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)