Radiation Biology And Protection Flashcards
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
Temporary and permanent sterility can occur after acute doses of approximately
Temporary 500 mGy
Permanent 6 Gy
Most common histologic type of radiation induced thyroid cancer
WELL DIFFERENTIATED PAPILLARY THYROID CARCINOMA
Defined as the dose required per generation to double the spontaneous mutation rate
DOUBLING DOSE
Most sensitive times of exposure for humans during preimplantation
12hrs after conception (one cell stage)
30-60hrs (1st two divisions)
Spontaneous abortion during preimplantation period requires _____ dose
50-100mGy
After implantation it requires dose > 250mGy
Primordial radionuclides:
Potassium 40 Half life= 1.28 x 109yrs)
Uranium 238 Half life= 4.51 x 109yrs)
Thorium 232 Half life= 1.41 x 1010yrs)
Tobacco leaves and cigarette smoke contains this 2 alpha-emitting radionuclides
Pb-210, Po-210
Consists of a small sealed packet of radiation sensitive film, similar to dental x-ray film, placed inside a special plastic holder and uses film emulsion with Silver bromide grains
FILM BADGES
Contains storage phosphors in which a fraction of the electrons raised to excited states by ionizing radiation, become trapped in excited states
Thermoluminescent dosimeter
Most commonly used tld material for personnel dosimetry
LiF (Lithium fluoride)
Osm is similar to that of tld except that the release of trap electrons and light emission are simulated by laser light instead of heat. It utilizes this compound which is capable of detecting losses as low as 10ùSv
Crystalline aluminum oxide activated with carbon
Relatively new technology in which a non-volatile analog memory cell surrounded by a gas filled ion chamber is used to record radiation exposure
Direct ion storage dosimeter
Disadvantages includes inability to measure beta radiation exposure
This principle states that any decision that alters the radiation exposure situation should do more good than harm, that is yield an individual or societal benefit that is higher than the detriment it causes.
Principle of justification
This principle states that in plant situations the total dose to any individual from all the regulated sources should not exceed the appropriate regulatory limits.
Principle of limitation of maximum doses
What are the four principal methods by which radiation exposures to persons can be minimized
-reducing time of exposure
-increasing distance
-use of shielding
-controlling contamination by radioactive material
This law states that exposure rate decreases as the distance from the source is squared
Inverse square law
Give the shielding design goal for controlled areas uncontrolled areas and radiographic film storage room
Controlled area 5 mGy per year
Uncontrolled area should be 1 mGy per year
Film storage area should be less than 0.1 mGy
Gonadal shield must attenduate primary nation and its thickness must be equivalent to at least
0.5 mm of lead
Alara stands for
As low as reasonably achievable
In evaluating a pregnant and possible pregnant patients the pregnancy test should be obtained within ____ hours before examination
72 hours
This is the most common encountered tissue reaction following high dose image guided interventional procedure (deterministic effect)
Skin damage
In using direct ion storage decimeter to measure the radiation exposure, which of the following is a disadvantage of this technology?
A. Broad dose and photon energy response range
B. Unlimited real time dose readings without the need for a special reader
C. Elimination of the periodic distribution and collection of dosimeters
D. The current version cannot be used to measure exposure to beta radiation
D
Acute radiation dose for neurovascular syndrome
> 50 Gy
Among the personnel monitoring methods this provide a permanent recording
A. Film badge
B. Osl
C. Tld
D. Pocket dosimeter
A
Pocket dosimeter a type of direct ion storage device that allows direct reading of exposure however it cannot measure beta radiation
Osl have the advantage to distinguish static and dynamic exposures and the ability to reread
Tld more common but more expensive than film. Used for phantom and patient dosimetry
P
