ABMP Medical Health Physics cheat sheet

Radioactive decay law: N = N0·e^(−λt); activity A = λN, with λ = ln2/T½.

Half-life relations: after n half-lives, activity fraction remaining = (1/2)^n; mean life τ = 1/λ = T½/ln2 ≈ 1.44·T½.

Decay modes: alpha (Z−2, A−4), beta-minus (Z+1, A unchanged), beta-plus/positron (Z−1, A unchanged), electron capture (Z−1), isomeric transition (gamma emission, Z and A unchanged).

Gamma/X-ray interactions with matter: photoelectric effect dominates at low energy and high Z (∝ Z^4–5/E^3); Compton scattering dominates at intermediate energies in low-Z media; pair production requires photon energy ≥ 1.022 MeV.

Attenuation: I = I0·e^(−μx); mass attenuation coefficient μm = μ/ρ is approximately independent of physical state; half-value layer HVL = ln2/μ ≈ 0.693/μ.

Inverse-square law for a point source: exposure or dose rate ∝ 1/d²; doubling distance reduces dose rate to one quarter.

Coulomb inverse-square force F = k·q1q2/r²; photon energy E = hν = hc/λ, with hc ≈ 1240 eV·nm.

Attenuation in matter of charged particles: beta particles show a range distribution; alpha particles have a short, nearly discrete range (few cm in air, microns in tissue).

Units: 1 Bq = 1 decay/s; 1 Ci = 3.7×10^10 Bq; specific activity (Bq/g) = λN per gram.

Gas-filled detectors operate in ionization, proportional, or Geiger-Mueller regions depending on applied voltage; GM counters give high sensitivity but no energy information and dead-time losses.

Ionization chambers measure exposure or dose rate and are the reference instrument for radiation protection surveys; they have flat energy response when properly calibrated.

Scintillation detectors (NaI(Tl), CsI, plastic, LaBr3) convert energy deposition to light; NaI(Tl) resolution is roughly 6–7% at 662 keV, while HPGe gives <0.2% at 1.33 MeV.

Semiconductor detectors (HPGe, Si) provide high energy resolution for gamma spectroscopy; HPGe requires liquid nitrogen or mechanical cooling.

Dead time and resolving time: observed rate m = n/(1 − nτ) in a paralyzable model, where n is true rate and τ is resolving time.

Survey meter calibration is checked with a check source before use; energy dependence and geometry must match the calibration conditions.

Personnel monitoring: TLD and OSL dosimeters measure Hp(10) and Hp(0.07); ring badges measure extremity dose; neutron dosimeters use track-etch or albedo methods.

Counting statistics: relative standard deviation of a count N is 1/√N; background subtraction increases uncertainty as √(N_s + N_b).

Geiger-Mueller detectors cannot discriminate photon energy; spectroscopy requires proportional, scintillation, or semiconductor detectors.

Absorbed dose D = dE/dm, unit gray (Gy) = 1 J/kg; 1 rad = 0.01 Gy.

Equivalent dose H_T = w_R·D_T, unit sievert (Sv); radiation weighting factors w_R = 1 for photons/electrons, 20 for alpha particles and neutrons (energy dependent).

Effective dose E = Σ w_T·H_T, where tissue weighting factors w_T sum to 1.0 (e.g., gonads 0.08, breast 0.12, lung 0.12, red marrow 0.12, remainder 0.12).

Committed effective dose integrates dose over 50 years after intake (70 years for children); used for internal emitters.

Operational quantities: Hp(10) for effective dose, Hp(0.07) for skin/extremity, H*(10) for area monitoring; all in Sv.

Exposure X in air, unit roentgen (R); 1 R = 2.58×10^−4 C/kg, and in air approximately 0.00877 Gy.

Kerma K = dE_tr/dm (kinetic energy released per unit mass in a medium); air kerma is the basis of many calibration protocols.

