1895: X-rays Discovered

On 8th November, 1895 William Röntgen made a discovery that would revolutionise physics and medicine.

At the time, Röntgen was working at the University of Würzburg. His experiments focussed on the light emitted from “Crookes tubes,” glass tubes with the air expelled from them and fitted with electrodes. When a high electric voltage is sent through the tube the result is a green fluorescent light. Röntgen realised that when he wrapped a piece of thick black card around the tube, a green glow appeared on a surface a few feet away. He concluded that the glow was caused by invisible rays that were capable of penetrating the card.

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Over the coming weeks, Röntgen continued to experiment with his new rays. He realised they were able to pass through substances other than paper. In fact, they could pass through the soft tissues of the body, creating images of the bones and metal. During his experiments, he produced an image of his wife’s hand wearing her wedding ring.

concern over X-ray glasses led to the production of lead underwear

News of Röntgen’s discovery spread globally and the medical community realised quickly that this was a major breakthrough. Within a year, the new X-ray was being used in diagnosis and treatment. It would take much longer however, for the scientific community to comprehend the damage that radiation caused.

The X-ray also captured the public’s imagination. People queued up to have ‘bone portraits’ taken and concern over X-ray glasses led to the production of lead underwear to protect modesty.

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In 1901, Röntgen received the first Novel Prize in physics. He donated the money from the Nobel Prize to the University of Würzburg and never took out any patents on his work in order that it might be used globally.

Wilhelm Conrad Röntgen

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Wilhelm Conrad Röntgen, Röntgen also spelled Roentgen, (born March 27, 1845, Lennep, Prussia [now Remscheid, Germany]—died February 10, 1923, Munich, Germany), physicist who was a recipient of the first Nobel Prize for Physics, in 1901, for his discovery of X-rays, which heralded the age of modern physics and revolutionized diagnostic medicine.

Röntgen studied at the Polytechnic in Zürich and then was professor of physics at the universities of Strasbourg (1876–79), Giessen (1879–88), Würzburg (1888–1900), and Munich (1900–20). His research also included work on elasticity, capillary action of fluids, specific heats of gases, conduction of heat in crystals, absorption of heat by gases, and piezoelectricity.

In 1895, while experimenting with electric current flow in a partially evacuated glass tube (cathode-ray tube), Röntgen observed that a nearby piece of barium platinocyanide gave off light when the tube was in operation. He theorized that when the cathode rays (electrons) struck the glass wall of the tube, some unknown radiation was formed that traveled across the room, struck the chemical, and caused the fluorescence. Further investigation revealed that paper, wood, and aluminum, among other materials, are transparent to this new form of radiation. He found that it affected photographic plates, and, since it did not noticeably exhibit any properties of light, such as reflection or refraction, he mistakenly thought the rays were unrelated to light. In view of its uncertain nature, he called the phenomenon X-radiation, though it also became known as Röntgen radiation. He took the first X-ray photographs, of the interiors of metal objects and of the bones in his wife’s hand.

This article was most recently revised and updated by Amy Tikkanen, Corrections Manager.

X-rays: laying the foundation of modern radiology, 1896-1930

The authors describe the initial impact and far-reaching consequences of the discovery of x-rays in 1895. Roentgen was quick to realise the importance of this mysterious new kind of ray he had discovered. As early as 1896 x-rays were already being used in surgery and medicine, replacing Bell's telephonic needle probe, which could only detect metallic objects by sound and was therefore limited to the location of objects such as bullets for removel. As x-ray diagnosis became more accurate, radiological techniques were gradually improved over the years and progressed from examination of the skeleton to imaging complex internal organs. The x-ray became vital in the detection of tuberculosis, for which it is still used today. Through the use of opaque substances such as barium sulfate it became possible to visualise the digestive tract and later advances in photographic techniques made visible the brain and almost all parts of the body. Meanwhile the dangers of radiation were recognized and after 1930 safety measures were introduced to protect radiologists and patients against overexposure. In the hundred years since its discovery the ever-widening scope of radiology has made it a fundamental resource in medical diagnosis and treatment.

History of Medicine: Dr. Roentgen’s Accidental X-Rays

In today’s world, doctors order X-rays to diagnose all sorts of problems: a broken bone, pneumonia, heart failure, and much, much more. Mammography, the standard screening method for breast cancer, uses X-rays. We barely think about it, it’s so ubiquitous. But not so long ago, a broken bone, a tumor, or a swallowed object could not be found without cutting a person open.

Wilhelm Roentgen, Professor of Physics in Wurzburg, Bavaria, discovered X-rays in 1895—accidentally—while testing whether cathode rays could pass through glass. His cathode tube was covered in heavy black paper, so he was surprised when an incandescent green light nevertheless escaped and projected onto a nearby fluorescent screen. Through experimentation, he found that the mysterious light would pass through most substances but leave shadows of solid objects. Because he did not know what the rays were, he called them ‘X,’ meaning ‘unknown,’ rays.

Roentgen quickly found that X-rays would pass through human tissue too, rendering the bones and tissue beneath visible. News of his discovery spread worldwide, and within a year, doctors in Europe and the United States were using X-rays to locate gun shots, bone fractures, kidney stones and swallowed objects. Honors for his work poured in--including the first Nobel Prize in physics in 1901.

Clinical use of the X-ray flourished, with little regard for potential side effects from radiation exposure. There were a few early suspicions from scientists including Thomas Edison, Nikola Tesla, and William J. Morton, each of whom reported injuries they believed resulted from experiments with X-rays. But overall, early use of X-rays was widespread and unrestrained, even to the degree that during the 1930’s and 1940’s, shoe stores offered free X-rays so that customers could see the bones in their feet.

We now have a far better understanding of the risks associated with X-ray radiation and have developed protocols to greatly minimize unnecessary exposure. And while X-rays remain a cornerstone of modern medicine, their discovery paved the way for the development of today’s broad spectrum of imaging techniques, including magnetic resonance imaging (MRI), computed tomography (CT), ultrasound, echocardiography, and many others -- some of which avoid the use of radiation altogether. Not a bad legacy for an accidental discovery.

A wake up call…

Interestingly, it wasn’t the x-ray which made known the fact that ionizing radiation wasn’t something to play with. Rather, it was the mishaps of the similar novelty of the time, Radium, which put an end to most of the nonsense.

Radium is an element that emits huge quantities of alpha particles and gamma rays which, like x-rays, “Had the power to cure any ailment”. As such, it was added to everything from wristbands to drinking water and was bought by the public en masse.

Circa 1917, thousands of women were working in shops to paint the dials of watches with radium-containing luminescent paint. Ideally, this wouldn’t have been anything special, but unfortunately paintbrushes lose their shape after a few strokes. To keep them sharp, women would use their mouths to adjust their shape.

Many women eventually died of radium jaw a disease of the bone that often results in the jaw literally falling off. This, coupled with the death of socialite Eben Byers finally let the public know, large amounts of radiation are dangerous.

Wilhelm Conrad Röntgen Takes the First X-Ray

On 8 Nov 1895, Wilhelm Conrad Röntgen (accidentally) discovered an image cast from his cathode ray generator, projected far beyond the possible range of the cathode rays (now known as an electron beam). Further investigation showed that the rays were generated at the point of contact of the cathode ray beam on the interior of the vacuum tube, that they were not deflected by magnetic fields, and they penetrated many kinds of matter.

