What determines the number of Hounsfield Units (HU) assigned to each level of gray in a CT image?

The number of Hounsfield Units (HU) assigned to each level of gray in a CT image is determined by the window width settings. The Hounsfield scale quantifies radiodensity and is used to differentiate tissue types in a CT scan. The window width refers to the range of HU values that is displayed within the grayscale of the image.

A narrower window width will enhance subtle differences in similar tissues, allowing for better contrast in that specific range, whereas a wider window width will include a broader range of HU values, resulting in a flatter image. Essentially, the window width helps to set the sensitivity of the imaging system to variations in tissue density, thereby influencing how different tissues appear on the final scan.

While factors like image visualization techniques and detector sensitivity do play a role in overall image quality, they do not directly affect the assignment of Hounsfield Units. Patient demographic data is also unrelated to the specific assignment of HU values, focusing more on patient history and clinical context rather than the technical aspects of the CT imaging process itself.