5. I’m Looking Through You: The Discovery of X-Rays
Mysteries, secrets, and revelations: four true stories...
Case 1: Up until two days ago, the six-week-old boy had been healthy, active, and alert, but when his left thigh suddenly swelled up, his worried mother brought him to the emergency room. Responding to routine questions, she told doctors that the child had not been injured by rough play or an accident. What could explain the swollen leg—a tumor, blood clot, or perhaps infection? The mystery was solved with a single X-ray: Emerging from a shadowy black background, the ghostly white glow revealed a left thigh bone that had been cleanly snapped into two pieces. But an even darker secret was revealed by subsequent X-rays: The baby was also healing from fractures in his right forearm, right leg, and skull. Diagnosis in hand, treatment was clear. The boy was fitted with an orthopedic harness and placed—along with his two siblings—in a foster home to prevent further abuse.
Case 2: Jin Guangying, a 77-year-old grandmother in China, had been suffering from headaches for decades, some so severe that she would pound her head with her fist and babble incoherently. When her family finally borrowed enough money to take her to a doctor, X-rays of Guangying’s head were unremarkable—a dull, grayish white landscape surrounded by a trace outline of her brain and facial bones. Except for one startling feature: There, nestled comfortably near the center of her brain, was the blazing white glow of a one-inch long bullet. Doctors removed the bullet in a four-hour operation and soon learned the full story. In 1943, during World War II, 13-year-old Guangying had been taking food to her father when she was shot by the invading Japanese army. She somehow survived the wound, and it was forgotten for the next 60 years—until a simple X-ray revealed both the mystery and the secret of her headaches.
Case 3: When the 62-year-old man arrived at the ER with stomach pain and an inability to eat or move his bowels, doctors were warned that he had a history of mental illness. But that hardly prepared them for what an X-ray of his chest and abdomen soon revealed. As doctors glanced over the billowy clouds of organs and ladder-like shadows of vertebrae, their gaze quickly fell on the enormous, bright-white sack in his lower abdomen. The shape did not correspond with any known anatomic feature—unless, of course, one’s stomach happens to be packed with 350 coins and assorted necklaces. As doctors learned during surgery, the 12 pounds of metal was sufficient to sink his stomach to its new location between the hips—explaining both the mystery of the patient’s symptoms and the secret of a mental illness more severe than anyone had realized.
Case 4: Luo Cuifen, a 31-year-old woman from a rural province in China, suffered for years from depression, anxiety, and an inability to do physical labor. But it was not until she noticed blood in her urine that she went to the hospital for tests. What costly marvels of high-tech medicine would solve the mystery of her symptoms? Nothing more than a simple X-ray. There, glowing brightly among the shadows of her spine and pelvis, were the sharp outlines of 23 one-inch-long sewing needles lodged in her lungs, liver, bladder, and kidneys. As doctors prepared to operate, they revealed the dark secret behind this mystery. The needles were likely jabbed into Cuifen by her now-deceased grandparents when she was an infant—a failed attempt at infanticide in an area of rural China where baby girls are often killed because tradition does not allow them, unlike boys, to carry on the family name or support their parents in old age.
Eerie and invasive: an invisible form of light that shocked and changed the world
Although these true stories—culled from recent medical journals and news reports—are unusual, they illustrate why X-rays continue to fascinate us 100 years after their discovery. In a glance, they can solve the deepest mysteries of pain and suffering, reveal unseen injuries and disease, and illuminate strategies for treatment. But as these stories also demonstrate, X-rays sometimes uncover even deeper secrets of human behavior—revelations of child abuse, wartime atrocities, mental illness, and the brutality of cultural shame. Today, we marvel—and sometimes fear—the humble X-ray for its ability to unveil truths that can, in a matter of seconds, change the course of a person’s life.
As the world soon realized after their discovery in 1895, X-rays are a strange breed of science and magic. Looking at X-rays of our own bodies, we are confronted with an unsettling paradox: both the hard evidence of our sturdy inner workings and a skeletal reminder of our eventual demise and decomposition. Yet there is also magic in those images, the wonder that a trained eye can translate cloudy blurs and shadows into specific diseases and treatable injuries. This is a nice trick that, over the course of a century, has saved or improved millions of lives.
The mystique of X-rays is also hidden within its very name—the inscrutable “X” that suggests a power too unworldly to be pinned down by a “real” name. Indeed, X-rays are eerie because, in revealing our inner secrets, they themselves are secretive—invisible, unheard, and unfelt as they trespass our bodies at the speed of light.
* * *
Unlike most breakthroughs in medicine, X-rays were not discovered after a series of milestones in biology and health. Rather, their discovery was the result of decades of pioneering work in electricity and magnetism. Therefore, in this case we begin with the moment of discovery and then track the subsequent milestones that transformed X-rays into a breakthrough in medicine.
And those milestones are truly remarkable—from the shockwaves of amazement that shook the world after their discovery, to the countless applications that soon proved their unprecedented value in diagnostic medicine; from the discovery that they could treat cancer and other diseases, to the tragic realization that they could have dangerous, even deadly, effects. At the same time, X-rays helped trigger a paradigm shift in our understanding of reality itself. Indeed, they arrived at a time when scientists were grappling with the nature of the physical world—the structure of the atom and quantum physics—and for years no one knew exactly what X-rays were or how they could even exist. As Wilhelm Roentgen, the man who won the 1901 Nobel Prize in physics for discovering X-rays, once told an audience: Even after witnessing the rays pass through various objects, including his own hand, “I still believed I was the victim of deception.”
