Optimising beam quality selection in mammographic acquisition using the standard attenuation rate
Tromans CE., Diffey J., Cocker M., Brady M.
A common metric used to optimise digital mammography image acquisition is contrast-to-noise ratio. Using the standard attenuation rate (SAR), a quantitative normalised representation of breast tissue for image analysis applications, we demonstrate that the image contrast may be completely separated from the acquisition parameters, in particular the beam quality, used for acquisition. Optimising the contrast-to-noise ratio at acquisition is therefore suboptimal, since the contrast may be manipulated by post processing. A tissue equivalent phantom is used to investigate the variation in both signal-to-noise ratio, and image sharpness within the SAR images. The results show that the primary effect of varying the acquisition parameters through the various automated optimisation of parameter modes, and hence the mean glandular dose, is to vary the global contrast of the acquired image, an effect successfully mapped to a common normalised basis using the SAR. The signal-to-noise ratio and image sharpness are second order effects, and are therefore dominated by the global image contrast when image acquisition is optimised using the contrast-to-noise ratio. © 2010 Springer-Verlag.