Dose equivalent rate and dose rate: 1 mSv/h = 100 mrem/h; 1 rem = 0.01 Sv.

Brachytherapy and external beam dosimetry use TG-43 and TG-51 protocols; absorbed dose to water is the reference quantity.

Stochastic effects (cancer, heritable effects) have no threshold and probability increases with dose; deterministic (tissue reaction) effects have thresholds and severity increases with dose.

Acute radiation syndrome thresholds: prodromal ~0.5–1 Gy, hematopoietic syndrome ~1–2 Gy, GI syndrome ~5–10 Gy, CNS/cardiovascular >20 Gy.

Cell survival curve: linear-quadratic model S = e^(−αD−βD²); α/β ratio is high (~10 Gy) for early-responding tissues and low (~3 Gy) for late-responding tissues.

Law of Bergonié and Tribondeau: radiosensitivity is greatest in cells that divide rapidly, are undifferentiated, and have a long mitotic future.

Oxygen enhancement ratio (OER) for sparsely ionizing radiation is about 2.5–3; relative biological effectiveness (RBE) compares dose of reference radiation to test radiation.

DNA double-strand breaks are the principal lethal lesion; repair pathways include non-homologous end joining and homologous recombination.

Fetal effects: preimplantation (0–2 weeks) is largely all-or-none; organogenesis (2–8 weeks) risks malformation; 8–15 weeks carries highest risk of intellectual disability per unit dose.

Dose-rate effectiveness factor (DDREF) of ~2 is applied to low-dose, low-dose-rate risk estimates; LNT model assumes linearity with no threshold.

Radiosensitivity is modified by fractionation, dose rate, oxygen, and cell cycle phase (most sensitive in M and G2, most resistant in late S).

ICRP system of protection: justification, optimization (ALARA), and dose limitation.

ICRP 103 dose limits: occupational 20 mSv/y averaged over 5 years (max 50 mSv in any single year); public 1 mSv/y; lens of eye 20 mSv/y (occupational, averaged).

NCRP and US regulatory framework: 10 CFR Part 20 (occupational/public dose), Part 35 (medical use of byproduct material), Part 30/31/32 (general licensing), Part 37 (physical protection).

License types: general license, specific license, and broad-scope license; amendments and renewals required; termination requires decommissioning survey.

Dose limits for the embryo/fetus of a declared pregnant worker: 5 mSv (0.5 rem) over gestation (NRC).

Radiation Safety Officer and Radiation Safety Committee requirements; written directives and authorized user provisions under 10 CFR 35.

Occupational dose records: NRC Form 3 (notice to employees), Form 4 (planned special exposure), Form 5 (report of overexposure).

Public dose limit 1 mSv/y (0.1 rem) plus ALARA; unrestricted area limit 20 µSv/h (2 mrem/h) per NRC.

Medical event (misadministration) criteria under 10 CFR 35.3045: dose differs from prescribed by ≥20% and exceeds 0.5 Sv to an organ or 50 mSv effective dose.

X-ray production: bremsstrahlung spectrum with maximum energy equal to kVp; characteristic lines determined by anode material (W K-lines ~59–69 keV).

Half-value layer (HVL) of diagnostic beams is typically 2.5–4 mm Al at 70–100 kVp; minimum HVL is prescribed by regulation to limit low-energy dose.

mAs controls tube current-time product and total photons; kVp controls beam penetration and patient dose (roughly dose ∝ kVp²–3).

Fluoroscopy dose control: use pulsed fluoroscopy, last-image hold, and minimize fluoroscopy time; typical entrance skin dose rates ~10–50 mGy/min in normal mode.

Automatic exposure control (AEC) adjusts mAs to maintain receptor exposure; proper collimation and gonad shielding reduce patient dose.

Occupational protection: lead apron ≥0.25 mm Pb (0.5 mm Pb for fluoroscopy), thyroid shield, and use of personal dosimeters outside the apron at collar level.

Source-to-image distance and source-to-skin distance affect patient skin dose; increasing SID reduces skin dose and improves image quality.

