Haptic Information in Minimally Invasive Surgery Tools for Use in

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					       Haptic Information in Minimally Invasive
            Surgery Tools for Use in Simulation




                              Ashley Elizabeth Seehusen




A dissertation submitted to the University of Bristol in accordance with the requirements of
     the degree of Doctor of Philosophy in the Faculty of Engineering, Department of
                                 Mechanical Engineering.


                                    September 2001
Abstract
The objective of this research is to understand the haptic information in a minimally
invasive surgery tool so that it may be appropriately reproduced in a MIS simulator. This
thesis looks at the generation of forces and accelerations at the tip of the tool, the
transmission of this haptic information along the shaft of the MIS tool and the perception of
this information at the handle.


To determine what haptic information is likely to be encountered in MIS, the maximum
dynamic forces and accelerations were measured using a test rig. In the rotational degrees
of freedom around the pivot point of the abdominal wall the maximum torque (as force is a
function of its distance from the pivot point) was 0.75 Nm for tool-tool collisions and 0.525
Nm for tissue-tool collisions. Maximum accelerations were given as 135 m/s2 for tool-tool
collisions and 84.0 m/s2 for tissue-tool collisions. For the degree of freedom that controls
the tip mechanism, the maximum force was found to be 15 N and the maximum
acceleration was found to be 100 m/s2.


The transmission of haptic information in the tool was considered in order to define the
relationship between tip and handle of a tool. A MIS tool was excited by a linear actuator
and the transfer functions relating the force and acceleration of the handle and the tip were
found. Through validation it was shown that this was an effective method for predicting
the behaviour of the handle.


Finally, several tests were done to determine the perception of haptic information at the
handle of a tool. First, the perception of small changes in frequency and amplitude of a
moving signal were tested. Perception was found to be most accurate between 2 and 8 Hz.
A 12% change in frequency and an 11% change in amplitude were determined to be at the
threshold of perception. Next, the ability to detect differences in phase of a moving signal
was shown to drop after 1.25 Hz. Then, it was found that to distinguish between two sharp
pulses there must be at least 0.02s between them in order for them to be felt. This test also
allowed a transfer function of human perception to be estimated as being second order
critically damped response with a time constant of 0.085s. The last two tests, the detection
of square step waves from round edged step waves and the ability to distinguish between
different waveforms, showed that the difference in rate of force change between two waves
determined whether they could be distinguished from each other.


                                                i
Acknowledgements


I would like to thank all of those who have helped me in my work:


Dr. Andrew Harrison for all of his help and his excellent guidance through the last year.


Dr. Peter Brett for the opportunity to come to Bristol and for his guidance in my first years
here.


Dave Baker for his inspiration and enduring patience.


The Mechanical Engineering Workshop and the department support staff for all of their
help.


My family for their never-ending support, encouragement, and talent at writing e-mails so I
never felt far from home.


Dan, Mariusz, Pensiri, and Dave for helping me stick. Ali, Alex, Katie, Katharine, Rose,
Lou and Helen for the excellent distraction. Matt for the encouragement and
understanding.


Finally, to the EC Esprit Program for funding the project that supported this research and
the Missimu project partners for their contribution.




                                              ii
Declaration
The accompanying thesis entitled "Haptic Information in Minimally Invasive Surgery
Tools for Use in Simulation" is submitted in support of an application for the degree of
Doctor of Philosophy in Engineering at the University of Bristol.


The thesis is based on independent work by the candidate. All contributions from other
have been acknowledged within the thesis. The supervisors' contributions were those
normally made in a British University. The views expressed within the dissertation are
those of the author and not of the University of Bristol.


None of the work in the thesis has been, or is being submitted for any other degree or
diploma at this or any other institution. Elements of this work have formed the basis two
conference papers.


I hereby declare that the above statements to be true.




