Medical knowledge improved considerably during the 20th century. One of the earliest developments was the discovery of the X-ray by Wilhelm Röntgen in 1895. He was experimenting with cathode rays and realised that they could pass through flesh, but not through bone.
Within six months hospitals were installing X-ray machines and they had a major impact on medicine. Doctors could see inside the human body for the first time without having to operate. The early X-ray machines produced high doses of radiation, leading to side effects.
During World War One, X-rays saved thousands of lives as surgeons were able to operate more accurately. Since then X-rays have been used routinely in hospitals to investigate problems with bones.
This uses high frequency sound to see inside the body, and so avoids the need to use radiation as in X-rays. It produces 3D images of internal organs like the heart and kidneys, as well as muscles and since the 1970s has also been used to check the progress of babies in the womb.
Magnetic resonance imaging uses radio waves to build up a detailed picture of organs and tissues and is used to detect any areas of disease.
Positron emission tomography uses a special dye that has radioactive tracers. These tracers are injected into a vein. As the organs and tissues absorb the tracer, they are highlighted under a PET scanner, which allows doctors to investigate diseases like cancer and heart disease. CT scans (computed tomography) are X-ray procedures that combine many X-ray images with the aid of a computer to generate cross-sectional images of the internal organs and structures of the body.
All these scanning techniques have revolutionised medical knowledge, particularly over the last 30 years. They are non-invasive, but enable doctors to identify diseases earlier and so improve chances of survival.