Although paragangliomas can occur in a variety of anatomic locations, the majority are seen in relatively predictable regions of the body. Extraadrenal paragangliomas have nearly identical imaging features, including a homogeneous or heterogeneous hyperenhancing soft-tissue mass at CT, multiple areas of signal void interspersed with hyperintense foci (salt-and-pepper appearance) within tumor mass at MRI, and an intense tumor blush with enlarged feeding arteries at angiography.

Although pulmonary artery aneurysms are a rare vascular anomaly, they are seen in a wide variety of conditions, such as congenital heart disease, infection, trauma, pulmonary hypertension, cystic medial necrosis and generalized vasculitis. To our knowledge, mycotic aneurysms caused by pulmonary actinomycosis have not been reported in the radiologic literature. Herein, a case of pulmonary actinomycosis complicated by mycotic aneurysm is presented. On CT scans, this case showed focal aneurysmal dilatation of a peripheral pulmonary artery within necrotizing pneumonia of the right lower lobe, which was successfully treated with transcatheter embolization using wire coils.

In daily practice, cases in which a unilateral hyperlucent hemithorax is seen at frontal chest radiography are often encountered. Because such an abnormality is related to various conditions, including radiographic artifacts, chest wall abnormalities, pulmonary vascular disorders with reduced perfusion, and lung parenchymal abnormalities with air trapping or compensatory over-expansion, a radiographic finding of increased radiolucency involving one hemithorax may give rise to difficulties in differential diagnosis. The accurate radiographic interpretation of unilateral hyperlucency therefore requires an awareness of the spectrum of these causes. The various conditions can be grouped on the basis of their underlying mechanisms and radiographic features, and according to our experience, an approach that reflects this is useful for their evaluation and differentiation. In this pictorial essay, we present the imaging spectrum of the conditions causing unilateral hyperlucent hemithorax, emphasizing the importance of a systematic approach to the radiographic interpretation of the re-615

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