Ultrasound tomography imaging methods for imaging a tissue medium with one or more ultrasound transducer arrays comprising a plurality of transducers, wherein said transducers comprise source transducers, receiving transducers. The methods include assigning a phase value or time delay to source transducers, exciting the transducers and calculating a search direction based on data relating to the excited transducers.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
 This invention was made with Government support under Grant No. MIPROLDATM0144 from the Breast Cancer Research Program of DoD-Congressionally Directed Medical Research Programs and Contract No. DE-AC52-06NA25396 awarded by the Department of Energy. The Government has certain rights in the invention.