chapter 7 EXAM 3 Flashcards
what is the goal of radiobiologic research
the accurate description of the effects of radiation on humans so that radiation can be used more safely in diagnosis and more effectively in therapy
generalizations about radiation effects on living organisms #1
the interaction of radiation in cells is a probability function or a matter of chance
ionizing radiation does not seek out certain cells.
generalizations about radiation effects on living organisms #2
the initial deposition of energy occurs very rapidly
generalizations about radiation effects on living oragnisms #3
radiation interaction in a cell is nonselective
energy is deposited randomly
generalizations about radiation effects on living organisms #4
the visible changes in the cells, tissues and organs due to ionizing radiation are not unique. They can’t be distinguished from damage produced by other types of trauma
cancer is cancer
generalizations about radiation effects on living organisms #5
the biologic changes in cells and tissues resulting from radiation occur only after a period of time. The length of time depends on the initial dose and varies from weeks or even years
3 radiation energy transfer determinants
- Linear energy transfer (LET)
- relative biologic effectiveness (RBE)
- oxygen enhancement ratio (REO)
characteristics of ionizing radiation
charge
mass
energy
Linear Energy Transfer (LET)
the measure of the rate at which energy is transferred from ionizing radiation to soft tissue
LET is expressed in
kiloelectronvolts per micrometer
the LET of diagnostic xrays is
3 KeV/micrometer
considered Low LET
LET is a factor in
assessing potential tissue and organ damage from exposure to ionizing radiation
when LET increases,
the likelihood of biologic response increases
T or F
LET helps determine radiation weighting factors
true
radiation is divided into 2 categories according to LET
- low LET
2. high LET
Low LET
xrays and gamma rays
electromagnetic radiation is sparsely ionizing therefore it is Low LET
when interacting with biologic tissue Low LET causes damage primarily
through indirect action which involves the production of free radicals
free radicals
a solitary atom or a combo of atoms that behave as extremely reactive single entities as a result of the presence of an unpaired electron
Low LET radiation generally causes what kind of damage to the DNA
sublethal damage
repair enzymes revers the damage
direct action means
it will hit the nucleus of a cell
indirect action means
it will hit water
high LET includes
particles that possess large mass and charge
high LET causes
dense ionization along its length of track and more likely to interact with biologic tissue
way more destruction
examples of high LET radiation
alpha particles
ions of heavy nuclei
low energy neutrons
charged particles released from interactions between neutrons and atoms