Question

How many CT numbers are assigned to each pixel in the image matrix?

a. One half the number of all values recorded from the array detector
b. One
c. Two values for a 256-matrix, 4 values for a 512-matrix
d. The number of HU per pixel is one-tenth the display field of view

Answer 1

Each pixel in a CT image matrix is assigned just one CT number, which is equivalent to one Hounsfield Unit (HU), regardless of the matrix size and not related to the display field of view.

Step-by-step explanation:

In computed tomography (CT) imaging, the CT number is a value that quantifies the radiodensity of tissues in a cross-sectional image of the body. Each pixel in the image matrix on a CT scan is assigned one CT number, which is also commonly referred to as a Hounsfield Unit (HU). The CT number represents the relative density of the tissue compared to a reference value, which is typically the radiodensity of water. A 256x256 matrix and a 512x512 matrix both will have one CT number (or HU) per pixel, not varying by the size of the matrix. The statement that the number of HU per pixel is one-tenth the display field of view is incorrect, as HU values are not scaled in this manner.