A week after his discovery, Rontgen took an x-ray photograph of his wife's hand which clearly revealed her wedding ring and her bones. The photograph electrified the general public and aroused great scientific interest in the new form of radiation. Röntgen named the new form of radiation x-radiation (X standing for "Unknown"). Hence the term x-rays (also referred to as Röntgen rays, though this term is unusual outside of Germany).


Pre-Röntgen observations and research Edit

Before their discovery in 1895, X-rays were just a type of unidentified radiation emanating from experimental discharge tubes. They were noticed by scientists investigating cathode rays produced by such tubes, which are energetic electron beams that were first observed in 1869. Many of the early Crookes tubes (invented around 1875) undoubtedly radiated X-rays, because early researchers noticed effects that were attributable to them, as detailed below. Crookes tubes created free electrons by ionization of the residual air in the tube by a high DC voltage of anywhere between a few kilovolts and 100 kV. This voltage accelerated the electrons coming from the cathode to a high enough velocity that they created X-rays when they struck the anode or the glass wall of the tube. [4]

The earliest experimenter thought to have (unknowingly) produced X-rays was actuary William Morgan. In 1785 he presented a paper to the Royal Society of London describing the effects of passing electrical currents through a partially evacuated glass tube, producing a glow created by X-rays. [5] [6] This work was further explored by Humphry Davy and his assistant Michael Faraday.

When Stanford University physics professor Fernando Sanford created his "electric photography" he also unknowingly generated and detected X-rays. From 1886 to 1888 he had studied in the Hermann Helmholtz laboratory in Berlin, where he became familiar with the cathode rays generated in vacuum tubes when a voltage was applied across separate electrodes, as previously studied by Heinrich Hertz and Philipp Lenard. His letter of January 6, 1893 (describing his discovery as "electric photography") to The Physical Review was duly published and an article entitled Without Lens or Light, Photographs Taken With Plate and Object in Darkness appeared in the San Francisco Examiner. [7]

Starting in 1888, Philipp Lenard conducted experiments to see whether cathode rays could pass out of the Crookes tube into the air. He built a Crookes tube with a "window" at the end made of thin aluminum, facing the cathode so the cathode rays would strike it (later called a "Lenard tube"). He found that something came through, that would expose photographic plates and cause fluorescence. He measured the penetrating power of these rays through various materials. It has been suggested that at least some of these "Lenard rays" were actually X-rays. [8]

In 1889 Ukrainian-born Ivan Puluj, a lecturer in experimental physics at the Prague Polytechnic who since 1877 had been constructing various designs of gas-filled tubes to investigate their properties, published a paper on how sealed photographic plates became dark when exposed to the emanations from the tubes. [9]

Hermann von Helmholtz formulated mathematical equations for X-rays. He postulated a dispersion theory before Röntgen made his discovery and announcement. It was formed on the basis of the electromagnetic theory of light. [10] However, he did not work with actual X-rays.

In 1894 Nikola Tesla noticed damaged film in his lab that seemed to be associated with Crookes tube experiments and began investigating this radiant energy of "invisible" kinds. [11] [12] After Röntgen identified the X-ray, Tesla began making X-ray images of his own using high voltages and tubes of his own design, [13] as well as Crookes tubes.

Discovery by Röntgen Edit

On November 8, 1895, German physics professor Wilhelm Röntgen stumbled on X-rays while experimenting with Lenard tubes and Crookes tubes and began studying them. He wrote an initial report "On a new kind of ray: A preliminary communication" and on December 28, 1895 submitted it to Würzburg's Physical-Medical Society journal. [14] This was the first paper written on X-rays. Röntgen referred to the radiation as "X", to indicate that it was an unknown type of radiation. The name stuck, although (over Röntgen's great objections) many of his colleagues suggested calling them Röntgen rays. They are still referred to as such in many languages, including German, Hungarian, Ukrainian, Danish, Polish, Bulgarian, Swedish, Finnish, Estonian, Turkish, Russian, Latvian, Lithuanian, Japanese, Dutch, Georgian, Hebrew and Norwegian. Röntgen received the first Nobel Prize in Physics for his discovery. [15]

There are conflicting accounts of his discovery because Röntgen had his lab notes burned after his death, but this is a likely reconstruction by his biographers: [16] [17] Röntgen was investigating cathode rays from a Crookes tube which he had wrapped in black cardboard so that the visible light from the tube would not interfere, using a fluorescent screen painted with barium platinocyanide. He noticed a faint green glow from the screen, about 1 meter away. Röntgen realized some invisible rays coming from the tube were passing through the cardboard to make the screen glow. He found they could also pass through books and papers on his desk. Röntgen threw himself into investigating these unknown rays systematically. Two months after his initial discovery, he published his paper. [18]

Röntgen discovered their medical use when he made a picture of his wife's hand on a photographic plate formed due to X-rays. The photograph of his wife's hand was the first photograph of a human body part using X-rays. When she saw the picture, she said "I have seen my death." [21]

The discovery of X-rays stimulated a veritable sensation. Röntgen's biographer Otto Glasser estimated that, in 1896 alone, as many as 49 essays and 1044 articles about the new rays were published. [22] This was probably a conservative estimate, if one considers that nearly every paper around the world extensively reported about the new discovery, with a magazine such as Science dedicating as many as 23 articles to it in that year alone. [23] Sensationalist reactions to the new discovery included publications linking the new kind of rays to occult and paranormal theories, such as telepathy. [24] [25]

Advances in radiology Edit

Röntgen immediately noticed X-rays could have medical applications. Along with his 28 December Physical-Medical Society submission he sent a letter to physicians he knew around Europe (January 1, 1896). [26] News (and the creation of "shadowgrams") spread rapidly with Scottish electrical engineer Alan Archibald Campbell-Swinton being the first after Röntgen to create an X-ray (of a hand). Through February there were 46 experimenters taking up the technique in North America alone. [26]

The first use of X-rays under clinical conditions was by John Hall-Edwards in Birmingham, England on 11 January 1896, when he radiographed a needle stuck in the hand of an associate. On February 14, 1896, Hall-Edwards was also the first to use X-rays in a surgical operation. [27] In early 1896, several weeks after Röntgen's discovery, Ivan Romanovich Tarkhanov irradiated frogs and insects with X-rays, concluding that the rays "not only photograph, but also affect the living function". [28]

The first medical X-ray made in the United States was obtained using a discharge tube of Pului's design. In January 1896, on reading of Röntgen's discovery, Frank Austin of Dartmouth College tested all of the discharge tubes in the physics laboratory and found that only the Pului tube produced X-rays. This was a result of Pului's inclusion of an oblique "target" of mica, used for holding samples of fluorescent material, within the tube. On 3 February 1896 Gilman Frost, professor of medicine at the college, and his brother Edwin Frost, professor of physics, exposed the wrist of Eddie McCarthy, whom Gilman had treated some weeks earlier for a fracture, to the X-rays and collected the resulting image of the broken bone on gelatin photographic plates obtained from Howard Langill, a local photographer also interested in Röntgen's work. [29]

