Interaction between X-ray photon and high-atomic-number atom

This "target" describes the fundamental physical processes by which X-ray photons interact with high-atomic-number (high-Z) atoms, such as iodine, barium, gadolinium, or hafnium. These interactions are dominated at diagnostic and therapeutic X-ray energies by the photoelectric effect: the X-ray photon is fully absorbed and its energy is transferred to an inner-shell electron, causing ionization and emission of secondary electrons and characteristic X-rays[2][3][4][5][6]. High-Z atoms are used in medical imaging (such as CT contrast agents) and radiation therapy dose enhancers due to their increased probability of photoelectric interaction with X-ray photons, which scales strongly with atomic number, thereby improving image contrast and/or increasing local dose deposition in tumors. This is not a classical biological or therapeutic target, but rather a physicochemical interaction exploited for clinical benefit[1][4][8].

Other names

Photoelectric effect with high-Z atomsX-ray–high-Z interactionX-ray absorption by heavy elements

X-ray absorption via the photoelectric effect, where an X-ray photon is absorbed by an inner-shell electron, leading to ionization and secondary photon/electron emission[2][3][5][6] Compton scattering, where an X-ray photon transfers part of its energy to an electron, altering its path and energy[2][7] Secondary generation of characteristic X-rays and Auger electrons, enhancing local dose or image contrast[3][4]