But Roentgen soon became a believer, as did the rest of the world, once his first X-ray image was released to the public. That shadowy image—a photograph of his wife’s hand clearly revealing bones, tissues, and the wedding ring on her finger—was unlike anything seen before. Almost immediately it set off a global firestorm of excitement, fear, and reckless speculation. As Roentgen later recalled, once the world saw that first X-ray, the secret was out and: “All hell broke loose.”
Milestone #1 How one man working alone at night discovered a remarkable “new kind of ray”
One Friday evening in November, 1895, a respected physicist in Germany began fooling around with something he had no business doing. Working alone in his laboratory, Wilhelm Roentgen began shooting electricity through a sealed, pear-shaped glass tube, causing its sides to emit an eerie fluorescent glow. It’s not that Roentgen wasn’t qualified: The 50-year-old Director of the Physical Institute at the University of Wurzburg had published more than 40 papers on various topics in physics. But he had shown no interest in such “electrical discharge” experiments until recently, when his curiosity had been aroused by an odd finding reported by another physicist.
For more than 30 years, physicists knew that firing high-voltage electrical discharges through a vacuum tube could cause the negative terminal in the tube—the cathode—to emit invisible “rays” that caused the tube to glow. They called these rays, logically enough, “cathode rays,” though no one knew exactly what they were. Today, we know them to be electrons, the charged particles that orbit atoms and whose flow comprises electricity. But at the time, cathode rays were a mystery, and when in the early 1890s physicist Philipp Lenard discovered a new property—that cathode rays could actually pass through a small window of aluminum in the glass tube and travel a few inches outside—many scientists, including Roentgen, were intrigued.
On that historic evening, November 8, 1895, Roentgen was simply trying to repeat Lenard’s experiment when two events—the products of curiosity and coincidence—led to a breakthrough discovery. First, he decided to cover the glass vacuum tube (called a Crookes tube) with light-proof cardboard and darken the room so he could better see the luminescent glow when the rays passed through the aluminum and outside the tube. Second, he happened to leave a small light-sensitive screen lying several feet away on a table.
Roentgen turned off the lights, fired up the Crookes tube, and watched for the faint glow to appear an inch or two outside the tube. Instead, something completely unexpected happened: An eerie yellow-green glow appeared in the dark several feet away, nowhere near the Crookes tube. Roentgen scratched his head, checked his equipment, and repeated the discharges. The same strange glow appeared across the room. He turned on the light and immediately saw where the glow was coming from: It was the light-sensitive screen that happened to be lying nearby. Roentgen moved the screen around, fired up the Crookes tube, and checked and rechecked the glow until he could no longer doubt his eyes. Some kind of “rays” were coming out of the Crookes tube, striking the screen, and causing it to glow. What’s more, they could not be cathode rays because to reach the screen, they had to travel at least six feet—25 times farther than the few inches that cathode rays were known to travel.
As Roentgen studied the rays late into that November evening and with feverish intensity over the next six weeks, he soon realized that the distance these invisible rays traveled was the least of their remarkable properties. For one thing, when they were beamed at the light-sensitive screen, the screen glowed even when the coated side was facing away from the rays. That meant the rays could pass through the back of the screen. Could they pass through other solid objects as well? In subsequent experiments, Roentgen found that the rays could easily pass through two packs of cards, blocks of wood, and even a 1,000-page book, before striking the screen and causing it to glow. On the other hand, dense materials, such as lead, blocked or partially blocked the rays, casting a shadow on the screen.
It was during these experiments that Roentgen made his final, astonishing discovery. At one point, while shooting the rays through an object to study its ability to stop the rays, he was startled to see cast upon the screen not only the shadow of his fingers holding the object, but within that shadow, the additional shapes of...his own bones. Roentgen had arrived at his milestone discovery. While he knew that the rays were absorbed in varying amounts based on the density of an object, this was a new twist: If the object itself consisted of different densities—such as the human body, with its bones, muscle, and fat—any rays passing through it would cast shadows of varying brightness on the screen, thus revealing those inner parts.
When Roentgen cast that first shadow of his own bones upon the screen, he simultaneously achieved two milestones: he had created the world’s first X-ray and the first fluoroscope. But it was not until several weeks later, on December 22, 1895, that he created the world’s first permanent X-ray image when he beamed the newly discovered rays through his wife’s hand and onto a photographic plate.
Following his initial discovery, Roentgen worked alone and secretly for the next seven weeks. Sometimes sleeping in his laboratory and often skipping meals, he hardly hinted at his discovery to anyone other than perhaps his wife and a close friend or two. To one friend, he remarked with characteristic modesty, “I have discovered something interesting, but I do not know whether or not my observations are correct.” During those weeks, Roentgen methodically explored the properties of these strange new rays, from the various materials they could penetrate, to whether, like other forms of light, they could be deflected by a prism or a magnetic field.
Finally, over the Christmas holidays, Roentgen wrote up his findings in a concise 10-page paper, titled “On a New Kind of Rays.” In this paper, he used the term “X-rays” for the first time and reported—correctly—that the invisible rays were somehow generated when cathode rays struck the walls of the glass tube. On December 28, 1895, Roentgen sent his paper to the Physical-Medical Society of Wurzburg for publication in their Proceedings. A few days later he received reprints of the article, and on New Year’s Day, 1896, he mailed 90 envelopes with copies of the article to physicists throughout Europe. In 12 of the envelopes, he included nine X-ray images that he had created. Most of the images showed the interiors of common objects, such as a compass and a set of weights in a box. But there was one image in particular—the image of his wife’s skeletal hand bearing a ring—that caught the world’s attention.
