biotransport education: thermal therapies
DESCRIPTION
Biotransport Education: Thermal Therapies. John Pearce, Temple Foundation Professor Electrical & Computer Engineering The University of Texas at Austin. Acknowledgment & Objective. Partial funding: the T.L.L. Temple Foundation, Motivation: Dr. Leslie Geddes (1928 - 2009), - PowerPoint PPT PresentationTRANSCRIPT
Biotransport Education: Thermal Therapies
John Pearce,
Temple Foundation Professor
Electrical & Computer Engineering
The University of Texas at Austin
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.
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.
tcTt
kT qgen qmet wtcb Ta T Bioheat Eqn.
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:
CEM43 Rcem43 T t
0
dt
S
N0 t
e
t t0D0 T e
CEM43
D0 43 e C t C 0
Theory of Absolute Reaction Rates:
lnC t C 0
A e
ERT
0
dt
Rcem 2
1e
E
RT1T2
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.
Diathermy Models
Capacitive Applicator Inductive Coil (w/ perfusion)
Qgen: 0 - 1000 (W/m3)
T@14 m: 32 - 46 (C)
T@30 m: 37 - 42 (C)
Qgen: 0 - 250000 (W/m3)
Hyperthermia models
CHO cells Disk electrode, T = 37 - 62C
Damage: 10, 63.2, 90% CEM43: 30, 60, 90 min.
CEM43 Rcem43 T t
0
dtP % 100 1 e
Sq. CAUnheated Heated
Cardiac Ablation Models
Cooled bipolar elliptical Atricure Squares
20s
T: 35 - 90 C Damage: 10, 63.2, 90%
90s90s
20s
Moving monopolar electrode 1,0 u exp ln A Eact
RT ln Ux
Electrosurgery models
Vessel sealing:Bipolar forceps electrodes
2 mm x 6 mmCartesian model
Qgen x 109
(W/m3)
Problem: Comsol can’t model equilibrium boiling processes.
log10{Qgen}
Corneal shrinkage:Needle electrode
0.5 mm x 2 mmCylindrical model
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.