-
consist of 2 protons and 2 neutrons and are therefore simply helium nuclei
alpha particles
-
what are emitted from unstable heavy nuclei such as radium or radon during the decay process
alpha particles
-
because of their charge and heavy mass, what travel only short distances (can be stopped by a sheet of paper)
alpha particles
-
what produce intense ionization and are therefore high linerar energy transfer (High LET) radiation
alpha particles
-
what are extremely hazardous if ingested or inhaled but are less dangerous if the exposure is external (have greater biologic effect)
alpha particles
-
what is High LET
High Linear Energy Transfer
-
electrons emitted by the nucleus
beta particles
-
may be negatively charged (negatron) or postively charged
beta particles
-
negatively charged
negatron
-
positively charged
positron
-
not stable and may exist for only very short periods of time
positrons (beta particles)
-
emitted and accompanied by a small massless, chargeless particle known as the neutrino
beta particles
-
small massless, chargeless particle
neutrino (beta particles)
-
which particles have the same rest mass as an electron and are usually emitted frome the nucleus with high velocities
both types of particles
-
what may be used for shielding, but bremsstrahlung radiation may result
metals (beta particles)
-
bremsstrahlun x-ray production is _____ proportional to the square of the _____ ____ of the absorber
- directly proportional
- atomic number
-
bremsstrahlung x-ray production is ____ proportional to the square of the mass of the _____ particle
- inversely proportional
- incident particle
-
Thus, ____ _____ is much more likely to occur with beta particles then with alpha particles
bremsstrahlung radiation
-
bremsstrahlung radiation is much more likely to occur with ____ particles, than with ____ particles
-
rays both forms of electromagnetic radiation
x-ray and gamma rays
-
electromagnetic radiation
photons
-
have no mass and no charge
photons
-
photons emitted from a nucleus
gamma rays
-
extranuclear and result from rearrangements within the electron shells or from bremsstrahlung radiation
x-rays
-
gamma rays are emitted from
nucleus
-
x-rays are within
electron shells
-
except for their origins, there is no difference between ____ and ____
x-rays and gamma rays
-
the most common types of ionizing radiation used in radiation therapy
- x-rays
- gamma rays
- electrons
-
radiation with sufficient energy to separate an electron from its atom
ionizing radiation
-
alpha particles:
charge number
atomic mass
origin
-
beta particles (negatron):
charge number
atomic mass
origin
-
beta particles (positron):
charge number
atomic mass
origin
-
Neutrinos:
charge number
atomic mass
origin
-
x-rays:
charge number
atomic mass
origin
-
gamma rays:
charge number
atomic mass
origin
-
-
-
-
-
-
% for nuclear medicine
4%
-
estimated % of all radiation exposure of the u.s. population comes from natural background sources
82%
-
estimated 82% of all radiation exposure of the u.s. population comes from ___ ___ ___
natural background sources
-
3 sources of natural background radiation
- cosmic rays
- terrestrial radiation
- internal
-
rays that bombard the earth
cosmic rays
-
radiation that emanates from radioactive materials naturally occurring in the earth
terrestrial radiation
-
deposits of radionuclides in our bodies
internal
-
originate from nuclear reactions in space or from our own sun
cosmic rays
-
____ ____ interact with molecules in the atmosphere to create other reactive agents known as ____ particles
- cosmic rays
- secondary particles
-
with cosmic rays, exposure is ____ at the polar regions than at the equator
higher
-
with cosmic rays latitude, solar cycles and other factors may account for a variation of ___ % in exposure
10%
-
earth is made up of hundreds of materials, many of which are naturally radioactive
terrestrial radiation
-
terrestrial radiation are naturally radioactive because of teh presence of small amounts of long-lived isotopes of ____, ____, and ____.
-
the largest exposure to terrestrial radiation involves
radon
-
may be particularly harmful because it is an easily inhaled gas
radon (terrestrial radiation)
-
what is EPA
Environmental Protection Agency
-
estimates that radon exposure is the second leading cause of lung cancer in the u.s.
environmental protection agency (EPA)
-
results from the radioactive materials that are normally present in our bodies
internal exposure
-
the amount of ionization produced by photons in air per unit mass of air
exposure
-
traditional unit for exposure is
Roentgen
-
the energy absorbed per unit mass of any material
absorbed dose
-
1 Gy=100cGy=100 rad
absorbed dose
-
takes into account the fact that different types of radiation produce different amounts of biologic damage
dose equivalent
-
example of dose equivalent ____ ____ and ____ are high-LET radiation and therefore have a greater biologic effect than x-rays
-
takes into account the effect of irradiation of only part of the body or the effect of nonuniform irradiation of the body
effective dose equivalent
-
the rate at which the radioactive isotope undergoes nuclear decay
activity
-
traditional unit of activity is
curie (Ci)
-
3.7 x 1010 disintegrations per second
activity (Ci)
-
the SI unit is ____ which is 1 disintegration per second in activity
Becquerel (Bq)
-
traditional unit for exposure
1 roentgen
-
traditional unit for absorded dose
-
traditional unit for dose equivalent
100 rem
-
traditional unit for activity
1 Ci
-
quality factor (QF) for x-rays and gamma rays
1
-
quailty factor (QF) for fast neutrons and alpha particles
20 times that of x-rays
-
this instrument has a chamber filled with gas that is ionized in part of whole when radiation is present
gas-filled dectectors
-
either the total quanity of electrical charge is measured or the rate at which charge is produced is measured
gas-filled dectectors
-
two kinds of gas-filled detectors may be found in a rad therapy dept
- ionization chamber
- Geiger-Muller (G-M)
-
consist of two electrodes within a gas-filled chamber, an applied voltage across the electrodes & electronics
ionizing chamber
-
a meter to amplify and measure the electrical signal
ionization chamber
-
because of the sensitivity, they are best for finding contamination and other low levels of radiation
G-M detectors (Geiger-Muller)
-
when ____ ____ are properly calibrated, their accuracy approaches ___%, which makes them suitable for measurement of the radiation output of therapy equipment.
