Real-time 3D ultrasonic imaging with 2D array is difficult to implement because of the challenge in fabricating and interconnecting the 2D transducer array with a large number of elements. Row-column addressing provides a simple manufacturing method with 2N connections rather than N2 for an N×N array. The top and bottom electrodes of the transducer are designed to be orthogonal, resulting in essentially two orthogonal1-D arrays in a single transducer. However, this interconnection scheme degrades the image quality because of defocusing in column direction in transmit event. To solve this problem, a split row-column addressing (SRCA) scheme is proposed in this paper. Rather than connecting all the elements in the column direction together, the array is divided into several disconnected blocks. This method can access focusing beams in both row and column directions. Selecting an appropriate split scheme is the key to maintaining a reasonable trade off in image quality and the number of connections. The relation between the number of split and the corresponding main-lobe width is discussed. The simulated point spread functions of 32×32 array with and without split row-column addressing are given out. The result shows the image quality is similar to fully addressing for 32×32 array in case of five blocks with 4, 6, 12, 6, and 4 elements of each block.
During the last decade, various methods for 2D array design have been developed for real-time 3D ultrasonic imaging. Most of the methods concentrated on how to reduce the number of elements and channels to overcome the difficulties in array fabrication and mass data processing. Few works focused on the 2D array beamforming techniques to narrow the main lobe width and suppress the side and grating lobe levels, thus improve the 3D image quality. Coherence imaging (CI) has been verified to suppress the side and grating lobes of the 2D ultrasound images in an effective way. It was based on a statistical analysis of the received signal dispersion. In this paper, two kinds of CI, coherence factor (CF) and sign coherence factor (SCF) are modified for 2D arrays and combined with array designs to improve the 3D ultrasound image qualities. The simulation results of point spread functions show that the main lobe width is narrowed from 1.26mm to 1.01mm and the side lobe level is suppressed from -48.79dB to -79.31dB for dense arrays with CF. Similar simulation results can be obtained for other array designs. The combination of CI and 2D array design provides a potential approach to increase the 3D imaging resolution and contrast without increasing the system complexity.