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Dose Estimation by Chromosome Analysis
https://repo.qst.go.jp/records/59630
https://repo.qst.go.jp/records/59630cc0c10ec-5b5b-4572-b96b-9a45d91848d7
| Item type | 会議発表用資料 / Presentation(1) | |||||
|---|---|---|---|---|---|---|
| 公開日 | 2003-04-18 | |||||
| タイトル | ||||||
| タイトル | Dose Estimation by Chromosome Analysis | |||||
| 言語 | ||||||
| 言語 | eng | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_c94f | |||||
| 資源タイプ | conference object | |||||
| アクセス権 | ||||||
| アクセス権 | metadata only access | |||||
| アクセス権URI | http://purl.org/coar/access_right/c_14cb | |||||
| 著者 |
Hayata, Isamu
× Hayata, Isamu× 早田 勇 |
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| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | Chromosomal aberrations in the peripheral lymphocytes are the most reliable biological indicator for estimating the dose in radiation exposures. Peripheral lymphocytes are in the G0 phase in cell division cycle. If cells in this phase are irradiated, chromosomal aberrations are of the chromosome type, i.e., they involve both chromatids of a chromosome as shown in Fig. Among them a fragment (Fr), a dicentric (Dic), a centric ring (Rc), and translocation (Tr) are generally used as indicators in radiation dosimetry. Chromosomes with 3 or more (n) centromeres are also induced by radiation. They are treated as multidicentrics for convenience sake, and are counted as 2 or more (n-1) dicentrics. Tr is a stable aberrations to be inherited by daughter cells while Dic, Rc, and Fr are unstable, to be lost during cell division. Theoretically, Tr and Dic accompanied by Fr are induced by radiation in the equal ratio. The background frequency of Dic and Rc is very low, about one Dic plus Rc in 1000 cells. A fragment caused by deletion is called as an excess fragment (exFr). The background frequency of Tr and exFr is much higher than Dic and Rc. In general, Dic and Rc accompanied by a fragment are specific markers of radiation exposures, while Tr and exFr are of all kinds of chromosomal mutagens. The yield (Y) of chromosome aberrations (exFr, Dic, Rc and Tr) is related to dose (D) by the equation as follows: Y=A+ alfaD + betaD2 where A is background yield, alfaD is aberrations induced by a single track of radiation, and betaD2 is aberrations produced by two or more tracks of radiation. Coefficients alfa, and beta can be obtained by an experimental study analyzing chromosome aberrations in the irraditated blood. This equation can be applied up to the doses about 6 Gy in low LET radiation where the yield of Dic saturates because of the limitation of chromosome number (46) of a man as well as cell death. In the low linear energy transfer (LET) radiation such as X-rays or gamma rays, the dose response relationship of Dic becomes linear at low doses and quadratic at high doses. In high LET radiation such as neutrons (n in Fig. 2), protons, and gamma-rays, the dose response relationship of Dic becomes rather linear. When the dose is the same , the higher the LET, the more the yield of Dic. The yield of Dic increases with the decrease of energy if the sort of radiation is the same (for example, uppermost 3 lines in Fig 3). In case of Low LET radiations, the yield of Dic decrease when the dose rate becomes lower (lowermost 2 lines in Fig. 2). On the other hand, the effect of the dose rate is not significant in the case of high LET radiation. Analyzing the yield of chromosome aberration also makes it possible to estimate the size of the exposed portion in the body and the exposed dose in the past. The increase of the yield of Dic was detected at the dose of 2 cSv in acute exposures in vitro and at the dose rate of about 1 cSv per year in chronic exposures in vivo. Typical cases of dose estimations performed by chromosome analysis will be presented. |
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| 会議概要（会議名, 開催地, 会期, 主催者等） | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | International Symposium on Innovative Technology for Radiation Risk Study 2003 | |||||
| 発表年月日 | ||||||
| 日付 | 2003-03-14 | |||||
| 日付タイプ | Issued | |||||
