Already in January the Washington University in St. Louis released a nice collection of numerical breast phantoms in 3D, for use in various optical and acoustic imaging simulation studies in MATLAB formats.
Generously, the material was released under very permissive conditions: the database is released under Open Database License. The content itself is under Database Contents License, meaning it can be used for any purpose.
The OA-Breast Database webpage is here: OA-Breast Database