Which statement about attenuation is accurate?

Which statement about attenuation is accurate?

• A. It increases with higher atomic number and higher density
• B. It decreases with higher atomic number
• C. It is independent of tissue density
• D. It increases with lower density

Answer: (A)

Attenuation of X-rays in tissue increases when density is higher and when the atomic number is higher. A denser material has more atoms per unit volume for the photons to interact with, so there’s more absorption and scattering, which reduces beam intensity. A higher atomic number increases the probability of interactions, especially photoelectric absorption at diagnostic energies, further increasing attenuation. This makes bones, which are both dense and high in Z, attenuate the beam more than soft tissues, producing the bright appearance on radiographs. So the statement that attenuation increases with higher atomic number and higher density is the best choice. Attenuation is not independent of density, it does not increase with lower density, and it does not decrease with higher atomic number.

Attenuation of X-rays in tissue increases when density is higher and when the atomic number is higher. A denser material has more atoms per unit volume for the photons to interact with, so there’s more absorption and scattering, which reduces beam intensity. A higher atomic number increases the probability of interactions, especially photoelectric absorption at diagnostic energies, further increasing attenuation. This makes bones, which are both dense and high in Z, attenuate the beam more than soft tissues, producing the bright appearance on radiographs.

So the statement that attenuation increases with higher atomic number and higher density is the best choice. Attenuation is not independent of density, it does not increase with lower density, and it does not decrease with higher atomic number.