With the many recent advances in technology and robotics, the world of medicine is gradually moving towards a more machine-based approach. Robotic surgery, or robot assisted surgery, is one of the developments that is at the forefront of this shift. Robotic surgery involves the use of surgical robots that can be controlled by doctors through computers. Why is robotic surgery becoming more popular among surgeons? The robot does not have to deal with shaky hands or other forms of human error, so their cuts are smaller and their movement is more precise. This results in less pain and blood loss for the patient, and quicker healing time.1 Even higher accuracy can be achieved when computer-generated images are used to guide surgeries. One such possibility is the use of a real time MRI scan to guide surgeries. However, the MRI machine is too small to have the traditional large robots inside it. In addition, since most robots are made of metal, they are unsafe to place inside the MRI, which uses a very strong magnetic field to conduct its imaging.2
Fortunately, there has been a recent development made at the Worcester Polytechnic Institute that opens up the door for robots to be used in MRI. The research team at the Automation and Interventional Medicine Robotics lab led by Dr. Gregory Fischer at WPI developed a small, non-metallic robot that can perform surgeries inside an MRI.2
The motor of the robot controls its movement. To make the motor non-metallic, the researchers first attempted to use pneumatic actuators to control the robot’s movement. Pneumatic actuators typically use compressed air as energy for mechanical movement. However, this did not give them the accuracy that they wanted, due to “jitter and overshoot” from air pressure.3 Instead, they decided to use a motor made of piezoelectric material. An electric charge can accumulate in piezoelectric materials when mechanical stress is applied to them. There are many non-metallic materials that have piezoelectric properties, so the research team used these instead of metal for the motor.4 The rest of the robot’s body is made out of plastic, small enough to fit inside an MRI.1
Currently, it is undergoing clinical trials at Brigham and Women’s Hospital in Boston. Prostate biopsies with the robot have been performed on about a dozen men so far, and all of them have been more accurate than a typical biopsy.2 In a normal prostate biopsy, it is difficult for the doctor to see exactly where the lesion or target tissue is. However, with an MRI, doctors can see suspicious areas in the prostate, which they can target accurately with the robot. In these clinical trials, however, the robot itself does not insert the needle into the patient. It instead positions the needle at the surface of the skin and tells the doctor how deep the target area is. Then, the doctor inserts the needle and takes the sample. Fischer states that in lab tests, the robot can autonomously “locate the target, track the needle, and if it deflects during insertion, it can steer the needle to hit the target.” This part of the robot needs to be worked on more until it is ready for clinical testing.2
The development of small MRI-compatible surgical robots has significant future implications in the future of robotic surgery. This principle can be used in other procedures in which accuracy is limited by what the doctor can see. With the ability to use piezoelectric material and plastic to make non-metal robots, many doors open up for robotic MRI-compatible surgeries. New robots can be made with piezoelectric material and plastic instead of metal, and different types of small robots can be made for different types of surgeries.
Lavan Rajan is a sophomore from Martel College at Rice University.
Liou, L.S. Robotic Surgery. Medicine Plus. http://www.nlm.nih.gov/medlineplus/ency/article/007339.htm (accessed July 16, 2015)
Fischer, G.; Harrington, K.; Camilo, A.; Tokuda, J.; Tempany, C.M.; Hata, N. Piezoelectrically Actuated Robotic System for MRI-Guided Prostate Percutaneous Therapy. Institute of Electrical and Electronics Engineers. 2014. 1-12.
Inside an MRI, a Non-Metallic Robot Performs Prostate Surgery. IEEE Spectrum. http://spectrum.ieee.org/automaton/robotics/medical-robots/inside-an-mri-a-nonmetallic-robot-performs-prostate-surgery (accessed July 16, 2015)
The Piezoelectric Effect. Nanomotion. http://www.nanomotion.com/piezo-ceramic-motor-technology/piezoelectric-effect/. (accessed July 16, 2015)