Partial vs. Total-Body Exposure
Another part of figuring out whether radiation might cause harmful effects has to do with the part of the body that is being exposed. With natural background radiation, our whole body is exposed. With a heart x ray, the heart (our chest) is being exposed. Sometimes many different parts of the body might be exposed at the same time with some of the areas or organs getting a larger dose than other areas. That is the case with most nuclear medicine exams. Radioactive material is usually injected into a patient and gets passed through the body by the blood, finally stopping in specific organs. In that case, the total body receives some radiation dose while the organ or organs that collect the radioactive material receive more radiation dose.
The amount of the body (all of it or just some of it) and location within the body receiving a radiation dose are related to the potential harmful effects. We will consider three circumstances, two with partial exposure and one with total-body exposure. For this section, the term “critical organ” is being used and is defined as an organ that must continue to function for us to be able to live.