Is there reliable experimental evidence for different dicentric yields in human lymphocytes produced by mammography X-rays free-in-air and within a phantom?
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 alpha of (5.88+/-0.66) x 10(-2) Gy(-1) of the linear quadratic dose-response relationship was determined. This value does not differ significantly from the coefficient alpha of (6.55+/-0.97) x 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 alpha(E) to the measured alpha coefficients as a function of the energy E of monochromatic X-rays was used to calculate weighted mean values 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) x 10(-2) Gy(-1) and (4.5+/-1.0) x 10(-2) Gy(-1) were obtained, respectively. Although the measured alpha coefficients for mammography X-rays appear to be systematically higher than those calculated as weighted mean values 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.
Büermann
L
L
Department 6.6, Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany. Ludwig.Bueermann@ptb.de
Krumrey
M
M
Haney
M
M
Schmid
E
E
D000388:Air; D002478:Cells, Cultured; D002869:Chromosome Aberrations; D002877:Chromosomes, Human / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D018499:Linear Energy Transfer; D008214:Lymphocytes / Q000528:radiation effects* / Q000648:ultrastructure; D008297:Male; D008327:Mammography / Q000009:adverse effects; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D014965:X-Rays