TY - JOUR
AU - Miller, Earl R.
AB - Significance of Speed and Resolution Characteristics of Certain Cassette-Screen-Film Combinations 1 Earl R. Miller , M.D. Department of Radiology, University of California Medical Center, San Francisco 22, Calif. Excerpt Replacing worn-out cassettes and intensifying screens in a radiology department using a large stock of cassettes entails a considerable expenditure, and the choices have a significant effect on the radiation exposure of patients. This problem was faced in the Department of Radiology at the University of California Medical School in San Francisco. It was desirable to obtain the fastest, most durable cassette-screen-film combination affording adequate resolution. The determination of the adequacy of the resolution became the most interesting part of the study. 1. Cassette Studies Radiation absorbed in the cassette front contributes to patient-exposure but does not add information to the radiograph. The radiopacity of ten cassette fronts of different manufacture was determined. The cassette front to be studied, without intensifying screen, was placed 6 feet from an x-ray tube. A Victoreen rate-meter probe was placed in the beam on the tube side of the cassette to act as a monitor. A similar probe was placed on the far side of the cassette front for use as a transmission-measuring device. Transmission readings were corrected with the monitor reading. One series of studies was performed at machine settings of 70, 90, and 110 kv with 3 mm. Al total filtration. Another series was made at 90 kv and 3 mm. Al plus 1.04 mm. Cu total filter. Table I, in which the results are given, shows that there is considerable absorption by various cassette fronts when the filtration is low (equivalent to no “patient” in the beam). There is also a great difference between cassettes under these conditions. When, however, the 1.04 mm. Cu filter is placed in the beam, as a substitute for a patient, the absorption of the radiation by the cassette is much less. Thus, for example, in radiography of a “thick” part, such as the lateral lumbar spine, various cassette fronts may absorb between 5 and 15 per cent of the incident radiation, whereas in radiography of “thin” parts, such as a wrist, the absorption by the cassette fronts may vary from about 11 to 34 per cent. The amount of radiation absorbed in cassette fronts is not negligible and should be taken into consideration. Manufacturers should be encouraged to provide data on this point. Cassettes that have a low absorption should be chosen. 2. Intensifying Screen Speeds The speed of intensifying screens is of importance in determining the amount of patient-exposure required for an examination. To test the speed of medium- and high-speed screens, the following procedures were carried out. Medium-speed screens (Du Pont-Patterson Par-Speed and Radelin T) were mounted in two Halsey wafer cassettes. High-speed screens (Du Pont Patterson Hi-Speed and Radelin TF) were mounted in two other Halsey wafer cassettes. These four cassettes were used in all of the following studies unless otherwise specified. A test exposure of a wire grid was made on each cassette to determine screen contact.
TI - Significance of Speed and Resolution Characteristics of Certain Cassette-Screen-Film Combinations
JF - Radiology
DO - 10.1148/80.1.103
DA - 1963-01-01
UR - https://www.deepdyve.com/lp/radiological-society-of-north-america-inc/significance-of-speed-and-resolution-characteristics-of-certain-zV5QLKY4th
SP - 103
VL - 80
IS - 1
DP - DeepDyve
ER -