But x-ray was far from a dead-end technology. Instead, it marked the start of a revolution in medical diagnosis. Like other medical imaging technologies that followed, including ultrasound, computed tomography ( or Cat Scan ) scanning, and magnetic resonance imaging ( or MRI ), x-ray can help doctors narrow down the causes of a patient's symptoms without surgery and sometimes diagnose an illness before symptoms even appear. X-rays imaging can be a useful first step in treating a range of problems, from a simple broken bone to a cancerous tumor. Roentgen labeled the rays he discovered with the scientific symbol "X," meaning unknown, because he didn't understand their makeup at first. x-rays are actually electromagnetic waves. When they are passed through a patient's body to a photographic film on the other side, they create a picture of internal body structures called a radiograph. The less dense a structure of the body is, the more radiation passes through it and reaches the film. The x-rays expose the film, changing its color after it is developed to gray or black, much like light would darken photographic film. Bones, as well as tumors, are more dense than soft tissues. They appear white or light on the x-ray film because they absorb much of the radiation, leaving the film only slightly exposed. Structures that are less solid than bone, such as skin, fat, muscles, blood vessels, and the lungs, intestines, and other organs, appear darker on the film because they let more of the x-rays pass through. Likewise, a break in a bone allows the x-ray beams to pass through, so the break appears as a dark line in the otherwise white bone. To make certain organs stand out more clearly, a "contrast medium" — a substance that blocks x-rays rather than transmitting any — can be introduced into the body, in the form of a drink or injection. Barium sulfate is commonly used to study the gastrointestinal tract, while iodine-containing dyes are often used to provide information about the gallbladder, kidneys, blood vessels (using a technique called angiography)
X-rays are electromagnetic radiation that differentially penetrates structures within the body and creates images of these structures on photographic film or a fluorescent screen. These images are called diagnostic x-rays. The x-ray technologist positions the patient appropriately, so that the part of the body to be x-rayed will be between the x-ray beam and the film plate. Usually the individual either lies on an adjustable table or stands. Parts of the body that are especially sensitive to damage by x-rays (for example, the reproductive organs, the thyroid) are shielded with a lead apron. Lead is very dense and effectively protects the body by stopping all x-rays. X-rays pass through the body and strike a photographic plate and interact with silver molecules on the surface of the film. Once the film plates have been processed, dense material such as bone shows up as white, while softer tissue shows up as shades of gray, and airspaces look black. A radiologist, who is a physician trained to interpret diagnostic x-rays, examines the pictures and reports to the doctor who ordered the tests. Plain film x-rays normally take only a few minutes to perform and can be done in a hospital, radiological center, clinic, doctor's or dentist's office, or at bedside with a portable x-ray machine. Although unnecessary exposure to radiation should be avoided, the low levels of radiation one is exposed to during an x-ray does not cause harm with a few exceptions. Pregnant women should not have x-rays unless in emergencies the benefits highly outweigh the risks. Exposure of the fetus to x-rays, especially during early pregnancy can increase the risk of the child later developing leukemia. Body parts not being x-rayed should be shielded with a lead apron, especially the testes, ovaries, and thyroid. Low dose exposure to x-rays creates minimal cell damage and minimal risk when x-rays are performed in an accredited facility. Doses of radiation received in most x-rays are quite similar to the environmental (background)
