RD3.1-4 | Radiation Safety and Legal Requirements — Glossary

The amendment that broadened the PNDT Act to cover pre-CONCEPTION sex-selection techniques (e.g. sperm sorting) and strengthened regulation, renaming it the PC-PNDT Act.

The physical energy deposited per unit mass of tissue (joules/kg); its unit is the Gray (Gy). It is purely physical and carries no information about biological risk.

The committee constituted under the PC-PNDT Act to advise and assist the Appropriate Authority in performing its functions.

India's statutory radiation safety regulator, constituted in 1983 under the Atomic Energy Act 1962; it licenses and registers X-ray and CT installations, sets safety codes and dose reference levels, and enforces compliance.

As Low As Reasonably Achievable — the optimisation principle requiring that, once an exposure is justified, the dose be kept to the lowest level reasonably achievable, accounting for economic and social factors.

A prenatal diagnostic technique sampling amniotic fluid (typically from ~15 weeks) for foetal karyotyping and genetic/biochemical analysis — a permitted use under the Act.

The official (district/state level) empowered under the PC-PNDT Act to register and inspect facilities, seize records and equipment, and initiate prosecution for violations.

The Indian statute under which the AERB derives its authority to regulate radiation sources, including medical diagnostic X-ray and CT equipment.

Naturally occurring radiation (cosmic, terrestrial, radon, internal) to which everyone is exposed — roughly 2–3 mSv per year — used as a reference for comparing examination doses.

The induction of cancer by a somatic-cell mutation; the dominant stochastic risk of diagnostic radiation, with no assumed threshold and long latency.

The number of girls per 1000 boys in the 0–6 year age group; its decline in successive Indian censuses is the demographic evidence of sex selection that the PC-PNDT Act aims to reverse.

A prenatal diagnostic technique sampling placental tissue (typically 10–13 weeks) to detect chromosomal and genetic disorders — a permitted use under the Act.

Restricting the X-ray beam to the area of clinical interest; a key optimisation technique that reduces patient dose and improves image quality.

A radiation effect that occurs only above a threshold dose and whose severity rises with dose; includes skin erythema, epilation, cataract, sterility and acute radiation syndrome.

DNA damage caused when radiation (or a secondary electron) deposits energy directly in the DNA molecule, breaking a strand.

The principle that regulatory dose limits are set for occupational workers and the public and must not be exceeded; it does NOT apply to a patient's own diagnostic exposure.

A benchmark dose for a standard diagnostic procedure set by the AERB; facilities routinely exceeding it must review and reduce their practice.

Equivalent dose further weighted by tissue radiosensitivity and summed over the body; the Sievert (Sv) quantity (usually mSv) used to compare the stochastic risk of different examinations.

The AERB's online portal (e-Licensing of Radiation Applications) through which diagnostic X-ray and CT installations are registered and licensed in India.

Absorbed dose weighted by a radiation weighting factor for the biological damaging power of the radiation type; unit Sievert (Sv).

An older personal dosimeter in which a photographic film darkens in proportion to absorbed dose, with filters allowing radiation type/energy to be inferred; single-use, gives a permanent record.

The mandatory PC-PNDT record completed for every pregnant woman undergoing a prenatal diagnostic procedure, documenting her particulars, the clinical indication, and a signed declaration that foetal sex was not detected or disclosed.

A highly reactive molecule with an unpaired electron (e.g. ·OH) produced by water radiolysis, which chemically attacks DNA in indirect radiation damage.

The SI unit of absorbed dose, equal to one joule of energy absorbed per kilogram of tissue.

The International Commission on Radiological Protection — an international advisory body that recommends radiation-protection principles and dose limits but has no regulatory authority in India.

DNA damage caused when radiation ionises water (radiolysis), generating free radicals (e.g. the hydroxyl radical) that then damage DNA; the predominant route for diagnostic X-/gamma rays.

Radiation intensity from a point source falls in proportion to the square of the distance (I ∝ 1/d²); doubling distance reduces dose to one-quarter — the physical basis of distance as a protection tool.

Radiation carrying enough energy per photon or particle to eject an electron from an atom (ionise it), and therefore to damage DNA; in imaging, X-rays and gamma rays.

The radiation-protection principle that no exposure should be authorised unless it does more good than harm — the diagnostic benefit must outweigh the radiation detriment.

A measure of a shielding material's X-ray attenuation expressed as the thickness of lead giving the same protection; aprons are typically 0.25–0.5 mm lead equivalent.

The radiation-protection assumption that stochastic risk is directly proportional to dose with no safe lower threshold, derived largely from atomic-bomb survivor data.

Radiation without enough energy to ionise atoms, so it cannot directly break DNA; in imaging, the sound waves of ultrasound and the radiofrequency/magnetic fields of MRI.

The maximum permitted effective dose for a radiation worker — 20 mSv per year averaged over five years (with no single year exceeding 50 mSv) under ICRP/AERB.

A modern personal dosimeter read out by laser light rather than heat; an increasingly used alternative to the TLD.

The radiation-protection principle (operationalised as ALARA) of keeping justified exposures as low as reasonably achievable; applies to both patients and workers.

The Pre-Conception and Pre-Natal Diagnostic Techniques (Prohibition of Sex Selection) Act — Indian law (enacted 1994, in force 1996, amended 2003) that prohibits sex selection and the misuse of prenatal diagnostic techniques for foetal sex determination.

Use of prenatal diagnostic techniques to detect chromosomal abnormalities, genetic/metabolic disorders, congenital anomalies and certain sex-linked disorders — legitimate medical purposes allowed under the Act.

The original Pre-Natal Diagnostic Techniques Act of 1994, renamed PC-PNDT after the 2003 amendment added pre-conception sex-selection techniques to its scope.

A direct-reading personal dosimeter giving an immediate display of accumulated dose, useful for real-time checks but less precise for the legal cumulative record.

Procedures such as ultrasound, amniocentesis, chorionic villus sampling and foetal blood/genetic testing used to examine the foetus; permitted for detecting disease but not for sex selection.

The maximum permitted effective dose for a member of the public from controlled radiation practices — 1 mSv per year.

Fluoroscopy delivered as brief pulses rather than a continuous beam, reducing screening dose — a 'time' optimisation technique.

A designated, qualified person responsible for radiation safety, monitoring and AERB compliance within a diagnostic radiology installation.

The compulsory registration with the Appropriate Authority that every genetic counselling centre, genetic laboratory, genetic clinic and ultrasound/imaging clinic using prenatal diagnostic techniques must obtain before operating.

Determining or communicating the sex of a foetus by any means; the PC-PNDT Act makes such determination and disclosure a criminal offence regardless of intent.

Any procedure, technique or administration intended to ensure or increase the likelihood of a child of a chosen sex, whether applied before conception or prenatally — prohibited by the Act.

A heritable disorder linked to the sex chromosomes (e.g. haemophilia, Duchenne muscular dystrophy) where foetal sex may be medically relevant — managed under strict documented conditions, never for selection.

The SI unit of equivalent and effective dose — a biologically weighted measure of radiation risk; diagnostic doses are quoted in millisieverts (mSv).

The notice that registered facilities must prominently display stating that determination/disclosure of foetal sex is prohibited by law and not done at the centre.

A radiation effect with NO threshold dose whose probability (not severity) rises with dose; comprises carcinogenesis and hereditary effects, typically with long latency.

The principal personal radiation monitor: a crystal (e.g. lithium fluoride) that stores energy when irradiated and releases it as light proportional to accumulated dose when heated in a reader.

A lead-equivalent collar worn to protect the radiosensitive thyroid gland during fluoroscopy and interventional procedures.