Cauterization Catheter Brad Wood, M.D. Charles Blyth Cristina Fernandez Scott Hittinger Cameron Jones Brian McGee

Liver

Kidney

Catheter Use Nephrostomy and/or Biliary Tubes Nephrostomy and/or Biliary Tubes Drain the bile from the gallbladder before, during, or after surgery Drain the bile from the gallbladder before, during, or after surgery Drain the urine from the kidneys before, during, or after surgery Drain the urine from the kidneys before, during, or after surgery

Big Picture The liver and kidney are highly vascularized The liver and kidney are highly vascularized Hepatic portal vein, hepatic artery Hepatic portal vein, hepatic artery Bile duct (Liver) Bile duct (Liver) Internal bleeding during removal Internal bleeding during removal Individuals with problems need the procedure, but the procedure will be denied due to the risk of fatal internal bleeding Individuals with problems need the procedure, but the procedure will be denied due to the risk of fatal internal bleeding.1 – 3.6% of cases.1 – 3.6% of cases

Our Job Catheter to prevent bleeding upon removal Catheter to prevent bleeding upon removal Conductive polymer Conductive polymer Cauterization of tissue tract Cauterization of tissue tract 0 -.2g of blood loss 0 -.2g of blood loss 0 – 1mL of blood loss 0 – 1mL of blood loss

Cauterization Used mainly to coagulate tissue stopping bleeding Used mainly to coagulate tissue stopping bleeding First performed with burning logs of fire First performed with burning logs of fire 2 nd generation of cauterization techniques utilized heated metals 2 nd generation of cauterization techniques utilized heated metals Current therapeutic techniques are based upon electrocautery Current therapeutic techniques are based upon electrocautery

RF Ablation A technique that can bake internal tissue using radio frequency waves A technique that can bake internal tissue using radio frequency waves RF waves are transferred by microelectrodes to tissue where the frictional movement of ions generates thermal energy RF waves are transferred by microelectrodes to tissue where the frictional movement of ions generates thermal energy Proteins are denatured and cells destroyed Proteins are denatured and cells destroyed

Ablation Techniques Collagen/Fibrin Plug Collagen/Fibrin Plug Injection technique, cumbersome approach Injection technique, cumbersome approach RF Pulse RF Pulse Cauterization, tissue damage Cauterization, tissue damage Pritchard et al. “Radiofrequency Cauterization with Biopsy Introducer Needle”. Journal of Vascular Interventional Radiology Average blood loss Without Ablation:.30 grams With Ablation: grams

Prototype Design Plastics allow for flexibility and mobility Conductive polymers poly – acetylene poly – thiophene Polyurethane/Silicone base Resistivity and Conductivity

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

Heat Transfer Heat conduction equation governs heat transfer in transfer Important for determining effective ablation radius Difficult to model since most equations and models assume constant electric conductivity in tissue

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

Some Values to Apply to Models Power = 200 W with a resistance of 50 ohms and current of 2 amps RMS Power = 200 W with a resistance of 50 ohms and current of 2 amps RMS Ambient Temperature (Tamb) K (37°C) Tissue Density (ρ) kg/m3 Thermal 37.0°C (k) W/°C-m Tissue Heat Capacity (C) J/kg-°C Tissue Electrical K (σ)x S/m Blood Density (ρb)* 1000 kg/m3 Blood Heat Capacity (Cb)* 4180 J/kg-°C Perfusion Coefficient (ω)* 6.4 × /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