The present invention provides a method and apparatus for delivering and controlling thermal therapy to a volume of diseased tissue. Specifically, the invention includes using thermal imaging and other inputs to determine an acoustic (ultrasonic) treatment regime employing interstitial ultrasound applicators to deliver a required therapeutic temperature or thermal dose to the affected region in a body or organ. Various aspects of the treatment that can be controlled include individual transducer element operating power and frequency, as well as the rate of cooling and rotation of the entire applicator.