[CT pulmonary functional imaging in emphysema: a correlative study of CT technique and pulmonary function test]

To compare the effectiveness of high resolution CT, CT pulmonary functional imaging, and pulmonary function test (PFT) in the quantitative evaluation of emphysema and obstructive pulmonary disease.

The study included 37 patients with obstructive ventilatory defect and 20 normal controls. CT and pulmonary function test were performed in all subjects in one week. Correlation between and differences among HRCT visual scoring, parameters of CT pulmonary functional imaging and the result of pulmonary function test were compared.

(1) Emphysema was detected by CT in 23 of the 37 patients with obstructive ventilatory defect. (2) HRCT visual scoring was correlated only with D(L)CO% (r = -0.731, P < 0.001) among other pulmonary function parameters. (3) HRCT visual scoring in patients with enrphysema was correlated with pixel indices (PI) at full inspiration and expiration. Visual scoring showed the best correlation with PI(-910in) (r = 0.506, P < 0.001) and PI(-910ex) (r = 0.610, P < 0.001). (4) The grading of pulmonary function based on PI(-910in) and PI(-910ex) showed no difference from the grading by pulmonary function tests (chi(2) = 0.527, P = 0.913; chi(2) = 3.645, P = 0.302). The grading of emphysema based on PI(-910in) accorded with the grading by pulmonary function tests (chi(2) = 2.59, P = 0.459).

HRCT is more sensitive than conventional CT in diagnosing emphysema. However, in terms of slice thickness and radiation dose, it cannot be used in the evaluation of both lungs. CT functional imaging is easily performed, and the results are objective and correlated with the result of HRCT visual scoring and PFTs. It may be, therefore, more useful in diagnosing early emphysema and evaluating lung function.