Radiation Effects and Radiation Safety - Lecture Notes Review

Flashcards covering radiation units, biological effects of exposure, and radiation safety principles for both personnel and patients, as detailed in the lecture notes.

Traditional (British) System

One of two systems of measurement for radiation units.

Système Internationale (SI)

One of two systems of measurement for radiation units.

Coulombs per kilogram (C/kg)

The SI unit for radiation exposure.

Roentgen (R)

The Traditional (British) unit for radiation exposure, representing the quantity of radiation producing 2.08 x 10^9 ion pairs in 1 cm^3 of air.

Gray (Gy)

The SI unit for absorbed radiation dose, equal to 100 rad.

Radiation absorbed dose (rad)

The Traditional (British) unit for absorbed radiation dose, equal to 100 erg per gram of tissue.

Sievert (Sv)

The SI unit for dose equivalent, calculated as Gy × WR.

Roentgen equivalent in man (rem)

The Traditional (British) unit for dose equivalent, calculated as rad × WR.

Centigray (cGy)

The most commonly used dose unit in the United States.

Laws of Bergonié and Tribondeau

State that cell sensitivity to radiation exposure depends on age, differentiation, metabolic rate, and mitotic rate.

Cell sensitivity (Age)

Younger cells are more sensitive to radiation than older ones.

Cell sensitivity (Differentiation)

Nonspecialized cells are more sensitive to radiation than highly complex ones.

Cell sensitivity (Metabolic rate)

Cells that use energy rapidly are more sensitive to radiation than those with a slower metabolism.

Cell sensitivity (Mitotic rate)

Cells that divide and multiply rapidly are more sensitive to radiation than those that replicate slowly.

Short-term somatic effects

Biological effects of radiation observed within 3 months of exposure, associated with high radiation doses (>50 cGy), and categorized by affected body system (CNS, GI, hematological).

Deterministic effects

Biological effects that occur only after a certain amount of exposure has been received, with severity being dose dependent.

Long-term (latent) effects

Biological effects of radiation that may not be apparent for as many as 30 years.

Somatic effects

Biological effects of radiation that affect the body of the irradiated individual directly.

Genetic effects

Biological effects of radiation that occur as a result of damage to reproductive cells and may be observed as defects in the children or grandchildren of the irradiated individual.

Stochastic effects

Biological effects with no threshold amount of exposure required for occurrence, greater likelihood with increased dosage, no correlation between dosage and severity, and may occur from repeated small doses.

Occupational exposed radiographers

Radiographers who are prohibited from activities resulting in direct exposure to the primary x-ray beam and are protected by time, distance, and shielding principles.

Time (radiation protection)

A principal method of radiation protection aiming for minimum exposure duration.

Distance (radiation protection)

A principal method of radiation protection aiming for maximum distance from the radiation source.

Shielding (radiation protection)

A principal method of radiation protection that should always be used.

Dosimeters

Devices for monitoring personal radiation exposure, typically worn at the collar with the label facing out.

ALARA

The guiding philosophy for radiation safety, meaning 'As Low As Reasonably Achievable'.

Occupational exposure effective dose (EfD) limit

50 mSv per year for occupationally exposed individuals.

Cumulative (lifetime) dose limit

Equal to 1 rem (10 mSv) times the worker's age.

Principles to minimize patient dose

Include avoiding errors and repeats, collimating, using the highest kVp, using at least 40 inches SID, and providing shielding.

Collimate (patient protection)

Using the smallest possible radiation field for the anatomy of interest to minimize patient dose.

Highest kVp (patient protection)

Strategy to minimize patient dose by allowing the use of the lowest possible mAs.

40 inches SID (patient protection)

Recommended Source-to-Image Receptor Distance to limit patient exposure from tube housing leakage and collimator scatter.

Gonad shielding

Lead shields of at least 0.5-mm lead equivalent that prevent unnecessary radiation to reproductive organs.

Conditions for gonad shielding

Required when the patient is of reproductive age or younger, and the shield will not interfere with the examination (generally applies to most patients younger than 55 years).

Shielding and AEC

If an automatic exposure control (AEC) machine senses a lead shield, it may use more radiation than necessary.

Misplacement of lead shield

Can lead to repeat exposures and increased patient dose.

First trimester (fetal radiation risk)

The period of greatest risk to a fetus for radiation exposure.

Pregnant worker EfD limit

50 mSv of whole-body radiation over the 9-month course of the pregnancy for occupationally exposed pregnant workers.

Advising female patients of childbearing age

Regulations require these patients to be advised of potential radiation hazards before an exam, by signs and direct questioning.