X-ray Vision: Roentgen and the Dawn of Radiology

Saurabh Jha, MS, MBBS, MRCS; Jeanne Elkin


February 12, 2021

On the night of November 8, 1895, German physicist Wilhelm Conrad Roentgen finished his supper and went to his laboratory to conduct some routine experiments. Roentgen had no way of knowing that, quite by accident, he would soon make a discovery bordering on the fantastical, rendering a once-hidden world suddenly visible.

Roentgen was studying cathode rays, invisible forces created by electricity, later determined to be electrons. Using a pear-shaped Crookes vacuum tube, Roentgen would fire the cathode rays from one end using an electric jolt, where they would exit the other end through a small hole and generate colorful light upon striking fluorescent material placed nearby.

On this particular evening, Roentgen closed the curtains, wanting his pupils maximally dilated to spot tiny flickers of light. When he turned the voltage on the Crookes tube, he noticed that a paper soaked in barium platinocyanide on a bench 9 feet away flickered. He was understandably perplexed. Cathode rays traveled only a few centimeters. Also, he had covered the tube with heavy cardboard to stop light. Why, then, did the distant paper glow?

Roentgen's initial discovery may have been accidental, but he followed it through using a rigidly disciplined scientific method. Only reproducibility of results could convince him that his eyes weren't being deceived. He knew the glow wasn't an artifact because it occurred only when the Crookes tube was on. Had he underestimated the distance that cathode rays traveled? The paper still glowed when placed farther away from the tube. Not even a deck of cards stopped the glow.

Like his contemporaries, Roentgen didn't know the precise nature of cathode rays. He didn't think they were responsible for the distant glow. But perhaps they were somehow responsible for creating a new kind of ray, similar to light but which could penetrate solid material. He decided to call his discovery "x-rays" — the "x" denoting that their nature was unknown.

The Birth of Modern Radiology

Increasingly curious, Roentgen spent several weeks experimenting with x-rays. He studied the stopping properties of various metals by observing their shadows. Then, on one occasion, when he held a piece of lead in his hand, he saw shadows of his bones.

It was this discovery that led to the birth of modern radiology.

On December 22, 1895, Roentgen placed his wife's left hand in the path of the x-rays. After a 15-minute exposure, an iconic photograph emerged. Only the bones of his wife's hand and her wedding ring cast a shadow.

The x-ray had provided a view of the human body that had previously only been possible when inspecting the bones of the deceased. Seeing the image of the bones stripped of flesh in a living subject, obtained noninvasively, must have seemed almost supernatural at the time.

Roentgen published his findings in a paper titled "On a New Kind of Rays" in the Proceedings of the Wurzburg Physical Medical Society, a relatively obscure publication with a rapid publishing time.

Roentgen's publication probably would not have been the first mention of x-rays had history gone slightly differently.

A few years earlier, Arthur Godspeed, a physicist at the University of Pennsylvania who also experimented with cathode rays, discovered that some photos he had developed displayed disk-shaped shadows, which, unbeknownst to him, were cast by coins in the path of x-rays. William Crookes, the inventor of the Crookes tube, returned several photographic plates to their manufacturers because they were fogged. After Roentgen's discovery, he realized that the "damage" he had reported was actually x-rays' signature.

If taking notice of x-rays had eluded Roentgen's peers, his discovery would not have the same effect on the press of the era.

On January 5, 1896, the Vienna Presse, an Austrian newspaper, published Roentgen's discovery. Even during a time without social media, with communication limited to telegraph-shortened distances, news of his discovery became a viral phenomenon. Within 10 days, the London Standard and The New York Times ran the story. The press instantly recognized the medical importance of x-rays, marveling at how they could photograph broken bones and bullets in human bodies.

This is not to say that Roentgen's discovery was universally embraced. X-rays quickly became known for their nefarious potential, considered antithetical to Victorian sensibilities. An editorial in the London-based Pall Mall Gazette in March 1896 expressed concern with the "Roentgen Rays" and, cautioning readers of the "revolting indecency" of being able to see people's bones with the naked eye, asked that legislature restrict x-ray vision.

Much of radiographic practice today can be traced to the research that followed in the months after Roentgen's publication some 125 years ago.

The first medical x-ray in the United States was of a Colles fracture in a boy who injured his wrist, taken by Dartmouth astronomer Edwin Frost in February 1896, on behalf of his physician brother. In the same month, John Cox from McGill University in Canada localized a bullet in the leg of a patient that had eluded the surgeons. By the end of the year, x-rays joined the battlefield in the British expedition of the Nile, helping surgeons deal with wartime injuries.

Disease Can Now Be Seen and Heard

Before Roentgen, disease was inferred by sound, percussion, and auscultation. X-rays ensured that disease would now be seen as well as heard. The Frankfurter Zeitung called x-rays "an epoch-making result of research in exact science."

The first Nobel Prize in Physics was awarded to Roentgen in 1901 for his medical breakthrough.

Roentgen contributed heavily to medicine's firmly becoming an applied science by melding it with physics. Later, x-rays would illuminate the structure of DNA through the related process of crystallography.

Notably unassuming, Roentgen dodged fame and declined fortune. He refused to copyright his discovery. He donated his Nobel Prize money to academia.

When asked by a journalist what he thought when he saw the glow from the distant paper, Roentgen replied, curtly, "I did not think; I investigated." And in this deceptively simple act, he propelled both medicine and science into the future.

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