Significance of Endoscopic Ultrasonography Guided Transbronchial Lymph Node Biopsy (TBNA) and Ultrasound Elastography in Lymph Node

Introduction Elastography was first proposed by Ophir of Texas State University in the United States in 1991 ，which can objectively reflect the elastic information of the tissue through the deformation of the external force. Then, the elastic information is converted to RGB (red,green,blue) mode image, where hard tissue is shown in blue, medium tissue in green and soft tissue in red, overlaid on the B-mode image. Different image colors reflect the difference of tissue hardness, and then help identify the difference between benign and malignant tissue hardness. UE has become a hot spot in medical ultrasound imaging shortly after it was proposed. Now UE is widely used in the diagnosis of diseases in the breast, thyroid, prostate and other related tissues. The common clinical UE includes quasi-static elasiticity imaging, acoustic radiation force pulse (ARFI) and shear wave elastography (SWE).

Lung cancer is one of the most common malignancies with high morbidity and mortality，the 5-year survival rate being only 16%. Lymphatic metastasis, the most common mode of metastasis, is of great significance for staging of lung cancer. Therefore, the correct diagnosis of benign and malignant intrathoracic lymph nodes becomes the key to definite diagnosis and accurate treatment. EBUS-TBNA has shown its certain diagnostic value in lung cancer, lymphoma, sarcoidosis and lymph node tuberculosis. However, researches related to real-time endobronchial UE (EBUS-RTE) are scarce, EBUS-RTE combined with EBUS B-mode ultrasound and enhanced CT is even fewer.

This study aimed to evaluate the value of endobronchial UE in differentiating benign and malignant intrathoracic lymph nodes qualitatively and quantitatively, and the combined features were evaluated as well. Here we show that endobronchial UE has significant value in the differential diagnosis of benign and malignant intrathoracic lymph nodes.

Materials and Methods Patients Patients undergoing EBUS-TBNA examination in the Department of Respiratory Diseases, Nanjing Hospital Affiliated to Nanjing Medical University from June 2016 to April 2017 were recruited in this study. All patients were evaluated by chest enhanced CT and/or 18-FDG PET-CT. Those who had enlarged intrathoracic lymph nodes(≥1cm) and/or 18-FDG high uptake (SUV Max > 2.5) without bleeding tendency, abnormal coagulation function and serious cardiac dysfunction were finally selected. The study was approved by the Ethics Committee of Nanjing Hospital (YL 20160713-020) and supported by Nanjing Science and Technology Commission (201505002). All the patients gave written informed consent.

EBUS B-Mode ultrasound The patients were sedated by local anesthesia (lidocaine, China Otsuka Pharmaceutical Incorporated Company) and conscious sedation (midazolam, Jiangsu Nhwa Pharmaceutical incorporated company; fentanyl, Yichang Humanwell Pharmaceutical Incorporated Company; and propyl chloride, Xi'an Libang Pharmacertical Company) .The patients received an ultrasonic bronchoscopy (the Olympus 290 electronic bronchoscopy system of Japanese Olympus Company) from the mouth, the glottis, through the trachea. The locations of the lymph nodes were initially determined according to preoperative imaging examination. The B-mode ultrasound was started and the image focus and depth of observation was adjusted after the ultrasonic water sac was filled, so that the whole target lymph nodes and the surrounding normal tissues were clearly displayed on the screen. the investigators observed multi sections, selected the largest layer of the target lymph node, and retained pictures.The ultrasound image characteristics were independently recorded by three skilled respiratory physicians. The results were discussed and judged until consensus was reached.