Pulse coding with complementary golay sequences for signal to noise ratio improvement in ultrasound mammography

Abstract

The main objective of this study is to obtain improved detection of 50 μm breast microcalcifications in ultrasound mammography. A synthetic transmit aperture imaging method combined with coded excitation and pulse compression is employed. Coded excitation by means of complementary Golay sequences and pulse compression at each transducer element improve the signal to noise ratio and enhance the visualization of the microcalcifications despite the fact that the process is computationally complex. Correlation based beamforming is also applied to the experimental data, resulting in significant improvement in image quality. In this study, pre-beamformed raw data is collected by an ultrasound research scanner, DiPhAS, where a 7.5 MHz phased array transducer with 128 element and 0.1 mm pitch was used. Benefits of coded excitation compared to tone burst excitation of equal energy are clearly observed. The ultrasound images of monofilament nylon wire targets in the phantom are presented, where the superiority of coded excitation is evident. The image reconstruction is performed by using Synthetic Transmit Aperture imaging method with single emission and 5 emissions, respectively. The experimental results show that efficient implementation of coded excitation improves signal to noise ratio, increases penetration depth and provides images with better resolution.