The gantry aperture is the opening through which the table with the patient moves for the examination. Typical diameters of the gantry range from 50 to 85 cm. The gantry aperture diameters between 70 and 85 cm are useful for biopsy procedures and obese patients. Larger gantry apertures allow for easier handling of the biopsy equipment.
The scanning field of view in which the CT data are acquired is smaller than the gantry aperture diameter.

The gantry is a ring-shaped structure, containing the x-ray tube, collimators, filters, data acquisition system (DAS), associated electronics such as gantry angulation motors, rotational components including slip ring systems and the detector array in a CT or radiation therapy system. The table control, to regulate the gantry tilt and laser (or high intensity) lights are included within, or mounted on the gantry serving as anatomical positioning guides. To scan the patient, the patient table is moved through the gantry aperture.
The rotating arm on which an accelerator head is mounted is also called gantry. This gantry can rotate 360 degrees around its axis.