Detection accuracy in chest radiography.

The detection accuracy of the diagnostic radiologist is important in everyday medical decision making. However, little work has been done relating the detection accuracy of the radiologist to the quality of the image. This study, using a thorax and lung phantom, simulated tissue-equivalent 6.4 mm lesions, and a 183 cm source-to-image distance, shows that the detection accuracy is not dependent on the focal spot size (over a range of 0.3-2.0 mm). However, the false positive rate increases when using small focal spots. In addition, the detection accuracy decreases with increasing root-mean-square (RMS) noise (a measure of the amount of quantum mottle in the image), while the false positive rate and intraobserver disagreement increase with increasing RMS noise. It is also shown that the nonradiologist responds to changes in noise in exactly the same way as the radiologist.