Your physician uses an endoscope (a long, flexible tube) with a small ultrasound transducer on the tip to obtain images of the lymph nodes deep in the chest. This instrument is passed into your esophagus. The transducer sends high-frequency sound waves to the organs to create detailed images of them. You should avoid food and drink for at least 6 hours before the procedure, and you will be sedated, so you should not drive or return to work for 24 hours.