THERMAL AND STRUCTURAL MODELING OF ARTERIES SUBJECTED TO SUB ZERO TEMPERATURE CONDITIONS PROJECT BY KARAN PRADEEP ARVIND C.J KARTHIK KUMAR B NAJUMUDEEN A UNDER THE GUIDANCE OF Dr.N.V.MAHALAKSHMI

INTRODUCTION

ARTHEROCLEROSIS Deposition of fat - Plaque Deposition of fat - Plaque Clogging of arteries Clogging of arteries Reduces blood flow to the legs and feet Reduces blood flow to the legs and feet Increases risk of Increases risk of  Infection  Leg ulcers  Gangrene  Amputation.

METHODS FOR THE TREATMENT OF ARTHEROCLEROSIS Lifestyle changes & medication Lifestyle changes & medication Bypass surgery Bypass surgery Angioplasty Angioplasty  Insertion of balloon into the artery.  Passing of saline water. Stents Stents Placement of alien body as support Placement of alien body as support Cryoplasty therapy Cryoplasty therapy

CRYOPLASTY Catheter balloon material Catheter balloon material  expanded PolyTetraFluoroEthylene  Diene polymer Usage of nitrous oxide Usage of nitrous oxide Temperature -10 to C Temperature -10 to C Inside pressure 6 bar Inside pressure 6 bar Time for treatment is 50 seconds Time for treatment is 50 seconds

APOPTOSIS Programmed cell death - induced within a precisely defined temperature zone. Programmed cell death - induced within a precisely defined temperature zone. Too low temperatures may result in necrosis Too low temperatures may result in necrosis Injury - cellular inflammation, cell proliferation, and restenosis. Injury - cellular inflammation, cell proliferation, and restenosis. Temperatures that are not cold enough have little or no effect Temperatures that are not cold enough have little or no effect

LITERATURE SURVEY & SCOPE OF THE PROJECT

LITERATURE SURVEY IN VITRO STUDIES OF ARTERIAL FREEZING INJURY by James D. Joye, DO, FACC and Kristine Tatsutani, Ph.D FEASIBILITY AND SAFETY OF A NOVEL CRYOPLASTY TM SYSTEM by Mitsuyasu Terashima, Yasuhiro Honda1, Frederick St. Goar, Margaret Yoklavich, Paul G. Yock, Peter J. Fitzgerald CRYOPLASTY PROCEDURE PROPOSED MECHANISMS OF ACTION by Kristine Tatsutani, PhDPrinciple Scientist, Cryobiologist CryoVascularSystems, Inc. Current research topic in Current research topic in 1. Texas A & M University 2. University of Minnesota, Twin cities

SCOPE OF PROJECT Lack of clear understanding of the mechanism restricts its usage to peripheral arteries Lack of clear understanding of the mechanism restricts its usage to peripheral arteries Most of the present research in this field is concentrated on 1-D analysis Most of the present research in this field is concentrated on 1-D analysis No particular focus on the thermal effects of cryoplasty on the artery walls. No particular focus on the thermal effects of cryoplasty on the artery walls. A 2-D analysis would serve to identify any high stress level due to the sub-zero temperature A 2-D analysis would serve to identify any high stress level due to the sub-zero temperature

PHASE I SIMPLIFIED MODEL

ASSUMPTIONS 1. Properties of artery walls are same as that of water. 2. Length of the artery in contact with the catheter balloon alone is considered. 3. The effects of the following are ignored Plaque Plaque Flow of nitrous oxide Flow of nitrous oxide Balloon material Balloon material Radiation and convection Radiation and convection Thermal expansion and contraction Thermal expansion and contraction 4. Temperatures considered Initial temperature 37 o C Initial temperature 37 o C Outer surface temperature 37 o C Outer surface temperature 37 o C Inner surface temperature -20 o C Inner surface temperature -20 o C

MATERIAL PROPERTIES - CONDUCTIVITY Conductivity values of ice and water from Heat and Mass transfer data book Conductivity values of ice and water from Heat and Mass transfer data book

MATERIAL PROPERTIES - ENTHALPY Formulation of enthalpy values for phase change material, water. Formulation of enthalpy values for phase change material, water. Arbitrary datum, enthalpy h = 0, at T1=-20 o C Arbitrary datum, enthalpy h = 0, at T1=-20 o C At T2 =0 o C, At T2 =0 o C, h2 = h1 + ρ( Cp ice)(T2 – T1) = J/m3 h2 = h1 + ρ( Cp ice)(T2 – T1) = J/m3 At T3 = 0.5 o C, At T3 = 0.5 o C, h3 = h2 + ρ( Cp ice,water)(T3 – T2) + ρh sl = J/m3 At T4 = 20 o C, At T4 = 20 o C, h4 = h3 + ρ( Cp water)(T4 – T3) = J/m3 h4 = h3 + ρ( Cp water)(T4 – T3) = J/m3Where  Cp ice = 2261 J/kg K  Cp water = 4216 J/kg K

MATERIAL PROPERTIES - ENTHALPY Enthalpy values used to simulate the effects of phase change Enthalpy values used to simulate the effects of phase change

DESIGN – 2D MODEL Inside part (Lumen of artery) 6 mm 3 mm

DESIGN – AXISYMMETRIC MODEL AXISYMMETRY L R2 = 6mm L t = 3mm R1 = 3mm

RESULTS CONTOUR PLOTS 2D MODEL

CONTOUR PLOTS AXISYMMETRIC MODEL

GRAPHICAL COMPARISON ALONG THE RADIUS

TEMPERATURE DISTRIBUTION GRAPH ALONG THE AXIAL DIRECTION

CONCLUSIONS Temperature distribution along any radius is the same. Temperature distribution along any radius is the same. Temperature distribution along the radial direction are the same for both the models. Temperature distribution along the radial direction are the same for both the models. Temperature distribution does not vary along the axial direction. Temperature distribution does not vary along the axial direction.

FUTURE PLAN Phase 2: Plaque layer and its effects on temperature distribution. Phase 2: Plaque layer and its effects on temperature distribution. Phase 3: Inclusion of the balloon layer. Phase 3: Inclusion of the balloon layer. Phase 4: Effects of flow of nitrous oxide on temperature distribution. Phase 4: Effects of flow of nitrous oxide on temperature distribution. Phase 5: Temperature distribution along axial direction Phase 5: Temperature distribution along axial direction Phase 6: Determination of the stress distribution. Phase 6: Determination of the stress distribution.

REFERENCES BOOKS BOOKS  Annual review of heat transfer, volume 9 By Chang L Tien By Chang L Tien  Heat conduction By Latif M Jiji  The CRC handbook of thermal engineering By Frank Keith  Heat and mass transfer data book By C P Kothandaraman and S Subramanyan WEB SITES WEB SITES    