Which pathology will result in decreased attenuation of the x-ray beam?

• A. Tibial fracture
• B. Penumbra
• C. Osteoporosis
• D. Cellulitis

Answer: (C)

Attenuation depends on tissue density and composition; denser tissues absorb more photons. Bone normally attenuates a lot because of its calcium content, but osteoporosis reduces bone mineral density, thinning trabeculae and cortex. With less mineral density, bone absorbs fewer photons, so more x-rays pass through—the image shows decreased attenuation and a more radiolucent (lighter) appearance. The other options don’t cause this broad drop in attenuation: a fracture changes the bone’s outline but not the overall density; penumbra is an imaging blur or edge effect, not a pathology; cellulitis affects soft tissue, not bone mineral density, so it doesn’t produce the same decrease in attenuation.