Improving Reflection Mode Ultrasound Computed Tomography Using Diverging Waves

Synthetic aperture (SA) and plane wave (PW) are two transmission strategies that have been used to provide high-quality reflection mode imaging in ultrasound computed tomography (USCT). However, these methods cannot simultaneously balance deep penetration and a wide field-of-view (FOV), which are critical for tomographic imaging. In this work, we propose using diverging wave (DW) transmission to overcome this limitation. The performance of the proposed method in terms of resolution and contrast was demonstrated through in-silico studies. By synthesizing the diverging wavefront using multiple elements in transmission, we can achieve a more uniform lateral pressure distribution across a wide FOV range, which is beneficial for enhancing the penetration depth and consistency of the reflection images. The image quality of DW is comparable to that of SA, while DW exhibits a larger FOV than PW. This approach holds the potential to improve the quality of USCT by providing a clearer and location-invariant images across a wide FOV, making it a more suitable technique for a variety of clinical applications, particularly in the context of dense breast tissue imaging.