X-rays

X-rays Wilhelm Conrad Röntgen, Professor of Physics in Wurzburg, Bavaria, accidentally discovered X-rays in November 1895 while studying cathode rays in a low pressure gas discharge tube. Alone in his laboratory on a Friday evening, he placed his hand in the path of the invisible rays which he was investigating, and saw an image of the bones on the screen beyond. Later, using a photographic plate instead of a screen, he made the first X-ray photograph — of his wife's hand, her wedding ring clearly visible. This was a highly significant breakthrough in the history of medicine because it made so many other things possible. It opened a window to what goes on in our bodies and in our heads. While news flashed round the world and most read of the discovery in the newspapers, Röntgen sent copies of his scientific paper to only two people in Britain: Lord Kelvin in Glasgow, for whom he had the highest esteem, and Professor Shuster in Manchester. Kelvin passed his copy to Dr John Macintyre, ‘Medical Electrician’ at the Glasgow Royal Infirmary. Like many others — physicists, electrical engineers, and doctors — in those early hectic days, and perhaps the most energetic of all the medical pioneers, Macintyre quickly grasped the significance of this ‘new light’ as it was then known. His X-ray department was up and running by March 1896 — one of the first radiological departments in the world. He subsequently had many other ‘firsts’: an X-ray of a kidney stone, a halfpenny in the gullet of a child, and, most spectacular, a ‘cineradiogram’ showing movements of a frog's legs. He probably did not produce the first medical radiograph in Britain: this is attributed to another Scot, Campbell Swinton, electrician and photographer in London, who also gave the first public demonstration of X-rays to the Royal Photographic Society in February 1896 — just one day before an open-air demonstration by a Birmingham GP, Hall-Edwards; he was also one of the first to apply X-rays to diagnosis: in that same month he took a photograph which located a needle in a woman's hand. There followed a distinct move to treat these new rays as public entertainment, but while some treated Röntgen's discovery with a certain hilarity and scepticism, like a freak show, the medical profession quickly recognized its potential. In the months following the news, scientists and doctors on both sides of the Atlantic were among the earliest pioneers working feverishly to reproduce X-rays and radiographs (medical X-ray photographs). Among the first medical radiologists, along with John Macintyre, were Sidney Rowland, who demonstrated X-rays to the Medical Society of London, and greatly advanced the cause whilst an undergraduate scholar in 1896 at St Bartholomew's Hospital; and Francis H. Williams in Boston, MA, who published a book in 1902 on the diagnostic and therapeutic use of X-rays, and in the 1920s wrote of his reminiscences as a pioneer.-->

The X-rays were also called ‘skiagrams’ (coined by Rowland) or ‘shadows’ at that time. When Röntgen observed the ‘new light’ he called it an X-ray, because it had been unknown; the name has persisted, although the deservedly eponymous alternative, Röntgen ray, is also used.

During the first two decades, the use of X-rays spread widely, mainly to define fractures and foreign bodies such as bullets — first in the Boer War and later in World World War I. Screening, or fluoroscopy (allowing the doctor to view the patient under X-ray, without taking a ‘still’ photograph), was a frequent alternative to radiographs. At that time electricity supplies were unstable and, before examining the patient, radiologists, or their technical assistants, radiographers, would place their own hands in the X-ray beam as a test for optimum exposure. Little was appreciated of the dangers of X-rays and protection was unknown, but the hazards all too soon became apparent. Frequent exposure led to radiation burns, loss of fingers, and fatal skin cancers. A Martyr's Memorial was erected in Hamburg in 1936 by the German Röntgen Society, inscribed with the names of 169 X-ray and radium martyrs from 15 countries who by then had died; the highest tolls recorded were 14 British, 20 German, 39 American, and 40 French. Twenty-eight more British names were later added. It was not until the 1920s that any protective requirements became obligatory, although some steps had been taken earlier — notably, the London Hospital in 1908–9 was among the first to provide protection for operators.

While the specialty of radiology has undergone incredible changes and now incorporates a wide range of imaging techniques, X-rays remain the cornerstone, accounting for a least 60–80% of all diagnostic imaging examinations. In all such systems X-rays are produced in a glass vacuum tube by electrons striking a tungsten target. The resulting beam of X-rays, invisible to the eye, directed at the part being examined, passes through the patient's body. Various structures absorb the X-ray photons differentially: bones more than soft tissues; other organs and tissues such as muscle producing shadows of varying intensity. The image is recorded by a detection device, either a fluorescent screen (screening) or photographic film (radiography). However, using X-rays alone it is not possible to distinguish between soft tissues of the same density, and to do this various liquid or gaseous contrast media are used. The American physiologist Walter Cannon (1871–1945) was a pioneer in this field who devised this way, now in routine diagnostic use, of examining the internal workings of the body without recourse to surgical interference. He utilized the newly discovered X-rays to examine the passage of food which had been mixed with a radio-opaque substance through the gut of humans and experimental animals. He was initially interested in the mechanisms of swallowing, but subsequently, using a range of foods, he analysed the mechanical properties of every region of the gut. Pictures of the ‘J’ shape of the stomach and pylorus during gastric emptying were originally traced onto lavatory paper held over the Röntgen screen: they are still the classic illustrations used in many textbooks.

Barium is used by mouth to outline the stomach (barium meal), or per rectum to outline the large bowel (barium enema). Water-soluble contrast media can be injected into blood vessels or the chambers of the heart to produce an angiogram, or to be excreted by the kidneys, giving an image of the urinary tract: an intravenous urogram. With such techniques it is possible to investigate virtually any part of the body by X-ray, to give information not only about structure but also about function. These contrast studies, along with X-rays of bones and of the chest, form a very large component of the practice of radiology.

X-ray tomography is a further technique used to define deep internal structures more clearly. In ‘linear tomography’ the X-ray tube, emitting a beam of X-rays, moves in a straight line while the X-ray film moves in the opposite direction. In this way most structures are blurred by the movement but the image is focussed at a particular plane, so giving greatly improved definition. More complicated variations include circular and multidirectional tomography, producing even sharper images. This type of tomography was widely used in the past to define bones, kidneys, or the inner ear, but has now largely been supplanted by computed tomography (see imaging techniques).

With so many patients having X-ray examinations, protection from the dangers of radiation has become of paramount importance. X-ray tubes are encased in lead shields and fully protected and equipment is regularly calibrated. Staff are required to wear lead aprons and to remain behind protective screens during exposures, and their radiation dose is monitored by a device contained in a ‘badge’ which they wear all the time. Likewise patients must be properly supervised and protected. Gonad protection is essential especially in women of child-bearing age. There must be ‘a clear-cut clinical indication’ before any X-ray is requested so that unnecessary tests are avoided. All X-ray examinations must be directed by a properly trained physician, almost always a radiologist. If recognized practice is followed, the dangers from diagnostic X-rays are negligible.

The damaging properties of X-rays have been put to positive use in radiotherapy; already in the early 1900s this was established for the treatment of skin diseases and cancers. Despite the advent of radioisotopes in radiotherapy, X-rays continue to be used for this purpose in appropriate cases.

J. K. Davidson

Bibliography

Mould, R. F. (1980). A history of X-rays and radium. IPC Business Press Ltd, Sutton, Surrey.

See also imaging techniques; radiation, ionizing; radiology.