Study Syllabus for Classification of Radiographs of Pneumoconioses

Radiograph Classification

Subset 4 – Small and Large Opacities

Symbol ax

Symbol ax refers to an area of coalescence of small opacities. The area may be of any dimension but is not homogeneous in character because the margins of individual small opacities are still identifiable. A large opacity “A” is more homogeneous. It should be noted that coalescence may occur with small rounded as well as with small irregular opacities. Coalescent small opacities (ax) and “A” large opacities may be present in the same radiograph and should be so classified. Additional projections or chest CT would likely resolve the issue. The distinction of whether a shadow represents coalescence vs a large opacity is not trivial; some federal and state agencies consider the presence of a large opacity as evidence of disability.

Radiograph #45 – Symbol ax

Answer Key #45A pdf icon[PDF – 492 KB]
Answer Key #45B pdf icon[PDF – 493 KB]
Answer Key #45C pdf icon[PDF – 493 KB]
Answer Key #45D pdf icon[PDF – 493 KB]

Radiograph #45 illustrates 3 examples of coalescent small opacities (images B, C, and D) and contrasts them with image A, which shows superimposition of opacities without coalescence.

Radiograph #45A. This image illustrates an excellent example of r/r – 3/3. The left lung shows superimposition of many small opacities but there is no coalescence. The normal vascular pattern is totally obscured. On the right there is a category A large opacity in the right upper zone, as well as coalescence (ax) along the upper right lateral chest wall. Note also hilar adenopathy (hi).

Radiograph #45B. An area of coalescence, ax, is seen on this image lateral to the left hilum (arrow) overlying the left fourth anterior rib. Large opacities are evident along the right lateral chest wall as opaque densities adjacent to areas of coalescence in which the margins of small opacities are still discernible. These large opacities would be classified as category “B” since the sum of their diameters is greater than 50 mm.

Radiograph #45C shows widespread rounded small opacities, q/r, with a profusion of 3/2. A good     example of coalescent small opacities is seen beneath the middle left clavicular shadow (arrow), and the left base overlying the 6th anterior rib (arrow). These densities are not considered to represent a large opacity because it is not homogeneous and the margins of the coalescing small opacities remain visible. This image also illustrates superimposition of small opacities and a large relatively homogeneous opacity where the sum of the long axis diameters is greater than 50 mm, therefore category “B”. Note the large opacity on the right is in the lower zone. Symbol di is checked.

Radiograph #45D once again shows widespread small rounded opacities, r/r, and profusion of 3/+. There is an area of coalescent small opacities (ax) over the anterior left second rib in this image. Large opacities are classified as “B” when are added together and superimposition of small opacities are also present.

Page last reviewed: August 5, 2020