Study Syllabus for Classification of Radiographs of Pneumoconioses
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Subset 4 – Small and Large Opacities
Subset 4 consists of a narrative analysis of small rounded and small irregular opacities at profusion levels of 0/1 and 1/0, illustrated by representative radiographs. In addition, the subset includes composite radiographs that illustrate examples of ax, large opacity A, and carcinoma of the lung.
The ILO 2011 System classifies the small parenchymal opacities of pneumoconiosis according to shape, size, extent, and profusion or concentration. The correct determination of profusion is important because it is the best-known indicator of the dust burden of the lung. Also, although not intended for this purpose, profusion levels have been used by various state and federal agencies as part of the medical evidence in the adjudication of compensation claims.
A variety of structures, both normal and abnormal, may produce similar patterns. For example, small blood vessels projected on end commonly appear as small rounded opacities. Usually small blood vessels are fewer in number and less uniform in size than pneumoconiotic small opacities, and they are usually associated with the characteristic branching shadows of vessels seen in profile. Also, in the normal aging process, bronchovascular structures may thicken and become irregular, making them difficult to distinguish from the small irregular opacities of pneumoconiosis. This may be more pronounced if the individual has a smoking history, has had repeated pulmonary infections, or shows early manifestations of congestive heart failure. Many other pathologic conditions not related to pneumoconiosis from mineral dust exposure may also present as small opacities in any or all lung zones. Histoplasmosis or varicella are examples.
It has been stated that when the profusion of pneumoconiotic opacities is minimal, there are few situations in diagnostic radiology in which the differentiation of the normal from the abnormal is more difficult. The availability of a 12-point scale of profusion for both small rounded and small irregular opacities may appear to indicate that profusion levels are easily distinguished and quantified. Such is not the case, however, particularly at the lower end of the scale, where profusion levels of 0/1 and 1/0 must be differentiated. As a result, inconsistencies occur, and multiple readings may be necessary to resolve differences, even among experienced readers. Several factors are responsible for the inconsistencies of interpretation at these profusion levels. Among these are poor image quality, a lack of experience with chest radiography or the ILO Classification system, and a lack of familiarity with the radiographic appearances of the pneumoconioses.
The ILO 2011 Standard Radiographs illustrate only the middle categories of profusion, 0/0, 1/1, 2/2, and 3/3. This subset is, therefore, specifically designed to familiarize the reader with the distinctions among profusion levels 0/0 (normal), 0/1 (normal), 1/0 (abnormal), and 1/1 (abnormal) as they relate to small opacities of various shapes and sizes.
Now look at radiographs #39 to #46 in turn, and compare each with the narrative description provided. In each of these radiographic series, Image A represents a normal lung with profusion 0/0, Images B, C, and D represent higher levels of profusion of small pneumoconiotic opacities.