Quizlet LRA-221 Week 3 Flashcards
(56 cards)
1
Q
What do Scintillators do?
A
Absorb x-rays photons & convert them to light
2
Q
What is a Thin Film Transistor (TFT)?
A
- photosensitive array, made up of small pixels (approx. 100 to 200 µm)
- converts the light into electrical charges.
3
Q
What controls line scanning sequence?
A
Specialized silicon integrated circuits
4
Q
What is “a-Se”? And what is it used as?
A
- Amorphous Selenium
- Used as a Photoconductor
- absorbs x-rays and converts them to electrons
5
Q
Is “a-Se” considered a scintillator? (T/F)
A
- FALSE
- it is a photoconductor
6
Q
What do Flat Panel Detectors that use indirect conversion technology convert?
A
X-rays photons are converted to visible light
light photons are converted into an electrical signal
7
Q
How many steps does an indirect conversion FPD have?
A
2
8
Q
How is Detector Performance measured?
A
- Numerical measurement of spatial resolution and DQE
- Observation of low contrast objects in a contrast detail
phantom
9
Q
What can cause an image to have LAG?
A
- Rapid image succession
- Overexposure and lack of beam attenuation
10
Q
Are dead pixels at the edge of the detector easily identified?
A
No
11
Q
Can absorption materials be attached to the pixel array electrically or physically ? (T/F)
A
TRUE
12
Q
Do ALL FPD have the ability to take images faster than the detector can accommodate ? (T/F)
A
FALSE
13
Q
Describe what a CCD (Charge Coupled Device) is?
A
Oldest indirect-conversion Digital Radiography Systems, used to acquire digital image.
14
Q
What is a Capacitor?
A
An electrical component that stores electrical charge or electrical energy.
15
Q
The amount of X-rays absorbed depends on the type of Scintillator (T/F)?
A
TRUE
16
Q
Describe the Readout process
A
- data is sent sequentially to the sense amplifier and is digitized.
- The readout process requires that the movement of the electrons is timed.
- Multiple voltage changes occur very quickly.
17
Q
What are the “most” common types of noise that affect image quality?
A
- Statistical noise
- Amplification noise
- “Dark” or current noise
18
Q
What is the difference between CMOS and CCDs?
A
- CCD sensors create high-quality, low-noise images.
- CMOS sensors are usually more susceptible to noise.
- CMOS uses very little power.
- Pixel Fill factor is greater w CCDs than CMOS
19
Q
What is the most popular base of material used in integrated circuits?
A
Silicon
20
Q
Define CMOS?
A
- A semiconductor
- When struck with x-ray photons it converts the x-rays into light photons and store them in capacitors.
21
Q
Which indirect conversion detector requires optical coupling and image size reduction?
A
CCD
22
Q
When specialized pixels in a complementary metal oxide silicon system, are struck with x-ray photons what happens? List the steps.
A
- The x-ray photons are converted into light
- Light photons are stored in capacitors
- Light photons are converted into electrical charges
23
Q
What is Quantum Efficiency?
A
- The amount of electrons produced relative to the incident light from the scintillator. The measure of the efficiency of the light collection and the signal created in the CCD chip.
24
Q
What are some advantages of CCDs?
A
- CCDs are simple and modular.
- Easy to repair, replace, and upgrade
- Inexpensive than TFT-based flat-panel systems.
(less expensive to manufacture and demagnification capabilities)
25
The Number of Electron-Hole pairs produced is related to the amount of light absorbed (T/F)?
TRUE
26
The Polysilicon layer within a CCD acts as an insulator (T/F)?
FALSE
27
CCDs use more power than CMOS (T/F)?
TRUE
28
1. Scintillators are phosphors that
A. produce light when absorbing x-rays
B. produce x-rays when absorbing light
C. absorb light and produce electrical charges
D. absorb x-rays and produce electrical charges
A. produce light when absorbing x-rays
29
2. A device that includes a photosensitive array and small pixels that convert light into electrical charges is known as a ______ transistor
