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RadioBio Ch33

Radiosensitivity cells sensitivity and reaction to radiation; critical in how radiation affects the human body
sensitivity of cells (3: most, less, least) lymphocytes, muscle, central nervous system
Law of Bergonie and Tribondeau the radiosensitivity of living tissue varies with maturation and metabolism
Radiosensitivity is ________ proportionate to a cell's reproductive activity directly
Name the 4 corollaries of the Law of B and T 1. stem cells are more radiosensitive. 2. young tissues are more radiosensitive. 3. increasted proliferation rate = more radiosensitive. 4. increase metabolic rate = more radiosensitive.
Radiosensitivity is ________ proportionate to its degree of differentiation (specialized) indirectly
Linear Energy Transfer (LET) measure of the rate at which ionizing radiation energy is transferred to soft tissue; also a method of expressing radiation quality
what permits us the assessment of potential biological damage based on number of ionizations taht occur in a specific distance? Linear Energy Transfer
LET is measured in _________ KeV per micron
LET equals ________ unless _________________________. zero, photon interacts with tissue and sets an electron in motion
LET of diagnostic x-rays is approximately ____________________. 3 KeV/micron of soft tissue
An increase in LET results in _________ and _________. an increase in bilogical response and and increase in the number of ionizations that occur and the probability of interaction with target a target molecule (DNA)
LET helps in radiation protection because ________________. it is used to determine the tissue weighting factor (W^R)
(High / Low)-LET is of greatest concern when internal contamination is possible. High
Low-LET: type of _________energy (_______and______), ______wavelenght and ________energy, interacts _______along the length of its track, ________all of its energy quickly, causes damage primarily through______ action, and causes the production of _______ electromagnetic, x-rays, gamma rays, short, high, randomly, doesn't use, indirect, free radicals
Which of the following interacts with DNA and cuases single strand breaks? -HighLET or LowLET Low LET
High LET: _______-like (possess _______and _______), cause ______ionization along track, lose energy ______, _______destructive than LowLET,ex. __________,and a____probability of interacting with DNA particle, mass, charge, dense, rapidly, more, alpha particles, greater
Relative Biological Effectiveness (RBE) as the LET of radiation increases, the ability to produce bilogic damage also increases
RBE equation Dose of standard rad. necessary to produce a given effect------------------------------------------------------Dose of test rad. necessary to produce the same effect
x-rays, gamma rays, and beta particles all have a quality factor of ________ 1
alpha particles and fast neutrons have a quality factor of ________ 20
Fractionation dicision of dose into multiple fractions sparing normal tissue through repair of sublethal damage between dose fractions and repopulation of cells
Fractionation increases tumor damage by _________ and _________ of tumor cells re-oxygenation, redistribution
Protraction dose delivered continuously over a long period of time but at lower dose rate; rarely used because of low effectiveness
Name two artificail modifiers oxygen and chemical agents
Tissue is more sensetive in a(n)______________ (anaerobic / aerobic) state. aerobic
free radicals possess ability to attack and damage organic molecules
Oxygen Enhancement Ratio (OER) ratio of radiation dose required to cause a particular biological response of cells or organisms in an oxygen-deprived environment to radiation dose required to cause an identical response under nromal oxygenated conditions
Low-LET equals ______ in Oxygen Enhancement Ratio increase
x-rays and gama rays have an OER of ________ when dose is high approximately 3.0
Low-LET radiation's biological effects are caused by ________actions(_________), and high-LET radiations produce biological effects by ______ actions (________ and _________) indirect, free radicals, direct, ionization, distruption of biomolecules
Alpha particles have an OER of ______ 1.0
Chemical agents either reduce or enhance cell's response; radiosensitizers, radioprotectors
radiosensitizers agents that enhance the effect of radiation, promote direct and indirect effects
halogenated pyrimidines intercalate between DNA strands and inhibit repair
radioprotectors agents used to make body less radiosensitive, generally influence indirect effects
types of radiosensitizers halogenated pyrimidines, methotrexate, actinomycin D, hydroxyurea, and vitamin K
types of radioprotectors sulfur, hydrogen bound molecules, custeine, and cysteamine
Hormesis an apparent threshold dosage in the atomic bomb survivors that corresponds to the amount of natural background radiation residents recieve for their lifetime in the US
Sensitivity and age... most sensitive before birth, decreases until maturity, increases agin with age
sensitivity and gender... males slightly more sensitive to radiation than females
about _______% of damage is irreparrable and the remaining ______% may be reparable over time 10, 90
radiation Dose Response Relationships mathematic relationship between various radiation dose levels and the magnitude of response observed
the 2 applications of radiation dose response relationships in radiology used to design thereapy routes, provide effects on low-dose irradiation
linear dose response relationships are ________ proportionate to dose directly
__________ and ________ effects follow the _______ ________ ______ response relationship leukemia, genetic effects, linear non-threshold dose
the type of dose response relationship that is generally used in radiation therapy to demonstrate high-dose cellular response non-linear
resuarch indicates that a low level of radiation will cause a ______ ________ response linear non-threshold
linear-quadratic nonthreshold curve as radiation dose increases, resonse tends to increase in an increasingly rapid manner
hypothetical curve used to calculate reponses by extrapolationof info from high levels of radiation to determine low dose of radiation
BEIR biological effects of ionizing radiation
we ASSUME bilogical response is _________ proportional to _________ doses directly, increased
Created by: 509420642