chapter 4 EXAM 2 Flashcards
somatic damage
biologic damage to the body of the exposed individual
who was the first recognized american xray fatality
clarence daily
died oct. 1904
occupational exposure
radiation exposure received by radiation workers in the course of exercising their professional responsibilities
what diseases are more common among radiologist than non radiologists
aplastic anemia and leukemia
british xray and radium protection committee
formed in 1921 to investigate methods for reducing radiation exposure
unfortunately they could not agree on things and did not fulfill their responsibility
skin erythema dose
the first unit for measuring radiation exposure (1900-1930)
skin erythema dose definition
received quantity of radiation that causes diffused redness over an area of skin after irradiation
first international congress of radiology
in london england in 1925
allowed collaboration of rads from around the world
no decisions for measuring ionizing radiation
the international commission on radiation units and measurements ICRU
formed in 1925
finished the job from the second international congress of radiology
roentgen became the internationally accepted unit of measurement for x radiation and gamma radiation
second international congress of radiology
stockholm sweeden 1928
made the roentgen accepted as a unit of exposure but could not define it so the ICRU did in 1937
short term somatic effects (early or acute effects)
definition
somatic effects that appear within minutes hours days or weeks of the time of radiation exposure
list of short term somatic effects (early or acute effects)
nausea fatigue redness of skin loss of hair fever blood disorders shedding of skin
tolerance dose
a radiation dose to which occupationally exposed persons could be continuously subjected without any apparent harmful acute effects
believed nothing would happen as long as it was kept below dose
in 1934 internation xray and radium protection committee recommended a tolerance dose of
0.2 roentgen a day
was reduced to 0.1 roentgen a day in 1936
threshold dose
a dose of radiation below which an individual has a negligible chance of sustaining specific biologic damage
long term or late somatic effects definition
effects of ionizing radiation that appeared months or years following exposure to ionizing radiation
long term or late somatic effects list
cancer
embryonic effects (birth defects)
formation of cataracts
the general conference of weights and measurements created
the international system of units to be able to interchange units throughout the world
when was tolerance dose replaced and what was it replaced by
early 1950s and it was replaced by the maximum permissible dose MPD
maximum permissible dose MPD
a term used in the past to indicate the maximum dose equivalent of ionizing radiation that an occupationally exposed person could absorb in a specified time without sustaining bodily injury
MPD meant that
no amount of radiation was considered completely safe
1 sievert is equal to how many rem
100 rem
what are the 5 radiation quantities
- exposure
- air kerma
- absorbed dose
- equivalent dose
- effective dose
exposure is measured in
reontgen (traditional)
columb per kilogram (SI)
air kerma is measured in
gray with subscripts “a” or “t”
absorbed dose is measured in
Rad (traditional)
gray (SI)
equivalent does is measured in
Rem (traditional)
sievert (SI)
effective dose is measured in
Rem (traditional)
sievert (SI)
exposure (x)
the total electrical charge of one sign, either all pluses or minuses, per unit mass
basically measures the amount of ion pairs in the air.
exposure is measured by an
ionization chamber
coulomb (C)
a basic unit of electrical charge
how do you convert from roentgens to coulombs per kilogram
multiply the number of roentgens by 2.58 x 10^-4
how do you convert coulombs per kilogram to roentgens
divide the coulombs per kilogram by 2.58x10^-4
air kerma
SI quantity that can be used to express radiation concentration transferred to a point
kinetic energy released in a unit mass of air
basically indicates a calculation of radiation intensity in air
air kerma is replacing what
the traditional quantity, exposure
Kerma is an acronym for
kinetic energy released in matter
kinetic energy released per unit mass
air kerma is expressed in metric units of
joule per kilogram
joule is the metric unit of
energy
tissue kerma
energy released in a unit mass of tissue
tissue kerma is measured in
Gray
air kerma is expressed as
Gya
tissue kerma is expressed as
Gyt
if the air kerma is measured at a point where soft tissue is located,
the absorbed dose in the tissue will be about the equal to the air kerma
dose area product
the sum total or air kerma over the exposed area of the patients surface
DAP is expressed in units of
mGy/cm^2
DAP is the most practical quantity for
monitoring the radiation delivered to patients
absorbed dose (D)
the amount of energy per unit mass absorbed by the irradiated object
absorbed dose is used to indicate
the amount of ionizing radiation a patient receives during a procedure
amount of energy absorbed by a patient depends on
atomic number (Z)
mass density
energy of incoming photon
absorption increases as
atomic number and mass density increases and photon energy decreases
effective atomic number (Zeff)
weighted average of atomic numbers
T or F
bone has a higher effective atomic number than soft tissue
true
Zeff of bone =
13.8
Zeff of soft tissue =
7.4
what is the only measure of ionization in air and not other tissues
exposure
1 gray = how many joules/kilogram
1 joule/kilogram
what is the traditional unit for joule
erg
1 gray = how many rads
100 rad
how do you convert rad to gray
divide the rad by 100 to get gray
how to convert gray to rad
multiply the gray by 100
how to convert from gray to milligray
multiply by 1000
how to convert from milligray to gray
divide by 1000
in therapeutic radiology what is replacing the rad for recording absorbed dose
the centigray
to convert gray to centigray
multiply by 100
surface integral dose SID
the total amount of radiant energy transferred by ionizing radiation to the body during an exposure
quality factor AKA radiation weighting factor
an adjustment multiplier used in the calculation of dose equivalent
linear energy transfer LET
the amount of energy deposited on average by ionizing radiation in an object per unit length of track as it passes through the object
Linear energy transfer is measured in
KeV/micrometer
high LET
departs energy quickly and causes more biologic damage
alpha particles have a high LET
low LET
more sparsely ionizing.
less chance of producing biologic damage because it disperses its energy
LET helps explain
the quality factor or modifying factors for different types of ionizing radiation
equivalent dose enables the calculation of
effective dose
stochastic effects
non threshold, randomly occurring biologic effects of ionizing radiation
the probability of stochastic effects depends on
radiation dose and type of energy of the ionizing radiation
the higher the radiation weighting factor of a type of ionizing radiation, the more
effective it is at producing biologic damage
equivalent dose is obtained by multiplying
the absorbed dose (D) by the radiation weighting factor (Wr)
or Sv = Gy x Wr
how to convert the sievert to the microsievert
multiply the sievert by 1,000,000
effective dose
the sum of the weighted equivalent doses for all irradiated tissues and organs
effective dose includes
the type of radiation and the radiosensitivity of the specific organ or body part
tissue weighting factor
a value that denotes the percentage of the stochastic risk stemming from the irradiation of tissue
how to determine effective dose
an absorbed dose (D) is multiplied by a radiation weighting factor to obtain the equivalent dose. then the equivalent dose is multiplied by a tissue weighting factor to obtain the effective dose.
collective effective dose ColEfD
the product of the average effective dose for an individual belonging to the exposed population or group and the number of persons exposed
what is the unit for ColEfD
person-sievert
what does the total effective dose equivalent do TEDE
to monitor and control human exposure to ionizing radiation
what is the TEDE
the sum of effective dose equivalent from external radiation sources and a quantity called committed effective dose equivalent (CEDE) from internal exposures
TEDE is a useful dose monitor for
occupationally exposed personnel
for occupationally exposed personnel, the whole body TEDE regulatory limit is
0.05 sieverts or 50 milisieverts
