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unit 2 review

QuestionAnswer
What is LET? Measure of the rate at which energy is transferred from a particular type of radiation to soft tissue.
What is the LET for diagnostic x-rays? apprx 3 keV/m for diagnostic x-ray
What is OER? A measure of the increased radiosensitivity of tissue in the presence of oxygen (ratio of dose required if a cell is hypoxic/anoxic vs in oxygenated state)
Discuss the law of bergonie and tribondeau Radiosensitivity was a function of the metabolic state of the tissue being irradiated. More radiosensitive: Stem cells, younger tissues/organs, high metabolic activity, high proliferation rate.
What is RBE? RBE=dose of standard radiation to produce an effect, divided by dose of test radiation to produce the same effect.
What is protraction? Dose that is delivered continuously but at a lower dose rate.
What is fractionation? pts receive the radiation dose at the same dose rate but broken into equal values and given over time. radiation oncology pts receive prescribed doses fractionated daily.
What is deterministic (nonstochastic) response? Follow high dose exposure and demonstrate an early response. i.e. radiation induced skin burns represent a deterministic response.
Describe stochastic (probabilistic) response. follow low radiation exposure and appear as a late radiation response. i.e. cancer, leukemia, genetic effects.
Draw and properly label the four dose-response relationships we have discussed. Linear Nonthreshold. Linear threshold. Nonlinear Nonthreshold. Nonlinear Threshold.
What does a dose-response relationship describe? Describes the relationship btwn the dose that is received and the expected response.
A biologic reaction is produced by 600 rad of a test radiation. It takes 3600 rad of 250-kvp xray radiation to produce the same biologic reaction. What is the RBE of the test radiation? 6
Because high-LET types of radiation deposit more energy per unit length of biologic tissue traversed, they are: More destructive to biologic matter than low-LET radiation
A biologic reaction is produced by 7 Gy of a test radiation. It takes 21 Gy of 250-kvp xrays to produce the same biologic reaction. What is the RBE of the test radiation? 3
Which of the following are examples of stochastic effects? epilation, diarrhea, cancer, erythema, genetic defects caner, genetic defects
How do threshold and nonthreshold relationships differ in terms of radiation dose and biologic response? Threshold- there is a "safe" dose. Nonthreshold- there is no safe dose.
Gonvert 8000 rad to Gy 80 Gy
convert 0.96 Gy to rad 96 rad
the breakage of a back bone of the long-chain macromolecule, resulting in may smaller molecules is referred to as: Main Chain Scission (reduces viscosity)
The effect of macromolecule irradiation that results in spurs on the sides of the macromolecules, which can attach to neighboring molecules or other segments of the same molecule is: Cross linking
The disruption of single chemical bonds that can cause minor modifications to the molecule, causing the cell to malfunction, are called: Point Lesions
What is catabolism? Refers to the breaking down of melecular nutrients into smaller molecules with an accompanying release of energy.
What is anabolism? the construction or synthesis of macromolecules from smaller molecules.
What is the target theory? That each cell contains a target site on a target molecule, which must be hit in order to cause cell death. This master or target molecule is though to be DNA.
What is the difference btwn direct effect and indirect effect? A direct effect exists when the ionizing radiation interacts directly with the target molecule DNA. An indirect effect occurs when the interactions on some distant, noncritical molecule, resulting in free radical or toxic substances being formed.
When are cells most sensitive? Human cells are most radiosensitive in Mitosis, specifically metaphase
In which phase of the cell cycle is the cell the least radiosensitive? late S phase
What are fee radicals? Why can they be bad for cells? A free radical is an unchanged molecule that contains a single unpaired electron in the outer shell. They are highly reactive, unstable, and therefore exist with a lifetime of less than 1 ms
What does teh presence of oxygen due to the probability of a hit on the target molecule? Increases the probability of a hit on the target molecule.
Which molecules in the human body are most commonly directly acted on by ionizing radiation to produce molecular damage through an indirect action? water
is it possible to distinguish btwn an indirect and direct hit and explain. No, it is not possible to distinguish btwn the two types of hits.
Explain translation mRNA transfer its information to a tRNA molecule in the making of a protein; occurs at a ribosome in the cytoplasm.
explain transcription DNA transfers to codee to a mRNA molecule; occurs in the nucleus.
The dissociation of water molecules following irradiation is termed: radiolysis
What is the teory that toential benefits result from small amounts of radiation? Hormesis
What of the following have the highest LET? x-ray, alpha particles, gamma, beta particles ALPHA
What is the relationship btwn RBE & LET? direct
What is the RBE of diagnostic x-rays? One
Radiation induced genetic damage follows a ____ dose response relationship. linear, nonthreshold
Two free radical OH* can join to form ____ molecules, which are toxic to the cell. Hydrogen peroxide (H2O2)
If the target molecule is inactiviated, what will happen to the cell? it will die
The probability of a "hit" is increased in the presence of oxygen with low or high LET radiation? Low LET radiation (xrays, gamma)
What type of DNA damage is NOT reversible? Change or loss of a nitrogenous base.
How can you recognize a free radical? * (asterisk)
Created by: rieste
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