Robotic surgical systems, such as the da Vinci Surgical System (Intuitive Surgical, Inc., Sunnyvale, California), have revolutionized laparoscopic surgery but are limited by large size, increased costs, and limitations in imaging. Miniature in vivo robots are being developed that are inserted entirely into the peritoneal cavity for laparoscopic and natural orifice transluminal endoscopic surgical (NOTES) procedures. In the future, miniature camera robots and microrobots should be able to provide a mobile viewing platform. This article discusses the current state of miniature robotics and novel robotic surgical platforms and the development of future robotic technology for general surgery and urology.
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Laparoscopy reduces surgical invasiveness, and thus leads to a shortened recovery period and better cosmesis by decreasing the size of incisions within the abdominal wall. Today, long rigid instruments inserted into the peritoneal cavity through small incisions limit the surgeon’s range of motion, and thus the complexity of the procedures that can be performed. The advent of robotic surgical systems, such as the da Vinci Surgical System (dVSS; Intuitive Surgical, Inc., Sunnyvale, California), has revolutionized laparoscopic surgery. The addition of stereoscopic three-dimensional visualization, tremor abolition, increased dexterity, and motion scaling to robotic surgical systems has allowed the surgeon to perform complex tasks using only laparoscopic techniques. In addition to the loss of haptic feedback, the cameras currently used in robotic surgical systems have a limited view, relying on a fixed-port system that is constrained to 4 df . Current robots are bulky and require significant space allocation in an already crowded operating suite. Furthermore, there is a significant delay between the formulation of an idea, its development, and the commercialization of surgical robotic products. Robotic surgery, still in its infancy, should inevitably progress as several new concepts are brought to fruition.
Novel robotic surgical systems are being developed that address the aforementioned visualization and manipulation limitations; however, many of these systems remain constrained by the entry incisions. Alternatively, miniature in vivo robots are being developed that are inserted entirely into the peritoneal cavity for laparoscopic and natural orifice transluminal endoscopic surgical (NOTES) procedures. These robots can provide vision and task assistance without the constraints of the entry port incision while reducing the number of incisions required for laparoscopic procedures. Miniature robots are easily deployed in a myriad of environments. These robotic surgical systems are smaller, smarter, and less expensive. Easily deployable robots, tailored for specific operations, can be manipulated by telepresence and remote access. Miniature camera robots and microrobots should be able to provide a mobile viewing platform. This article discusses the current state of miniature robotics and novel robotic surgical platforms and the development of future robotic technology.
Present commercial systems and common limitations
The dVSS was the first surgical robotics system cleared by the US Food and Drug Administration (FDA) for use in general and urologic laparoscopic surgery. The system has three-dimensional visualization of the operating field, 7° range of motion, tremor elimination, and provision of comfortable postural seating for the operating surgeon. These advantages allow surgeons improved hand-like distal tip dexterity, tremor reduction, and correction of motion reversal and motion scaling, which ultimately provide enhanced precision. Urologists have widely accepted its use in prostate surgery. Studies have shown that robotic prostatectomy is safe and effective in men who have prostate cancer.
Surgeons using such robots lack haptic feedback during operations, are unable to switch instruments or tailor the operating field view during the procedure, are inhibited by the large size of the robot, and cannot justify the high cost of the technology. Much effort is being directed toward the development of next-generation robots with improved mobility and sensing and reduced complexity and cost. Today, research focused on the development of a master-slave telerobotic system, with enhanced dexterity and sensing using millimeter-scale robotic manipulators, can be found. Intelligent microsurgical instruments are also being developed to filter involuntary hand motion in handheld instruments. A full prototype of this device has demonstrated a reduction in tremor oscillations by as much as 50%. Other work focuses on developing smaller telerobotic surgical systems with improved haptics. Many surgical robotic developments have focused on mitigating and circumventing the incisional limitations of minimally invasive surgery; however, such devices continue to be constrained by the fulcrum effect.
Miniature in vivo robot platform for laparoscopy and natural orifice transluminal endoscopic surgical procedures
Miniature in vivo robots have been designed to assist surgeons during laparoscopic surgery by providing an enhanced view of the surgical environment from multiple angles and improving movement by means of dexterous manipulators unconstrained by the abdominal wall fulcrum effect. Miniature robots that are inserted completely into the peritoneal cavity can overcome some of the limitations of current surgical robotic systems, such as the dVSS, by restoring lost df . The miniature in vivo robots developed by the authors’ research group can be classified as having a fixed-base or mobile platform.
Miniature in vivo robot platform for laparoscopy and natural orifice transluminal endoscopic surgical procedures
Miniature in vivo robots have been designed to assist surgeons during laparoscopic surgery by providing an enhanced view of the surgical environment from multiple angles and improving movement by means of dexterous manipulators unconstrained by the abdominal wall fulcrum effect. Miniature robots that are inserted completely into the peritoneal cavity can overcome some of the limitations of current surgical robotic systems, such as the dVSS, by restoring lost df . The miniature in vivo robots developed by the authors’ research group can be classified as having a fixed-base or mobile platform.
Miniature robot family
Imaging Robots
The authors have created two types of imaging robots: the pan-and-tilt camera robot and the imaging robot. The 15-mm diameter pan-and-tilt camera robot, made of an aluminum body, was initially fabricated for standard laparoscopic use ( Fig. 1 ) and tested in a porcine in vivo environment. This robot allows for rotation of approximately two independent axes, allowing it to pan 360° and tilt 45°. Increased rotation enhances visualization and depth perception of the abdominal cavity in surgical procedures. Independent motors actuate the robot’s tilting lever and provide the panning motion. The entire assembly rests on a small ball bearing that is attached to the base and is externally controlled by a joystick. The platform legs are attached at the base and are abducted by torsion springs after abdominal entry. Light-emitting diodes (LEDs) provide illumination. The initial prototype was tethered for power; however, wireless prototypes are currently being developed.
