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what is ionization a production of?
ionization results in two things what are the?
dislodged negative electron
how does radiation injury occur
radiation injury results when x-rays strike _____
x-ray photons interact with _____ ----> ______, excitation and ______ ----->______ changes ----> ______ changes
ionization causes _____ changes
through the formation of what does xradiation cause cell damage?
what is defined as an uncharged atom or molecule that exists with a single unpaired electron in its outermost shell
when do free radicals form
when the xray photon ionizes water
what happens when an xray photon ionizes water?
produces hydrogen and hydroxyl free radicals
what is the primary component of a living cell
what three things may a free radical do to achieve stability
recombine without causing changes in the molecule
may combine with other free radicals and cause changes
combine with ordinary molecules to form a toxin capable of producing widespread cellular changes
what is an example of a free radical combining with an ordinary molecule to form a toxin?
what are two theories used to describe how radiation damages biologic tissues?
which theory suggests that cell damage results when ionizing radiation directly hits critical areas or targets within the cell.
direct theory of radiation injury
_____ theory occurs infrequently compared to ______ theory which occurs more frrequently
direct theory occurs ______ compared to indirect which occurs _______
what is an example of direct theory
xray photon directly striking the DNA of the cell
what theory suggestst that xray photons are absorbed within the cell and cause the formation of toxins, which in turn damage the cell
indirect theory of radiation injury
what is an example of indirect theory
xray photons absorbed by water forming a free radical
what does the combination of free radicals cause?
cellular dysfunction and biologic damage
why does indirect theory occur more frequently?
because of the high water content of the cells
what can be used to correlate the response or damage of tissues with the dose or amount of radiation received
dose response curve
t/f there is a safe amount of radiation exposure
false! No safe amount!!
what are the two classifications for biologic effects from radiation
which biologic effects occur as a direct function of dose
_____ effects do not have a dose threshold
stochastic effects _____ have a dose threshold
what are some examples of stochastic effects
cancer (tumor) induction and genetic mutations
the probability of stochastic effects occurrence _____ with increasing absorbed dose
does the severity of the stochastic effects depend on the magnitude of the absorbed dose
No it does not depend on magnitude of absorbed dose
nonstochastic effects is also known as?
what are somatic effects that have a threshold and that increase in severity with increasing absorbed dose
nonstochastic effects (deterministic effects)
what are some examples of nonstochastic effects?
loss of hair
what biologic effect has these examples: erythema, loss of hair, cataract fomation and decreased fertility
nonstochastic effects require more or less radiation than stochastic to cause serious impairment of health.
t/f nonstochastic effects require larger radiation doses to cause serious impairment of health
_____ effects are genetic but _____ effects are ones you can see
_____ _____ that follow absorption of radiation occur rapidly at a molecular level
t/f observable effects of radiation are visible immediately after exposure
false-no visible immediately after
what is the time that elapses between exposure to ionizing radiation and the appearance of observable clinical signs
what determines the length of the latent period?
total dose of radiation received and amount of time or rate it took to receive the dose
what is the sequence of radiation injury
period of injury
what is involved in the period of injury?
what are some examples of cellular injuries during the period of injury (6)
changes in cell function
breaking or chumping of chromosomes
formation of giant cells
cessation of mitotic activity
abnormal mitotic activity
what is the last event in the sequence of radiation injury
are all cellular radiation injuries permanent?
no-not all cellular radiation injuries are permanent
cellular damage is followed by what?
____ _____ radiation damage is repaired within the cells of the body
where is low level radiation damage repaired?
in the cells of the body
what is it called when repeated radiation exposure leads to health problems
effects of radiation exposure are _____ and ____ damage accumulates in the tissues
what is defined as the quantity of radiation receive or the total amount of radiation energy absorbed.
t/f more damage occurs when tissues absorb large quantities of radiation
what is defined as the rate at which exposure to radiation occurs and absorption takes place
t/f more radiation damage takes place with high dose rates because a rapid delivery of radiation does not allow time for the cellular damage to be repaired
true (dose rate)
what is defined as the areas of the body exposed to radiation
amount of tissue irradiated
____ _____: more damage occurs in cells that are most sensitive to radiation such as rapidly dividing cells and young cells
what age group is more susceptible to radiation
radiation effects in hematopoietic tissues causes?
what tissues would you need to radiated to cause leukemia
hematopoietic (blood forming) tissues
what are the radiation effects with the reproductive cells?
which tissues or organs have the radiation effect of carcinoma? (2)
what radiation effect do you get with the thyroid?
what radiation effects do you get with the skin?
what radiation effects do you get with the eyes
following the latent period effects seen within minutes days or weeks are termed what?
short term effects
what are shor term effects associated with?
large amounts of radiation absorbed in a short time
what is ARS?
