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Pain management specialists who perform injections with the assistance of fluoroscopy must have a basic knowledge of radiation effects and safety. Although a complete review of this topic is beyond the scope of this chapter, the following outlines some of the most important details of working in an x-ray environment. These include basic principles of radioactivity, potential adverse effects to patients and physicians, and preventive measures for maintaining effective radiation safety.


Radiation is the process by which energy in the form of waves or particles is emitted from a source. Electromagnetic radiation (EMR) has no mass and no charge. Common types of EMR include: gamma rays, x-rays, ultraviolet visible light, infrared, radar, microwaves, and radio waves. This list is in increasing order of increasing wavelength.


X-rays are one of the most common potential radiation hazards in health care. The hazard is mainly due to potential harmful biological effects resulting from x-rays passing through matter with enough energy to remove electrons (ionizing radiation) from atoms, which can result in ionized atoms and free radicals (atoms with an unpaired electron in the outer shell). This risk of biological damage from radiation exposure can exist even with low doses. Biological effects of radiation exposure depend on two major factors: dose and duration. The greater the exposure, the greater the risk.


Radiation is both naturally occurring and man-made. It occurs all around us and cannot be completely avoided (“background” radiation.) We are also exposed to radiation through medically necessary testing (e.g., dental x-rays, nuclear medicine, and radiology procedures). Typically, the average individual is exposed to roughly 3.6 mSv per year or 360 mrem per year (see terminology in following section). This dosage is both from medical and scattered background radiation.


  • Exposure (E): is the ability of energy to ionize air (source-related). The unit is the roentgen (R), which is the amount of radiation that produces ionization of one electrostatic unit (ESU) of either positive or negative charge per cc of air at 0°C and 760 mm Hg (STP). In SI units it is coulombs (C)/kg (1R = 2.58 × 10).
  • Absorbed Dose (D): is a measure of the energy absorbed in a unit mass of material from radiation. It depends on the characteristics of the absorbing medium. The unit is the radiation absorbed dose or the rad (1 rad = 100 erg/g absorber). In SI units, gray (Gy) is the unit of radiation absorbed dose and is given by 1 Gy = 100 rad = 1 J/kg absorber. D = f × E (is the f-factor or roentgen-to-rad conversion factor). At diagnostic x-ray energies, the f-factor for air and soft tissues is close to 1.
  • Dose Equivalent (DE): is a measure of the biological damage that is likely to result from the absorbed energy. The unit is roentgen equivalents man, or rem. In SI units, the Sievert (Sv) is the unit of dose ...

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