Which interactions contribute to attenuation of x-rays inside the body during radiography?

• A. 1 and 2
• B. 1 and 3
• C. 2 and 3
• D. 1, 2, and 3

Answer: (A)

Attenuation of x-rays in the body mainly comes from interactions that remove photons from the original beam. The two key processes responsible are photoelectric absorption, where the photon is completely absorbed and an inner-shell electron is ejected, and Compton scattering, where the photon is deflected and loses energy. Both of these reduce the number of photons that reach the detector, contributing to image formation and contrast.

Coherent (Rayleigh) scattering, while it does scatter some photons elastically, has a much smaller role in attenuating the beam at diagnostic energies, and most scattered photons stay outside the forward beam or are of negligible energy change. Therefore the combination that best explains attenuation is the two interactions of absorption and Compton scattering, making that option the correct one.