Computed tomography dose index (CTDIvol) and dose-length product (DLP) are the standard CT dose metrics; effective dose ≈ DLP × k (k depends on body region).

Image quality metrics: spatial resolution, contrast resolution, noise, and modulation transfer function; dose and image quality trade off.

Common radionuclides: Tc-99m (T½ = 6 h, 140 keV gamma), I-131 (T½ = 8 d, beta + 364 keV gamma), F-18 (T½ = 110 min, 511 keV annihilation photons), Ga-68, Lu-177.

Tc-99m generator: Mo-99 (T½ = 66 h) decays to Tc-99m; elution efficiency and Mo-99 breakthrough limits (≤0.15 kBq Mo-99 per MBq Tc-99m).

PET physics: positron annihilation produces two 511 keV photons emitted ~180° apart; coincidence detection with time-of-flight improves SNR.

Radiation protection: syringe shields, lead-lined L-block, distance and time control; dose rate from a point source follows inverse-square.

Patient release criteria: 10 CFR 35.75 allows release if dose to any other individual is unlikely to exceed 5 mSv (0.5 rem).

Contamination control: survey with a thin-window GM or NaI probe; wipe tests for removable contamination; package surveys for sealed sources.

Dose calibrator (re-entrant ionization chamber) verifies activity before administration; geometry and volume affect readings.

Radiopharmaceutical therapy dose limits: bone marrow and organ constraints per EANM/SNMMI; dosimetry with MIRD formalism.

Shielding for PET requires high-density concrete or lead because 511 keV photons have high penetration; tenth-value layer for 511 keV in concrete ~ 40 cm.

External beam modalities: linac photons (6–20 MV), electrons (6–20 MeV), protons, and brachytherapy sources (Ir-192, I-125, Pd-103).

Percentage depth dose (PDD) and tissue-air ratio (TAR) / tissue-phantom ratio (TPR) describe depth dependence; build-up region is characteristic of megavoltage photon beams.

Isodose distributions and treatment planning: conformal, IMRT, VMAT, and SBRT techniques; dose constraints to organs at risk (OARs).

Brachytherapy: TG-43 formalism for dose to water; source strength in air kerma (U = 1 µGy·m²/h).

Dose verification: in vivo dosimetry, diode arrays, and film; daily QA includes output constancy, laser alignment, and energy checks.

Shielding for linacs: primary and secondary barriers, workload W, use factor U, occupancy T; NCRP Report 151 formalism.

Neutron production for >10 MV beams requires neutron shielding (borated polyethylene) and neutron survey instruments.

Patient safety: time-out procedures, independent dose calculation checks, and verification of treatment parameters before delivery.

Radiation protection for therapy staff: controlled area, interlocks, area monitors, and audiovisual patient observation.

Shielding design goal: reduce dose to workers and public below regulatory limits and ALARA; NCRP 147 (diagnostic), NCRP 151 (therapy), NCRP 49 (older).

Transmission through barrier: B = (P·d²)/(W·U·T) for primary barriers, where P is weekly dose limit, d distance, W workload, U use factor, T occupancy.

Secondary barrier calculation uses scattered and leakage radiation; leakage limit for linacs is 0.1% of primary beam.

Barrier thickness from transmission data: use attenuation curves; number of TVLs = log10(1/B), thickness = TVL × number.

Controlled vs uncontrolled areas: controlled area limit 1 mSv/y (or 5 mSv/y in some frameworks); uncontrolled 0.02 mSv/week (1 mSv/y).

Occupancy factor T: full 1, partial 1/4, occasional 1/16; use factor U applies only to primary barriers.

Structural considerations: lead, concrete, gypsum wallboard, and steel; concrete density ~2.35 g/cm³; lead equivalency for diagnostic barriers.

Radiation safety survey after construction: verify dose rates at barriers, doors, and penetrations; document with survey meter and TLDs.

