Chapter 7- Molecular and Cellular Radiation Biology Flashcards
Branch of biology concerned with the effects of ionizing radiation on living systems
Radiation Biology
what does Radiation Biology include of:
Sequence of events occurring after the absorption of energy from ionizing radiation
Action of the living system to make up for the consequences of this energy assimilation
Injury to the living system that may be produced
Damages living systems by ionizing the atoms comprising the molecular structure of these systems
IONIZING RADIATION
Biologic damage begins with the ionization produced by various types of radiation such as
Xrays
Gamma rays
Alpha particles
Beta particles
Protons
TRUE OR FALSE:
Ionized atoms will not bond properly in molecules
True
what varies among the different types of radiation
Charge, mass, and energy vary among the different types of radiation
**These attributes determine the extent to which different radiation modalities transfer energy into biologic tissue.
Three important concepts help us to understand the way ionizing radiation causes injury and how the effects may vary in biologic tissue.
Linear energy transfer
Relative biologic effectiveness
Oxygen enhancement ratio
The average energy deposited per unit length of track by ionizing radiation as it passes through and interacts with a medium along its path
Linear Energy Transfer (LET)
What does LET stand for
Linear Energy Transfer
what units is LET described in
Is described in units of keV/μm
Is a very important factor in assessing potential tissue and organ damage from exposure to ionizing radiation
LET
Radiation categories according to LET
Low-linear energy transfer radiation
High-linear energy transfer radiation
Examples of Low LET radiation
Gamma Rays and Xrays
Examples of high LET Radiation
-alpha particles
-ions of heavy nuclei
-charged particles released from interactions between neutrons and atoms
-low energy neutrons
Describes the relative capabilities of radiation with differing LETs to produce a particular biologic reaction
Relative Biologic Effectiveness (RBE)
What does RBE stand for
Relative Biologic Effectiveness
is the ratio of the dose of a reference radiation (conventionally 250-kVp x-rays) to the dose of radiation of the type in question that is necessary to produce the same biologic reaction in a given experiment. The reaction is produced by a dose of the test radiation delivered under the same conditions.
RBE of the type of radiation being used
The ratio of the radiation dose required to cause a particular biologic response of cells or organisms in any oxygen-deprived environment to the radiation dose required to cause an identical response under normal oxygenated conditions
Oxygen Enhancement Ratio (OER)
when the radiation dose is high, how much OER does xrays and gamma rays have
In general, x-rays and gamma rays have an OER of about 3.0 when radiation dose is high.
when the radiation dose is low, how much is the OER
ER may be less (approximately 2.0) when radiation doses are below 2 Gyt.
what is the OER ratio
radiation dose required to cause biologic responce without O2 over Radiation dose required to cause biologic response with O2
In living systems, biologic damage stemming from exposure to ionizing radiation may be observed on three levels
Molecular
Cellular
Organic systems
Any visible radiation-induced injuries of living systems at the cellular or organic level always begin with damage at what level
at the molecular level.
results in the formation of structurally changed molecules that may impair cellular functioning.
Molecular Damage