TY - JOUR
AU - Busanovich, G. M.
AB - The Calibration of X-ray Developer 1 G. M. Busanovich Philadelphia Excerpt THE high degree of accuracy obtainable with modern x-ray apparatus and methods of exposure requires correspondingly exact work in the dark room to insure uniform results from day to day. However excellent the exposure technic, density and contrast may be impaired or detail may be obscured by fog during development. The chief concern of the processing room is to maintain the extremely fine control of the developing solution that is necessary in producing comparable films of good quality 2 (1). Development is a chemical process in which the exposed silver halide of the emulsion is reduced to black, finely divided silver by the developing solution. The chemicals are gradually exhausted by the films that are developed, and, to a less extent, by aerial oxidation. The exhaustion of the chemicals must be compensated for by lengthening the development time at definite intervals, that is, after a certain number of films have been developed. The compensation in time must be sufficient to allow for the loss in density and contrast, but must not cause too much fog; for developers, as they are being used, give less density and less contrast, and, to a slighter degree, produce more fog, which is further increased by the longer development. In the x-ray film, density, contrast, and detail are intimately related and are determined mainly by the exposure technic (voltage, current, length of exposure, size of the focal spot and its distance from the film, efficiency of intensifying screens, etc.). To a less extent they are affected by the developer. With a given exposure, a definite density and a definite degree of contrast are obtainable by development in a particular fresh solution for a definite period. Increase in the length of development of one of two otherwise identical negatives causes an increase in density, and usually in contrast. The chief requirement of the developer is that the contrast and density decided upon as satisfactory, for general purposes, shall be maintained throughout the entire life of the solution. In common practice, this depends upon accurate adjustments of the development time. For a particular purpose, more or less density and contrast may be sought by over- or under-development. In any competent work with developers, some account is taken of their effect upon density but their effect upon contrast is usually disregarded. Nevertheless this is an important consideration, because as the developer becomes exhausted there is a loss in both density and contrast, but a point is reached at which the latter falls more rapidly than the former. Consequently they should be measured separately. Fog may be produced during exposure ( e.g. , by secondary radiation) or in developing. It is axiomatic that during development light must be rigidly excluded from the dark room. Chemical fog must be kept at a minimum by scrupulous care, preventing at all times contamination of the solution by foreign material (soap, metal, dust, etc.).
TI - The Calibration of X-ray Developer
JF - Radiology
DO - 10.1148/35.4.407
DA - 1940-10-01
UR - https://www.deepdyve.com/lp/radiological-society-of-north-america-inc/the-calibration-of-x-ray-developer-a1feGjzzTB
SP - 407
VL - 35
IS - 4
DP - DeepDyve
ER -