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Radiation with sufficient energy to seperate an electron from its atom
ionizing radiation
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What are the 2 major groups of radiation sources?
External Beam therapy machines
brachytherapy sources
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Which source of radiation use gamma rays, x-rays, and sometimes electrons
external beam
such as cobalt teletherapy units or linear accelerators
-
What source od radiation use gamma rays & x-rays from sources such as cesium-137, iridium-192, and iodine-125.
brachytherapy
-
**
Consist of 2 protons and 2 neutrons and therefore are simply helium neclei
Alpha Particles
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They are emitted from unstable heavy nuclei such as radium or radon during the decay process
Alpha particles
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**
Can only travel short distances.
--most can be stopped by a sheet of paper, but they produce intense ionization and are therefore high linear energy transfer (LET) radiation
Alpha particles
-
They are extremely hazardous if ingested or inhaled but are less dangerous if the exposure is external
Alpha particles
-
**
Electrons emitted by nucleus
They may be either negatively or positively charged
Beta particles
-
Negatively charged beta particles are called
negatron
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positively charged beta particles are called
positrons
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_______ are not stable and may exist for only very short periods of time
positrons
-
**
Whenever beta particles are emitted, they are accompanied by a small, massless, chargeless particles known as the
neutrino
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metals may be used for shielding, but ____ radiation may result
bremsstrahlung
-
**
The probability of bremsstrahlung x-ray production is ___
___ to the square of the atomic number of the absorber and ___ ___ to the square of the mass of the incident particle
directly proportional
inversely proportional
-
**
Bremsstrahlung radiation is much more likely to occur with ____ particles than with ____ particles
Beta
Alpha
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____ & ____ are both forms of electromagnetic radiation (photons)
x-rays & gamma rays
-
**
____ have no mass and no charge
photons
-
**
____ are photons emitted froma nucleus
gamma rays
-
**
_____ are extranuclear and result from rearrangements
within the electron shells or from bremsstrahlung radiation
x-rays
-
**
Except for their origin, there is no difference between ___ and ____.
xrays & gamma rays
-
NOTE:
xrays, gamma rays, and electrons are the most common types of ionizing radiations
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It is estimated that ___% of the radiation exposure of the United States population comes from natural background sources
82%
-
What are the amounts of radiation exposure for
natural _____%
man made ____%
82
18
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What are the 3 sources of natural background radiation?
Cosmic Rays
Terrestrial Exposure
Internal Exposure
-
**
The primary cosmic rays interact with molecules in the atmosphere to create reactive agents known as _____.
secondary particles
-
Whhat natural radiation originates from nuclear reations in spce or from our own sun
Cosmic Rays
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Exposure is _____ at the polar regions than at the equator
higher
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Latitude, solar cycels, and other factors may account for a variation of ___% in exposure.
The intensity varies even more with increasing elevation
10%
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What natural source is made up of small amounts of long lived isotopes of uranium, thorium, and radium among others
terrestrial radiation
-
**
The ___ ___ ___ estimates that radon exposure is the 2nd leading cause of lung cancer in the U.S. (following smoking)
- EPA
- Enviromental Protection Agency
-
**
___ ___ results from the radioactive material that are normally in our bodies
Internal exposure
-
What are examples of man-made sources?
xrays - nuclear medicine procedures, TV, tobacco products, nuclear reactors, fuel cycle, & fallout from above ground nuclear weapons testing
-
**
___ is defined as the amount of ionization produced by photons in AIR per unit mass of air
Exposure
-
**
___ ___ is defined as the energy absorbed per unit mass of any material
absorbed dose
-
___ Gy = ___ cGy = ___ rad
-
**
___ ___ takes into account the fact that different types of radiation produce different amounts of biologic damage
dose equivelent
-
Alpha particle & neutrons are __ ___ LET radiation and therefore have a greater biologic efect than x-rays
high
-
NOTE:
To account for differences in biologic response, each type of radiation is assigned a quality factor
-
What is the traditional unit of:
Exposure:
Absorced Dose:
Dose Equivelent:
Activity
-
The QF of
xrays & gamma rays=
fast nuetrons=
-
**
___ ____ ___ takes into account the effect of irradation of only part of the body or the effect of non uniform irradation of the body
effective dose equivelent
-
NOTE:
The units for the effective dose equivelent are also the Sievert & the REM
-
**
___ is the rate at which a radiaoactive isotope undergoes nuclear decay
activity
-
NOTE:
The traditional unt of activity is the curie (CI)
This SI unit is the becquerrel
-
What are the 2 kinds of gas-filled detectors that may be found in a RT dept.
ionization chamber
Geiger Muller
-
** When ionization chambers re properly calibrated their accuracy approaches ___% which makes them suitable for measurement of the radiaiton output of therapy equipment
2%
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What form of ionization chamber is used for personal monitoring
the pocket dosimeter
-
Note:
becuase ionization chambers are not very sensitive, they are not suitable for the detection of very low levels of radiation or radiation contamination
-
** NOTE
Because of their sensitivity, G-M detectors are best for finding contamination and other low levels of radiation
-
**
Because of their small size, ___ ___ are widely used to measure radiation in a number of applications
TLD's thermoluminscent dosimeters
-
**
Thermoluminscent materials give offlight when heated
-
The atomic number of LIF is close to that of tissue
-
With proper care, doses can be measured with an accuracy of approximately ___ %
5%
-
**After development, x-ray film exposed to radiation turns black.
This amount of blackness is called the ___ ___
optical density
-
NOTE:
The optical denisty is the amount of radiation received by the film
-
**
The primary task of ___ ___ is to analyze the existing data related to radiation exposure and to access the radiobiologic risk associated with those exposures
advisory agencies
-
**
It is the role of the ___ ___ to license users of radioactive materials & radiaiton-producing equipment, inspect such users, and enforce the laws
regualtory agencies
-
**
many states have entered into agreements concerning licensing, inspection and enforcement with the NRC have become ___ states
agreement
-
effects have no threshold and for which the probability of occurance is a function of dose
Stochastic
ex: cancer induction, genectic effects and embryologic & teratogenic effects
-
*
___ effects are those for which a threshold exist and for which the severity of the effect increases with dose
non-stochastic
- ex: erythema (skin reddness),
- epilation (hair loss)
- cataract formation
- infertilty
-
What are the significant long term effects related to exposure to radaition?
nonstochaltic & stochastic effects
-
WHat does the LD 50/30 means?
lethal dose or 50% of the population in 30 days
-
we have a far greater knowledge of the effects of high doses than those of low doses.
In sufficiency high quanitites, radiation can be lethal. A single whole body dose of 4.5 ___ is lethal for ___5 of the exposed population with in ___ days of the event
-
what agency oversees the use of isotopes produced in nuclear reactors.
These isotopes are currently used in nuclear med dept, labs as sources for teletherapy & brachytherapy
- NRC
- nuclear regulatory commission
-
NOTE:
TLD's are also used for mail intercomparision of therapy units calibration, in ring badges used for personal monitoring, and for measurements of enviromental levels of radiation.
-
A typical ___ ___ has a slot in which the film may be placed and several thin, metal, filters that surround portions of the film.
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