The unit of radiation and the effective radiation dose of radiation are divided into two categories: radioactive activity unit and radiation dose unit, all of which are announced by the International Radiation Unit and the Measure Committee (ICRU), and are called international units (SI units). The following briefly describes several important radiation units:
Activity
The number of times that a radionuclide produces spontaneous decay in a unit of time, that is, the rate of decay, which is called radioactivity. The unit of activity is "Beck", abbreviated as Bq, which is defined as 1 Bq = 1 Decay/sec but is used to indicate the intensity (decay rate) of a radiation source (such as cobalt 60).
Another common old unit is "Curi":
1 Curie = 3.7 x 10 Beq (Bq) 10
Absorbed dose, D
The mass of material (kg) absorbs radiant energy (joules), called absorbed dose. The unit of absorbed dose is "Grey", abbreviated as Gy, which is defined as 1 Gy = 1 Joule/kilogram The average absorbed dose per hour is called absorbed dose rate, in Gy/h (Gy/h ), there are also milligray/hour (mGy/h), microgray/hour (μGy/h).
Equivalent dose (doseequivalent), HT
Different kinds of radiation (α, β, γ, neutrons) illuminate the human body, although the human body has the same absorbed dose, but it will cause different damage. For this purpose, radiation weight factors (Q) are defined for different kinds of radiation, which represent different levels of biological damage caused by different radiation on human tissues. Their values ​​are listed in the following table:
The equivalent dose is the product of the body's absorbed dose and the radiation weight factor, and it already contains the meaning of radiation on the human body. Its unit is "Sivot", abbreviated as "hi", abbreviated as Sv, defined as:
H (Sywood) = D (Gray) × QT
There are also milliswater (mSv), micro-Sivot (μSv). We took a chest X-ray and the chest tissue received approximately 0.1 millisieverts.
From the radiation weight factor Q, we can see that although the alpha particles have very weak penetration, they have great health hazards. For example, uranium 235 and other isotopes emitting alpha particles will cause greater harm to the body tissues.
Effective dose, E
Due to the different sensitivity of radiation to various tissues and organs of the human body, although the same equivalent dose is accepted, the risk (probability) of health loss (cancer or poor inheritance) is different, that is, different tissues and organs are irradiated. The same radiation causes different damage. Therefore, the "organizational weight factor" (WT) was also set to represent the probability of radiation loss to health on behalf of each organ organ.
If the sum of the equivalent dose (HT) of each tissue organ and its weight factor is added up, it becomes an effective dose (E). E represents the total body radiation dose used to assess the risk of radiation that may cause our health effects. The unit is also Sv.
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