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The word robot is a ubiquitous term that describes an autonomous device capable of various tasks. Industrial robots used in assembly lines perform highly precise, repetitive tasks. The robots are preprogrammed off-line, and tasks are invoked on command. Robots used in orthopedic surgery and neurosurgery are examples.[16] Precise tasks such as drilling and probe insertion are based on registration. Registration is a mathematical process that allows location and anatomic orientation in
Figure 66-1
Degrees of freedom (DOFs) in motion. A,
Conventional laparoscopic instruments have only 4 DOFs and grip. Insertion (i.e.,
movement in the z axis), roll, and movement along
the x and y axis
outside the body relative to a fulcrum point constitute the 4 DOFs. B,
Depiction of the EndoWrist instrument with two added intracorporeal joints produce
6 DOFs along with grip. (A and B,
© 1999 Intuitive Surgical, Inc., Sunnyvale, CA.)
A second type of robot is defined as an assist device, such as AESOP. These robots are used to control instrument location and guidance. Assist-device robots are not autonomous; they need input cues from the operator.
A third type of robot is a telemanipulator. These robots are under constant control of the operator. These devices mimic the operator's hand motions in an exact or scaled motion. There are several telemanipulator robotic devices available throughout the world. The da Vinci Robotic Surgical System ( Fig. 66-2 ) has been cleared by the FDA for laparoscopy, thoracoscopy, and intracardiac mitral valve repair surgery, and the ZEUS Surgical System ( Fig. 66-3 ) has been developed in parallel and cleared for sale by the FDA for general and laparoscopic surgery. The two systems are very similar, with some minor differences. The da Vinci Robotic Surgical System is described in this chapter as a representation of most modern surgical robots.
The da Vinci system has three components: a console, an optical three-dimensional vision tower, and a surgical cart. The surgical cart has three arms that can be manipulated by the surgeon through real-time computer-assisted control. One of the arms holds an endoscopic camera, and the other two are manipulator or instrument-holding arms. The system allows the surgeon to be physically remote from the patient. The system's instruments are designed to have 6 degrees of freedom plus grasp, which enables it to approach the identical articulation of the human wrist ( Fig. 66-4 ). The system design incorporates a frequency filter that eliminates hand tremor greater than 6 Hz.[17] Motion scaling can also be invoked up to a ratio of 5:1 (i.e., the surgeon moves 5 cm, and the robot moves 1 cm). Scaling allows for work on a miniature scale. The console also provides a three-dimensional image of the surgical field. The endoscope consists of dual, independent optical channels capable of transmitting digital images to the console's visual monitor. At the console, the surgeon is actually looking at two separate monitors; each eye sees through an independent
Figure 66-2
The da Vinci System Surgeon console (A)
and of the cart with three mounted surgical arms for holding the camera and instruments
(B). (A and
B, © 1999 Intuitive Surgical, Inc., Sunnyvale,
CA.)
The surgeon sits at the console and controls the telescope arm and two robotic manipulator arms. The surgeon has a viewing space that is similar to a double-eyepiece microscope. Each eyepiece displays a mirror reflection of a computer monitor screen. Each monitor displays one channel of the stereo endoscope to an eye, creating a virtual three-dimensional stereoscopic image of the surgical field.
The surgeon controls the manipulators with two masters. The masters are made of levers that attach to index fingers and thumbs of each hand. Wrist movements replicate the movements of the instruments at the end of the robotic
Figure 66-3
A, The console of the
ZEUS robotic telemanipulation system consists of a video monitor and two instrument
handles that translate the surgeon's hand motions into an electrical signal that
moves the robotic instruments. B, Two table-mounted
AESOP arms hold instruments, and a third arm controls the camera. (Courtesy
of Computer Motion, Inc., Sunnyvale, CA.)
The side cart of the robotic device has three arms that respond to the manipulative controls of the surgeon while sitting at the console. The cart is bulky and of tremendous weight. It requires wheeling to the vicinity of the patient's surgical area and is locked into place. Because of the proximity of the side cart to the patient, the patient must be guarded against inadvertent contact from the motions of the robotic arms. Even more important, after the instruments are engaged to the arms of the robot and inside the patient, the patient's body position cannot be modified unless the instruments are disengaged entirely and removed from the body cavity.
Figure 66-4
The EndoWrist instrument of the da Vinci System mimics
the natural kinematics of the surgeon's hand and wrist. This design allows 6 degrees
of freedom and grip. (© 1999 Intuitive Surgical, Inc., Sunnyvale, CA.)
The optical tower contains the computer equipment needed to integrate the left and right optical channels to provide stereoscopic vision and to run the software needed to control the kinematics of the robotic arms. The computer interfaces the translated motion of the surgeon's hands to a digital code that moves mechanical levers, motors, and cables that allow the robot to articulate the exact motions of the surgeon's hand.
The instruments in the body cavity must remain sterile but interface with nonsterile robotic arms. Detachable disposable instruments facilitate this interface. Each type of instrument requires different forces and motion scaling intrinsic to the task at hand and requires specific computer software processing. Additional operating room staff is required for detaching and exchanging task specific instruments throughout the case. Monitors are positioned on top of the tower so that all people in the operating room have a view of the surgical field.
An obstacle that still needs research is tactile sensing. The feedback that the robot offers for the surgeon's applied force is inferior. The robot offers some sensation, but the applied force does not correlate well with the force applied to the tissues. This correlation varies with the type of instrument and depends on the torque applied; the operator therefore must rely on visual cues from tissue distortion to gauge how much pressure is being generated.
The ZEUS Surgical System is another example of a master-slave telemanipulator. It employs the assistance of the AESOP Robotic System for visualization. It is basically one mechanical arm used by the physician to position the endoscope, which is a surgical camera inserted into the patient. Foot pedals or voice-activated software allow the physician to position the camera, leaving his or her hands free to continue operating on the patient. The manipulators of the ZEUS system are freely mounted on the operating table, much like the AESOP. It provides tremor filtering and motion scaling from 2:1 to 10:1.
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