Thermal dosimetry studies of the Helios ultrasound hyperthermia system

SAR (specific absorption rate) distributions from the Helios, a multitransducer ultrasound hyperthermia system, were characterized in a tissue-equivalent phantom. Well-localized heating (FWHM of 3.5 cm) was obtained at the focal depth when the three inner transducer rings were set to converge at the focal plane. It was also possible to produce a well defined donut-shaped SAR pattern by opening the ring diameters. In-vivo trials in porcine thigh muscle, using the three inner transducer ring at a frequency of 540 kHz, showed an ability to achieve therapeutic temperatures at depths of 10 to 11 cm.<
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