Chapter 7 Flashcards
Potentially harmful effects of ionizing radiation on living systems occur primarily at what level
Cellular
Biologic damage occurs from what types of radiation
Xrays
Gamma Rays
Alpha particles
Beta particles
Protons
What differs among various types of radiation
Charge, mass, and energy
What attributes determine the extent to which different radiation modalities transfer energy into biologic tissue
Charge, mass, and energy
What are the three concepts to understand how ionizing radiation causes injury to 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
LET
How is LET measured
keV/um
What are the 2 radiation categories of LET
Low-linear energy transfer
High-linear energy transfer
What type of radiation has a low-LET
Gamma rays
X-rays
What type of radiation has a high-LET
Alpha particles
Ions of heavy nuclei
Charged particles released from interactions between neutrons and atoms
Low-energy neutrons
Describes the comparative capabilities of radiation with differing LETs to produce a particular biologic reaction
Relative Biologic Effectiveness
What is the ratio to determine RBE
Dose (in Gy) of reference radiation to Dose (in Gy) of test radiation
What is typically used as the reference radiation to determine RBE
250 kVp x-rays
What is the Oxygen Enhancement Ratio
Radiation dose required to cause biologic damange without oxygen to Radiation dose required to cause biologic damage with oxygen
What is the OER for x-rays and gamma rays
3
Biologic damage resulting from exposure to ionizing radiation can be observed on what 3 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
Molecular
If a sufficient quantity of _______ cells are affected by ionizing radiation, entire body processes may be disrupted
Somatic
If radiation damages _____ cells, the damage may be passed on to future generations
Germ cells
What are the two classifications of ionizing radiation interactions on a cell
Direct action
Indirect action
Essentially all effects of irradiation in living cells result from _______ action
Indirect
Ionization of water molecules
Radiolysis
Effects of radiolysis
Production of free radicals
Production of unstable chemical reactions and biologic damage
Production of cell-damaging substances
Ionizing radiation interacts with DNA macromolecule, transfers energy, and ruptures one of the molecule’s chemical bonds
Single-strand break
Ionizing radiation interacts with DNA macromolecule, transfers energy, and ruptures additional breaks of the molecule’s chemical bonds
Double-strand break
Double-strand breaks occur more commonly with densely ionizing _____-LET radiation
High
Result is a cleaved or broken chromosome with each new portion containting an unequal amount of genetic material
Double-strand break
Alteration of the base sequence caused by ionizing radiation interacting with a DNA molecule
Mutation
Mutation is a/an ______ consequence (indirect/direct)
Direct
Chemical unions created between atoms by the single sharing of one or more pairs of electrons
Covalent cross-links
Covalent cross-links are initiated by ____ -LET radiation
High
Types of cross-link patterns
Intrastrand
Interstrand
Types of radiation-induced chromosome breaks in both somatic and reproductive cells
Chromosomal fragments
Chromosomal anomalies
-chromosome aberrations
-chromatid aberrations
Structural changes
Consequences to the cell from structural changes in biologic tissue
Restitution
Deletion
The chromosome break rejoins in the original configuration with no visible damage
Restitution
Part of a chromosome is lost at the next cell division, creating an acentric fragment
Deletion
Theory that there is a master, or key, molecule that maintains normal cell function is present in every cell
Target Theory
Damage to the cell’s nucleus reveals itself in what ways
Reproductive death
Apoptosis (interphase death)
Mitotic (genetic) death
Mitotic delay
Interference w/ function
What does the cell survival curve display
Sensitivity of a particular type of cell to radiation
Radiosensitive cells
Basal cells
Blood cells
Intestinal crypt cells
Reproductive (germ) cells
Radioinsensitive cells
Brain cells
Muscle cells
Nerve cells
______ enhances the effects of ionizing radition on biologic tissue by increasing tissue radiosensitivity
Oxygen
Law of Bergoine and Tribondeau established that radiosensitvity was a function of the _________ state of the cell receiving the exposure
Metabolic
Law of Bergoine and Tribondeau states that the radiosensitivity of cells is _______ proportional to their reproductive activity and _______ proportional to their degree of differentiation
Directly
Indirectly
Law of Bergoine and Tribondeau observed the effects of ionizing radiation on ____________ cells of rabbits that had been exposed to x-rays
Testicular germ cells
The most pronounced radiation effects occur in cells having the _______ maturity and specialization or differentiation, the _____reproductive activity, and the _______ mitotic phase
Least
Greatest
Longest
Equation for linear energy transfer
Total energy/total length of track
What is x-rays LET
3 keV/um
What is the result of the interaction of radiation with water
Formation of an ion pair
H+ and OH- and 2 free radicals H and OH
Chromatid break rejoins in the original configuration with no visible damage
Restitution
Chromosome is lost at the next cell divison, creating an acentric fragment
Deletion
The cell will die after exposure to ionizing radiation if the master, or key molecule (DNA) is inactivated in the process
Target Theory
