1. Cauterization Catheter – An Advancement in Conductive Biomaterials and Medicine C. Blyth 1, C. Fernandez 1, S. Hittinger 1, C. Jones 1, B. McGee 1, B. Wood 2 1 Vanderbilt University, Nashville, TN; 2 NIH, Bethesda, MD Catheter Use Catheters are used in medical operations to enable access for drainage, fluid injection or surgical instrument access. Catheters are frequently utilized after a nephrostomy and/or biliary tube procedure is performed. These catheters drain the bile from the gallbladder and urine from the kidneys before, during, or after surgery. Surgical work in these organs necessitates catheters to ensure proper drainage. Heat Transfer State of Design IntroductionAblation Techniques We have finished our designs for catheter and adapter for connection to the RF generator and CAD models have been created. The catheter model in CAD is finished, but crucial questions arose that had to be answered before proceeding with the RF generator connection. Connecting the catheter to the RF generator has proposed design considerations that have delayed development. We will be working to finish this design in CAD. CAD design has been finished for the catheter. We have considered mathematical modeling for our system to access the power lost through the insulated shaft of the catheter. We discovered that this model will be very difficult to accomplish and have resolved to use a homogeneous tissue model where power will dissipate in a 1/R 2 manner. Where R is the distance away from the source. Model manufacturing will begin as soon as time allows. Background The liver and kidney are highly vascularized organs that receive their blood supply from the hepatic portal vein, hepatic artery, nephrons. When inserting tubing into these organs, there is a high risk of internal bleeding resulting in blood loss, tissue damage and potentially death. Each year, there are approximately 430,000 new cases worldwide of liver disease alone. However, individuals with deleterious health conditions are frequently denied these procedures because of their increased susceptibility to adverse outcomes. In fact, 1 – 3.6% of these new cases have complications of internal bleeding. This results in 430 - 15,480 people turned down due to elevated risks. Problem Statement To better serve those individuals turned down because of elevated risks, a flexible catheter capable or reducing blood loss most be designed. This problem necessitates the use of conductive polymers to transmit the radiofrequency capable of cauterizing the vascularized tissue immediately surrounding that catheter effectively stopping the bleeding entirely before removal. Reasonable goals are to obtain 0 -.2g of blood loss 0 – 1mL of blood loss during these procedures. Cauterization is the process by which high frequency waves are used to denaturize proteins within tissue in order to induce coagulation. This process of cauterization was first performed with burning logs of fire and proceeded to a 2 nd generation of cauterization techniques which utilized heated metals. The current therapeutic techniques are based upon electrocautery and use high frequency RF pulses to accomplish such cauterization within the human body for procedures such as biopsies and tumor ablation. Cauterization P = h (dT/dt) h = c * w c = specific heat = 3600 J/(kg K) w = weight of treated tissue Density = 1060 kg/m3 Goal is to cauterize tissue within1 mm radius from electrodes over the course of 1 to 5 seconds Power calculations require using an electrode length ranging from 1 to 2 cm RF Ablation Some Values to Apply to Models Power = 200 W with a resistance of 50 ohms and current 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 RF ablation is a technique that bakes internal tissue using radio frequency waves. RF waves are transferred by microelectrodes to tissue where the frictional movement of ions generates thermal energy. As a result, proteins are denatured and cells destroyed (target temperature of 75 degrees Celsius for total protein denaturization.) The Collagen/Fibrin Plug – Injection of collagen and fibrin, the precursors for the blood clotting cascade, is very cumbersome and tedious for the doctor performing the procedure. RF Pulse – Used for biopsy tracts through the conductance of the metal needles used in the operating room. Prototype Design Plastics allow for flexibility and mobility Conductive polymers poly – acetylene poly – thiophene Polyurethane/Silicone base insulation Resistivity and Conductivity – main parameters for acquisition of target temperatures, power distribution, and overall performance. Prototype Design