[en] Short communication

[en] New muonic x-ray data on the isotopes of ¹⁹²Os, ¹⁹⁴Pt and ¹⁹⁶Pt are reported. Barrett radii for the monopole part of the nuclear charge distribution are extracted and isotope and isotone shifts are obtained. A new model independent method of analysis is presented and used to analyze the quadrupole charge densities. The ¹⁹²Os data indicates that the quadrupole moment of the first excited ²₁⁺ state is negative in sign and is -1.0 +- .1 b

[en] Photon spectra from a dual-energy Linac were generated using a Laplace transform pair model. Narrow beam attenuation curves for distilled water were measured at nominal energies of 6 and 18 MV. Values for parameters of the attenuation curve model were determined by a nonlinear least-squares fit to the transmission data. Spectra were generated from the inverse Laplace transform of the attenuation curve model. The Laplace spectra are compared to computed Schiff spectra attenuated by appropriate beam hardening and flattening filters and Monte Carlo spectra calculated by the EGS code. In addition, percent depth dose calculated from the Laplace spectra are compared with observed depth dose

[en] A brain weight deficit of about 70 mg was induced at doses of approximately 75-mGy and a deficit of 60 mg was induced at 100 mGy. This confirms the effects projected and observed by Wanner and Edwards. Although the data do not demonstrate a clear dose-response relationship between the 75-mGy and 100-mGy groups, the data are statistically consistent with a dose-response effect because of the overlapping confidence intervals. The lack of a statistically significant observation is most likely related to the small difference in doses and the limited numbers of animals examined. There are several factors that can influence the brain weight of guinea pig pups, such as caging and housing conditions, the sex of the animal, and litter size. These should be taken into account for accurate analysis. Dam weight did not appear to have a significant effect. The confirmation of a micrencephalic effect induced x rays at doses of 75-mGy during this late embryonic stage of development is consistent with the findings of small head size induced in those exposed prior to the eight week of conception at Hiroshima. This implies a mechanism for micrencephaly different from those previously suggested and lends credence to a causal relation between radiation and small head size in humans at low doses as reported by Miller and Mulvihill. 16 refs., 13 tabs

[en] Many investigators have substantially reduced doses in pediatric radiography by employing specialized beam-modifying filters. Image quality is not affected. The results are achieved by reducing the amount of low-energy, poorly penetrating x-rays as well as cutting back on the low-contrast high-energy portion of the bremsstrahlung spectrum. The maximum dose reduction can theoretically be achieved by employing an optimal single photon energy. The authors used the theory of information content and patient exposure to determine this energy. Its dependence on patient size and other factors is demonstrated. Experimental results using this approach are presented

[en] The dependence of response of air-kerma meters on air-kerma rate and beam energy is investigated for meters used in the United States. The response of some meters is reduced considerably at the high kerma rates sometimes encountered in diagnostic examinations. The energy dependence of some meters leads to inaccurate measurements of the half-value layer in mammography. Performance characteristics of meters necessary to produce sufficiently accurate measurements are discussed

[en] The detail signal-to-noise ratio model of radiographic imaging is quantitatively anayzed in terms of its accuracy in describing observer threshold perceptibility of radiographic detail. The model is found to adequately describe the effects of magnification, scatter radiation, and system resolution on observer threshold perceptibility. However, it is shown that the model does not apply in screen/film radiography for very low contrasts and high scatter conditions due to insufficient optical density contrast. The dose-to-information conversion efficiency of a radiographic imaging system is defined and the effect of magnification, scatter, resolution, image processing, detector efficiency, grids, patient table support, field size, and geometry on the dose efficiency of the imaging system are investigated

[en] Concerns about conceptus exposure to ionizing radiation, the level of conceptus dose that is likely to result from the mother's occupation, precautions to insure low conceptus dose, and the effects of radiation on the conceptus are discussed as they relate to the woman radiologist, her career and possible pregnancy. The amounts of radiation per examination are tabulated for the various radiologic modalities, and a summary is given of exposure levels

[en] An analytical method to compute x-ray spectra from attenuation data utilizing the Laplace transformation has been extended to include characteristic radiation. It is based on an a priori technique of determining the ratio of characteristic radiation exposure to the total radiation exposure in diagnostic spectra. The technique is shown to produce characteristic intensities in good agreement with experimentally determined values

[en] The dependence of response of air kerma meters on air kerma rate and beam energy is investigated for meters used in the United States. The response of some meters is reduced considerably at the high kerma rates sometimes encountered in diagnostic examinations. The energy dependence of some meters leads to inaccurate measurements of the half-value layer in mammography. Performance characteristics of meters necessary to produce sufficiently accurate measurements are discussed. (author)