Terms in this set (27)
LET, RBE, & OER
Factors that influence the effects of radiation in
tissue: (HINT: 3)
Linear energy transfer (LET)
-Average energy deposited per unit length of track
-As it increases, so does the risk of biologic damage to tissue
-Xray, Gamma ray
-Can be more penetrating
-less ionizing/ biologic damage
-Cell damage caused by INDIRECT action with production of FREE RADICALS
-Damage to DNA occurs rarely (single strand breaks) and is usually not lethal
-Particulate radiation with substantial mass and/or charge (alpha particles and neutrons)
-More ionizing/biologic damage
-Short length of track and cannot penetrate as far
-Damage be very destructive to biologic matter (double-strand breaks)
Relative Biologic Effectiveness (RBE)
-Relative capabilities of radiation with differing LETs to produce a biologic reaction
-Compares a dose of a specific type of radiation to that of 250 kVp of Xrays
Oxygen Enhancement Ratio (OER)
The ratio of the radiation dose required to cause a particular biologic response of cells in an oxygen-deprived environment to the radiation dose required to cause an identical response under normal oxygenated conditions.
__________ LET radiation (particulate radiation) has an OER of 1 because oxygen plays no role in direct ionization reactions
LET radiation damage is caused indirectly by production of free radicals and their interaction with oxygen in the tissue
biologic damage occurs as a result of ionization of atoms on essential molecules
effects produced by free radicals that are created by the interaction of radiation with water
2/3 of radiation-induced damage is created by
Short lived atom that has an unpaired electron but no net electrical charge. They are highly interactive because unpaired electron will pair up with another electron even if it has to break a chemical bond.
Is made of 2 hydroxyl radicals that combine and is poisonous to the cell.
Is a combination of a hydrogen radical and oxygen which causes biologic damage
Single strand break
-Rupture of one side of the sugar-phosphate rails
-Point-mutation results in gene abnormality
-Common with low-LET radiation
-Often repairable by the repair enzymes
Double strand break
-rupture of both sides of the sugar-phosphate rails
-More common with high-LET radiation
-Not easily repaired
-Sometimes fatal to the DNA and therefore the
Double strand break in the same rung
-2 interactions on each sugar-phosphate rail of
-Broken chromosome can have unequal amounts of genetic material
-Cell division will result in inadequate
number of chromosomes in future
generation cells leading to MUTATION
-Can result in cell death or genetic
Is enough DNA changes occur, changes in chromosome structure will be visualized in _____________.
When referring to broken fragments of chromosomes, the breaks then rejoin and there is no visible damage.
When referring to broken fragments of chromosomes, part of the chromosome (chromatid) is lost at the next cell division, leading to cell mutation
When referring to broken fragments of chromosomes, visual defects occur leading to different malformations and cell mutation.
Broken end arrangement without visual damage to chromatids
When referring to broken fragments of chromosomes, the genetic material has been rearranged but appears normal leading to cell mutation.
-describes the notion that damage from a single hit to a vital molecule is often repairable and therefore insignificant
-It explains both cell death and nonfatal cell abnormalities caused by radiation exposure
-Hits are random events and must occur on the DNA to be biologically effective
Cellular effects of radiation
-Interferes with function
• Law of Bergonie & Tribondeau:
The law that states the radiosensitivity of cells is directly proportional to their reproductive activity and inversely proportional to their degree of differentiation
dose that produces death in 50% of subjects within 60 days (3.0 to 4.0 Gy)
the most radiosensitive cell in the body
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