liver excision-cauterization amine hallab kevin mihelc jen bacior hiroki meguro april 18 th, 2005...
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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 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
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