A. thin-field
B. field-effect
C. thin-film
D. field-energy
C. thin-film
30
3. In a flat-panel detector, specialized silicon integrated circuits control
A. line scanning sequence
B. readout
C. amplification
D. analog-to-digital conversion
A. line scanning sequence
31
4. Which of the following is used as a photoconductor?
A. Gd2O2S
B. a-Se
C. a-Si:H
D. Cesium Iodide (CsI)
B. a-Se
32
5. Which of the following is not considered a scintillator?
A. Gd2O2S
B. CsI
C. a-Se
D. None of the above
C. a-Se
33
6. Flat-panel detectors that use indirect conversion technology convert
A. electrical signals to light
B. light to x-rays
C. x-rays to electrical signals
D. x-rays to visible light
D. x-rays to visible light
34
7. Indirect conversion in flat-panel detectors is a ____-step process
A. One
B. two
C. three
D. four
B. two
35
8. Detector performance is measured with all of the following except
A. spatial resolution
B. observation of flow contrast objects in a phantom
C. DQE
D. contrast
D. contrast
36
9 .Possible causes of image lag include all except
A. rapid succession images
B. overexposure
C. lack of beam attention
D. underexposure
D. underexposure
37
10. All of the following statements are true except:
A. As the detector ages, the number of dead pixels increases
B. Software programs identify and isolate dead pixels
C. Interpolation uses information from surrounding pixels to "fill in" missing information
D. Dead pixels at the edge of the detector are easily identified
D. Dead pixels at the edge of the detector are easily identified
38
11. The absorption material can be attached to the pixel array electrically or physically
A. True
B. False
A. True
39
12. All flat-panel detector systems have the ability to take images faster than the detector can accommodate
A. True
B. False
B. False
40
13. Which statement best describes a charge-coupled device (CCD)?
A. It is the oldest direct conversion technology that is still in use today
B. It is the oldest direct conversion technology with limited use today
C. It is the oldest indirect conversion technology that is no longer used in medical imaging
D. It is the oldest indirect conversion technology used in a variety of image capture applications
D. It is the oldest indirect conversion technology used in a variety of image capture applications
41
14 A device that acts like a camera in an indirect conversion detector is known as a
A. CCD
B. field-effect transistor
C. CMOS
D. thin-field transistor
A. CCD
42
15. Which statement best describes a capacitor?
A. It converts x-ray photons to light
B. It converts light to an electrical charge and stores it
C. It converts x-ray photons to light and stores it
D. It stores light and converts it from an analog to a digital signal
C. It converts x-ray photons to light and stores it
43
16. Which of the following statements about scintillators is true?
A. All scintillators absorb the same amount of x-ray photons
B. The amount of x-rays absorbed depends on the type of scintillator
C. Structured phosphors produce more light spread
D. Unstructured phosphors are more efficient
B. The amount of x-rays absorbed depends on the type of scintillator
44
17. The readout process requires that _______ and _______
A. electrons flow freely when the gates are open; voltage stays consistent
B. the flow of electrons is timed; voltage stays consistent
C. electrons flow freely when the gates are open; multiple voltage changes occur
D. the flow of electrons is timed; multiple voltage changes occur
D. the flow of electrons is timed; multiple voltage changes occur
45
18. The most common types of noise that affects image quality include all of the following except
A. quantum noise
B. statistical noise
C. "dark" current noise
D. amplification noise
A. quantum noise
46
19. When compared with a CMOS, CCDs
A. are less light sensitive
B. are more susceptible to noise
C. use more than 100 times the power
D. are inexpensive to manufacture
C. use more than 100 times the power
47
20. The most popular base material used in integrated circuits is
A. selenium
B. sulfur
C. silicon
D. tellurium
C. silicon
48
21. A detector in which each pixel has its own amplifier is known as a
A. CCD
B. field-effect transistor
C. CMOS
D. thin-field transistor
C. CMOS
49
22. A highly efficient indirect conversion system that takes up less fill space than CCDs is known as a(n)
A. analog to digital converter
B. field-effect transistor
C. CMOS
D. thin-field transistor
C. CMOS
50
23. The indirect conversion detector system that requires optical coupling and image size reduction is known as a
A. CCD
B. field-effect transistor
C. CMOS
D. thin-field transistor
A. CCD
51
24. When specialized pixels in a complementary metal oxide silicon system are struck with x-ray photons
A. the x-ray photons are converted into light
B. light photons are stored in capacitors
C. light photons are converted into electrical charges
D. All of the above
D. All of the above
52
25. Quantum efficiency is a measurement of the
A. amount of electron-hole pairs held by the electrostatic force
B. percentage of light that is absorbed
C. amount of electrons produced relative to the incident light from the scintillator
D. total amount of light that is absorbed
D. total amount of light that is absorbed
53
26. Some advantages to CCDs include
A. less expensive to manufacture
B. module design makes repairs and upgrades easy
C. demagnification capabilities
D. a and c only
E. All of the above
D. a and c only
54
27. The number of electron-hole pairs produced is related to the amount of light absorbed
A. True
B. False
A. True
55
28. The polysilicon layer within a CCD acts as an insulator
A. True
B. False
B. False
56
29. CCDs use more power than CMOS
A. True
B. False
A. True
