Objective: To find out the correlation between endobronchial ultrasonography (EBUS) images and histologic findings in normal bronchial wall via quantitative analysis of the airway wall thickness and the layer thickness.
Methods: From July 1st to December 31th in 2010, patients underwent lobectomy performed endobronchial ultrasonography (EBUS) before surgery and frost pathological examination after surgery. The layer thickness of EBUS and pathological images were measured. Bland-Altman plots were used to analyze the agreement between EBUS measurements and pathological measurements.
Results: Twenty-one patients were enrolled in the study. Five layers of the wall were distinguished at the ultrasonogram. Starting on the luminal side, the first, third and fifth layer (L1, L3, L5) were hyperechoic while the second, fourth layer (L2, L4) were hypoechoic. The wall thickness with good agreement was almost equal between the 2 kinds of images (1.877:1.745). L1 thickness was lager than the mucosa thickness (0.275:0.164). L2 thickness was smaller than the submucosa thickness (0.100:0.202). L1 + L2 thickness was almost equal to the thickness of mucosa and submucosa layer (0.375:0.366). The Bland-Altman plots showed poor agreement between the L1, L2 thickness and the mucosa thickness, the submucosa thickness while good agreement between the L1 + L2 thickness and the thickness of mucosa and submucosa layer. L3 thickness was lager than the inner perichondrium thickness (0.241:0.075), and L4 thickness was smaller than the cartilage layer thickness (0.655:0.811). L3 + L4 thickness was almost equal to thickness of the inner perichondrium and the cartilage layer (0.895:0.887). L5 thickness was almost equal to thickness of the outer perichondrium and the connective tissue outside the cartilage layer (0.533:0.491). The Bland-Altman plots showed poor agreement between the L3, L4 thickness and the inner perichondrium thickness, cartilage layer thickness, while good agreement between L5, L3 + L4, L3 + L4 + L5 thickness and the corresponding indexes.
Conclusions: There is a five-layer structure on the bronchial EBUS image including the first layer at the luminal side corresponding to the mucosa and inner part of the submucosa; the second layer corresponding to the outer part of submucosal tissue; the third layer corresponding to the inner perichondrium and the inner part of the cartilage; the fourth layer corresponding to the outer part of cartilage; the fifth layer corresponding to the outer perichondrium and the connective tissue outside the cartilage layer.