ABSNM RP flashcards
ABSNM RP · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Half-value layer
- The thickness of material that reduces the intensity of a photon beam to one half of its original value; numerically HVL = ln2/μ ≈ 0.693/μ.
- Inverse-square law
- For a point source, dose rate or exposure rate varies inversely with the square of the distance, so doubling distance reduces the rate to one quarter.
- Photoelectric effect
- A photon transfers all its energy to a bound electron, which is ejected; dominant at low photon energies and strongly dependent on atomic number.
- Compton scattering
- A photon scatters from an electron, transferring part of its energy; dominant at intermediate energies and dependent on electron density of the material.
- Pair production
- A photon with energy at least 1.022 MeV converts into an electron-positron pair in the field of a nucleus; dominant at high energies in high-Z materials.
- Bremsstrahlung
- Radiation produced when a charged particle, usually a beta particle, is decelerated in the electric field of a nucleus; more probable in high-Z absorbers.
- GM counter plateau
- The voltage region of a Geiger-Mueller detector where count rate is nearly independent of applied voltage and pulse height does not indicate deposited energy.
- Dead-time correction
- Correction applied to observed count rates to account for detector resolving time: true rate equals observed rate divided by one minus observed rate times dead time.
- HPGe spectrometry
- Gamma spectrometry using a high-purity germanium detector, which provides high energy resolution for identifying radionuclides but requires cryogenic cooling.
- Ionization chamber
- A gas-filled detector operated in the ionization region where collected charge is proportional to the radiation-induced ionization, used for exposure and dose-rate measurement.
- Liquid scintillation counting
- A detection method in which the sample is mixed with a scintillant, allowing measurement of low-energy beta emitters such as tritium and carbon-14.
- Absorbed dose
- The mean energy imparted by ionizing radiation to a unit mass of matter; the SI unit is the gray, equal to one joule per kilogram.
- Equivalent dose
- The absorbed dose averaged over a tissue or organ multiplied by the radiation weighting factor for the type and energy of radiation; unit sievert.
- Effective dose
- The sum over tissues of equivalent dose multiplied by tissue weighting factor; represents whole-body stochastic risk and is expressed in sieverts.
- Committed effective dose
- The effective dose accumulated over 50 years after intake of a radionuclide, accounting for uptake, retention, and radioactive decay in the body.
- Gray and rad
- The gray is the SI unit of absorbed dose equal to one joule per kilogram; one gray equals 100 rad.
- Deterministic effect
- A tissue reaction that has a threshold dose and whose severity increases with dose, such as erythema, cataract, or acute radiation syndrome.
- Stochastic effect
- A probabilistic effect, such as cancer or heritable mutation, assumed to have no threshold under the linear no-threshold model, with probability increasing with dose.
- Acute radiation syndrome
- A set of clinical syndromes following high whole-body acute exposure, including hematopoietic, gastrointestinal, and cerebrovascular forms, with severity dependent on dose.
- LD50/60
- The whole-body acute dose that would be lethal to 50 percent of an exposed population within 60 days without medical support; approximately 3.5 to 4.5 gray.
- Radiosensitivity
- The relative susceptibility of cells or tissues to radiation damage, highest in rapidly dividing cells such as bone marrow, intestinal epithelium, and gonads.
- ALARA principle
- The principle that radiation doses should be kept as low as reasonably achievable, taking economic and social factors into account.
- Time distance shielding
- The three basic external-dose control measures: minimize exposure time, maximize distance from the source, and interpose appropriate shielding.
- Dose constraint
- A prospective restriction on individual dose from a single source, set below the dose limit to ensure optimization of protection.
- Contamination control
- Measures to prevent the spread of radioactive material, including containment, protective clothing, surface monitoring, and prompt decontamination.
- Occupational dose limit
- The regulatory limit for a radiation worker: 20 mSv per year averaged over five years, with no more than 50 mSv in any single year.
- Public dose limit
- The annual effective dose limit for members of the public from all regulated practices, generally 1 mSv per year.
- Lens dose limit
- The equivalent dose limit for the lens of the eye, set at 20 mSv per year averaged over defined periods with no more than 50 mSv in a single year.
- Declared pregnant worker
- A worker who has voluntarily declared pregnancy; the dose to the fetus should not exceed 1 mSv during the remainder of the pregnancy.
- Personal dosimeter
- A device worn by an individual to measure accumulated dose, commonly using thermoluminescent or optically stimulated luminescent technology, with extremity and neutron variants.
- Internal dose assessment
- Estimation of committed dose from incorporated radionuclides using bioassay, whole-body counting, and air sampling together with biokinetic models.
- Decay-in-storage
- A waste management method in which short-lived radioactive waste is held until its activity decays below clearance levels before disposal.