The pan-and-tilt camera robot has been used to assist a standard laparoscopic cholecystectomy in a porcine model and a laparoscopic nephrectomy and prostatectomy in a canine model. In a nonsurvival porcine model experiment, a miniature camera imaging robot with a fixed-base platform was inserted through small abdominal incisions into the insufflated abdominal cavity. The placement of an additional trocar and laparoscopic instrument insertion were then viewed and guided using miniature robotic cameras. The miniature robots provided auxiliary visual feedback to the surgeon, giving an enhanced field of view from various orientations during a laparoscopic cholecystectomy. The robots were initially positioned by the surgeon and were reoriented, without requiring additional abdominal incisions, as needed throughout the procedure. The miniature robots provided additional camera angles that augmented surgical visualization and improved orientation.
The imaging robot consists of an inner housing containing the lens and focusing mechanism, two white LEDs for lighting, and a permanent magnet direct current (DC) micromotor for rotating the inner housing within the clear outer housing ( Fig. 2 ). This robot is 12 mm in diameter and designed to be inserted into the insufflated abdominal cavity through a standard trocar during laparoscopy or by endoscopic approach in NOTES procedures. Each end of the imaging robot is fitted with a magnetic cap. The robot is held to the peritoneum on the abdominal wall using the interaction of magnets housed in the robot with an external magnetic handle (see Fig. 2 ). The handle can be moved along the exterior surface of the abdomen for gross positioning and panning of the robot. The imaging robot’s video feedback is displayed on a standard monitor in the operating room. Miniature imaging robots provide the surgeon with better depth perception, improve patient safety, and enable effective planning and execution of surgical procedures.
Lighting Robot
The lighting robot is similar to the imaging robot and is held to the inner anterior abdominal wall through magnetic attraction between the magnetic end caps and the magnets housed on an external handle. The clear outer tube houses six white LEDs. As with the imaging robot, this lighting robot can be inserted through a standard trocar during laparoscopic surgery or endoscopically in NOTES procedures ( Fig. 3 ).
Modular Crawler or Mobile Endoluminal Robot
The mobile in vivo robot, or modular crawler, is composed of two independently driven wheels that enable forward, reverse, and turning motions within the abdominal cavity. A tail that collapses into the wheel tread for insertion through the trocar is used to prevent counterrotation. A 6-mm diameter permanent magnet DC micromotor is attached to each wheel using bearings and spur gears ( Fig. 4 ). The robot also carries an adjustable-focus image sensor that provides real-time video feedback to the surgeon.
Multiple miniature robots can be placed inside the peritoneal cavity unrestrained by the small diameter of the natural orifice. Such robots, when equipped with stereoscopic imaging, could provide much needed depth perception while allowing triangulation between the image plane and the motion of the instruments. Mobile miniature robots provide a remotely controlled platform for vision and surgical task assistance, which is a feasible system, as was successfully demonstrated in a porcine model. A mobile camera robot was introduced through the esophageal opening and inserted into the stomach through a sterile overtube using a standard upper endoscope. The robot explored the gastric cavity before advancing into the peritoneal cavity through a transgastric incision. Once fully inserted, an endoscope was advanced to view the mobile robot as it maneuvered within the peritoneal cavity. The robot was then retracted into the gastric cavity, and the transgastric incision was closed. The ability to navigate the peritoneal cavity without external restraint was advantageous, especially when using several robots simultaneously. These robots have the capability to traverse the abdominal cavity in all directions, obtain liver biopsies in porcine models (see Fig. 4 ), and provide enhanced imaging in operations, including nephrectomy and prostatectomy, as previously performed in canine models.
University of Nebraska AB1 Robot
A multiarmed dexterous miniature in vivo robot with stereovision capabilities has been developed to provide the surgeon with a stable repositionable platform for visualization and tissue manipulation while performing NOTES procedures in the peritoneal cavity. The basic design of the robot, shown in Fig. 5 , consists of two “arms” each connected to a central “body” by a rotational “shoulder” joint. Each arm consists of an upper arm and a lower arm fitted with forceps or a cautery end effector. The body of the robot is held to the upper abdominal wall using magnets housed in the body of the robot and an external magnetic handle that can be moved along the outer surface of the abdomen throughout a procedure to reposition the robot internally. This handle enables the surgeon to position the robot to obtain alternative views and workspaces within each quadrant of the peritoneal cavity without requiring an additional incision or a retroflexed configuration. This NOTES-compatible robot has successfully aided in the completion of various operations, including cholecystectomy ( Fig. 6 ) and small bowel dissection, in nonsurvivable porcine model experiments. The robot was inserted into the peritoneal cavity through an endoscopic gastrotomy and magnetically secured to the anterior abdominal wall. Using video feedback from on-board cameras, the authors explored the peritoneal cavity, identified the target small bowel for manipulation, and positioned the robot to provide a suitable workspace for visualization and tissue manipulation. A small bowel dissection was then performed ( Fig. 7 ). The forceps arm was extended toward the small bowel and was used to grasp the tissue. The arm was then retracted to provide access to the tissue for the cautery arm. The shoulder of the cautery arm was rotated, and the lower arm was extended to cauterize the small bowel. The robot provided flexibility for entrance through a gastrotomy and stability for visualization and dexterity, similar to that of routine laparoscopy, without abdominal wall incisions. This multiarmed dexterous miniature in vivo robot can potentially be used as a platform for urologic procedures, such as prostatectomy and nephrectomy, by means of a NOTES or laparoscopic approach.
