Practical Implementation of Quality Assurance Guidelines for Hyperthermia Therapy

Licentiate thesis, 2023

Hyperthermia therapy (HT) has been proven to be a potent enhancer of chemotherapy and radiotherapy in numerous clinical trials. The effectiveness of HT is strictly dependent on the administered thermal dose, which, in turn, is dependent on the quality of the therapeutic heat applied to the patient. Quality Assurance (QA) protocols in HT exist to ensure that heating devices can consistently deliver controlled, reproducible, and high-quality treatments.
 The physical characterization of HT devices requires specific procedures and instrumentation as well as adequate tissue-mimicking phantoms to perform QA experimental procedures. However, the implementation of QA guidelines is hampered due to the unavailability of suitable phantom materials and limited equipment for the QA experimental evaluation. This work addresses these gaps by (i) proposing the design of tissue-mimicking materials for routine use in HT QA procedures and (ii) demonstrating the practical implementation of the latest QA guidelines for both superficial and deep HT.
 A novel fat-mimicking material was developed to mimic superficial fatty tissue. This fat phantom is based on an ethylcellulose stabilized glycerol in oil emulsion and is intended to be used in superficial HT QA procedures. Measured dielectric and thermal properties were consistent with fatty tissue properties, with an acceptable variability in most of the frequency range used in HT. This fat-mimicking material was then used in the experimental implementation of HT guidelines. The physical characterization of a superficial HT device (Lucite Cone Applicator, LCA) was conducted by assessing the quality metrics defined in the HT guidelines, demonstrating acceptable performance. These findings were further validated through computational studies.
For deep HT, a comparative study engaged six HT centers across Europe to assess the performance of commonly used deep regional heating devices. Preliminary results in experimental phantoms showed a good performance in terms of device heating capability and steerability. This study provided practical insights into implementing QA guidelines involving phantom properties, experimental setup, temperature acquisition, and time constraints. We are positive this research will benefit the routine implementation of deep HT guidelines in a clinical setting.