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Radiology > LEC 2 - MRI + CT Scans > Flashcards

LEC 2 - MRI + CT Scans Flashcards

1
Q

What is the downside to radiography?

A

Not functional
Not cross sectional
Poor soft tissue appearance

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2
Q

What is the downside to ultrasound?

A

Not functional

Bad at seeing bone and lung

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3
Q

What are the four options for advanced imaging?

A

Nuclear imaging
Computed Tomography
Magnetic Resonance Imaging
Contrast Ultrasound

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4
Q

What is nuclear imaging used for?

A

Bone scans

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5
Q

What is the major difference between CT scan and normal radiography?

A

Rotating photon source
Rotating detectors
Computer constructs image

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6
Q

What do CT’s measure?

A

Attenuation

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7
Q

What is attenuation coefficient?

A

Degree to which x-ray intensity is reduced by material

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8
Q

How is the measurement called for CT?

A

Hounsefielf (HU)

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9
Q

What is HU’s based on?

A

Water = 0

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10
Q

What is the progression of HU units?

A 
Bone = + 
Water = 0 
Air = -
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11
Q

How do CT scanners work in regards to providing you information?

A

Each pixel given number that correlates to HU scale - this tells you what the substance is most likely

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12
Q

What color do you want the thing you are interested in to be?

A

Gray

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13
Q

What are the two things that you change on a CT scanner to get an image?

A

WL - Window level
– and –
WW - Window Width

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14
Q

how do you set a CT machine?

A

Set WL to the substance that you want to be gray

Set WW to the range that you would like tissues to be visable

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15
Q

What is the most important clinical reason to use a cone beam CT?

A

Thorax - Lung mass

GOLD STANDARD

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16
Q

What are the limitations to a cone beam CT?

A

only images in the transverse plane

VERYYYYYY SLOW

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17
Q

What is the clinical reasons for using a single slice helical CT?

A

Angiography

PSS + Masses + Thrombosis

18
Q

What are the limitations to using a single slice helical CT?

A

Slow

Only imaging in the transverse plane

19
Q

What are the limitations to the multislice CT?

A

none

20
Q

What is the best reason to use MRI?

A

to see brain + nervous system

NO ionization or radiation

21
Q

What is MRI good for in the body?

A

Soft tissue
– and –
Grey vs. White mater

22
Q

What is MRI bad for in the body?

A

Bone
– and –
Air

23
Q

What is the basic way in which a MRI works?

A

Makes a strong magnentic field
Causes protons to line up
RF pulse causes protons to act a certain way
Wobble = signal

24
Q

What are the two directions that the protons can line up?

A

Parallel
– and –
Anti-parallel

25
Q

What direction of magnetization can NOT be measured?

A

Longitudinal

26
Q

What is another name for the wobbling of the protons?

A

Precession

27
Q

What is RF pulse?

A

Radiofrequency pulse

caused by the rapid changing of magnetic and electrical fields

28
Q

What are the types of RF pulses?

A

90 pulse
180 pulse
90 + 180 pulse
Variable flip pulse

29
Q

Outcome of 90 pulse?

A

Rotation into transverse plane

30
Q

Outcome of 180 pulse?

A

Rotation into longitudinal plane

31
Q

Out come of 180 + 90 pulse?

A

Spin Echo sequence

32
Q

Outcome of variable flip angles?

A

Gradient echo sequence

33
Q

Characteristics of T1 relaxation?

A

Longitudinal

34
Q

Characteristics of T2 relaxation?

A

Transverse or spin-spin

35
Q

What two things does the MR signal depend on?

A

How long after RF pulse - TE

The time we repeat the pulse - TR

36
Q

What is the “measurements” of T1?

A

Short TR

37
Q

What is the “measurement” of T2?

A

Long TE

38
Q

What is the “measurement” of proton?

A

Long TR
– and –
Short TE

39
Q

What is the tissue of T1?

A

Fat

40
Q

What is the tissue of T2?

A

Water (CSF)

41
Q

What is T1- weighted good for seeing?

A

Anatomical detail

42
Q

What is T2-weight food for seeing?

A

tissue oedema

Radiology (21 decks)

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