Regional Hyperthermia with an Annular Phased Array in the Experimental Treatment of Cancer: Report of Work in Progress with a Technical Emphasis

The annular phased aray (APA)1 has been under study at the University of Utah since late 1980. The prototype instrument was upgraded to its present configuration by April 1982. Its clinical engineering features and application are described. As of December 1982, 46 patients have been treated in a feasibility study to evaluate the use of the APA in inducing experimental regional hyperthermia for the treatment of advanced abdominal and pelvic cancer. Extensive temperature measurements from tumors and normal tissues were performed. With a few exceptions, the APA appeared capable of delivering power to deep-seated tumor volumes, but data pertaining to power distributions were scanty. Adjustment of the patient position within the aperture to achieve uniform heating is a significant problem. Treatment results are considered encouraging and there were no significant complications, but firm conclusions regarding tumor responses cannot be drawn from a study of this kind. Further studies of methods to predict power deposition patterns are needed if complications are to continue to be avoided in the more aggressive potentially curative treatments that may need to be employed in future studies.