Questions and Answers
What are the objectives at the end of the class related to radiation safety?
To describe the mechanism of occurrence of side effects of ionizing radiation, list and explain types of side effects, list and describe the principle of radiation safety, describe the principle of quantification of received radiation quantity.
What are the three types of radiation-induced damages?
Lethal, Potentially lethal, Sub-lethal
What are examples of deterministic effects of radiation?
Skin reddening (erythema)
Stochastic effects of radiation consist mainly of cancer and genetic effects.
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Radiosensitivity of cells is proportional to rate of cell __________ and inversely proportional to the level of cell specialisation.
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What method is recommended for limiting exposure to radiation by increasing the distance?
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Which rays are primarily affected by limiting exposure through increased distance?
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What is a common material used for shielding against radiation in radiology?
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What is the purpose of lead aprons in radiology departments?
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The distance from the X-ray tube affects exposure to radiation proportionally.
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Study Notes
Radiation Safety
Biological Effects of Radiation
- Radiation damages to chromosomes can occur through direct or indirect damage
- Indirect damage: OH free radical reacts with DNA, causing damage (75% of radiation-caused DNA damage)
- Direct damage: DNA molecule is struck by radiation, resulting in damage
- There are three types of radiation-induced damage: lethal, potentially lethal, and sub-lethal
Radiation-Induced Responses
- Can be grouped into stochastic and non-stochastic effects
- Stochastic effects: occur by chance, include cancer and genetic effects, and have no threshold
- Non-stochastic effects: have a threshold, include cataract formation, skin reddening, and sterility
Radiation Dose
- Measured in Grays (Gy) or Rems (R)
- Exposure to 1 Roentgen approximates 0.9 rad in air
- Biological Equivalent Dose (BED) takes into account the quality factor (QF)
Goals of Radiation Safety
- Eliminate deterministic effects
- Reduce incidence of stochastic effects
Radiosensitivity of Cells
- Radiosensitivity is proportional to rate of cell division and inversely proportional to level of cell specialization (Law of Bergonie and Tribondeau)
- Younger patients are more radiosensitive due to higher rate of cell division and incomplete differentiation
- The unborn child is the most sensitive
Radiation Dosimetry
- Quantifying radioactive decay: measured in disintegrations per second (dps) or Becquerel (Bq)
- Quantifying exposure and dose: measured in Roentgen (R) or rad (Roentgen absorbed dose)
Radiation Control Principles
- ICRP (International Commission for Radiation Protection) principles: justification, optimization, and dose limitation
- ALARA (As Low As Reasonably Achievable) principle for minimizing patient exposure
Protection of the Conceptus
- Women of childbearing age: protection of a possible conceptus when X-ray imaging the region from the knees to the diaphragm
- Ask pregnancy question, pregnancy test, 10-day rule, and 28-day rule
Radiation Dose Limits
- Dose limits for personnel and patients
Personnel Monitoring Devices
- Types of dosimeters: pen dosimeter, TLD rings, electronic personnel dosimeter (EPD), and film badges
- Dosimetry requirement decision tree: depends on type of radiation source and job requirements
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