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Imaging Applications and Quality > Final Exam > Flashcards

Final Exam Flashcards

1
Q

What is the first scan that is done following the presentation of symptoms of a stroke?

A

Non contrast CT

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2
Q

Why should we not start the examination of a stroke protocol with contrast?

A
  1. Don’t want to miss/mask a bleed
  2. We want to determine if it is an ischemic or hemorrhagic stroke
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3
Q

What vessel does CTA access?

A

The arteries

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4
Q

What are the advantages of preforming a CTA of the head following symptoms of a stroke?

A

-Non-invasive
-Quick
-Widely available.

(The time saving nature of CTA is an advantage in the case of patients suspected of suffering from an acute stroke in which treatment decisions must be made quickly.)

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5
Q

What is the goal of CTA?

A
  1. To accurately measure the stenosis of carotid and vertebral arteries and their branches.
  2. To evaluate the structure of the Circle of Willis
  3. To detect other vascular issues, such as occlusions or dissections.
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6
Q

What is the purpose of performing a CT Perfusion following the presentation of symptoms of a stroke?

A

Allows quantitative evaluation and assessment of regional cerebral perfusion. With a CT perfusion study, we can determine where the core and penumbra is.

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7
Q

How does infarcted tissue appear on a perfusion study?

A

-Decrease in cerebral blood flow
-Decrease in cerebral blood volume
-Increase in time to peak
-Increase in mean transit time

Tissues that match the above parameters are not viable, even if reperfusion is attempted.

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8
Q

How does penumbral tissue appear on a perfusion study?

A

-Decease in CBF
-Cerebral blood volume is normal or higher
-Increase in time to peak TTP
-Increase in mean transit time

Tissue that matches the above parameters are viable; salvageable if normal CBF is returned.

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9
Q

What pathologies in the head and neck of a patient can result in neurological deficits?

A

-Strokes/CVA
-Trauma (mass effects, bleed)
-Intracranial hemorrhage
-Brain tumours/mass/lesions/metastasis
-Abscess
-Meningitis

(cerebrovascular disorders)

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10
Q

What are the commonly selected regions for ROI placement following acquisition of CTP images of the head? Why?

A

-The anterior cerebral artery is commonly used to obtain arterial ROI because it travels along the axial plane, and is easy to locate.
-The superior sagittal sinus is usually used to obtain the venous ROI.

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11
Q

What is the window width?

A

1000

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12
Q

What is the window level?

A

0

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13
Q

What is the window width?

A

300

-Right=150
-Left=150
-150+150=300 WW

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14
Q

What is the window level?

A

WL=200

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15
Q

What is the window width?

A

WW=300

150+150

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16
Q

What is the window level?

A

0

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17
Q

What does the window width determine?

A

Determines the number of Hounsfield units (CT numbers) represented in an image

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18
Q

What is window level?

A

The center CT value of the assigned window width.

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19
Q

What window settings are seen in images A and B?

A

A=Lung window
B=Mediastinal window

Can’t get a complete picture without seeing these two window

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20
Q

What structures are seen well with a lung window? What are the limitations?

A

-Detail of the lung parenchyma seen
-Limitations=can’t appreciate mediastinal structures

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21
Q

What structures are seen well with a mediastinal window? What are the limitations?

A

-Clearer picture of the mediastinal structures
-Limitations=Don’t see a lot of the lung detail

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22
Q

What are the two types of reconstructions?

A

1.Retrospective
2.Prospective

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23
Q

Define reconstruction:

A

Used when raw data is manipulated to create an image.

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24
Q

Define reformation:

A

Used when image data are assembled to produce images in different planes, or to produce 3D images.

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25
Q

T/F

Raw data includes everything in the SFOV

A

True

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26
Q

Describe prospective reconstruction.

A

-Manipulating raw data so that an initial image may be formed. Prospective reconstruction is planned before actual scanning begins.

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27
Q

What are some examples of prospective reconstruction?

A

-For example, selecting the protocol (which will determine the technique, algorithm, SFOV, slice thickness etc.) and setting the DFOV.

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28
Q

Describe retrospective reconstruction.

A

Can only be performed on the operator console (scanner). Raw data is needed. CT scanner memory-limited-stays days, weeks, etc.)

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29
Q

What are some examples of retrospective reconstruction?

A

-Selecting the wider SFOV from raw data from the DFOV
-image centering and reconstruction algorithm.

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30
Q

What phantoms are used for QC testing in mammography?

A

-Digital Mammography Uniform Phantom (DMUP)
-Digital Standard Breast ACR Phantom.

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31
Q

How thick are DMUP phantoms? What are they made of?

A

4 cm thick slab of PMMA (acrylic)

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32
Q

What should the WL generally be set at?

