Ethylcellulose-stabilized fat-tissue phantom for quality assurance in clinical hyperthermia

Abstract

Background

Phantoms accurately mimicking the electromagnetic and thermal properties of human tissues are essential for the development, characterization, and quality assurance (QA) of clinically used equipment for Hyperthermia Treatment (HT). Currently, a viable recipe for a fat equivalent phantom is not available, mainly due to challenges in the fabrication process and fast deterioration.

Materials and methods

We propose to employ a glycerol-in-oil emulsion stabilized with ethylcellulose to develop a fat-mimicking material. The dielectric, rheological, and thermal properties of the phantom have been assessed by state-of-the-art measurement techniques. The full-size phantom was then verified in compliance with QA guidelines for superficial HT, both numerically and experimentally, considering the properties variability.

Results

Dielectric and thermal properties were proven equivalent to fat tissue, with an acceptable variability, in the 8 MHz to 1 GHz range. The rheology measurements highlighted enhanced mechanical stability over a large temperature range. Both numerical and experimental evaluations proved the suitability of the phantom for QA procedures. The impact of the dielectric property variations on the temperature distribution has been numerically proven to be limited (around 5%), even if higher for capacitive devices (up to 20%).

Conclusions

The proposed fat-mimicking phantom is a good candidate for hyperthermia technology assessment processes, adequately representing both dielectric and thermal properties of the human fat tissue while maintaining structural stability even at elevated temperatures. However, further experimental investigations on capacitive heating devices are necessary to better assess the impact of the low electrical conductivity values on the thermal distribution.

Keywords:

• Hyperthermia
• microwaves
• quality assurance
• phantom
• ethylcellulose

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Raw data were generated at Chalmers University of Technology, Göteborg, and Eramsus MC, Rotterdam. Derived data supporting the findings of this study are available from the corresponding author H.D.T. on request.

Additional information

Funding

This research was funded by the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie (MSCA-ITN) grant “Hyperboost” project, no. 955625, the Swedish Research Council grant number 2021-04935, an STSM grand under COST Action MyWAVE CA17115 and the Royal Irish Academy.