A new study by BGU researchers improves our understanding of the perceptual effects and distortions in haptic information during Minimally Invasive Surgery (MIS) and reveals key differences in perceptual and motor strategies employed by experts.
The study is a collaboration between Dr. Ilana Nisky (BGU), Department of Biomedical Engineering, Dr. Felix Huang (Rehabilitation Institute of Chicago - RIC), Amit Milstein (BGU), Prof. Carla Pugh (Northwestern University), Prof. Sandro Mussa-Ivaldi (RIC), and Dr. Amir Karniel (BGU), and will be presented at the next MMVR19/NextMed conference that will take place February 9-11, 2012 in Newport Beach, California. Nisky is currently a post-doctoral research fellow at Stanford after receiving her B.Sc., M.Sc. and Ph.D. from BGU.
In laparoscopy, a form of MIS, the surgeon operates with elongated instruments through a small incision in the abdominal wall of the patient. Reduced blood loss, pain, complications, and hospitalization time, and improved cosmesis are just examples of the vast advantages of MIS over traditional open surgery. However, when surgeons perform surgical maneuvers through the laparoscope, they face various challenges due to the “fulcrum effect” of the mechanical constraint at the incision point. These challenges include inversion and scaling of movements and forces (similar to what happens when children use a seesaw at a playground). Researchers have studied extensively how the fulcrum effect changes the motion of surgeons, but haptic perception through the laparoscopic device has not received as much attention.
“Haptic perception is the scientific name of everything that is related to the sense of touch and includes the sensation of forces as well as textures, humidity, temperature etc. In our study, we focused on forces, and explored the effect of the fulcrum on the perception of the stiffness of tissue. To systematically study this effect, we connected a mechanical simulator – a box with a hole through which a mockup of a surgical instrument was inserted, to a haptic device – a robotic system that can apply forces as a function of its position. The participants interacted with virtual tissues that were rendered using this device, and were asked to compare between pairs of different tissues and answer which felt stiffer. Based on their answers in different experimental conditions, we extracted the bias in perception due to the fulcrum,” Nisky explained.
Two groups of participants performed the experiment: novices – students from BGU, and haptic experts – students from the Computational Motor Control Laboratory at BGU, who work regularly with haptic devices.
“We found that the perception of stiffness of novices was biased by the scaling of movement and the reciprocal scaling of forces due to the fulcrum. Interestingly, the haptic experts were affected by this bias to a much smaller extent,” Nisky said.
These findings could aid in the development of training techniques for future surgeons and could contribute to improving surgical outcomes.