Detectability of normal anatomy in digital panoramic radiographs

The aim of this study was to evaluate the image quality of digital panoramic radiographs and its correlation with the detectability of normal anatomical structures. The effects of image enhancement on the detectability were also studied. A total of 500 panoramic images (DICOM format) obtained with a storage phosphor-based digital system were evaluated. The image quality and the detectability of selected normal anatomical structures were evaluated in all images. Images with inadequate image quality were subjected to enhancement after which the detectability of the structures was re-evaluated. Only 9% of the images were classified as having adequate technical quality. The main sources of poor image quality were that the patient's tongue was not held against the palate and incorrect positioning of the patient. Not holding the tongue against the palate was found to have a negative impact on the detectability of maxillary structures. Of the images with horizontal positioning errors the patient's head was rotated to the left in 81% (70 images). The most effective form of enhancement was a combination of increased contrast and decreased brightness. Images in which the tongue was not held against the palate were partially improved, whereas images with positioning errors remained unaffected by this enhancement. In conclusion, most of the panoramic images showed some technical flaws. The marginal bone level and the maxillary area were the most difficult areas to reproduce. Retakes could be avoided in some cases by using image enhancement. However, this should not be regarded as an option to avoid poor image quality.