Sarthak Misra is building the surgeon of the future
A robot doctor in your body
Removing prostate glands, repairing cardiac valves, excising tumours in the head and neck: Da Vinci does it all, in hospitals all over the world. That’s because he’s not a person, but a robotic system that can perform procedures while the actual surgeon sits behind a console and operates it remotely.
‘Robots are very useful to make surgery less invasive’, says Sarthak Misra, professor of medical robotics at the UMCG. Because they can be very precisely controlled, you minimise the risk of damaging healthy tissue. So it’s no surprise that they are increasingly utilised during different types of procedures.
Da Vinci is the most widely used example of a medical robot and it’s a sizable machine. In his laboratory, Misra works on these kinds of large-scale systems, but also on much smaller robots: ‘We try to develop novel techniques to reach challenging locations in the body. And we think micro-robots are the way to get there.’
He wants to go beyond machines you move remotely with a console or a joystick: ‘We aim to make flexible robots that can move wirelessly and adapt autonomously in a dynamic environment.’ And that’s challenging, he explains, because navigating through the human body comes with a lot of uncertainties. ‘We need to plan for this, so that the procedure can be performed accurately and safely.’
For now, it’s still science fiction, but I believe it is possible
Making a well-thought-out pre-operative plan is a first step for these kinds of medical robots. Misra: ‘You have to map the route they take as well as the action that the robot needs to take when it gets to its destination or target, such as taking a biopsy or releasing a drug.’
This map is made with the help of imaging techniques, like computed tomography (CT), magnetic resonance imaging (known either as MR or MRI), or ultrasounds. ‘All these images are fed into a computer model that can predict the best path the robot should take.’
The next step is to actually do the procedure. ‘You have to get the robot inside the body and use data from the sensors and real-time images to track it, and use this information to control the robot. If there are unexpected encounters, it needs to adapt its course. And when the robot gets to the end, it has to perform the action.’
Unfortunately, this second step is much harder to execute, and Misra admits that it is not yet possible: ‘This is where we want to go, but for now it’s still science fiction. But I believe it is possible, and we’ve already managed to make some parts of this dream a reality.’
One example of this is the robot that he and his colleagues developed for the diagnosis and treatment of prostate cancer. Instead of being operated on, some patients are treated with localised radiation: radioactive seeds are placed in the prostate, says Misra. That has to be done very precisely – the prostate is the size of a walnut – and doctors often use ultrasound images to do it.
You want to have accurate knowledge of where the robot is, otherwise you can’t use it
‘To make this process more accurate, you need high resolution MR images, so we developed a robot that’s compatible with the MR scanner. The robot is put in place while the patient is in the scanner, and it can deliver the radioactive seeds with the doctor guiding the robot or performing the procedure autonomously.’
Another robot that came from his lab can be inserted into the lungs to take a biopsy of small lesions that traditional biopsy needles cannot reach. ‘We’ve developed a robotically steered flexible needle system for this, so you can navigate without damaging healthy tissue and reach the target site accurately’, Misra says. ‘It kind of moves like a snake within the body, and can also be adapted to help guide catheters when doctors perform cardiac procedures.’
All these examples are quite far along on the road to actual clinical applications. They are now in various stages of testing on human cadavers and animals. Misra hopes that they make it to the clinical trials, where they will be tested on live humans, but they do still run into lots of different issues: ‘The main problem is how to see what is going on deep inside the body, so you can keep track of the robot. You want to have accurate knowledge of where it is, otherwise you can’t use it. But we are working on new sensors and imaging techniques to solve this.’
Another major issue: how do you get the micro-robots to move? You can’t power it with a battery, so researchers are working on other ways, for instance by harvesting energy from within the body. Misra takes another approach: ‘We use magnetic fields and sound waves to wirelessly propel the robots, because it is something that can penetrate tissue and won’t hurt the patient.’
A magnetic field was also the key to one of Misra’s widely publicised robots: magnetosperm. ‘Here we put a magnetic head on a silicon tail, and the magnetic field makes the micro-robot sway like sperm cells and swim forward. We’re now investigating further miniaturising of these robots and using them for drug delivery.’
Magnetosperm moves forward by swaying like sperm cells do
So there are lots of small victories, but the hardest challenge might be to put all those inventions together. ‘I can make something that moves, but it also needs to be biocompatible so the body doesn’t reject it, and it needs to actually perform the task’, Misra says. ‘I can’t do that alone, so we work together with people from different disciplines like chemistry, material science and of course clinicians.’
The challenge of this task also forces them to be creative and to keep coming up with new ideas. ‘We’ve developed so many different robots by now: big and small ones, snake-like robots, a squid robot that can eject air bubbles. The possibilities seem endless.’
With all these developments and new discoveries, Misra does believe that in the future, robotics will be ubiquitous in the operating room. ‘The use of medical robots will be widely accepted by both clinicians and patients. As we move forward, I foresee a future where soft biocompatible miniaturised robots can move and perform complex surgeries in the body. It will take time, but we will get there.’