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.
