The HU value (Hounsfield Unit value) is a measure used in CT (Computed Tomography) imaging to describe the radiodensity of a tissue or material. It helps in identifying and differentiating different types of tissues based on how much they attenuate (block) X-rays.
🔹 HU Value Scale:
The HU scale is based on the density of water, which is defined as 0 HU, and air, which is -1000 HU.
| Material | Approx. HU Value |
|---|---|
| Air | -1000 |
| Lung | -700 to -900 |
| Fat | -100 to -50 |
| Water | 0 |
| Soft tissue (muscle, liver) | +40 to +80 |
| Blood | +30 to +45 |
| Bone (cancellous) | +200 to +300 |
| Bone (cortical) | +700 to +3000 |
| Metal (implants, contrast) | > +1000 |
🔸 Why is HU Important?
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Diagnosis: Helps differentiate between cysts, tumors, hemorrhages, etc.
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Quantification: E.g., in measuring lung density in COPD or fat in the liver.
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Planning: Used in radiotherapy planning and surgical navigation.
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