G.radiation instrumentation Flashcards
An _______ is a gas-filled chamber that has two electrodes with an applied voltage and a meter that measures the electrical signal. When the gas is irradiated, ion pairs are produced and create an electrical current that flow to the electrodes, which is measured
ionization chamber
The _____of the gas in the chamber determines the sensitivity of the ion Chamber
mass
Ionization chamber Readings are in
mR (milliRoentgen) or mR/hour
Ion chambers are Not sensitive enough to detect low levels of radiation such as
radiation Contamination
When calibrating the ionization chamber, certain correction factors need to be used if the chambers are not sealed. » Correction factors are
temperature, pressure, and volume
Examples of ion chambers are
pocket dosimeters and a cutie pies
A ______dosimeter is a low-energy personnel dosimeter
A ______ is a portable ion chamber (survey meter)
cutie pie
______ is a Portable instrument used to detect radiation of low levels and radioactive contamination
Geiger-muller detector
M detectors are used to survey rooms and equipment for presence of radiation but
dont actually measure the amount of radiation
Geiger-muller detector is a Gas-filled chambers that contain a mixture of gasses with a pressure of
100 mmHg
Geiger-muller detector Can detect radiation
100 mR/hr and less
is a Geiger-muller detector or ion chamber more sensitive
Geiger-muller detector
TLD/ OSL are Solid-state detectors and _____ devices
Personnel monitoring
______: When heated, this dosimeter lights up in proportion to the amount of radiation that was absorbed
Thermoluminescent Dosimeter (TLD)
Thermoluminescent Dosimeter (TLD)
has a crystal material embedded in the dosimeter and when irradiated, electrons are released from their valence bonds and remain trapped within a
gap
TLDs are commonly used for patient dosimetry (in-vivo measurements) to record
entrance or skin dose
TLDs are made of ________because this material has an atomic number that is very similar to human tissue
lithium fluoride (LiF)
TLDs are also made in ring form for personnel monitoring for radiation workers handling
radioactive materials and equipment
________is where Crystals release electrons from their valence bonds when irradiated just like TLDs. however, electrons are released and visible light photons are emitted when they are excited by light instead of heat
Optically Stimulated Luminescence (OSL)
Optically Stimulated Luminescence (OSL) are Made of
aluminum oxide (AL203:C)
OSLDs are the Most common detector used to
measure occupational (personnel) exposure today
_______ are Small solid-state detectors that are very sensitive to radiation
Diodes
Both TLDs and OSLs must be sent out to a special facility to be
analyzed
Diodes are the equipment of choice for patient dosimetry because it can measure the
beam delivered for treatment
Diodes are used for a daily QA check for the
linear accelerator’s beam output
Diodes are not used to calibrate the
beam
Neutron Detectors are Important in proton therapy and photon therapy above
10 MV
____ scatter occurs at energies above 10 MV
neutrons
_____chambers can be used to detect neutrons
Ionization
_____ within the walls and gas of chamber make ionization chambers more sensitive to neutrons
hydrogen
