Doctor Ulrich Hagn from the
German Center for Aerospace ;
Doctor Ulrich Hagn of the German Center for Aerospace ”Institute of Robotics and Mechatronics/Department of Robotic Systems“(DLR) in Wessling researches towards the realization of this vision. MiroSurge has already brought the institute a great deal closer to this goal.
COMPAMED.de: Doctor Hagn, how are robots being used in medical science and what exactly is MiroSurge able to do?
Ulrich Hagn: Robots are being used in different application areas in medical science and surgery. You can operate these robots either by remote control, manually or autonomously; they can resemble a tripod or can be movable to operate instruments for example. However, our goal here at the DLR was to research robotic components; this meaning robotic arms and control modules that can be assembled in a modular kit. MiroSurge is one of these set-ups intended to be used for minimally invasive surgery that’s remote-controlled. Remote-controlled however does not mean that a surgeon is located in another country or hospital. This is how it works: if you want to perform minimally invasive surgery, you only make a very small incision. The surgeon is therefore not able to reach the surgical area particularly well. That’s why you use minimally invasive instruments and place them “into the hands“ of the robot, while the surgeon sits at an input console and controls the instruments from there.
Compared to classic – meaning hand-assisted – laparoscopic surgery you also don’t have the issue of motion reversal. During classic surgery, if you want to shift the instrument tip to the left in the video picture for example, you need to steer the hand grip on the console to the right since laparoscopic instruments don’t have a wrist. But in robotics we have the advantage of being able to use instruments that feature such wrists – thereby gaining greater mobility and flexibility. Through the robot, the surgeons can remote control instruments where motion reversal is cancelled. That is to say, if the surgeon at the input console steers to the left, then the instrument tip is also moving to the left. You need to imagine that the hand movement is being transferred one-to-one to the movement of the instrument tip.
COMPAMED.de: How do you achieve the ability to convey a realistic haptic feeling to the physician at the control levers?
Hagn: Very small, miniaturized force sensors are integrated in the instrument tips, which measure all interactive forces of the instrument in the surrounding tissue. These small electrical sensors that create signals when, for example the instrument impacts tissue, measure exactly how strongly you affect the tissue. This measurement is fed back to the surgeon’s input console in which motors are installed. Thanks to these motors we can dispense forces and virtually return them back to the hands of the surgeon.
Micro-robotic arms flanged at the operating table. Right picture: Close-up view; © DLR
MiroSurge input station for the surgeon; © DLR
COMPAMED.de: So if the surgeon cuts something, he feels that he transects tissue?
Hagn: That’s correct. Let’s take some tissue of the liver with tumors for example – due to their tissue characteristics tumors are stiffer than normal liver tissue. In normal open surgery, a surgeon palpates the tissue with his/her finger and feels where there is any hardening. With MiroSurge we can scan the tissue with a special test rod and measure where there is tissue hardening. But the surgeon is not only able to feel the hardening at his input console – we can also graphically chart the hardening, for example as a map. You should envision it this way: you have tissue that is being scanned piece by piece like on a grid. This way you create a map of the stiffness of the tissue and can see precisely which areas exhibit hardening.
COMPAMED.de: How does MiroSurge differ from similar systems?
Hagn: In essence there is only one similar system on the market today – the da Vinci surgical system. Technologically, we differ very much from this system. Basically we work on a robotic platform. This means that we build a modular kit and depending on the application and request, you can configure the different system characteristics. For instance, you can determine if you would like to work with three or four robotic arms. You don’t have to design a new system for this, but instead you can add a fourth or fifth arm to the operating table. This modularity is a very important subject for us. That said, the da Vinci surgical system is already a commercially available system, whereas MiroSurge to date is only a research project.
The interview was conducted by Simone Ernst and translated by Elena O'Meara.