Many experimenters, including Röntgen himself in his original experiments, came up with methods to view X-ray images "live" using some form of luminescent screen. [26] Röntgen used a screen coated with barium platinocyanide. On February 5, 1896, live imaging devices were developed by both Italian scientist Enrico Salvioni (his "cryptoscope") and Professor McGie of Princeton University (his "Skiascope"), both using barium platinocyanide. American inventor Thomas Edison started research soon after Röntgen's discovery and investigated materials' ability to fluoresce when exposed to X-rays, finding that calcium tungstate was the most effective substance. In May 1896 he developed the first mass-produced live imaging device, his "Vitascope", later called the fluoroscope, which became the standard for medical X-ray examinations. [26] Edison dropped X-ray research around 1903, before the death of Clarence Madison Dally, one of his glassblowers. Dally had a habit of testing X-ray tubes on his own hands, developing a cancer in them so tenacious that both arms were amputated in a futile attempt to save his life in 1904, he became the first known death attributed to X-ray exposure. [26] During the time the fluoroscope was being developed, Serbian American physicist Mihajlo Pupin, using a calcium tungstate screen developed by Edison, found that using a fluorescent screen decreased the exposure time it took to create an X-ray for medical imaging from an hour to a few minutes. [30] [26]

In 1901, U.S. President William McKinley was shot twice in an assassination attempt. While one bullet only grazed his sternum, another had lodged somewhere deep inside his abdomen and could not be found. A worried McKinley aide sent word to inventor Thomas Edison to rush an X-ray machine to Buffalo to find the stray bullet. It arrived but was not used. While the shooting itself had not been lethal, gangrene had developed along the path of the bullet, and McKinley died of septic shock due to bacterial infection six days later. [31]

Hazards discovered Edit

With the widespread experimentation with x‑rays after their discovery in 1895 by scientists, physicians, and inventors came many stories of burns, hair loss, and worse in technical journals of the time. In February 1896, Professor John Daniel and Dr. William Lofland Dudley of Vanderbilt University reported hair loss after Dr. Dudley was X-rayed. A child who had been shot in the head was brought to the Vanderbilt laboratory in 1896. Before trying to find the bullet an experiment was attempted, for which Dudley "with his characteristic devotion to science" [32] [33] [34] volunteered. Daniel reported that 21 days after taking a picture of Dudley's skull (with an exposure time of one hour), he noticed a bald spot 2 inches (5.1 cm) in diameter on the part of his head nearest the X-ray tube: "A plate holder with the plates towards the side of the skull was fastened and a coin placed between the skull and the head. The tube was fastened at the other side at a distance of one-half inch from the hair." [35]

In August 1896 Dr. HD. Hawks, a graduate of Columbia College, suffered severe hand and chest burns from an x-ray demonstration. It was reported in Electrical Review and led to many other reports of problems associated with x-rays being sent in to the publication. [36] Many experimenters including Elihu Thomson at Edison's lab, William J. Morton, and Nikola Tesla also reported burns. Elihu Thomson deliberately exposed a finger to an x-ray tube over a period of time and suffered pain, swelling, and blistering. [37] Other effects were sometimes blamed for the damage including ultraviolet rays and (according to Tesla) ozone. [38] Many physicians claimed there were no effects from X-ray exposure at all. [37] On August 3, 1905, in San Francisco, California, Elizabeth Fleischman, an American X-ray pioneer, died from complications as a result of her work with X-rays. [39] [40] [41]

20th century and beyond Edit

The many applications of X-rays immediately generated enormous interest. Workshops began making specialized versions of Crookes tubes for generating X-rays and these first-generation cold cathode or Crookes X-ray tubes were used until about 1920.

A typical early 20th century medical x-ray system consisted of a Ruhmkorff coil connected to a cold cathode Crookes X-ray tube. A spark gap was typically connected to the high voltage side in parallel to the tube and used for diagnostic purposes. [42] The spark gap allowed detecting the polarity of the sparks, measuring voltage by the length of the sparks thus determining the "hardness" of the vacuum of the tube, and it provided a load in the event the X-ray tube was disconnected. To detect the hardness of the tube, the spark gap was initially opened to the widest setting. While the coil was operating, the operator reduced the gap until sparks began to appear. A tube in which the spark gap began to spark at around 2 1/2 inches was considered soft (low vacuum) and suitable for thin body parts such as hands and arms. A 5-inch spark indicated the tube was suitable for shoulders and knees. A 7–9 inch spark would indicate a higher vacuum suitable for imaging the abdomen of larger individuals. Since the spark gap was connected in parallel to the tube, the spark gap had to be opened until the sparking ceased in order to operate the tube for imaging. Exposure time for photographic plates was around half a minute for a hand to a couple of minutes for a thorax. The plates may have a small addition of fluorescent salt to reduce exposure times. [42]

Crookes tubes were unreliable. They had to contain a small quantity of gas (invariably air) as a current will not flow in such a tube if they are fully evacuated. However, as time passed, the X-rays caused the glass to absorb the gas, causing the tube to generate "harder" X-rays until it soon stopped operating. Larger and more frequently used tubes were provided with devices for restoring the air, known as "softeners". These often took the form of a small side tube that contained a small piece of mica, a mineral that traps relatively large quantities of air within its structure. A small electrical heater heated the mica, causing it to release a small amount of air, thus restoring the tube's efficiency. However, the mica had a limited life, and the restoration process was difficult to control.

In 1904, John Ambrose Fleming invented the thermionic diode, the first kind of vacuum tube. This used a hot cathode that caused an electric current to flow in a vacuum. This idea was quickly applied to X-ray tubes, and hence heated-cathode X-ray tubes, called "Coolidge tubes", completely replaced the troublesome cold cathode tubes by about 1920.

In about 1906, the physicist Charles Barkla discovered that X-rays could be scattered by gases, and that each element had a characteristic X-ray spectrum. He won the 1917 Nobel Prize in Physics for this discovery.

In 1912, Max von Laue, Paul Knipping, and Walter Friedrich first observed the diffraction of X-rays by crystals. This discovery, along with the early work of Paul Peter Ewald, William Henry Bragg, and William Lawrence Bragg, gave birth to the field of X-ray crystallography.

In 1913, Henry Moseley performed crystallography experiments with X-rays emanating from various metals and formulated Moseley's law which relates the frequency of the X-rays to the atomic number of the metal.

The Coolidge X-ray tube was invented the same year by William D. Coolidge. It made possible the continuous emissions of X-rays. Modern X-ray tubes are based on this design, often employing the use of rotating targets which allow for significantly higher heat dissipation than static targets, further allowing higher quantity X-ray output for use in high powered applications such as rotational CT scanners.

The use of X-rays for medical purposes (which developed into the field of radiation therapy) was pioneered by Major John Hall-Edwards in Birmingham, England. Then in 1908, he had to have his left arm amputated because of the spread of X-ray dermatitis on his arm. [43]

Medical science also used the motion picture to study human physiology. In 1913, a motion picture was made in Detroit showing a hard-boiled egg inside a human stomach. This early x-ray movie was recorded at a rate of one still image every four seconds. [44] Dr Lewis Gregory Cole of New York was a pioneer of the technique, which he called "serial radiography". [45] [46] In 1918, x-rays were used in association with motion picture cameras to capture the human skeleton in motion. [47] [48] [49] In 1920, it was used to record the movements of tongue and teeth in the study of languages by the Institute of Phonetics in England. [50]

In 1914 Marie Curie developed radiological cars to support soldiers injured in World War I. The cars would allow for rapid X-ray imaging of wounded soldiers so battlefield surgeons could quickly and more accurately operate. [51]

From the early 1920s through to the 1950s, X-ray machines were developed to assist in the fitting of shoes [52] and were sold to commercial shoe stores. [53] [54] [55] Concerns regarding the impact of frequent or poorly controlled use were expressed in the 1950s, [56] [57] leading to the practice's eventual end that decade. [58]

The X-ray microscope was developed during the 1950s.

