General Considerations

• The risks of iatrogenic injury from radiation exposure and contrast administration (in any route) should always be seriously considered prior to the request for an imaging study. Remember, primum no nocere…“first do no harm.”

• Almost every imaging investigation carries with it risks, some of which are yet unknown for newer modalities.

• Risks include radiation-induced malignancy (a cumulative risk over the lifetime of a patient), contrast reaction, contrast-induced nephropathy (CIN), and nephrogenic systemic fibrosis (NSF). These entities are considered in this chapter.

Radiation Risks

• Every human is exposed to radiation on a daily basis, in the form of solar radiation. Individuals living in areas where there is loss of the protective ozone layer have increased exposure to this ionizing radiation. Individuals also receive increased exposure to background radiation when they fly in airplanes.

• The highest single exposure to ionizing radiation on record occurred in the fallout from the atomic bombs dropped on Hiroshima and Nagasaki. This fallout totaled a radiation dose of 5–200 mSv.

• Medical radiation is the highest exposure to ionizing radiation that most individuals receive, putting them at increased risk of radiation-induced malignancy.

• The following is a rough estimate of the amount of radiation involved with most imaging exposures; these and other values are available online. The total effective radiation dose is dependent upon the equipment used and varies from center to center.