Endobronchial ultrasound using a new convex probe: a preliminary study on surgically resected specimens

The radial endobronchial ultrasound (EBUS) probe is conventionally inserted through the working channel of the flexible bronchoscope and limits interventional diagnostics and therapeutics under direct ultrasound control. The aim of this study was to assess the new convex probe EBUS (CP-EBUS) in the visualization of the hilar lymph nodes in surgically resected specimens and explore its feasibility to perform transbronchial needle aspiration (TBNA) under direct EBUS guidance prior to its clinical use. Fourteen surgically resected specimens from lung cancer (n=12) and metastatic lung cancer (n=2) patients were included in the study. The resected specimens included eight right upper lobes, one right middle lobe, and five left lower lobes. The EBUS examination was performed with a flexible bronchoscope equipped with a 7.5 MHz convex probe (CP) that scans parallel to the insertion direction of the bronchoscope. The appearance of the hilar lymph nodes using this CP-EBUS was noted. The size of hilar lymph nodes was measured at CP-EBUS and compared with the actual size of the lymph nodes, which was measured with a Vernier's caliper. Hilar lymph nodes could be clearly visualized with CP-EBUS. There was a good correlation between the actual size of the lymph node and that measured using CP-EBUS (R(2)=0.950). A dedicated transbronchial aspiration needle could be inserted into the hilar lymph node under direct ultrasonic control. There is a possibility in the underestimation of the size of large lymph nodes due to the scanning nature of the convex probe. The CP-EBUS was successfully used to visualize the hilar lymph node and perform TBNA in surgical resected lung specimens. This technique has an excellent potential to perform direct ultrasound guided TBNA of mediastinal and hilar lymph nodes.