Direct injection
Contrast media (CM) is injected directly into the site of interest, rather than letting the CM reach the site in a diluted state, along with the blood. This can be done in virtually all of the body's cavities that are filled, not with blood, but with some other fluid. Such fluids dilute the CM far less, and much more slowly, than blood, because they are not flowing but are contained within the cavity. Examples of such cavities are joints, especially the knee; the spinal canal, the tear ducts, the uterus and Fallopian tubes, and the large bowel.
GE Healthcare Glossary