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Figure 9b. Spiral CT angiography (2-mm collimation, pitch of 2, 24% iodinated contrast agent) performed in a 72-year-old patient. (a) Spiral CT scan obtained at the level of the right and left main pulmonary arteries shows bilateral endoluminal hypoattenuated areas (). Note the additional presence of a partial filling defect at the level of a subsegmental branch of the superior segmental artery (arrow) of the left lower lobe. (b) Spiral CT scan obtained at the same level as in a, 2 minutes after contrast material administration, shows heterogeneous enhancement of the right and left vascular regions () due to the presence of multicentric malignant histiocytofibroma (surgically confirmed).