Interstitial ultrasound applicators for localized thermal coagulation of tissue

Two interstitial ultrasound applicator design configurations were evaluated for high-temperature thermal therapy using computer simulations, acoustic beam measurements, and in vivo temperature measurements. Simulated transient temperature rises and cumulative thermal dose distributions indicate that these applicators can produce target temperatures greater than 50/spl deg/C and corresponding thermal doses greater than 300-600 EM43/spl deg/C within 5 min at a radial depth of 1 cm in moderately perfused tissues. Temperature distributions achieved with prototype applicators in vivo were in good agreement with theoretical calculations, and further demonstrate that the devices are practicable, sufficient power output levels can be obtained, and heating profiles can be shaped to protect non-targeted critical normal tissues. This preliminary study demonstrates that these interstitial ultrasound applicators have potential to provide controlled thermal ablation (necrosis) of small cancerous lesions, and deserve further investigation for possible implementation in sites such as prostate and brain.