Abstract:
In this paper, a novel hybrid approach for treating deep localized tumors through strong obstacles (e.g., the rib cage) using ultrasound phased arrays is presented. In view of the large problem wavelength dimensions, high-frequency techniques such as ray acoustics and diffraction techniques are used. In particular, a ray method is employed to propagate the ultrasound fields from the feeding array to the frontal plane of the rib cage where these fields are considered as the primary sources for the region below the ribs. The Rayleigh--Sommerfeld diffraction integral is then used to determine the fields in the lower region interior to the rib cage. The pressure-velocity relation is finally put into matrix form and the pseudo-inverse technique is employed to synthesize the heating pattern required for hyperthermia. The intensity levels over the solid ribs are also examined, as well as the field map under the hard obstacles, to ensure that the synthesized pattern satisfies the desired specifications. Experimental results are given which are in excellent agreement with the computational model and serve to validate the methodology. [Work supported by the National Institutes of Health.]