Dear sdixon: It is not uncommon after a screening mammogram to be called back for additional views. Usually, the mammogram for call back are read more immediately to ensure that the area in question is well visualized. Mammogram, Ultrasound and MRI all have different purposes and are not “alternatives” for each other. You should discuss this with your doctor to see if he can clarify why the third mammogram was ordered, what the findings are, and whether additional testing is warranted.
With dense breasts it is often difficult to get satisfactory views on a first mammogram. Callbacks are not infrequent for magnified views of specific areas. If a diagnostic mammogram would have been ordered those additional views could very likely have been done at the same time. Diagnostic mammograms are done when a Radiologist is present to read the films immediately rather than the films being read at a later time. I am suprised that your first call back wasn't a diagnostic.
Each exam (mammogram, ultrasound, MRI) has it's own purpose and each is best to see something different. You might request that your next exam be diagnostic in nature to prevent all these return trips and you might ask about anything that might be available to reduce the discomfort this causes you. Some institutions are using a numbing gel before mammograms to lessen the pain of the exam.