{"id":25409,"date":"2019-10-29T13:42:15","date_gmt":"2019-10-29T13:42:15","guid":{"rendered":"http:\/\/sitepourvtc.com\/?page_id=25409"},"modified":"2023-06-15T06:10:15","modified_gmt":"2023-06-15T06:10:15","slug":"sievert-unit-of-equivalent-dose","status":"publish","type":"page","link":"https:\/\/sitepourvtc.com\/nuclear-engineering\/radiation-protection\/equivalent-dose\/sievert-unit-of-equivalent-dose\/","title":{"rendered":"Sievert – Unit of Equivalent Dose"},"content":{"rendered":"
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\"sievert<\/a>In radiation protection, a sievert<\/strong> is a derived unit of equivalent dose<\/strong> and effective dose. <\/strong>The sievert represents the equivalent biological effect of depositing a joule of gamma rays energy in a kilogram of human tissue. Unit of sievert is important in radiation protection and was named after the Swedish scientist Rolf Sievert, who did a lot of the early work on dosimetry in radiation therapy.<\/p>\n

As was written, the sievert is used for radiation quantities such as equivalent and effective doses. Equivalent dose<\/strong> (symbol H<\/strong>T<\/sub><\/strong>)<\/strong> is a dose quantity calculated for individual organs (index T \u2013 tissue). The equivalent\u00a0dose<\/strong> is based on the absorbed dose to an organ, adjusted to account for the effectiveness of the type of radiation<\/strong>. An equivalent dose is given the symbol HT<\/sub>. The SI unit of H<\/strong>T<\/sub><\/strong> is the sievert<\/strong> (Sv) or but rem (roentgen equivalent man) is still commonly used (1 Sv = 100 rem<\/strong>).<\/p>\n

Sievert and Gray<\/h2>\n

For radiation protection<\/a> purposes, the absorbed dose is averaged over an organ or tissue, T. This absorbed dose average is weighted for the radiation quality in terms of the radiation weighting factor<\/strong><\/a>, wR<\/sub>, for the type and energy of radiation incident on the body. The radiation weighting factor<\/strong> is a dimensionless factor used to determine the equivalent dose from the absorbed dose averaged over a tissue or organ. It is based on the type of radiation absorbed. The resulting weighted dose was designated as the organ- or tissue equivalent dose:<\/p>\n

\"equivalent<\/a><\/p>\n

\"Radiation<\/a>
Table of radiation weighting factors. Source: ICRP Publ. 103: The 2007 Recommendations of the International Commission on Radiological Protection<\/figcaption><\/figure>\n

An equivalent dose of one Sievert<\/strong> represents that quantity of radiation dose that is equivalent to specified biological damage<\/strong>\u00a0to one gray<\/strong><\/a> of X-rays<\/a> or gamma rays<\/a>. A dose of one Sv<\/strong> caused by gamma radiation is equivalent to an energy deposition of one joule in a kilogram of tissue. That means one sievert is equivalent to one gray of gamma rays deposited in certain tissue. On the other hand, similar biological damage (one sievert) can be caused only by 1\/20 gray of alpha radiation (due to high wR<\/sub> of alpha radiation). Therefore, the sievert is not a physical dose unit<\/strong>. For example, an absorbed dose of 1 Gy by alpha particles will lead to an equivalent dose of 20 Sv. This may seem to be a paradox. It implies that the energy of the incident radiation field in joules has increased by a factor of 20, thereby violating the laws of Conservation of energy<\/a>. However, this is not the case. Sievert is derived from the physical quantity absorbed dose but also considers the biological effectiveness<\/strong> of the radiation, which is dependent on the radiation type and energy. The radiation weighting factor <\/strong>causes the sievert cannot be a physical unit.<\/p>\n

One sievert<\/strong> is a large amount of equivalent dose. A person who has absorbed a whole-body dose of 1 Sv has absorbed one joule of energy in each kg of body tissue (in case of gamma rays).<\/p>\n

Equivalent doses<\/strong>\u00a0measured in industry and medicine often have usually lower doses than one sievert, and the following multiples are often used:<\/p>\n

1 mSv (millisievert) = 1E-3 Sv<\/strong><\/p>\n

1 \u00b5Sv (microsievert) = 1E-6 Sv<\/strong><\/p>\n

Conversions from the SI units to other units are as follows:<\/p>\n