Liver Excision-Cauterization
description
Transcript of Liver Excision-Cauterization
Liver Excision-Cauterization Amine Hallab
Kevin Mihelc
Jen Bacior
Hiroki Meguro
April 18th, 2005Mentors:
Kelly Dympna MD, John Patzer PhD
University of PittsburghSenior Design - BioE1160/1161
Outline• Background
• Problem Statement and Design Proposal• Quality System Considerations
• Design Description and Progression
• Heat and Materials Analysis
• Experimental Design
• Testing Results
• Future Considerations
Background
• 1 in 10 Americans are or have been afflicted with liver disease
• Treatments – Liver transplant
• The causes of liver diseases are poorly characterized
• Liver biopsy– Common procedure for afflicted liver diagnosis
– Essential tool for metabolic processes research
– American Liver Foundation 2003
– Maddrey, W C, “Atlas of the Liver,” 2004, Current Medicine Inc
Background Cont’d
• Liver biopsy results in major bleeding
• The current excision procedure is inconvenient
• The cauterization post excision is complicated and time consuming
• Requires immediate freezing upon excision for metabolite testing
• The metabolites are affected by the time from excision to freezing
– Askin et al. 2002
How do surgeons take a liver biopsy ?
- Fully excised pig liver - Picture taken by Amine Hallab- BioScience Tower
1cm
Problem Statement
• For transplant surgery and research purposes»There currently is no device that will
excise a biopsy and cauterize the host tissue simultaneously
• For research purposes »There is no mechanism to ensure biopsy
temperature control for metabolic processes measurements
Design Proposal
• Liver Excision-Cauterization (LEC)• LEC Functions
– To excise a biopsy wedge and cauterize at the same time– To provide temperature control» Thermal and electrical insulation/conduction
Design & Customer Requirements
• Outer conduction
• Inner insulation
• Affordable price
• Sharp blade
• Small and easy to use
• Easy to sterilize
Features & Benefits
• Combines 3 functions: tissue excision, wound cauterization, biopsy insulation
• Researchers can assure accuracy in metabolic measurements
• Prevent blood loss with easier and faster technique
• Market size is estimated by– 6,000 liver Transplants per year– In 2002 alone, $262 million was spent on liver research
• LEC would be sold by surgical instrument companies– Comparable surgical instrument only sells for $100.00
–www.ustransplant.org– American Liver Foundation (2002 annual report)
Quality System Considerations
• Human factors– Ease of use
– User hand comfort
– Protection from heat and current
• Regulatory– Class II device
• Safety– Stainless steel» Support stresses of
cutting technique
– Surgical latex gloves» User thermal and electrical
protection
– Sharpness of the blades» Avoid liver tissue deformation
» Blades can be re-sharpened
Project Management
BioE 1160
Goals
Initial Design Concept
Liver & Biopsy Research
Solid Model
Safety & Regulation
Market & Task communication
Design History File
J. Bacior
H. Meguro
A. Hallab
K. Mihelc
BioE 1161
Goals
Materials & Structural Analysis
SolidWorks Testing
Heat Transfer Analysis
Prototype & Fabrication
Animal Testing
J. Bacior
H. Meguro
A. Hallab
K. Mihelc
Design Progression
Initial LEC Design
LEC Version 2.0
LEC Version 3.0 LEC Version 3.125cm
25cm
Design Progression Cont’d
Physical Features:– Sharp blade
– Bent shaft
– Small
– Prototype»Nickel-plated ABS
– Final Tool»Stainless steel and
CeramicLEC Version 4.0
15cm
Design Description
t2
t1
L
α Conductive MaterialInsulation Material
L = 2 cmt1 = 0.5 mmt2 = 1.5 mm
α = 60˚
Structural Design and Materials
• The volumetric triangular shape provides:– Uniform conduction and efficient insulation
• Materials selection for proposed product– Stainless steel as the conductive surface»High thermal conductivity (14.6 W/m-K @ 100˚C)» Low electrical resistivity (0.5 Ω-cm)
– Ceramic as the insulation material
»High electrical resistivity ( >106 Ω-cm) » Low thermal conductivity (1.46 W/m-K @ 25˚C)
– www.accuratus.com
Heat Transfer Model • Differential thermal energy balance
– Eq (1) used to verify selected materials
– Heat transfer and thermal diffusivity chosen to .provide» Uniform conduction through stainless steel
» Insignificant biopsy temperature increase
• Conclusion– Proposed LEC materials will sufficiently meet
the .required temperature control needs of the product
genqTKt
Tc
).(
COSMOSWorks Analysis
FEA Thermal Study:• – 60°C applied to porcine
liver piece
• 110°C applied to back face of basket
COSMOSWorks Analysis
Thermal Analysis on Nickel-plated Somos 14120 (Prototype Materials)
Thermal Analysis on Cast Stainless Steel and Ceramic
Porcelain (Proposed Final Materials)
COSMOSWorks Analysis
• Conclusions:–Theoretical analysis shows that both the prototype and final LEC product will adequately promote hemostasis while protecting the biopsy tissue
Experimental Methods for Testing
• Porcine Liver– Cutting capability
– Cauterization efficiency
– Insulation efficiency
– Biopsy tissue protection
– Cutting and cauterizing simultaneously
1cm
Testing Results
• Excision ability – Failure
• Cauterization – Success
• Quick cauterization – Failure
• Biopsy protection – Success
• Overall– Positive user feedback
Constraints Limiting Phase I
• Economic– Labor costs to produce a single .stainless steel and ceramic prototype
• Regulatory– Scheduling between our device testing .and available animal research
Future Considerations
• Current generator with bipolar technique• Modification in cutting mechanism– Sharper blades– Cut as product of shearing
• Outer surface modification– Quicker cauterization
• Human factors modification– Handle protection and reduction in size
Acknowledgments
• Thank you to Drs. Hal Wrigley and Linda Baker whose generous gift made this project possible
• Thank you to department of BioEngineering for the generous support
• John Patzer, PhD
• Kelly Dympna, MD
• Professor Gartner
• Bob Barry
Time = 1 sec
Position cm
T (C)
Time = 50 sec
Position cm
T (C)
Time = 100 sec
Position cm
T (C)