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Tuesday

Biological Effects of Radiation #1

This multi-part  series of articles will focus on radiation and biological effects. We'll cover the basics of radiation as well as the phases and syndromes associated with radiation exposure. In this post we'll provide an overview of radiation sources, measurement, and an introduction to the biologic effects.

Biological Effects of Radiation Part 1 Radiation Basics

Potential Radiation Sources...the threat is not just from terrorism. The threat or potential of harmful radiation can be expected from a variety of sources. These sources include, but are not limited to:

  • Nuclear weapon
  • Nuclear power plan accidents
  • Transportation and waste storage accidents
  • Military accidents
  • Vandalism
  • Terrorism
Rules for Radiosensitivity...made easy

“The sensitivity of cells to irradiation is in direct proportion to their reproductive activity and inversely proportional to their degree of differentiation.” (Bergonie and Trubondeau)

What this means is:
  • The faster turnover rate (reproduction rate) a cell has the greater radiation exposure will effect it.
  • Unborn children and young children are affected more.
  • Effects can be terotgenic or mutagenic. 
Dose Rate Effects

Dose RATE is a significant factor for the biological response to a given dose of radiation exposure. As the dose rate is decreased and the exposure time is increased, the biological effect for a given dose is decreased.

What this means is:

At lower dose rates more subleathal damage to the cell can repair and cell populations have time to reproduce and repopulate.

Units of radioactivity measurements

In order to understand the effects of radiation on a cell, tissue or organism three units of activity must be looked at. The three units of activity that are of concern to patient care are:
  • Units of activity.
  • Units of radiation dose or deposited energy
  • Units of biological dose equivalent.
  • Units of activity
A radioactive substance can be characterized by its activity or rate of decay. The units measuring radioactive decay are:

  • The Becquerel (Bq) or disintegrations per second:
    • 1Bq = 1 disintegration per second
  • The Curie (Ci)
    • 1 Ci = 3.7 x 1010 Bq

Units of radiation dose

Units of radiation that is absorbed (the dose) of any radiation type and in any material is defined as the amount of energy deposited or received. The units of absorbed dose are:

  • The radiation absorbed dose (rad)
    • 1 rad = 0.01 Gy
    • 1 Gray (Gy) = 100 rad
Types of radiation injury
  • Whole body radiation
  • Partial body radiation
  • External contamination
  • Internal contamination
  • Combined radiation and traditional injuries
Local radiation injury
  1. Frequently involves the hands
  2. Acute Radiation Syndrome (ARS) is rare
  3. Traditional wound management is not effective
Links and References

You'll also find these links and references useful. I've used them, in part and along with references, to put this series together. Again, the complete bibliography will be posted along with the final installment of the series. 


Radiation Injury Treatment Network


Radiation Emergency Medical Treatment (from the U.S. Department of Health and Human Services)


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