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Figure 1. Spiral CT scan (2-mm collimation, pitch of 2, 24% iodinated contrast agent) obtained at the level of the right upper lobe in a 65-year-old patient with acute onset of dyspnea. There are multiple partial filling defects at the level of the anterior (arrowhead) and posterior (arrow) segmental arteries of the right upper lobe. Note the additional presence of bilateral pleural effusion.