Field penetration of arrays of compact applicators in localized hyperthermia

Abstract

The three-dimensional analysis of a range of new compact applicators indicates that there is an optimum operating frequency for maximum depth of field penetration and a given applicator size. The prospect of obtaining increased penetration depth by deploying more than one applicator is considered and assessed for an equi-phase array of compact applicators arranged symmetrically around a cylindrical shaped volume of uniform muscle phantom material; field penetration curves enable the maximum cross-section that can be heated to be assessed. Experiments at 200 MHz and results from a three-dimensional analysis demonstrate the usefulness of the assessment and establish that in multi-applicator configurations the field penetration decreases markedly for cross-sectional diameters in excess of 10 cm. However, the three-dimensional analysis for four applicators also shows that more uniform fields are obtained in the muscle phantom when it is surrounded by a low loss bolus region. In conclusion the clinical implications of the investigations are briefly discussed.

Key Words:

• hyperthermia
• penetration depth
• applicators
• arrays