The Chandra X-ray Observatory, launched on July 23, 1999, has been allowing the exploration of the very violent processes in the universe which produce X-rays. Unlike visible light, which gives a relatively stable view of the universe, the X-ray universe is unstable. It features stars being torn apart by black holes, galactic collisions, and novae, and neutron stars that build up layers of plasma that then explode into space.

An X-ray laser device was proposed as part of the Reagan Administration's Strategic Defense Initiative in the 1980s, but the only test of the device (a sort of laser "blaster" or death ray, powered by a thermonuclear explosion) gave inconclusive results. For technical and political reasons, the overall project (including the X-ray laser) was de-funded (though was later revived by the second Bush Administration as National Missile Defense using different technologies).

Phase-contrast X-ray imaging refers to a variety of techniques that use phase information of a coherent X-ray beam to image soft tissues. It has become an important method for visualizing cellular and histological structures in a wide range of biological and medical studies. There are several technologies being used for X-ray phase-contrast imaging, all utilizing different principles to convert phase variations in the X-rays emerging from an object into intensity variations. [59] [60] These include propagation-based phase contrast, [61] Talbot interferometry, [60] refraction-enhanced imaging, [62] and X-ray interferometry. [63] These methods provide higher contrast compared to normal absorption-contrast X-ray imaging, making it possible to see smaller details. A disadvantage is that these methods require more sophisticated equipment, such as synchrotron or microfocus X-ray sources, X-ray optics, and high resolution X-ray detectors.

Soft and hard X-rays Edit

X-rays with high photon energies above 5–10 keV (below 0.2–0.1 nm wavelength) are called hard X-rays, while those with lower energy (and longer wavelength) are called soft X-rays. [64] The intermediate range with photon energies of several keV is often referred to as tender X-rays. Due to their penetrating ability, hard X-rays are widely used to image the inside of objects, e.g., in medical radiography and airport security. The term X-ray is metonymically used to refer to a radiographic image produced using this method, in addition to the method itself. Since the wavelengths of hard X-rays are similar to the size of atoms, they are also useful for determining crystal structures by X-ray crystallography. By contrast, soft X-rays are easily absorbed in air the attenuation length of 600 eV (

2 nm) X-rays in water is less than 1 micrometer. [65]

Gamma rays Edit

There is no consensus for a definition distinguishing between X-rays and gamma rays. One common practice is to distinguish between the two types of radiation based on their source: X-rays are emitted by electrons, while gamma rays are emitted by the atomic nucleus. [66] [67] [68] [69] This definition has several problems: other processes also can generate these high-energy photons, or sometimes the method of generation is not known. One common alternative is to distinguish X- and gamma radiation on the basis of wavelength (or, equivalently, frequency or photon energy), with radiation shorter than some arbitrary wavelength, such as 10 −11 m (0.1 Å), defined as gamma radiation. [70] This criterion assigns a photon to an unambiguous category, but is only possible if wavelength is known. (Some measurement techniques do not distinguish between detected wavelengths.) However, these two definitions often coincide since the electromagnetic radiation emitted by X-ray tubes generally has a longer wavelength and lower photon energy than the radiation emitted by radioactive nuclei. [66] Occasionally, one term or the other is used in specific contexts due to historical precedent, based on measurement (detection) technique, or based on their intended use rather than their wavelength or source. Thus, gamma-rays generated for medical and industrial uses, for example radiotherapy, in the ranges of 6–20 MeV, can in this context also be referred to as X-rays. [71]

X-ray photons carry enough energy to ionize atoms and disrupt molecular bonds. This makes it a type of ionizing radiation, and therefore harmful to living tissue. A very high radiation dose over a short period of time causes radiation sickness, while lower doses can give an increased risk of radiation-induced cancer. In medical imaging, this increased cancer risk is generally greatly outweighed by the benefits of the examination. The ionizing capability of X-rays can be utilized in cancer treatment to kill malignant cells using radiation therapy. It is also used for material characterization using X-ray spectroscopy.

Hard X-rays can traverse relatively thick objects without being much absorbed or scattered. For this reason, X-rays are widely used to image the inside of visually opaque objects. The most often seen applications are in medical radiography and airport security scanners, but similar techniques are also important in industry (e.g. industrial radiography and industrial CT scanning) and research (e.g. small animal CT). The penetration depth varies with several orders of magnitude over the X-ray spectrum. This allows the photon energy to be adjusted for the application so as to give sufficient transmission through the object and at the same time provide good contrast in the image.

X-rays have much shorter wavelengths than visible light, which makes it possible to probe structures much smaller than can be seen using a normal microscope. This property is used in X-ray microscopy to acquire high-resolution images, and also in X-ray crystallography to determine the positions of atoms in crystals.

X-rays interact with matter in three main ways, through photoabsorption, Compton scattering, and Rayleigh scattering. The strength of these interactions depends on the energy of the X-rays and the elemental composition of the material, but not much on chemical properties, since the X-ray photon energy is much higher than chemical binding energies. Photoabsorption or photoelectric absorption is the dominant interaction mechanism in the soft X-ray regime and for the lower hard X-ray energies. At higher energies, Compton scattering dominates.

Photoelectric absorption Edit

The probability of a photoelectric absorption per unit mass is approximately proportional to Z 3 /E 3 , where Z is the atomic number and E is the energy of the incident photon. [72] This rule is not valid close to inner shell electron binding energies where there are abrupt changes in interaction probability, so called absorption edges. However, the general trend of high absorption coefficients and thus short penetration depths for low photon energies and high atomic numbers is very strong. For soft tissue, photoabsorption dominates up to about 26 keV photon energy where Compton scattering takes over. For higher atomic number substances this limit is higher. The high amount of calcium (Z = 20) in bones, together with their high density, is what makes them show up so clearly on medical radiographs.

A photoabsorbed photon transfers all its energy to the electron with which it interacts, thus ionizing the atom to which the electron was bound and producing a photoelectron that is likely to ionize more atoms in its path. An outer electron will fill the vacant electron position and produce either a characteristic X-ray or an Auger electron. These effects can be used for elemental detection through X-ray spectroscopy or Auger electron spectroscopy.

Compton scattering Edit

Compton scattering is the predominant interaction between X-rays and soft tissue in medical imaging. [73] Compton scattering is an inelastic scattering of the X-ray photon by an outer shell electron. Part of the energy of the photon is transferred to the scattering electron, thereby ionizing the atom and increasing the wavelength of the X-ray. The scattered photon can go in any direction, but a direction similar to the original direction is more likely, especially for high-energy X-rays. The probability for different scattering angles is described by the Klein–Nishina formula. The transferred energy can be directly obtained from the scattering angle from the conservation of energy and momentum.

Rayleigh scattering Edit

Rayleigh scattering is the dominant elastic scattering mechanism in the X-ray regime. [74] Inelastic forward scattering gives rise to the refractive index, which for X-rays is only slightly below 1. [75]

Whenever charged particles (electrons or ions) of sufficient energy hit a material, X-rays are produced.

