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 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
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
- 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 ...