Which type of interactions do not reach the image receptor but provide diagnostic information by representing anatomic structures?

The photoelectric effect is the correct choice because it is the interaction that occurs when an incoming photon is completely absorbed by an inner-shell electron of an atom, typically in biological tissue. In this process, the photon transfers all of its energy to the electron, allowing the electron to overcome the binding energy and be ejected from its shell. This results in the emission of secondary electrons and leads to ionization of the atom.

The photoelectric effect is instrumental in generating contrast in medical imaging, especially in radiography, where it provides diagnostic information by contrasting different tissue densities. Tissues with higher atomic numbers and densities, like bone, will absorb more photons, appearing white on the radiographic image. In contrast, softer tissues absorb fewer photons and appear darker. Although the interaction does not directly produce radiation that reaches the image receptor, it contributes to the differential absorption of photons in various tissues, enabling the formation of an image that displays anatomical structures.

In contrast, other types of interactions mentioned, such as Compton scattering, pair production, and photodisintegration, typically involve different mechanisms that may not serve the same illustrative purpose in diagnostic imaging. Compton scattering can cause photons to scatter and reach the image receptor, affecting image quality. Pair production occurs only at