The scan involves injecting a radioactive tracer into a person’s vein. The tracer travels through the bloodstream into the body parts listed above. A special camera takes pictures to track the tracer’s movement and transmit images onto a computer screen for observation and diagnosis. This article discusses HIDA scanning and outlines what a person can expect before, during, and They are done to get images of the liver, gallbladder, bile ducts and small intestine. To prepare for a HIDA scan, a person may need to fast for 4 to 12 hours before the scan. Women who are pregnant or breast-feeding should tell their doctor.