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* This chapter is dedicated to the memory of our dear colleague Howard Smith who was a trusted friend, a renaissance clinician trained in multiple fields and disciplines, a scholar with boundless energy, and a compassionate professional who strived to reduce pain in all of his many endeavors.


A fundamental knowledge of radiation effects and safety is essential for any pain management specialist who performs fluoroscopically guided procedures. It is sobering to note that practitioners of fluoroscopy and radiography in the first half of the twentieth century had the highest incidence of cancer-related death among all physicians. 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 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. Greater exposure is associated with greater 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), of which 15% is due to medically necessary procedures.


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 ...

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