Concentric Tube Robots
Concentric Tube Robots—a new robot technology that promises to revolutionize minimally invasive surgery.
Pierre Dupont, IEEE Fellow, is Chief of Pediatric Cardiac Bioengineering at Children’s Hospital Boston, Harvard Medical School. He is a member of the Electronic Products and Services Board of the IEEE Robotics and Automation Society.
Concentric tube robots are designed to balance the objectives of force application and steerability. Composed of telescoping curved metal tubes, they possess cross sections and stiffnesses comparable to needles
When performing repairs deep inside the body, surgeons have traditionally had to choose between precise control of their tools and minimizing the invasiveness of the surgery. This is because existing instruments for minimally invasive surgery trade off stiffness and steerability. For example, laparoscopic instruments, which consist of straight rigid shafts, can exert high forces, but typically require inflation of the abdominal cavity with gas to create enough room to move the instrument without damaging surrounding tissue. At the other extreme, catheters are designed to be flexible enough to follow the contours of the vasculature, however, they cannot be used to apply forces large enough to manipulate tissue. “Many surgeries today are performed as open, invasive procedures because surgeons lack the right tools,” says Pierre Dupont, Chief of Pediatric Cardiac Bioengineering at Children’s Hospital Boston, Harvard Medical School. “Our goal is to create the technology that will enable converting these open procedures to minimally invasive ones.”
Toward achieving this goal, Dupont and his group have invented a new type of robot that they call concentric tube robots. In contrast to existing medical instruments, concentric tube robots are designed to balance the objectives of force application and steerability. Composed of telescoping curved metal tubes, they possess cross sections and stiffnesses comparable to needles. Their shape, however, can be actively controlled through motorized rotation and translation of the individual tubes. This enables the robots to navigate through the body along complex 3D curves and also to manipulate tools at their tips, such as grippers, staplers, cutting tools and lasers. The surgeon controls the robots by means of joysticks and a keyboard.
In Dupont’s lab, they are currently using these robots to close holes inside the beating hearts of pigs. The robot enters the body through a vein in the neck and snakes its way through the vasculature to the inside of the heart. Using 3D ultrasound for visualization, the surgeon is able to precisely navigate the robot to the hole, pull on the tissue to close the hole and then seal it with a specially designed fastener. “An incredible advantage of the robot is that its combination of steerability and stiffness enables the surgeon to position the robot with millimeter accuracy inside the beating heart. This is something that is just not possible with a catheter,” says Dupont whose current goal is to adapt the technology to perform more complicated beating-heart surgeries, such as mitral valve repair.
A robot with forceps
Dupont acknowledges that surgery inside a beating heart is difficult. “I think we picked the hardest part of the body to work on first. But if we can make a robot work inside the heart, going anywhere else in the body will be easy.”
Besides cardiac surgery, there are many applications that would benefit from a curved, needle-sized robotic instrument that could steer through tissue and body cavities to perform surgical repairs. Dupont’s group is currently investigating applications of the technology in neurosurgery and urology.
Two concentric tube robots are shown dissecting chicken tissue. The robot on the left is equipped with a CO2 laser. The robot on the right has 1 mm wide forceps (fingers).
The video below demonstrates several versions of the teleoperated robot performing tasks on the bench top. It also demonstrates two specialized surgical tools developed for use with the robot inside the beating heart. The first tool is designed for removing tissue. The second tool is a suture substitute for attaching two layers of tissue.
