Optimization of tumor ablation volume for nanoparticle-mediated thermal therapy

Abstract

Nanoparticle-assisted thermal therapy for therapeutic tumor specific heating is emerging as a promising, minimally-invasive future cancer treatment. For efficient ablation of a tumor with minimum damage to the healthy tissue, the controlling factors must be optimized a-priori. In this study, a two dimensional tissue domain, comprising tumor diameters from 1 cm to 3 cm, were used to optimize the controlling factors of tumor ablation volume. In particular, irradiance, irradiation duration and particle volume fraction were varied to optimize the thermal damage (i.e. calculated from the Arrhenius equation in combination with Pennes' bioheat model). Taguchi's full factorial approach was used with an L27 orthogonal array for the controlling factors. The ‘nominal-the-best’ approach was implemented to target the optimal ablation volume for each tumor size. The results show that ablation volume increases from irradiance level of 0.75 W/cm2 to 1.50 W/cm2, irradiation duration of 70–80 s to 120–130 s and from a particle volume fraction of 0.00001% to a volume fraction of 0.0001% (i.e. from low to high levels for each parameters) for each tumor size. It was also found that these controlling factors showed the highest gradients for larger tumor diameters. Among the controlling factors, irradiance emerges as the significant factor, with a pronounced effect on tumor ablation volume. Ultimately, the study shows that this approach can be used to define a precise set of controlling factors (specific for each tumor size) to achieve the target ablation volume with minimum variation, resulting in an efficient thermal therapy.