Hounsfield scale

Hounsfield Scale

A CT scan image demonstrating variations in radiodensity measured by the Hounsfield scale.

The Hounsfield scale, named after Sir Godfrey Hounsfield, is a quantitative scale that is essential in the field of computed tomography (CT) imaging for describing the radiodensity of various tissues. The scale assigns a specific numerical value, known as a CT number, to different levels of radiodensity, allowing for the clear differentiation of tissues in CT scans.

Background

Developed in conjunction with the invention of the CT scanner by Sir Godfrey Hounsfield, the Hounsfield scale revolutionized diagnostic imaging by providing a precise method to quantify tissue densities. This innovation has been fundamental in the advancement of medical imaging and diagnosis.

Scale Values

The Hounsfield scale is measured in units (HU), with distilled water at standard pressure and temperature (STP) set at zero HU. The scale ranges from -1000 HU (air) to approximately +3000 HU (dense bone), with various tissues falling at specific points within this range:

• Air: -1000 HU
• Fat: -100 to -50 HU
• Water: 0 HU
• White matter: +20 to +30 HU
• Grey matter: +37 to +45 HU
• Liver: +40 to +60 HU
• Dense bone: +700 to +3000 HU

Clinical Applications

The Hounsfield scale is instrumental in distinguishing between different types of body tissues in CT scans due to its sensitivity to variations in radiodensity. This capability is crucial for:

• Identifying tumors, cysts, and other lesions
• Detecting hemorrhages and calcifications
• Guiding radiological interventions
• Assessing bone mineral density

Limitations

While the Hounsfield scale is a powerful tool in CT imaging, it has limitations, including:

• Variability in HU readings due to scanner calibration
• Overlap in density ranges for certain tissues, potentially complicating interpretation

See Also

• Computed tomography (CT) scan
• Radiodensity
• Diagnostic imaging
• Sir Godfrey Hounsfield

External Links

• Radiopaedia - Hounsfield Unit
• National Center for Biotechnology Information - The Hounsfield Unit

This article is a medical stub. You can help WikiMD by expanding it!
Most recent articles Ongoing trials	Wikipedia