1204 Part F Field and Service Robotics eration or hands-on cooperative control interface.The positioning.or endoscope holding.One primary advan- primary value of these systems is that they can overcome tage of such systems is their potential to reduce the some of the perception and manipulation limitations of number of people required in the operating room,al- the surgeon.Examples include the ability to manipu- though that advantage can only be achieved if all the late surgical instruments with superhuman precision by tasks routinely performed by an assisting individual can eliminating hand tremor,the ability to perform highly be automated.Other advantages can include improved dexterous tasks inside the patient's body,or the abil-task performance (e.g.,a steadier endoscopic view), ity to perform surgery on a patient who is physically safety (e.g.,elimination of excessive retraction forces), remote from the surgeon.Although setup time is still or simply giving the surgeon a greater feeling of control a serious concern with most surgeon extender systems, over the procedure.One of the key challenges in these the greater ease of manipulation that such systems offer systems is providing the required assistance without pos- has the potential to reduce operative times.One widely ing an undue burden on the surgeon's attention.A variety deployed example of a surgeon extender is the daVinci of control interfaces are common,including joysticks, Part system [52.2](Intuitive Surgical Systems,Sunnyvale,head tracking,voice recognition systems,and visual CA)shown in Fig.52.2.Other examples include the tracking of the surgeon and surgical instruments,for ex- Sensei cathetersystem [52.6](Hansen Medical Systems,ample,the Aesop endoscope positioner[52.7]used both u Mountain View,CA.)and the experimental Johns Hop- a foot-actuated joystick and a very effective voice recog- kins University (JHU)Steady Hand microsurgery robot nition system.Again,further examples are discussed in shown in Fig.52.3.Further examples are discussed in Sect.52.3. Sect.52.3. It is important to realize that surgical CAD/CAM A second category,auxiliary surgical support and surgical assistance are complementary concepts. robots,generally work alongside the surgeon and per- They are not at all incompatible,and many systems have form such routine tasks as tissue retraction,limb aspects of both. 52.2 Technology 52.2.1 Mechanical Design Considerations designs.For example,laparoscopic surgery and percu- taneous needle placement procedures typically involve The mechanical design of a surgical robot depends cru- the passage or manipulation of instruments about a com- cially on its intended application.For example,robots mon entry point into the patient's body.There are two with high precision,stiffness and (possibly)limited basic design approaches.The first approach uses a pas- dexterity are often very suitable for orthopaedic bone sive wrist to allow the instrument to pivot about the shaping or stereotactic needle placement,and medical insertion point and has been used in the commercial robots for these applications [52.8-11]frequently have Aesop and Zeus robots [52.12,14]as well as several high gear ratios and consequently,low back-drivability, research systems.The second approach mechanically high stiffness,and low speed.On the other hand,robots constrains the motion of the surgical tool to rotate about for complex,minimally invasive surgery (MIS)on soft a remote center of motion (RCM)distal to the robot's tissues require compactness,dexterity,and responsive- structure.In surgery,the robot is positioned so that ness.These systems [52.2,12]frequently have relatively the RCM point coincides with the entry point into the high speed,low stiffness,and highly back-drivable patient's body.This approach has been used by the com- mechanisms. mercially developed daVinci robot [52.21,as well as by Many early medical robots [52.8,11,13]were es- numerous research groups,using a variety of kinematic sentially modified industrial robots.This approach has designs [52.15-171. many advantages,including low cost,high reliability, The emergence of minimally invasive surgery has and shortened development times.If suitable modifica-created a need for robotic systems that can provide tions are made to ensure safety and sterility,such systems high degrees of dexterity in very constrained spaces can be very successful clinically [52.9],and they can also inside the patient's body,and at smaller and smaller be invaluable for rapid prototyping and research use. scales.Figure 52.4 shows several typical examples of However,the specialized requirements of surgical current approaches.One common response has been to applications have tended to encourage more specialized develop cable-actuated wrists [52.2].However,a num-
