[Axial calcaneus roentgenograph]

Low-frequency noise caused by intestinal gas, bone, or high-contrast subjects on roentgenographs often makes them difficult to read. The plantodorsal projection of the calcaneus taken by the conventional method has low-frequency noise because of its own high contrast for the long axis. Even if a higher X-ray tube voltage is used to reduce the low-frequency noise, middle- or high-frequency signals such as those of bone trabeculae are also reduced. We investigated a new method that takes into consideration the subject contrast between the part of the posterior calcanean articulation and distal part on the calcaneus projection, the spectrum of bone trabeculae, and the scatter fraction. The technique we introduced has some merit compared with the conventional method in that it reduces image distortion, provides low contrast for the long axis, and sharpens trabeculae images and articulations.