-
what is TLDs
thermoluminescent dosimeters
-
because of their small size, they are widely used to measure radiation in a number of applications
thermoluminescent dosimeters (TLDs)
-
as the name implies, thermoluminescent, materials give off light when ____.
heated
-
the ____ number of LiF is close to that of tissue
atomic
-
if proper care is taken, ____ can be measured with and accuracy of approx ___%.
-
also used for mailed intercomparison of therapy unit calibration
TLDs (thermoluminescent dosimeters)
-
ring badges unsed for personnel monitoring & for measurements of environmental levels of radiation
TLDs (thermoluminescent dosimeters)
-
after development, x-ray film exposed to radiation turns ____
black
-
on x-rays the amount of blackness is called
opitical density
-
related to the amount of radiation received by the film
opitical density
-
has a slot in which the film (in its protective paper cover) may be placed and serveral thin metal filters that surround portions of the film
film badge
-
filter allow discrimination between different types and energies of radiation
film badge
-
______ radiation will not penetrate any of the filters but can reach the film in the area where no filters are present.
low-energy (film badge)
-
primary task is to analyze the existing data related to radiation exposure
advisory agencies
-
to assess the radiobiologic risks associated with those exposures
advisory agencies
-
these agencies can develop recommendations for dose limits
advisory agencies
-
the role is to license users of radioactive materials and radiation-producing equipment
regulatory agencies
-
inspect such users, and enforce the appropriate laws
regulatory agencies
-
one of the leading federal regulatory agencies in the u.s. is the
nuclear regulatory commission (NRC)
-
oversees the use of isotopes produced in nuclear reactors.
- NRC (nuclear regulatory commission)
- regulatory agency
-
isotopes are commonly used in ____ ____ departments, in _____ and as sources for teletherapy (external beam radiation) and _____ (internal implants)
- nuclear medicine
- labs
- brachytherapy
-
with regulatory agencies, many states have entered into agreements concerning licensing, inspection and enforcement with ___ and have become "agreement" states.
NRC (nuclear regulatory commission)
-
as part of the agreement, states must maintain a certain level of _____ with NRC regulations
- compatibility
- regulatory agencies
-
transportation of radioactive material is primarily the concern of _____ and the NRC
- DOT (department of transportation)
- regulatory agencies
-
the use of machines that produce ionizing radiation, such as x-ray units and linear accelerators, fall under the jurisdiction of the ____________ and state agencies
- food and drug administration (FDA)
- regulatory agencies
-
the EPA and _______ also have regulations that relate to the use of radiation.
- OSHA (Occupational Safety and Health Administration)
- Regulatory agencies
-
we have a far greater knowledge of the effects of ____ doses of radiation than those of _____ doses.
-
in sufficiently high quantities, radiation can be
lethal
-
a single whole-body exposure of approx ___ cGy is lethal for ___% of the exposed population within ____ days of this event. Termed LD50/30
- 4.5 cGy (450 rads)
- 50%
- 30 days
-
even at levels below the lethal dose, there are significant long-term effects related to exposure to radiation. 2 general classifications
-
are those for which a threshold exists and for which the severity of the effect increases with dose
nonstochastic effects
-
are those that have no threshold and for which the probabilty of occurance is a function of doses.
stochastic effects
-
the severity of the effect is not a function of the dose
stochastic effects
-
the regulatory requirements for limits for exposure to radiation for various groups, and practical methods for individual radiation protection
ionizing radiation
-
contribute to the annual dose to individuals
man-made sources
-
a form of ionization chamber, this is used for personnel monitoring
pocket dosimeter
-
examples of nonstochastic effects are:
- erythema (skin reddening)
- epilation (loss of hair)
- cataract formation
- infertility
-
threshold doses for these effects are relatively high, which is reflected in the higher permitted doses tothe specific organs involved.
nonstochastic effect
-
*note*
overall risk of exposure to radiation is approx 7 in 10,000 persons per rem.
-
what is ALARA
As Low as Reasonably Achievable
-
the less radiation received, the lower the risk
ALARA
-
practical radiation protection from the external beam radiation should include the time-honored methods of
-
rate of nuclear decay
activity
-
the source of ionizing radiation that contributes the most to exposure of the general population in the u.s. is
natural background radiation
-
which type of device is best suited for output measurements of radiation therapy equipment
ionizing chamber
-
stochastic, or nonthreshold, effects of radiation exposure include:
- cancer induction
- genetic effects
- birth defects
-
exposure of which of group of people would contribute the most to the genetically significant dose
20 year old woman
-
the annual effective doe equivalent limit for radiation works is
50 mSv
-
G-M detector is 2 m form a small brachytherapy source and measure rate of 10 mR/hr. what exposure rate would you expect to measure if the detector were moved to 4 m from the source
2.5 mR/hr
-
energy absorbed per unit mass
absorbed dose
-
ionizing per unit mass of air by photons
exposure
-
short range, relatively heavy-mass, high-LET particle
Alpha particle
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