How much radiation-exposure occurs in the administration of therapeutic injections for pain management?

Updated: Jun 19, 2018
  • Author: Anthony H Wheeler, MD; Chief Editor: Meda Raghavendra (Raghu), MD  more...
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X-rays are a form of electromagnetic energy. When transferred through matter, x-rays ionize human tissue and produce electrically charged ions that can induce molecular changes, potentially leading to somatic and genetic damage. Radiologic nomenclature describes radiation quantities using terminology such as the absorbed dose, effective dose, equivalent dose, and Dose-area-product. A roentgen (R) measures exposure to ionizing radiation equivalent to the electrical charge per unit mass of air (1R=2.58x10-4 coulombs/kg of air). The concentration of energy that is deposited locally into a tissue is called the absorbed dose. This is measured in units of gray (Gy) or milligray (mGy). One gray of absorbed dose is equivalent to the energy deposition of 1 joule in 1 kg of tissue mass. Doses lower than 1 Gy generally do not cause notable acute effects other than slight cellular changes.

The absorbed dose rate describes the rate of dose accumulation in mGy/min. A typical skin entrance dose rate from fluoroscopy is about 30 mGyt/min. Effective dose is the quantity of radiation exposure affecting people who are not in a stationary or typically uniform space. It is the hypothetical dose received by the entire unprotected human body and poses the same health risk as the nonuniform dose received by an individual not wearing a protective apron. For the purposes of radiation protection, regulatory limits of whole-body exposures to personnel are given in terms of effective dose. This information is extracted from the data generated by film badges or other types of personal radiation monitors.

Therefore, the radiation-absorbed dose is the amount of energy deposited into human tissue from ionizing radiation sources and is measured in Gy. Biologic effects of radiation are caused by the ionization of water molecules within the cells, producing light highly reactive free radicals that damage macromolecules of DNA. The acute effects occur at relatively high-dose levels, such as those given during radiotherapy treatments or from accidents. Chronic effects are more often the result of long-term low-dose exposure. The most common radiation-induced injuries affect the skin. Unlike a thermal burn, x-ray injuries develop slowly and may not become apparent until days or weeks later. Potential effects vary in severity from erythema to dermal necrosis and skin cancer. Additionally, the probability of induced cancer or leukemia is increased in the exposed individual. The latent period between radiation overexposure and cancer may be as short as 2 years.

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