Investigation of basic imaging properties in digital radiography. 10. Structure mottle of II–TV digital imaging systems

Single‐frame images obtained with image intensifier (II)–TV digital systems contain a large amount of structure mottle. In the present study, we examined several II–TV digital systems by use of Wiener spectral analysis and noted considerable variation of the structure mottle over the wide spatial frequency range. We found that the structure mottle in these systems may originate in the input phosphor, the output phosphor, and/or the electronic components, and that the Wiener spectra of structure mottle seem to depend on the specific combination of these components. The results of observer performance studies indicated that structure mottle can significantly decrease the detection of low‐contrast objects in a single‐frame image when the exposure incident on the II is greater than approximately 0.1 mR. In addition, we showed that the structure mottle can be removed by subtraction of a uniformly exposed mask. This simple procedure will improve the quality of radiologic images obtained with II–TV digital systems. Note, however, that the structure mottle is largely eliminated by subtraction in digital subtraction angiography(DSA)images.