ABSTRACT
The embryotoxic effects of neutron radiation on rodent embryos are documented, but there is disagreement about the dose-response relationship and the impact of protracting the dose. Pregnant rats were exposed to total absorbed doses of 0.15 to 1.50 Gy 14.1 MeV neutrons on day 9.5 after conception, coincident with the most sensitive stage of embryonic development for the induction of major congenital malformations. In general terms, the incidence of embryotoxic effects increased with increasing total absorbed dose. However, the dose-response relationship differed depending on the parameter of embryotoxicity chosen, namely, intrauterine death, malformations or very low body weight. In a second study, embryos were exposed to a single embryotoxic absorbed dose (0.75 Gy) administered at a range of dose rates, from 0.10 to 0.50 Gy/h. The results offer no evidence that protraction of this selected dose significantly increased or decreased the incidence or pattern of embryotoxicity of the neutron exposure used in this study. The results do not support the hypothesis of a linear dose-response relationship for the effects of prenatal neutron irradiation that contribute to embryotoxicity for total absorbed doses of 0.15 to 1.50 Gy.
Subject(s)
Embryo, Mammalian/radiation effects , Abnormalities, Radiation-Induced , Animals , Birth Weight , Dose-Response Relationship, Radiation , Female , Fetal Death , Male , Neutrons , Radiation Injuries, Experimental , Rats , Rats, WistarABSTRACT
Our aim was to compare the dose-response relationship for the embryotoxic effects of 0.43 MeV neutrons with those of 240 kVp X rays after in utero exposures during early organogenesis in the rat. At 9.5 days after conception, pregnant rats were exposed to 0.025 to 0.35 Gy 0.43 MeV neutrons at a dose rate of 0.04 to 0.07 Gy/h. Comparable biological effects were produced using 0.50 to 2.05 Gy 240 kVp X rays. Neutron irradiation produced a greater proportion of offspring with very low body weight than with malformations when compared to X rays. There were no embryotoxic effects observed at neutron exposures of 0.025, 0.049, 0.079, 0.10, 0.15 and 0.20 Gy or X-ray exposures of 0.50 and 0.96 Gy. Taken together, the results suggest that the mechanisms by which neutron irradiation affects embryonic development may, in part, be both quantitatively and qualitatively different from those by which X irradiation affects development. These results support the generalization that the embryo exhibits a nonlinear response to increasing doses of ionizing radiations during the period of early organogenesis.
Subject(s)
Embryonic and Fetal Development/radiation effects , Neutrons , Abnormalities, Radiation-Induced/etiology , Animals , Dose-Response Relationship, Radiation , Female , Male , Pregnancy , Rats , Rats, Wistar , X-RaysABSTRACT
Thyroid doses for various dermatologic radiation techniques were measured with thermoluminescent dosimeters and ionization rate meters in an Alderson-Rando anthropomorphic phantom. The effects of changes in radiation quality and of the use or nonuse of treatment cones and thyroid shields were evaluated in detail. The results indicate that the potential risk of radiogenic thyroid cancer is very small when proper radiation protection measures are used. The probability of radiogenic thyroid cancer developing and the potential mortality risk were assessed quantitatively for each measurement. The quantification of radiation risks allows comparisons with risks of other therapeutic modalities and the common hazards of daily life.
Subject(s)
Neoplasms, Radiation-Induced/etiology , Radiotherapy/adverse effects , Skin Diseases/radiotherapy , Thyroid Neoplasms/etiology , Acne Vulgaris/radiotherapy , Adult , Child , Facial Dermatoses/radiotherapy , Humans , Mortality , Neck , Neoplasms, Radiation-Induced/epidemiology , Radiation Protection , Radiotherapy Dosage , Thermoluminescent Dosimetry , Thyroid Gland , Thyroid Neoplasms/epidemiologyABSTRACT
This study was set up to provide quantitative data to evaluate unsubstantiated claims that improper dermatologic radiation techniques may cause breast cancer. A thin mylar window ionization rate meter placed at the location of the right breast of an Alderson-RANDO anthropomorphic phantom was used to measure direct and scatter radiation reaching the female breast during radiotherapy of the facial region (as given for acne). The results indicate that scatter doses are very small; they are influenced by radiation quality and the use or nonuse of a treatment cone. Quantitative risk estimates show that the very small risk of breast cancer induction can be reduced even further by the use of proper radiation protection measures.
Subject(s)
Acne Vulgaris/radiotherapy , Breast Neoplasms/etiology , Radiotherapy/adverse effects , Breast/radiation effects , Female , Humans , Radiation Protection , Radiotherapy DosageABSTRACT
Patients undergoing full-spine radiographic examinations receive x-ray doses of 115 mrad (1,150 microGy) to 85% of the body's total active bone marrow, 235 to 465 mrad (2,350 to 4,650 microGy) to the breasts, 165 mrad (1,650 microGy) to the embryo and ovaries, and 700 mrad (7,000 microGy) to the thyroid. These doses can be doubled for patients exposed to the x rays before and after treatment.