Algorithmic Port Placement Algorithmic Port Placement for Robot-assisted CABG for Robot-assisted CABG Pierre Dupont Pierre Dupont Aerospace and Mechanical Aerospace and Mechanical Engineering Engineering Boston University Boston University Collaborators: Collaborators: Jeremy Cannon, CHC Jeremy Cannon, CHC Shaun Selha, BU Shaun Selha, BU Jeff Stoll, BU Jeff Stoll, BU Robert Howe, Harvard Robert Howe, Harvard David Torchiana, MGH David Torchiana, MGH endoVia Medical Seminar – August 23, 2002
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Algorithmic Port Placement for Robot-assisted CABG Pierre Dupont Aerospace and Mechanical Engineering Boston University Collaborators: Jeremy Cannon, CHC.
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Algorithmic Port Placement Algorithmic Port Placement for Robot-assisted CABGfor Robot-assisted CABG
Pierre DupontPierre Dupont
Aerospace and Mechanical Aerospace and Mechanical EngineeringEngineering
Consists of two Consists of two proceduresprocedures
1.1. Harvest of the Left Harvest of the Left Internal Mammary Internal Mammary Artery (LIMA)Artery (LIMA)
2.2. Anastomosis of LIMA Anastomosis of LIMA and coronary artery.and coronary artery.
Coronary Artery
Aorta Internal Mammary Artery (from chest)
Saphenous Vein (from leg)
Plaque Blockages
Illustration by Mitchell Christensen copyright ViaHealth 1999
Anastomosis Site
Boston UniversityBoston University 33
Procedure HistoryProcedure History
Non-endoscopic Non-endoscopic suturingsuturing• Median SternotomyMedian Sternotomy• Mini SternotomyMini Sternotomy• Anterior ThoracotomyAnterior Thoracotomy
Endoscopic CABGEndoscopic CABG• ZEUS and AESOP ZEUS and AESOP
Robotic System at MGHRobotic System at MGH
Top Notch of Sternum
Xiphoid Process
Boston UniversityBoston University 44
How are the port locations selected?How are the port locations selected?
Literature - templatesLiterature - templates
Practice – use Practice – use external landmarks external landmarks and size of patient’s and size of patient’s torso to make their torso to make their best guess.best guess.
2. Inability to perform the surgical procedure due to the orientations of the tools with respect to each other and the surgical site,
3. Internal instrument / endoscope collisions,
4. Robot singularities and joint limits,
5. Robot collisions.
Boston UniversityBoston University 66
Approach Port placement and robot placement problems can be solved independently.
● Port placement
● Robot placement
1. Inability to reach the surgical site,
2. Inability to perform the surgical procedure due to the orientations of the tools with respect to each other and the surgical site,
3. Internal instrument / endoscope collisions,
4. Robot singularities and joint limits,5. Robot collisions.
Robot placement
Port placement
Boston UniversityBoston University 77
How do we define dexterity? Preserve surgeon’s intuition
Orient instruments by task and with respect to the surgical site
Avoid internal collisions
Permit flushing of endoscope lens
Minimize the amount of the endoscope inserted into the chest cavity
Right Instrument
Left Instrument
Line of Sight
Invasive CABG Procedure
Boston UniversityBoston University 88
Surgical site coordinate frame
Figure Key Instrument Angles
= Yaw angle in instrument plane
= Elevation angle of instrument plane
Endoscope Angles
= Azimuthal angle
= Elevation angle
= Constant offset angle
θ
γ
e
a
o
Boston UniversityBoston University 99
Dexterity MetricDexterity Metric
Definition: Definition: Sum, over all surgical Sum, over all surgical sites, of the weighted squared sites, of the weighted squared “distance” of the instruments “distance” of the instruments and the endoscope from their and the endoscope from their optimal orientation angles.optimal orientation angles.
( ) ( )i opt i opt1
Dn T
i
ψ ψ W ψ ψ=
= - -å
diagonal weighting matrixW =
, , , , ,T
i r r l l e a i =é ùë û
optψ = vector of optimal orientation angles
Boston UniversityBoston University 1010
Rationale for optimal angles
LIMA take-down
oφ
Optimal values based on surgeon’s experience in performing invasive and minimally invasive CABG’s
Instrument angles are task based.Endoscope angles are viewpoint based
System evaluation Thorax model: ribs with neoprene skinThorax model: ribs with neoprene skin
Task: vessel dissectionTask: vessel dissection• 3 mm diameter “vessel” of stiff clay encased in 3 mm diameter “vessel” of stiff clay encased in
“soft tissue” matrix of modeling dough and then “soft tissue” matrix of modeling dough and then shrink wrapped.shrink wrapped.
• Three dissections: two at extremes of LIMA Three dissections: two at extremes of LIMA takedown and one at site of coronary artery.takedown and one at site of coronary artery.
Boston UniversityBoston University 1313
System evaluationSystem evaluation
= Endoscope Port= Instrument Ports
Six staff cardiac Six staff cardiac surgeons.surgeons.
Three sets of ports Three sets of ports comparedcompared
1.1. LIT = template from LIT = template from literature.literature.
2.2. SURG = cardiac SURG = cardiac surgeons with surgeons with thoracoscopic and thoracoscopic and minimally invasive minimally invasive surgery experience.surgery experience.
3.3. ALG = algorithmic ALG = algorithmic port placementport placement
Boston UniversityBoston University 1414
Dissection SpeedDissection Speed
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
Proximal Distal Coronary Mean
Literature
Surgeon
Algorithm
Dis
sect
ion
spee
d (m
m/m
in)
Boston UniversityBoston University 1515
Length of Gouges Length of Gouges >> 1.5 mm deep 1.5 mm deep
0.00
5.00
10.00
15.00
20.00
25.00
30.00
Proximal Distal Coronary Mean
Gou
ge L
engt
h (%
)
Literature
Surgeon
Algorithm
Boston UniversityBoston University 1616
SummarySummary
Decoupled robot placement Decoupled robot placement from port placementfrom port placement
Developed a dexterity metric Developed a dexterity metric based on optimal orientationsbased on optimal orientations
Preliminary in vitro trialsPreliminary in vitro trials• Dissection speed increased 25%Dissection speed increased 25%
• Gouge length decreased 50% or Gouge length decreased 50% or moremore
Boston UniversityBoston University 1717
Long-term role of algorithmic port placementLong-term role of algorithmic port placement
Routine use versus special Routine use versus special cases?cases?• Image library comparison of Image library comparison of
algorithmic port selectionsalgorithmic port selections
Development of new proceduresDevelopment of new procedures• Beating heart intracardiac ASD Beating heart intracardiac ASD