Hounsfield units (HU)

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Indications

Procedure

  • obtained from a linear transformation of the measured CT attenuation coefficients
  • radiodensity of distilled water at standard temperature & pressure = 0 HU
  • radiodensity of air at standard temperature & pressure = -1000 HU
  • a change of 1 HU represents a change of 0.1% of the attenuation coefficient of water

Interpretation

  • lesions > 20 HU on non-contrast CT images are considered hyperdense
  • an increase > 15 HU between precontrast & postcontrast CT imaging is considered enhancement.

Notes

More general terms

References

  1. Thomas S, Grimm L, Brady MP Renal Cell Carcinoma: Recognition and Follow-up. Medscape. April 18, 2016 http://reference.medscape.com/features/slideshow/renal-cell-carcinoma
  2. 2.0 2.1 Weerakkody Y, Greenway K et al Hounsfield unit https://radiopaedia.org/articles/hounsfield-unit
  3. 3.0 3.1 Wikipedia: Hounsfield scale https://en.wikipedia.org/wiki/Hounsfield_scale