Computed tomography densitometry of the lung: a method to assess perfusiondefects in acute pulmonary embolism

Objective: To evaluate the potential of spiral computed tomography (CT) den sitometry of the lung to assess segmental perfusion defects in patients wit h acute pulmonary embolism. Materials and Methods: Ten patients with known segmental or lobar perfusion defects on ventilation/perfusion scintigraphy and with normal findings in the contralateral lung segment underwent spiral CT of the thorax before and after the administration of contrast material. Regions of interest were defined in 14 segments with normal perfusion and in 14 segments with reduced perfusion. Three consecutive densitometry measu rements were performed in each segment. Results: Those segments with reduce d perfusion showed a significantly lower mean CT value on the enhanced scan s (-813.4 +/- 57.1 Hounsfield units (HU) vs - 794.0 +/- 44.8 HU, P = 0.01) and a significantly decreased contrast enhancement (13.3 +/- 18.3 HU vs 29. 8 +/- 16.6 HU, P < 0.01) when compared to segments with normal perfusion. M easurements from the unenhanced CT scans were not statistically different b etween segments with reduced and normal perfusion. Conclusions: Spiral CT d ensitometry allows the assessment of at least segmental perfusion defects i n patients with acute pulmonary embolism. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.