For thousands of years, bonesetters and doctors could not accurately diagnosis broken bones or differentiate such injuries from joint dislocations and torn ligaments. That changed with a chance discovery almost exactly 125 years ago. Subsequently, perhaps with equal parts of chagrin and enlightenment, doctors began using the new discovery to discount their previous assumptions and accurately diagnose skeletal diseases.
In his darkened laboratory on November 8, 1895, a German mechanical engineer and physicist, Wilhelm Röntgen, electrified a vacuum tube and happened to observe a strange glow coming from a nearby card, one that he had coated with a photosensitive chemical. He turned the electricity off. The glow disappeared. He turned it back on and placed his hand in front of the card. A shadow of his hand appeared. With the weekend upon him, Röntgen repeated and varied the experiment. Over the following weeks, he ate and slept in his laboratory and studied this unknown ray, which he labeled “X,” the mathematical symbol for an unknown.
He learned that X-rays passed through books, no matter how thick, and that coins cast a shadow on the photosensitive board. Six weeks later, Röntgen shared the secret with his wife, who allowed him to take a fifteen-minute exposure of her hand, the first orthopedic X-ray. When she saw the image of her hand skeleton, she exclaimed, “I have seen my death.” Far more broadly, she was witnessing the advent of diagnostic radiology and modern orthopedic surgery.
A week later, Röntgen presented his findings in a paper titled, “On a New Type of Rays.” This caught the immediate attention of physicists, who alerted the lay press. The discovery made the front-page headline news within a week of Röntgen’s public presentation.
At the time, vacuum tubes were well known and easy to make. After Röntgen’s discovery and announcement, many investigators contributed to the understanding and practical applications of X-rays. Interest was intense, and advances were rapid. Less than three months after Röntgen’s public announcement, an enterprising electrical contractor and avid photographer opened a laboratory offering diagnostic services.
Röntgen received the Nobel Prize in 1901, the first one ever awarded for physics. Röntgen not only gave the reward money to his university, but he also refused to take out patents on his discovery to allow for a wide-spread application.
I suppose when X-rays were in their infancy, patients were asking, “Now that you have finished obtaining a thorough medical history, performing a careful physical examination, and telling me that you know with assurance what is wrong, aren’t you going to order an X-ray, Doctor?” This question implied a lack of trust in the doctor’s diagnosis unless he threw in a high-tech, oh-so-modern X-ray evaluation. Gradually, doctors and patients came to understand when an X-ray study could help make the diagnosis or plan treatment and when one would be superfluous. For instance, today it is intuitive that a sore tooth most likely deserves an X-ray while a sore throat does not. In general, X-rays reveal calcium-rich structures—those containing enough calcium to cast a shadow in the X-ray beam. Examples are bones, teeth, hardened arteries, and kidney stones.
Doctors have learned to order X-rays with some caution because radiation damages living tissues and their DNA. That fact required discovery, and the harmful effects of early X-ray examinations were slow to reveal themselves. Since X-rays could not be seen or felt, investigators had no reason to consider them harmful. Both Nicola Tesla and Thomas Edison experimented with X-rays, and both observed that their eyes became irritated; but neither drew a connection between the radiation and their symptoms.
For convenience, dentists originally held the film inside the patient’s mouth with their fingers when shooting dental X-rays. Decades later, the skin on their hands dried, cracked, and became cancerous. I have been fortunate to escape similar problems. In the 1950s, I watched my toe bones wiggle under fluoroscopy in the shoe department at Sears, and in the 1960s, I received enough radiation for acne that it left me “sunburned.” Nowadays, the radiology tech steps behind a lead shield before shooting the film, and there are generally accepted standards for how much radiation a person can receive on an annual and lifetime basis without incurring undue risk.
