Gastric emptying study is a test that evaluates the process of emptying food from the stomach. For a gastric emptying study, a patient eats a meal in which the food or beverage is mixed with a small amount of radioactive material. A “Gamma Camera” is placed over the stomach to monitor the amount of radioactivity in the stomach for several hours after the test meal. In patients with abnormal emptying of the stomach, the food and radioactive material stay in the stomach longer than normal (usually for hours) before emptying into the small intestine.

source: MedTerms.com