Facility design elements: interlocks, warning lights, signage, and controlled area posting.

ALARA: as low as reasonably achievable, considering economic and social factors; use time, distance, shielding.

Occupational dose limit 20 mSv/y averaged over 5 years (ICRP) / 50 mSv in any year; NRC 10 CFR 20.1201 gives 50 mSv (5 rem) annual limit.

Investigation levels: 10% of limit triggers review; 30% triggers investigation; 100% triggers overexposure report.

Dosimeter placement: whole-body badge at collar or waist; ring badge for extremities; fetal badge for declared pregnant workers.

Public dose limit 1 mSv/y (0.1 rem); dose to a member of the public from a licensed facility must be ALARA.

Area monitoring: survey meters for dose rate, wipe tests for contamination, air sampling for airborne radioactivity.

Dose records: maintain lifetime occupational dose records; prior dose must be requested from new employees.

Emergency response: use of alarming dosimeters, personal protective equipment, and decontamination procedures.

Dose reduction from distance: doubling distance reduces dose by factor of 4; shielding thickness reduces dose exponentially.

Radioactive equilibrium: secular equilibrium when parent half-life >> daughter half-life; transient equilibrium when parent half-life > daughter.

Decay chains: natural series U-238, Th-232, U-235; radon progeny contribute significantly to public dose.

Beta spectrum: continuous energy distribution with maximum energy E_max and average energy ~1/3 E_max.

Gamma emission follows isomeric transition; internal conversion competes with gamma emission.

Activity units: becquerel (Bq) and curie (Ci); 1 mCi = 37 MBq.

Mass-energy equivalence: E = mc²; 1 u = 931.5 MeV.

Photon interactions: coherent scattering, photoelectric, Compton, pair production; total attenuation coefficient is the sum.

Fluence and energy fluence: Φ = dN/dA; Ψ = dE/dA; related to dose through mass energy absorption coefficients.

Radioactive decay is a random process; counting statistics follow Poisson distribution for small counts.

Detector efficiency: absolute efficiency = counts emitted / photons emitted; intrinsic efficiency = counts detected / photons incident.

Energy resolution R = FWHM/E × 100%; better resolution allows separation of close photopeaks.

Photomultiplier tube (PMT) converts scintillation light to electrical signal; gain depends on dynode voltage.

Pulse-height analyzers and multichannel analyzers sort pulses by energy for spectroscopy.

Calibration sources: Cs-137 (662 keV), Co-60 (1173, 1332 keV), Am-241 (60 keV).

Dose calibrators use sealed gas-filled ionization chambers; geometry corrections for syringes and vials.

TLD readout: glow curve analysis; annealing required before reuse; OSL uses optically stimulated luminescence.

Neutron detection: BF3 or He-3 proportional counters, moderated by polyethylene; rem meters for dose equivalent.

Survey meter selection: GM for contamination, ionization chamber for dose rate, scintillation for low-level gamma.

Dose equivalent H = D·Q·N (older formalism); modern equivalent dose uses w_R.

Effective dose is not a measurable quantity; it is derived from organ doses and used for risk estimation.

Dose-area product (DAP) and kerma-area product (KAP) are used in fluoroscopy and radiography.

CTDIvol = CTDIw / pitch; DLP = CTDIvol × scan length.

Brachytherapy dose: TG-43 formalism with radial dose function and anisotropy function.

Dose to water is the reference for therapy calibration; air kerma calibration converted via N_D,w.

Film and TLD dosimetry for patient dose measurement; optically stimulated luminescence for in vivo dosimetry.

Dose limits for lens of eye: 20 mSv/y occupational (ICRP 2011) and 15 mSv/y for public.

Extremity dose limit: 500 mSv/y (50 rem) to hands and feet.

Radiosensitivity of organs: highest for lymphoid tissue, bone marrow, gonads, and intestinal epithelium.

Carcinogenesis risk estimates: ~5% per Sv for solid cancers and leukemia at low doses (ICRP).

