Question

CT number ____________ would appear black if a window width of 400 and a window level of -100 are used.

Answer 1

A CT number lower than -300 Hounsfield units (HU) would appear black on a CT image with a window width of 400 and a window level of -100.

Step-by-step explanation:

In Computed Tomography (CT), the CT number is a measure of the radiodensity of a particular tissue compared to a reference substance, typically water, and is expressed in Hounsfield units (HU). The window width and window level are controls used to adjust the brightness and contrast of the CT images.

When a window width of 400 and a window level of -100 are used, any CT number less than the lower boundary of this range would appear black on the image. To determine the lower boundary, you subtract half of the window width from the window level: -100 - (400/2) = -300. Therefore, a CT number lower than -300 HU would appear black on this CT image.