Using the da Vinci Surgical System shown here, the surgeon operates while seated at a console viewing a 3D image of the surgical field. His or her fingers grasp the console’s master controls below the display, and the system translates the surgeon’s hand, wrist, and finger movements into precise, real-time movements of surgical instruments by the robot.
A system-level approach moves robotic surgery from science fiction to reality.
By PJ Tanzillo
In 1981, Star Wars Episode V: The Empire Strikes Back featured a scene in which autonomous robotic surgeons attached a mechanical hand to Luke Skywalker after his climactic battle with Darth Vader. Real-life autonomous robotic surgeons are still just fiction, but a new breed of medical machines is taking advantage of robotic concepts to aide surgeons with complex medical procedures.
Combining sophisticated and reliable electronic control systems and high-level design software with advanced mechanical elements has improved procedural safety and patient comfort level.
The improved medical machines are the result of applying a mechatronics approach to merge mechanical, electrical, control system, and embedded software design. It represents an industry-wide effort to improve the design process by integrating the best-available development practices and technologies to streamline the design, prototype, and deployment stages. By using system-level design software, domain experts, scientists, and doctors, who have expertise in medical procedures but not necessarily in programming, can develop medical machines themselves. With this approach, they can reliably develop, test, and validate complex robotic control systems. This opens up a new class of safety-critical applications that were previously out of reach of computer technology.
The University of Nebraska Medical Center, OptiMedica, and Lebanese University have all developed surgical devices – the da Vinci Surgical System, the PASCAL Photocoagulator, and a photodynamic-therapy robot, respectively – that have benefited from a mechatronics approach to development.
The da Vinci Surgical System
Laparoscopy is a type of minimally invasive surgery that uses long instruments inserted through small incisions. Compared with traditional open procedures, laparoscopy has revolutionized the treatment of abdominal pathologies by shortening recovery time with less pain, fewer adhesions, and better postoperative quality of life.
However, manual laparoscopy has also revealed several limitations during operation, including lack of depth perception, poor camera control, limited degrees of freedom of the instrument tips, and inverted hand-instrument movements. These limitations lead to unnatural and painful surgical postures that result in surgeon fatigue.
The advent of robotic assistive surgery using the da Vinci Surgical System (dVSS) – from Intuitive Surgical, Inc., in Sunnyvale, CA – has overcome some of the limitations of manual laparoscopy. In robot–assisted laparoscopic surgery, the surgeon sits at a console and remotely controls instruments via a surgical robot (see Figure 1). The 3D visualization provides depth perception and increased dexterity.
The wrist-like articulations of the instruments in the console have also been shown to improve surgeons’ dexterity by diminished tremor, scaled motion, and increased range of motion. The coordinated hand-instrument movement reduced training time using robotic systems compared to manual laparoscopy. The dVSS has been approved by the FDA for gastrointestinal, thoracic, urological, gynecological, and cardiac procedures.
The Nebraska Biomechanics Core Facility in the HPER Biomechanics Laboratory at the University of Nebraska at Omaha and the Robotic Surgical Laboratory at the University of Nebraska Medical Center collaborated to develop a training program for robotic surgery in which new surgeons can learn how to use this advanced robotic technology.
Using LabVIEW software, they acquire all the information from the robotic surgical system by connecting with the dVSS via TCP/IP. To acquire physiological measurements such as muscle activations and joint angles from the surgeon, they use the NI USB-6009 data acquisition (DAQ) device to connect the electromyography system and electrogoniometers. With this system, instructors can objectively evaluate surgical proficiency before and after the robotic surgical training protocol.
In this training protocol, they also use LabVIEW to create visual real-time feedback to show trainees how much force they apply on the training task or animate tissue. This visual feedback helps the trainees reduce the tissue damage they inflict with the procedure.
The PASCAL Photocoagulator
Used by retinal surgeons to treat a number of eye conditions, laser photocoagulation involves the controlled destruction of the peripheral retina using targeted laser pulses. While this type of treatment has proven effective at reducing the chances of vision loss by as much as 50%, it can be very tedious to both patients and doctors. Ophthalmologists can deliver only one burn at a time, and treatment can require as many as 2,000 burns. A full course of treatment typically requires two to four sessions, each lasting 12 to 15 minutes.
LabVIEW is used to control the robotic arm responsible for extremely precise photodynamic therapy application for cancer patients.
With a small, three-member design team, OptiMedica developed the PASCAL (Pattern Scan Laser) Photocoagulator. PASCAL has a fully integrated pattern scanning laser system that provides significantly improved performance for the physician administering the treatment as well as an enhanced therapeutic experience for the patient.
OptiMedica used the LabVIEW FPGA Module and commercial off-the-shelf (COTS) hardware from National Instruments because it provides the hardware determinism and fast response times needed to deliver large batches of precisely placed laser pulses in a fraction of a second. This significantly reduced the number of patient office visits and increased the comfort of the procedure.
With a single graphical development platform, OptiMedica quickly and efficiently designed and prototyped the machine to demonstrate the system to potential investors. Then, it took advantage of the smooth migration path to deploy the final system on intelligent PCI DAQ hardware.
When treating cancer, oncologists select from a number of techniques depending on the type and stage of the tumor in question. The most common techniques used today are photodynamic therapy (PDT), surgery, radiation therapy, chemotherapy, hormone therapy, and immunotherapy. PDT is a specialized form of phototherapy, a term comprising all treatments that use light to induce beneficial reactions in a patient’s body. PDT is a new technique capable of destroying unwanted tissue while sparing normal tissue.
During PDT treatment, a drug called a photosensitizer is administrated to the patient by injection. The photosensitizer alone is harmless and has no effect on either healthy or abnormal tissue. However, when light emitted by a laser is directed at the tissue containing the drug, the drug is activated and the tissue is rapidly destroyed precisely where the light has been directed. With this technique, oncologists can target the abnormal tissue with careful application of the light beam, which translates into more effective treatment.
Lebanese University developed an automated robotic mechanical manipulator with the primary function of skimming along the patient’s skin while performing the PDT technique. The robot uses NI motion controllers to precisely position the laser heads over the affected area of the patient’s body in certain geometrical designs, such as circular or elliptical shapes, to destroy the tumor.
The development team began by simplifying its robot configuration into 2D applications and by simulating movement using LabVIEW. Then, it extrapolated the same reasoning to a 3D problem and simulated the movement following the same process adopted in the simple 2D application. Finally, the team replaced the simulated input and output signals with measurements taken from real sensors and from driving real motors to control the real robot.
To learn more about designing and prototyping medical devices, visit http://www.ni.com embedded/medical_device.htm