Which photon-tissue interaction is often described as classical or Thomson scattering?

Which photon-tissue interaction is often described as classical or Thomson scattering?

• A. Photoelectric interaction
• B. Compton interaction
• C. Coherent scatter
• D. Pair production

Answer: (C)

Coherent scattering is when a photon interacts with an atom and changes direction without losing energy. In the classical view, this elastic scattering is described as Thomson scattering: the electromagnetic wave drives the electrons, causing them to scatter the wave, but the photon emerges with essentially the same energy it had before. This description works best at lower photon energies where there isn’t enough energy to knock electrons free or create new particles. It contrasts with the photoelectric effect, where the photon is absorbed and an electron is ejected; with Compton scattering, the photon loses energy to a recoil electron and is scattered with reduced energy; and with pair production, a high-energy photon is converted into an electron–positron pair in the nucleus’s field. In tissues, coherent (Thomson) scattering is an elastic process that contributes to scattering at small angles and preserves photon energy, which is why it’s described using the classical Thomson picture.

Coherent scattering is when a photon interacts with an atom and changes direction without losing energy. In the classical view, this elastic scattering is described as Thomson scattering: the electromagnetic wave drives the electrons, causing them to scatter the wave, but the photon emerges with essentially the same energy it had before. This description works best at lower photon energies where there isn’t enough energy to knock electrons free or create new particles. It contrasts with the photoelectric effect, where the photon is absorbed and an electron is ejected; with Compton scattering, the photon loses energy to a recoil electron and is scattered with reduced energy; and with pair production, a high-energy photon is converted into an electron–positron pair in the nucleus’s field. In tissues, coherent (Thomson) scattering is an elastic process that contributes to scattering at small angles and preserves photon energy, which is why it’s described using the classical Thomson picture.