Merck Manual

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    X-ray technology utilizes high-energy rays that can pass through certain body tissue and create imagery vital to diagnosis and treatment. The x-ray machine is composed of an x-ray tube that contains a pair of electrodes, or conductors, called a cathode and an anode.

    The cathode is a filament that releases energy with the introduction of an electrical current, much like that of a light bulb. The cathode energy is released in the form of electrons. The anode, located on the opposite end of the x-ray tube, is a disk made of tungsten, a material that attracts the electrons.

    When the electrons released from the cathode come in contact with the tungsten, they release energy in the form of photons. These highly energized photons are channeled through a lead cylinder and a series of filters, creating an x-ray beam. The x-ray beam is a high-energy beam that can be absorbed only by dense body tissues, such as bone.

    During an x-ray, a radiographic film is placed behind the patient, and the patient is placed between the film and the x-ray machine. The x-ray machine then focuses the energy beam at the specific area of the patient’s body.

    As the x-ray energy passes through the patient’s body, the photons of the beam reach the film and cause a chemical reaction: The areas where x-ray energy passes through the body become black, while the areas where energy is absorbed by the bones appear white. This process produces a radiograph, which is commonly referred to as an x-ray.