What does the term "Hounsfield unit" measure in CT imaging?

The term "Hounsfield unit" is a specific measure used in computed tomography (CT) imaging to quantify the radiodensity of tissues. Hounsfield units (HU) provide a standardized way to compare the attenuation of X-rays by different types of tissues in the body. This unit system is critical because it enables radiologists to distinguish between various types of tissue based on their density. For example, air has a HU value of -1000, water is defined as 0 HU, and denser tissues like bone can have values greater than +300 HU.

Using Hounsfield units allows for a more precise interpretation of CT scans, as different tissues absorb X-rays to varying extents. This measurement helps in identifying abnormalities, evaluating pathology, or even determining the composition of a mass based on its density relative to surrounding structures. Because of this significance in assessing tissue characteristics, Hounsfield units are fundamental to the function and utility of CT imaging in medical diagnostics.