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2403 Physics > Chapter 10 Exam > Flashcards

Chapter 10 Exam Flashcards

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1
Q

What represents the latent image in a PSP CR system?
a. Electrons trapped in conduction band
b. Ionized silver halide crystals
c. Scattered photons in the patient
d. Chemical reaction in the processor

A

a. Electrons trapped in conduction band

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2
Q

Which PACS storage option offers the fastest retrieval of data?
a. Offline
b. Nearline
c. Online
d. All are equal in retrieval speed

A

c. Online

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3
Q

Which of the following controls brightness of a digital system?
a. mAs
b. kVp
c. The display monitor
d. Room lighting

A

c. The display monitor

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4
Q

Rescaling a digital image adjusts the histogram to reflect which of the following?
a. kVp
b. mAs
c. LUT
d. VOI

A

d. VOI

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5
Q

Which of the following is used by both forms of indirect cassetteless systems?
a. Scintillator
b. CCD
c. Optics
d. TFT

A

a. Scintillator

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6
Q

Which of the following is used by both forms of indirect cassetteless systems?
a. Direct capture DR system
b. Indirect capture DR system
c. CR system
d. Cassette-based system

A

a. Direct capture DR system

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7
Q

Which component of the CR reader digitizes the signal?
a. Photodetector
b. ADC
c. Optics
d. Laser

A

b. ADC

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8
Q

The emission of light by a phosphor when exposed to a laser is known as _____
a. Phosphorescence
b. Sensitometry
c. Conversion efficiency
d. Photostimulable luminescence

A

d. Photostimulable luminescence

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9
Q

What is the phosphor for CR (PSP)?

A

Barium fluorohalide (turbid)

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10
Q

How do we get the CR image off of the cassette?

A
  • The phosphor is ionized when exposed to x-rays, approx half the liberated electrons are trapped in the conduction band.
  • The plate I then scanned in the reader, the energy is released and converted to an electronic signal becoming a manifest image
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11
Q

digital receptor’s response to exposure is linear and the range of exposures is very wide (dynamic range)

A

Linear response

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12
Q

Non-linear response

A

CR

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13
Q

Digital detectors are separated into small individual components termed:

A

detector elements (DELs)

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14
Q

the size of individual DELs is referred to as the

A

pixel pitch

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15
Q

the matrix size is the number of _____ in each direction on the detector

A

DELs

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16
Q
  • At the time of processing the energy of the trapped electrons is released by exposure to a laser in this process
  • Release of stored energy within a phosphor by stimulation with visible light, to produce a luminescent signal
A

Photostimulable luminescence

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17
Q

an automatic function of the system that occurs before the image is displayed, the human eye hasn’t seen it yet

A

Pre-processing

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18
Q

computer software operations that allow manual manipulation of the displayed image

A

Post-processing

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19
Q
  • An integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to a neighboring capacitor
  • Can respond to a wide range of light intensities
    Associated with indirect capture
A

Charged-coupled device (CCD)

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20
Q
  • The direct method uses amorphous selenium photoconductor and a TFT array
  • Before exposure an electric field is applied via the bias electrode across the surface of the amorphous selenium layer
  • During exposure, x-rays are absorbed by the amorphous selenium and electric charges are created in proportion to received x-ray exposure
  • The charges are stores in capacitors attached to TFTs where they are amplified and converted to digital code
A

Direct Digital Radiography (DDR)

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21
Q

What systems use cassettes and a processor?

A

Computed radiography (CR)

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22
Q

CR cassette layers top to bottom

A

Protective layer
Phosphor layer
Reflective layer
Conductive layer
Support layer

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23
Q

a thin layer of plastic to protect the phosphor layer

A

Protective layer

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24
Q

the heart of the plate and contains the phosphor, which is usually of the barium fluorohalide family and europium activated, may be turbid or structured

A

Phosphor layer

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25
Q

reduces and conducts away static electricity

A

Conductive layer

26
Q

a sturdy material to give some rigidity to the plate

A

Support layer

27
Q

random distribution of phosphor crystals within the active layer and can be used with both CR and DR systems

A

Turbid

28
Q

columnar phosphor crystals within the active layer resembling needles standing on end and packed together

A

Structured

29
Q

These devices are scintillators made up of crystalline silicon matrix. Each detectors element has its own amplifier, photodiode, and storage capacitor and is surrounded by transistors

