Endoscopic Ultrasound (EUS) Guided Opacification Of Mediastinal Lymph Nodes

Background: EUS has become the preferred modality for local staging of esophageal cancer and gaining popularity for lung cancer staging as well. Reliable and long-lasting non-invasive opacification of malignant lymph nodes may help to determine the treatment field to guide radiation and surgical therapy. Tantalum, a physiologically inert metal, has been used as radio-opaque material in various areas of medicine. AIM: To assess the feasibility of EUS-guided opacification of the mediastinal lymph nodes in a porcine model. Methods: The study was approved by the Animal Institutional Review Board. All procedures were performed on 50-kg pigs under general anesthesia. A linear EUS (Olympus® GF-UCT140) was introduced into the esophagus. Mediastinal lymph nodes were identified and injections with 1ml of a tantalum suspension (5 gm of tantalum powder with 10 cc of normal saline) were attempted via 19 and 23 gauge fine needle aspiration (FNA) needles (Wilson-Cook®) under the fluoroscopic observation. The EUS and fluoroscopy were repeated 1 week later followed by euthanasia and necropsy. Results: The injection through the 23-gauge FNA needle was impossible due to a rapid precipitation of tantalum leading to complete occlusion of the needle. EUS-guided intranodal injection was performed through the 19-guage FNA needle resulting in a good fluoroscopic opacification of the mediastinal lymph node. Repeated fluoroscopy 1 week later demonstrated stable deposition of the tantalum in the place of injection. There were no complications during the procedure and in the post-procedure period. Conclusions: EUS-guided marking of mediastinal lymph nodes is technically simple and safe and can facilitate radiation therapy and surgical resection.