Study Syllabus for Classification of Radiographs of Pneumoconioses
Section 2: Parenchymal Abnormalities (Continued)
2C. Large Opacities
A large opacity is one having a longest dimension greater than 10 mm. Large opacities are classified individually and collectively as follows:
A = an opacity whose greatest diameter exceeds 10 mm. but is less than 50 mm, or several opacities each of which exceeds 10 mm. in diameter but the sum of whose greatest diameters does not exceed 50 mm.; B = a large opacity whose greatest diameter exceeds 50 mm. but whose area is not greater than the area of the right upper zone, or several large opacities the sum of whose greatest diameters exceeds 50 mm., but which when summed do not exceed an area equivalent to that of the right upper zone; and C = a large opacity whose area exceeds that of the right upper zone, or several large opacities whose areas when summed exceed the area of the right upper zone. Identification of a large pneumoconiotic opacity may be facilitated by recognition of a coexistent background of small pneumoconiotic opacities.