Deck 5: Flat-Panel Digital Radiography

Question 1

Which of the following will detect the light from the CsI scintillator in the indirect flat-panel TFT detector?

A)TFT switch
B)sensing area
C)storage capacitor
D)active matrix

Answer 1

sensing area

Question 2

The raw digital data from a detector has a high image contrast simply because of the wide exposure latitude of the digital detector.

Answer 2

False

Question 3

The flat-panel TFT digital detector uses complex and sophisticated electronic circuitry to read out the electrical charges produced and stored in the matrix array.

Answer 3

True

Question 4

All digital imaging systems have what is referred to as the limiting resolution, which is the spatial frequency limit that is obtained at an MTF value of 0.1.

Question 5

An important imaging performance characteristic of a flat-panel detector that has an impact on clinical practice is image lag.

Question 6

With selenium drum technology, a negative charge is first placed on the drum, which is then exposed to X-rays.

Question 7

Which of the following reduces the output image from the scintillator phosphor to the size of the CCD array?

A)pixel detector
B)exposure indicator
C)photoconductor
D)optical system

Question 8

While the low frequencies contain fine details of the image, high frequencies contain the contrast information in the image.

Question 9

The purpose of a photodiode is to collect and store the electrical charge produced in the a-Si photodiode array.

Question 10

____ produce(s) lateral spreading of light, which destroys the spatial resolution of the image.

A)Structured phosphors
B)Amorphous silicon
C)Cesium iodide
D)Powdered phosphors

Question 11

Which of the following is a photoconductor that conducts electrons when struck by light or X-ray photons?

A)selenium
B)cesium iodide
C)amorphous silicon
D)photodiode

Question 12

With indirect flat-panel TFT digital detectors, what is used to first convert X-ray photons into light photons?

A)scintillator layer
B)k-edge characteristic
C)electrical charge
D)photoconductor

Question 13

A higher MTF value at a higher spatial frequency means that the detector provides better spatial resolution than lower MTF values at low frequencies.

Question 14

Which of the following images is obtained initially from the detector and contains artifacts due to the bad detector elements?

A)flat-field
B)pre-processed
C)post-processed
D)raw digital

Question 15

Too much edge enhancement produces image noise and creates ____.

A)nonlinear response
B)poor contrast
C)linear response
D)an halo effect

Question 16

Which of the following addresses the appearance of the image displayed on a monitor for viewing and interpretation by a radiologist?

A)presentation operations
B)pre-processing operations
C)DICOM operations
D)post-processing operations

Question 17

Which layer used in the indirect flat-panel digital detector is usually either cesium iodide (CsI) or gradolinium oxysulfide (Gd₂O₂S)?

A)flat panel
B)thin-film transistor
C)X-ray scintillator
D)amorphous silicon

Question 18

Flaws in the various components that make up a panel can lead to image lag.

Question 19

Under random conditions it has been shown that the quantum efficiencies (based on the X-ray absorption properties of the detector converter materials) at 70 kV is about 67% for a-Se and 77% for CsI phosphor.

Question 20

Which concept examines the response of the image receptor (screen-film detector or digital detector) to the radiation falling upon it?

A)fill factor
B)exposure indicator
C)exposure latitude
D)image processor

Question 21

One important physical concept that is essential to understanding the rationale for the use of specific X-ray ____________________ and a-Se in digital detectors is that of X-ray attenuation or absorption.

Question 22

The flat-panel TFT digital detector is designed as a matrix of detector elements, each of which can be regarded as a(n) ____________________.

Question 23

Image processing is not intended to correct poor images due to routine errors that are made during image ____________________.

Question 24

Which of the following deals with the efficiency of a detector to convert the x-radiation signal at its entrance window into useful image signal?

A)MTF
B)DQE
C)SNR
D)a-Se

Question 25

Which of the following plays a role in image display optimization?

A)scaling the histogram
B)edge enhancement algorithm
C)image post-processing operations
D)image pre-processing operations

Question 26

In imaging applications, because contrast resolution (the ability to resolve small differences in tissue contrast) is mandatory for diagnostic interpretation, ____ is important.

A)low SNR
B)high DQE
C)high SNR
D)low DQE

Question 27

Which of the following is a complex mathematical function that measures the ability of the detector to transfer its spatial resolution characteristics to the image?

A)image lag
B)dynamic range
C)spatial resolution
D)modulation transfer function

Question 28

Which of the following describes the ability of the imaging system to resolve fine details present in an object?

A)spatial resolution
B)modulation transfer function
C)dynamic range
D)ghosting

Question 29

Since there are different sizes of body parts to be imaged, different sizes of ____________________ are commercially available for clinical imaging.

Question 30

While indirect detectors use a phosphor, direct detectors use a(n) ____________________.

Question 31

The dynamic range of a digital detector is the response of the detector to different levels of ____.

A)radiation exposure
B)spatial frequency
C)underexposure
D)overexposure

Question 32

____ refer(s) to the persistence of the image; charge is still being produced after the radiation beam from the X-ray tube has been turned off.

A)Image lag
B)Image artifacts
C)Image flaw
D)Image effect

Question 33

The column artifact arising from a bad column of pixels indeed provides a rationale for ongoing ____________________ of the digital imaging system.

Question 34

The charge from each pixel in a row is transferred to the next row and subsequently down all the columns to the final ____________________ row.

Question 35

An MTF of ____ represents a perfect transfer of spatial and contrast information.

A)1
B)2
C)3
D)4

Question 36

At ____ kV, efficiencies are 37% for a-Se and 52% for CsI.

A)100
B)110
C)120
D)130

Question 37

The ____ is a graph of the contrast plotted as a function of spatial frequency.

A)DQE
B)SNR
C)MTF
D)a-Se

Question 38

The purpose of the a-Si photodiode layer is to convert the light from the X-ray detection ____________________ into electrical charges.

Question 39

The ____________________ technology was developed as a dedicated system specifically for imaging the chest.

Question 40

For the flat-panel TFT digital detectors used in ____________________, the readout process and readout electronics are somewhat different to the detectors used for radiographic applications.

Question 41

Flaws include dust, scratches, chemical reactions among the various materials that the detector is made of as well as defective ____________________.

Question 42

A higher MTF value at ____________________ spatial frequencies means that the detector provides better contrast resolution.

Question 43

Flat-panel digital detectors are complex devices and pose numerous challenges in the ____________________ process.

Question 44

In imaging, the goal is to obtain good ____________________ information in the image.

Question 45

For digital imaging systems, the spatial resolution depends on the size of the ____________________ in the matrix.

Question 46

Problems arising as a result of image ____________________ may also be related to the differences in the acquisition workstation and the higher-quality PACS workstation used by the radiologist.

Question 47

A system that has a higher spatial frequency at an MTF of 0.1 will show better spatial ____________________ than a system that has a lower spatial frequency at an MTF of 0.1.

Question 48

The narrower the LSF, the better the ____________________ resolution.

Question 49

Optimization of the image displayed on monitors for viewing by both technologists and radiologists requires a good working knowledge of not only image processing but also display ____________________ principles and technology.

Question 50

Flat-panel detectors can be used in portable radiography applications and in applications involving ____________________.