In tissues that attenuate sound greatly such as lung or bone, the HVL is:

In tissues that attenuate sound greatly such as lung or bone, the HVL is:

• A. Thick
• B. Medium
• C. Variable
• D. Thin

Answer: (D)

Half-value layer is the thickness of material needed to cut the beam’s intensity in half. The attenuation follows I = I0 e^{-μx}, so the thickness that halves the beam is x1/2 = ln(2)/μ. When the attenuation coefficient μ is large, the required thickness to reduce to half is small, meaning the HVL is thin. Dense tissues like bone have a high μ for X-rays, so only a small amount of material is needed to halve the beam, giving a thin HVL. If a tissue attenuates less (lower μ), a thicker layer would be required, yielding a thicker HVL.

Half-value layer is the thickness of material needed to cut the beam’s intensity in half. The attenuation follows I = I0 e^{-μx}, so the thickness that halves the beam is x1/2 = ln(2)/μ. When the attenuation coefficient μ is large, the required thickness to reduce to half is small, meaning the HVL is thin. Dense tissues like bone have a high μ for X-rays, so only a small amount of material is needed to halve the beam, giving a thin HVL. If a tissue attenuates less (lower μ), a thicker layer would be required, yielding a thicker HVL.