63 Questions
What is the main purpose of a hermetic seal in scintillation detectors?
To prevent the scintillation crystals from coming into contact with air or moisture
What is the reason for using Thallium activated Sodium iodide and Thallium activated Cesium iodide crystals in scintillation detectors?
Because they contain iodine with a high atomic number for effective absorption of x-rays
What is the characteristic of light produced during scintillation?
It is emitted isotropically
What is the purpose of the polished inner surface of the Al seal in scintillation detectors?
To reflect the light produced during scintillation
What is the common application of Thallium activated Cesium iodide crystals in scintillation detectors?
In radiography imaging detectors
Why is it important to prevent scintillation crystals from coming into contact with air or moisture?
Because they can crack or degrade
What is the purpose of a photomultiplier tube (PMT) in a scintillation detector?
To convert light into electrical signals
What is the process by which electrons are emitted from the photocathode in a PMT?
Photoemission
What determines the overall electron gain of a PMT?
The number of dynodes and the electron gain at each dynode
What is the purpose of the dynodes in a PMT?
To amplify the electron signal
What is the advantage of using scintillation detectors for radiation detection?
They are highly sensitive to low-level radiation
What is the process of thermoluminescence used for?
For personnel radiation monitoring using TLD badges
What happens to the electrons in a thermoluminescent crystal when it is heated?
They escape the traps and emit light
What is the purpose of the collecting electrode (anode) in a PMT?
To absorb the electron pulse from the last dynode
What is the result of the amplification process in a PMT?
A strong electrical signal
What determines the spectral sensitivity of a PMT?
The photocathode material
What is the purpose of the preamplifier in a scintillation detector?
To further amplify the electrical signal
What is the purpose of annealing in Thermoluminescence Dosimetry?
To release residual energy stored from previous exposures
What is the role of the photomultiplier (PMT) tube in Thermoluminescence Dosimetry?
To measure the intensity of emitted light
What is the relationship between the height of the highest temperature peak and the energy deposited in the TLD?
Directly proportional
What is the advantage of using LiF as a thermoluminescent phosphor in TLDs?
All of the above
What is the purpose of the TLD analyzer in Thermoluminescence Dosimetry?
To relate the glow curve to exposure or dose
What is the role of Europium in Computed Radiography Phosphor Plate?
To create defects in the crystal lattice
What is the purpose of the F-centres in the Computed Radiography Phosphor Plate?
To capture electrons that are released from the phosphor atoms when x-rays strike the phosphor plate
What is the composition of the Computed Radiography Phosphor Plate?
Barium fluorohalides (BaFBr/BaFCl)
How many times can LiF TLDs be used after annealing?
Almost 300 times
What is the purpose of the planchet in Thermoluminescence Dosimetry?
To hold the TLD phosphor for analysis
What is the primary function of storage phosphor screens in Computed Radiography?
To store the latent image in the form of excited electrons
What is the term used to describe the process of releasing trapped electrons in phosphor screens using intense infrared light?
Stimulable phosphorescence
What percentage of electrons return to the ground state immediately after exposure to x-rays, releasing light through fluorescence?
50%
What is the purpose of the laser beam in PSP stimulation?
To add energy to the trapped electrons, allowing them to escape and fall back to their atomic shells
What determines the spatial resolution of the CR imaging system?
The diameter of the laser beam
What is the result of the PSP stimulation process?
The emission of blue light
What is the purpose of the PSP erasure process?
To prevent ghosting on subsequent images
What is the role of photodetectors in CR imaging systems?
To convert emitted light into an electrical signal
What is the result of a thicker laser beam in CR imaging systems?
Lower spatial resolution
What is the purpose of intense white light in PSP erasure?
To erase the residual latent image
What is the main purpose of erasing a CR plate after periods of non-use?
To reduce background radiation
What is the result of high Z and a thicker phosphor layer in CR plates?
More x-rays are absorbed
What is the purpose of needle-shaped crystals in CR plates?
To direct the light upward and improve emission efficiency
What is the characteristic of the light emitted by the phosphor in CR plates?
It is emitted isotropically
What is the function of the reflective layer in CR plates?
To reflect light backward
What is the benefit of a higher fill factor in a DR image receptor?
Better contrast resolution
What is the result of a higher resolution in a DR image?
An increase in the ability to see grayscale
What is the purpose of the active-matrix array in DR systems?
To form a digital radiograph
What is the benefit of using a thin film transistor in DR systems?
Improved charge collection
What is the result of a higher absorption efficiency in a CR plate?
More light is emitted
What enables indirect conversion systems to save patient dose?
Higher absorption efficiency due to the thicker phosphor layer
What is the coupling element in CR systems?
Fiber optics
What is the capture element in indirect DR systems?
Scintillation phosphors
What is the advantage of indirect conversion systems compared to direct conversion systems?
They can be less expensive and easier to work with
What is the collection element in CR systems?
Photodiode
What is the difference between indirect and direct conversion systems in terms of detector element thickness?
Indirect conversion systems have thicker detector elements
What is the effect of reducing the dexel size in a Direct DR system?
Reduced patient radiation dose
What is the function of the Thin Film Transistor (TFT) in a Direct DR system?
To release the electrical charge from the dexel
What is the material used in the capture element and the coupling element in a Direct DR system?
Amorphous Selenium (a-Se)
What is the result of an ionizing event in a Direct DR system?
Creation of a charged pair
What is the purpose of the gate lines in an AMA?
To control the order of dexel readout
What is the difference between Direct DR and Indirect DR systems?
Indirect DR uses a phosphor screen, while Direct DR does not
What is the purpose of the phosphor screen in an Indirect DR system?
To scintillate when exposed to X-rays, emitting light
What is the advantage of using a Direct DR system over an Indirect DR system?
Higher resolution
What determines the absorption efficiency of an AMA?
The ratio of photons absorbed to incident photons
What is the purpose of keeping the layers of photoelectric material thin in a Direct DR system?
To increase absorption efficiency
This quiz covers the process of radiation dosimetry using Thermoluminescent Dosimeters (TLDs) and their analysis. It includes the steps involved in irradiating the TLD phosphor, subsequent heating, and measurement of the emitted light intensity. Test your understanding of radiation detection and measurement!
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