Investigation of coded excitation in advanced synthetic aperture technique for ultrasound imaging

Encoding techniques can be used to improve image quality in ultrasound imaging modality. Binary orthogonal codes, such as Hadamard codes, have been used for its relative ease of implementation in ultrasound systems. However, it requires symmetrically inverted pulse and the traditional pulse (i.e., -1 and 1) to be transmitted alongside each other. S-sequence, a variant of Hadamard code, has been used to overcome this limitation as it is made up of 0 's and 1 's making its implementation more practical. However, S-sequence has been previously applied only to synthetic transmit aperture (STA) imaging, which has limitations in frame rate and image quality at depth. Here, we explore diverging waves with virtual source encoding using S-sequence and observe improved axial and lateral resolution even at higher frame rates.