1204 Part F Field and Service Robotics eration or hands-on cooperative control interface. The primary value of these systems is that they can overcome some of the perception and manipulation limitations of the surgeon. Examples include the ability to manipulate surgical instruments with superhuman precision by eliminating hand tremor, the ability to perform highly dexterous tasks inside the patient’s body, or the ability to perform surgery on a patient who is physically remote from the surgeon. Although setup time is still a serious concern with most surgeon extender systems, the greater ease of manipulation that such systems offer has the potential to reduce operative times. One widely deployed example of a surgeon extender is the daVinci system [52.2] (Intuitive Surgical Systems, Sunnyvale, CA) shown in Fig. 52.2. Other examples include the Sensei catheter system [52.6] (Hansen Medical Systems, Mountain View, CA.) and the experimental Johns Hopkins University (JHU) Steady Hand microsurgery robot shown in Fig. 52.3. Further examples are discussed in Sect. 52.3. A second category, auxiliary surgical support robots, generally work alongside the surgeon and perform such routine tasks as tissue retraction, limb positioning, or endoscope holding. One primary advantage of such systems is their potential to reduce the number of people required in the operating room, although that advantage can only be achieved if all the tasks routinely performed by an assisting individual can be automated. Other advantages can include improved task performance (e.g., a steadier endoscopic view), safety (e.g., elimination of excessive retraction forces), or simply giving the surgeon a greater feeling of control over the procedure. One of the key challenges in these systems is providing the required assistance without posing an undue burden on the surgeon’s attention. A variety of control interfaces are common, including joysticks, head tracking, voice recognition systems, and visual tracking of the surgeon and surgical instruments, for example, the Aesop endoscope positioner [52.7] used both a foot-actuated joystick and a very effective voice recognition system. Again, further examples are discussed in Sect. 52.3. It is important to realize that surgical CAD/CAM and surgical assistance are complementary concepts. They are not at all incompatible, and many systems have aspects of both. 52.2 Technology 52.2.1 Mechanical Design Considerations The mechanical design of a surgical robot depends crucially on its intended application. For example, robots with high precision, stiffness and (possibly) limited dexterity are often very suitable for orthopaedic bone shaping or stereotactic needle placement, and medical robots for these applications [52.8–11] frequently have high gear ratios and consequently, low back-drivability, high stiffness, and low speed. On the other hand, robots for complex, minimally invasive surgery (MIS) on soft tissues require compactness, dexterity, and responsiveness. These systems [52.2,12] frequently have relatively high speed, low stiffness, and highly back-drivable mechanisms. Many early medical robots [52.8, 11, 13] were essentially modified industrial robots. This approach has many advantages, including low cost, high reliability, and shortened development times. If suitable modifications are made to ensure safety and sterility, such systems can be very successful clinically [52.9], and they can also be invaluable for rapid prototyping and research use. However, the specialized requirements of surgical applications have tended to encourage more specialized designs. For example, laparoscopic surgery and percutaneous needle placement procedures typically involve the passage or manipulation of instruments about a common entry point into the patient’s body. There are two basic design approaches. The first approach uses a passive wrist to allow the instrument to pivot about the insertion point and has been used in the commercial Aesop and Zeus robots [52.12, 14] as well as several research systems. The second approach mechanically constrains the motion of the surgical tool to rotate about a remote center of motion (RCM) distal to the robot’s structure. In surgery, the robot is positioned so that the RCM point coincides with the entry point into the patient’s body. This approach has been used by the commercially developed daVinci robot [52.2], as well as by numerous research groups, using a variety of kinematic designs [52.15–17]. The emergence of minimally invasive surgery has created a need for robotic systems that can provide high degrees of dexterity in very constrained spaces inside the patient’s body, and at smaller and smaller scales. Figure 52.4 shows several typical examples of current approaches. One common response has been to develop cable-actuated wrists [52.2]. However, a numPart F 52.2