Production by electrons Edit

Characteristic X-ray emission lines for some common anode materials. [76] [77]
Photon energy [keV] Wavelength [nm]
Kα1 Kβ1 Kα1 Kβ1
W 74 59.3 67.2 0.0209 0.0184
Mo 42 17.5 19.6 0.0709 0.0632
Cu 29 8.05 8.91 0.154 0.139
Ag 47 22.2 24.9 0.0559 0.0497
Ga 31 9.25 10.26 0.134 0.121
In 49 24.2 27.3 0.0512 0.455

X-rays can be generated by an X-ray tube, a vacuum tube that uses a high voltage to accelerate the electrons released by a hot cathode to a high velocity. The high velocity electrons collide with a metal target, the anode, creating the X-rays. [78] In medical X-ray tubes the target is usually tungsten or a more crack-resistant alloy of rhenium (5%) and tungsten (95%), but sometimes molybdenum for more specialized applications, such as when softer X-rays are needed as in mammography. In crystallography, a copper target is most common, with cobalt often being used when fluorescence from iron content in the sample might otherwise present a problem.

The maximum energy of the produced X-ray photon is limited by the energy of the incident electron, which is equal to the voltage on the tube times the electron charge, so an 80 kV tube cannot create X-rays with an energy greater than 80 keV. When the electrons hit the target, X-rays are created by two different atomic processes:

  1. Characteristic X-ray emission (X-ray electroluminescence): If the electron has enough energy, it can knock an orbital electron out of the inner electron shell of the target atom. After that, electrons from higher energy levels fill the vacancies, and X-ray photons are emitted. This process produces an emission spectrum of X-rays at a few discrete frequencies, sometimes referred to as spectral lines. Usually, these are transitions from the upper shells to the K shell (called K lines), to the L shell (called L lines) and so on. If the transition is from 2p to 1s, it is called Kα, while if it is from 3p to 1s it is Kβ. The frequencies of these lines depend on the material of the target and are therefore called characteristic lines. The Kα line usually has greater intensity than the Kβ one and is more desirable in diffraction experiments. Thus the Kβ line is filtered out by a filter. The filter is usually made of a metal having one proton less than the anode material (e.g., Ni filter for Cu anode or Nb filter for Mo anode).
  2. Bremsstrahlung: This is radiation given off by the electrons as they are scattered by the strong electric field near the high-Z (proton number) nuclei. These X-rays have a continuous spectrum. The frequency of bremsstrahlung is limited by the energy of incident electrons.

So, the resulting output of a tube consists of a continuous bremsstrahlung spectrum falling off to zero at the tube voltage, plus several spikes at the characteristic lines. The voltages used in diagnostic X-ray tubes range from roughly 20 kV to 150 kV and thus the highest energies of the X-ray photons range from roughly 20 keV to 150 keV. [79]

Both of these X-ray production processes are inefficient, with only about one percent of the electrical energy used by the tube converted into X-rays, and thus most of the electric power consumed by the tube is released as waste heat. When producing a usable flux of X-rays, the X-ray tube must be designed to dissipate the excess heat.

A specialized source of X-rays which is becoming widely used in research is synchrotron radiation, which is generated by particle accelerators. Its unique features are X-ray outputs many orders of magnitude greater than those of X-ray tubes, wide X-ray spectra, excellent collimation, and linear polarization. [80]

Short nanosecond bursts of X-rays peaking at 15-keV in energy may be reliably produced by peeling pressure-sensitive adhesive tape from its backing in a moderate vacuum. This is likely to be the result of recombination of electrical charges produced by triboelectric charging. The intensity of X-ray triboluminescence is sufficient for it to be used as a source for X-ray imaging. [81]

Production by fast positive ions Edit

X-rays can also be produced by fast protons or other positive ions. The proton-induced X-ray emission or particle-induced X-ray emission is widely used as an analytical procedure. For high energies, the production cross section is proportional to Z1 2 Z2 −4 , where Z1 refers to the atomic number of the ion, Z2 refers to that of the target atom. [82] An overview of these cross sections is given in the same reference.

Production in lightning and laboratory discharges Edit

X-rays are also produced in lightning accompanying terrestrial gamma-ray flashes. The underlying mechanism is the acceleration of electrons in lightning related electric fields and the subsequent production of photons through Bremsstrahlung. [83] This produces photons with energies of some few keV and several tens of MeV. [84] In laboratory discharges with a gap size of approximately 1 meter length and a peak voltage of 1 MV, X-rays with a characteristic energy of 160 keV are observed. [85] A possible explanation is the encounter of two streamers and the production of high-energy run-away electrons [86] however, microscopic simulations have shown that the duration of electric field enhancement between two streamers is too short to produce a significant number of run-away electrons. [87] Recently, it has been proposed that air perturbations in the vicinity of streamers can facilitate the production of run-away electrons and hence of X-rays from discharges. [88] [89]

X-ray detectors vary in shape and function depending on their purpose. Imaging detectors such as those used for radiography were originally based on photographic plates and later photographic film, but are now mostly replaced by various digital detector types such as image plates and flat panel detectors. For radiation protection direct exposure hazard is often evaluated using ionization chambers, while dosimeters are used to measure the radiation dose a person has been exposed to. X-ray spectra can be measured either by energy dispersive or wavelength dispersive spectrometers. For x-ray diffraction applications, such as x-ray crystallography, hybrid photon counting detectors are widely used. [90]

Since Röntgen's discovery that X-rays can identify bone structures, X-rays have been used for medical imaging. [91] The first medical use was less than a month after his paper on the subject. [29] Up to 2010, five billion medical imaging examinations had been conducted worldwide. [92] Radiation exposure from medical imaging in 2006 made up about 50% of total ionizing radiation exposure in the United States. [93]

Projectional radiographs Edit

Projectional radiography is the practice of producing two-dimensional images using x-ray radiation. Bones contain a high concentration of calcium, which, due to its relatively high atomic number, absorbs x-rays efficiently. This reduces the amount of X-rays reaching the detector in the shadow of the bones, making them clearly visible on the radiograph. The lungs and trapped gas also show up clearly because of lower absorption compared to tissue, while differences between tissue types are harder to see.

Projectional radiographs are useful in the detection of pathology of the skeletal system as well as for detecting some disease processes in soft tissue. Some notable examples are the very common chest X-ray, which can be used to identify lung diseases such as pneumonia, lung cancer, or pulmonary edema, and the abdominal x-ray, which can detect bowel (or intestinal) obstruction, free air (from visceral perforations) and free fluid (in ascites). X-rays may also be used to detect pathology such as gallstones (which are rarely radiopaque) or kidney stones which are often (but not always) visible. Traditional plain X-rays are less useful in the imaging of soft tissues such as the brain or muscle. One area where projectional radiographs are used extensively is in evaluating how an orthopedic implant, such as a knee, hip or shoulder replacement, is situated in the body with respect to the surrounding bone. This can be assessed in two dimensions from plain radiographs, or it can be assessed in three dimensions if a technique called '2D to 3D registration' is used. This technique purportedly negates projection errors associated with evaluating implant position from plain radiographs. [94] [95]

Dental radiography is commonly used in the diagnoses of common oral problems, such as cavities.

In medical diagnostic applications, the low energy (soft) X-rays are unwanted, since they are totally absorbed by the body, increasing the radiation dose without contributing to the image. Hence, a thin metal sheet, often of aluminium, called an X-ray filter, is usually placed over the window of the X-ray tube, absorbing the low energy part in the spectrum. This is called hardening the beam since it shifts the center of the spectrum towards higher energy (or harder) x-rays.

