Optimal photon energies with respect to absorbed dose for visualization of soft tissue masses with adipose tissue.

The photon energies which maximize the signal to noise ratio per unit absorbed dose (optimal photon energies) have been calculated for detection of soft tissue masses within adipose tissue 3--15 cm thick. The detection task simulates mammography in women with fatty breasts. Ideal, plain film and calcium tungstate screen-film systems were considered in the analysis. Net photographic density is not incorporated into this model; therefore, the optimal photon energy with respect to the signal to noise ratio per unit absorbed dose may not be the same as the photon energy which results in maximum film density per unit absorbed dose. Therefore, the model has limited applicability to film or screen-film systems. However, it is directly applicable to digital systems where brightness and contrast can be adjusted.