Ashley Elizabeth Seehusen


September 2001




                                              iii
Table of Contents
Acknowledgements………………………………………………………………………….ii
Declaration………………………………………………………………………………….iii
Table of Contents…………………………………………………………………………...iv
Table………………………………………………………………………………………..vii
Figures………………………………………………………………………………..……viii
Graphs………………………………………………………………………………………ix


1. Introduction……………………………………………………………………..……….1
      1.2 Issues to Be Addressed in This Thesis…………………………………………..2
      1.3 Background Minimally Invasive Surgery ……………………………………….3
            1.3.1 Training Surgeons in Minimally Invasive Surgery……………………4
            1.3.2 Simulation for Training in Minimally Invasive Surgery………………5
            1.3.3 Summary of Minimally Invasive Surgery……………………………..7
      1.4 Haptics Background……………………………………………………………..7
            1.4.1 The Development of Haptics in Surgical Simulation…………………9
      1.5 State-of-the-Art Simulators and Haptics………………………………………...9
            1.5.1 Current Status of Simulators…………………………………………..9
            1.5.2 State of the Art Haptic Force Feedback ……………………………..12
            1.5.3 State of the Art Surgical Simulators…………………………………14
            1.5.4 Validation of Surgical Simulators……………………………………19
            1.5.5 Conclusion on State-of-Art Simulators ……………………………...22
      1.6 Need for and Importance of Research………………………………………….23


2. Haptic Information at the Tip of a Minimally Invasive Surgery Tool……………...24
      2.1 Introduction………………………………………………………………...…..24
      2.2 Background…………………………………………………………………….24
      2.3 Literature Review of Maximum Forces in Minimally Invasive Surgery………26
      2.4 Tissue Properties……………………………………………………………….28
      2.5. Testing in Degrees of Freedom 1&2…………………………………………..31
            2.5.1 Testing Set-Up in Degrees of Freedom 1&2…………………………31
            2.5.2 Force Results for Degrees of Freedom 1 &2……………….………...33
            2.5.3 Acceleration Results for Degrees of Freedom 1 &2……….………...36



                                       iv
      2.6 Testing in Degree of Freedom 5………………………………………………..41
            2.6.1 Testing Set-Up in Degree of Freedom 5……………………………..41
            2.6.2 Force Results in Degree of Freedom 5……………………...……….44
            2.6.3 Acceleration Results in Degree of Freedom 5……………………….46
      2.7 Conclusions…………………………………………………………………….47
            2.7.1 Conclusions for Degrees of Freedom 1&2…………………………...47
            2.7.2 Conclusions for Degree of Freedom 5……………………………….48


3. Transmission of Haptic Information in a Minimally Invasive Surgery Tool………50
      3.1 Introduction…………………………………………………………………….50
      3.2 Testing Methods………………………………………………………………..51
      3.3 Testing Set-Up in Degrees of Freedom 1&2…………………………………...52
      3.4 Results for Degrees of Freedom 1&2…………………………………………..54
            3.4.1 Point Frequency Test for Acceleration in Degrees of Freedom 1&2...54
            3.4.2 Swept Frequency Test for Acceleration in Degrees of Freedom 1&2
                   ………………………………………………….…………………..56
            3.4.3 Point Frequency Test for Force in Degrees of Freedom 1&2………..58
            3.4.4 Swept Frequency Test for Force in Degree of Freedom 1&2………..60
      3.5 Testing Set-Up in Degree of Freedom 5……………………………………….62
      3.6 Results for Degree of Freedom 5………………………………………………63
            3.6.1 Point Frequency Test for Acceleration in Degree of Freedom 5…….63
            3.6.2 Swept Frequency Test for Degree of Freedom 5………………….…65
      3.7 Validation of Transfer Functions………………………………………………69
            3.7.1 Results and Discussion for Validation of Transfer Functions………..70
      3.8 Conclusions…………………………………………………………………….72


4. Human Perception of Haptic Cues……………………………………………………74
      4.1 Introduction…………………………………………………………………….74
      4.2 Physiology of Haptic Perception……………………………………………….75
            4.2.1 The Skin………………………...……………………………………75
            4.2.2 The Sensing Receptors……………………………………………….76
            4.2.3 Conclusion on Haptic Perception…………………………………….78
      4.3 Literature Review of Haptic Perception………………………………………..79
      4.4 General Testing Methods………………………………………………………80



