Orthogonal Golay Codes With Local Beam Pattern Correction in Ultrasonic Imaging

Abstract

The goal of this study is to improve the synthetic transmit aperture (STA) imaging method by employing the transducer array element beam pattern correction combined with emission of mutually orthogonal complementary Golay sequences. The transmit-receive scheme based on simultaneous emission of different Golay pairs by adjacent transmit subapertures is implemented to decrease the image reconstruction time. A brief discussion on the fundamentals of the orthogonal Golay complementary sequences is provided and their advantages for the STA imaging method are demonstrated. The performance of the developed approach was tested using FIELD II simulated synthetic aperture data from the point reflectors, which allowed to estimate both; the penetration depth and the lateral resolution. In the work the 128 element, 5 MHz, linear array transducer was used. The obtained results showed that the applying the beam pattern correction leads to the image quality improvement in the vicinity of the transducer face. Specifically, the noise level evaluated between the point reflectors at the depth of 4 mm decreased from $ - 14.1~\hbox{dB}$ for the case of omnidirectional source to $ - 38.7~\hbox{dB}$ when the element beam pattern correction was implemented. The simulation proved that the overall imaging quality was improved considerably.