Advances in the production, delivery, receipt, and interpretation of Röntgen’s rays continue to be tweaked to reduce exposure and enhance image quality. About 75 years after Röntgen’s discovery, a major advance came along—computed tomography, or CT scanning, also known as computed axial tomography—CAT scanning. The concept is simple. X-rays cast a shadow when portions of the beam are interrupted, just as the sun casts a visible shadow of a lobster pot’s wooden slats. That is fine if you are interested in the pot, but what if you are instead interested in imaging the lobster inside? From any given angle, you cannot see the entire lobster. What to do? Walk around the lobster pot and take a photo every thirty degrees—one o’clock, two o’clock, and so forth, knowing that the lattice will obscure part or all the lobster from some positions. Nonetheless, by combining the twelve images, you can later accurately estimate the lobster’s missing contours and dimensions. A CT scanner takes pictures from over one hundred evenly spaced positions. CT scanning became practical because of the advent of high-speed computers, which process the X-ray images taken from all the angles and construct images of the area of interest unobscured by overlying structures. At first, it took hours for the computer to acquire the raw data and create images. Now acquiring and processing the image takes seconds. Development of computed tomography rewarded Godfrey Houndsfield, working in England, and Allan Cormack, working in the United States, with Nobel Prizes in 1979.
In orthopedics, CT scanning is most helpful in two instances. The first is when a soft-tissue area of interest is surrounded by bone, for example, where nerve roots emerge from the spine. The other is when a shattered fracture involves a joint or a complex anatomical area, such as the pelvis. Computer-generated three-dimensional renderings of the CT scan can help the surgeon visualize the injury and plan a reconstruction. Although such images are impressive, CT scanning exposes the patient to considerable radiation.
When viewing their plain X-ray or CT images with me, patients often ask, “How do my bones look? Do I have osteoporosis?” Remember two facts. First, osteoporosis means porous, fragile bone that is prone to fracture because it has diminished calcium content. This occurs naturally with aging and inactivity and accelerates in women after menopause. Second, a routine X-ray study does not reveal the presence or absence of osteoporosis. Factors that keep a normal X-ray study from revealing bone mineral density include the thickness of the surrounding soft tissues and the X-ray beam’s duration and intensity.
DXA scanning, which is a lot easier to say than dual-energy X-ray absorptiometry, solves the problem and can accurately determine osteoporosis’s presence and severity. Two standardized X-ray beams, one low- and one high-energy, are aimed at the same area of bone, typically in the lower back and hip. These areas are chosen because they wreak the most havoc when they collapse from inadequate calcium support. The soft tissues absorb most of the low-intensity beam, so subtracting its effect from that of the high-intensity beam leaves the amount of X-ray that the bone absorbed. It is a bit like somebody saying that it takes ten minutes to drive to work. That measurement has much more meaning if they also tell you how long it takes to walk there.
Despite our best efforts, we cannot avoid radiation exposure entirely. Some come naturally from the sun and some from the ground. We get more during a plane flight because the thinner air at high altitude blocks less of the sun’s radiation. This fact poses a major, unsolved problem for interplanetary travel because of the absence of Earth’s radiation-shielding atmosphere and because of the impracticality of armoring spaceships with lead. Stay tuned, or maybe just stay earthbound. Even so, for reference, 100 DXA scans equal the radiation of one chest X-ray, which is about the amount of radiation one receives by merely hanging out on Earth for 12 days, which is about one-fourth the radiation exposure from a mammogram, which is about 6% of a low back CT scan.
However, most would agree that the potential benefits of a timely chest X-ray or mammogram far outweigh the risks. Even an occasional and judiciously planned CT scan may help maintain or restore your health, but avoid advice such as, “I don’t have a clue about what’s wrong, so let’s get a CT scan.” A second opinion is safer. Remember, it took decades for the damaged DNA in dentists to turn into skin cancers. Similarly, avoid being your own doctor and proclaiming, “I would just feel better, Doctor, if you ordered a CT scan.”
Röntgen discovered his new type of ray a few decades after the introduction of general anesthesia and the acceptance of aseptic surgical techniques. These developments, along with the invention of stainless steel, ushered orthopedic surgery and the practicality of operative fixation of fractures into the modern era. Looking ahead 125 years, fractures will still exist. Arthritis and osteoporosis may be fully preventable by then. Bone imaging techniques will be even more sophisticated than those in current use. X-ray imaging may be obsolete, replaced completely by magnetic resonance imaging, ultrasound, or some yet-to-be-discovered alternative. Nevertheless, Röntgen’s discovery and its enduring 125-year legacy deserve recognition.
Roy A. Meals is an orthopedic surgeon who blogs at About Bone.
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