Until the end of the last century doctors had no means of seeing beneath the surface of their patients’ bodies, other than by opening them up in an exploratory surgical operation. Diagnosis of internal disorders proceeded by inference from the patient’s history and the doctor’s method of external examination. A medical revolution began on 11 November 1895 when the German physicist W.C. Roentgen (1845-1923) discovered a hitherto unknown phenomenon. Experimenting with electricity, using an evacuated discharge tube, he detected the production of invisible rays that blackened photographic plates, caused chemically-treated screens to fluoresce, and had the power to pass through some solid objects. He named them X-rays. Within a short time their potential for creating images of parts of the human body ordinarily invisible to the eye had been recognized, and the era of’diagnostic imaging’ had begun. At the beginning of the present century, the chemist and physicist Madame Curie (1867-1934) discovered that natural radioactivity from radium could also be used to take X-ray photographs, and she used the method, as a preliminary to surgery, to locate bullets and shrapnel in soldiers wounded in World War I.