A zoom reconstruction is the enlarged reconstruction of a part of an image. A zoom reconstruction uses the raw data of a scan. Zooming or targeting requires the operator to manipulate the displayed field of view.

Usually, magnification is the enlargement of an area by interpolation after the reconstruction of an image. Magnification does not provide more information, but allows a better view of certain object details. A zoom reconstruction is based on the raw data of the scan. Magnification software enlarges an image by mapping one pixel onto an n x n array of screen pixels (pixel stretching).
Other types of magnification include electron-optical, geometric, the product of geometric and the electron-optical magnification and enlargement by imaging procedures.
Electron-optical magnification is the ratio of the dimension of the detector input image and the size of the image on the screen. This ratio is determined by all electronic and optical imaging processes of the image chain, provided that one camera pixel is mapped onto accurately one monitor pixel.
Geometric magnification occurs in x-ray images when the focal spot is theoretically assumed to be a point and not an area. For nanofocus and microfocus radiographic systems, the focus-to-detector (film) distance and the focus-to-object (film) distance defines the geometric magnification.
The total magnification is the product of the electron-optical and geometric magnification. Possible magnifications are up to a factor of 26,000.
Magnification procedures in medical imaging are usually produced by extended distance between the subject and the image receptor.

Raw data are the values of all measured detector signals during a scan. After calibration for fluctuations in tube output and beam hardening, the attenuation properties of each x-ray signal are accounted and correlated with the ray position. From these data the CT images are reconstructed including the use of mathematical procedures like convolution filtering and back projection.
Raw data can also be used for later reconstruction of additional planes and images by using a different convolution filter, zoom reconstruction, or an alternative CT number scale.

See also Magnification, Archiving, Number of Measurements and Convolution.

Reconstruction is the mathematical process by which the displayed image is produced from the raw data.
Used equipment and data processing methods to reconstruct CT images:
See also Zoom Reconstruction, Reconstruction Matrix and Multiplanar Reconstruction.

Zooming increases scale factors of images within a window. Zooming takes a selected region and extends it over the entire matrix of the displayed CT image. Usually, a zoom reconstruction increases the accuracy of the CT numbers by decreasing the overall size of the displayed image pixels, which decreases the possibility of many tissues occupying a single pixel (partial volume averaging).
Zooming or targeting is not the same as image magnification.

See also Banding.