Steerable-beam therapeutic ultrasound for superficial heat treatments

A novel. movable beam therapeutic ultrasound applicator was fabricated and tested. Each element was individually powered and directed under computer control. Beam steering experiments were done in a water tank with a needle hydrophone. The elements moved under steppermotor control. Acoustic pressure measurements were compared to computed results for the cases of 0". 15" in and 15" out, at fixed angles. Power could be modulated during the excursion for each element. Measured results matched well with computed results and suggest that beam steering allows power control throughout the heated region. Water tank tests and perfused phantom experiments verified that the collimated acoustic beams were independently steenble and that shaping of power deposition is possible with this system. Although the planar elements were 3.0 x 3.0 cm. rectangular and smaller elements, or non-planar could be ulilized. Also. lower frequencies (such as 0.5 MHz) or higher frequencies (3.0 to 4.0 MHz) could also be used in the same applicator to provide control over depth of penetration.