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Cauterization Cauterization CatheterCatheter
Brad Wood, M.D.Brad Wood, M.D.Charles BlythCharles Blyth
Cristina FernandezCristina FernandezScott HittingerScott HittingerCameron JonesCameron JonesBrian McGeeBrian McGee
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.