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Principles III > ASRT Digital Imaging Module 1 > Flashcards

ASRT Digital Imaging Module 1 Flashcards

1
Q

Primary Beam consists of photons of __________ energies. With different abilities to ____________.

A
  1. varying

2. penetrate tissue in a patient

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2
Q

The tissues in the human body have varying abilities to _______ or _______ x-ray photons.

A

attenuate or absorb

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3
Q

The beam containing useful and diagnostic information is the _____________.

A

remnant beam

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4
Q

In film imaging, the chemical interactions are between the _____________ and the _____________.

A
  1. processing solutions

2. emulsion/recording layer (of the film)

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5
Q

Digital images allow us to see structures that would have required ______________ with film technology.

A

additional imaging

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6
Q

Film screen is always considered __________.

A

analog

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7
Q

Analog IR has 3 components.

A
  1. cassette
  2. intensifying screen
  3. film
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8
Q

In analog, the _______ is the recording device.

A

film

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9
Q

the _____________________ turn x-rays into light, which in turn makes up the latent image.

A

intensifying screens

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10
Q

Film digitizers are ______ efficient in measuring slight changes in film opacity.

A

very

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11
Q

The ______________________ changes the continuous signal into a discrete signal.

A

ADC (analog-to-digital converter)

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12
Q

The process of assigning numeric values to a signal is _______________.

A

quantization

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13
Q

The number of gray levels in a bit depends on its ____________.

A

bit depth

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14
Q

formula for calculating bit depth

A

2^x = # of shades of gray

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15
Q

bit depth for ADC used in diagnostic imaging is _________

A

12-32

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16
Q

The ability to distinguish objects adjacent to each other is measured with _________________.

A

line pairs per millimeter

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17
Q

higher resolution = individual lines are ____________

A

separate and distinct

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18
Q

How is pixel size is measured?

A

from side to side of a single pixel

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19
Q

How is pixel pitch measured?

A

from the center of one pixel to the center of an adjacent pixel

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20
Q

A typical matrix size for a digital radiograph is _______ x _______ with a bit depth of ____.

A

3000 x 3000; bit depth of 12

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21
Q

A typical matrix size for CT is _____ x _____ with a bit depth of ___.

A

512 x 512; bit depth of 16

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22
Q

2 types of Photostimulable Phosphor plate systems

A

cassette-less and cassette-based

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23
Q

2 types of Flat-Panel Receptors

A

scintillator based and nonscintillator based

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24
Q

Define scintillation (in radiography) and its process

A

the ability of a material to absorb x-ray energy and produce light; the light is then converted to electrons which create an image

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25
Q

3 important parameters used to assess performance of receptors

A
  1. absorption efficiency
  2. conversion efficiency
  3. detective quantum efficiency (DQE)
26
Q

What does Absorption Efficiency measure?

A

the percent of energy that strikes a receptor that is actually absorbed

27
Q

What does Conversion Efficiency measure?

A

the percent of energy absorbed by the receptor that is converted to usable output

28
Q

What is Detective Quantum Efficiency?

A

DQE is a product of absorption and conversion efficiencies

29
Q

What are the two types of phosphor types for PSP?

A
  1. Turbid (randomly distributed)

2. Needle (columnar)

30
Q

Needles have less __________ ___________ when compared to columnar. This helps improve ________ ________.

A
  1. light divergence

2. spatial resolution

31
Q

How long can a latent image remain on a PSP detector?

A

several hours (roughly 8)

32
Q

PSP latent image can lose ___% of its energy in ___ hours.

A

25% in 8 hours

33
Q

What holds the electrons elevated in the higher energy state?

A

conductive band

34
Q

Where do the electrons go while in the resting state?

A

valence band

35
Q

T/F: The reader’s laser light releases all electrons from the F-Trap.

A

False, some are left behind

36
Q

As the plate travels thru the reader, how is the laser light set up?

A

it is pointed towards an optic scanner

37
Q

Newer plate readers are line-scan devices which have ______ _______ in a row.

A

several lasers

38
Q

The newest type of PSP reader is the ___________.

A

dual-sided

39
Q

Step-by-step process of signal conversion (starting with light emitted from electrons in F-trap)

A
  1. photodetector captures light from PSP plate
  2. converts light intensities to electronic signal
  3. signal sent to ADC
  4. signal undergoes sampling and quantization
40
Q

Photoconductive material used for (1) scintillator-based and (2) non-scintillator-based

A
  1. Amorphous Silicon (aSi)

2. Amorphous Selenium (aSe)

41
Q

TFT

A

Thin-Film Transistors; complex circuit device that collects electrons

42
Q

DELs

A

detector elements of TFT array; a DEL collects electrons that represent the exposure level

43
Q

Fill Factor

A

used to assess the quality of the FPD; a ratio of the radiation-sensitive area to the non-. 80% Fill Factor means 80% of the detector area is devoted to sensing radiation

44
Q

Fill Factor affects a detector’s ______ and _______.

A
  1. spacial resolution

2. signal-to-noise ratio

45
Q

Noise affects the observer’s ability to perceive ______ ______ within an image.

A

structural details

46
Q

Indirect TFT systems are cassette based. The cassette’s scintillator system is made of _________ or ________.

A

Cesium Iodide or Gadolinium OxiSolfate

47
Q

T/F: CCD requires a scintillator.

A

true; can be CsI or GdOS

48
Q

3 Advantages of CCD receptors

A
  1. wide range of exposure settings
  2. respond to lower light levels from scintillator
  3. produces images quickly and instantly refreshes for the next image (good for fluoro)
49
Q

4 steps for CCD image capture

A
  1. scintillator converts x-rays to light
  2. light photons reflect off mirror to focusing lens which get directed to CCD
  3. CCD converts light signal to electrical signal
  4. electrical signal is sent to ADC
50
Q

In a CMOS detector, the light from the scintillator is directed to the CMOS by a ______________.

A

fiber-optic cable

51
Q

If a detector has a higher spatial frequency, it represent a _________ number of viewable objects on an image

A

larger

52
Q

Spatial Resolution is measured in _________ per _____

A

Line Pairs per mm

53
Q

The _________ determines the line pairs per mm we can see.

A

size of the pixels

54
Q

Better recorded detail (resulting from higher sampling frequency) is ideal for __________ exams.

A

extremity

55
Q

For ____________ detector, the size of the detector determines spatial resolution.

A

flat-panel detector

56
Q
  1. DEL size of 200 microns = spatial resolution of _____

2. 100 microns =

A
  1. 2.5 Lp/mm

2. 5 Lp/mm

57
Q

T/F:
PSP w/200 micron pixels = FPD w/DEL of 200
however, PSP w/100 does not equal FPD w/100

A

true

58
Q

Nyquist Frequency/Theorem

A

determines level of spatial resolution for IR

59
Q

Analog receptors produce acceptable images between ___% underexposed to ___% overexposed.

A

30% under, 50% over

60
Q

Digital receptors produce acceptable images between ___% underexposed to ___% overexposed.

A

50% under, 100% over

61
Q

The only visual cue a tech has to indicate underexposure is _____ _____.

A

quantum noise (50%+ underexposed)

62
Q

For a digital image overexposed, ________ ________ is decreased.

A

image contrast (100%+ overexposed)

Principles III (1 decks)

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