This paper proposes an optima] many-core processor architecture that meets the requirements of low power and high performance for different ultrasonic image resolutions in hand-held ultrasonic devices. To identify the optimal many-core architecture, seven different PE configurations are simulated for processing ultrasonic images in terms of execution performance and energy consumption. Experimental results indicate that the highest energy efficiencies are achieved at PEs=1,024, 64, and 256 for ultrasonic images at $256{ imes}256$, $320{ imes}240$, and $800{ imes}480$ resolutions, respectively. In addition, the maximum area efficiencies are obtained at PEs=256 (for $256{ imes}256$ and $800{ imes}480$ image resolutions) and 64 (for $320{ imes}240$ image resolution).