Which pattern on a chest x-ray is described as 'butterfly' and indicates pulmonary edema?

The 'butterfly' pattern on a chest x-ray is characterized by bilateral perihilar opacities that resemble the shape of a butterfly or wings, which is indicative of pulmonary edema. This pattern is typically observed in cases of congestive heart failure or other conditions that lead to fluid accumulation in the lungs. The bilateral distribution and the specific location near the hilum contribute to the butterfly appearance, where the central part of the lung appears less affected while both sides exhibit this distinct pattern of increased density due to fluid.

Scattered densities, while they may appear in various pulmonary conditions, do not specifically denote the hallmark 'butterfly' pattern associated with pulmonary edema. Similarly, linear striations and ground glass appearance describe different radiographic findings that are not specific to the butterfly pattern. Opacities may refer to any area of increased density but lack the distinctive bilateral symmetry and shape associated with pulmonary edema indicated by the butterfly appearance. Thus, the correct choice effectively captures the visual characteristic relevant to pulmonary edema on a chest x-ray.