Optimum X-ray spectra for mammography

Abstract

A number of authors have calculated x-ray energies for mammography using, as a criterion, the maximum signal-to-noise ratio (SNR) obtainable per unit dose to the breast or conversely the minimum exposure for constant SNR. The predicted optimum energy increases with increasing breast thickness. Tungsten anode x-ray spectra have been measured with and without various added filter materials to determine how close the resultant spectra can be brought to the predicted optimum energies without reducing the x-ray output to unacceptable levels. The proportion of the total number of x-rays in a measured spectrum lying within a narrow energy band centred on the predicted optimum has been used as an optimum energy index. The effect of various filter materials on the measured x-ray spectra has been investigated both experimentally and theoretically. The resulting spectra have been compared with molybdenum anode, molybdenum filtered x-ray spectra normally used for mammography. It is shown that filters with K-absorption edges close to the predicted optimum energies are the most effective at producing the desired spectral shape. The choices of filter thickness and Vp are also explored in relationship to their effect on the resultant x-ray spectral shape and intensity.

Performance tests for mammographic film-screen combinations: use of absolute techniques

“…beam quality, an optimum working voltage of 28 kVp with the Mo/Mo target-filter combination has been selected for all of the tests. This conclusion was also confirmed by other studies in the literature (17)(18)(19). The optimal combinations of 30 F-S pairs were investigated in this work by sensitometry and total performance phantom and efficiency measurements.…”

Optimisation of Image Quality and Dose

“…In mammography the possibility of adapting radiation quality to object thickness by selection of the tube voltage alone is very limited together with the conventional molybdenum anode-molybdenum filter system (Gajewski and Reiss 1974;Jennings et al 1981;Beaman et al 1982;Aichinger et al 1994;S€ abel and Aichinger 1996). The relative energy distribution of the X-ray photons (i.e.…”

Image Quality in Mammography with Special Reference to Anti-Scatter Grids and the Magnification Technique

“…Recently, it has been suggested that x-ray tubes with tungsten anodes used with palladium filters would give images comparable to molybdenum tubes (7,8,30). An example of a primary mammographic spectrum at 30 kYp with a tungsten anode is also shown in Fig.…”