Hyperthermia has been shown to be efficacious in the treatment of many tumors despite the limited capabilities of the available heating technologies, which have been constrained by the short history of modern clinical hyperthermia. One developing, non- invasive heating technology with the potential to tailor power deposition patterns to individual tumors and to allow multipoint temperature control is scanned, focussed ultrasound. We have developed such a system and propose (1) to perform phase 1 studies involving human tumors at a variety of locations to determine which tumors and sites can be effectively treated by this modality, (2) to develop a computerized treatment planning system to allow the ultrasound scanning pattern to be individualized and optimized for each patient, (3) to extend our current, single point feedback control system to a multipoint controller to give improved control over tumor temperature distributions, and (4) to perform animal experiments to obtain important knowledge concerning the interactions between ultrasound and normal and tumor tissues. The clinical studies will investigate the temperature distributions in different tumors and locations as a function of our system parameters (transducer choice, feedback algorithm, scanning speed and pattern), and the limitations of scanned focussed ultrasound imposed by pain and other normal tissue toxicity, abdominal gas, tissue inhomogeneities and interfaces, and the available utltrasonic treatment window. The treatment planning approach will use serial CT scans of the patient, pretreatment measurements of the tumor blood perfusion values and ultrasonic absorption coefficients, and computerized treatment simulations. The multipoint feedback control system will utilize the know locations of the temperature sensors to vary power as a function of position. The animal studies will investigate the possible utilization of nonlinear effects (including a determination of potential cavitation problems), the in vivo absorption coefficients in different tissues, the distortion of the high power ultrasound beam while passing through multiple tissues, and the power deposition at soft tissuebone and-gas interfaces. These studies will give a scientific basis for the improved design and application of scanned focussed ultrasound.
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