(P) The electric polarization refers to the separation of charges in a material to form electric dipoles, or the alignment of existing electric dipoles in matter when an electric field is applied. The unit of electric polarization is dipole moment per cubic meter or coulomb per square meter(C/m²).

Grids are used in a test phantom to check the quality of x-ray images. Such a grid may consist for example, of gold structures on a silicon surface and a grid period length of 2 micrometer with space wide in between of 1 micrometer.
Filter grids are also used in x-ray imaging to reduce noise contributed by scatter.

Magnetic flux density is the amount of magnetic flux per unit area of a section, perpendicular to the direction of flux. The magnetic flux density is the product of the magnetic field strength and permeability. The SI unit for flux density is weber per square meter. One weber per square meter equals one tesla (T).

The pitch factor is a selectable CT parameter. The definition depending on the IEC standards is the ratio of the table speed per rotation and the total collimation.
The choice of pitch factor is determined on practical considerations and on the availability of the computed tomography algorithms and parameters for image reconstruction.

See Pitch.

A pixel is a picture element (pix, abbreviation of pictures + element). Tomographic images are composed of several pixels; the pixel size is determined by the used field of view and the number of elements in the display image matrix. The corresponding size of the pixel may be smaller than the actual spatial resolution.
Pixels do not have a fixed size; their diameters are generally measured in micrometers (microns). Although the pixel is not a unit of measurement itself, pixels are often used to measure the resolution (or sharpness) of images. As a hypothetical example, a 600 x 1000 pixel image has 4 times the pixel density and is thus 4 times sharper than a 300 x 500 pixel image, assuming the two images have the same physical size.