Exploratory surgery is surgery whose purpose is to look inside the body to help diagnose an ailment. Because surgery is an invasive and often risky intervention, it is typically only used when other methods such as external observation and testing body fluids have failed. Modern imaging techniques, starting with the invention of CT scans in 1972, have made it possible to look inside the body without surgery; these less-invasive techniques have significantly replaced exploratory surgery in humans. Exploratory surgery is still used for non-human animals, where tools for imaging are more expensive than exploratory surgery and often less available.