Developing Force-Feedback Technology for Robot Assisted Surgeries

The Journal of Robotic Surgery, launched last month, heralds a new age in the use of robotic techniques to aid in surgery. While robotic surgery offers benefits over traditional surgery, the technology still lags in a few areas. When surgeons cut tissue with robot arms, for example, they can't feel the resistance and cannot judge the amount of pressure being applied. A team of haptics researchers from Johns Hopkins' University (JHU) hopes to solve this problem.

This is where Allison M. Okamura comes in. An associate professor of mechanical engineering and director of Johns Hopkins' Haptics Exploration Laboratory, Okamura has made it her mission to figure out how to infuse robots with a human-like sensitivity to touch — and to help robot-assisted surgeons like Yuh practice safer medicine.

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Okamura built Hopkins' haptics lab from scratch. Shortly after arriving here, she wanted to work on medical robotics but, she says, "I had no idea how to get started." Mentors from the ERC taught her how best to write grant proposals and integrate work on robotics with researchers from other disciplines. She apprenticed for two years under a host of Hopkins engineers. After a pair of cardiac surgeons — Yuh, and Vincent Gott, a since-retired professor of surgery — approached her in 2001 with their concerns about breaking fine sutures while performing delicate surgery, Okamura and crew were off and running.

Earlier research at JHU demonstrated that a lack of tactile feedback in robotic systems led to errors by experienced cardiac surgeons.

Clinical successes with robot-assisted minimally invasive cardiac surgery have lagged behind those achieved with robot-assisted laparoscopic general surgery due, in large part, to the lack of feedback. This deficiency with current robotic systems is a significant handicap in performing the technically more intricate and delicate surgical tasks inherent in cardiac surgery. For example, suturing a coronary arterial anastomosis with fine polypropylene suture is a highly dexterous task, in which the surgeon typically uses his or her sense of touch to puncture tissue with a fine needle, pull the suture through, and tie and tighten knots. In our own observations of experienced and talented cardiac surgeons training with the da Vinci surgical system, fine polypropylene sutures are often broken, and delicate tissues torn, due to the application of excessive forces conventionally attenuated with haptic feedback. The consequences of such surgical errors or delays in cardiac surgery (e.g., coronary microvascular or great vessel trauma, prolonged cardiopulmonary bypass) present much greater potentials for irreversible injury, excessive hemorrhage, or even death for the patient.

Providing a visual substitute for tactile feedback improved their success rate.

Our results demonstrate significantly greater and more consistent tensions applied to suture materials, without breakage, during robotic knot tying enhanced with haptic feedback compared to knots tied without feedback. During the execution of these experiments, several interesting observations were noted. Surgeons broke the finer polypropylene sutures on several occasions both with and without sensory substitution. Interestingly, surgeons were able to partially compensate for the lack of haptic feedback by visually observing the deformation of tissue when the knot was pulled away from the tissue. We also noted that different users employed different tying techniques; some surgeons used equal force with both hands, while others favored increased control with one hand.

In this preliminary study, we have shown that haptic feedback, in the form of a visual color bar scale, permits surgeons to be more consistent, precise, and apply significantly greater tensions to fine sutures without breakage during robotic knot tying. Our visual sensory substitution aid represents an initial step towards providing surgeons with tactile feedback during robotic surgery. This early work with computer-enhanced robotic-assisted cardiac surgery represents the field in its infancy.

The JHU team believes that the integration of haptics, more commonly known as force feedback, will lead to a broader adoption of robotic surgery.

More Than a Feeling [Johns Hopkins University]