It took only three days for “All hell to break loose.” At a dinner party on January 4, 1896, one of the recipients of Roentgen’s article and X-ray images happened to show it to a guest from Prague, whose father happened to be the editor of Die Presse, Vienna’s largest daily newspaper. Intrigued, the guest asked to borrow the images, took them home to his father, and the next morning, the story of Roentgen’s discovery appeared on the front page of Die Presse under the headline, “A sensational discovery.” Within days, the story had been reported by newspapers across the world.
Milestone #2 A one-year firestorm and those “naughty, naughty” rays
It is almost impossible—no, it is literally impossible—to overstate the intensity and range of reactions by scientists and the public during 1896, the first year after Roentgen’s discovery. From the moment Roentgen’s shared his findings, even respected colleagues were stunned. One physicist to whom Roentgen sent the original reprint and photographs recalled, “I could not help thinking that I was reading a fairy tale... that one could print the bones of the living hand upon the photographic plate as if by magic...” A physician recalled that shortly after the first news reports came out, a colleague came to up to him at an event and excitedly began describing Roentgen’s “peculiar” experiments. The physician scoffed and starting cracking jokes until the colleague became angry and left. But when the physician later met with a group of other doctors who were discussing the report, he read the article for himself and, “I must say that I was speechless.”
Before long, there were few doubters. As the London Standard reported on January 7, “There is no joke or humbug in the matter. It is a serious discovery by a serious German Professor.” And with acceptance, recognition of the implications quickly followed. On January 7, the Frankfurter Zeitung wrote, “If this discovery fulfills its promise, it constitutes an epoch-making result... destined to have interesting consequences along physical as well as medical lines.” Later in January, The Lancet noted that the discovery “will produce quite a revolution in the present methods of examining the interior of the human body.” And on February 1, the lead article in the British Medical Journal stated that “The photography of hidden structures is a feat sensational enough and likely to stimulate even the uneducated imagination.”
In those first few weeks, many scientists reacted exactly as you might expect: They raced out and bought their own Crookes tubes and equipment—which at the time cost less than $20—to see if they could create their own X-rays. In fact, so many people did this in the first month that on February 12, 1896, the Electrical Engineer wrote, “It is safe to say that there is probably no one possessed of a vacuum tube and induction coil who has not undertaken to repeat Professor Roentgen’s experiments.” One week later, Electrical World reported, “All the Crookes tubes in Philadelphia have been purchased...” Telegraph wires, too, were abuzz with scientists seeking advice. When one physician in Chicago wired inventor Thomas Edison for technical advice, Edison wired back the same day, “THING IS TOO NEW TO GIVE DEFINITE DIRECTIONS. IT WILL REQUIRE TWO OR THREE MORE DAYS EXPERIMENTING...”
As the news spread and became the hot topic of the day, some couldn’t restrain their cynicism with the hullabaloo. In March, the English Pall Mall Gazette noted, “We are sick of the Roentgen rays... It is now said... that you can see other people’s bones with the naked eye... On the revolting indecency of this there is no need to dwell.” And on February 22, 1896, the editor of the Medical News wrote, “It is questionable how much help can be obtained by such crude and blurred shadow pictures...”
But for many scientists, there was little question of the significance of X-rays. On January 23, 1896, Roentgen gave one of his few public lectures on his discovery to a large group that included members of the Physical-Medical Society of Wurzburg, university professors, high-ranking city officials, and students. Roentgen was greeted with a “storm” of applause and interrupted repeatedly during his talk by more applause. Near the end, he summoned famous anatomist Rudolph von Kolliker from the audience and offered to make an X-ray of his hand on the spot. The X-ray was made, and when the image was held up to the room, the audience again burst into applause. Von Kolliker then praised Roentgen and led the crowd in calling three cheers for the professor. When von Kolliker concluded by suggesting the rays be named after Roentgen, the room again thundered with applause.
Perhaps the best evidence for the overwhelming interest in Roentgen’s discovery during that first year is seen in a simple statistic: By the end of 1896, more than 50 books and 1,000 papers about X-rays had been published worldwide.
As for the general public, the response was equally enthusiastic—but far more charged by irrational fears, nervous humor, and shameless profiteering. One of the biggest initial misunderstandings was the belief X-rays were just another form of photography. Many early cartoons made great fun of this misperception, such as joke in the April 27, 1896, issue of Life magazine. A photographer is preparing to take a picture of a woman and asks her if she would like it “with or without.” She answers, “With or without what?” To which he replies, “The bones.”
From such misunderstandings came genuine fears that shady individuals, driven by prurient desires, would take their X-ray “cameras” to the streets and snap revealing photographs of innocent passersby. And so, within weeks of the discovery, one London company thoughtfully advertised the sale of “X-ray-proof underclothing—especially made for the sensitive woman.” In a similar vein of misunderstanding, Edison was undoubtedly puzzled when he received two odd requests in the mail. In one, the libidinous individual had sent a set of opera glasses, asking Edison to “fit them with X-rays.” The other simply requested, “Please send me one pound of X-rays and bill as soon as possible.”
