Ultra Sound:
http://breastcancer.about.com/od/imagingandscreeningtests/f/mammo-vs-ultrasd.htm
Ultrasounds Are Diagnostic, Mammograms Are For Screening
Breast ultrasound is good at distinguishing between a fluid-filled cyst and a solid mass. Ultrasound cannot image the entire breast at once, so it's used for a diagnostic spot check of areas that a screening mammogram has already revealed.
Ultrasound can not:
image the whole breast at once
image areas deep inside the breast
make 100% accurate diagnostic images
show microcalcifications -- the most common feature of tissue around a tumor
Neither technology is perfect. And in the case of ultrasound, the skill level of the operator makes a great difference in your results. One technician may miss something, another one may find it.