Medical Robotics and Computer-Integrated Surgery 52.2 Technology 1205 semiautonomously moving robots for epicardial [52.23] b or endoluminal applications [52.24,25]. Although most surgical robots are mounted to the surgical table,to the operating room ceiling,or to the floor,there has been some interest in developing systems that directly attach to the patient [52.28,29].The main advantage of this approach is that the relative position of 4.2mm the robot and patient is unaffected if the patient moves. The challenges are that the robot must be smaller and that relatively nonintrusive means for mounting it must be developed. Finally,robotic systems intended for use in specific imaging environments pose additional design chal- lenges.First,there is the geometric constraint that the robot (or at least its end-effector)must fit within the scanner along with the patient.Second,the robot's mechanical structure and actuators must not interfere Part F52 with the image formation process.In the case of X- ray and CT,satisfying these constraints is relatively straightforward.The constraints for MRI are more chal- lenging [52.30]. 52.2.2 Control Paradigms Surgical robots assist surgeons in treating patients by moving surgical instruments,sensors,or other devices in relation to the patient.Generally,these motions are controlled by the surgeon in one of three ways: d Preprogrammed,semi-autonomous motion:The de- sired behavior of the robot's tools is specified interactively by the surgeon,usually based on med- ical images.The computer fills in the details and obtains the surgeon's concurrence before the robot is moved.Examples include the selection of needle tar- get and insertion points for percutaneous therapy and Fig.52.4a-d Dexterity enhancement inside a patient's tool cutter paths for orthopaedic bone machining. body:(a)The daVinci wrist with a typical surgical in- Teleoperator control:The surgeon specifies the de- strument (here,scissors)[52.2]:(b)The end-effectors sired motions directly through a separate human of the JHU/Columbia snake telesurgical system [52.18]; interface device and the robot moves immediately. (c)Two-handed manipulation system for use in endogas- Examples include common telesurgery systems such tric surgery [52.26]:(d)five-degree-of-freedom 3 mm wrist as the daVinci [52.2].Although physical master and gripper [52.27]for microsurgery in deep and narrow manipulators are the most common input devices, spaces other human interfaces are also used,notably voice control [52.12]. ber of investigators have investigated other approaches,.Hands-on compliant control:The surgeon grasps the including bending structural elements [52.18],shape- surgical tool held by the robot or a control handle memory alloy actuators [52.19,20],microhydraulic on the robot's end-effector.A force sensor senses systems [52.21],and electroactive polymers [52.22]. the direction that the surgeon wishes to move the Similarly,the problem of providing access to surgical tool and the computer moves the robot to comply sites inside the body has led several groups to develop Early experiences with Robodoc [52.8]and other
Medical Robotics and Computer-Integrated Surgery 52.2 Technology 1205 4.2 mm b) c) d) a) Fig. 52.4a–d Dexterity enhancement inside a patient’s body: (a) The daVinci wrist with a typical surgical instrument (here, scissors) [52.2]; (b) The end-effectors of the JHU/Columbia snake telesurgical system [52.18]; (c) Two-handed manipulation system for use in endogastric surgery [52.26]; (d) five-degree-of-freedom 3 mm wrist and gripper [52.27] for microsurgery in deep and narrow spaces ber of investigators have investigated other approaches, including bending structural elements [52.18], shapememory alloy actuators [52.19, 20], microhydraulic systems [52.21], and electroactive polymers [52.22]. Similarly, the problem of providing access to surgical sites inside the body has led several groups to develop semiautonomously moving robots for epicardial [52.23] or endoluminal applications [52.24, 25]. Although most surgical robots are mounted to the surgical table, to the operating room ceiling, or to the floor, there has been some interest in developing systems that directly attach to the patient [52.28, 29]. The main advantage of this approach is that the relative position of the robot and patient is unaffected if the patient moves. The challenges are that the robot must be smaller and that relatively nonintrusive means for mounting it must be developed. Finally, robotic systems intended for use in specific imaging environments pose additional design challenges. First, there is the geometric constraint that the robot (or at least its end-effector) must fit within the scanner along with the patient. Second, the robot’s mechanical structure and actuators must not interfere with the image formation process. In the case of Xray and CT, satisfying these constraints is relatively straightforward. The constraints for MRI are more challenging [52.30]. 