To generate an image of the cardiovascular system, including the arteries and veins (angiography) an initial image is taken of the anatomical region of interest. A second image is then taken of the same region after an iodinated contrast agent has been injected into the blood vessels within this area. These two images are then digitally subtracted, leaving an image of only the iodinated contrast outlining the blood vessels. The radiologist or surgeon then compares the image obtained to normal anatomical images to determine whether there is any damage or blockage of the vessel.

Computed tomography Edit

Computed tomography (CT scanning) is a medical imaging modality where tomographic images or slices of specific areas of the body are obtained from a large series of two-dimensional X-ray images taken in different directions. [96] These cross-sectional images can be combined into a three-dimensional image of the inside of the body and used for diagnostic and therapeutic purposes in various medical disciplines.

Fluoroscopy Edit

Fluoroscopy is an imaging technique commonly used by physicians or radiation therapists to obtain real-time moving images of the internal structures of a patient through the use of a fluoroscope. In its simplest form, a fluoroscope consists of an X-ray source and a fluorescent screen, between which a patient is placed. However, modern fluoroscopes couple the screen to an X-ray image intensifier and CCD video camera allowing the images to be recorded and played on a monitor. This method may use a contrast material. Examples include cardiac catheterization (to examine for coronary artery blockages) and barium swallow (to examine for esophageal disorders and swallowing disorders).

Radiotherapy Edit

The use of X-rays as a treatment is known as radiation therapy and is largely used for the management (including palliation) of cancer it requires higher radiation doses than those received for imaging alone. X-rays beams are used for treating skin cancers using lower energy x-ray beams while higher energy beams are used for treating cancers within the body such as brain, lung, prostate, and breast. [97] [98]

Diagnostic X-rays (primarily from CT scans due to the large dose used) increase the risk of developmental problems and cancer in those exposed. [99] [100] [101] X-rays are classified as a carcinogen by both the World Health Organization's International Agency for Research on Cancer and the U.S. government. [92] [102] It is estimated that 0.4% of current cancers in the United States are due to computed tomography (CT scans) performed in the past and that this may increase to as high as 1.5–2% with 2007 rates of CT usage. [103]

Experimental and epidemiological data currently do not support the proposition that there is a threshold dose of radiation below which there is no increased risk of cancer. [104] However, this is under increasing doubt. [105] It is estimated that the additional radiation from diagnostic X-rays will increase the average person's cumulative risk of getting cancer by age 75 by 0.6–3.0%. [106] The amount of absorbed radiation depends upon the type of X-ray test and the body part involved. [107] CT and fluoroscopy entail higher doses of radiation than do plain X-rays.

To place the increased risk in perspective, a plain chest X-ray will expose a person to the same amount from background radiation that people are exposed to (depending upon location) every day over 10 days, while exposure from a dental X-ray is approximately equivalent to 1 day of environmental background radiation. [108] Each such X-ray would add less than 1 per 1,000,000 to the lifetime cancer risk. An abdominal or chest CT would be the equivalent to 2–3 years of background radiation to the whole body, or 4–5 years to the abdomen or chest, increasing the lifetime cancer risk between 1 per 1,000 to 1 per 10,000. [108] This is compared to the roughly 40% chance of a US citizen developing cancer during their lifetime. [109] For instance, the effective dose to the torso from a CT scan of the chest is about 5 mSv, and the absorbed dose is about 14 mGy. [110] A head CT scan (1.5mSv, 64mGy) [111] that is performed once with and once without contrast agent, would be equivalent to 40 years of background radiation to the head. Accurate estimation of effective doses due to CT is difficult with the estimation uncertainty range of about ±19% to ±32% for adult head scans depending upon the method used. [112]

The risk of radiation is greater to a fetus, so in pregnant patients, the benefits of the investigation (X-ray) should be balanced with the potential hazards to the fetus. [113] [114] In the US, there are an estimated 62 million CT scans performed annually, including more than 4 million on children. [107] Avoiding unnecessary X-rays (especially CT scans) reduces radiation dose and any associated cancer risk. [115]

Medical X-rays are a significant source of human-made radiation exposure. In 1987, they accounted for 58% of exposure from human-made sources in the United States. Since human-made sources accounted for only 18% of the total radiation exposure, most of which came from natural sources (82%), medical X-rays only accounted for 10% of total American radiation exposure medical procedures as a whole (including nuclear medicine) accounted for 14% of total radiation exposure. By 2006, however, medical procedures in the United States were contributing much more ionizing radiation than was the case in the early 1980s. In 2006, medical exposure constituted nearly half of the total radiation exposure of the U.S. population from all sources. The increase is traceable to the growth in the use of medical imaging procedures, in particular computed tomography (CT), and to the growth in the use of nuclear medicine. [93] [116]

Dosage due to dental X-rays varies significantly depending on the procedure and the technology (film or digital). Depending on the procedure and the technology, a single dental X-ray of a human results in an exposure of 0.5 to 4 mrem. A full mouth series of X-rays may result in an exposure of up to 6 (digital) to 18 (film) mrem, for a yearly average of up to 40 mrem. [117] [118] [119] [120] [121] [122] [123]

Financial incentives have been shown to have a significant impact on X-ray use with doctors who are paid a separate fee for each X-ray providing more X-rays. [124]

Early photon tomography or EPT [125] (as of 2015) along with other techniques [126] are being researched as potential alternatives to X-rays for imaging applications.

Other notable uses of X-rays include:

    in which the pattern produced by the diffraction of X-rays through the closely spaced lattice of atoms in a crystal is recorded and then analysed to reveal the nature of that lattice. A related technique, fiber diffraction, was used by Rosalind Franklin to discover the double helical structure of DNA. [127] , which is an observational branch of astronomy, which deals with the study of X-ray emission from celestial objects. analysis, which uses electromagnetic radiation in the soft X-ray band to produce images of very small objects. , a technique in which X-rays are generated within a specimen and detected. The outgoing energy of the X-ray can be used to identify the composition of the sample. uses X-rays for inspection of industrial parts, particularly welds. , most often x-rays of paintings to reveal underdrawing, pentimenti alterations in the course of painting or by later restorers, and sometimes previous paintings on the support. Many pigments such as lead white show well in radiographs.
  • X-ray spectromicroscopy has been used to analyse the reactions of pigments in paintings. For example, in analysing colour degradation in the paintings of van Gogh. [128]
  • Authentication and quality control of packaged items. (computed tomography), a process that uses X-ray equipment to produce three-dimensional representations of components both externally and internally. This is accomplished through computer processing of projection images of the scanned object in many directions. luggage scanners use X-rays for inspecting the interior of luggage for security threats before loading on aircraft. truck scanners and domestic police departments use X-rays for inspecting the interior of trucks.
  • X-ray art and fine art photography, artistic use of X-rays, for example the works by Stane Jagodič
  • X-ray hair removal, a method popular in the 1920s but now banned by the FDA. [130] were popularized in the 1920s, banned in the US in the 1960s, in the UK in the 1970s, and later in continental Europe. is used to track movement of bones based on the implantation of markers is a chemical analysis technique relying on the photoelectric effect, usually employed in surface science. is the use of high energy X-rays generated from a fission explosion (an A-bomb) to compress nuclear fuel to the point of fusion ignition (an H-bomb).

