sufficiently clear and intuitive. One of the most serious problems resulting from the absence of tactile feedback in minimally invasive (robotic) surgery is the augmented risk of an unintended blunt artery dissection causing bleeding which would be difficult to control. In open surgery, tissue can be palpated and a pulsating perception indicates a hidden artery. In open cardiac surgery preoperatively planned bypass anastomoses positions can be found by palpation. Using optical examination only, a dissection of the arteries, which is very time consuming, may become necessary to locate the correct positions. The solution presented in this dissertation does not provide full remote tactile perception, but focuses on the quasi-tactile detection of special structures under covering tissue using ultrasound. The acquired signals are subjected to a modality substitution and presented to the user as an intuitive haptic or multi channel signal. For this purpose, an ultrasound transducer embedded in a minimally invasive surgical instrument is used to acquire Doppler frequency shifts of blood flow in the vessels to be detected. The acquired signals are analyzed and transferred to a haptic feedback device. Here, the detection and characteristics of a covered vessel is presented in an intuitive way. A slight twitch of the feedback device accompanied by the characteristic Doppler shift sound are, based on the results of first experiments, expected to be very reliable and intuitive and effectively replace palpation. Further investigations to prove the validity and deepen the understanding of this hypothesis are pending. It is highly questionable whether full feedback of all possible tactile impressions in MIRS is worth striving for – the medical benefit does not appear to justify the efforts and cost. Therefore, the substitution of only selected components of full tactility, comparable to the human perception, such as carried out in this dissertation promises to be a better solution. In contrast to realizations described in literature that have not prevailed in practical application the system described here has passed first tests and demonstrated its superior performance. A patent was granted on April 5th, 2007.