Ultrasounds are frequently used to complement other screening tests. 

They are most often used if an abnormality is seen on a mammogram. In cases such as this, an ultrasound can help to provide further information about the nature of a lump or an area of concern. 

Ultrasounds are also more frequently used on younger women who have denser breast tissue.  Ultrasounds can be more sensitive in picking up abnormalities in dense tissue than a mammogram can.

An ultrasound works by sending high frequency sound waves through your body.  These sound waves are then converted into images on a viewing screen.  The technician simply runs a sound-emitting probe over your breast.  There is no radiation involved and the procedure should not be painful.