Multi-criterion optimization of invasive antenna applicators for Au@Fe3O4, Au@-Fe2O3 and Au@-Fe2O3 mediated microwave ablation treatment.

Abstract

Magnetic nanoparticle (MNP) mediated microwave ablation has the great potential at present to address challenges associated with treatment planning such as maximum heat generation in the vicinity of targeted tissues in lesser penetration time. Further, the antenna applicators injected in human phantom must be rigid and thin. The derivative-free optimization algorithms are carried out for optimum design of monopole, slot, dipole, and tapered slot antenna applicators for ablation of tumour tissues invasively. It is found that in terms of input impedance matching, the used multi-criterion Nelder-Mead optimization performs efficiently for tapered slot applicator achieving S₁₁ value of -40 dB with much reduced antenna dimensions. In order to further escalate the performance of tapered slot antenna, gold (Au)-coated iron-based MNPs are suggested for tumor infusion. Spherical gold-coated shell material is preferrable for more sphericity of ablation zone, biocompatibility and due to high conductivity, heat generated in MNPs can be transferred to biological tissues more rapidly. The size, type, and shape of MNPs also influence the heat generation in tumor tissues. Thus, three different types of MNPs having high magnetization properties, Au@Fe₃O₄, Au@$\alpha$-Fe₂O₃ and Au@$\gamma$-Fe₂O₃ have been employed to study the performance in terms of maximum rise in temperature, specific absorption rate (SAR), and area of ablation zone by varying core size radius of MNPs. Results demonstrate that increase in radius of MNP core helps in increasing the temperature distribution and reduction in ablation zone. The optimized lesion is achieved for 20 nm core radius of Au@Fe₃O4.