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RadioBio Ch33
| Question | Answer |
|---|---|
| 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 |
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