The large difference in transmission between the mediastinum and the part of the chest mainly containing lungs causes major problems in chest radiography. A system for advanced multiple beam equalization radiography has been evaluated. Evaluation of image quality has been performed both using standard phantoms and from clinical radiographs. Measurements of radiation dose burden to the patient have been made both in clinical examinations and using an anthropomorphic phantom. The image quality, in areas with low transmission, is substantially increased using the equalization system. In parts of the chest mainly containing lung tissue, conventional systems show an equal or slightly better image quality. The radiation dose burden to the patient is increased by 25 percent using the equalization system, as compared to a low-dose air-gap system. In our opinion, the slight increase in radiation dose burden is well motivated by the high overall quality of the radiographs produced.
A large-sized image intensifier-TV-fluorographic system in combination with 100 mm sheet-film camera was evaluated for use in neuroradiologic practice. The image intensifier tube had new features such as a large input screen diameter, metal input screen cover and fiber optics on the output screen. The system was evaluated both technically and clinically. With some modifications, the tested system can be recommended for use in neuroangiography provided that it is supplemented by facilities for full-size or magnification technique.
The clinical demands for accuracy of roentgen generator scales were investigated in order to define suitable levels of tolerance to be required during calibration procedures and preventive maintenance on modern equipment. Radiographs of various film densities were made of four body parts. As test observers 59 radiologists and 53 radiologic technicians were asked to judge which radiographs they considered acceptable or not acceptable. Ninety-five per cent of the radiographs were accepted with the underor overexposure of one mAs step. The spread of the estimations of suitable exposure data made by 38 radiologic technicians was also investigated. From these data the clinically acceptable tolerance of roentgen generator exposure parameters could be derived. It is suggested that the tolerance of tube voltage (kV) should be less than ±5 per cent, current-time product (mAs) -20 to +25 per cent and automatic exposure control systems (AEC) -20 to + 25 per cent.
Monitoring of film processors performance is essential since image quality, patient dose and costs are influenced by the performance. A system for sensitometric constancy control of film processors and their associated components is described. Experience with the system for 3 years is given when implemented on 17 film processors. Modern high quality film processors have a stability that makes a test frequency of once a week sufficient to maintain adequate image quality. The test system is so sensitive that corrective actions almost invariably have been taken before any technical problem degraded the image quality to a visible degree.
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