SIC 3844 X-Ray Apparatus and X-Ray Tubes
SIC 3844
Firms in this industry engage primarily in manufacturing irradiation apparatus and tubes for applications such as medical diagnostic, medical therapeutic, industrial, research, and scientific evaluation.
334517
Irradiation Apparatus Manufacturing
After growing by an average of 8 percent annually during the early 2000s, the X-ray apparatus and tubes industry fell off slightly during 2003 to $4.38 billion, down from $4.52 billion in 2002. However, by the mid-2000s the industry was once again making positive gains. Numerous advances were made in imaging technologies. The increasing sophistication of computed tomography, which was undergoing rapid technological advancements, was driving growth in the industry. Also, handheld and portable X-ray devices were becoming more widely used in the offices of doctors, dentists, and veterinarians, as well as having a variety of industrial and manufacturing applications. X-ray equipment also was on the forefront during the mid-2000s as a method of security against terrorist attacks.
In the mid-2000s approximately 150 U.S. companies were involved in the irradiation apparatus industry, an increase of about 10 percent from the late 1990s. However, the largest companies (those with more than 500 employees), which accounted for less than 8 percent of all establishments, commanded more than two-thirds of the industry's revenues. Establishments with more than 50 employees, which made up about one-third of the industry, accounted for more than 90 percent of total shipment values. California, Illinois, and Massachusetts had the most establishments, with 33, 22, and 16, respectively. Those three states accounted for approximately 58 percent of the industry's total revenues.
The discovery of the X-ray was an accident. In 1895, Wilhelm Conrad Roentgen, experimenting with electrical discharges in an evacuated tube called a Crookes' tube, discovered that the invisible rays given off from his experiment could penetrate a human hand and project a skeletal image onto a florescent screen. Later, he substituted photographic film to make a permanent record. Since then, scientists have discovered that X-rays are a type of electromagnetic radiation. An X-ray's wavelength of 0.01 to 300 angstroms is shorter than visible light, lying between and partially over the ultraviolet and gamma-ray segments of the electromagnetic spectrum. They are produced by the collision of high-energy particles with other charged particles.
American scientist William D. Coolidge developed the first efficient X-ray tube, called a Coolidge tube, in 1913. Modern tubes fire electrons from a tungsten filament cathode at a target anode, usually made of tungsten, molybdenum, or copper and coated with a thin film of gold.
The speed of passage of the x-radiation through a body depends on density. Relatively dense material, like bone, yielded white images, whereas less-dense material like lungs appeared black. Doctors found the phenomenon invaluable for accurately diagnosing such things as tuberculosis, miners' black lung, and broken bones. However, it only provided a two-dimensional image of the problem area, superimposing layers of body components one on top of another without any indication of depth. One solution to that problem was to use a contrast medium like liquid barium to highlight the esophagus, stomach, and intestine. By using a fluoroscope, which produces real-time images on a video screen, the physician tracked the medium through the digestive system, pinpointing any problem areas.
The late 1960s saw a major advancement in the effective use of X-rays for medical diagnosis. By linking the computer to a moving X-ray emitter inside a doughnut-shaped machine, Geoffrey Hounsfield of EMI produced a three-dimensional image of an entire object. Instead of a few X-ray photographs, the computer-aided-tomograph (CAT) took hundreds of thousands of carefully directed, slice-like images, which the computer reassembled. Tomograph comes from the Greek word for slice. The results, startlingly clear, could be manipulated to highlight specific areas. CAT scans could locate bleeding inside a brain, find and measure tumors, or help to evaluate injuries anywhere in the body.
Concerns over the amount of radiation a patient would be exposed to and the cost and sheer physical immensity of the equipment led to the development of ultrasound tomograph, which did not use X-rays. By the mid-1980s, the ultrasound systems were beginning to gain popularity. Ultrasound systems are classified under SIC 3845: Electromedical Apparatus.
Magnetic Resonance Imaging (MRI) uses a powerful magnet to align the hydrogen atoms in a patient's body. When the magnetic field is released, the atoms return to their original orientation, but different tissues realign at different rates. By using a computer to clock the relative rates of change, physicians can map joints, tumors, and post-surgical changes in the chest, abdomen, pelvis, brain, and spinal cord.
The safety and effectiveness of all medical devices became the responsibility of the Food and Drug Administration in 1938. Radiation emitting devices were specifically targeted in 1968 by the Radiation Control for Health and Safety Act and, in 1976, by the Medical Device Amendments to the Food, Drug, and Cosmetic Act.
In the late 1990s, the continued concern for radiation exposure to patients led to further advances in X-ray equipment development and technological advances. One of the technological advances in 1997, called a "soft" X-ray, was a new technology that used long wavelengths to decrease radiation.
Even though other, safer technologies were displacing X-rays by the 1990s in their traditional medical applications, radiation proved useful in unique ways. The fluoroscope could show movement within the body like the operation of the heart and the intestines. It facilitated angioplasty, providing the physician with a real-time way of guiding a balloon-tipped catheter down a blood vessel to the point where the balloon insert could be expanded with the greatest effect. Radiation oncology used X-rays or gamma-rays to attack cancerous tumors without damaging surrounding tissue. With this technique a linear accelerator, betatron, or cobalt machine is used to direct a beam of radiation from outside the patient's body at the pinpointed tumor.
Initial investigations of the radiation in the research laboratory led to many useful applications for the nonvisible light energy. X-ray crystallography led to X-ray microscopes. Crystal structures direct and control X-rays much as lenses do with normal light energy. Using this principle, researchers were able to delve ever-deeper into the structure of crystals. The fact that X-rays are absorbed by material led to absorption spectroscopy, which studies metals in living systems. The industry began using lithography to produce densely packed computer chips. Holography made it possible to glimpse the world within a living cell.
Scientists also used the radiation to look beyond this world. By launching satellites equipped with X-ray detectors, they were able to observe and theorize about the structure of the universe. The first such satellite, UHURU, was launched from a site near Kenya in 1970 and was followed by an...
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