Unit 3 Radiation electronics and detection part 2

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What is the main purpose of a hermetic seal in scintillation detectors?

To reflect the light produced during scintillation

To enhance the absorption of x-rays

To increase the isotropy of the light emission

To prevent the scintillation crystals from coming into contact with air or moisture (correct)

What is the reason for using Thallium activated Sodium iodide and Thallium activated Cesium iodide crystals in scintillation detectors?

Because they are easy to manufacture

Because they contain iodine with a high atomic number for effective absorption of x-rays (correct)

Because they are the most widely available materials

Because they are the most inexpensive options

What is the characteristic of light produced during scintillation?

It is emitted in a single direction

It is absorbed by the scintillation crystal

It is emitted isotropically (correct)

It is reflected by the hermetic seal

What is the purpose of the polished inner surface of the Al seal in scintillation detectors?

To reflect the light produced during scintillation Signup and view all the answers

What is the common application of Thallium activated Cesium iodide crystals in scintillation detectors?

In radiography imaging detectors Signup and view all the answers

Why is it important to prevent scintillation crystals from coming into contact with air or moisture?

Because they can crack or degrade Signup and view all the answers

What is the purpose of a photomultiplier tube (PMT) in a scintillation detector?

To convert light into electrical signals Signup and view all the answers

What is the process by which electrons are emitted from the photocathode in a PMT?

Photoemission Signup and view all the answers

What determines the overall electron gain of a PMT?

The number of dynodes and the electron gain at each dynode Signup and view all the answers

What is the purpose of the dynodes in a PMT?

To amplify the electron signal Signup and view all the answers

What is the advantage of using scintillation detectors for radiation detection?

They are highly sensitive to low-level radiation Signup and view all the answers

What is the process of thermoluminescence used for?

For personnel radiation monitoring using TLD badges Signup and view all the answers

What happens to the electrons in a thermoluminescent crystal when it is heated?

They escape the traps and emit light Signup and view all the answers

What is the purpose of the collecting electrode (anode) in a PMT?

To absorb the electron pulse from the last dynode Signup and view all the answers

What is the result of the amplification process in a PMT?

A strong electrical signal Signup and view all the answers

What determines the spectral sensitivity of a PMT?

The photocathode material Signup and view all the answers

What is the purpose of the preamplifier in a scintillation detector?

To further amplify the electrical signal Signup and view all the answers

What is the purpose of annealing in Thermoluminescence Dosimetry?

To release residual energy stored from previous exposures Signup and view all the answers

What is the role of the photomultiplier (PMT) tube in Thermoluminescence Dosimetry?

To measure the intensity of emitted light Signup and view all the answers

What is the relationship between the height of the highest temperature peak and the energy deposited in the TLD?

Directly proportional Signup and view all the answers

What is the advantage of using LiF as a thermoluminescent phosphor in TLDs?

All of the above Signup and view all the answers

What is the purpose of the TLD analyzer in Thermoluminescence Dosimetry?

To relate the glow curve to exposure or dose Signup and view all the answers

What is the role of Europium in Computed Radiography Phosphor Plate?

To create defects in the crystal lattice Signup and view all the answers

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 Signup and view all the answers

What is the composition of the Computed Radiography Phosphor Plate?

Barium fluorohalides (BaFBr/BaFCl) Signup and view all the answers

How many times can LiF TLDs be used after annealing?

Almost 300 times Signup and view all the answers

What is the purpose of the planchet in Thermoluminescence Dosimetry?

To hold the TLD phosphor for analysis Signup and view all the answers

What is the primary function of storage phosphor screens in Computed Radiography?

To store the latent image in the form of excited electrons Signup and view all the answers

What is the term used to describe the process of releasing trapped electrons in phosphor screens using intense infrared light?

Stimulable phosphorescence Signup and view all the answers

What percentage of electrons return to the ground state immediately after exposure to x-rays, releasing light through fluorescence?

50% Signup and view all the answers

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 Signup and view all the answers

What determines the spatial resolution of the CR imaging system?

The diameter of the laser beam Signup and view all the answers

What is the result of the PSP stimulation process?

The emission of blue light Signup and view all the answers

What is the purpose of the PSP erasure process?

To prevent ghosting on subsequent images Signup and view all the answers

What is the role of photodetectors in CR imaging systems?

To convert emitted light into an electrical signal Signup and view all the answers

What is the result of a thicker laser beam in CR imaging systems?

Lower spatial resolution Signup and view all the answers

What is the purpose of intense white light in PSP erasure?

To erase the residual latent image Signup and view all the answers

What is the main purpose of erasing a CR plate after periods of non-use?

To reduce background radiation Signup and view all the answers

What is the result of high Z and a thicker phosphor layer in CR plates?

More x-rays are absorbed Signup and view all the answers

What is the purpose of needle-shaped crystals in CR plates?

To direct the light upward and improve emission efficiency Signup and view all the answers

What is the characteristic of the light emitted by the phosphor in CR plates?

It is emitted isotropically Signup and view all the answers

What is the function of the reflective layer in CR plates?

To reflect light backward Signup and view all the answers

What is the benefit of a higher fill factor in a DR image receptor?

Better contrast resolution Signup and view all the answers

What is the result of a higher resolution in a DR image?

An increase in the ability to see grayscale Signup and view all the answers

What is the purpose of the active-matrix array in DR systems?

To form a digital radiograph Signup and view all the answers

What is the benefit of using a thin film transistor in DR systems?

Improved charge collection Signup and view all the answers

What is the result of a higher absorption efficiency in a CR plate?

More light is emitted Signup and view all the answers

What enables indirect conversion systems to save patient dose?

Higher absorption efficiency due to the thicker phosphor layer Signup and view all the answers

What is the coupling element in CR systems?

Fiber optics Signup and view all the answers

What is the capture element in indirect DR systems?

Scintillation phosphors Signup and view all the answers

What is the advantage of indirect conversion systems compared to direct conversion systems?

They can be less expensive and easier to work with Signup and view all the answers

What is the collection element in CR systems?

Photodiode Signup and view all the answers

What is the difference between indirect and direct conversion systems in terms of detector element thickness?

Indirect conversion systems have thicker detector elements Signup and view all the answers

What is the effect of reducing the dexel size in a Direct DR system?

Reduced patient radiation dose Signup and view all the answers

What is the function of the Thin Film Transistor (TFT) in a Direct DR system?

To release the electrical charge from the dexel Signup and view all the answers

What is the material used in the capture element and the coupling element in a Direct DR system?

Amorphous Selenium (a-Se) Signup and view all the answers

What is the result of an ionizing event in a Direct DR system?

Creation of a charged pair Signup and view all the answers

What is the purpose of the gate lines in an AMA?

To control the order of dexel readout Signup and view all the answers

What is the difference between Direct DR and Indirect DR systems?

Indirect DR uses a phosphor screen, while Direct DR does not Signup and view all the answers

What is the purpose of the phosphor screen in an Indirect DR system?

To scintillate when exposed to X-rays, emitting light Signup and view all the answers

What is the advantage of using a Direct DR system over an Indirect DR system?

Higher resolution Signup and view all the answers

What determines the absorption efficiency of an AMA?

The ratio of photons absorbed to incident photons Signup and view all the answers

What is the purpose of keeping the layers of photoelectric material thin in a Direct DR system?

To increase absorption efficiency Signup and view all the answers

Unit 3 Radiation electronics and detection part 2 - Med Rad 2

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