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Biologic Effects of Radiation

Radiation Exposure Phases and Syndromes

The biological effects of radiation are dependent upon the type of exposure a person actually has. Duration of the exposure as well as the intensity of the material play a role. Factors of personal protection such as time, distance, and shielding need to be included.

Biologic effects can be categorized generically as acute or chronic. Acute exposure may be for a very short period of time to a higher level radiation source while chronic exposure can either be in extended exposure to low-level source or repetitive exposures to a variety of sources of radiation.

 Individual biological differences must be considered. Each person is different and will respond differently to radiation exposure.  Extremely high-level radiation exposure is an exception.

In general, radiation causes three major problems in our bodies.
  • Radiation can damage DNA and other cellular structures
  • Radiation exposure results in cell death immediately or shortly after exposure
  • Radiation exposure results in incorrect cellular repair and mutations that can cause cancer and other disease
The effects of radiation on each person differs in their biologic response to any given dose of radiation. The factors that influence radiological impact on the body include:
  • age- Younger patients and those with a higher metabolism and cell turnover rate are more susceptible.
  • sex
  • diet
  • body temperature and overall health
Acute radiation sickness can occur when an individual is exposed to a large amount of radiation in a short period of time (acute exposure). This level of exposure may be defined that radiation doses greater than 100 REM which is equivalent to 100 RAD for gamma ray exposure. The signs and symptoms of acute radiation sickness vary by the dose received and by the unique biologic factors of each individual. Symptoms can be as subtle as “flu-like” symptoms or as dramatic as rapid changes in blood cells. In general acute radiation sickness generates the following:
  • nonspecific (flu-like symptoms)
  • hair loss
  • fever
  • skin irritation
  • vascular changes
  • blood cell changes
While the initial symptoms may seem minor such as with G.I. upset, the sooner a person vomits or loses consciousness after cute exposure indicates severe exposure. Severity and course of treatment depend on how much total doses been received as well as how much of the body has been exposed taking into account individual susceptibility as a variable. Acute radiation sickness is not an all-or-nothing situation. The symptoms may appear shortly after exposure only to disappear after a few days. Symptoms may also reappear in a much more severe illness later on.

Acute radiation sickness has four phases and may manifest with four separate syndromes.
The four phases of acute radiation sickness are:
  • prodromal phase
  • latent phase
  • manifest phase (sometimes called the period of illness)
  • and recovery or death
The four syndromes of acute radiation sickness  are:
  • Hematopoietic Syndrome
  • gastrointestinal syndrome
  • cardiovascular syndrome
  • and central nervous system syndrome

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