DIN Standards Committee Radiology
DIN 6867-3
Sensitometry of screen/film systems for medical radiography - Part 3: Method for determination of sensitometric curve shape, speed and average gradient for mammography
Sensitometrie an Film-Folien-Systemen für die medizinische Radiographie - Teil 3: Verfahren zur Ermittlung des Verlaufs der sensitometrischen Kurve, der Empfindlichkeit und des mittleren Gradienten für die Mammographie
Overview
The standard describes methods for determining the sensitometric curve shape, the average gradient and the speed of radiographic systems consisting of intensifying screen, film, filmholder and processing systems and that are used in mammography. The sensitometric curve, which is also needed for the determination of other properties such as, for example the modulation transfer function, is measured under low-scatter conditions via intensity scale X-ray sensitometry, preferably by using the photometric inverse square law (intensity scale sensitometry). While the average gradient is determined from the sensitometric curve shape, speed shall be measured by a separate method since the exposure conditions should simulate as closely as possible those which are used in practice. Therefore, scattered radiation is included, accompanied by a slight change of beam quality compared to the beam quality used for intensity scale sensitometry. Speed is generally dependent on X-ray energy distribution, the amount of scattered radiation from the patient to the image receiver and the exposure time. Therefore, some variation in speed values for the same system may be expected under practical conditions. As the range of tube voltages applied in screen-film mammography is small, ISO 9236-3 describes only one beam quality for speed measurement. The measurement conditions described in this standard provide values for speed and average gradient which are representative of those found under practical conditions. The standard represents a modified adoption of the International Standard ISO 9236-3:1999. This standard has been prepared by Working Committee NA 080-00-06 AA "Bildgebende Systeme" ("Image acquisition systems") of NAR in cooperation with the Entertainment Technology, Photography and Cinematography Standards Committee (NVBF).
