What is the Hounsfield Unit (HU) range for lung tissue?

The range of Hounsfield Units (HU) for lung tissue is typically about -500 to -900 HU. This measurement reflects the low density of air-filled lung tissue compared to surrounding structures. The negative values indicate that lung tissue is less dense than water, which is defined as 0 HU.

In imaging, structures that have lower attenuation than water will yield negative HU values. Lung tissue, being primarily composed of air, naturally falls on this negative side of the scale, making option A the correct representation of the typical HU range for normal lung tissue. This range is essential for differentiating lung pathology during CT scans, as it allows radiologists to recognize abnormalities in lung density, such as fluid accumulation or tumors, which will appear with higher attenuation values (closer to or above 0 HU).

Other ranges provided in the options do not accurately represent lung tissue's typical HU values. Positive values would suggest denser tissues, while the mid-range negative values are not reflective of healthy lung tissue as understood in radiology practice.