Analysis of the Influence of Phantom Design in Superficial Hyperthermia Quality Assurance Procedures

Oncological radiative hyperthermia (HT) is a therapeutic technique used as an adjuvant in cancer treatments. Depending on the tumour depth, it is named superficial or deep HT. This study focuses on superficial hyperthermia, evaluating critical aspects of quality assurance (QA) procedures to understand their implications for treatment effectiveness. QA protocols involve temperature measurements in non-perfused tissue equivalent phantoms to assess HT device performances. An analytical formulation of the transient bioheat transfer equation, supported by numerical and experimental results, examines the electromagnetic-thermal phenomenon in perfused and non-perfused tissues, analysing stability, heating-up times, and thermal response evolution. Results show that the absence of blood perfusion significantly influences the transient thermal behaviour and temperature distribution, with time-dependent effects. A numerical study explores the temperature distributions induced by an electromagnetic source in a multilayered phantom replicating the QA setup. The influence of dielectric and thermal properties of the materials making the phantom on the QA parameters, such as temperature rise (TR), thermal effective field size (TEFS), and thermal effective penetration depth (TEPD), is assessed. Simulations reveal the impact of thermal properties on temperature profiles, highlighting the importance of designing phantoms with properties representative of real tissues.