                                         v
      4.5 Differential Threshold Tests for Frequency and Amplitude…………………...83
            4.5.1 Frequency Test……………………………………………………….86
            4.5.2 Results for Frequency Test…………………………………………..86
            4.5.3 Amplitude Test……………………………………………………….90
            4.5.4 Results for Amplitude Test………………………………...………...90
      4.6 Phase Test………………………………………………………………………93
            4.6.1 Results for Phase Test………………………………………………..94
      4.7 Point Discrimination Test………………………………………………………95
            4.7.1 Point Discrimination Results…………………………………………96
      4.8 Conclusions………………………………………………………………….101


5. Human Perception of Haptic Events…………………………………..…………….103
      5.1 Introduction…………………………………………………………………...103
      5.2 The Step Test………………………………………………………………….103
            5.2.1 Testing Set-Up for the Step Test……………………………………103
            5.2.2 Results for the Step Test…………………………………………….105
      5.3 Waveform Test……………………………………………..…………………108
            5.3.1 Testing Set-Up for Waveform Test…………………………………108
            5.3.2 Results for Waveform Test…………………………………………110
      5.4 Conclusions…………………………………………………………………...116


6. Conclusions and Future Work…………………………………………...…………..117
      6.1 Maximum Forces and Accelerations in MIS………………………...………..117
      6.2 Transmission of Haptic Information in a MIS Tool…………………………..118
      6.3 Haptic Perception……………………………………………………………..119
      6.4 Future Work…………………………………………………………………..120
      6.5 Conclusions…………………………………………………………………...121


Appendix 1: Material Testing Stress-Strain Curves……………………………………...122

Appendix 2:Control Test Graphs for Frequency and Amplitude Test…………………...125

Appendix 3: Rate of Force Change Graphs for Waveform Test…………………………130

References………………………………………………………………………………..133




                                      vi
Table
Table 2.1 Young's Modulus of Tissues (Duck 1990; Carter 2000)………………………...30
Table 2.2 Young's Modulus of Materials Used…………………………………………….31
Table 2.3 Maximum Force, Torque and Acceleration Data for DOF 1&2………………...47
Table 2.4 Maximum Force and Acceleration Data for DOF 5……………………………..49
Table 4.1: Types of Haptic Sensory Receptors in the Glabrous Skin of the Hand………...76
Table 4.2: Points Assigned for Graded Answers…………………………………………..84
Table 4.3: Resulting Time Constants for Human Perception of Impulses……………….100




                                         vii
Figures
Figure 1.1 Elements of Haptic Information Explored in This Research…………………….1
Figure 1.2 The SensAble Technologies PHANTOM Haptic Interface…………………….13
Figure 1.3 The Set-up of the Immersion Laparoscopic Impulse Engine…………………..14
Figure 2.1: Five Degrees of Freedom in a MIS Tool ……………………………………...25
Figure 2.2 Maximum Force and Acceleration Testing Rig………………………………...31
Figure 2.3 Dimensions of Degree of Freedom 1&2 Testing Set-up……………………….32
Figure 2.4 Degree 5 Test Rig………………………………………………………………42
Figure 2.5 Dimensions of Degree of Freedom 5 Test Rig…………………………………43
Figure 2.6 Dimensions of Inner Rod and Handle Connection……………………………..44
Figure 3.1: Model of Simulator Design Including Tool Transmission Block in Red……...51
Figure 3.2: Degree of Freedom 1&2 Set-Up for Haptic Transmission Test……………….53
Figure 3.3 Dimensions for Transmission Test Set-up……………………………………..53
Figure 3.4: Degree of Freedom 5 Set-Up for Haptic Transmission Test…………………..62
Figure 3.5 Dimensions for Degree of Freedom 5 Set-up…………………………………..62
Figure 3.6: Model of Transfer Function Validation Simulation…………………………...69
Figure 4.1: Layers of the Skin and Sensory Receptors……………...……………………..76
Figure 4.2: Receptive Field Sensitivity Maps: SAI receptor and SAII receptor …………..77
Figure 4.3 Human Perception Testing Rig…………………………………………………81
Figure 4.4 Dimensions of Haptic Perception Testing Rig…………………………………81