To clear up such misconceptions, Edison and other scientists set up exhibitions to educate the public first-hand about Roentgen’s amazing rays. As it turned out, it was often the scientists who were educated about the public. At one exhibit in London, an attendant reported that two elderly ladies entered the small X-ray room, asked that the door be fastened tightly, and then solemnly requested that he “show them each other’s bones, but not below the waistline.” As the attendant prepared to comply, a brief argument broke out as “Each wished to view the osseous structures of her friend first.” At another point, a young girl asked the attendant if he could take an X-ray of her boyfriend “unbeknown to him, to see if he was quite healthy in his interiors.”
Not surprisingly, X-rays brought out the human penchant for foolish hopes and silly deceptions. Columbia College reported that someone had found that projecting X-rays of a bone upon the brain of a dog caused the dog to immediately become hungry. A New York newspaper claimed the College of Physicians and Surgeons had found that X-rays could be used to project anatomic diagrams directly into the brains of medical students, “making a much more enduring impression than ordinary methods of learning anatomic details.” And a newspaper in Iowa reported that a Columbia college graduate had successfully used X-rays to transform a 13-cent piece of metal into “$153 of gold.”
But to its credit, the public soon recognized that X-rays could be used in equally valuable, but more realistic, ways. A Colorado newspaper reported in late 1896 that X-ray images had been used to settle a malpractice suit against a surgeon who had not properly treated a patient’s broken leg. Interestingly, one judge refused to accept the X-ray evidence “because there is no proof that such a thing is possible. It is like offering the photograph of a ghost.” But another judge later praised the X-ray evidence and that “modern science has made it possible to look beneath the tissues of the human body.”
In the end, perhaps it was a sense of humor that helped society survive that first year following Roentgen’s discovery. A political commentary in a 1896 newspaper joked that the Shah had all of his court officials photographed with Roentgen rays and that “In spite of a one hour’s exposure, no backbone could be detected in any one of them.” In another bit of humor, the Electrical World wrote in March 1896 that a woman, apparently fixated on Roman numerals, “recently asked us something about those wonderful ‘Ten rays.’” And in August, 1896, the Electrical Engineer, mystified by a photographer’s ad claiming he could use X-rays to settle divorce cases, wrote, “We presume he uses the X-ray to discover the skeleton which every closet is said to contain.”
Finally, a poem that appeared in Photography in early 1896 captured the public’s nervous amusement with the new rays. Titled “X-actly So!” the poem concluded,
I’m full of daze
Shock and amaze;
For nowadays
I hear they’ll gaze
Thro’ cloak and gown—and even stays,
These naughty, naughty Roentgen Rays.
Milestone #3 Mapping the unknown country: X-rays revolutionize diagnostic medicine
With all their potential to uncover life-threatening injuries and diseases in virtually any part of the body, it’s ironic that the first medical use of X-rays was so remarkably nondramatic: locating a needle. On January 6, just two days after the discovery was announced, a woman came into Queens’ Hospital in Birmingham, England, complaining of a sore hand. Fortunately, the necessary equipment was available. An X-ray was made and passed on to a surgeon, who used the image to locate and remove the slender invader. Yet the importance of locating stray needles should not be underestimated, given the apparent frequency of such mishaps. One physicist at Manchester University complained that in early 1896, “My laboratory was inundated by medical men bringing patients who were suspected of having needles in various parts of their bodies. During one week, I had to give the better part of three mornings locating a needle in the foot of a ballet dancer.”
But it was not long before physicians began using X-rays for far more serious injuries. In North America, the first use of X-rays for diagnosis and guiding surgery was on February 7, 1896. Several weeks earlier, on Christmas day, a young man named Tolson Cunning had been shot in the leg while playing in a scrimmage. When doctors at Montreal General Hospital couldn’t find the bullet, a 45-minute X-ray revealed the flattened intruder lodged between his tibia and fibula. The image not only helped surgeons remove the bullet, but helped Cunning in a law suit he later filed against the shooter. Fortunately or unfortunately, X-rays soon played a starring role in such emergencies. As The Electrician wryly observed in early 1896, “So long as individuals of the human race continue to inject bullets into one another, it is well to be provided with easy means for inspecting the position of the injected lead, and to that extent aid the skilled operators whose business and joy it is to extract them.”
As X-rays continued to prove their diagnostic value, physicians began demanding that the equipment—often located in a physics laboratory half-way across town—be brought closer to their practices. Thus, as early as April, 1896, the first two X-ray departments in the United States were installed in the New York Post-Graduate Medical School and in the Hahnemann Hospital and Medical College in Chicago. With the opening of the Post-Graduate Medical School facility, Electrical Engineer reported that “The utility of taking X-ray pictures in surgery has been demonstrated so often that the hospital authorities have set aside one of the smaller wards for that purpose. They will equip it with Crookes tubes...and all the other paraphernalia of the new art.”
X-ray equipment was also soon enlisted for service on the battlefield. In May, 1896, the War Office of the British Government ordered two X-ray machines “to be sent up the Nile to help army surgeons locate bullets in soldiers and in determining the extent of bone fracture.” Interestingly, nearly 20 years later, as hospitals were overwhelmed by “terrifying numbers” of wounded soldiers during World War I, Nobel Prize winner Marie Curie helped expand the use of X-rays and save numerous lives. Curie created what became known as the “petite Curie,” a motor vehicle that was equipped with an X-ray machine and powered by the car engine. The vehicle could be driven to the battlefront or short-handed hospitals in and around Paris to help in treating wounded soldiers.
