The purpose of this study is to examine the diagnostic accuracy in the detection of jaw lesions with computed panoramic radiography and to find optimal parameters for every diagnostic purpose. A phantom of an artificial mandibular bone was devised, and radiolucent and radiopaque jaw lesions were simulated by a wedge-shaped cavity.
Panoramic radiographies were taken by varying the position of the phantom and the parameters of computed radiography (CR) .
The results were as follows:
1. Detectability decreased more abruptly with CR than with conventional radiography with the increase of the distance from the focal trough.
2. The optimal relative gamma value (GA) of CR for the radiolucent lesions (air) was ; 1.2 for gradationally enhanced (L) images and 1.0 for frequency enhanced (R) images. The detectavility was not influenced with the changes in the spatial frequency areas (RE) .
3. The optimal parameters for the radiolucent lesions (water) were ; GA= 1.2, RE=0.2 -0.5, frequency enhancement ranks (RN) =1 for the L images, and GA =1.0-1.2, RN = 3-5 for the R images.
4. The optimal parameters for the radiopaque lesions (50% CaCl2 solution) were ; GA= 1.2 -1.6 for the L images and GA= 1.6, RE = 5.0, for the R images.
5. The clinical images with these optimal parameters were generally recognized as better than those with non-optimum parameters.