Committee on Medical Internal Radiation Dose (MIRD)
Radiation dosimetry provides the fundamental quantities used for radiation protection, risk assessment, and treatment planning. The MIRD Committee develops standard methods, models, assumptions, and mathematical schema for assessing internal radiation doses from administered radiopharmaceuticals. The MIRD approach simplifies the problem of assessing dose for many different radionuclides—each with its unique radiological characteristics and chemical properties as labeled compounds—in the highly diverse biological environment represented by the human body, internal organs, tissues, fluid compartments, and cells. The virtue of the MIRD approach is that it systematically reduces complex dosimetric analyses to methods that are relatively simple to use, including software tools for experimental and clinical use.
Absorbed dose is a measure of the amount of energy deposited in a material by ionizing radiation. It is calculated by dividing the energy deposited by the mass of the material.
Manual calculation of organ dose allows for a more accurate estimation of the radiation dose received by specific organs or tissues, as it takes into account factors such as the type of radiation, the energy of the radiation, and the specific location of the organ in the body.
The steps involved in manually calculating organ dose include determining the type and energy of the radiation, determining the mass of the organ, and using mathematical equations to calculate the absorbed dose.
Absorbed dose is a measure of the amount of energy deposited in a material, while effective dose takes into account the type of radiation and the sensitivity of different organs and tissues to that radiation. Effective dose is a more comprehensive measure of the potential harm caused by radiation exposure.
The units of absorbed dose are gray (Gy) and rad. They are expressed as the amount of energy (in joules or ergs) deposited per unit mass (in kilograms or grams) of the material.