Primary X-ray beam

Apuntes

Primary X-ray beam The source of x-rays is the x-ray tube. The internal structure and function of the tube are discussed in Chapter 5. X-rays are formed within a very small area inside the tube. From this point, the x-rays diverge into space. The x-ray tube is surrounded by a lead-lined tube housing. Some of the scattered x-rays are absorbed by the tube housing. X-rays that are created, exit the housing through an opening called the tube port. These x-rays form the triangular- shaped x-ray beam (Fig. 2-1). The radiation that leaves the tube is called primary radiation. The squared area of the x-ray beam that strikes the patient and x-ray table is called the radiation field. An imaginary line in the center of the x-ray beam and perpendicular to the long axis of the x-ray tube is called the central ray. The central ray is important in positioning the patient because this point is used to align the x-ray tube to the body part to be imaged. 51 FIG. 2-1 Terms for basic concepts in radiography. During a radiographic exposure, x-rays from the tube are directed through the patient to the image receptor (IR) (Fig. 2-2). As the x-rays pass through the patient, some of them are absorbed by th...