| Autor: |
Chakera, T. M. H., Fleay, R. F., Henson, P. W., Cole, S. M. |
| Zdroj: |
The British Journal of Radiology; November 1982, Vol. 55 Issue: 659 p853-858, 6p |
| Abstrakt: |
Conventional single-and three-phase X-ray generators and tubes provide a continuous spectrum of photons only a fraction of which form the radiographic image. Depending upon the body thickness, low energy photons emitted from the X-ray tube may be completely attenuated, resulting in a high radiation dose with no contribution to the image. For skull and abdominal radiography, where there is an average thickness of 18 cm in the anterior/posterior projections, photons below 30 keV offer little or no contribution to the X-ray image. The purpose of this paper is to investigate metals that may be used as filters with a view to reducing radiation dose to the patient without compromising the quality of the radiographic image. The study led to the selection of erbium as the metal of choice. Erbium, with a K absorption edge of 57.5 keV and density of 91 gm cm-3and atomic weight of 68, has good physical and chemical stability under normal atmospheric conditions.Atkins et al (1975) published spectral data for singlephase X-ray generators up to 100 kVp. From this data a computer program was constructed to plot the spectral distribution and also to compute the effect of K absorption filters. Data on tissue and bone attenuation factors were also included in the program to determine transmission data necessary for correct image formation. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
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