Ionizing radiation
Radiation with enough energy to ionize matter. X-rays and gamma rays are ionizing electromagnetic (photon) radiation; radio-frequency interference is a different protection problem.
X-ray
High-energy photon radiation produced by electron processes, such as electrons striking the target of an X-ray tube. Its spectrum depends on tube voltage and filtration.
Gamma ray
Photon radiation usually emitted by nuclear transitions; its energy is set by the radionuclide. Shielding is selected for the actual spectrum and source geometry, not the name.
Alpha and beta particles
An alpha particle contains two protons and two neutrons; beta radiation consists of electrons or positrons. X-ray product ratings do not prove protection against particle fields.
Lead equivalence (mmPb)
The thickness of lead that gives the same attenuation under specified test conditions. It is not the material’s thickness, weight or lead content, and should be quoted with radiation quality, method and geometry.
How lead equivalence is determined
- Same radiation quality (tube voltage, filtration) and the same measurement geometry for both paths.
- The material sample under test.
- A lead reference whose thickness d is adjusted.
- Transmission is measured at the same detector position.
- When transmission matches, the material’s lead equivalence is d mmPb. It is not the material’s own thickness, weight or lead content.
See also: mmLE
mmLE
A lead-equivalent notation used in some catalogs, expressing the same concept as mmPb. Confirm beam quality and finished-product testing before treating grades as interchangeable.
See also: Lead equivalence (mmPb)
Tube voltage (kV, kVp)
The accelerating voltage of an X-ray tube, which shapes the spectrum; kVp denotes the peak value. It is an equipment setting — the photons do not all share one energy.
Tube current (mA)
Relates to the electron flow and X-ray output. Filtration, exposure time and other settings also matter; no single value defines a protection requirement.
Radiation quality
The spectral character of a beam, defined by conditions such as tube voltage and filtration. Standard reference qualities, for example the N series in GB/T 12162.1, make tests comparable.
Narrow beam and broad beam
Measurement geometries that change how much scattered radiation reaches the detector. Narrow, broad and inverse broad beam results should not be mixed; a narrow beam does not mean a narrow spectrum.
Narrow beam and broad beam
- Narrow beam: collimators restrict the beam before and after the sample.
- Most radiation scattered by the sample never reaches the small detector.
- Broad beam: a wide field and a large detector close to the sample.
- Part of the scatter is counted, so broad-beam results differ from narrow-beam results. Do not mix them when comparing materials.
Areal density (kg/m²)
Mass per unit area. For the same coverage, core mass equals areal density times area; compare it only at the same verified protection level and test condition.
Attenuation
The reduction in radiation intensity after passing through a material, often expressed as a percentage. The value depends on radiation quality, geometry and the sample tested.
Half-value layer (HVL)
The thickness of a material that reduces the beam intensity to one half. It changes with the spectrum and geometry, and is also used to characterize radiation quality.
Photoelectric absorption
An interaction in which a photon is absorbed and an electron is released. It is important at lower photon energies and in high-atomic-number elements.
Compton scattering
A photon collides with an electron and changes energy and direction. It is a main source of scattered radiation.
Absorption edge
A sharp rise in absorption when photon energy just exceeds an electron-shell binding energy. Edges make material response energy-dependent, which lets multi-element formulations target a spectrum.
Characteristic X-ray fluorescence
Secondary X-rays emitted as an atom relaxes after absorbing a photon. In the bilayer described by Newlife, the body-side bismuth layer absorbs fluorescence from the front rare-earth layer.
Pair production
Creation of an electron–positron pair in a nuclear field, with a 1.022 MeV threshold. It is not a shielding mechanism at 120 kVp diagnostic conditions.
Scatter radiation
Radiation redirected by interaction with the patient, equipment or surroundings. Drapes, collars and similar products are selected for the scatter geometry of the procedure.
Lead-free shielding material
A material that does not use lead as its shielding component. “Lead-free” describes composition only; it does not mean every substance is harmless, that all regulations are met, or that it suits every radiation source.
Lead acrylic
A transparent acrylic that contains lead, used where viewing and shielding are both needed. It is a lead-containing product.
IEC 61331-1
The international standard for determining the attenuation properties of materials for protective devices against diagnostic medical X-radiation (2014 edition). Naming the standard is not the same as certification.
Source notes
Definitions are based on Newlife’s radiation protection FAQ, the lead-free shielding presentation and the public references below. Reviewed 2026-09-24. Consult model literature for product values.
IAEA — Radiation basics · IEC 61331-1:2014 · NIST XCOM
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