ACUTE RADIATION SYNDROME
what are the symptoms of ARS?
are short term effects of radiation applicable to dentistry?
what are effects that appear after years, decades or generations?
long term effects
what are long term effects associated with?
small amounts of radiation absorbed repeatedly over long period
what are low levels of radiation exposure linked with?
what is ARS associated with?
short term radiation effects
all the cells in the body can be classified either ____ or ____
what are the somatic cells in the body?
all the cells in the body exept the reproductive cells
what are the genetic cells in the body
_____ effects are seen in the person being irradiated
_____ effects are not seen in the person irradiated but are passed on to future generations
what do changes in somatic cells produce?
what are major somatic effects of radiation exposure?
t/f somatic effects are not transmitted to future generations
t/f genetic damage can be repaired
FALSE!! cannot be repaired (future generations is just screwed)
the cell ____ is more sensitive to radiation than the ____
damage to the cell nucleus affects what?
the chromosomes containing the DNA
damage to the cells DNA results in what?
disruption of cell division (disrupt cell function or cell death)
what is a cell that is sensitive to radiation called?
what is is a cell that is resistant to radiation called?
what are three things that determine the response of a cell to radiation exposure?
how does mitotic activity determine the response of the cell to radiation exposure?
cells that divide frequently or undergo many divisions over time are more sensitive to radiation
how does cell differentiation determine the response of the cell to radiation exposure?
cells that are immature or are not highly specialized are more sensitve to radiation
how does cell metabolism determine the response of the cell to radiation exposure
cells that have higher metabolism are more sensitve to radiation
what are 3 examples of radiosensitive cells?
immature reproductive cells
young bone cells
what is the cell that is most sensitive to radiation?
what are 3 radioresistant cells?
what are 4 examples of radiosensitive organs?
radiosensitive organs are composed of ______ cells
what are 3 examples of radioresistant tissues?
how is an organ classified as a critical organ?
if the organ is damaged it diminishes the quality of a person's life
if an organ is damaged and diminishes a person's life what is that organ classified as?
what are critical organs involved in dentistry (4)
lens of the eye
what is the ICRU
international commission on radiation units and measurement
what quantities of radiation are the ICRU measurements used to define? (3)
what are the two systems used to define radiation measurements
tradition system or standard system
SI system or International system of units
what are the traditional units of radiation measurements
radiation absorbed dose (rad)
roentgen equivalent in man (rem)
what are the SI units of radiation measurement?
what is defined as the measurment of ionization in the air produced by exrays
the traditional nit of exposure for xrays is?
what is defined as the quantity of xradiation or gamma radiation that produces an electrical charge or 2.58 X 10
coulombs in a kilogram of air at standard temperature and pressure conditions
the roentgen is limited to measurements in the ____ it cannot measure amount of radiation _____
what is a coulomb?
unit of electrical charge
what is the conversion of 1 R to a C/kg?
1 R=2.58 X 10
what is the conversion of 1 C/kg to R?
1 C/kg= 3.88 x 10
what can be defined as the amount of energy absorbed by a tissue
what is the traditional unit of dose?
radiation absorbed dose (rad)
t/r the rad is not restricted to air?
what is a special unit of absorbed dose that is equal to the deposition of 100 ergs of energy per gram of tissue
what is the SI unit equivalent to the rad
what is the conversion for 1 rad to the gray
what is the conversion for 1 gray to rads
1 gray=100 rads
what is the measurement used to compare biologic effects of different types of radiation
what is the tradition unit of dose equivalent
roentgen equivalent man or rem
what is the product of absorbed dose (rads) and a quality factor specific for the type of radiation
what is used to place the exposure effects of different types of radiation on a common scale
quality factor or dimensionless multiplier
what is the SI unit for equivalent of the rem?
what is the conversion for 1 rem to Sv
1 rem=0.01 Sv
what is the conversion for 1 Sv to rems
1 Sv=100 rems
in dental radiograph the gray and the ____ are equal and the roentgen ____ and ____ are considered approximately equal
what prefix is used to accommodated the small doses of radiation used?
what is the daily exposure of radiation that humans undergo called?
what is cosmic radiation?
originates from the stars and sun
what does a persons exposure to cosmic radiation depend on?
what is terrestrial radiation?
emitted from radioactive materials present in the earth and air
what is an example of terrestrial radiation?
postassium-40 and uranium
what is artificial radiation?
modern technology or man made
what is the greatest contributor to artificial radiation?
the medical radiation exposure _____ the average yearly dose from all other exposures combinded
what can be defined as the likelihood of adverse effects or death resulting from exposure to a hazard
what is the risk in dental radiography
cancer induction from ionizing radiation
what is the potential risk of dental radiography inducing a fatal cancer in an individula?
3 in 1 million
what is the risk of a person developing cancer spontaneously
3300 in 1 million
what is an estimated dose necessary to produce cancer in the thyroid gland?
what is the average dose to the thyroid gland with dental radiography?
what is the dose needed to cause leukemia?
what is the average bone marrow dose in dental radiography?
1 to3 mrads
a total of ____ rads in a ____ day period causes erythema or reddening of the skin
to produce erythema or reddening of the skin more than ____ dental films in ____ day period would have to be exposed
how many mrads are necessary to induce cataract foramtion?
what is the average dose to the cornea during dental radiography?
dental radiographs should be prescribed for a patient only when?
the benefit of disease detection outweighs the risk of biologic damage
when dental radiographs are properly prescribed and exposed the ____ of disease detection ___ _____ the risk of damage from xradiation