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03/25/2003

Precision Design in Surgical Tools

Presented by:

Hugo Ramirez

Eugene Kushnir

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Microsurgery Overview Current Designs

DaVinci Surgical System Harmonic Scalpel Microsurgical Tele Robotic System

Future of Microsurgery References Questions / Comments

Agenda

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Principles for the development of Microsurgery Devices

Limits of Human precision Involuntary and inadvertent movements Noise and error in hand motion

Convert Procedures to Minimally Invasive Increase Precision

Increase recovery time Decrease post-operative pain Enhance dexterity

Enable Remote Participation Surgical Systems Neuroendoscopy

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Analysis of the Microsurgical Environment

Table 1. Microsurgical environment general specifications

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Analysis of the Microsurgical Environment

Figure 1. Microsurgical environment general force specifications

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Material Qualities Comparison

MATERIAL PROPERTY USES WEDLING FORMABILITY

304 STAINLESSSTEEL

CROMIUM = 12%

* STRESS CORROSION CRACKING ABOVE 60ºC* PITTING IN CHLORIDE ENVIRONMENTS

MOST WIDELY USED SST

* SEMICONDUCTOR IND.* SPRINGS

EXCELLENT

USUALY NO ANNEALING

EXCELLENT

316L STAINLESSSTEEL

CROMIUM = 20%(EXTRA LOW CARBON)

* MOLYBDENUM ADDS RESISTANCE TO PITTING, SULFURIC AND HYDROCHLORIC ACID, ALKALINE CHLORIDES

* PHARMACEUTICAL* JET ENGINE PARTS* PAPER PROCESSING

GOOD

ANNEALING REQUIRED

EXCELLENT

Ti6Al4V TITANIUM(Ti-90, Al-6, V-4)

* CORROSION RESISTANCE IN NATURAL AND CHEMICAL ENVIRONMENTS* RESISTANCE TO CHLORIDES* RESISTANT TO STRESS CORROSION CRACKING* CAN BE ANODIZED

MOST WIDELY USED ALLOY

* MEDICAL TOOLS DIFFERENT COLORS TO PREVENT REFLECTION OF LIGHT (EX. EYE SURGERY)* AEROSPACE* POWER GENERATION IND.

FAIR

ANNEALING REQUIRED

* GALLING HIGHER THAN STEEL* LOWER MODULUS OF ELASTISITY CAUSES SPRING-BACK* LOWER THAN STEEL DUCTILITY

NYLON 12(30% GLASS)

* LIGHT AND SELF LUBRICATING* LOW WATER ABSORBTION <0.5%

* MATERIAL OF CHOICE FOR GEARS IN MOTOR HEADS WHERE WEIGHT AND COST IS IMPORTANT

N/A EXCELLENT

TABLE 2. MATERIAL QUALITY

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Material Properties Comparison

MATERIAL DENSITY(lb/in^3)

YIELD STRENGTH(psi)

MODULUS OFELASTISITY (ksi)

CTE(in/in-ºF)

HARDNESSBRINELL (3000kg)

304 STAINLESSSTEEL

0.289 31200 28000 9.61 123

316L STAINLESSSTEEL

(EXTRA LOW CARBON)0.289 34100 28000 8.89 146

Ti6Al4V TITANIUM(Ti-90, Al-6, V-4)

0.163 120000 16500 4.78 334

NYLON 12(30% GLASS)

0.037 8702 305 27.8Rockwell R

(1/2" steel ball, 60kg)108

TABLE 3. MATERIAL PROPERTIES

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Da Vinci System Overview

Illustration courtesy Dr. Akhil Madhani

Da Vinci Surgical System – Three arm tele-operated robot

Degrees of Freedom (DOF) – 34-DOF Total Arms – 3-DOF for operation and 6-DOF for initial position on the

ports (incisions) plus 4-DOF for the endoscope Active End Effector (EndoWrist) – 3-DOF plus grip

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DaVinci System Overview (continued)

EndoWrist

Position Mechanism

0.4 inchIncision

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DaVinci Position Actuators – Arm

Master DeviceSurgeon Control System

Slave DeviceEndoWrist Control System

Force-Feedback System 1. Master Device – Servo-motors and encoders receive input from a

surgeon’s hands actuating robotic arms 2. Slave Device – Arms exert forces back through the console

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DaVinci Position Actuators – Arm (continued)

Click on image to Play/Pause Video Click on image to Play/Pause Video

COMPONENTS/SUBSYSTMES PARAMETERS

MOTORS(TOTAL OF 36 MOTORS)

13mm - 35mm

MOTOR GEAR HEARS(NYLON 12 GEARS FOR 13mm

SIZES)

REDUCTION 4:1 TO 20:1TORGQUE 0.15 lbf-ft TO 1.70 lbf-ftBACKLASH 0.7°

FEEDBACK SYSTEM(REAL TIME < 35 msec.)

