For a long time, the ability of robots to interact with humans in our daily lives was more myth than reality— and the idea of robotics performing exceptionally complex tasks such as neurosurgery seemed like science fiction. However, in the mid-1980s computer technology started to catch up with design engineering, and the field of robotics began to truly evolve. The PUMA 560 (Programmable Universal Machine for Assembly or Programmable Universal Manipulation Arm), a standard industrial robotic arm, was initially developed by an engineer at Unimation, which became a subsidiary of Westinghouse Corp.

Fig. 1 – The da Vinci Xi Patient Side Cart (© 2016 Intuitive Surgical)

In 1985, Dr. Yik San Kwoh of Memorial Medical Center, Long Beach, CA, who developed a computer program that makes the arm work, shattered previous conceptions about robot-assisted surgery by successfully placing a needle for a human brain biopsy using Computed Tomography (CT) for guidance. This success effectively launched the “Age of Medical Robotics” around the world. The past 35 years have seen an explosion in the industry, with a global forecast of $11.4 billion by the year 2020.

A Brief History

The successful implementation of the PUMA 560 led to the development of the PROBOT at the Imperial College, London, UK, where, in 1992, Dr. Senthil Nathan completed the first entirely robotic surgery in history. Across the pond in Sacramento, CA, Integrated Surgical Supplies was already in the process of developing ROBODOC, a robot designed to mill out precise cavities in the femur, which would insert fittings during hip replacement surgery.

ROBODOC became the first robot to assist in a Total Hip Arthroplasty (THA) and was subsequently cleared by the FDA for wide use in THA surgeries. Today, the ROBODOC is still the only active robotic platform approved by the FDA for use in orthopedic surgery. These breakthroughs were closely watched by US military and NASA, who then funded private research companies to further investigate the capabilities of robots in the field. Telesurgery, the ability for a doctor to perform remote surgery, spurred several NASA scientists to join the Stanford Research Institute (SRI) with the goal to utilize virtual reality to develop a manipulator that could be used by a surgeon to operate from across a room.

Fig. 2 – Shown is the neuroArm in use.

The U.S. Army also had an interest in telesurgery for its potential to lower wartime casualties by bringing a virtual surgeon to an injured soldier who may be located on the battlefield. In 2005, DARPA, the Defense Advanced Research Projects Agency, envisioned and funded research that would allow an injured soldier to be loaded onto a vehicle or pod where a surgeon, located in a safe location, could use telepresence to make real-time medical decisions until the soldier could reach proper medical attention. Individuals working on the NASASRI team later formed commercial projects understanding the value of the emerging robotic market, and in 1995, Dr. Frederic H. Moll acquired the license to the NASA-SRI telepresence surgical system and started Intuitive Surgical Inc.

Today’s Surgical Robots

The most technologically advanced surgical robot in operation today is the da Vinci Surgical System by Intuitive Surgical Inc., Sunnyvale, CA. The system consists of three main components that work together seamlessly during surgical procedures: the Vision System, which includes a high-definition 3D endoscope and a large viewing monitor: the Patientside Cart that contains three or four robotic arms that carry out the surgeon’s commands; and the Surgeon Console, where the surgeon utilizes 3D imagery from the endoscope, as well as hand manipulators with Endowrist instruments (which provide seven degrees of motion, more than a human wrist) to perform the surgery. (See Figure 1)

Fig. 3 – Spring engaged brake with splined hub.

In 2000, the da Vinci system became the first robotic surgical system to be cleared by the FDA for general laparoscopic (abdominal) surgery. The da Vinci’s capabilities continued to evolve, and the FDA certified the robot for use in thoracoscopic (chest) procedures, as well as laparascopic removal of the prostate and a variety of urologic, gynecologic, pediatric, and otolaryngology approvals followed.

The technology used to develop these systems has grown exponentially since its introduction in 1985. A great example of merging robotics and motion control can be found in the neuroArm, developed in 2007 by a team led by Dr. Garnette Sutherland, Professor of Neurosurgery, University of Calgary. (See Figure 2) The neuroArm, a Magnetic Resonance Imaging (MRI)-compatible image-guided computer-assisted surgical robot designed for neurosurgery, was funded by the Canada Foundation for Innovation, Western Economic Diversification, Alberta Advanced Education and Technology and the philanthropic community of Calgary.

