Classification of emphysema in candidates for lung volume reduction surgery: a new objective and surgically oriented model for describing CT severity and heterogeneity.

OBJECTIVE

To elaborate a surgically oriented and objective model for classification of emphysema heterogeneity.

PATIENTS AND INTERVENTIONS

CT examinations of 66 candidates for lung volume reduction surgery.

DESIGN

Emphysema severity was calculated by computer as the emphysema index (EI), a commonly used computer-based quantification that accurately assesses the extent of emphysema of a CT image. The distribution of the EI in different parts of each lung was illustrated in a diagram with the position in the lung (from cranial to caudal) on the x-axis and the EI on the y-axis. The slope of the fitted line was calculated. As a measure of the variation of the EI within each lung, the EI difference was calculated.

RESULTS

A diagram was constructed with the absolute value of slope, k, on the x-axis and EI difference on the y-axis. This resulted in a diagram differentiating markedly heterogeneous, intermediately heterogeneous, and homogeneous emphysema. Nineteen patients fulfilled the criteria of bilateral markedly heterogeneous emphysema, 3 patients filled the criteria of bilateral intermediately heterogeneous emphysema, and 18 patients filled the criteria of bilateral homogeneous emphysema. Twenty-six patients had different types of emphysema in the right and left lung.

CONCLUSION

We present a method for classification of emphysema heterogeneity that is (1) objective, (2) surgically oriented, and (3) classifies both lungs separately.