At low energy levels (30-50 keV), which tissue type has greater attenuation?

• A. Soft tissue
• B. Bone
• C. Muscle
• D. Air

Answer: (B)

At low energy levels, specifically between 30-50 keV, bone demonstrates greater attenuation compared to other tissue types. This is primarily due to the higher atomic number and density of bone compared to soft tissue, muscle, and air. Bone contains more calcium and phosphate, which are elements that have a higher atomic weight and therefore interact with X-ray photons more effectively, leading to increased absorption and scattering of X-rays.

Attenuation refers to the reduction in the intensity of X-ray beams as they pass through different types of tissues. The greater the density and atomic number of a material, the more it attenuates X-rays. Soft tissue, while also effective at attenuating X-rays, does so to a lesser extent than bone. Muscle, which is denser than soft tissue but still significantly less dense compared to bone, will also have a lower level of attenuation than bone at these energy levels. Air, being much less dense, attenuates X-rays the least.

Thus, at the specified energy range, the strong attenuation characteristic of bone makes it the correct choice.