An Automated Dosing Method for a HIFU Device Containing Multiple Phased Arrays

A device containing multiple 2D therapeutic and imaging ultrasound phased arrays is proposed for acoustic hemostasis applications. An automated dosing algorithm selects the optimal combination of therapeutic phased arrays and calculates the acoustic power required of each array. Simulations demonstrate that therapeutic temperatures (70'C < T < 95'C) are achieved over a tissue depth range with highly localized heating, minimizing damage to surrounding tissue. The device has the 2D arrays mounted in panels that embody a cuff, patch or blanket type device. Using array and tissue target positions, an algorithm automatically estimates the available power at the target using depth, beam steering angles, directivity and the tissue properties. The individual array powers are then assigned using a power balance (equalization) algorithm that adjusts the size and shape of the heated target region. The treatment volume is adjusted by dynamically scanning the individual foci through patterns in the target zone. The temperature elevation was simulated using 3D finite element models. Numerical simulations were performed on the therapeutic performance of the device. The surface acoustic intensity of the arrays was maintained below a threshold associated with avoidance of skin burning. The total absorbed power in the target volume (8 mm diameter spherical target) producing therapeutic temperatures was 4 to 5W for 30 second continuous dosing times. The spatial-peak-time-averaged intensity in the target focal zone was -600W/cm2, below the inertial cavitation threshold for these conditions. Simulations showed that the proposed ultrasound device yielded a relatively uniform temperature distribution in the target volume.