Mammograms, 2D and 3D both, are considered low dose radiation. This imaging delivers an average of 0.4 millisieverts (mSv) to each breast with 2 images per breast, slightly higher in 3D imaging. To put this in perspective, in the United States, we are exposed to an average of 3-4 mSv of radiation per year. This is what is called background radiation, and is increased if you are a frequent flyer, or if you live near a coal mine or nuclear plant. A chest x-ray gives 0.2mSv, and a CT scan gives an average of 10mSv radiation dose. For a screening mammogram, the dose of radiation is equivalent to the background radiation you would get from your natural surroundings in about 7 weeks.