Development of a novel method to enhance the therapeutic effect on tumours by simultaneous action of radiation and heating

Abstract

Purpose: This paper describes the development of a new type of electromagnetic hyperthermia applicator delivering dose control within large application fields and increased effectiveness by providing simultaneous action of radiation and heating (SRH) in malignant tumours, and development of a dosimetric feedback method to support SRH. Materials and methods: Single and phased arrays of flexible applicators have been developed to allow simultaneous hyperthermia and external beam therapy. A frequency of 434 MHz is used to heat near-surface and moderately deep-seated tumours and 70 MHz for deep-seated tumours. Phase and amplitude control allows focusing of electromagnetic energy (EM) to deep-seated tumours. The specific absorption rate (SAR) dose distribution can be modified to achieve uniform heating of tumours with complex shapes and heterogeneous tissue properties. A lithium fluoride thermoluminescent dosimeter (TLD) in a flexible film cassette has been developed for real-time dose measurement. Results: Four types of 434 MHz applicators were manufactured with 3, 4, 9 or 12 independent applicators. Two types of 70 MHz applicators were made with 4 or 6 independent applicators. Phantom tests demonstrated the ability to control the SAR pattern by phase and amplitude control. Placement of the dosimeter between bolus and phantom increased the phantom surface temperature up to 3 °C and showed that the ratio of absorbed energy in TLD to dose in water approaches (0.83 ± 3%) for photon energies >60 keV. Conclusions: Simultaneous and controlled radiation and local hyperthermia is technically feasible in a preclinical setting, a clinical feasibility test is the next step.

• Gamma radiation
• hyperthermia
• phased array
• radiofrequency/microwave
• simultaneous radiation and heating
• TLD dose monitor

Acknowledgements

The authors thank V.P. Legonkih for assistance in carrying out the simulations.

Declaration of interest

This research was performed within the framework of International Science and Technology Center (ISTC) project 3996 with financial support of the EU. Dr Mazokhin is employed by Istok, the other authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.