52.2.2 Control Paradigms Surgical robots assist surgeons in treating patients by moving surgical instruments, sensors, or other devices in relation to the patient. Generally, these motions are controlled by the surgeon in one of three ways: • Preprogrammed, semi-autonomous motion: The desired behavior of the robot’s tools is specified interactively by the surgeon, usually based on medical images. The computer fills in the details and obtains the surgeon’s concurrence before the robot is moved. Examples include the selection of needle target and insertion points for percutaneous therapy and tool cutter paths for orthopaedic bone machining. • Teleoperator control: The surgeon specifies the desired motions directly through a separate human interface device and the robot moves immediately. Examples include common telesurgery systems such as the daVinci [52.2]. Although physical master manipulators are the most common input devices, other human interfaces are also used, notably voice control [52.12]. • Hands-on compliant control: The surgeon grasps the surgical tool held by the robot or a control handle on the robot’s end-effector. A force sensor senses the direction that the surgeon wishes to move the tool and the computer moves the robot to comply. Early experiences with Robodoc [52.8] and other Part F 52.2
1206 Part F Field and Service Robotics Fig.52.5a-d Clinically deployed robots for orthopaedic surgery.(a,b) The Robodoc system [52.8.9]repre- sents the first clinically applied robot for joint reconstruction surgery and has been used for both primary and revision hip replacement surgery as well as knee replacement surgery. (c,d)The Acrobot system of Davies et al.[52.31]uses hands-on compliant guiding together with a form of vir- tual fixtures to prepare the femur and tibia for knee replacement surgery Part F52.2 surgical robots [52.16]showed that surgeons found time visual appreciation of deforming anatomy would this form of control to be very convenient and nat-be very difficult. ural for surgical tasks.Subsequently,a number of Teleoperated control provides the greatest versatil- groups have exploited this idea for precise surgical ity for interactive surgery applications,such as dexterous tasks,notably the JHU Steady Hand microsurgical MIS [52.2,12,17,32]or remote surgery [52.33,34].It robot [52.3]shown in Fig.52.3 and the Imperial Col- permits motions to be scaled,and (in some research sys- lege Acrobot orthopaedic system [52.31]shown in tems)facilitates haptic feedback between master and Figs.52.5c,d. slave systems.The main drawbacks are complexity, cost,and disruption to standard operating room work These control modes are not mutually exclusive and flow associated with having separate master and slave are frequently mixed.For example,the Robodoc sys-robots. tem [52.8,9]uses hands-on control to position the Hands-on control combines the precision,strength, robot close to the patient's femur or knee and pre- and tremor-free motion of robotic devices with some programmed motions for bone machining.Similarly,of the immediacy of freehand surgical manipulation. the IBM/JHU LARS robot.[52.16]used both cooper- These systems tend to be less expensive than telesurgical ative and telerobotic control modes.The cooperatively systems,since there is less hardware,and they can be controlled Acrobot [52.31]uses preprogrammed vir- easier to introduce into existing surgical settings.They tual fixtures Sect.52.1.3 derived from the implant exploit a surgeon's natural eye-hand coordination in an shape and its planned position relative to medical intuitively appealing way,and they can be adapted to images. provide force scaling [52.3,4].Although direct motion Each mode has advantages and limitations,depend- scaling is not possible,the fact that the tool moves in the ing on the task.Preprogrammed motions permit complex direction that the surgeon pulls it makes this limitation paths to be generated from relatively simple specifica- relatively