Interview with D. Engr. Bernhard Kübler, Research Assistant, Institute of Robotics and Mechatronics, DLR- German Aerospace Center, Weßling
Minimally invasive surgeries are gentler on the patient but have one distinct disadvantage for the surgeon: he is not able to interact directly with the operating field. Sometimes he misses impressions that are very important to the success of the intervention. The MiroSurge robot for surgical applications which transmits feedback to the surgeon can help.
In this interview with MEDICA.de, Dr. Bernhard Kübler talks about the origins of MiroSurge in aerospace technology, how immersion can assist surgeons during the intervention and how the system was already received during last year's MEDICA EDUCATION CONFERENCE.
Dr. Kübler, findings from aerospace technology were applied during the development of the MiroSurge surgical robotic system. What played a role in this?
D. Engr. Bernhard Kübler: When astronauts have to step out during a "spacewalk" to work on the outside of a spacecraft, it is expensive and also dangerous for the astronaut. In these cases, it is great when you have a universal device on the outer shell that can complete certain tasks remotely. This is a telemanipulated task. The necessary technology is comparable to a medical scenario where somebody also controls a device across a spatial barrier.
This is why we saw the chance to expand into new areas of application. The technology that was originally intended for tasks in space can also be used in the surgical field, especially during minimally-invasive robotic surgery. The concept is similar: tools are operated via special input devices and manipulate something across a spatial barrier, in this case, the patient’s abdominal wall for example. The technologies are related but not entirely identical. However, technologies that were originally developed for space are thus transferred into the OR.
What would a possible usage scenario for MiroSurge actually look like?
Kübler: We call the individual arm "Miro" which is derived from minimally invasive, robot-assisted surgery. Two of these arms carry instruments with which we facilitate a bimanual manipulation in the patient. That means you operate one instrument each with your right and left hand by remote control. A third Miro carries the camera that transmits stereoscopic pictures. The surgeon is supposed to feel as if he is "right at the site". We call this the telepresence experience; the surgeon is supposed to forget all the technology around him and the distance to the patient through a high degree of immersion. When he imagines himself in the scenario and believes his hands are right at the actual location, things are ideal.
You already said it, you should feel like you are right there at the site. The instruments have sensors on the tip. What exactly do these sensors measure?
Kübler: We develop a variety of sensors. The sensor technology is crucial for haptic and kinesthetic feedback to be more accurate. We want to measure the surrounding interaction forces and moments. Whenever the instrument touches the patient, we want to pass the contact forces and torque of the device through the hand controller and represent the surgeon there. The surgeon then no longer just sees the tissue deformation on the monitor to estimate the interaction force, but feels the counteracting force at the input device.
A grip force sensor is added to this. The surgeon needs to know how much force he applies when he grips the tissue to avoid tissue damages by exerting too much force. The next step pertains to mere tactility, meaning the sense of touch. In open surgery, the physician uses his own fingertips to palpate the tissue. However, the past has shown that the sensitivity of human fingertips is very difficult to technically simulate in terms of force, heat and friction. Yet in surgery it is very important to feel vessels during the surgical procedure for example. The classic force sensors are not able to measure this properly.
That said, you can detect blood vessels with ultrasound very nicely. This is why we have developed an ultrasonic sensor that lets you detect regardless in which direction the blood vessel faces. The surgeons feel the located vessel through a small pressure pulse at the input device.
Is it not incredibly complex for the user to sense and interpret all of this?
Kübler: Actually not. Of course, you need a certain time to familiarize yourself with the device but you should not have to read a manual to be able to use the robot. The hand controllers are meant to be as intuitive and immersive as possible. The surgeon slips inside them with each hand and controls the input device like a joystick where he also feels the respective counteracting forces. The feedback of the ultrasonic sensor is subsequently self-explanatory: the stronger the twitching is, the stronger the detected pulsation is and the associated risk of injury to vessels. If needed, the surgeon then should have the option of accessing additional information about the vessel. This can be very smart at that moment during surgery without resulting in a sensory overload for the surgeon. This also eliminates the risk of the surgeon losing track because he receives too much information.
MiroSurge is also designed to provide assistance during open surgery. Why do surgeons need this when they are at the operating table?
Kübler: These can be typical one-arm applications. Wounds need to constantly be held open during surgery which is an exhausting task for the resident physician or prospective surgeon. The surgeon can pass this task on to a Miro which subsequently keeps the wound open by applying constant pressure that can be adjusted.
Precise cuts in bone surgery are another option. You can bring the robot into position beforehand. It then performs this brief, simple task with high precision for the surgeon.
You already introduced the MiroSurge at last year's MEDICA EDUCATION CONFERENCE. What type of feedback did you receive for the device?
Kübler: This was the first time we were able to introduce the system on such a platform. Initially, we were overwhelmed at how many actual interested parties there were. We received very interesting questions from the audience. Those are always interesting for a researcher and broaden your horizon. That is why we were very satisfied and look forward to participating this year.
Do you anticipate certain future trends in the field of medical robotics?
Kübler: For the most part, the skills of human beings are maxed out in many surgical disciplines. The human physiognomy limits the technical skills of a surgeon so to speak. The dimensions certain areas like eye or brain surgery already work in are in some cases already smaller than the natural tremor, meaning the naturally occurring tremble of a person. Technical support systems are required in this case to make another quantum leap. Exactly how this can be realized needs to be seen in and by working together with the individual disciplines. MiroSurge can only be one example of this. The actual design is something that also needs to be accomplished in joint collaborations with the field of surgery in the future.