* OPTICAL ROTARY WITH UP TO 2000 COUNTS/REV.* MAGNATIC LINEAR ENCODERS* PRECISION <50 m

SPEED (MAX.)ROTATIONAL 180°/secLENEAR 40 mm/sec

BALL SCREWS PRELOADED - 0° BACKLASH

TABLE 3. POSITION SYSTEM

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DaVinci Position Actuators - EndoWrist

Ultrasonic Shears

EndoWrist – 4-DOF

Motion controlled by tendon like cables to simulate human wrist movement

Modular design allows various surgical accessories and instruments to be used

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Harmonic Scalpel

High frequency ultrasonic energy to actuate the cutting blade. Simultaneous cutting and blood coagulation due to high speed Advantages:

Fewer instrument exchanges, Improved visibility in the surgical field Less tissue charring and dehydration (coagulation occurs at less than

100ºC) Disadvantages:

High initial cost

ULTRASONIC SCALPEL BODY DSP CONTROLED ULTRASONIC WAVE GENERATOR (55.5 KHZ)

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Harmonic Scalpel (continued)

The ultrasonic vibration of the cutting blade is generated by a piezoelectric ceramics that expand and contract under power from a 55.5 KHz wave generator.

Vibration Range: 50 to 100 µm (function of power level) 100 µm – Faster cutting less coagulation 50 µm – Slower cutting more coagulation

Tissue

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System Overview (Microsurgical Tele Robotic System)

Modified Steward type platform for the Micro-manipulator

6-DOF Positional Accuracy - within 50μm Workspace - 20mm × 20mm × 20mm

Master: Force-reflecting haptic master device. Slave: Surgery micro-manipulator

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Microsurgical Tele Robotic System - Slave

Stewart Platform Schematic

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Microsurgical Tele Robotic System - Master

Modified Stewart Platform Schematic

X

Y

ZBase

5 bar Linkage (Ball-Joined –top, Pin-Joined-bottom)

Platform

End Effector

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FUTURE OF MICROSURGERY

The New Order of Surgery Patient dataset of MRI, CT, and other physiological data Systems for interfacing anatomical and physiological data with finite ele-

ment modeling tools A surgical model to construct a simulation of the surgery High Precision Tele-robotic Surgical systems

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QUESTIONS / COMMENTS

Questions, comments and group discussion

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References

Chintwood, W. Randolph Jr, MD. “Enddoscopic Robotic Coronary Surgery- Is this Reality or Fantasy?” The Journal of Thoracic and Cardiovascular Surgery. July 1999; Volume 118: 1-3

Dong-Soo Kwon, et. al, “Microsurgical Telerobot System” Proc. of the IEEE/RSJ Int. Conf. on Intelligent Robots and Systems,pp. 945-950, 1998

Guthart, Gary, Salisbury, Kenneth Jr. “The IntuitiveTM Telesurgery System: Overview and Application” Proc. of IEEE Int. Conf. on Robotics and Automation, pp. 618-621, 2000

K.Y.Woo, B.D.Jin, D.S.Kwon, “A 6 DOF Force Reflecting Hand Controller Using the Fivebar Parallel Mechanism,” Proc. of IEEE Int. Conf. on Robotics and Automation, pp. 1597-1602, 1998

” Surgical Robots”, National Horizon Scanning Centre, University of Birmingham, Edgbaston, Birmingham, January 2000.

Yamano Ikuo, et. al, “Method for Controlling Master-Slave Robots using Switching and Elastic Elements” Proc. of IEEE Int. Conf. on Robotics and Automation, pp. 1717-1722, 2002.

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References

www.intuitivesurgical.com

www.cybelius.com

www.thetrocar.net

www.harmonicdrive.de

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Surgical System Applications

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Patient care advantages

less post-operative pain

less blood loss

lower risk for infection

decreased recovery times

reduced time in hospital

enhanced cosmetic results

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Motor Specifications

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Surgical System video Camera

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Block Diagram of EndoWrist

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Human Arm Degrees of Freedom

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Position Actuator (Microsurgical Tele Robotic System)

Harmonic Servo Motor

Advantages Positioning accuracy

and repeatability Not back-drivable Zero-Backlash High efficiency

Motor in Motion Simulation

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Harmonic Servo Motor Operation Principle

As soon as the Wave Generator starts to rotate clockwise, the zone of tooth engagement travels with the major elliptical axis.

When the Wave Generator has turned through 180 degrees clockwise the Flexspline has regressed by one tooth relative to the Circular Spline.

Each turn of the Wave Generator moves the Flexspline two teeth anti-clockwise relative to the Circular Spline.