Treatment planning for capacitive regional hyperthermia

• Published in: International journal of hyperthermia Vol. 19; no. 1; pp. 58 - 73
• Main Authors: Kroeze, H., Van de Kamer, J. B., De Leeuw, A. A. C., Kikuchi, M., Lagendijk, J. J. W.
• Format: Journal Article
• Language: English
• Published: London Informa UK Ltd 2003; Taylor & Francis
• Subjects: Biological and medical sciences; Capacitive; Electromagnetic Fields; Ethnic Groups; Humans; Hyperthermia, Induced; Induced hyperthermia. Cryotherapy; Medical sciences; Models, Biological; Pelvic Neoplasms - therapy; Phantoms, Imaging; Regional Hyperthermia; Sar; Somatotypes; Temperature; Therapy, Computer-Assisted - methods; Thermography; Treatment Planning System; Treatment with physical agents; Treatment. General aspects; Tumors; Temperature; Treatment; Simulation model; Mathematical model; Treatment planning; Induced hyperthermia; Localized; Test object
• ISSN: 0265-6736; 1464-5157
• DOI: 10.1080/02656730210158464

Capacitively coupled hyperthermia devices are widely in use, mainly in Asian countries. In this paper, a comprehensive treatment planning system, including a Specific Absorption Rate (SAR) and thermal model for capacitively coupled hyperthermia, is described and demonstrated using a heterogeneous patient model. In order to accurately model a hyperthermia treatment, simulation at high resolution is mandatory. Using the quasi-static approximation, the electromagnetic problem can be solved at high resolution with acceptable computational effort. The validity of the quasi-static approximation is demonstrated by comparing the Maxwell solution of a phantom problem to the quasi-static approximation. Modelling of capacitive hyperthermia of the prostate reveals the difficulty of heating deep-seated tumours in the pelvic area. Comparison of the SAR distribution in the heterogeneous patient model and a patient shaped agar phantom shows a shielding effect of the pelvic bone and the influence of the fat-muscle distribution. It is shown that evaluation of capacitive hyperthermia with agar phantoms leads to overly optimistic conclusions. Therapeutic relevant tumour temperatures can only be obtained by permitting temperature extrema in normal tissue. This concurs with clinical practice, where treatment-limiting hot spots restrict the tumour temperature. It is demonstrated that the use of very cold overlay bolus bags has only a very superficial effect. The presented model can be used for individual treatment planning and optimization, for the evaluation of capacitive applicator modifications and comparison with other devices.