What is the x-ray beam that leaves the tube called?

The x-ray beam that exits the tube is referred to as primary radiation. This term specifically describes the unscattered and direct radiation produced by the x-ray tube, which is aimed at the patient or subject being examined. Primary radiation is critical in diagnostic imaging because it directly interacts with the materials in the imaging path to create an image.

In medical imaging, understanding the distinction between primary radiation and other types of radiation is essential. Secondary radiation, for instance, is produced as a result of primary radiation interacting with matter, leading to scatter, and it does not contribute to the diagnostic image quality. Collimated radiation refers to x-rays that have been narrowed down to a specific area, typically after passing through the primary beam. While exit radiation may refer to x-rays that have passed through the patient, it is not the standard term used to describe the initial x-ray beam leaving the tube. Thus, primary radiation is the most accurate choice for describing the beam emitted directly from the x-ray tube before any interaction with the patient or surrounding materials.