unimportant when working with a surgical tions of the specific task to be performed.They are most microscope.The biggest drawbacks are that hands-on often encountered in surgical CAD/CAM applications control is inherently incompatible with any degree of where the planning uses two-(2-D)or three-dimensional remoteness between the surgeon and the surgical tool (3-D)medical images.However,they can also provide and that it is not practical to provide hands-on control of useful macro motions combining sensory feedback in instruments with distal dexterity. teleoperated or hands-on systems.Examples might in- Teleoperation and hands-on control are both com- clude passing a suture or inserting a needle into a vessel patible with shared control modes in which the robot after the surgeon has prepositioned the tip.On the other controller constrains or augments the motions specified hand,interactive specification of motions based on real- by the surgeon,as discussed in Sect.52.2.3
1206 Part F Field and Service Robotics a) c) b) d) Fig. 52.5a–d Clinically deployed robots for orthopaedic surgery. (a,b) The Robodoc system [52.8, 9] represents the first clinically applied robot for joint reconstruction surgery and has been used for both primary and revision hip replacement surgery as well as knee replacement surgery. (c,d) The Acrobot system of Davies et al. [52.31] uses hands-on compliant guiding together with a form of virtual fixtures to prepare the femur and tibia for knee replacement surgery surgical robots [52.16] showed that surgeons found this form of control to be very convenient and natural for surgical tasks. Subsequently, a number of groups have exploited this idea for precise surgical tasks, notably the JHU Steady Hand microsurgical robot [52.3] shown in Fig. 52.3 and the Imperial College Acrobot orthopaedic system [52.31] shown in Figs. 52.5c,d. These control modes are not mutually exclusive and are frequently mixed. For example, the Robodoc system [52.8, 9] uses hands-on control to position the robot close to the patient’s femur or knee and preprogrammed motions for bone machining. Similarly, the IBM/JHU LARS robot. [52.16] used both cooperative and telerobotic control modes. The cooperatively controlled Acrobot [52.31] uses preprogrammed virtual fixtures Sect. 52.1.3 derived from the implant shape and its planned position relative to medical images. Each mode has advantages and limitations, depending on the task. Preprogrammed motions permit complex paths to be generated from relatively simple specifications of the specific task to be performed. They are most often encountered in surgical CAD/CAM applications where the planning uses two- (2-D) or three-dimensional (3-D) medical images. However, they can also provide useful macro motions combining sensory feedback in teleoperated or hands-on systems. Examples might include passing a suture or inserting a needle into a vessel after the surgeon has prepositioned the tip. On the other hand, interactive specification of motions based on realtime visual appreciation of deforming anatomy would be very difficult. Teleoperated control provides the greatest versatility for interactive surgery applications, such as dexterous MIS [52.2, 12, 17, 32] or remote surgery [52.33, 34]. It permits motions to be scaled, and (in some research systems) facilitates haptic feedback between master and slave systems. The main drawbacks are complexity, cost, and disruption to standard operating room work flow associated with having separate master and slave robots. Hands-on control combines the precision, strength, and tremor-free motion of robotic devices with some of the immediacy of freehand surgical manipulation. These systems tend to be less expensive than telesurgical systems, since there is less hardware, and they can be easier to introduce into existing surgical settings. They exploit a surgeon’s natural eye–hand coordination in an intuitively appealing way, and they can be adapted to provide force scaling [52.3, 4]. Although direct motion scaling is not possible, the fact that the tool moves in the direction that the surgeon pulls it makes this limitation relatively unimportant when working with a surgical microscope. The biggest drawbacks are that hands-on control is inherently incompatible with any degree of remoteness between the surgeon and the surgical tool and that it is not practical to provide hands-on control of instruments with distal dexterity. Teleoperation and hands-on control are both compatible with shared control modes in which the robot controller constrains or augments the motions specified by the surgeon, as discussed in Sect. 52.2.3. Part F 52.2