Heritable effects risk: ~0.2% per Sv for all generations.

Acute effects: erythema, epilation, and desquamation occur at skin doses of several Gy.

Fractionation spares normal tissue more than tumor because of repair and repopulation differences.

Cell cycle checkpoints: G1/S and G2/M; DNA damage response involves ATM, p53, and BRCA.

Bystander effect and genomic instability are non-targeted effects of radiation.

Radiation-induced cataracts have a threshold of ~0.5 Gy and are deterministic.

Prenatal radiation exposure: 0.1 Gy threshold for deterministic effects; risk of childhood cancer increases with dose.

NRC regulations: 10 CFR Part 20 (standards for protection), Part 35 (medical use), Part 30 (byproduct material), Part 31 (general licenses).

Agreement states regulate byproduct material under NRC oversight; state regulations may be more restrictive.

Licensee responsibilities: radiation safety officer, radiation safety committee, and authorized users.

Written directives for medical use; verification of patient identity and dose.

Recordkeeping: dose records, survey records, and calibration records must be retained per regulation.

Reporting: immediate notification for lost sources, overexposures, and medical events.

Sealed source accountability: leak tests every 6 months for sources > 10 µCi (0.37 MBq) for certain uses.

Occupational dose limits: 50 mSv/y whole body, 150 mSv/y lens (older NRC), 500 mSv/y extremities.

Public dose limit 1 mSv/y; unrestricted area dose rate limit 20 µSv/h (2 mrem/h).

X-ray tube: cathode filament emits electrons; anode target (tungsten) produces bremsstrahlung and characteristic X-rays.

Focal spot size affects spatial resolution; smaller focal spots improve resolution but limit tube current.

Grid use improves contrast by reducing scatter; grid ratio and Bucky factor affect patient dose.

Fluoroscopy: automatic brightness control adjusts kVp/mA; pulsed fluoroscopy reduces dose.

Patient shielding: gonadal, thyroid, and breast shielding where appropriate; shielding must not obscure diagnostic information.

Pediatric dose reduction: lower kVp/mAs, collimation, and avoidance of unnecessary repeat exposures.

Mammography uses low-energy X-rays (Mo/Rh target, ~25–35 kVp) with high-contrast requirements.

CT dose optimization: automatic tube current modulation, iterative reconstruction, and reduced scan length.

Occupational protection in interventional radiology: lead apron, thyroid shield, ceiling-suspended shield, and dosimeter placement.

Tc-99m decay: 140 keV gamma, 6 h half-life; used in ~80% of nuclear medicine procedures.

I-131 therapy: beta emitter with 364 keV gamma; patient isolation and radiation safety instructions.

PET radionuclides: F-18, C-11, N-13, O-15; short half-lives require on-site cyclotron or generator.

Radiopharmaceutical administration: verify activity with dose calibrator, check patient identity, and document.

Contamination control: use absorbent pads, gloves, and survey after procedures.

Waste management: decay-in-storage for short-lived radionuclides; survey before disposal.

Patient instructions after therapy: avoid close contact with children and pregnant women for a specified period.

Shielding: lead for Tc-99m; high-density materials for PET 511 keV photons.

Dose limits for therapy: bone marrow dose constraints and organ dosimetry.

Linac components: electron gun, waveguide, bending magnet, target, flattening filter, collimators.

Photon beam quality: nominal energy (6 MV, 10 MV); PDD increases with energy.

Electron beam: short range, used for superficial lesions; bolus to build up dose.

Treatment planning: CT simulation, contouring, inverse planning for IMRT/VMAT.

Quality assurance: daily, monthly, and annual QA per AAPM TG-142.

Brachytherapy sources: Ir-192 HDR, I-125 LDR; source calibration and leak testing.

Shielding: primary barrier for photon beams; neutron shielding for >10 MV.

Patient safety: independent verification of treatment parameters, in vivo dosimetry, and incident reporting.

