What Does a Dosimetrist Do?

Dose is a polysemy and can be expressed as: 1. drug dose; 2 radiation dose.

Basic meaning

Dose

Dose means once

Basic meaning of dose

In nuclear chemistry, radiation dose refers to the quantity related to the interaction of radiation and radiation with matter in the field of ionizing radiation, such as the absorbed dose (absobed dose), exposure (exposure), specific kinetic energy, flux density, etc. ^[3] .

The amount of ionizing radiation is a problem in radiation medicine and human radiation protection. International units (SI) are also used in radiation doses. According to the recommendations of the International Radiation Unit Measurement Board (1962), Japan's metrology law has been significantly revised in 1966. If the biological effect is the target, the number and distribution of ions and excited molecules generated by the interaction between radiation and biomolecules are more important than the state of the radiation energy spectrum. Therefore, the following various units are used:

Dose- related amount

Exposure dose

The so-called irradiation amount describes the amount of X-rays and -rays ionizing ability in the air. It is defined as generating 1 electrostatic unit of electricity in 1 cubic centimeter of air (1.293 mg of air) under standard conditions. Exposure X is the quotient obtained by dividing dQ by dm, where the value of dQ is the total charge of the ions generated when all electrons (negative and positrons) released by photons are completely blocked in air with mass dm Absolute quantity, that is: X = dQ / dm. Unit: Coulomb · kg ^ -1 (C / kg);

Roentgen's definition is: under 1R X or -ray irradiation, the secondary electrons generated in the air at 0.001293g (equivalent to the mass of 1cm ^ -3 dry air at 0 ° C and 760mm Hg atmospheric pressure) in the air form The amount of charge is a positive ion or a negative ion of one electrostatic unit. The exposure is only for air, and only for X or gamma rays.

Absorbed dose

Absorbed dose refers to the average energy of ionizing radiation received per unit mass of substance ^[4] . It is defined as the quotient of d divided by dm, where d is the average energy given by ionizing radiation to a irradiated substance with mass dm. That is, the SI unit of the absorbed dose of D = d / dm is Joule · kg-1 (J · kg ^ -1), and the proper name of the SI unit is Gray [gray], symbol Gy. The name of the special unit temporarily used with SI is rad, and the symbol is rad. 1Gy = 1J · kg ^ -1 = 100rad, or 1rad = 10 ^ -2 J · kg-1 = 10 ^ -2Gy. It describes the amount of ionizing radiation energy. When ionizing radiation interacts with matter, part or all of its energy can be deposited in the illuminated medium. Its unit is rad, which is equivalent to receiving 1 × 10 ^ -5 joules of energy per gram of matter. 1Gy = 100rad. Unlike the case of exposure, the absorbed dose is the amount of radiation suitable for any type of ionizing radiation and any type of irradiated substance. It must be noted that when applying this measure, it is necessary to indicate the specific exposure substance, such as air, muscle or other specific materials.

3. Absorption rate

Absobed dose rate refers to the absorbed dose per unit time (such as rad / min);

4. Irradiance rate

Exposure ra-te refers to the exposure dose per unit time;

5. Equivalent dose

The absorbed dose multiplied by the appropriate correction factor ^[4] (absorbed dose) is called the equivalent dose and is represented by the symbol H. The equivalent dose is limited to protective applications. The equivalent dose H at a point in the tissue is the product of D, Q, and N; the equivalent dose is the amount of ionizing radiation that reflects the strength of biological effects caused by the absorption of various rays or particles. It is not only related to the absorbed dose, but also to the type and energy of the radiation. The equivalent dose is based on the absorbed dose and introduces a weight factor (wR) related to the type of radiation and energy: H (T, R) = wR? D In the formula (T, R), D (T, R) is called the organ dose, and it is the average absorbed dose of radiation R in the tissue or organ T. International units: Sv (Sievert), 1Sv = 1J? Kg ^ -1. Old dedicated unit: rem (Rem), 1Sv = 100rem;

6. Effective Equivalent

Effective dose equivalent (Effective dose equivalent) is the product of the average dose equivalent received by each organ or tissue of the human body and the corresponding machine weight factor when the whole body is subjected to non-uniform irradiation when the radiation effect occurring in human tissues or organs is a random effect. The sum.