第一次属于screening. It is required by federal law to cover by insura

the radiation dose level is lower for good reason (wont get into details here). If something suspeciou is found, then they will have to do a Diagnostic exam which typically involves ultrasounds, or even biopsy, or MRI. These procedures may require some co-payment, depending on insurance. 

I am not saying there is no fraud, but that was the reason for the follow up exams. 

As for ultrasound, it is NOT a good screening tool. So no good for breast cancer screening.