Even though solid tumors often look like the healthy tissue they’re invading, they almost always present as fibrous densities, hence surgeons use their fingers to feel for a difference in stiffness during extraction. Canadian researchers from the University of Western Ontario and Canadian Surgical Technologies and Advanced Robotics at the London Health Sciences Center have adapted a robot to identify the change in stiffness as it traverses a surface, hoping to develop this technology for cancer detection or diagnosis. So far, in lab experiments, the instrument has displayed considerably greater precision than humans at detecting the stiffness gradient.
With cows’ livers standing in for human tissue and 10mm and 5mm blobs of glue wrapped in wire representing tumours, the researchers compared palpation by surgeons, non-surgeons and the robot in the blinded trials. The researchers used a torque sensor to measure the force of the palpations.
Using tactile MIS sensing instruments under robotic control reduces the maximum force applied to the tissue by over 35% compared to a human controlling the same instrument. Accuracy in detecting the tumours was also far greater with the robot – between 59 and 90% depending on the robot control method used for palpation.
Unlike humans, the robot applies consistent force in each step, and moves over the tissue systematically. This produces a complete map, equivalent to one large pad applying ideal levels of force to the whole sample. (Similar to tactile sensors that have been developed to detect breast tumours.)
Humans do not know from one palpation to the next exactly how much force they are applying. This means some features are only highlighted because the surgeon is applying more force, or because the human user has changed the angle slightly between the instrument and the tissue. It is also easier to miss a tumour due to applying slightly lower force.
In fact both surgeons and non-surgeons were more likely to cause tissue damage than the robot. When a subject observed increased pressure on the visual display, they tended to focus on the area and apply even more force to see if what they had observed was a tumour. In the case of MIS, only a very small area can be palpated, which makes it challenging to compare adjacent areas and search for a tumour manually.
Press release: Robot’s gentle touch aids delicate cancer surgery …
Article in The International Journal of Robotics Research: Robot-assisted Tactile Sensing for Minimally Invasive Tumor Localization
