Image enhancement of the mandibular condyle through digital subtraction

The use of conventional radiography to visualize the mandibular condylar articulating surface is limited by the superimposition of surrounding bony elements, which can be termed structured noise. This study investigated the application of digital subtraction to reduce such noise. Two conventional radiographs were made of a temporomandibular joint: first a reference radiograph with the condyle seated in the glenoid fossa (simulating a patient with mouth closed), then a radiograph from the identical orientation but with the condyle translated slightly downward and forward (simulating mouth partially opened). The radiographs were digitized and, on a pixel-by-pixel basis, the intensity value of the second image was subtracted from the reference image to produce a third, subtracted image. The subtracted image provided a significantly improved visualization of the condyle's superior surface.