Heating patterns of cylindrical ultrasound transducers for breast tumors

The purpose of this paper is to examine the optimal driving frequency and to configure the ultrasound energy deposition schema for a various size and location of breast tissues when a portion or the entire cylindrical ultrasound transducer is employed for breast hyperthermia treatments. This work employs a computer simulation program based on an ideal ultrasound power deposition from a cylindrical transducer. The distribution of specific absorption rate (SAR) ratio is employed to determine the heating pattern of a set of given parameters. The control parameters considered are the ultrasound frequency in the breast tissue, the active portion of cylindrical transducer, and the shifting distance between the central axes of the breast and the transducer. The effect of the breast size on the SAR ratio is also considered. Simulation results demonstrate that the breast size, the ultrasound frequency in breast tissue, the shifting distance and the active portion of cylindrical transducer are the potential parameters for influencing the distribution of SAR ratio. The distribution of SAR ratio indicates the domain of treatable tumor size and tumor depth for a given set of parameters (driving frequency, shifting distance and active portion of transducer, as well as breast diameter).