# Radiology Glossary Terms

## The following is a short list of some common radiology terms.

##### Non-ionizing radiation:

Any electromagnetic radiation that is unable to scavenge electrons from atoms or molecules to produce direct or indirect ions or ionized molecules.

##### Far Field area:

It is called the area of the field of an antenna where the angular field distribution is substantially independent of the distance from the antenna. In this region, the field has a predominant flat wave character, ie with uniform local distributions of electric and magnetic field intensity at levels transverse to the direction of propagation.

##### Near Feld area:

This area is generally close to an antenna, or other radiant structure, where the angular field distribution depends on the distance from the antenna. In this region, electric and magnetic fields have no flat wave character. The near field field is further subdivided into the reactive near field field, which is closest to the radiant structure and contains most or almost all of the stored energy, and the near field field where the radiation field predominates over the reactive field but has no real-level wave character and is complex in structure.

##### Power flux density (S):

This is the radiant power that strikes perpendicular to a surface, divided by the area of the surface, and is expressed in watts per square meter (W / m2). For flat waves, the power flux density S, the active value of the electric field strength and the active value of the magnetic field strength H are related to the free space impedance (377Ω) with the following relation: S = E2 / 377 = 377H2 .

##### Current density (J):

Defined as the current flowing through a unit cross section of a three-dimensional conductor, such as the human body, perpendicular to its direction and expressed in apex per square meter (A / m2).

##### Electric field strength (E):

It is the vector quantity corresponding to the force exerted on a charged particle, regardless of its motion in space. It is expressed in volts per meter (V / m).

##### Magnetic field strength (H):

It is a vector quantity (H), which, in combination with the magnetic flux density, defines a magnetic field at any point in space. It is expressed in apex per meter (A / m).

##### Magnetic flux density (B):

It is a vector quantity (B), on which the force exerted on moving loads depends; it is expressed in tesla (T). In vacuum and in biological materials, the magnetic flux density can be converted to magnetic field strength and vice versa, based on the formula 1 A m-1 = 4π10-7 T. In the literature, the magnetic flux density is also found as magnetic induction.

##### Specific Energy Absorption (SA):

Defined as the energy absorbed per unit mass of biological tissue expressed in joules per kilogram (J / Kg).

##### Specific Absorption Rate (SAR):

SAR is the power absorbed per kilogram of mass (W / Kg). For whole body exposure, SAR may be averaged over localized areas of the body, e.g. the head or limbs. The basic exposure limits are usually expressed in SAR terms. (e.g. check the list with the **SAR values of recent / popular mobile phones** models)

##### Multi-source exposure factor:

Used when considering exposure to many different electromagnetic sources with frequencies greater than 1MHz. Multi-source Exposure Factor is defined as the sum of the ratios of the measured power flux density at each frequency to the value of the reference level for that frequency. If smaller than the unit indicates compliance with the exposure instructions.

##### Individual source exposure factor:

Individual Source Exposure Factor is defined as the ratio of the measured power flux density at a frequency to the value of the reference level for that frequency. If less than the unit indicates compliance with the exposure instructions at this frequency.

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