My doctor scheduled me for a mammogram at 18. what are some possible reasons?

History?: J: do you have a very strong family history of breast cancer (mother, sister)? A mammogram is usually not needed until age 40. In someone as young as you, if you are having a problem we would start with a sonogram. There is no radiation with a sonogram and often a mammogram at that young age would not be helpful. See if you can clarify the reasons for the mammogram before you get it.

Not sure: Usually ultrasound is the imaging modality of choice to evaluate the breasts in young women.