P2I-3 A Comparison of Acoustic Beam Properties of a High-Frequency Annular and Linear Array

This paper compares the acoustic-beam properties of high-frequency linear and annular arrays operating at 40 MHz. The annular array was modeled with a spatial-impulse response method and the linear array was simulated with Field II. The parameters of the linear array were 64-mum pitch, 14-mum kerf, 3-mm elevation aperture, 12-mm elevation focus and up to 64 elements. The parameters of our 40-MHz annular array were 5 elements, 12-mm geometric focus, and 6-mm total aperture. Simulations were performed for the cases of fixed, synthetic- transmit/receive, and dynamic-receive focusing. After synthetic- focusing, the -6-dB axial depth of field (DOF) for the annular array was ap 5 mm, while the DOF of the linear array was 4 mm. Over the extended DOF of 9 to 15 mm, the azimuthal beamwidths of the annular array ranged from 65 to 89 mum, while the beamwidths of the linear array ranged from 110 to 180 mum. The practical implication of the above analysis is that an annular array will lead to better overall image quality than current state-of-the-art in HFU linear-array technology. In vivo mouse embryo data were acquired with the 40-MHz annular array and beamformed in order to demonstrate the improved image quality obtained with synthetic focusing versus fixed and dynamic-receive focusing.