Page 292 - Computational Modeling in Biomedical Engineering and Medical Physics

Hyperthermia and ablation 281

The computational domain was built large enough for its boundary to remain in thermal

equilibrium (at 37 C, or adiabatic) with the outside, that is, the cooling effect provided by
the perfusion (convection) term in Eq. (8.12) is large enough.
Microwave interstitial hyperthermia is applied to heat the tissue in two situations: in
the absence of MNPs (regular hypethermia) and the presence of MNPs (magnetic
hyperthermia). It is further assumed that the MNPs are attached to the tumor only.
Consequently magnetic heating occurs at the tumor level only, whereas electric heating
21 3
happens inside and outside the tumor. The concentration of the MNPs is n 5 10 /m ,
their susceptibility χv 5 65, and the hydraulic radius r 5 18 nm (Urdaneta, 2015). As
stationary solutions (EMF and heat transfer) are aimed, an iterative, segregated solver
may be used to solve the problems (8.10) (electric field) and (8.22) please call it (heat
transfer, stationary form). The temperature distribution is within a relatively tight inter-
val, therefore the electric, magnetic, and thermal properties may be assumed constant.
Figure 8.23 shows the stationary temperature profiles along a horizontal line drawn
between antennas and passing through the tumor (see Fig. 8.22), along its horizontal
diameter, for three power levels (1.2, 1.4, and 1.6 W) per antenna port. In all cases,
the presence of the 6 mm wide MNP-magnetized inclusion is identifiable using the
lateral maxima of the temperature curves.
Moreover, the presence of MNPs is seen to require lower levels of exposure (the
almost same effect is noticed for 1.4 W, with magnetic work, as of 1.6 W, without
magnetic work), and better, deep heating of the tumoral volume.
Patient-specific information may be needed when adequately planning the proce-
dure. Among other input data, the actual organ of concern has to be considered. Its
“geometry” may be extracted out of medical scans, and reconstruction techniques

Figure 8.23 The temperature along a horizontal line, between the antennae (Fig. 8.22), with (blue)
and without (red) magnetic nanoparticles.