Chapter 9 Notes Flashcards
_____ is any form of radiation that possesses energy capable of displacing atomic electron bonds and breaking the electron bonds that hold the molecules of matter together
ionizing radiation
ionizing radiation comes from two major sources
natural background radiation and human-made radiation
biological effects of radiation exposure are either
somatic or genetic
somatic effects
occur in individual exposed
genetic effects
occur in descendants of individual exposed
important radiation quantities and units
exposure, absorbed dose, and equivalent dose
SI unit of exposure
coulomb per kilogram (C/kg)
SI unit of absorbed dose
gray (Gy)
SI unit of equivalent dose
sievert (Sv)
traditional unit of exposure
roentgen (R)
traditional unit of absorbed dose
rad
traditional unit of equivalent dose
rem
portable field survey instruments include
Geiger-Mueller (GM) survey instruments, scintillation detection devices, and ionization chamber instruments
personnel monitoring devices include
optically stimulated luminescence dosimeter, film badge dosimeter, thermoluminescent dosimeter, and pocket dosimeters
radiographer’s responsibilities
minimize dose, protect patients and others from unnecessary exposure, and optimize image quality
alpha particles are composed of
two protons and two neutrons
alpha particles can travel _____
5 cm in air
beta particles are composed of
electrons from decaying radioactive material
beta particles can travel _____
10-100 cm in air
_____ particles are more penetrating in tissue than _____ particles
beta; alpha
most biological damage is due to _____ interactions
indirect
somatic effects are
evident in individual
examples of somatic effects
cataracts, erythema, cancer formation
genetic effects are
evident in offspring of individual
the NCRP established
an international standard for dose measurement and exposure
natural sources of ionizing radiation
cosmic radiation, terrestrial radiation, radionuclides naturally present internally and externally
man-made sources of ionizing radiation
x-rays, radiopharmaceuticals, consumer products, air travel, nuclear fuel production, fallout
NCRP lists five major areas of radiation exposure in US
ubiquitous background; medical procedures; consumer products; industrial, medical education, and security activities; occupational exposure
medical imaging modalities contributing to medical exposure
CT, radiography and fluoroscopy, interventional fluoroscopy, NM, radiotherapy
exposure
number of ionizations in given quantity of air
units of exposure
1 R = 2.58 x 10 (to the negative fourth power) C/kg
absorbed dose
measures amount of energy absorbed
absorbed dose units
1 Gy = 100 rad
kerma
kinetic energy released in matter
unit for kerma
Gy (Gray)
air kerma
kinetic energy released per unit mass of air
air kerma is used to describe
tube output; input to IRs
unit of air kerma
1 cGy = 1 rad (equivalent to 1 R of exposure)
integral dose
total amount of energy deposited in matter
equivalent dose
product of absorbed dose and radiation weighting
radiation weighting
different types of ionizing radiation produce different biological responses
units for equivalent dose
1 Sv = 100 rem
rem stands for
roentgen equivalent mane
effective dose (E)
sum of equivalent dose of specific tissues; accounts for various tissue sensitivities to irradiation
activity (A)
describes quantity of radioactive material
activity is expressed as
number of radioactive atoms to decay per unit of time
unit of activity
curie (Ci) (3.7 x 10 (to the 10th power) disintegrations/sec)
becquerel (Bq) (1 disintegratgion/sec)
Geiger-Mueller survey instruments
gas-filled detector; volume of gas between two electrodes
GM counters are used to
demonstrate presence of radiation
GM counters are most effective with
particulate radiation
GM counters are least effective in detecting
x-ray or gamma radiation
scintillation detection devices
scintillators emit light when stimulated by ionizing radiation; light converted to electric signal
scintillation detection devices are commonly used in
NM and CT
ionization chamber instruments are used to evaluate
equipment performance, leakage radiation, and patient exposure
personnel monitoring devices are provided to workers who accumulate _____ of recommended dose limit
1/10
OSL
optically stimulated luminescence
TLD
thermoluminescent dosimeter
most common type of personnel monitor
OSL
OSL contents
thin layer of aluminum oxide
OSL function
laser light processing of aluminum dioxide causes luminescence; level of luminescence proportional to amount of exposure received
OSL are issued
on monthly or quarterly basis
OSLs are sensitive to
1 millirem (mrem)
film badge dosimeter contents
two pieces of film in light tight packet
film badge dosimeter is sensitive to
10 mrem
film badge dosimeters are environmentally sensitive to
heat, humidity, pressure, prolonged exposure to light
TLD contents
lithium fluoride crystals
lithium fluoride crystals will
store energy when exposed to ionizing radiation; released stored energy when heated as visible light; amount of light released proportional to amount of exposure
TLD sensitivity
10 mrem
TLDs are environmentally sensitive similar to
film badges
electronic personal dosimeter
ionization of air in small chamber
