A molecular breast imaging (“MBI”} configured for combined MBI and ultrasound imaging or MBI-guided biopsy is provided. In one configuration, the MBI portion of the system includes two opposed gamma ray detectors, while in another configuration only one gamma ray detector is provided. In two detector configurations, a compression plate is provided to make contact with and apply light compression to the subject under examination. One of the gamma ray detectors is configured to be moveable with respect to the other detector such that the gamma ray detector can be moved away from the examination region, thereby allowing access to the breast for an ultrasound imaging system or a breast biopsy device.