Protection CH 9 Flashcards
The long term results of radiation exposure
late effects
The science that deals with the incidence, distribution, and control of disease in a population
epidemiology
Demonstrated graphically through a curve that maps as observed effects of radiation exposure in relation to dose received. As dose increases so does effects.
radiation dose-response relationship
a point at which a response or reaction to an increasing stimulation first occurs. means that below a certain radiation dose, no biologic effects are observed
threshold
relationship meaning that any radiation dose will reproduce a biologic effect-No radiation dose is absolutely safe
nonthreshold
estimates the risk associated with low level radiation
linear quadratic nonthreshold curve
this model accurately reflects the effects of high LET radiation (neurons and alpha rays) at higher doses
linear dose response curve
when living organisms that have been exposed o radiation sustain biologic damage, the effects are classified as somatic effects when late effects are mutational or randomly occurring biologic somatic change, independent of dose
stochastic (probabilistic) somatic effects
effects that appear months or years after exposure to ionizing radiation–could result from previous whole or partial-body acute, high radiation doses or they may be the product of individual low level doses sustained over several years
late somatic effects
late effects that can be directly related to dose received and occur months or years after a high level radiation exposure.. Ex. cataract formation, reduced fertility, organ atrophy
late nonstochastic (deterministic) somatic effects
late effects that do not have a threshold, occur in an arbitrary or probabilistic manner, have a severity that does not depend on dose and occurs months or years after high level radiation exposure.. Examples: cancer and birth defects
late stochastic (probabilistic) somatic effects
randomly occurring effects that are nonthreshold. this means the greater the dose an individual receives the greater the chance that a specific late effect will be seen. ex. cancer and genetic disorders
stochastic events
when the biologic effects demonstrate the existence of a threshold, a dose below which a person has a negligible chance of sustaining specific biologic damage, and the severity of that biologic damage increases as a consequence or increases absorbed dose
nonstochasctic events
Cancer is the most important late stochastic somatic effects caused by exposure to ionizing radiation. Cancer effect is a random occurrence that does not seem to have a threshold and for which the severity of the disease is not dose related
carcinogenesis
biologic effects of ionizing radiation to future generations
genetic effects
the radiation dose that causes the number of spontaneous mutations occurring in a given generation to increase to two times their original number
doubling dose
know the difference between stochastic effects and deterministiec effects
Stochastic is the probability that the effect happens depends upon the received dose, but the severity of the effect does not. deterministic effects-both the probability and the severity of the effect depend on the dose
For a dose response curve, what numbers variable are plotted along the axes of the graph to demonstrates
horizontal=dose received
vertical=biologic effects observed
curve=either be linear of non linear and will depict either a threshold or nonthreshold
in reference to the linear quadratic nonthreshold curve what do the following terms mean:
linear-
quadratic-
linear-dose
quadratic-dose squared
how are nonstochastic effects (ie skin erythema) demonstrated graphically>
linear threshold curve of radiation dose response
what is the actual meaning of stochastic events
randomly occurring effects that are nonthreshold. meaning the greater the dose an individual receives the greater the chance that a specific late effect will be seen
what are examples of late deterministic somatic effects
cataract formation fibrosis organ atrophy loss of parenchymal cells reduced fertility sterility
be able to list the 3 major types of late somatic effects
carcinogenesis
cataractogenesis
embryologic effects(birth defects)
what single dose will likely cause the formation of cataracts
2 gy or 200 rad
what procedures produces the highest radiation exposure to the lens of the eyes
fluoroscopic procedures
when are all life forms more vulnerable to radiation
embryonic stage
when Is the embryo-fetus most susceptible to death from radiation
during first 8 weeks of development at a dose in excess of 200 mSv (20 rem)
what could happen to an embryo fetus if it is exposed to radiation during organogenesis
growth inhibition, mental retardation, microcephaly, genital deformities, and sense organ damage have a chance of occurrence
at what dose does death occur to the fetus
excess of 200 mSv (@) rem)
Genetic effects occur as result of
radiation induced damage to the DNA molecule in the sperm and ova of an adult
what happens when radiation interacts with DNA molecules
it can modify the structure of the molecule by causing breaks in the chromosomes or change the amount of DNA belonging to a cell by causing a deletion or an alteration in the sequence of the nitrogen bases
what does the information obtained from the fruit flies experiments indicate
that genetic effects does not have a threshold– a dose at which radiation causes genetic effects begin to occur and below which they cannot occur. this implies that even the smallest dose could cause some genetic damage
what must be done to minimize the possibility of genetic effects for those in medical imaging
You must use gonadal shielding effectively and with all exposures you must use and maintain ALARA
