[Screening for tracheobronchial diseases with digital storage phosphor radiography]

Digital storage phosphor radiography (FCR: Fuji computed radiography) has a wide dynamic range and unique postprocessing capabilities. This study was designed to test whether chest imaging with FCR and its image processing would increase the accuracy of and confidence in the diagnosis of tracheobronchial abnormalities. In a phantom study, the performance of digital images having the appearance of a conventional chest radiograph was compared with that of a conventional system in detecting simulated tracheobronchial nodules. The digital images of lower kilovoltage (ROC area = 0.647 +/- 0.035) were equivalent to the conventional radiographs (ROC area = 0.620 +/- 0.028). On the other hand, nodule detectability was significantly improved in the digital images of higher kilovoltage (ROC area = 0.826 +/- 0.020). The author also compared the impact of five postprocessing algorithms (standard image, wide latitude image, enhanced image, reversed image, and subtraction image). ROC analysis indicated that the default standard image (ROC area = 0.826 +/- 0.020) was as good as an image with a linear rather than a sigmoid gradation curve (ROC area = 0.843 +/- 0.020), an image with strong enhancement of high frequencies (ROC area = 0.804 +/- 0.020), and an image with reversed gray scale polarity (ROC area = 0.775 +/- 0.015). Therefore these specific algorithms had no effect on the detection of tracheobronchial nodules. However, digital subtraction soft tissue images (ROC area = 0.961 +/- 0.030) were significantly better than the control images. Clinical study also indicated that subtraction images improve diagnostic accuracy in tracheobronchial diseases.