While generally considered invisible to the human eye, in special circumstances X-rays can be visible. Brandes, in an experiment a short time after Röntgen's landmark 1895 paper, reported after dark adaptation and placing his eye close to an X-ray tube, seeing a faint "blue-gray" glow which seemed to originate within the eye itself. [131] Upon hearing this, Röntgen reviewed his record books and found he too had seen the effect. When placing an X-ray tube on the opposite side of a wooden door Röntgen had noted the same blue glow, seeming to emanate from the eye itself, but thought his observations to be spurious because he only saw the effect when he used one type of tube. Later he realized that the tube which had created the effect was the only one powerful enough to make the glow plainly visible and the experiment was thereafter readily repeatable. The knowledge that X-rays are actually faintly visible to the dark-adapted naked eye has largely been forgotten today this is probably due to the desire not to repeat what would now be seen as a recklessly dangerous and potentially harmful experiment with ionizing radiation. It is not known what exact mechanism in the eye produces the visibility: it could be due to conventional detection (excitation of rhodopsin molecules in the retina), direct excitation of retinal nerve cells, or secondary detection via, for instance, X-ray induction of phosphorescence in the eyeball with conventional retinal detection of the secondarily produced visible light.

Though X-rays are otherwise invisible, it is possible to see the ionization of the air molecules if the intensity of the X-ray beam is high enough. The beamline from the wiggler at the ID11 at the European Synchrotron Radiation Facility is one example of such high intensity. [132]

The measure of X-rays ionizing ability is called the exposure:

  • The coulomb per kilogram (C/kg) is the SI unit of ionizing radiation exposure, and it is the amount of radiation required to create one coulomb of charge of each polarity in one kilogram of matter.
  • The roentgen (R) is an obsolete traditional unit of exposure, which represented the amount of radiation required to create one electrostatic unit of charge of each polarity in one cubic centimeter of dry air. 1 roentgen = 2.58 × 10 −4 C/kg .

However, the effect of ionizing radiation on matter (especially living tissue) is more closely related to the amount of energy deposited into them rather than the charge generated. This measure of energy absorbed is called the absorbed dose:

  • The gray (Gy), which has units of (joules/kilogram), is the SI unit of absorbed dose, and it is the amount of radiation required to deposit one joule of energy in one kilogram of any kind of matter.
  • The rad is the (obsolete) corresponding traditional unit, equal to 10 millijoules of energy deposited per kilogram. 100 rad = 1 gray.

The equivalent dose is the measure of the biological effect of radiation on human tissue. For X-rays it is equal to the absorbed dose.


In the early days, while American workers were busily exploring and reporting the beneficial use of X-rays, less welcome news was beginning to trickle in from many parts of the USA. The rays, it was discovered, produced undesirable changes in exposed tissues. In the 116th anniversary year of the discovery of X-rays, when Roentgen and others were glorified for their discovery and use of X-rays, this article throws light on some of the early victims and martyrs. Given the ambiguity of universal guidelines in obtaining a cone beam CT (CBCT) scan and the undue use of panoramic and full-mouth periapicals at tertiary care centres, oral radiologists may end up making unnecessary examinations, which can result in undue radiation exposure. This highlights the need to look back through history.

Historical perspective

It was barely 14 days after the announcement of the discovery of Roentgen rays that Friedrich Otto Walkhoff took the first dental radiograph. He took an ordinary photographic glass plate, wrapped it in a rubber dam, held it in his mouth between his teeth and tongue and then lay on the floor for a 25 min exposure. Walkhoff said that those 25 min of exposure were a torture to him. 1 However, the exact nature of this torture has not been described. Later, in 1896, Walkhoff succeeded in making extra-oral pictures with an exposure time of 30 min. He noticed a loss of hair on the side of the head of some of the patients he irradiated, 2 but as there was no mention of blisters on the skin it is assumed that the absorbed dose was less than 300 rads.

In 1896, Otto Walkhoff and Fritz Giesel established the first dental roentgenological laboratory in the world. For many years the laboratory provided practitioners with images of the jaw and head. Fritz Giesel later died in 1927 of metastatic carcinoma caused by heavy radiation exposure to his hands. 3

In February 1896 a child who had been accidentally shot in the head was brought to the laboratory at Vanderbilt University (Tennessee, USA). Before attempting to locate the bullet in the child, Professor Daniel and Dr Dudley decided to undertake an experiment. Dr Dudley, with his characteristic devotion to science, lent himself to this experiment. A plate holder containing the sensitive plate was tied to one side of Dudley's head and the tube attached to the opposite side of the head. The tube was placed 0.5 inches away from Dudley's hair and activated for 1 h. After 21 days all the hair fell out from the space under discharge, which was approximately 2 inches in diameter. 4

On 12 August 1896, Electrical Review reported that Dr HD Hawks, a graduate of the 1896 class of Columbia College, gave a demonstration with a powerful X-ray unit in the vicinity of New York. 5 After 4 days, he was compelled to stop work. He noticed a drying of the skin, which he ignored. The hand began to swell and gave the appearance of a deep skin burn. After 2 weeks the skin came off the hand, the knuckles become very sore, fingernail growth stopped and the hair on the skin exposed to X-rays fell out. His eyes were bloodshot and his vision became considerably impaired. His chest was also burnt. Mr Hawks' physician treated this as a case of dermatitis. Hawks tried protecting his hands with petroleum jelly, then gloves and finally by covering it with tin foil. Within 6 weeks Hawks was partially recovered and was making light of his injuries. Electrical Review concluded by asking to hear from any of its readers who had had similar experiences.

GA Frei of Frei and Co., a Boston manufacturer of X-ray tubes, replied the next day: Mr K, an employee of the company, complained of peculiar itching and burning in his left hand and thought it was due to poisoning with chemicals. Mr K used to regularly attend to testing of tubes during and after the exhausting process at the rooms. The same phenomenon also appeared on Frei's hand. The letter concluded by stating that further developments would be carefully monitored. 5

A distressing case was reported in September 1896. William Levy had been shot in the head by an escaping bank robber 10 years previously. The bullet entered his skull just above the left ear and presumably proceeded towards the back of the head. Having heard about X-rays, he decided he wanted the bullet localized and extracted. Levy approached Professor Jones of the Physical Laboratory, University of Minnesota. Professor Jones, who was familiar with Daniel and Dudley's experiments, warned Levy against the exposure, but Levy was undeterred and an exposure was made on 8 July 1896. Exposures were made with the tube over his forehead, in front of his open mouth and behind his right ear. Levy sat through the exposures from 8 o'clock in the morning until 10 o'clock at night. Within 24 h his entire head was blistered, within a few days his head was an angry sore and his lips were badly swollen, cracked and bleeding. His right ear had doubled in size and the hair on his right side had entirely fallen out. Professor Jones concluded that the one feature that was satisfactory to the patient was that a good picture of the bullet was obtained, showing it to be about an inch beneath the skull under the occipital protuberance. 6

Dr Stickney reported a case in December 1896 of a woman who complained of abdominal pain. A radiograph of the patient, Mrs Q, was taken in the abdominal region. The focus of X-rays was over the liver. 3 exposures were made of 20 min, 30 min and 35 min. Two days later she developed burns over the region. The condition worsened until the surface sloughed. 7

The above cases of Hawks, Dudley and Stickney all reported skin blisters and it could therefore be assumed that the absorbed dose of the victims was at least 1500 rads. Serious damage from the rays was also reported from the Edison Laboratory. Elihu Thomson of General Electric cited two Edison cases in a letter dated 1 December 1896 to Dr EA Codman of Boston. Thomson referred to these cases as serious because they took place over the hands and arms of the victims and they had to stop working with X-rays altogether. The story goes that one of them was told by his physician that if he continued to work with X-rays it would be necessary to amputate his hands. The worker threatened with amputation was probably Clarence Dally, Thomson Edison's glassblower.

