A study of the display pixel-based focusing method in ultrasound imaging

This paper presents a new beamforming technique, in which ultrasound waves are focused at the display pixels on the Cartesian coordinates, rather than sampling points located on the uniformly-separated scanlines on either the polar or Cartesian coordinates. Consequently,this method does not require a digital scan converter (DSC) and therefore completely eliminates the dist ortions due to the DSC. A new imaging system based on the proposed method i s also presented, which is advantageous over conventional systems in hardwa re complexity, especially when high-density imaging is required. The new me thod can also be used effectively to achieve high frame rates for real-time 3D imaging and cardiac applications. To verify the proposed method, we mod ified a commercial ultrasound scanner and performed experiments with a 3.5 MHz convex array and a 7.5 MHz linear array. The experimental results with in vivo and in vitro data show that the proposed technique provides much sm oother and finer images than the conventional dynamic focusing methods.