                                         viii
Graphs
Graph 2.1: Stress-Strain Curves for Three Soft Tissues………………………………...…29
Graph 2.2: Example Strain Gauge and Acceleration Data for Maximum Force and
       Acceleration Testing for Interaction with Polymer………………………………...33
Graph 2.3 Maximum Force Graph for Different Collision Materials Used………………..34
Graph 2.4 Torques at Pivot Point for Different Collision Materials Used…………………34
Graph 2.5: Momentum of Tool at Tip and Handle in DOF 1&2 for Different Materials….35
Graph 2.6: Angular Impulse for Tip and Handle in DOF 1&2 for Different Materials……36
Graph 2.7 Maximum Acceleration Graph for Different Collision Materials Used………..37
Graph 2.8: Ratio of Tip/Handle Acceleration for Collision with Different Materials……..38
Graph 2.9: Acceleration Data and Frequency Content for Aluminium……………………39
Graph 2.10: Acceleration Data and Frequency Content for Polymer……………………...39
Graph 2.11: Acceleration Data and Frequency Content for Chicken Breast………………40
Graph 2.12: Acceleration Data and Frequency Content for Sponge 1……………………..40
Graph 2.13: Acceleration Data and Frequency Content for Sponge 2……………………..40
Graph 2.14 Example Data of Strain gauge and Acceleration Data for DOF 5 for Interaction
       with Chicken Breast………………………………………………………………..45
Graph 2.15 Maximum Forces in DOF5 for Different Materials…………………………...45
Graph 2.16 Maximum Acceleration in DOF 5 for Different Materials……….…………...46
Graph 3.1: Dynamic Amplification for Acceleration between Handle and Tip in DOF 1&2
       and Phase Difference between Handle and Tip for Acceleration in DOF 1&2..….54
Graph 3.2: Linear Sweep of Frequencies in DOF 1&2 for Acceleration at Tip and Handle
       ……………………………………………………………………………………...55
Graph 3.3: Bode Plots for Acceleration Transfer Function (Equation 3.1) in DOF 1&2 with
       Magnitude and Phase against Frequency………………………………………….57
Graph 3.4: Dynamic Amplitude between Force at Handle and Tip in DOF 1&2 and Phase
       Difference between Force at Handle and Tip in DOF 1&2………………………..58
Graph 3.5: Linear Sweep of Frequencies in DOF 1&2 for Force at Tip and Handle……...59
Graphs 3.6: Bode Plots for Force Transfer Function in DOF 1&2 with Magnitude and
       Phase against Frequency …………………………………………………………..61
Graph 3.7 Dynamic Amplification between Handle and Tip Acceleration in DOF 5 and
       Phase Difference between Handle and Tip Acceleration in DOF 5…………..……63
Graph 3.8: Linear Sweep of Frequencies in DOF 5 for Acceleration……………………...64



                                           ix
Graph 3.9: Bode Plots for Acceleration Transfer Function in DOF 5 for a Range of 1-200
       Hz with Magnitude and Phase against Frequency…………………………………66
Graph 3.10: Bode Plots for Acceleration Transfer Function in DOF 5 for a Range of 1-70
       Hz with Magnitude and Phase against Frequency…………………………………67
Graph 3.11: Bode Plots for Acceleration Transfer Function in DOF 5 for a Range of 70-200
       Hz with Magnitude and Phase against Frequency…………………………………68
Graph 3.12: Tip, Handle and Estimated Handle Values for Acceleration During Impact Test
       and Human Perception of Tip, Handle and Estimated Handle Values for
       Acceleration………………………………………………………………………..70
Graph 3.13: Tip, Handle and Estimated Handle Values for Force and Human Perception of
       Tip, Handle and Estimated Handle Values for Force………………………………71
Graph 4.1: Increase in Frequency from Set 1 to Set 2 for Frequency Test……………...…83
Graph 4.2: Increase in Force Amplitude from Set 1 to Set 2 for Amplitude Test…………84
Graph 4.3: Frequency Test Results in Absolute Terms for Different Percent Changes in
       Frequency…………………………………………………………………………..87
Graph 4.4: Frequency Test Results in Graded Terms for Different Percent Changes in
       Frequency…………………………………………………………………………..87
Graph 4.5: Frequency Test Results in Absolute Terms for Different Force Amplitudes….89
Graph 4.6: Frequency Test Results in Graded Terms for Different Force Amplitudes……89
Graph 4.7: Frequency Test Results in Absolute Terms for Different Percent Changes in
       Frequency…………………………………………………………………………..90
Graph 4.8: Frequency Test Results in Graded Terms for Different Percent Changes in
       Frequency…………………………………………………………………………..91
Graph 4.9: Frequency Test Results in Absolute Terms for Different Force Amplitudes….92
Graph 4.10: Frequency Test Results in Graded Terms for Different Force Amplitudes…..92
Graph 4.11: Phase Test: In Phase Pulses in Set 1 and Out of Phase Pulse in Set 2………..94
Graph 4.12: Phase Test Results in Both Absolute and Graded Terms……………………..95
Graph 4.13: Pulses Moving In and Out of Phase for Point Discrimination Test…………..96
Graph 4.14: Point Discrimination Detection for Several Different Approximation of Human
       Perception…………………………………………………………………………..98
Graph 4.15: Possible Human Perception Estimations for Impulse Offset of 0.010 s……...99
Graph 4.16: Possible Human Perception Estimations for Impulse Offset of 0.015 s……...99
Graph 4.17: Possible Human Perception Estimations for Impulse Offset of 0.020 s…….100
Graph 5.1: Step Waves with Square and Rounded Edge Waves in Step Test……………104



