Quantification of thin-section CT lung attenuation in acute pulmonary embolism: Correlations with arterial blood gas levels and CT angiography

OBJECTIVE. The purposes of this study were to investigate the frequency histogram of lung attenuation on CT angiography (CTA) in patients with and without acute pulmonary embolism (PE) and to evaluate the relation of the frequency histogram of lung attenuation and hypoxenua. MATERIALS AND METHODS. Twenty-six patients with PE and 11 patients without PE who underwent CTA were evaluated with frequency histograms. We obtained quantitative parameters such as mean lung attenuation, median lung attenuation, SD, skewness, kurtosis, and the proportion of lung attenuation except for the median +/- 50 H (P +/- 50 H). Lung attenuation was also assessed visually and scored. The relationship between those histogram parameters, or visual score, and Pao(2) was evaluated. CTA scores for evaluation of the degree of pulmonary artery obstruction were obtained, and the relation with Pao(2) was assessed. RESULTS. No significant differences were found in mean lung attenuation and median lung attenuation between patients with and without PE. Meanwhile, SD, skewness, kurtosis, and P +/- 50 H were significantly different between patients with and without PE (P = 0.0003, 0.0071, 0.0047, and 0.0028, respectively) and significantly correlated with Pao(2) (r = -0.770, 0.797, 0.786, -0.871, respectively). Significant differences were found in visual scores between patients with and without PE (p < 0.0001). There were significant but relatively low correlations between CTA score and arterial blood gas levels (r = -0.442, p = 0.03). CONCLUSION. In patients with acute PE, heterogeneity in lung attenuation is more prominent than in patients without PE.