Raitt, Duncan Guthrie; (2024) Soft, compliance-controllable sensing for tissue stiffness characterisation. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Surgeons’ performances are reduced when working with robotic surgical systems due to not having any haptic feedback. In open surgery surgeons use their sense of touch to work in obscured areas, assess tissue health, and locate edges of stiff tumours. Over time, more surgeries are utilising robotic minimally invasive surgical systems. These systems reduce patient recovery time compared to open surgery. Additionally they are easier to learn and having greater dexterity than laparoscopy. However, there is no direct connection between the surgeon and their tools, preventing them from receiving haptic feedback. Literature shows that surgeons using robotic surgical systems are more likely to leave cancer behind, which may then require further treatments. To address this issue, this thesis produces a soft tipped sensor which can quantify tissue stiffness and locate boundaries during dynamic palpation, suitable for use in robotic surgery. This was done by developing a sensor which interacts using a compliance controllable membrane which is tracked using a camera. Firstly, it is shown that sensors which function through this method can measure forces with an adjustable range. The sensor can measure normal forces using a 4th-order polynomial fit and measure the angle and magnitude of non-normal forces using a neural network. The range of the sensor could be adjusted by changing its internal pressure. Secondly, these sensors were shown to be able to measure stiffness and locate boundaries when mounted on a linear rail or teleoperated. The sensor was integrated into a teleoperated system with haptic feedback. Participants could identify the angle of stiff embedded objects using this system. Finally, it was demonstrated that a robotic surgery compatible sensor with a diameter under 12 mm could be produced using this method. This sensor was able to measure forces with an adjustable range, quantify stiffness and locate boundaries during palpation.

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