Double-contrast knee arthrography

From octber 1989, in Radiology Department of Arcispedale Sant'anna in Ferrara, digital radiographic techniques have been applied to be double-contrast arthrography of the knee. In this preliminary work the diagnostic contribution of computed radiography to arthrographic findings by comparing image quality conventional and digital radiographs using a dedicated Philips unit has been examined. The digital unit is compatible with all the extant radiographic equipment in the department and automatically supplues two images, the first one resembling a conventional radiograph, the second one characterized by broader exposure range that allows a clear visualizzation of soft tissues. To obtain high-quality radiographs the processing curves of the system were modified, in particular by shifting the curve leftward, thus reducing its slope, and by amending the parameters related to spatial frequences. The changes in the reading curves made these images more useful: they were more homogeneous and allowed a better evaluation of fine details. Relative to the second type of images, characterized by both edge enhancement and a broader recording range, it was enough to shift the curve along the X-axis to compensate for a moderate image overexposure. Keeping in mind that the aim of this preliminary work was not compare the two techniques from a diagnostic point of view, in the authors' opinion the two yield similar information for the diagnostic evaluation of meniscal traumas. On the contrary, if the same principles are applied to the evaluation of capsulo-ligamentous components, digital arthrography appears to be more accurate than the conventional technique, the latter being deceptive especially in the evaluation of cruciate ligaments