The gantry tilt is the angle between the vertical plane, and the plane containing the x-ray beam and the detector array. The gantry angulation allows aligning the selected anatomic region with the scanning plane.
A CT gantry can typically be angled up to 30° forward or backward. However, the gantry angulation is determined by the manufacturer and varies among CT systems. In a series of CT scans made with a tilted gantry the anatomy shifts in location from scan to scan.

Radiation can ionize matter caused by the high energy which displaces electrons during interactions with atoms. In the electromagnetic spectrum higher frequency ultraviolet radiation begins to have enough energy to ionize matter.
Examples of ionizing radiation include alpha particles, beta particles, gamma rays, x-rays, neutrons, high-speed electrons, high-speed protons, and other particles capable of producing ions by direct or secondary processes in passage through tissues.
Damage of living tissue results from the transfer of energy to atoms and molecules in the cellular structure. Ionized cells have to repair themselves to remain alive. Generally, healthy cells have a higher capability to repair themselves than cancer cells.

Biological effects of ionizing radiation exposure:
Ionizing radiation are used in a wide range of facilities, including health care, research institutions, nuclear reactors and their support facilities, and other manufacturing settings. These radiation sources can pose a serious hazard to affected people and environment if not properly controlled.

See also Radiation Safety, Controlled Area, Radiotoxicity and As Low As Reasonably Achievable.

Isobars are atoms with equal mass number but different atomic number.

The mass number is the total number of protons and neutrons (also total nucleon) in the nucleus.

See also Atomic Mass Unit, Atomic Mass.

A molecule is a structure formed of atoms of various elements. It is the smallest concentration of same or different atoms that all chemical characteristics retain.

See also Free Radicals, Osmole, Enzyme Linked lmmuno Sorbent Assay, Gas Chromatography and Gel Chromatography.