Radiation Biology And Protection Flashcards
(49 cards)
He discovered the natural radioactivity in 1986 by observing radiation induced erythema on his abdomen from a vial of radium he carried in his best pocket during a trip to london
Becquerel
“Becquerel burn”
Biological effect of radiation in which the probability of the effect occurring increases with those rather than its severity
Stochastic effect
Example: radiation induced leukemia
Radiation biologic effect in which the severity of the injury increases with those rather than its probability of occurrence
Deterministic
Examples are skin erythema fibrosis and hematopoietic damage
Threshold those is an approximation of the laws that would likely result in the specified effect
Interaction of radiation with tissue by production of energetic electrons includes:
Excitation, ionization and thermal heating
In low energy electrons, energy deposition along the shorter tracks are referred to as
Spurs
With diameters approximately 4 to 5 nm
Complex cluster damage in which groups of several damage nucleotides occur within one or two helical turns of dna is a hallmark of:
Ionizing radiation induced dna damage
Radiation interaction wherein the change is said to be due to biological macromolecules such as dna rna or protein becoming ionized or excited by an ionizing particle or photon passing through or near it
Direct interaction
Radiation interaction wherein the change is due to damage from medical irridiation caused by interaction with water molecules
Indirect interaction
These are extremely reactive chemical species that can undergo variety of chemical reactions
Free radicals
Hydrogen donation from thiol compounds will produce a much less reactive or damaging ____
Thiyl Radical
In the presence of oxygen, repair is inhibited by chemical transformation into _______
Peroxiradical
This states that beyond approximately 100 kev per per millimeter in tissue the RBE decreases with increasing LET
Overkill effect
Overkill or wasted dose refers to the deposition of radiation energy in excess of that necessary to produce the maximum biological effect.
Structural changes induced by ionizing radiation
Hydrogen bond breakage
Molecular degradation
Intermolecular and intramolecular cross linking
Chromosome breaks produced by radiation do occur and can be observed microscopically during
Anaphase and metaphase
Chromosomal damage that occurs before dna replication
Chromosome aberrations
Whereas that occurring after dna synthesis is called chromatid aberrations
These are physical or chemical factors that exist before and/or at the time of irradiation
Conditional radiosensitivity
Mitigated by observing intervals between doses
Defined as the dose of radiation that produces a given biological response in the absence of oxygen divided by the dose of ignition that produces the same biological response in the presence of oxygen
Oxygen enhancement ratio (OER)
DESCRIBES THE RELATIVE EFFECTIVENESS OF RADIATION TO PRODUCE DAMAGE AT VARIOUS OXYGEN TENSIONS
This includes biological factors that are characteristics of the cells themselves such as mitotic rate the degree of differentiation and the stage of the cell cycle
Inherent radiosensitivity
The law of Bergonie and Tribondue states that
Radio sensitivity is greatest for doses that
-have a high mitotic rate
-have a long mitotic future
-are undifferentiated
General cells are most sensitive to radiation during
M phase
Gap between s and g2
Phenomenon in which irradiated cells or tissues can produce the literacy effects on non irradiated cells
Bystander effect/Abscopal/out of field effect
Epilation or temporary hair loss can occur
Approximately 3 weeks after exposure to 3 to 6 Gy radiation dose
With the growth beginning approximately 2 months later and complete within 6 to 12 months
Manifestations of moderately large doses approximately 40 Gy over a period of 4 weeks or 10 Gy in a single dose
Intense erythema followed by an acute radiation dermatitis and moist gas formation
Characterized by edema, dermal hypoplasia, inflammatory cell infiltration, damage to vascular structures and permanent hair loss
Repeated low level exposures 10 to 20 mGy per day where the total dose approaches 20Gy or more
Chronic radiation dermatitis
