[A comparison of various methods of x-ray sensitometry]

Three methods of roentgen sensimetry have been compared: the wedge method based on using the stepped wedge, the Moscow Radiation and Roentgenology Research Institute method consisting in the time-modulation of the exposure by means of a lead diaphragm and revolving cassette with screens and film, and the method, according to which the dose is modulated by changing the distance from the source of irradiation to the cassette. The exposure conditions have been selected in order to achieve the best coordination of the results obtained by all the three methods. The minimal sensitivity of the combination of the medium amplification screens of ZY-B2A type with film PM-1 is about 1000P-1. For a more complete characteristic of the important properties of the roentgenographic films it is necessary in addition to determining the sensitivity, gamma and medium gradient to measure the parameters determining the graininess of the film and the transmission of the screen light by its emulsion layer.