Radiation protection: controlled area, interlocks, and area radiation monitors.

NCRP Report 147 provides shielding design goals for diagnostic imaging: 1 mSv/y for controlled areas, 0.02 mSv/week for uncontrolled.

Primary barrier thickness calculation uses transmission curves for the workload and use factor.

Secondary barrier: scatter and leakage; leakage limit 0.1% of primary.

Occupancy factor T: full 1, partial 1/4, occasional 1/16.

Use factor U applies to primary barriers only; secondary barriers use U = 1.

Barrier materials: lead, concrete, gypsum, and steel; lead equivalency for diagnostic.

Radiation safety survey after construction verifies dose rates at barriers and doors.

Facility design: interlocks, warning lights, signage, and controlled area posting.

Shielding for PET: 511 keV photons require high-density concrete or lead; tenth-value layer ~40 cm concrete.

ALARA: as low as reasonably achievable; use time, distance, and shielding.

Occupational dose limit: 20 mSv/y averaged over 5 years (ICRP); NRC 50 mSv/y.

Investigation levels: 10% review, 30% investigation, 100% overexposure report.

Dosimeter placement: whole-body badge at collar or waist; ring badge for extremities.

Public dose limit: 1 mSv/y; unrestricted area dose rate limit 20 µSv/h.

Area monitoring: survey meters, wipe tests, air sampling.

Dose records: maintain lifetime occupational dose records; request prior dose from new employees.

Emergency response: alarming dosimeters, PPE, decontamination.

Distance: doubling distance reduces dose by factor of 4; shielding reduces dose exponentially.

Atomic structure: protons, neutrons, electrons; atomic number Z, mass number A.

Isotopes: same Z, different A; isobars: same A, different Z; isotones: same N.

Radioactive decay: spontaneous transformation of unstable nuclei; decay constant λ.

Alpha decay: emits He-4 nucleus; mass number decreases by 4, atomic number by 2.

Beta decay: beta-minus (neutron to proton), beta-plus (proton to neutron), electron capture.

Gamma emission: photon emission from excited nucleus; no change in Z or A.

Half-life: time for activity to decrease by half; T½ = ln2/λ.

Activity: number of decays per unit time; A = λN.

Attenuation: exponential decrease of photons in matter; HVL = ln2/μ.

Gas-filled detectors: ionization chamber, proportional counter, GM counter.

Scintillation detectors: NaI(Tl), CsI, plastic; convert energy to light.

Semiconductor detectors: HPGe, Si; high energy resolution.

Dead time: time after a pulse during which the detector cannot record another event.

Counting statistics: Poisson distribution; relative standard deviation = 1/√N.

Calibration: check source, energy calibration with known isotopes.

Personnel monitoring: TLD, OSL, film badges; ring badges for extremities.

Survey meters: GM for contamination, ionization chamber for dose rate.

Spectroscopy: multichannel analyzer sorts pulses by energy.

Absorbed dose: energy deposited per unit mass; unit Gy.

Equivalent dose: absorbed dose × radiation weighting factor; unit Sv.

Effective dose: sum of tissue-weighted equivalent doses; unit Sv.

Committed dose: dose integrated over 50 years after intake.

Operational quantities: Hp(10), Hp(0.07), H*(10).

Exposure: ionization in air; unit roentgen.

Kerma: kinetic energy released per unit mass.

Dose rate: dose per unit time; 1 mSv/h = 100 mrem/h.

Dosimetry protocols: TG-43 for brachytherapy, TG-51 for external beam.

Stochastic effects: no threshold, probability increases with dose.

Deterministic effects: threshold, severity increases with dose.

Acute radiation syndrome: hematopoietic, GI, CNS syndromes.

Cell survival: linear-quadratic model S = e^(−αD−βD²).

Radiosensitivity: Bergonié and Tribondeau law.

OER: oxygen enhancement ratio ~2.5–3 for sparsely ionizing radiation.

