algorithmic port placement for robot-assisted cabg pierre dupont aerospace and mechanical...

Algorithmic Port Placement Algorithmic Port Placement for Robot-assisted CABGfor Robot-assisted CABG

Pierre DupontPierre Dupont

Aerospace and Mechanical Aerospace and Mechanical EngineeringEngineering

Boston UniversityBoston University

Collaborators:Collaborators:

Jeremy Cannon, CHCJeremy Cannon, CHC

Shaun Selha, BUShaun Selha, BU

Jeff Stoll, BUJeff Stoll, BU

Robert Howe, HarvardRobert Howe, Harvard

David Torchiana, MGHDavid Torchiana, MGH

endoVia Medical Seminar – August 23, 2002

Boston UniversityBoston University 22

Coronary Artery Bypass Graft (CABG) Coronary Artery Bypass Graft (CABG)

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


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


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.

Top Notch of Sternum

Xiphoid Process


Problems encountered - MGHProblems encountered - MGH

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.


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


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


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


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


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

Anastomosis


Implementation

5.5. Locating Ports on the Patient

1.1. CT Scan 2.2. Image Processing3.3. Surgical Planning

System

4.4. Operating Room Registration


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.


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


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)


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


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


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

repairrepair

algorithmic port placement for robot-assisted cabg pierre dupont aerospace and mechanical...

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