It is difficult to describe PET radiation risks in a way that will address all subjects' concerns. The following language is intended to present PET radiation risks in relation to risks from natural background exposure and the potential harms related to ionizing radiation. The consent discussion should of course include the increased risk associated with multiple scans.
"Everyone is exposed to natural background radiation daily from sources such as radon, food, water and the sun's rays. The average exposure of people in the U.S. each year is estimated to be 360 mrem (units for measuring radiation). As a very rough comparison, the amount of radiation you will receive in one PET scan is in the same range as what you would be exposed to in one year from natural background sources. There are no known risks associated with this level of radiation; however, radiation adds up throughout a person's lifetime. It is not possible to tell whether the small additional radiation you will be exposed to by participating in this study will increase your long-term risk for diseases such as cancer."