In recent years, the use of computers and machines in surgery has gained widespread attention and adoption. Some of the benefits include increased accuracy, decreased duration, and minimized invasiveness. As computer hardware continues to miniaturize, the deployment of robotic surgery inside the body has become more feasible. Application domains include eye and ENT surgery, cardiac surgery, laparoscopy, and neurosurgery. The development of these internal surgical robots can be modeled across five generations of research [1].
The “zeroth” generation is laparoscopy, involving camera-aided surgery through a small incision. Although traditional laparoscopy does not involve robots, it inspired the first generation of surgical robots: stereotaxic robots. These robots compute precise positions for each step in a surgical procedure, albeit without a visual aid like in laparoscopy. The second generation involved rigid dexterous robots, such as precise robotic arms, to carry out surgery. One notable example is the “da Vinci” platform, currently run by Intuitive Surgical Inc. Then came the third generation of flexible robots, where a robot could enter the human body and navigate through vessels and orifices. Up through this point, these technologies required a physical connection to some exterior device (power supply, computer, etc.). The fourth generation is the untethered microsurgeon, a free-floating device — for example, a capsule endoscope.
Recent research on internal surgery focuses on third- and fourth-generation robots. Bruns et al. 2020 developed a tethered robot for inserting electrode arrays for cochlear implants, which are housed inside the delicate inner ear [2]. Empirical results show that manual insertions produce highly variable exerted forces, whereas their robot could alleviate much of these variations. In the automated process, the only human involvement is a button, which the surgeon holds to run a precomputed trajectory, allowing for a quick deactivation in the event of an emergency.
Heunis et al. 2020 presented the ARMM system for a specific type of robotic surgery: positioning endovascular catheters [3]. The typical procedure involves inserting a catheter in the groin and using X-ray imaging to monitor the catheter’s progress through the body. The patient risks trauma during the positioning process, while both patient and clinician must be exposed to X-rays for some time. The ARMM system computes a trajectory from a CT scan, navigates a tethered magnet through the arterial tree, and monitors the catheter’s progress in real-time using ultrasound. Leclerc et al. 2020 designed an untethered “magnetic swimmer” that, when subjected to a magnetic field, rotates and swims within the bloodstream [4]. One application is the treatment of acute pulmonary embolism. In a setting where a timely response with minimal side effects is essential, treatments such as anticoagulants or thrombolysis are inefficient, invasive, or dangerous. Instead, the magnetic swimmer can navigate the body’s blood vessels (even the chambers of the heart), taking advantage of its rotating motion and helical design to abrade the embolism.
The previous three projects use some form of custom electromagnets to control their respective robots. Erin et al. 2020 use magnetic fields generated by MRI devices to steer and control a robot with five degrees-of-freedom [5]. The cylindrical robot contains an air gap, inside which one can install cameras, lasers, or other components to achieve targeted yet minimally-invasive surgical procedures. While the magnetic swimmer is designed for blood vessels, the robot designed by Erin et al. is intended for organs.
As the research progresses, the cost and size of fourth-generation surgical robots are likely to decrease, while their accuracy, capabilities, and usage increase. Some identified challenges include miniaturization to the micrometer or nanometer scale, propulsion beyond electromagnets, visual feedback for the supervising surgeon, and social acceptability [1].
References
[1] C. Bergeles. From Passive Tool Holders to Microsurgeons: Safer, Smaller, Smarter Surgical Robots. IEEE Transactions on Biomedical Engineering 61.5, 1565-1576 (2014).
[2] T. L. Bruns et al. Magnetically Steered Robotic Insertion of Cochlear-Implant Electrode Arrays: System Integration and First-In-Cadaver Results. IEEE Robotics and Automation Letters (2020). Presented at the 2020 IEEE International Conference on Robotics and Automation (ICRA).
[3] C. M. Heunis et al. The ARMM System – Autonomous Steering of Magnetically-Actuated Catheters: Towards Endovascular Applications. IEEE Robotics and Automation Letters (2020). Presented at the 2020 IEEE International Conference on Robotics and Automation (ICRA).
[4] J. Leclerc et al. Agile 3D-Navigation of a Helical Magnetic Swimmer. IEEE International Conference on Robotics and Automation (ICRA 2020).
[5] O. Erin et al. Towards 5-DoF Control of an Untethered Magnetic Millirobot via MRI Gradient Coils. IEEE International Conference on Robotics and Automation (ICRA 2020).