Chapter 9: Basic Radiation Protection and Radiobiology - Vocabulary

VOCABULARY flashcards covering key terms, units, protection principles, and dose limits from the notes.

Ionizing radiation

Radiation with enough energy to eject electrons from atoms, causing ionization and potential biological effects.

Ionization

Process of removing electrons from atoms, creating charged ions.

ALARA

As Low As Reasonably Achievable; principle to minimize radiation exposure.

Natural sources of ionizing radiation

Ionizing radiation that comes from natural background sources.

Manmade sources of ionizing radiation

Radiation produced by human activities; medical and dental X-ray examinations contribute most.

X-ray production

Process requiring a source of electrons, high-speed motion, and a mechanism for abrupt deceleration to emit X-rays.

Cathode filament

Heated wire in the X-ray tube that emits electrons; current controlled by milliamperage.

Milliamperage (mA)

Electric current through the cathode filament; controls number of emitted electrons.

Kilovoltage peak (kVp)

Potential difference accelerating electrons toward the anode; affects X-ray energy.

Anode

Positive electrode where high-energy electrons decelerate to produce X-rays.

Primary beam

X-ray beam leaving the tube toward the patient before interactions.

Total absorption

X-ray energy completely absorbed by matter with no transmission.

Transmission (through with no energy loss)

X-ray beam passes through matter without energy loss.

Scattering

X-ray interactions that deflect photons and reduce energy, creating secondary interactions.

Roentgen (R)

Traditional unit of exposure in air; not used for absorbed dose.

Gray (Gy)

SI unit of absorbed dose; energy deposited per kilogram of matter.

Rad

Traditional unit of absorbed dose; replaced by Gray.

Sievert (Sv)

SI unit of dose equivalent; accounts for biological effect via quality factor.

Rem

Traditional unit of dose equivalent; replaced by Sievert.

Becquerel (Bq)

SI unit of activity; decays per second.

Air kerma

Kinetic energy released in matter; energy transferred from radiation to air per unit mass.

KERMA

Kinetic Energy Released in Matter; energy transferred from radiation to matter.

Exposure in air

Roentgen; amount of ionization in air due to exposure to X-rays or gamma rays.

Absorbed dose

Gray; amount of energy deposited per unit mass in a medium.

Dose equivalent

Sievert; absorbed dose adjusted for biological effect using quality factor.

Activity

Becquerel; decays per second.

Effective dose

Dose accounting for the varying sensitivities of tissues; measured in Sieverts.

Dose limits for occupational exposure

Annual limit of 50 mSv (5 rem); cumulative limit of 10 mSv × age.

Public exposure dose limits

Annual limits: continuous/frequent 1 mSv; infrequent 5 mSv.

Lens of the eyes dose limit

Annual limit of 150 mSv (15 rem) for the lens.

Skin, hands, and feet dose limit

Annual limit of 500 mSv (50 rem).

Embryo-Fetal exposure limit

Monthly equivalent dose limit of 0.5 mSv (0.05 rem) during pregnancy.

SID (Source-to-image distance)

Distance between the radiation source and receptor; recommended at least 40 inches (100 cm).

Cardinal rules of protection

Time, Distance, Shielding; minimize exposure time, maximize distance, use shielding.

Gonadal shielding

Shields used to protect reproductive organs during radiographic procedures.

Shielding types

Flat contact shields, shadow shields, shaped/contour shields.

Patient protection and ALARA

Use of shielding and technique optimization to minimize patient dose.

Protection of radiographers

Apply the Cardinal Rules; use barriers; minimize time in primary beam.

Dosimeters

Personnel monitoring devices that measure radiation exposure.

Dosimeter placement

Worn at collar level outside lead apron; pregnant workers may wear a second at the waist under the apron.

X-radiation effects

Ionizations in tissue can cause cellular disturbances and genetic alterations; dose-dependent.

No-threshold vs threshold model

Concepts about radiation risk; some models propose no safe dose, others a threshold.