1. Biotransport Education: Thermal Therapies John Pearce, Temple Foundation Professor Electrical & Computer Engineering The University of Texas at Austin

2. Acknowledgment & Objective Partial funding: the T.L.L. Temple Foundation, Motivation: Dr. Leslie Geddes (1928 - 2009), ECE Department allows me to teach my course (even years): EE 385J Topic 26 / BME 381J Topic 5 “Therapeutic Heating” Objective: Motivate coursework in this arena because prediction of tissue effects is a more appropriate endpoint than temperature fields alone.

3. Approach Topics range from low temperature diathermy and tumor hyperthermia to ablation and electro- surgery, Heavy reliance on purpose-generated course notes (lack of a textbook), Primary heating modalities are electromagnetic, Use FEM numerical models (Comsol) to compare and contrast the development of irreversible thermal alterations in tissues. Bioheat Eqn.

4. Now for something completely different... “It is interesting to listen to an Electrical Engineer explain Chemical Engineering to Mechanical Engineers.” Gene Wissler, ASME 1991 Annual Conference, Dallas TX. I’m very grateful that he didn’t say “mess up”. Theory of Relative Reaction Rates: Theory of Absolute Reaction Rates:

5. Comsol FEM software Highly flexible and adaptable, Excellent drawing features, Multiphysics modes include: —Bioheat equation, —Quasi-static electromagnetic modes (complex properties), —Full wave equation solutions. Supports thermal damage process modeling: —Additional general Partial Differential Equation modes may be superposed as desired.

6. Diathermy Models Capacitive Applicator Inductive Coil (w/ perfusion) Q gen: 0 - 1000 (W/m 3 ) T@14 m: 32 - 46 (C) T@30 m: 37 - 42 (C) Q gen: 0 - 250000 (W/m 3 )

7. Hyperthermia models CHO cellsDisk electrode, T = 37 - 62C Damage: 10, 63.2, 90% CEM 43 : 30, 60, 90 min. Sq. CA Unheated Heated

8. Cardiac Ablation Models Cooled bipolar ellipticalAtricure Squares 20s T: 35 - 90 C Damage: 10, 63.2, 90% 90s 20s Moving monopolar electrode

9. Electrosurgery models Vessel sealing: Bipolar forceps electrodes 2 mm x 6 mm Cartesian model Q gen x 10 9 (W/m 3 ) Problem: Comsol can’t model equilibrium boiling processes. log 10 {Q gen } Corneal shrinkage: Needle electrode 0.5 mm x 2 mm Cylindrical model

10. Conclusions Course notes provide an effective basis for the course, A disappointing fraction of students are facile in electromagnetics and/or thermodynamics, The Comsol commercial FEM package has adequate power to effectively support the many diverse aspects of the class, The FEM numerical models are an outstanding positive feature of the overall pedagogy.