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Radiology! > Alternative imaging modalities > Flashcards

Alternative imaging modalities Flashcards

1
Q

Name the 4 alternative imaging modalities.

A
  1. CT computed tomography
  2. MRI magnetic resonance imaging
  3. ultrasound
  4. nuclear medicine
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2
Q

what are the main issues with plain radiographs? 7 things

A
  • limited use for soft tissues
  • ionising radiation
  • sensitivity and specificity
  • only show retrospective view (active or arrested caries?)
  • significant demineralisation necessary to detect change.
  • 2D image = superimposition & multiple view needed for localisation
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3
Q

give 3 positives of plain radiographs.

A
  1. cheap
  2. readily available
  3. relatively low dose
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4
Q

what kind of radiation is used for CT scan?

A

Xray photons

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5
Q

how does the CT scanner move?

A

it rotates around the patient with an X-ray beam at one side of the ring and an X-ray receptor at the other side

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6
Q

what does the CT scanner do as it rotates around the patient?

A

splits the patient into little cubes called voxels

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7
Q

define a voxel

A

pixels with volume

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8
Q

what is the size range for a voxel?

A

0.008-0.04 mm

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9
Q

what is the benefit and disadvantage of using small voxel?

A 
good = high definition 
bad = greater exposure time = higher dose
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10
Q

how is the CT number determined?

A

the CT scanner works out how much attenuation of the beam has occurred in each voxel

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11
Q

In a CT what colour is 1. bone 2. soft tissue 3. air

A
  1. white 2. grey 3. black (just like X-ray)
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12
Q

Define windowing?

A

manipulation of an image to allow bettie visualisation of more subtle changes between tissues.

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13
Q

what 2 types of windowing can you get?

A

Soft tissue windowing and bone windowing

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14
Q

what shows up in the soft tissue windowing?

A

bone is totally white

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15
Q

what shows up in the bone windowing?

A

the bone is different shades depending upon the density

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16
Q

what are the 4 advantages of a CT scan?

A
  1. images both bone and soft tissue
  2. speed - faster than MRI
  3. multiplanar
  4. low cost and more available compared to MRI
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17
Q

what are the 4 disadvantages of a CT scan?

A
  1. high dose to patient
  2. artefacts will interfere (i.e. amalgam)
  3. expensive in comparison to plain radiograph
  4. allergy to iodine based intravenous contrast commonly used to distinguish tissues
18
Q

give reasons for the use of CT scans in the head and neck (6)

A
  • intracranial bleed, infarct, tumour
  • trauma (orbit, cranial base, cervical spine)
  • orthognathic surgery and treatment planning
  • evaluation of bony lesions
  • salivary glands
  • neoplasia (primary and metastases)
19
Q

what does CBCT stand for?

A

cone-beam computer tomography

20
Q

what is CBCT good for looking at?

A

bone (not soft tissues)

21
Q

3 advantages of CBCT

A
  1. 3D
  2. multiplanar
  3. same dose as conventional CT
22
Q

what is the difference between CBCT and normal CT?

A

normal CT = computer takes multiple slices (32 or 64) and adds together

CBCT = computer takes image as a whole volume and you split it up

23
Q

what are the 4 planes that data can be reconstructed into?

A
  1. axial
  2. coronal
  3. sagittal
  4. specific ones e.g. panoramic
24
Q

Indications for use of CBCT

A
  • Trauma
  • Pathology
  • Implantology
  • endodontics
  • localisation of impacted teeth that affect adjacent structures
25
Q

What does MRI stand for?

A

magnetic resonance imaging

26
Q

what 3 things make give an MRI scan?

A

protons (water) & strong magnetic field & radio frequency pulses

27
Q

what is MRI scan good at viewing?

A

The soft tissues and bone

28
Q

what colour is bone and dental tissues on an MRI scan?

A

Black

29
Q

what are the two types of MRI scan?

A

T1 and T2 weighted

30
Q

what is the T1 weighted MRI used for and what colour is water in it?

A

good for anatomy and water is dark

31
Q

what is the T2 weighted MRI used for and what colour is the water?

A

good for looking at pathology and bright water

32
Q

why is T2 weighted MRI better for looking at pathology?

A

with pathology you get increased water so these areas will show up brightly

33
Q

3 advantages of MRI

A
  1. no ionising radiation
  2. excellent for looking at soft tissues (and bone)
  3. multiplanar
34
Q

what are the 6 diadvantages of MRI

A
  1. many contraindications
  2. danger associated with strong magnetic field
  3. availability and expense
  4. long scan time
  5. claustrophobia
  6. very noisy
35
Q

Ultrasound is created by what?

A

high frequency sound waves >13MHz

36
Q

what are the 4 contraindications for using an MRI scan on a patient?

A
  1. pacemakers (may switch on/off)
  2. heart valves (old ones moved due to magnet)
  3. 1st trimester of pregnancy
  4. aneurysm clip (will heat it up)
37
Q

the benefits of ultrasound are.. (5)

A
  • multiplanar
  • no ionising radiation
  • no adverse effects known
  • real time images
  • ideal for ST
38
Q

diadvantages of ultrasound (4)

A
  • operator dependant
  • difficult to interpret
  • superficial tissues only
  • won’t penetrate bone
39
Q

the probe for an ultrasound is the … and the …

A

the source and the receptor

40
Q

uses for ultrasound are..

A
  • neck swelling
  • salivary glands (intraglandular lesions and calculus)
  • guidance for biopsy/drainage
  • blood flow testing in lesions

Radiology! (10 decks)

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