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Query: UMLS:C0917816 (mental retardation)
 15,867 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The present paper describes the radiobiological effects induced by an exposure to ionizing radiation and their pathogenesis. The different skin reactions are described in detail because of their importance and frequency. Thus the acute skin lesions after high doses and the late effects resulting, either from high doses, or from accumulation of chronic irradiation, are studied. The main early syndromes are then characterized: neurological, gastro-intestinal, bone-marrow and prodromic. As far as the complex problem of radiocarcinogenesis is concerned, the main results derived from studies by international organizations such as the ICRP and the UNSCEAR are reported: risk coefficient of 5% per gray, for lethal radioinduced cancer, after total body irradiation, at low dose of low-LET radiation. The effects of irradiation in utero are then considered: risk of malformation after irradiation during the two first months of pregnancy and risk of mental retardation after irradiation during the third and the fourth months. Finally, the genetic risk is presented as being equal to one fourth of the risk of carcinogenesis at low doses. The effects of irradiation on the gonads are also described.
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PMID:[Exposure to ionizing radiation: radiobiological and pathogenic effects (2)]. 868 52

The present paper describes the radiobiological effects induced by an exposure to ionizing radiation and their pathogenesis. The different skin reactions are described in detail because of their importance and frequency. Thus the acute skin lesions after high doses and the late effects resulting, either from high doses, or from accumulation of chronic irradiation, are studied. The main early syndromes are then characterized: neurological, gastro-intestinal, bone-marrow and prodromic. As far as the complex problem of radiocarcinogenesis is concerned, the main results derived from studies by international organizations such as the ICRP and the UNSCEAR are reported: risk coefficient of 5% per gray, for lethal radio-induced cancer, after total body irradiation, at low dose of low-LET radiation. The effects of irradiation in utero are then considered: risk of malformation after irradiation during the two first months of pregnancy and risk of mental retardation after irradiation during the third and the fourth months. Finally, the genetic risk is presented as being equal to one fourth of the risk of carcinogenesis at low-doses. The effects of irradiation on the gonads are also described.
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PMID:[Exposure to ionizing radiation: radiobiological effects and pathogenesis. 1]. 872 Sep 71

The biological effects of radiation result primarily from damage to DNA. There are three effects of concern to the radiologist that determine the need for radiation protection and the dose principle of ALARA (As Low As Reasonably Achievable). (1) Heritable effects. These were thought to be most important in the 1950s, but concern has declined in recent years. The current ICRP risk estimate is very small at 0.2%/Sv. (2) Effects on the developing embryo and fetus include weight retardation, congenital anomalies, microcephaly and mental retardation. During the sensitive period of 8 to 15 weeks of gestation, the risk estimate for mental retardation is very high at 40%/Sv, but because it is a deterministic effect, there is likely to be a threshold of about 200 mSv. (3) Carcinogenesis is considered to be the most important consequence of low doses of radiation, with a risk of fatal cancer of about 5%/Sv, and is therefore of most concern in radiology. Our knowledge of radiation carcinogenesis comes principally from the 60-year study of the A-bomb survivors. The use of radiation for diagnostic purposes has increased dramatically in recent years. The annual collective population dose has increased by 750% since 1980 to 930,000 person Sv. One of the principal reasons is the burgeoning use of CT scans. In 2006, more than 60 million CT scans were performed in the U.S., with about 6 million of them in children. As a rule of thumb, an abdominal CT scan in a 1-year-old child results in a life-time mortality risk of about one in a thousand. While the risk to the individual is small and acceptable when the scan is clinically justified, even a small risk when multiplied by an increasingly large number is likely to produce a significant public health concern. It is for this reason that every effort should be made to reduce the doses associated with procedures such as CT scans, particularly in children, in the spirit of ALARA.
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PMID:Radiation biology for pediatric radiologists. 1908 23