Opportunistic screening for osteoporosis using abdominal computed tomography scans obtained for other indications. Computed tomography scans in the evaluation of fatty liver disease in a population based study: the multi-ethnic study of atherosclerosis. Hounsfield units are named after Sir Godfrey Hounsfield, the Nobel prize winner and inventor of CT. No equivalent to Hounsfield units exists in any other form of structural imaging. Other less common uses include assessing bone mineral density (BMD) 3, predicting the presence of anaemia 4, and guiding the management of kidney stones 5. One well-known use is the evaluation of the fat content of the liver, with fatty liver diagnosed by the presence of a liver-to-spleen ratio <1.0 or 0.8 2. Hounsfield units are measured and reported in a variety of clinical applications.
HOUNSFIELD UNITS CT IMAGECAST SOFTWARE
The software of all CT scanners and PACSs has the ability to measure the density of a region of interest (ROI) electronically overlaid the image. How these values are displayed is then determined by the application of specific window and level values. Generally, CT images, therefore, use 12-bit images able to store values between −1024 to 3071 7. This results in a scale running from -1000 HU for air to +~2000 HU for very dense bone ( cochlea) and over 3000 for metals 7. Note: STP = standard temperature is 0 ☌ and pressure is 10 5 pascals (i.e. radiodensity of distilled water at standard temperature and pressure (STP) = 0 HU.This transformation (figure 1) is based on the arbitrarily-assigned densities of air and pure water: Hounsfield units are obtained from a linear transformation of the measured attenuation coefficients 1. Hounsfield units (HU) are a dimensionless unit universally used in computed tomography (CT) scanning to express CT numbers in a standardised and convenient form.
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