Dosimetry

Whilst Dosimetry in its original sense is the measurement of the absorbed dose delivered by ionizing radiation, the term is better known as a scientific sub-specialty in the fields of health physics and medical physics, where it is the calculation and assessment of the radiation dose received by the human body.

Internal dosimetry due to the ingestion or inhalation of radioactive materials relies on a variety of physiological or imaging techniques. External dosimetry, due to irradiation from an external source is based on measurements with a dosimeter, or inferred from other radiological protection instruments.

Dosimetry is used extensively for radiation protection and is routinely applied to occupational radiation workers, where irradiation is expected, but regulatory levels must not be exceeded. It is also used where radiation is unexpected, such as in the aftermath of the Three Mile Island, Chernobyl or Fukushima radiological release incidents, where the public irradiation is measured and calculated from a variety of indicators such as ambient measurements of radiation and radioactive contamination.

Other significant areas are medical dosimetry, where the required treatment absorbed dose and any collateral absorbed dose is monitored, and in environmental dosimetry, such as radon monitoring in buildings.

There are several ways of measuring absorbed doses from ionizing radiation. People in occupational contact with radioactive substances or who may be exposed to radiation routinely carry personal dosimeters. These are specifically designed to record and indicate the absorbed dose (or derived dosimetric index) received. Traditionally these were badges containing photographic film (film badge dosimeter), which would be chemically developed, following exposure to indicate the total absorbed dose received. Film badges have now been largely replaced with other devices such as the TLD badge which uses Thermoluminescent dosimetry or optically stimulated luminescence (OSL) badges.

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