Commercial medical ultrasound scanners produce images of human tissue by interpreting the information carried by echoes reflected from structures contained inside it. In this paper, a new generation of toroidal ultrasound arrays is used to measure both the signals reflected and transmitted through the tissue. It is shown that transmission measurements encode complete information about the gross structure of the tissue and lead to images that are superiorto those obtained form reflection measurements alone. Experimental results are provided for a gel phantom and a human breast in vivo.