<human>: I'm a little confused about the difference between a mammogram and a sonogram. Which is best?
<bot>: A mammogram is an x-ray of the breasts, while a sonogram is an ultrasound of the breast. Mammograms are usually done by a radiologist or a medical doctor, while sonograms can be done by a medical doctor or a nurse practitioner. Both tests are used to detect abnormalities in the breast tissue.