Page 271 - Computational Modeling in Biomedical Engineering and Medical Physics

260 Computational Modeling in Biomedical Engineering and Medical Physics

Figure 8.4 The FEM mesh made of B450,000 tetrahedral, quadratic, and Lagrange elements. FEM,
Finite element method.

are solved first, only once, independently, and sequentially. For the BHT analysis, the prop-
erties are independent of temperature hence the electrokinetic is solved once, in the
beginning.
The electric current density provided by the trocar electrodes is seen in Fig. 8.5A.
The blood flow presented in Fig. 8.5B and C (Morega et al., 2020) is driven by 49
kPa pressure drop (arterial entrance to the venous exit), which is consistent with avail-
able experimental data (Layton, 2013; Peralta et al., 2006).
The RF procedure may be successful provided that the temperature of the targeted

ROI is increased to atleast 45 C—a critical threshold. The total (Joule) power
received by the tumor is 0.141 W, in the BHT model, and 0.149 W in the GHT one.
This slight discrepancy may be caused by the electric current density distribution in
the two models. They may be due to the electrical conductivities of blood and renal
tissue, which are different.
Figure 8.6 shows the critical isotherm of 45 C, which contains part of the tumor

volume (the tumor surface is rendered in green), and the inner isotherms of 60 Cand

80 C after approx. 10 min. The progression of the ablated volume may be evaluated by
using the Arrhenius model discussed earlier, in this chapter. The two models cast differ-
ent predictions. Whereas the BHT may suggest that the tumor is completely ablated,
the GHT model shows off that only part of the tumor is well addressed. In both situa-
tions, the critical isotherm (45 C) contains the volume prone to ablation, consisting of

either part (GHT) or the entire (BHT) tumor and also some neighboring, healthy tissue.
Depending on the specific conditions, a second electrode array or a better positioning of
the electrode array may be advised to reduce the side effects. However, due attention
should be devoted to avoiding excessive, unneeded healthy tissue damage.