An x-ray photon absorbed in the phosphor layer of a computed radiography plate occurs through which interaction?

An x-ray photon absorbed in the phosphor layer of a computed radiography plate occurs through which interaction?

• A. Characteristic
• B. Photoelectric
• C. Compton
• D. Classical

Answer: (B)

Absorption in the phosphor layer happens mainly through the photoelectric effect. In high‑Z phosphor materials used for computed radiography, an incident x-ray photon is completely absorbed when it ejects a tightly bound inner-shell electron. The energy of the photon minus the binding energy goes into the ejected electron, and the resulting vacancies and excited states lead to energy being stored in traps that ultimately produce visible light when read out. This full absorption and energy transfer is what makes the photon’s energy contribute to the plate’s stored signal. Compton scattering, by contrast, would only transfer part of the energy to a loosely bound or free electron and the photon would be scattered away, not absorbed. Classical (Rayleigh) scattering involves minimal energy transfer and is not a primary absorption mechanism. Characteristic x-ray emission can occur after photoelectric absorption, but the initial absorption process is the photoelectric effect itself.

Absorption in the phosphor layer happens mainly through the photoelectric effect. In high‑Z phosphor materials used for computed radiography, an incident x-ray photon is completely absorbed when it ejects a tightly bound inner-shell electron. The energy of the photon minus the binding energy goes into the ejected electron, and the resulting vacancies and excited states lead to energy being stored in traps that ultimately produce visible light when read out. This full absorption and energy transfer is what makes the photon’s energy contribute to the plate’s stored signal.

Compton scattering, by contrast, would only transfer part of the energy to a loosely bound or free electron and the photon would be scattered away, not absorbed. Classical (Rayleigh) scattering involves minimal energy transfer and is not a primary absorption mechanism. Characteristic x-ray emission can occur after photoelectric absorption, but the initial absorption process is the photoelectric effect itself.