Two mammograms - normal on left and one showing cancer on right - Courtesty NIH via Wikipedia
A mammogram is a specialized type of X-ray equipment designed to take X-rays of the female breasts in order to diagnose breast cancer. It consists of two horizontal plates, adjustable for height, one of which emits X-rays and the other which contains the X-ray film.
Traditional X-ray equipment is designed to project the rays through the entire width of the body. This requires a higher dose of radiation than a mammogram, which only needs enough X-rays to penetrate the breast instead of the thorax.
However, a mammogram is much more uncomfortable for the patient. A traditional X-ray merely requires that the patient lay down on the table. In a mammogram, the breasts literally have to be squeezed between the two plates, requiring a fair amount of pressure to hold them in place during the exposure.
In Airborne, the patient was given a mammogram to attempt to confirm breast cancer as the diagnosis.