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.
The absorbed dose is the amount of energy deposited by ionizing radiation per unit mass of tissue, typically measured in grays (Gy). It is a crucial metric for assessing the potential biological effects of radiation on specific organs or tissues.
To manually calculate the absorbed dose for an organ, you need to know the energy deposited (E) in joules and the mass (m) of the organ in kilograms. The absorbed dose (D) is then calculated using the formula D = E/m. This requires detailed knowledge of the radiation energy and the organ's mass.
Several factors influence the absorbed dose to an organ, including the type and energy of the radiation, the organ's size and density, the distribution of the radiation source, and the presence of any shielding materials that might attenuate the radiation.
Calculating the absorbed dose for specific organs is important because different organs have varying sensitivities to radiation. This information helps in assessing the potential risk of radiation-induced damage, guiding medical treatments, and ensuring safety in radiation therapy and radiological protection.
Manual absorbed dose calculations can be limited by the accuracy of the input data, such as the precise energy deposition and the exact mass of the organ. Additionally, manual calculations may not account for complex geometries and heterogeneous tissue compositions, potentially leading to less accurate dose assessments compared to computational methods.