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41 Cards in this Set

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The branch of biology with effects of ionizing radiation on living systems.
Radiation Biology
Ineraction of radiation in cells is a matter of what?
chance
Can damage by radiation be repaired?
yes
Radiation deposits energy in a cell in a _________ fashion.
random
Is radiation damage any different than normal trauma?
no
Do biologic changes appear immediately?
no
What does the length of latency depend on?
dose given, as well as to biological characteristics of the irradiated.
What 3 concepts determine severity of injury?
1. Linear Energy Transfer

2. Relative Biologic Effectiveness

3. Oxygen Enhancement Ratio
What has a low let?
external electromagnetic radiations such as x-rays and gamma rays
What has a high let?
particles that possess substantial mass and charge such as alpha particles.
A large QF= what?
large rbe
What is the oxygen enhancement ratio?
Radiation is more damaging to tissue in an aerobic state.
When ionizing radiation interacts with a cell, ionizations and excitations are produced where?
targets(dna) or medium which organelles are suspended(water)
Radiation damage is seen on what 3 levels?
molecular, cellular, and organic
Any visible radiation induced injuries always begin with damage at what level?
molecular
with somatic cell involvement what can be disrupted?
entire body
When germ cells are damaged what are the affects?
genetic mutations of future generations
What is direct action?
when photon hits DNA
What is indirect action?
photon hits H2O, causes chemical reaction that is toxic to DNA
Are the effects of direct action and indirect action the same?
yes
What percentage is indirect action?
95%
Break in backbone of one chain of DNA- repairable
Single Strand Break
widely spaced , may repair with difficulty or may result in cell death?
Double Strand break
causes irrepairable damage or cell death
Double strand break on same rung
change or loss of a base casues mutation which cell divisions result in daughter cells with incorrect genetic information.
Nitrogenous Base damage
Effects of ionizing radiation on chromosomes deals with primarily what type of x-ray modality?
radiation therapy
If radiation damage is severe what may be detected?
visible chromosome aberrations
What are the effects of ionizing radiation on chromosomes? and explain them.
1. Terminal delection
2. Dicentric formation
3. ring formation4.
4. radiation induced reicprocal translocations.
States that there are targets in a cell, all of which must be "hit" to kill the cell. If one target is not hit, the cell will survive and repair the damage. As dose increases, the more damage accumulates and the cell dies.
Target theory
What are the main concepts of target theory?
there is a key molecule that is deactivated
can happen with direct or indirect hit
when oxygen is present, more probability of a hit
What are the two factors dealing with the law of bergonie and tribondeau?
1. x-rays appeared to destroy the cells of a malignant tumor without permanently damaging the healthy tissue.
2.Some tissues were damaged by doses that did not appear to harm other tissues.
What hypothesis did Bergonie and Tribondeau come up with?
1. The stem cells are radiosensitive
2. Younger tissues are more sensitive
3. When metabolic activity is high, radiosensitivity is high
4. As proliferation rate increases, radiosensitivity increases. embryo-fetus most sensitive
5. Undifferentiated cells are more sensitive.
what cells are highly radiosensitive?
lymphocytes, spermatogonia, erythroblast, intestinal crypt cells
What type of cells have intermediate radiosensitivity?
endothelial, osteoblasts, spermatids, fibroblasts
What ype of cells have low radiosensitivity?
muscle, nerve
responses such leukemia cancer and genetic effects referred to as stochastic.
Linear non threshold
certain dose will show an effect such as skin erythema referred to as nonstochastic.
Linear non threshold
Factors on which amount of somatic and genetic damage depends.
1. Quantity of ionizing radiation(mas)
2. Ability to cause ionization(QF)
3. Amount of body exposed(collimation)
4. Specific parts exposed(shielding)
Before radiation monitors how was exposure measured?
blood test
In humans, a response to radiation that occurs within months from the time of exposure is called an _______ __________.
Early Effect
Effects that become more severe with increased radiation dose are __________ and there is usually a close _________.
deterministic, threshold