Normal bronchial and pulmonary arterial diameters measured by thin section CT

We undertook this study to evaluate the normal values of the artery-bronchus ratio (ABR) and the bronchial lumen ratio (BLR) at subsegmental levels and to determine whether these values can be used as objective parameters for evaluation of various diseases involving the bronchovascular trees.

We analyzed high-resolution CT of 30 patients without cardiopulmonary diseases. The CT studies were performed with 5 mm collimation at 5 mm intervals from the carina to the level of the inferior pulmonary vein and with 1.5 mm collimation at 10 mm intervals through the remainder of the lung. Both ABR, defined as the outer diameter of the pulmonary artery were divided by the outer diameter of its accompanying bronchus, and BLR, defined as the inner diameter of the bronchus divided by its outer diameter, were measured at the subsegmental level on the display console.

The mean ABR was 0.98 +/- 0.14 (range, 0.53-1.39), and the mean BLR was 0.66 +/- 0.06 (range, 0.51-0.86). Although BLR revealed no statistical differences between segments, lobes, and lungs, there were statistically significant differences between the ABRs of segments and between those of lobes.

There was a wide range of normal values of ABR and BLR. This wide range of values would make these parameters of less value in the evaluation of bronchovascular bundles.