서강대학교

초록/요약

In 3-D ano-rectal ultrasonography, 3-D volume data is acquired by rotation of a linear array and used for diagnosis. The resolution of the transverse image is lowered when the image is obtained using fixed focusing in the elevation direction. In this paper, we propose a synthetic aperture algorithm (SA) in the elevation direction to improve the resolution and signal-to-noise ratio (SNR) of an image. In order to use the synthetic aperture technique, the elevation direction focusing point is regarded as a point source emitting a spherical wave in a limited area. High-resolution images are constructed by using low-resolution data obtained from a single emission. Simulation and phantom experiments were carried out using field II and ano-rectal probes. To demonstrate the improvement of the resolution and SNR of the proposed synthetic aperture technique, we compared it with the conventional technique. In addition, in the synthetic aperture technique, the focal point is assumed as a virtual source. Due to the nature of the ano-rectal probe, the natural focusing point is shortened because the size of the element height is limited. In the SA method, the natural focusing point is set as a virtual source because the focusing effect disappears as it goes beyond the natural focusing point. Compared with the conventional technique, the resolution showed good performance both in simulation and experiment. The SNR of the SA is confirmed to be √N times as many as the sum N of the low-resolution data used for producing a high-resolution image.