Apart from needles and bullets, X-rays quickly found their way into many other medical applications. One important use was the diagnosis of tuberculosis, a leading cause of death in the late nineteenth and early twentieth centuries. In early 1896, physician Francis Williams—widely considered to be America’s “first radiologist”—was diligently at work at Boston City Hospital testing the fluoroscope for its use in diagnosing chest diseases. In April, Williams wrote a letter about his work to a major medical journal, reporting, “One of the most interesting cases was that of a patient suffering from tuberculosis of the right lung...the difference in the amount of rays which passed through the two sides of the chest was very striking...The diseased lung being darker throughout than the normal lung...” In early 1897, after working with other patients and lung diseases, Williams wrote a classic paper in which he concluded, “By X-ray examinations of the chest we gain assistance in recognizing... tuberculosis, pneumonia, infarction, edema, congestion of the lungs in aneurysm, and in new growths...”
The use of X-rays in dentistry was also first reported early in 1896, in this case by William J. Morton (son of William T. G. Morton, who helped discover ether for anesthesia in 1846). In an April meeting of the New York Odontological Society, Morton announced that because the density of teeth is greater than the surrounding bone, “pictures of the living teeth may be taken by the X-ray, even of each wandering fang or root, however deeply imbedded in its sockets.” Morton also found that X-rays could be used to locate metal fillings, diseases within the tooth, and even “the lost end of a broken drill.” Nevertheless, the regular use of X-rays in dentistry would not come for several decades. With the high voltages, exposed wires, and proximity to the patient’s head, the risk of electrical shock—if not electrocution—was literally too close for comfort. Thus, X-rays in modern dentistry did not arrive until 1933, when improved X-ray equipment and dangerous wiring could be enclosed within a smaller unit.
As the diagnostic uses of X-rays expanded, their value was never better appreciated than in emergency situations. In one such case, just months after the discovery of X-rays, a ten-year-old boy accidentally swallowed a nail. When the doctor could not find anything in the boy’s throat, he concluded the nail had landed in the boy’s stomach and advised the boy to “eat large quantities of mashed potatoes.” The boy was fine for a few days, but was then stricken by attacks of coughing. X-ray equipment was called in and, though the first fluoroscopic examination revealed nothing, doctors tried again during one of the boy’s coughing attacks. Sure enough, there on the screen, rising up and down a distance of two inches with each cough, was the culprit—not in the boy’s digestive tract surrounded by a bolus of mashed potatoes, but lodged in one of his breathing passages. The nail had not been swallowed, but inhaled. With the nail located, the physician who reported this case concluded, “Now the surgeon has the last word.”
And finally, sometimes X-rays proved to be as valuable in diagnosing conditions of the mind as those of the body. In March, 1896, the Union Medical reported that a young woman had requested that her doctor operate on her arm for a pain that she knew was caused by some kind of bone disease. The doctor, who had diagnosed her pain as due to a slight trauma, was proven correct by an X-ray. And thus, “The patient left, entirely cured.”
Regardless of how they were put to use, it was soon clear that X-rays would—in fact, must—change the practice of medicine forever. On March 6, barely three months after the discovery was announced, Professor Henry Cattell of the University of Pennsylvania wrote in Science that, “It is even now questionable whether a surgeon would be morally justified in performing certain operations without first having seen pictured by these rays the field of his work—a map, as it were, of the unknown country he is to explore.”
Milestone #4 From hairy birthmarks to deadly cancer: a new form of treatment
“Herr Director, the hair has come out!”
—Leopold Freund, 1896
While these words hardly sound like a promising introduction to a revolutionary medical advance, when they were shouted out by Vienna X-ray specialist Leopold Freund in November, 1896, as he burst into the room of the director of the Royal Research Institute, they marked the first successful use of X-rays as a form of treatment. Yanked by the hand behind Freund was the lucky patient, a small girl who was disfigured by a “tremendous” hairy pigmented birthmark that covered most of her back. Freund had decided to investigate whether X-rays could help her after reading in a newspaper that excessive X-ray exposure could cause hair loss. And indeed, after treating the upper part of the girl’s birthmark to X-rays—two hours every day for ten days—the resulting circular bald spot was clear evidence of the therapeutic potential of X-rays.
As Freund and others were beginning to realize, the beneficial effects of X-rays were closely linked their harmful effects. Given the crude equipment and long exposure times being used at the time, the occurrence of harmful effects—including severe burns to the skin and hair loss—hardly seem surprising to us today. Yet it took a milestone insight for early pioneers to investigate such effects as a possible treatment. Interestingly, one of the first people to suggest the treatment potential of X-rays was Joseph Lister, the physician who played a role in the discovery of germ theory. In an address to the Association for the Advancement of Science in September, 1896, Lister noted that the “aggravated sun burning” seen with long exposure to X-rays “suggests the idea that the transmission of the rays through the human body may not be altogether a matter of indifference to internal organs, but may by long continued action produce... injurious irritation or salutary stimulation.”
In fact, X-rays were soon found to have therapeutic benefits in many skin diseases, including an ability to shrink and dry up the open sores seen in some cancers. What’s more, some physicians found that X-rays were particularly good at suppressing pain and inflammation in cancer patients. For example, after using X-rays to treat one patient with oral cancer and another with stomach cancer, French physician Victor Despeignes concluded that “the Roentgen rays have a distinct anesthetic effect, and [provide] a general improvement in the condition of the patient.” Similarly, Francis Williams observed that X-rays relieved pain in a breast cancer patient, and that the pain quickly returned when he had to stop treatment for 12 days due to equipment failure.
