Is there reliable experimental evidence for different dicentric yields in human lymphocytes produced by mammography X-rays free-in-air and within a phantom?
Tóm tắt
We examined the production of dicentrics in human lymphocytes irradiated with 29 kV X-rays to a depth of 13.5 mm in a PMMA phantom. For these irradiation conditions, which are appropriate for the diagnostic application of mammography X-rays, a coefficient α of (5.88±0.66)×10−2 Gy−1 of the linear quadratic dose–response relationship was determined. This value does not differ significantly from the coefficient α of (6.55±0.97)×10−2 Gy−1 obtained earlier for a free-in-air set-up using blood of the same donor. The results are interpreted in terms of both the energy distributions of the photon fluence of mammography X-rays free-in-air and those in the PMMA phantom. Based on earlier results of experiments with monochromatic X-rays in the energy range 1.83–40 keV (completed here by an additional measurement at 25 keV), a fit function α(E) to the measured α coefficients as a function of the energy E of monochromatic X-rays was used to calculate weighted mean values
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$$\bar \alpha$$
for both the mammography X-ray spectra free-in-air and in the phantom. As a result, weighted mean values of (4.9±1.0)×10−2 Gy−1 and (4.5±1.0)×10−2 Gy−1 were obtained, respectively. Although the measured α coefficients for mammography X-rays appear to be systematically higher than those calculated as weighted mean values
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$$\bar \alpha$$
, it can be concluded that the modification of the mammography X-ray spectrum to a depth of 13.5 mm in a PMMA phantom compared with the free-in-air spectrum has no significant influence on the dicentric yields in human lymphocytes.
Tài liệu tham khảo
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