Radiology Chapter 5&6 Flashcards
symptoms of the short-term radiation effects after a massive dose of ionizing radiation
Acute radiation syndrome (ARS)
Adopted as a culture and attitude by professionals who work with ionizing radiation to minimize radiation exposure and risks
ALARA
the theory that radiation-exposed tissues accrue damage and may function at a diminished capacity with each repeated exposure
cumulative effect
when the severity of the change is dependent on the dose
deterministic effect
states that cell damage results when ionizing radiation directly hits critical areas within the cell
direct theory
graph produced when radiation dose and the resultant biological response are plotted
dose response curve
cells contained within the testes and ovaries, containing the genes
genetic cells
radiation effect that is passed on to future generations
genetic effect
change in the genetic material of a cell that passes from one generation to another
genetic mutation
states that cell damage results indirectly when x-rays cause the formation of toxins in the cell such as hydrogen peroxide. Toxins in turn cause the cell damage
formation of ion pairs
indirect theory
formation of ion pairs
ionization
the exposure of an object or a person to radiation. Term can be applied to radiations of various wavelengths, such as infrared rays, ultraviolet rays, x-rays, and gamma rays
irradiation
: following exposure to radiation, injury that results in damage that is not repaired during the recovery period. May give rise to later long-term effects of radiation exposure
irreparable injury
: the time between exposure to radiation and the first clinically observable symptoms. Latent means hidden
latent period
states that the radiosensitivity of cells and tissues is directly proportional to their reproductive capacity and inversely proportional to their degree of differentiation
law of B and T
amount of radiation that is sufficient to cause the death of an organism
lethal dose
a graph showing the relationship between the dose of exposure and the response of the tissues, indicating that any amount of radiation, no matter how small, has the potential to cause a biological response
nonthreshold dose response curve
radiation-induced changes that follow the latent period
period of injury
ionization can dissociate water within a cell into hydrogen and hydroxyl radicals that have the potential to recombine into new chemicals such as hydrogen peroxide. These new chemicals act as toxins to the body, causing cellular dysfunction. Considered an indirect effect of radiation exposure
radiolysis of water
refers to a substance or tissue that is not easily injured by ionizing radiation
radioresistant
refers to a substance or tissue that is relatively susceptible to injury by ionizing radiation
radiosensitive
period following exposure to radiation, where some healing can take place
recovery period
the chance or likelihood of adverse effects or death resulting from exposure to a hazard
risk
any body cells except the reproductive cells
somatic cells
when radiation affects all body cells except the reproductive cells
somatic effect
when a biological response is based on the probability of occurrence rather than the severity of the change
stochastic effect
a graph showing the relationship between the dose of exposure and the response of the tissues, indicating that there is a “threshold” amount of radiation, below which no biological response would be expected
threshold dose response curve
Inventors of Law of B and T
Bergonie and Tribondeau
radiosensitive cells from high sensitivity to low sensitivity
white blood cells (lymphocytes) red blood cells (erythrocytes) immature reproductive cells epithelial cells connective tissue cells bone cells nerve cells brain cells muscle cells
somatic effect occurs when
biological change/damage occurs in irradiated individual, not passed to offspring
genetic effect describes
changes in hereditary material does not effect irradiated individual, but future generations
factors that determine radiation injuries
total dose dose rate area exposed variation in species individual sensitivity variation in cell sensitivity variation in tissue sensitivity age
critical tissues for dental radiography in head and neck region
mandible (red bone marrow)
lens of eye
thyroid gland
possibly the hypothalamus-pituitary-thyroid combination
studies of occupational workers exposed to chronic low levels of radiation have shown
no adverse biological effect
x-rays ionize water, resulting in
formation of free radicals, which recombine to form toxins
many body cells (somatic cells) have a recovery rate of
almost 75% during the first 24 hours
determining whether or not an exposure is potentially harmful, a radiographer should consider
the quantity and the duration of exposure and which body area to be irradiated
genetic cells cannot
repair themselves
the primary cause of biological damage from radiation is
ionization
direct injury from radiation occurs when the x-ray photons
strike critical cell molecules
indirect injury from radiation occurs when the x-ray photons
ionize water and form toxins
according to the law of B and T, cells with a high reproductive rate are described as
radiosensitive
what cells are most radiosensitive?
white blood cells
what cells are most radioresistant?
muscle cells
when the effect of radiation exposure is observed in the offspring of an irradiated person, but not in the irradiated person, this is called the
genetic effect
a dose response curve indicating that any amount of radiation, no matter how small, has the potential to cause a biological response is called
nonthreshold
ALARA stand for
as low as reasonably achievable
five possible biological responses of an irradiated cell
o Nothing-the cell is unaffected by the exposure
o Cell is injured or damaged but repairs itself and functions at preexposure levels
o Cell dies, but is replaced through normal biological processes
o Cell is injured or damaged, repairs itself, but now functions at a reduced level
o Cell is injured or damaged and repairs itself incorrectly or abnormally, resulting in a biophysical change (tumor or malignancy)
according to the factors that determine radiation injury based on age, a _____________ year old is most radiosensitive
6 year old
sequence of events following radiation exposure
latent period
period of injury
recovery period
when a biological response is based on the probability of occurrence rather than the severity of the change it is called
a stochastic effect
what is considered a short term outcome following radiation exposure
acute radiation syndrome
full term, low birth weight is possibly associated with radiation exposure to
thyroid gland
hypothalamus
pituitary gland
During exposure of an intraoral dental radiograph, approximately how much smaller is the dose of radiation in the gonadal area than at the surface of the face?
0.0001
not considered critical for dental radiography
spinal cord
the potential risk of a full mouth dental x-ray examination inducing cancer to a patient has been estimated to be
2.5 per 1,000,000 examinations
term that best expresses comparisons between dental radiation exposure and natural background exposure
effective dose equivalent
the cornerstone of all healthcare professions
continuing education
