Page 293 - Computational Modeling in Biomedical Engineering and Medical Physics

282 Computational Modeling in Biomedical Engineering and Medical Physics

(3DSlicer) and CAD constructs are used to build the computational domain, using
fusion techniques (Chapter 3: Computational Domains). The pair of MW antennae are
inserted to heat a spherical tumor volume (CAD constructs) of a 3 mm radius inserted
within a liver volume (reconstruction technique), Fig. 8.24. The same levels of power
are used, that is, 1.2, 1.4, and 1.6 W, for both regular and magnetic hyperthermia. The
same MNPs properties are used. For simplification, the bioheat model is used in the
entire domain.
To cope with the complex geometry of the domain, the computational domain is
FEM meshed using tetrahedral elements (unstructured mesh). First-order Lagrange ele-
ments are used to solve the electric field model and second-order elements for the
heat transfer problem.
Scattering (EMF) and adiabatic (heat transfer) boundary conditions on the surface
of the computational domain (the liver), and metabolic temperature as initial condition
close these coupled problems.
The two physics are solved sequentially, first the electric field, Eq. (8.10), and then the
thermal field, Eq. (8.22), in its stationary form. Because here the material properties are
assumed to be temperature-independent, the two problems are one only way coupled. The
validity of the solution, of course, holds as long as this assumption stands, that is, for power
levels that induce small temperature gradients in the ROI subjected to MW heating.

Figure 8.24 The computational domain constructed using image reconstruction (the liver) and
CAD blocks (the antennae and the tumor). The isotherms of 39 C, 43.641 C, and 48.068 C.