What computed tomography (CT) pixel intensities become white when using a 400 window width and 30 window level?

In computed tomography, the display of pixel intensities as white or black is determined by the window width and window level settings. The window width defines the range of CT numbers (or Hounsfield units) that will be displayed, while the window level sets the center point of that range.

With a window width of 400 and a window level of 30, the algorithm calculates that pixels with CT numbers above the window level plus half the window width will appear white. In this case, the window level is 30, and half the window width is 200 (which is half of 400). Therefore:

• The threshold for pixel intensities to appear white is calculated as follows:

• Level + (Width/2) = 30 + 200 = 230.

This means pixel intensities that have CT numbers above 230 will be displayed as white on the CT images. Thus, the correct identification of CT numbers that turn white under these window settings is those above 230.