                                           x
Graph 5.2: Step Test Results Showing Percent Correct Versus Settling Time for Step….105
Graph 5.3: Estimations for Rig Response to Force Demand in Step Test…………..……107
Graph 5.4: Rate of Change of Force For Different Steps Demand……………………….108
Graph 5.5: A Square Wave as a Composite of a Sine Wave and Odd Harmonics……….109
Graph 5.6 Waveforms Used for Waveform Test…………………………………………110
Graph 5.7: Waveform Test Results for Comparison of Several Different Waveforms…..111
Graph 5.8: Ideal Drop off of Perceived Harmonics with an Increase in Base Frequency..112
Graph 5.9: Actual Perception of Harmonic Frequencies for Increasing Frequency Base..112
Graph 5.10: Actual and Estimated Waveform 2 at 1 Hz………………………………….113
Graph 5.11: Actual and Estimated Waveform 4 at 1Hz…………………………………..113
Graph 5.12: Perception of Percentage Rate of Change of Force between Higher Waveform
       and Lower Waveform……………………………………………………………..114
Graph 5.13: Perception of Difference in Rate of Change of Force……………………….115
Graph A1.1 Compressive Stress-Strain Curve for Polymer………………………………122
Graph A1.2 Tensile Stress-Strain Curve for Rubber Piping……………………………...122
Graph A1.3 Compressive Stress-Strain Curve for Chicken Breast ………………………123
Graph A1.4 Compressive Stress-Strain Curve for Sponge 1 …………………………….123
Graph A1.5 Compressive Stress-Strain Curve for Sponge 2 …………………………….124
Graph A2.1: Control Data for Frequency Test: Absolute Data…………………………...125
Graph A2.2: Control Data for Frequency Test: Graded Data…………………………….125
Graph A2.3. Frequency Actual Produced by the Rig versus the Demanded Frequency…126
Graph A2.4:. Percent Change in Frequency Achieved for Each Percentage Demanded…126
Graph A2.5: Force Amplitude Achieved for Each Amplitude Demanded……………….127
Graph A2.6: Control Data for Amplitude Test: Absolute Data…………………………..127
Graph A2.7: Control Data for Amplitude Test: Graded Data …………………………….128
Graph A2.8: Force Demand versus Force Achieved for Amplitude Test………………...128
Graph A2.9: Percent Change Achieved for Each Percent Change Demanded…………...129
Graph A2.10: Frequencies Achieved versus Frequencies Demanded……………………129
Graph A3.1 Rate of Force Change for Base Frequency 0.05 Hz…………………………130
Graph A3.2 Rate of Force Change for Base Frequency 1 Hz …………………………….130
Graph A3.3 Rate of Force Change for Base Frequency 2 Hz …………………………….131
Graph A3.4 Rate of Force Change for Base Frequency 4 Hz …………………………….131
Graph A3.5 Rate of Force Change for Base Frequency 8 Hz …………………………….132




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