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  • Important concepts used to describe radiation include exposure, absorbed dose, and dose equivalent.

  • A relatable way of explaining the radiation dose from medical procedures to patients is to compare the dose to the reference dose, the yearly radiation exposure from natural sources.

  • Institutions must maintain radiation levels consistent with the As Low As Reasonably Achievable (ALARA) philosophy.

  • Deleterious effects of radiation are classified as either stochastic, where the probability of occurrence increases with dose, or deterministic, in which the severity increases with dose after a threshold is exceeded.

  • Major factors in limiting dose are time, distance, and shielding.

  • Regulatory agencies, such as the Nuclear Regulatory Commission (or state agencies in Agreement States), regulate the use of radioactive materials including transportation, handling, disposal, personnel monitoring, and medical use.

The Health Physics Society defines radiation as “energy that comes from a source and travels through space.”1 Radiation can be atomic particles such as alpha and beta emissions, as well as electromagnetic energy associated with radio, microwaves, radar, visible light, ultraviolet light, x-rays, and gamma rays. If the radiation has enough energy to remove an electron from an atom, creating an ion, it is termed ionizing radiation.2 Ionizing radiation includes x-rays, gamma rays, and alpha and beta particles and can lead to biological damage by depositing energy in living tissue, breaking molecular bonds.

This chapter will introduce units that describe radiation, sources of radiation exposure, radiation dose limits and introduce radiation biology. The chapter will further focus on radiation safety and protection regulations pertinent to the practice of nuclear cardiology. In the United States of America (USA), these regulations are governed by the Nuclear Regulatory Commission (NRC) and are found in Title 10, Parts 19, 20, and 35 of the Code of Federal Regulations (CFR). Most states in the USA are agreement states, meaning that they have an agreement with the NRC to regulate the use of radioactive materials within the state. Agreement state regulations have to be at least as strict as NRC regulations. NRC NUREG 1556 Volume 9, Revision 3 provides guidance specific to radioactive materials licensing for medical use and offers suggested policies and procedures for radiation safety compliance.3


Medical use of radioactive materials is defined in Part 35 of the CFR as “the intentional internal or external administration of byproduct material or the radiation from byproduct material to patients or human research subjects under the supervision of an authorized user.” The authorized users for nuclear cardiology are physicians who meet certain training and experience requirements and are identified on the facility’s radioactive materials license.4 Also important to the license is the Radiation Safety Officer (RSO), a person who is responsible for implementing the radiation protection program. The regulations specify that the RSO must have independent authority to stop unsafe operations and sufficient time to oversee ...

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