RAD 260: Safety Flashcards
Define air kerma
Used to define radiation exposure or radiation delivered to a specific point.
Unit of measurement = Gy
Absorbed dose
Amount of energy ABSORBED per unit mass of tissue
Unit measurement of tissue = Gy
Effective dose
Estimates the risk present when various tissues are irradiated
Unit measurement = sievert(Sv)
(Absorbed dose x radiation weighting factor x tissue weighting factor)
Type of radiation damage: Somatic
What is somatic?
Damage to the exposed individual
(Damage to the cell itself)
Type of radiation damage: Genetic
Define it
Damage to the genetic code of the germ cell contained in the DNA; may be passed to the next generation
Absorption and scatter (loss of intensity) of the x-ray beam as it passes through the patient.
Attenuation
- Produced by low-energy x-ray photons
- Atomic electrons are not removed but vibrate because of the deposition of energy from the photon
- Does not affect image less than 70 kVp
Coherent scatter
What results in them complete absorption of the incoming x-ray photon; this interaction produces contrast in the radiographic image
Photoelectric interaction
What results in scattering of the incoming x-ray photon; scatter produced by this interaction must be removed from the beam before it strikes the IR
Compton interaction
The source of the exposure to the radiographer or radiologist during fluoroscopy
Compton scatter
Randomly occurring effects of radiation; the probability of such effects is proportional to the dose (increased dose equals increase probability, not severity, of effects)
Stochastic effects
Effects that become more severe at high levels of radiation exposure and do not occur below a certain threshold dose
Tissue reactions
Indicates that NO level of radiation can be considered completely safe
-a response occurs at every dose
Linear-nonthreshold
Indicates that a lower doses of radiation exposure, no response is expected
- When the threshold dose is exceeded, the response is directly proportional to the dose received
Linear - threshold
Indicates that at a lower doses of radiation exposure, no response is expected
- When the the threshold dose is exceeded, the response is not directly proportional to the dose received and is increasingly effective per unit dose
Nonlinear - threshold
Indicates that no level of radiation can be considered completely safe
- a response occurs at every dose
Nonlinear - nonthreshold
What is the occupational exposure - annual equivalent dose limits for the lens of the eyes and localized areas of skin & hands?
Eyes: 150 mSv
Hands/skin: 500 mSv
Ability to produce biological damage, varies with LET
Relative biological effectiveness (RBE)
Which law states that cells are most sensitive to radiation when they are immature, undifferentiated, and rapidly dividing?
Law of Bergonié and Tribondeau
Which blood cells are the most radiosensitive in the body?
Lymphocytes
What are the early tissue reactions?
- Erythema
- Epilation
- Decreased blood count
- Acute radiation syndrome
What are the late tissue reactions?
- Cataractogenesis
- Thyroid: cancer or cessation of function
- Effect of fertility
What are the stochastic effects?
- Carcinogenesis: radiation induced malignancy
- Non malignant radiodermatitis
- Embryologic effects
- Genetic mutations
Amount of energy deposited per unit length of travel of radiation passing through matter
Linear energy transfer (LET)
How many mm should our lead aprons be equivalent to?
At least 0.25 mm
Law that governs the intensity os the x-radiation; states that the intensity of the x-ray beam is inversely proportional to the square of the distance between the source of the X-rays and the object
Inverse square law
Blood count can be depressed with a whole-body dose of?
0.25 Sv
What dosimeter has aluminum oxide layers that stores energy that is released when exposed to a laser?
OSL dosimeters
What dosimeter stores energy in lithium fluoride crystals that is released when heated?
Thermoluminescent dosimeters (TLDs)
The process of cell division for germ cells is called?
Meiosis
