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The Effect of Film Quality on Reading Radiographs of Simple Pneumoconiosis in a trial of X-ray sets
  1. F. D. K. Liddell
  1. Medical Statistics Branch, National Coal Board, London

    Abstract

    Four chest radiographs (14 in. × 14 in. postero-anterior) for each of 86 coal-miners were taken (in a trial to compare ϰ-ray sets) and assessed by a number of experienced readers for both quality and pneumoconiosis. All films were developed by one technician under standard conditions so that variations in the quality of the films produced for one subject arose because of differences in the sets and in the way they were used by the radiographers taking the films. The data thus obtained allowed a study of film quality to be made (a) in relation to the subject and (b) as it affected the reading of simple pneumoconiosis.

    The subjects were selected to include a high proportion whose earlier radiographs showed pneumoconiosis; they were thus substantially older than a normal colliery population.

    The assessments of quality were found to be reasonably consistent both between observers and on different occasions for the same observer.

    A clear tendency was found for the quality of a film to depend on the subject. Men with no radiological evidence of pneumoconiosis tended to produce films which were assessed as of better quality than those of men with pneumoconiosis, however slight. Among the latter, chest thickness had an important effect on film quality; men with thicker chests produced poorer films. The subject's age did not appear to have any effect on the quality of his film.

    Film quality was found to introduce only slight biases into the reading of pneumoconiosis. Individual readers varied considerably so that, although on average the readers tended to overcorrect for technical faults, i.e. to read more abnormality in black films than in good ones, and less in grey, some readers undercorrected slightly.

    What little evidence was available did not suggest that poor quality of films introduced any excess variability into film reading.

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