Which of the following is the most likely explanation for a linear density paralleling the superior margin of the clavicle on PA chest radiographic examination?

Question

Quizplus · Accepted Answer

The companion shadow is a normal radiographic finding that represents the superior margin of the clavicle on a PA (posteroanterior) chest radiograph. It is caused by the projection of the soft tissues and the clavicle itself, creating a linear density that parallels the superior margin of the clavicle. This is a common and normal finding, not indicative of any pathology, unlike the other options which represent pathological conditions.

Which of the Following Is the Most Likely Explanation for a Linear