Numerical Analysis on Cross-Shaped Array with Dynamic Transmit Focusing for Enhanced Volumetric Ultrasound Imaging

Volumetric ultrasound imaging has been primarily used as a clinical tool to diagnose cardiac dysfunction. However, the modality still suffers from system complexity due to a large number of receive channels for volumetric reconstruction. The aim of the study was to numerically assess a cross-shaped sparse array with a dynamic transmit focusing method to reduce the system complexity and to compensate for the image quality of unfocused volumetric imaging. Analytical simulations with two-way point spread functions demonstrated that the cross-shaped sparse array entailed up to an 84% increase in side-lobes (up to 32 dB), thus leading to significant degradation of the point spread function in the diagonal plane. A dynamic transmit focusing method was able to vividly overcome the image degradation by transmitting more beams with tilting angles. This also yielded a comparable image sensitivity (65 dB) to that of the full array when 31 × 31 tilted waves were used. The proposed cross-shaped sparse array with the dynamic transit focusing method can be used to enhance the frame rate as well as the image quality for unfocused ultrasound imaging.