A

Complete mentary metal oxide semiconductor (CMOS)

30
Q

A material that absorbs x-ray energy and emits visible light in response

A

Scintillator

31
Q

A process in which several CCD detectors abut to create on large detector

A

Tiling

32
Q

sequence of events for Indirect DR

A

x-ray > phosphor (scintillator) > visible light > photodetector > TFT > digital signal

33
Q

sequence of events for Direct DR

A

x-ray > electronic / digital signal

34
Q

A liquid that can be painted onto a substrate (foundation or underlying layer), is the material that makes flat-panel detectors possible

A

Amorphous silicone

35
Q
  • Captures the remnant beam through a detector array and transfer it to a computer for almost immediate processing and viewing
  • Involve the use of a scintillator that converts x-rays to light and then to an electronic signal
A

Indirect capture

36
Q

Does not use a scintillator, it uses a photoconductor and TFT array, thereby avoiding the loss of resolution caused by indirect capture

A

Direct capture

37
Q
  • A graphic representation of a data set, this graph represents the number of digital pixel values versus the relative prevalence of those values in the image
  • The x-axis represents the amount of exposure and the y-axis represents the incidence of pixels for each exposure level
A

Histogram

38
Q
  • The primary factor influencing contrast with digital systems
  • Histograms of luminance values used as a reference to evaluate the input intensities and assign predetermined grayscale values-VOI, rescaling occurs at this stage
A

Look up table (LUT)

39
Q

VOI

A

Values of interest in histogram

40
Q

Displayed as a single numerical value, which is represented as a single brightness level on a computer monitor

A

Pixel

41
Q

Refers to the range of exposure intensities an image receptor can accurately detect

A

Dynamic range

42
Q

The range of exposure values to the receptor that produce an acceptable range of densities for diagnostic purposes and are consistent with exposure rates as low as reasonably achievable

A

Exposure latitude

43
Q

The adjusting of the image by the computer program to present an image of predetermined image brightness

A

Rescaling

44
Q
  • A measure of exposure in air, followed by computation to estimate absorbed does to the patient, measured by a ____ meter embedded in the collimator
  • This value depends on the exposure factors and field size and is expressed in centigray-meter squared (cGY-m2)
A

Dose Area Product (DAP)

45
Q

System’s ability to preserve signal contrast

A

Modulation transfer function (MTF)

46
Q
  • The highest spatial frequency that a digital detector can record
  • Determined by the sampling frequency of CR systems and the DEL spacing of DR systems
A

Nyquist Frequency

47
Q
  • Focuses on the display monitors and viewing equipment
  • The AAPM published an online report, Report No. OR-03, to provide guidelines for proper performance of display devices intended for medical use, this report presents 26 test patterns
A

DR Quality Control

48
Q

Overall visual appearance: this test looks at general image quality and for the presence of any artifacts

A

uses the TG18-QC test pattern

49
Q

Resolution tests: assesses the system’s ability to display images of different parts of an image with high fidelity

A

TG18-QC and TG18-CX test patterns

50
Q

Reflection: evaluates the ambient light contribution to the light reflected by the display monitor

A

TG18-AD test pattern

51
Q

An electronic network for communication between the image acquisition modalities, display stations, and storage

A

PACS

52
Q

A common language used by different systems for communication

A

DICOM

53
Q

an expression of the radiation exposure level that is required to produce an optimal image

A

detective quantum efficiency (DQE)

54
Q

represents the exposure at the detector relevant to the region being imaged and is defined by the signal-to-noise ratio (SNR)

A

exposure index (EI)

55
Q

the target reference exposure obtained from a properly exposed image receptor

A

target exposure index (EIT)

56
Q

a measure of deviation of the EI from projection-specific EIT values

A

deviation index (DI)

57
Q

equal to one half the nyquist frequency

A

spatial resolution

58
Q

detector’s ability to resolve small structures

A

limiting spatial resolution (LSR)

59
Q

what are the two ways to effectively control scatter and radiation’s effect on the image?

A

collimation and grid use

60
Q

electronic component that includes the readout, charge, collector
act as individual switches that allow the pixels to change state rapidly

A

thin film transistor (TFT)

61
Q

what radiology method uses barium?

A

CR

62
Q

what radiology method uses selenium?

A

direct digital

2403 Physics (8 decks)

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