The primary radiation is the useful beam emitted from the x-ray source.

Scattered radiation is caused by interaction of the primary radiation with matter. The interaction with matter could cause a change in direction (scattering) and a reduction in energy.
From a radiation protection point of view, scattered radiation is assumed to come primarily from interactions of primary radiation with tissues of the patient.

Filter grids are used to reduce scattered noise and increase contrast in x-ray images. Primary radiation passing through an object gets scattered caused by the various density of different materials. Scatter radiation produces noise (radiographic fog) on the film or detector, which degrades the diagnostic quality. Anti-scatter grids act as filters between patient and film (or receiver) to remove scatter radiation. The use of a grid is recommended with body parts thicker than 10 cm and kVp values about 60 kV.
X-ray filter grids are available with focused or parallel strips. These two types are produced with linear or crossed grid configurations. The septa of filter grids consist of high radiation absorbing materials (e.g. lead) separated by permeable parts. During radiation exposure, movement of the grid blurs a projection of the septa.
If the image receptor and x-ray tube (with the focal spot) are in a fixed position relative to one another the grid is automatically aligned. In mobile radiography, the position of the focal spot and the image receptor is variable. Additionally cassettes incorporating anti-scatter grids are also available.

Radiation shielding is the process of limiting the penetration of radiation into the environment, by blocking with a barrier made of impermeable material. This protective barrier is usually formed of a material with high density, for example lead that absorbs the radiation.
Radiation sources are self-shielded with absorbing material incorporated into the equipment, adjacent to the source to reduce stray radiation to the surrounding area below dose limits.
Rooms with x-ray or other radiation equipment are additionally shielded with lead-lined walls to reduce the radiation exposure to humans within the facility. The amount of shielding required to protect against different kinds of radiation depends on how much energy they have. The shielding calculations are based on the half value layer of the primary radiation beam. Sufficient half value layers of shielding are calculated to reduce the radiation exposure outside the room to reasonable levels.
Personal shielding requirements depending on the type of radiation:
See also Radiation Safety.

Air KERMA (Kinetic Energy Released per unit MAss of air) measures the amount of radiation energy in air, unit is J/kg. This include the initial kinetic energy of the primary ionizing particles such as photoelectrons, Compton electrons, positron//negatron pairs from photon radiation, and scattered nuclei from fast neutrons, when for example air is irradiated by an x-ray beam. J/kg (gray) is also the unit of the radiation quantity 'Absorbed Dose'.