Mobile in vivo camera robots provide sole visual feedback for abdominal exploration and cholecystectomy
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- Rentschler, M.E., Dumpert, J., Platt, S.R. et al. Surg Endosc (2006) 20: 135. doi:10.1007/s00464-005-0205-7
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The use of small incisions in laparoscopy reduces patient trauma, but also limits the surgeon’s ability to view and touch the surgical environment directly. These limitations generally restrict the application of laparoscopy to procedures less complex than those performed during open surgery. Although current robot-assisted laparoscopy improves the surgeon’s ability to manipulate and visualize the target organs, the instruments and cameras remain fundamentally constrained by the entry incisions. This limits tool tip orientation and optimal camera placement. The current work focuses on developing a new miniature mobile in vivo adjustable-focus camera robot to provide sole visual feedback to surgeons during laparoscopic surgery. A miniature mobile camera robot was inserted through a trocar into the insufflated abdominal cavity of an anesthetized pig. The mobile robot allowed the surgeon to explore the abdominal cavity remotely and view trocar and tool insertion and placement without entry incision constraints. The surgeon then performed a cholecystectomy using the robot camera alone for visual feedback. This successful trial has demonstrated that miniature in vivo mobile robots can provide surgeons with sufficient visual feedback to perform common procedures while reducing patient trauma.
A primary patient advantage of minimally invasive surgery is reduced trauma, as compared to conventional open surgery, through the use of small incisions. However, these small incisions do not allow the surgeon to view or touch the surgical environment directly, and they constrain the motion of the end point of the tools and cameras to arcs of a sphere whose center is the insertion point. Such limitations have slowed the expanded use of laparoscopic techniques for complex procedures.
Several robot systems exist that help increase the surgeon’s dexterity by precisely manipulating laparoscopic tools. Such systems generally consist of a multi-arm robot external to the patient. Each arm manipulates a tool (or camera) that is teleoperated by a surgeon. The robots can filter the natural tremor present in the human hand, correct for the effects of motion reversal, and perform motion scaling to provide greater instrument control. Such systems, generally large and expensive, still are fundamentally constrained by the limited access to the abdominal cavity provided by small access ports.
A potentially new approach to laparoscopy involves inserting miniature robotic assistants entirely into the patient. Such wireless in vivo robots will provide vision and task assistance without being constrained by the entry incision. Robotic cameras inside the body can allow for better planning of trocar insertion and tool placement, while providing additional visual cues that help the surgeon to explore and understand the surgical environment more easily and completely.
These types of minirobots likely will fall into two main categories: fixed base and mobile. Fixed-base robots are positioned directly by the surgeon, and will be used predominantly to supply visual feedback for local procedures or to provide an overview of the surgical environment. Mobile robots will be capable of traversing abdominal organs to explore the abdominal cavity and provide sensor feedback (e.g., feedback on visual and environmental conditions). These robots, positioned via remote commands from the surgeon, will be extremely useful for identifying the location of the complication and providing task assistance. This mobile capability will be a key feature in the future. As techniques develop to perform procedures with fewer incisions so as to reduce patient trauma further, the surgeon will become less able to position fixed-base in vivo robots via direct manipulation.
Materials and methods
The use of robotics currently is recognized as the major driving force for the future technological advance of minimally invasive surgery [1, 9, 10]. Currently, robots used in surgery are implemented from outside the body, and therefore are still fundamentally constrained by the small access ports. Moreover, each of the robotic arms is necessarily long and bulky to accommodate the range of motion required to maneuver the long instruments attached to each arm. Large excursion arcs of the arms lead to collisions outside the patient, and improper placement of the access ports leads to collisions inside the patient . Each arm requires a separate access port. Hence the number of incisions is not reduced, as compared with traditional nonrobotic laparoscopy. These incisions are made as part of the setup procedure for the robot, so the problems associated with injuries caused by access port insertion [11, 12] remain unaddressed.
Similarly, a limited range of motion for the robotic camera still can result in obstructed or incomplete visual feedback. Tool changes still require removal of the existing tool and reinsertion of the new one, adding to the overall surgical time and adversely affecting the efficiency of the operation [2, 3]. Until visual feedback and dexterity improve, the enormous potential for minimally invasive surgery to replace many open conventional procedures will not be fully realized.
Initial work has begun to address in vivo robotic manipulators and visual feedback . Several prototype fixed-base in vivo camera robots have been used in conjunction with a standard laparoscope during porcine (swine) cholecystectomies to provide the surgeon with additional visual feedback . Findings have shown the quality of the images from these robot cameras to be comparable with that of current laparoscopic systems .
To the authors’ knowledge, tests conducted with the MARC robot represent the first use of in vivo wheeled robots during surgery to provide the sole source of visual feedback to the surgeon. The MARC robot was inserted through a fabricated trocar into an anesthetized pig, and the abdominal cavity then was insufflated with carbon dioxide. The trocar was designed to accommodate the 20-mm diameter of the MARC robot. Future robots will use standard 15-mm laparoscopic trocars.
Next, a standard trocar was inserted to provide an additional tool port. A third port also was created to accommodate a standard laparoscope. The laparoscope provided lighting for the MARC robot’s camera, but the surgeon did not use visual feedback from the laparoscope during the procedure.
This successful trial shows the great promise of mobile in vivo robotics, and the projected outcomes have the potential for important advancements in minimally invasive surgery. These tests have demonstrated that it is possible to perform a common laparoscopic procedure using an in vivo camera system as the sole source of visual feedback. This has the potential to reduce patient trauma by eliminating the need for a camera port and instead inserting mobile in vivo camera robots, such as MARC, through one of the tool ports. Although the initial prototype was slightly larger than a traditional trocar, future robots will be smaller in size, have no tethers, and incorporate additional sensors.
Miniature in vivo robots will be far more agile inside the abdominal cavity than the current generation of large and expensive external telemanipulators. Current laparoscopic robots are bulky and unwieldy and cannot be easily transported. Because of their cost, they typically are designed for multiple surgical procedures with interchangeable instrument arms. Future miniature robots may be designed for each specific task. Because they are small, multiple robots can be used simultaneously. Although it might be possible in the future for such robots to perform the entire procedure, current technology is more appropriate for use of the robots as assistants during surgery to aid in visualization and micromanipulation. Equipped with additional sensors, they also will be able to explore and provide tissue diagnosis.
The long-term goal is to use in vivo robots to improve the quality and safety of laparoscopic surgery. The rationale that underlies this research is that the ability to view the surgical field from multiple angles using dexterous manipulators not constrained by small incisions in the abdominal wall will help surgeons to realize the full potential of laparoscopic surgery.