What Is Dosimetry?

Dosimetry, whose full name is "radiological dosimetry", or more slightly, "ionizing radiation dosimetry", is a science that studies the deposition of ionizing radiation energy in matter.

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Dosimetry, whose full name is "radiological dosimetry", or more slightly, "ionizing radiation dosimetry", is a science that studies the deposition of ionizing radiation energy in matter.

The importance of dosimetry is closely related to the biological effects of ionizing radiation. Ionizing radiation illuminates biological tissues, where energy is deposited. The deposition of these energies is quite concentrated, can directly damage DNA, cause important biological effects, and can reach locations that are difficult to reach in other ways. These characteristics make ionizing radiation of extraordinary significance in biology, tumor treatment, radiation protection and so on. Dosimetry is an indispensable foundation for application and research in these fields.

Radiation therapy is the most important application area of dosimetry.

Chinese name

Dosimetry

Foreign name

dosimetry

Subject

physics

Ionizing radiation interacts with the irradiated substance and energy is absorbed by the substance. The amount of ionizing radiation energy absorbed by a metered substance is called the absorbed dose, which is the quotient of energy and mass.

The process of ionizing radiation interacting with the irradiated substance can be divided into two processes: energy transfer and energy deposition. First, ionizing radiation collides with matter, transferring energy to secondary electrons. If the original ionizing radiation particles are non-charged, then the energy generated by these secondary electrons transferred from the primary radiation to the secondary electrons is referred to as "K = Kerma = kinetic energy released per unit mass". In other words, the initial energy carried by the secondary electron is the specific kinetic energy K.

The International Commission on Radiation and Units ICRU defines specific kinetic energy as follows:

Specific release kinetic energy K is

Divide by d

The resulting quotient, ie

among them:

Are uncharged particles in mass d

Sum of the initial kinetic energy of all charged particles released in the material.

However, the measurement of specific kinetic energy in most materials is difficult to achieve, and the better one is air. If the material is air, the specific kinetic energy is called the specific kinetic energy of air, which is represented by Ka . The unit of specific kinetic energy (air specific kinetic energy) is J / kg, which is named Gy.

The energy transferred to the secondary electrons is attached to the secondary electrons in the form of kinetic energy, and these secondary electrons lose energy mainly in the form of ionization. Ionized energy is deposited in the material and becomes the absorbed dose. However, there are also some secondary electrons that lose energy in the form of radon radiation, etc. This part of the energy is taken off in the form of photons, without local deposition, that is, no absorbed dose is formed.

The absorbed dose is the quantity directly related to the radiation effect and is the most important quantity in dosimetry. Biological effects are the most important effects of radiation effects, and the absorbed dose of biological tissues is the basis for studying biological effects of radiation. The absorbed dose of biological tissue is difficult to measure, and the absorbed dose of water has become the most commonly used absorbed dose. It is generally not specified in the literature that the absorbed dose of a material is a water absorbed dose.

The ICRU defines the absorbed dose as follows: