Ch 30 Fundamental Principles of Radiobiology Flashcards
What are the different names for Stem Cells?
- Immature Cells
- Precursor
- Undifferentiated Cells
What type of cells are sensitive to Radiation?
Immature cells
What does proliferation mean?
The splitting/ dividing of cells
What happens to cells the more mature they are?
They become more resistant to radiation
What is the law needed to understand the biologic effects of radiation?
The Law of Bergonie and Tribondeau
What are the Laws of Bergonie and Tribondeu?
- Stem cells are radiosensitive, the more mature a cell, the more resistant to radiation
- The younger the tissue, the more radiosensitive
- When metabolic activity is high, radio sensitivity is high
- As proliferation increases, so does radio sensitivity
What is the radiosensitvity of cells proportional to?
Their reproductive activity
The radio sensitivity is inversely proportional to:
Their degree of differentiation
When does the most pronounced radiation effects in cells occur?
When they have the least maturity and specialization or differentiation
What law mainly has application in Radiation Therapy?
The law of Bergoine and Tribondeau
What type of cell is more sensitive to radiation, immature or mature cells?
Immature cells
What does LET stand for?
Linear Energy Transfer
What does RBE stand for?
Relative Biologic Effectiveness
What does OER stand for?
Oxygen Enhancement Ratio
What are the (3) attributes that determine the extent to which radiation energy is transferred into biologic tissue?
LET
RBE
OER
What is the rate radiation energy is transferred into soft tissue in diagnostic x-rays?
3 keV
What is an important factor in assessing potential tissue and organ damage from exposure to ionizing radiation?
LET
What two categories, can LET be divided into?
High and Low
What attribute is a method of expressing radiation quality?
LET
What are examples of Low- LET radiation?
External Electromagnetic Radiations
- X-rays - Gamma rays
Does low LET relinquish their energy quickly or over a sustained amount of time?
Over time
How does low LET cause damage?
Primarily through indirect action; involves free radicals
What does High LET radiation include?
Particles that possess substantial mass and charge.
What are some examples of High LET radiation?
- Alpha particles
- Ions of heavier nuclei
- Beta radiation
How well does High LET radiation penetrate?
Not very well,
It gives up energy quickly
What type of LET causes the most damage?
High
What increases as LET increases?
The ability of ionizing radiation to produce a biologic response
Does beta radiation have more energy than x-rays?
No, beta particles just lose their energy into the tissue faster
What escalates as the LET of radiation increases?
Biologic damage produced by radiation
What are some Biologic Factors that Affect Radiosensitivity?
- Oxygen effect (OER)
- Age (consistent with the law of B&T)
- Recovery
- Chemical agents
- Hormesis
What does Hormesis mean?
A little bit of radiation is good for you
What is OER?
- Oxygen Enhancement Ratio
- The ratio of the radiation dose required to cause a particular biologic response of cells in an oxygen deprived environment
What is more sensitive to radiation, a fetus or a newborn?
A fetus
Who is more sensitive to radiation, a newborn or a young child?
A newborn
What happens to radiosensitivity in teens?
It decreases
At what age specifically in teens does radiosensitivity decrease the most?
18 y/o
Radiosensitivity stabilizes as we age. At what age does it begin to increase again?
70 y/o
When are breast cancer rates increased?
When children are exposed to radiation at a time when breast tissue is developing
What are growing children 2-3 times more radiosensitive than adults in developing?
Leukemia
What does Dose Protraction mean?
Continuous dose of radiation at a lower rate, Bigger dose in a smaller amount of time
Define Dose Fractionation:
Divided doses of radiation given at a low rate, more of a treatment plan over time
Define Nonthreshold:
Small dose could cause an effect
Define Threshold:
Level is reached below, which no effects are observed
Curves are either:
Linear or non linear
As dose increases:
So do the effects
What is another name for Deterministic radiation responses?
Nonstochastic
What is a Hematologic disorder?
Blood
What does Epilation mean?
Loss of hair
What does Erythema mean?
Redness of skin
What does Desquamation mean?
Shedding of outer layer of skin
Following a high dose exposure to radiation that appeared within minutes, hours, days or weeks after exposure would be an example of:
Deterministic/ Nonstochastic
What are some examples of Deterministic/ Nonstochastic effects?
- Cytogenetic damages
- Hematologic depression
- Skin damage
- Epilation
- Desquamation
- Erythema
What is another name for a Stochastic response?
Probabilistic
What is the name for responses that appear years later:
Stochastic/ Probabilistic
What are some examples of Stochastic/ Probabilistic responses?
- Cancers
- Leukemia
- Genetic Disorders
