[Complex evaluation of film mammographic imaging systems. 2. Comparison of 18 systems using a signal-noise matrix]

The concept of the signal-noise matrix with physiological optical noise measurements for defining visibility thresholds provides a quantitative means for comparing film mammographic systems (9). Eighteen such systems were compared. A graded list can be produced relating the integrated signal-noise ratio to area and detail contrast (image quality) and to the required radiation dose (dose efficiency). For this, maximal dose (industrial film) and minimal image quality can be taken into consideration. In this list, in agreement with other publications (12) high resolution film-screen combinations, using industrial film (eg. Cronex 70/screen) come top. In combination with a grid technique, this system achieves a greatly superior image quality. Amongst commercial film-screen systems, only the Trimax mammography system with high resolution screens is comparable. All other commercial systems (single or double coated films) are unsatisfactory with respect to their dose efficiency and image quality. Some industrial films without screens (Mamoray M4) are intermediate between high definition and other commercial systems. Ninety-second, screenless films offered for mammography appear unsuitable for this purpose, both in view of their dose efficiency and image quality.