DNA damage: double-strand breaks are the principal lethal lesion.

Fetal effects: preimplantation, organogenesis, and fetal periods.

DDREF: dose-rate effectiveness factor ~2 for low-dose risk estimates.

ICRP system: justification, optimization, dose limitation.

ICRP 103 dose limits: occupational 20 mSv/y, public 1 mSv/y.

NRC 10 CFR Part 20: occupational and public dose limits.

10 CFR Part 35: medical use of byproduct material.

License types: general, specific, broad-scope.

RSO and RSC requirements.

Occupational dose records: NRC Form 3, 4, 5.

Public dose limit: 1 mSv/y; unrestricted area limit 20 µSv/h.

Medical event criteria: 10 CFR 35.3045.

X-ray production: bremsstrahlung and characteristic X-rays.

kVp controls beam energy; mAs controls photon quantity.

HVL: 2.5–4 mm Al at 70–100 kVp.

Fluoroscopy: pulsed fluoroscopy reduces dose.

AEC: adjusts mAs to maintain receptor exposure.

Lead apron: ≥0.25 mm Pb; 0.5 mm Pb for fluoroscopy.

CT dose metrics: CTDIvol and DLP.

Image quality: spatial resolution, contrast, noise.

Occupational protection: dosimeter placement and shielding.

Tc-99m: 6 h half-life, 140 keV gamma.

I-131: 8 d half-life, beta and 364 keV gamma.

F-18: 110 min half-life, 511 keV annihilation photons.

PET: coincidence detection of 511 keV photons.

Patient release criteria: 10 CFR 35.75, 5 mSv to others.

Contamination control: survey and wipe tests.

Dose calibrator: verifies activity before administration.

Radiopharmaceutical therapy: organ dose constraints.

Shielding for PET: high-density materials for 511 keV.

External beam: linac photons and electrons.

PDD and TPR describe depth dependence.

Brachytherapy: TG-43 formalism.

Dose verification: in vivo dosimetry and film.

Shielding: NCRP 151 formalism.

Neutron production for >10 MV beams.

Patient safety: time-out and independent checks.

Radiation protection: controlled area and interlocks.

QA: AAPM TG-142.

Shielding design goal: below regulatory limits and ALARA.

NCRP 147 (diagnostic), NCRP 151 (therapy).

Transmission: B = (P·d²)/(W·U·T).

Secondary barrier: scatter and leakage.

TVL: thickness = TVL × log10(1/B).

Occupancy factor T: 1, 1/4, 1/16.

Use factor U applies to primary barriers.

Barrier materials: lead, concrete, gypsum, steel.

Radiation safety survey after construction.

ALARA: time, distance, shielding.

Occupational dose limit: 20 mSv/y averaged over 5 years.

Investigation levels: 10%, 30%, 100%.

Dosimeter placement: whole-body and ring badges.

Public dose limit: 1 mSv/y.

Area monitoring: survey meters and wipe tests.

Dose records: lifetime occupational dose records.

Emergency response: alarming dosimeters and PPE.

Distance: inverse-square law.

Decay law: N = N0·e^(−λt).

Half-life: T½ = ln2/λ.

Mean life: τ = 1/λ.

Alpha decay: Z−2, A−4.

Beta-minus decay: Z+1, A unchanged.

Beta-plus decay: Z−1, A unchanged.

Gamma emission: no change in Z or A.

Attenuation: I = I0·e^(−μx).

HVL = ln2/μ.

GM counter: high sensitivity, no energy information.

Ionization chamber: reference instrument for dose rate.

NaI(Tl): ~6–7% resolution at 662 keV.

HPGe: <0.2% resolution at 1.33 MeV.

Dead time: paralyzable model m = n/(1 − nτ).

TLD and OSL: personnel monitoring.

Counting statistics: relative standard deviation = 1/√N.

Calibration: check source and energy calibration.

Spectroscopy: multichannel analyzer.