In 2008, this surgical system made history by performing the first brain surgery to remove a tumor through the use of its MRI-compatible robotics as well as an intraoperative MRI. The combined use of these technologies allows an MRI scanner to move into the operating room, providing in-depth imaging during the actual procedure without having to stop the surgery to review scans as before.

Fig. 4 – Permanent magnet brake with rotor/friction disc attached to armature plate.

Previously, combining these technologies was not thought to be feasible as the magnetic field produced by the MRI equipment is in the range of 1.5 to 3 Tesla or 15,000 to 30,000 gauss (for reference the Earth’s magnetic field is only 0.50 gauss). This means anything metallic inside of this field could potentially become a dangerous projectile as well as produce artifacts on any images the doctor would use to make critical surgical decisions.

To address this issue, Dr. Sutherland worked closely with engineering group who, in turn, succeeded in customizing a solution. They were able to modify motors specifically designed for use in a vacuum environment for semiconductor manufacturing by substituting ceramic parts, where stainless was previously used, and adding ceramic bearings. Using piezoelectric ceramic in the specialized motors allows motion to be created strictly through friction and filters to ensure the digital signal of the motors did not interfere with the MRI scanner.

Increasing Patient Safety Through Precision Robotics

An inherent risk of any surgery is uncontrolled or unwarranted motion—by robot or human hand—during a procedure, where even a slight misstep can be catastrophic. A surgeon’s hand is stable to roughly 100 microns, while a surgical robot is stable to roughly 25 microns. Many medical robots today are built to both aerospace and medical standards in order to guarantee quality control. Ensuring patient safety is always the top priority in the design. External brakes, haptic feedback hand controls, no-go zones, motion scaling, tremor filters, and battery backups have all been utilized on medical robots to increase patient safety.

Zero Backlash Brakes

New technologies are being developed to manage complementary issues that became apparent during the design and development of precision robotics. For example, one problem is the presence of backlash, or lost motion, caused by small gaps between a mechanism’s parts. Standard spring set power-off brakes, similar to those used in the original PUMA 560, are readily available and common in robotics, but generally have splined or hex-shaped hubs. These brakes experience considerable backlash because the design requires the hub and rotor (the friction disc in this case) to “float.” In order for the drive hub to float, sufficient clearances are required which consequently create backlash in the brake. (See Figures 3 and 4)

One solution to the issue of backlash is the electromagnetic permanent magnet power off brake (PMB). Electromagnetic PMBs have true zero backlash (no free play, no lost motion), making them ideal for robotic surgery equipment. Essentially, PMBs lock joints into place with absolutely zero radial movement.

In place of a “spring” that creates the normal force to transmit torque (as in Spring Engaged Brakes) the PMBs use Permanent Magnets to create the normal force. When the brake is energized, there is a reverse magnetic flux path created and the “return spring” disengages the braking surface, so when the power is “on” the brake is released. The “return” spring force is extremely low compared to the spring force required to transmit torque in a Spring Engaged Brake, therefore the PM brakes are very quiet in comparison—an important consideration in the operating room.

Permanent magnet brakes are also highly customizable, due to simple configuration and fewer parts, making them well suited for the numerous design iterations needed in order to engineer the best robotic surgery system possible. Other issues in robotic medical applications can also be resolved with the use of a PMB. PMBs are compact in size and have a low profile as well as high torque versus body size. Integral in the design of PMBs is a large inner diameter, which allows wires and cables to be run through the bodies.

PMB brakes operate at low voltage and have low current draw (to release). This is especially important if the equipment is portable or battery operated. PMB brakes are also environmentally friendly and UL, CSA, and RoHS compliant.

This article was written by Craig Harvey, Sales Engineer, and Rocco Dragone, Senior Sales/Application Engineer, at SEPAC, Inc., Elmira, NY. For more information, Click Here .


Medical Design Briefs Magazine

This article first appeared in the July, 2016 issue of Medical Design Briefs Magazine.

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