A

The window level should be set at a point that is roughly the same value as the average attenuation number of the tissue of interest.

(For example, a window level setting that is intended to display lung parenchyma will be approximately −600 because air-filled lung tissue measures around −600 HU.)

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33
Q

Any values above the selected window width appear what colour?

A

White

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34
Q

Any values below the selected window width appear what colour?

A

Black

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35
Q

What window width (narrow or wide) should be used when imaging tissue types that vary greatly, when the goal is to see all the various tissues on one image?

A

Wide window width

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36
Q

Would the lungs need a wide window width or a narrow window width?

A

Wide window width (it is necessary to see low- density lung parenchyma as well as high-density, contrast enhanced vascular structures (within the lungs)

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37
Q

What window width, (narrow or wide) should be used when imaging similar densities?

A

Narrow window width

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38
Q

Would the brain require a wide or narrow window width?

A

Narrow window width

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39
Q

Why can’t a wide window width be used with tissues of similar densities?

A

You wouldn’t be able to tell the structures apart because of all the shades of gray if a wide window width was used for similar densities.

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40
Q

What tool is shown here?

A

Reference Image Function

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41
Q

What post-processing tool is shown here?

A

MPRs

42
Q

What post processing tool is shown here?

A

MPRs

43
Q

What post-processing tool is shown here?

A

MPRs

44
Q

Read over the following post-processing techniques used in CT:

Don’t memorize, just review

A

-Window settings
-Region of interest tool
-Distance measurement tool
-Reference Image Function
-Image Magnification
-MPR (multi-planar reformation)
-Curved Planar Reformations (CPRs)
-3D reformation
-Shaded Surface Display (Surface Rendering)
-Volume Rendering (VR)
-Endoluminal Imaging
-Maximum Intensity Projections (MIPs)
-Minimum Intensity Projection (MinIP)
-Region of Interest Editing

45
Q

What is the purpose of MPR?

A

Done to show anatomy in various planes (axial, coronal, sagittal, oblique).

46
Q

Where are MPR’s created?

A

Created at operator console or separate workstation

47
Q

T/F

MPR’s preserves the original CT attenuation values.

A

True

48
Q

What dimension are MPR’s?

A

2D

49
Q

What techniques are required to be imputed for MPR’s?

A

Thickness of the MPR, the plane desired, and the incrementation of the resulting images.

(ex; spacing 2 and slice thickness 2=Will input 2 by 2 MPR)

50
Q

What are Scanner-Created (Automatic) MPRs?

A

Automatically generated MPR by the scanner software.

51
Q

What are the advantages of Scanner-Created (Automatic) MPRs?

A

Saves the technologist time & ensures they are done.

52
Q

What type of data does image magnification use?

A

Uses image data, not raw data

53
Q

What is the purpose of image magnification?

A

To make the existing image appear larger and allows relevant clinical detail to be more easily seen and measured

54
Q

T/F

Image magnification does not improve resolution.

A

True

55
Q

As DFOV decreases, what happens to SR?

A

It increases

56
Q

T/F

A decrease in display field of view increases the size of the displayed image.

A

True

57
Q

What is the purpose of the reference image function tool?

A

The reference image function (scout image) displays the location of slices through slice lines in corresponding locations on the scout image. This feature aids in localizing slices.

58
Q

T/F

Image magnification can be used as an alternative to correct DFOV selection.

A

False; magnification has inherent limitations and should not be used as an alternative to correct display field selection.

59
Q

According to SC35, what visual indicator displays are required for fluoroscopic systems?

A

-X-ray tube voltage
-X-ray tube current

60
Q

What is the purpose of a Chronometer on fluoroscopy machines?

A

Indicates the amount of time that the equipment has been emitting X-rays.

61
Q

What does the reset timer monitor on fluoroscopy machines?

A

Monitors the length of time the fluoroscopic x-ray tube is energized.

62
Q

How often does the reset timer go off?

A

Must go off every 5 minutes

63
Q

In CT, what QC tests need to be performed daily?

A

-Warm up
-Meters Operation: Meters and visual and audible indicators should be checked for proper function
-Equipment Condition
-Electronic Assessment of Electronic Display Devices

64
Q

What artifact is shown here?

A

Partial volume artifact

65
Q

What is the primary purpose of HRCT imaging of the chest?

A

Used to evaluate lung parenchyma in patients with known or suspected diffuse lung diseases such as emphysema and fibrosis.

Good for people with a known history and doing yearly check ups

66
Q

How does HRCT create high quality images of the chest?

A

By using edge enhancing algorithms used to get crisp images and is designed to display true architecture of the lung parenchyma

67
Q

Is HRCT using thinner or thicker slices? At what interval are the slices obtained?

