Back projection is a mathematical procedure used to reconstruct CT images. Back Projection is based on the blurring of the x-rays within a projection back along the direction in which they were measured.

Natural background radiation originates from radioactive elements in the environment, including food, water, soil and rock (also building materials), the atmosphere and cosmic rays. The level of natural exposure to radiation can vary greatly between different locations. In the US, the average annual exposure from natural sources to humans is about 3 mSv (millisievert) corresponding to 0.3 rem. Radon gas accounts for two-thirds of this exposure.
Background radiation may also interfere with measurements. Background radiation includes radioactive contamination of samples or incomplete absorption of radiation in a detector.

Banding is a set of functions performed by placing and dragging the mouse pointer on an image. For example, the zooming of images by placing the mouse pointer on an image, pressing and holding the mouse button, dragging a box around the area of interest, and releasing the mouse button to zoom. Other banding operations include panning and zooming.

A barcode is an information code with a linear sequence of machine-readable elements. The elements are made up of rectangular black bars and white spaces between the bars. In document imaging, barcodes are typically used to encode index data and/or separate documents.

A barium enema is an x-ray examination of the colon and rectum to find abnormalities such as polyps, diverticulosis, cancer, or inflammatory disease.
Liquid barium is administered through a small tube inserted into the rectum. In case of an air-contrast or double-contrast barium enema, the added air improves the evaluation of the lining of the large intestine.
Barium enemas require a bowel preparation with laxatives, starting one day before the examination.

See also Colonoscopy and Virtual Colonoscopy.