Cauterization Cauterization CatheterCatheter

Brad Wood, M.D.Brad Wood, M.D.Charles BlythCharles Blyth

Cristina FernandezCristina FernandezScott HittingerScott HittingerCameron JonesCameron JonesBrian McGeeBrian McGee

LiverLiver

http://www.tgt.vanderbilt.edu/reu2/REU2000/REU2000Kim.PPT

KidneyKidney

http://www.umm.edu/transplant/images/kidney.gifhttp://www.yoursurgery.com/procedures/kidneytransplant/images/KidneyTransAnatomy.jpg

Catheter UseCatheter Use

Nephrostomy and/or Biliary TubesNephrostomy and/or Biliary Tubes Drain the bile from the gallbladder Drain the bile from the gallbladder

before, during, or after surgerybefore, during, or after surgery Drain the urine from the kidneys Drain the urine from the kidneys

before, during, or after surgerybefore, during, or after surgery

Big PictureBig Picture

The liver and kidney are highly The liver and kidney are highly vascularizedvascularized Hepatic portal vein, hepatic Hepatic portal vein, hepatic

arteryartery Bile duct (Liver)Bile duct (Liver) Internal bleeding during Internal bleeding during

removalremoval Individuals with problems need Individuals with problems need

the procedure, but the procedure the procedure, but the procedure will be denied due to the risk of will be denied due to the risk of fatal internal bleeding fatal internal bleeding

.1 – 3.6% of cases .1 – 3.6% of cases

Our JobOur Job

Catheter to prevent bleeding upon Catheter to prevent bleeding upon removalremoval Conductive polymerConductive polymer Cauterization of tissue tractCauterization of tissue tract

0 - .2g of blood loss0 - .2g of blood loss 0 – 1mL of blood loss0 – 1mL of blood loss

CauterizationCauterization

Used mainly to Used mainly to coagulate tissue coagulate tissue stopping bleedingstopping bleeding

First performed with First performed with burning logs of fireburning logs of fire

22ndnd generation of generation of cauterization techniques cauterization techniques utilized heated metals utilized heated metals

Current therapeutic Current therapeutic techniques are based techniques are based upon electrocauteryupon electrocautery

RF AblationRF Ablation A technique that can bake A technique that can bake

internal tissue using radio internal tissue using radio frequency wavesfrequency waves

RF waves are transferred RF waves are transferred by microelectrodes to by microelectrodes to tissue where the frictional tissue where the frictional movement of ions movement of ions generates thermal energy generates thermal energy

Proteins are denatured Proteins are denatured and cells destroyedand cells destroyed

Ablation TechniquesAblation Techniques

Collagen/Fibrin PlugCollagen/Fibrin Plug Injection technique, cumbersome approachInjection technique, cumbersome approach

RF PulseRF Pulse Cauterization, tissue damageCauterization, tissue damage

Pritchard et al. “Radiofrequency Cauterization with Biopsy Introducer Needle”. Journal of Vascular Interventional Radiology 2004.

Average blood loss

Without Ablation: .30 gramsWith Ablation: .00044 grams

Prototype DesignPrototype Design• Plastics allow for flexibility

and mobility

• Conductive polymers• poly – acetylene• poly – thiophene

• Polyurethane/Silicone base

• Resistivity and Conductivity

Conductivity of PolymersConductivity of Polymers

Vetenskapsakdemien, K. “Conductive Polymers”. Nobel Prize in Chemistry, 2000.

Heat TransferHeat Transfer

Heat conduction Heat conduction equation governs equation governs heat transfer in heat transfer in transfertransfer Important for Important for

determining effective determining effective ablation radiusablation radius

Difficult to model Difficult to model since most equations since most equations and models assume and models assume constant electric constant electric conductivity in tissueconductivity in tissue

Effective RadiusEffective Radius

Several models Several models attempt to attempt to determine determine effective radius effective radius based on the based on the strength of the strength of the electric field as electric field as the distance the distance from the probe from the probe increasesincreases

Some Values to Apply to Some Values to Apply to ModelsModels

Power = 200 W with a resistance of 50 ohms and Power = 200 W with a resistance of 50 ohms and current of 2 amps RMScurrent of 2 amps RMS

Ambient Temperature (Tamb)+ 310.0 K (37°C) Tissue Density (ρ)+ 1060 kg/m3 Thermal Conductivity @ 37.0°C (k)+ 0.5020

W/°C-m Tissue Heat Capacity (C)+ 3600 J/kg-°C Tissue Electrical Conductivity @ 310.0 K (σ)x

0.148 S/m Blood Density (ρb)* 1000 kg/m3 Blood Heat Capacity (Cb)* 4180 J/kg-°C Perfusion Coefficient (ω)* 6.4 × 10-3 1/s

Current Work Performing research on conductive polymers and

finding some "real" numbers in respect to heat. poly-acetylene polythiophene

Designing a prototype for our project that is constantly updated according to needs of our ever-changing design.

Designing connection from RF generator to catheter.

Applying ablation equations to determine radius of cauterization based on a power of 200 Watts.

Future Steps

Further research biomaterials for production of catheters.

Create prototype in CAD TEST IN COW LIVER!!! Approach VU individuals about catheter

connections and general electrophysiology.

Proof of Concept