Johnston, R., Ph. D.; Blight, D.; Kouzmanoff, J., MSEE

Labthermics Technologies, Inc.

Champaign, Illinois, USA

There are distinct advantages in using ultrasound energy to heat breast tissues. As can be seen on diagnostic ultrasound scans of the breast, ultrasound energy is preferentially absorbed by tumor tissue components and to a lesser extent by normal tissues. This is due in part to higher collagen and protein content in tumors. In contrast, microwave energy produces higher temperatures in high resistance tissue, such as fat, and less heating in more electrically conductive tissues, including tumor. An additional advantage of ultrasound is a selectable depth-dose" of the heating beam. By changing frequency of the ultrasound energy, we can chose a heating profile that matches depth and thickness of the tumor.

A new ultrasound therapy system has been built that maximizes the therapeutic benefits of ultrasound. The system uses 16 wedge shaped transducer elements to match variable geometries of breasts and tumor locations. These elements can be driven at multiple simultaneous ultrasound frequencies to yield a truly three-dimensional heating beam. Ultrasound energy is directed tangentially to the chest wall in order to minimize heating of ribs or intercostal muscles.

In use, the patient lies on her side with the breast over a water-filled pillow on top of the treatment array. An attached ultrasound diagnostic scanner images the breast from above. A computer stores the scans and builds a three-dimensional image of the treatment area, tumor locations, and temperature sensor locations. This information is given to the treatment-planning program. The therapy array is then electronically customized for the treatment plan. Additional diagnostic ultrasound scans can be taken during therapy to insure correct registration of patient position.

The system is presently in clinical animal trials at the University of Illinois. Applications to the FDA for human use will be made soon. The system has been designed to function as a stand-alone therapy unit or as configurable modules for the present SONOTHERM Ultrasound Hyperthermia System.