Clarence Dally was likely to have had an absorbed dose of approximately 3000 rads to necessitate amputation. It needs to be noted that not everyone had the same experience. Dr Williams reported in 1897 that in approximately 250 patients, who he examined with X-rays, he had not seen any harmful effects. 8

Professor Stine of Armour Institute of Technology reported that a patient who was exposed for 2 h for 2 successive days with the plate a few inches from the skin developed itching and irritation. A few days later the skin swelled and became inflamed, and the area immediately surrounding the exposure was tanned and dry. In time the skin peeled off and resembled bad sunburn. Professor Stine, however, concluded that the effect was due to ultraviolet rays and not X-rays. 9

Dr EA Codman, in 1902, conscientiously reviewed all papers on X-ray injuries. Of the 88 X-ray injuries published, 55 had occurred in 1896, 12 in 1897, 6 in 1898, 9 in 1899, 3 in 1900 and 1 in 1901. The decline could be due to the fact that X-ray injuries were no longer in the news and therefore went unreported unless they exhibited unusual features. 10

Clarence Dally (1865�) is thought to be the first to die as result of X-ray exposure. He died of metastatic carcinoma at only 39 years old.

The next death to be reported was that of Elizabeth F Ascheim (1859�) of San Francisco. Deaths reported thereafter included those of Wolfram C Fuchs (1865�), who opened the X-ray laboratory in Chicago in 1896 and made the first X-ray film of a brain tumour in 1899, and Dr William Carl Egelhoff (1872�). Among the victims who suffered the most was Dr Walter James Dodd (1869�). He was operated on 32 times and died of metastatic carcinoma of the lung on 18 December 1916. 11

The deaths of tube manufacturers have included Rome Vernon Wagner (1869�), his brother Thurman Lester Wagner (1876�), Burton Eugene Baker (1871�), Henry Green (1860�), John Bawer (unknown year of birth�) and Robert H Machlett (1872�). 12

The case of C. Edmund Kells is well known. Kells developed a radiogenic neoplasm in 1922 and endured increasing discomfort and excruciating pain. Kells did not listen to the warning given by William Rollins regarding radiation hazards. He had undergone 42 operations and several amputations (some have reported 100). On 7 May 1928 Kells triggered a 0.32 calibre bullet into his brain. 3

Dr Perry Brown, an eminent Boston radiologist, published his collection of biological essays 𠇊merican martyrs to science through Roentgen rays” in 1936. He reported the deaths of Mihran Kasabian of Philadelphia (1870�), Eugene Caldwell of New York (1870�), Herbert Robert of St Louis (1852�), Fredrick H Baetjer of Baltimore (1874�) and a number of others whose lives deserve to be remembered. However, his own story was missing Dr Brown died of X-ray induced cancer in 1950. 11

Dr Cannon began using X-rays in 1896 when he was a medical student. In 1931 he developed itching of skin and fresh red papular lesions on his back, chest, thighs, knees and elbows. Dr Cannon suggested that repeated biopsies be made so that it would provide more information on this poorly understood condition. He developed several lesions all over the body, many of which continuously recurred.

In April 1944, a recurrent basal cell carcinoma of the nostril was excised. In 1945 he passed the 14 th anniversary of the onset of mycosis fungoidosis — an amazingly long survival. On 1 October 1945 he died of recurrent pulmonary infection. 6

It would be generous to accept Dr Grubbe's account precisely as he wrote it, for he truly was an X-ray martyr. Dr Grubbe suffered at least 83 surgical operations to relieve his discomfort and to stop the progress of gangrene from his left hand to his arm, elbow and finally shoulder. Grubbe's face was grossly disfigured with cancer. He became sterile. His marriage was left childless, a misfortune he attributed to the X-rays. He lived in agony for many years, yet he continued to work with the rays.

In his autobiography he maintained “my courage is my work. I treat patients who suffer more or are encumbered more than me, and so I go on. By helping others I help myself”. He went on to predict “I will die from the effects of early uncontrolled exposures to X-rays. And like many of the early pioneers, I too, will die a victim of natural science, a martyr to the X-rays.”

Dr Grubbe, in the chapter “The effect of the X-rays on author’s body”, concluded on a noble note: “I have lived large enough to see the child that I fathered develop into a sturdy, mature and worthwhile product and I hope as I approach the evening of my day, to see even more uses of X-ray energy in the alleviation of the ills of mankind.” Dr. Grubbe died of metastatic cancer on 26 March 1960. 13 It could be hypothesized that Kells and Grubbe had a consistent absorbed dose of 3000 rads.

November 28, 1895: Granddaddy of All American Auto Races

A Brief History On November 28, 1895, the first American auto race took place, the Chicago Times-Herald Race, a 54 mile event with a grand prize of $5000. (If that prize sounds lame, remember that this is worth over $140,000 in today’s money.) Digging Deeper As the automobile was a new-fangled invention at the time, a proper name for the motorized conveyance had not yet been agreed upon and the Times-Herald called their event a “Moto-cycle Race.” Originally meant to be a race from Chicago to Milwaukee, the roads of the day were not smooth enough for those primitive cars&hellip


This paper is intended to celebrate the 120th anniversary of the discovery of X-rays. X-rays (Roentgen-rays) were discovered on the 8th ofNovember, 1895 by the German physicist Wilhelm Conrad Roentgen. Fifty days after the discovery of X-ray, on December 28, 1895. Wilhelm Conrad Roentgen published a paper about the discovery of X-rays - "On a new kind of rays" (Wilhelm Conrad Roentgen: Ober eine neue Art von Strahlen. In: Sitzungsberichte der Wurzburger Physik.-Medic.- Gesellschaft. 1895.). Therefore, the date of 28th ofDecember, 1895 was taken as the date of X-rays discovery. This paper describes the work of Wilhelm Conrad Roentgen, Nikola Tesla, Mihajlo Pupin and Maria Sklodowska-Curie about the nature of X-rays . The fantastic four - Wilhelm Conrad Roentgen, NikolaTesla, Mihajlo ldvorski Pupin and Maria Sklodowska-Curie set the foundation of radiology with their discovery and study of X-rays. Five years after the discovery of X-rays, in 1900, Dr Avram Vinaver had the first X-ray machine installed in abac, in Serbia at the time when many developed countries did not have an X-ray machine and thus set the foundation of radiology in Serbia.

1895: Wilhelm Röntgen Discovers X-rays

On this day, in the late afternoon hours, German physicist Wilhelm Roentgen experimented with a variety of electronic devices, including some of Tesla’s, by putting them under electrical discharge and observing the rays they produce. In one of the experiments in a darkened room, he noticed a glimmer of barium platinocyanide. He concluded that this shimmering was caused by some as yet unknown rays.

He called them X-rays, where X was a designation for something unknown. When he placed various items in the range of these rays, he saw a picture of his skeleton on a barium platinocyanide screen. After that, he continued his research in secret because he was afraid that he might be ridiculed if his observations do not prove to be true. After two weeks, he made a picture of his wife’s hand, on which bones and rings can be seen. The rays were named Röntgen rays after him, although he always preferred the term X-rays.

Watch the video: Wilhelm Roentgen Biography: How u0026 Why X-rays were Discovered (January 2022).