What type of radiation is considered the radiation that actually contributes to the image?

Primary radiation is the type of radiation that directly contributes to the formation of the image in radiographic imaging. This radiation is generated at the source, such as an X-ray tube, and travels through the patient to expose the imaging receptor. It is the unscattered, high-energy radiation that interacts with the imaging medium (like film or digital detectors) to create the desired diagnostic image.

In contrast, secondary radiation refers to the radiation that is scattered or emitted by the patient or other objects after the primary radiation interacts with them. This type of radiation can contribute to the overall exposure but does not directly form the image, as it may result in reduced image contrast and quality. Attenuated radiation refers to the X-rays that have undergone absorption or scattering as they pass through the body, which also does not contribute positively to image formation. Characteristic radiation occurs when electrons from an atom are ejected, leading to rearrangements and the emission of photons; while it plays a role in the overall X-ray production process, it is not the direct contributor to the image itself.

Therefore, primary radiation is the definitive answer, as it is the direct source of the information displayed in a radiograph.