What is the Difference Between Absorbed Dose and Equivalent Dose?

🆚 Go to Comparative Table 🆚

The difference between absorbed dose and equivalent dose lies in the way they measure and assess the impact of radiation exposure on biological tissues:

  • Absorbed Dose: This is a measurable, physical quantity that represents the energy deposited in a small volume of tissue. It is used to assess the potential for biochemical changes in specific tissues.
  • Equivalent Dose: This is an amount that takes into account the damaging properties of different types of radiation. Equivalent dose is calculated by multiplying the absorbed dose by the appropriate radiation weighting factor, which represents the relative biological effectiveness of the radiation. Equivalent dose is used to assess how much biological damage is expected from the absorbed dose.

In diagnostic medicine, the absorbed dose and equivalent dose are numerically the same because all radiation used has the same low-harm potential. However, the units are different. For diagnostic radiation, the equivalent dose in milliSievert (mSv) equals the absorbed dose in milliGray (mGy).

Comparative Table: Absorbed Dose vs Equivalent Dose

The main difference between absorbed dose and equivalent dose lies in what they represent and how they are used. Here is a table summarizing the differences:

Absorbed Dose Equivalent Dose
Measures the energy deposited by radiation in a mass (e.g., water, rocks, air, people) Represents the dose calculated for individual organs, taking into account the biological impact of the radiation
SI unit is Gray (Gy), with another unit being Rad Uses the mean absorbed dose in body tissue or organ T, multiplied by the radiation weighting factor WR, which is dependent on the type and energy of the radiation
Used to compare the effect of radiation on inanimate matter and for calculating radiation doses absorbed by living tissue Considered for radiological protection purposes, specifically for calculating the risk associated with radiation exposure

In summary, while absorbed dose measures the energy deposited in tissue, equivalent dose considers the biological impact of that energy.