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Figure 2. Spiral CT scan (2-mm collimation, pitch of 2, 24% iodinated contrast agent) obtained at the level of the lower lobes in a 70-year-old patient with a previous history of severe chronic obstructive pulmonary disease and acute dyspnea at the time of diagnosis. There is a partial filling defect (arrow) at the level of a subsegmental branch of the anterior segmental artery of the right lower lobe.