Although Despeignes also reported that the rays had “little influence” on the growth of cancer, more promising results were seen after X-ray tube technology made a milestone leap in 1913 with the development of the Coolidge tube (discussed later in this chapter). In fact, researchers were eventually surprised to see that higher X-ray energies could kill more cancer cells, while being less damaging to normal cells. From this finding came the rationale for the modern treatment of cancer with X-rays: Because cancer cells grow more rapidly than normal cells, they are more susceptible to destruction by X-rays and less capable of regeneration than slower-growing normal cells.
Of course, not everyone limited their efforts to the treatment of serious diseases. In July 1896, the British Journal of Photography reported that Frenchman M. Gaudoin, having read that X-rays could cause hair to fall out, made a brief foray into the depilatory business. Gaudoin reportedly hoped to help the “considerable proportion of his country-women endowed with soft silky moustaches, which are by no means appreciated by marriageable young girls and even married ladies.” But though customers “flocked” to his business, the treatment failed to work. He was thus forced to “appease their infuriated graces” by returning their money and then “hurriedly retired from the business.”
Milestone #5 A darker side is exposed: the deadly dangers of X-rays
One summer day in 1896, William Levy, intrigued by reports of the miracle new rays, decided it was high time to look into getting that pesky bullet removed from his brain. Shot just above his left ear ten years earlier by an escaping bank defaulter, Levy survived the attack and now approached a professor at the University of Minnesota to see if X-rays could help doctors locate and remove the bullet. Levy was duly warned that the long exposures needed to penetrate his skull might cause some hair loss. And so, on July 8—in a marathon 14-hour session—he sat while X-ray exposures were taken at various points around his head, including one inside his mouth. Levy suffered no pain, but within days, his skin turned an angry red and began to blister, his lips became swollen, cracked, and bleeding, his mouth was so burned he could only ingest liquids, and his right ear swelled grotesquely to twice its normal size. And, oh yes, the hair on the right side of his head fell out. The good news was that not only did two X-ray images reveal the location of the bullet, but within four months Levy had recovered sufficiently to ask the professor to take more X-rays to help doctors determine the feasibility of an operation.
Throughout 1896, reports of side effects like those experienced by Levy provided growing evidence that Roentgen’s invisible rays were not simply passing harmlessly through the body. Some scientists, doubting that X-rays were to blame, suggested instead that the burns and hair loss were caused by the electrical discharges needed to produce the rays. Thus, it was proposed that the injuries might be avoided if X-rays were produced instead by “static” machines. But it did not take long for scientists—wielding their own swollen and burned fingers as proof—to show that the X-rays emitted by these machines were just as harmful. And so within a year of their discovery, it was increasingly clear that X-rays could cause short-term damage to tissues. What nobody yet suspected, however, was that the rays might cause long-term effects.
That direct exposure to X-rays could damage the body is hardly surprising given that exposure times in the early years were often an hour or longer. And of course patients were not the only ones at risk. One of the tragedies of early X-ray research is that it was often the scientists and clinicians who—having exposed their own hands and fingers to the rays day after day—suffered first and worst. One famous case was that of Clarence Dally, who assisted Thomas Edison in his early work in X-rays and often held objects beneath the rays with no protection. Dally eventually developed severe burns to his face, hands, and arms. In 1904, despite amputation of both his arms in an attempt to stop recurrent cancer, Dally died. While this tragic event helped alert the world to the dangers of X-rays, it also prompted Edison to abandon his X-ray research, despite his pioneering work in developing the fluoroscope and other achievements.
Interestingly, some early pioneers, thanks to a combination of intuition and luck, managed to escape harm. Roentgen, for example, conducted many of his experiments in a large zinc box, which provided the necessary shielding. And Francis Williams protected himself from the very start of his work because, as he later explained, “I thought that rays having such power of penetrating matter must have some effect upon the system, and therefore I protected myself.”
Unfortunately, the early years of unshielded X-ray use eventually took their toll on many early pioneers. In 1921, following the deaths of two famous radiologists in Europe, the New York Times published an article about the dangers of unprotected exposure to X-rays, listing a number of radiographers and technicians who had died between 1915 and 1920. Many of them, like Dally, endured multiple operations and amputations in a futile attempt to stop the spread of cancer. And some were heroic in facing the inevitable. After suffering facial burns and the amputation of his fingers, Dr. Maxime Menard, chief of the “electro-therapeutic” department at a hospital in Paris, reportedly said, “If the X-rays get me, at least I shall know that with them I have saved others.”
Eventually, a new understanding of X-rays and their biological effects helped clarify the risks. As we now know, X-rays are a form of light (electromagnetic radiation) so intensely energetic that they can strip electrons from atoms and thereby alter cellular functions at a molecular level. Thus, when X-rays pass through the body, they can have one of two major effects on cells, either killing them or damaging them. When cells are killed, short-term adverse effects such as burns and hair loss may occur. But if the X-rays “merely” damage DNA without killing the cell, the cell can continue to divide and pass the mutated DNA on to daughter cells. Years or decades later, these mutations can lead to the development of cancer.
Fortunately, by 1910, the hidden dangers of X-rays had been exposed, and protective goggles and shielding were used with growing frequency by scientists and clinicians. Having passed this dark milestone, X-rays could now move on to an even brighter and safer future in medicine.
