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Clinical Medicine > Computed Tomography > Flashcards

Computed Tomography Flashcards

1
Q

Computed Tomography (CT)

A

non-invasive x-ray technology with a computer

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2
Q

What does it provide?

A

detailed, digital, cross-sectional images of the body in any plane = “slices”

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3
Q

True or False: A CT is relatively free from superimposition of different tissues.

A

True

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4
Q

What are the two components necessary to take a CT?

A
  1. high intensity x-ray tube
  2. x-ray imaging detectors
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5
Q

What houses the components necessary to take a CT image?

A

the gantry

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6
Q

What function does the motorized patient table play during a CT?

A

moves the patient through the circular opening in the CT machine continually during the examination

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7
Q

True or False: The process to obtaining a CT is similar to obtaining a radiograph.

A

true

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8
Q

Describe “the science” behind a CT.

A
  • during the rotation, x-ray source produces a fan-shaped beam of x-rays
  • attenuation occurs
  • imaging detectors create a snapshot
  • many snapshots at different angles are collected in one rotation
  • snapshots sent to computer
  • computer reconstructs snapshots into cross-sectional images of the tissues
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9
Q

True or False: Radiographs carry a higher radiation dose than a CT scan.

A

false - CT scans have a higher radiation dose than radiographs.

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10
Q

What is the issue with ordering a CT on a child?

A

larger window for opportunity for expression of radiation damage due to children being more sensitive to radiation than adults

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11
Q

How can we accommodate pediatric patients that absolutely need a CT?

A

change the settings on the CT to adjust radiation dose to a smaller body size

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12
Q

What is key when considering ordering a CT for a pediatric patient?

A

order ONLY IF NECESSARY!

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13
Q

2 to 3 CT head scans equals how many mGy to the brain?

A

50-60

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14
Q

Children with a greater exposure reported a ______________ increase in risk of brain tumor or leukemia than those with 5mGy exposure.

A

threefold

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15
Q

Do the same principles of radiodensity and radiographic density that we utilize with x-rays apply to CT scans?

A

yes

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16
Q

What are the two characteristics of object radiodensity?

A

atomic #
Thickness

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17
Q

Relative radiodensity are displayed based on the average values of what scale?

A

hounsfield scale

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18
Q

how does the computer apply average values to display overlapping tissues?

A

overlapping tissues are displayed in one shade of grey

19
Q

radiodensity represents sum of ____________ & ____________ tissues

A

osseous & tendinous

20
Q

Hyperdense represents __________ and appears ________.

A

bone, white

21
Q

Isodense represents __________ and appears _________.

A

brain matter/muscle tissue, grey

22
Q

Hypodense represents _________ and appears __________.

A

fluid/fat/air, grey-black or black

23
Q

How may metals impede image interpretation?

A

metals lead to streaking artifacts

24
Q

In a CT, how is an axial view read?

A

anatomic position from the feet up

25
Q

In a CT, how is a sagittal view read?

A

from left to right

26
Q

In a CT, how is a front view read?

A

anatomic position facing the viewer

27
Q

When would you choose to obtain a CT for a musculoskeletal concern?

A
  • subtle fx
  • complex fx
  • when MRI is contraindicated
  • infectious processes
28
Q

What is the preferred imaging method for a suspected spinal fx?

A

CT

29
Q

What are the ABC’S when viewing a CT?

A

Alignment
Bone density
Cartilage joint or canal spaces
Soft tissues

30
Q

Where should cortical bone be more dense?

A

along the margins

31
Q

What are upper extremity indications for a CT?

A
  • shoulder complex fx
  • elbow complex fx
  • wrist/hand complex fx
32
Q

When would you choose to obtain a CT for a neurological concern?

A
  • acute trauma to the brain (bleeding & hemorrhaging)
  • tumor, cysts, abscesses
  • spinal cord eval when MRI is contraindicated
33
Q

In the brain, how does grey and white matter appear?

A

grey matter appears lighter than white matter

34
Q

What occurs in the grey matter?

A

where the processing happens (cell bodies, dendrites, axon terminals)

35
Q

What occurs in the white matter?

A

communication (axons)

36
Q

In an acute hemorrhage, how does blood appear on a CT?

A

bright white (hyperdense)

37
Q

In a subacute hemorrhage, how does blood appear on a CT?

A

fades to grey (isodense)

38
Q

In a chronic hemorrhage, how does blood appear on a CT?

A

fades to darker grey/black (hypodense)

39
Q

Can a chronic hemorrhage or ischemic stroke be seen on an MRI?

A

no

40
Q

CT arthrography

A

intravenous injection that is specific to a joint

41
Q

CT myelogram

A

CT imaging + myelography

injection of water-soluble contrast medium into posterior subarachnoid space, then performing a CT scan

42
Q

A CT myelogram enhances the ability to visualize abnormalities affecting the -

A

spinal cord, spinal canal, spinal nerve roots & blood vessels of the spinal cord

43
Q

Is a CT myelogram commonly used?

A

no - not since the invention of the MRI.

it is an invasive examination w/increased risk

44
Q

When is CT myelogram indicated over MRI?

A

contraindication to MRI

Clinical Medicine (5 decks)

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