A

Thinner slices-slices 10mm apart

68
Q

What percentage of the lung is scanned in HRCT?

A

10% of the lung parenchyma is scanned. (E.g., 1mm slice every 10 mm)

69
Q

What image has used HRCT?

A

The 2nd image

70
Q

Is post-processing possible with HRCT?

A

No

71
Q

What pathology is shown here?

A

-Dependent atelectasis

72
Q

Why might a patient receiving a scan of the thorax be scanned prone?

A

Done to confirm confirm dependent atelectasis

73
Q

What is atelectasis?

A

Atelectasis is the partial collapse of lung visualized as haziness or ground glass opacity.

74
Q

What is dependent atelectasis?

A

Not a collapse, just a collection of fluid that mimic’s atelectasis

75
Q

How does atelectasis (dependent or not) appear in a CT supine?

A

The portion of the lung closest to the scan table (dependent portion) may not inflate completely and appears hazy.

76
Q

How does positioning prone rule out atelectasis?

A

If the patient is positioned prone, and the haziness disappears and the dependent area inflates, atelectasis can be ruled out and dependent atelectasis becomes the diagnosis.

77
Q

Why is thorax imaging done on full inspiration?

A

When the lungs are fully expanded, the contrast between low attenuation aerated space and high attenuation lung structures is maximized.

78
Q

Why are CT expiratory scans of the chest performed?

A

Expiratory scans are used to look for areas of the lung that do not empty during expiration, which indicate small airway disease.

79
Q

T/F

The density gradient from the effects of gravity is more pronounced on expiratory images.

A

True

80
Q

What is the typical HRCT protocol?

A

Inspiratory supine, expiratory supine and an inspiratory prone.

81
Q

T/F

All HRCT scans can be done in helical mode as well as in axial slices.

A

False; The inspiratory supine image should be done in helical mode, but the additional images may be done in axial scan mode to reduce patient radiation exposure.

82
Q

When is a non-contrast CT of the chest indicated (examples of pathology)?

A

-Pulmonary nodules
-Screening
-Pleural effusion
-Pneumonia

83
Q

How can BHA be minimized in the SVC during CT pulmonary angiograms?

A

1.Saline flush
2.Scans being acquired in a caudo-crainial direction

84
Q

How does imaging in a caudo-crainial direction minimize BHA?

A

Avoids streak artifacts from dense contrast media in superior vena cava or subclavian vein, thus allowing time for the saline chaser to clear off the contrast to chest by the time imaging proceeds to that level.

85
Q

How does using a saline flush minimize BHA in the SVC?

A

Eliminates beam-hardening artifacts from the dense contrast media within the SVC by diluting contrast.

86
Q

What are the window settings in CT abdomen images?

A

Soft tissue, bone, lung window

87
Q

What are the window settings in head and face CT images?

A

Brain and bone window

88
Q

What is the standard window in CT head and face images?

A

Brain window

89
Q

What are the window settings in lung imaging in CT?

A

Lung window, mediastinal window

90
Q

What are the window settings in MSK and abdominal CT image?

A

Bone window and soft tissue window

91
Q

What artifact is shown here?

A

Cupping artifact from beam hardening

92
Q

What artifact is seen here?

A

Dark bands and streaks

93
Q

What artifact is seen here?

A

Dark bands and streaks

94
Q

What are the 4 types of artifacts in CT?

A

-Physics based artifacts
-Patient-based artifacts
-Scanner-based artifacts
-Reconstruction based artifact.

95
Q

What are the most important factors in avoiding CT artifacts?

A

Patient positioning and optimum selection of scanning parameters

96
Q

What do physics based artifacts result from?

A

Artifacts result from the physical processes involved in the acquisition of CT data.

97
Q

What are the 3 physics based artifacts?

A

-Beam hardening artifact
-Photon starvation
-Partial volume averaging

98
Q

What are the 2 types of artifacts can result from beam hardening?

A
  1. Cupping artifacts
  2. Streaks and dark bands
99
Q

Why does the beam hardening artifact occur?

A

Beam becomes “harder” as it passes through an object, because the low energy photons are absorbed more rapidly than the higher energy photons.

100
Q

Why does the cupping artifact occur?

A

More beam hardening in the middle because there is more tissue to attenuate, and therefore, less attenuation and darker in this area.

101
Q

Where do dark bands and streaks appear?

A

Dark bands or streaks can appear between two dense objects in an image or where contrast has been used

102
Q

Why do dark bands and streaks appear?

A

This occurs because a portion of the beam that passes through one of those objects at a certain tube positions is hardened less than when it passes through both objects at other tube positions.

Imaging Applications and Quality (16 decks)

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