Milestone #6 A leap into the modern age: Coolidge’s hot tube
From the day Roentgen first announced his discovery, scientists following in his footsteps began tinkering with various components of the equipment in attempts to make X-ray images sharper, shorten exposure times, and achieve better penetration of the body. It was one thing to create images of bones in the hands, which are relatively thin, flat, and easy to hold still for long exposures; capturing images of organs deep in the chest and abdomen was far more challenging. While a succession of technical improvements during the first decade or so allowed radiographers to create X-ray images of numerous body organs, image quality and exposure times remained a key limitation. And these were largely due to the design of the X-ray tube itself.
The basic problem with early tubes such as the Crookes tube was they were not true vacuum tubes: The tubes always contained some residual gas molecules. This was both good and bad. On the one hand, gas molecules were needed to create X-rays, given that it was their collision against the cathode that created cathode rays, which in turn created X-rays. On the other hand, the residual gas molecules were a problem because with repeated use, they altered the composition of the glass tube itself and disrupted its ability to produce X-rays. While the altered tubes produced more penetrating X-rays, the intensity was decreased, resulting in poorer image quality. The end result was that, over time, X-ray tubes became erratic—so much so that Roentgen once wrote in a letter, “I do not want to get involved in anything that has to do with the properties of the tubes, for these things are even more capricious and unpredictable than women.”
While many clever designs were implemented to compensate for the technical limitations of early X-ray tubes, the true milestone—what some experts call “the single most important event in the progress of radiology”—did not occur until nearly 20 years later. In 1913, William Coolidge, working in the General Electric Research Laboratory, developed the first so-called “hot” X-ray tube, subsequently called the Coolidge tube. Based on his earlier research, Coolidge had figured out how to make the cathode out of the metal tungsten, which has the highest melting point of all metals. With a cathode made primarily of tungsten, cathode rays could be generated by running an electric current through the cathode and heating it; the more the cathode was heated, the more cathode rays it emitted. Thus, with cathode rays generated by heat rather than gas molecule collisions, the Coolidge tube could operate in a perfect vacuum.
Thanks to these and other design changes, the Coolidge tube was not only more stable—producing consistent, reliable exposures—but operators could also now independently control X-ray intensity and penetration. X-ray intensity was controlled by changing the temperature of the cathode, while penetration was controlled by changing the tube voltage. Finally, by operating in a true vacuum, Coolidge tubes were less finicky and could function almost indefinitely, unless broken or badly abused.
By the mid-1920s, the Coolidge tube had essentially replaced the old gas-filled tubes. In addition, Coolidge later designed other innovations so that higher voltages could be used to produce higher frequency X-rays. This led to the development of so-called “deep therapy,” in which X-rays are used to treat deeper tissues without excessively damaging outer layers of skin. Thanks to Coolidge’s milestone redesign of the X-ray tube, the use of X-rays in medicine—for both diagnostic and therapeutic applications—expanded widely throughout the world from the 1920s and onward. Today, Coolidge’s “hot” tube design is still the basis for all modern X-ray tubes.
Milestone #7 A final secret revealed: the true nature of X-rays
If you were a scientist or layman in 1896 and fascinated by the discovery of X-rays, you probably would have been equally intrigued, if not amused, by some of the theories attempting to explain what they were. For example, physicist Albert A. Michelson curiously suggested that they were “electromagnetic whirlpools swirling through the ether.” And there was Thomas Edison’s proposal, eventually discredited as “nonsense,” that X-rays were “high-pitched sound waves.” Other theories included the view that—despite evidence to the contrary—X-rays were actually cathode rays.
Interestingly, Roentgen was closer to the mark in his landmark 1895 paper when he observed that X-rays were similar to light because, for example, they created images on photographic film. Yet he also observed that X-rays were different than light because they could not be diffracted by a prism or “bent” by magnets or other substances. With these and other contradictory observations, the mysterious nature of X-rays entered the greater debate among physicists at the time as to whether light was made up of particles or waves. But before long, increasing evidence suggested that X-rays were indeed a form of light—that is, a form electromagnetic radiation that traveled through space in waves. Roentgen and others had been initially misled because the wavelengths of X-rays are so incredibly short—in fact, 10,000 times shorter than visible light.
The final proof came on April 23, 1912, when physicist Max von Laue performed a milestone experiment. Von Laue had been contemplating how to show that X-rays were truly electromagnetic waves and—in what might seem to be an unrelated problem—whether the atoms in a crystal are arranged in a regular lattice-like structure. In a brilliant insight, von Laue addressed both questions with a single experiment. He sent a beam of X-rays through a crystal of copper sulphate, theorizing that if the atoms were indeed structured as a lattice—and if X-rays were indeed composed of waves—the spacing between the atoms might be sufficiently small to diffract the tiny X-ray waves. Von Laue’s experiment confirmed both theories. Based on the distinctive “interference” pattern the X-rays made when they emerged from the crystal and struck a photographic plate, von Laue was able to deduce that the atoms in a crystal are indeed arranged in a lattice and that X-rays travel in waves and are therefore a form of light. For his milestone discovery, von Laue received the 1914 Nobel Prize in Physics.
The twentieth century and beyond: the milestones keep on coming
While the milestones discussed here represent the most important advances in the discovery and application of X-rays to medicine, in recent years newer milestones have continued the revolution. Some of these milestones, such as the development of contrast agents, are so broad that they apply to many areas of diagnostic radiology. Others are specific to a given body region but still have profoundly impacted medicine and health. One example is mammography, the use of low-dose X-rays to detect and diagnose breast cancer. Although X-rays were first used to examine breast disease in 1913 by German surgeon Albert Salomon, the initial techniques were crude and unreliable. In 1930, radiologist Stafford Warren was one of the first investigators to provide reliable data on the clinical use of breast X-rays. But it was not until 1960 that Robert Egan, a radiologist at the University of Texas, published a landmark study in which he described mammography techniques that could attain 97% to 99% accuracy in detecting breast cancer. Egan’s results proved the validity of mammography and led to its widespread use in breast cancer screening. By 2005, mammography accounted for 18.3 million office visits in the United States, or about 30% of all X-ray exams.
