Photon Interactions Wrap Up

Seeing the full picture of how photons behave across energy ranges.

Now that we’ve explored the main types of photon interactions, let’s bring it all together.

(Image credit: https://oncologymedicalphysics.com/radiation-interactions/)

Each interaction behaves differently depending on the photon energy and the atomic number of the material it encounters. At low energies, the photoelectric effect dominates, creating the contrast that makes diagnostic imaging possible. As energy increases, Compton scattering takes over, making it the key interaction in radiation therapy for soft tissues. At even higher energies, pair production becomes significant, especially in materials with high atomic numbers.

Coherent scattering, though less influential, completes the picture by showing how photons can scatter without losing energy.

By understanding how these interactions vary across energy levels, you gain a clearer view of why imaging and therapy use different energy ranges, and how each process contributes to patient care.

Always aligned with good energy,

Sara

P.S. I hope this series has helped you see how each photon interaction plays its part in both imaging and therapy. Keep exploring, stay curious, and remember that understanding these fundamentals builds the foundation for everything you’ll do in clinical practice.