But perhaps the most astonishing recent milestone was the development of an entirely new way of using X-rays to reveal the inner world of the body. Until the 1970s, all X-ray images had one major limitation: They were flat and two-dimensional. Lacking depth, X-ray images of internal organs are often obscured by overlapping organs and tissues that cause unwanted shadows and reduced contrast. This is why physicians, in an effort to gain additional perspective, often order two X-ray images (one from the front and one from the side). But in 1971, British engineer Godfrey Hounsfield overcame this limitation with the development of computed tomography (CT), in which X-rays are used to take a series of cross-sectional images, or “slices,” of the body area being examined. (Tomos is a Greek word that means to cut or section.) With CT, instead of sending a single beam through the body to create a single image, X-rays are sent through the patient multiple times from multiple angles around the body and collected by detectors that convert them into electrical signals. These signals are then sent to a computer, which reconstructs the data into detailed cross-sectional “slices” that can be assembled into three-dimensional images. Because the image data doesn’t overlap while the image is being constructed and because CT detectors are more sensitive than film, CT can show much finer variations of tissue density than conventional X-rays.
The development of CT was aided by two key developments in the 1960s and 1970s. One was the advent of powerful minicomputers, which were needed to process the enormous amount of data captured by X-ray detectors and reconstruct it into images. The second was the work of Alan Cormack, who created a mathematical model for measuring different tissue densities in the body and predicting how this information could be used to create cross-sectional X-ray images. For their work in developing CT, Hounsfield and Cormack were awarded the 1979 Nobel Prize in Physiology or Medicine.
In its early uses, CT produced the first clear images of the brain’s gray and white matter and thus had a major impact on the diagnosis of neural diseases. Since then, numerous advances have led to faster scanning, thinner slices, and the ability to scan larger body areas. Today, CT scanners can produce exquisite, 3D images in virtually every part of the body. One recent application, for example, is virtual colonoscopy, in which CT produces images of the interior of the large intestine. Less invasive than the conventional method of threading a long, flexible optical tube through the colon, virtual colonoscopy is becoming an increasingly important tool in screening for colon cancer.
A remarkable range of uses—but always medicine’s trustworthy guide
Apart from their role in medicine, X-rays have had a major impact in numerous other areas of science and society. Within years of their discovery, X-rays were put to use in many areas of industry, including detecting flaws in iron castings and guns, examining submarine telegraph cable insulation, inspecting the structure of airplanes, and even examining live oysters for pearls. X-rays have also found important applications in basic biology (revealing the structure of proteins and DNA), the fine arts (detecting fraudulent imitations of paintings), archeology (assessing objects and human remains at archeological sites), and security (inspection of baggage, packages, and mail).
But for their sheer impact on saving or improving human lives, X-rays have made their greatest impact in the field of medicine. According to the Centers for Disease Control and Prevention (CDC), X-rays are still one of the most common medical tests. For example, in 2005 X-rays were ordered in 56.1 million office visits, making them nearly twice as common as ultrasound, MRI, and PET imaging tests. In terms of frequency of diagnostic tests given in an office visit, X-rays rank behind only three major blood tests (CBC, cholesterol, and glucose) and urinalysis.
Of course, X-rays have important limitations that cannot be overlooked. Today, for example, they are often used with or replaced by other imaging technologies, such as MRI, ultrasound, and PET, to provide anatomic and physiologic insights that X-rays alone could never achieve. In addition, the cumulative effects of X-rays continue to be a concern and play a role in determining the viability of some new applications. For example, CT angiograms are a promising new tool for non-invasively examining the coronary arteries and assessing heart disease risk. However, CT angiograms can expose patients to the equivalent of at least several hundred standard X-rays, thereby posing a small but real cancer risk. Thus, as with all evolving technologies, even the most exciting milestones must be continually evaluated for their balance of risks and benefits.
Nevertheless, it would be a shame if we ever lost that sense of awe and appreciation that shook the world when X-rays were first discovered, when those tiny, invisible waves of light first began opening unimagined new views into the human body. Nor should we forget that sometimes the images they unveil—whether bullets, bones, needles, or cancer—have little to do with hidden mysteries or secrets.
Take the case of the 39-year-old construction worker who was injured in 2004 in a grisly nailgun accident. There was no mystery when the nailgun suddenly fired six 3-inch nails into his face, spinal column, and skull, sending him to a Los Angeles hospital fearing for his life. Or the 59-year-old German woman who, when she was just four years old, fell down while carrying a 3-inch pencil. There was no secret when the pencil pierced her cheek and disappeared into her head, causing a lifetime of headaches, nosebleeds, and loss of smell. But in both cases, X-rays helped doctors locate the invaders and perform the surgery needed to successfully remove them.
In such cases, X-rays are more like a trustworthy guide, the same reliable friend that first helped doctors remove a needle from a woman’s hand, just two days after the announcement of their discovery. More than a century later, in both diagnosis and treatment, X-rays continue to provide the roadmaps and tools doctors need to save or improve the lives of millions.