LEC 2 - MRI + CT Scans Flashcards

1
Q

What is the downside to radiography?

A

Not functional
Not cross sectional
Poor soft tissue appearance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the downside to ultrasound?

A

Not functional

Bad at seeing bone and lung

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the four options for advanced imaging?

A

Nuclear imaging
Computed Tomography
Magnetic Resonance Imaging
Contrast Ultrasound

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is nuclear imaging used for?

A

Bone scans

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

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

A

Rotating photon source
Rotating detectors
Computer constructs image

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What do CT’s measure?

A

Attenuation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is attenuation coefficient?

A

Degree to which x-ray intensity is reduced by material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How is the measurement called for CT?

A

Hounsefielf (HU)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is HU’s based on?

A

Water = 0

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the progression of HU units?

A
Bone = + 
Water = 0 
Air = -
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

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

A

Gray

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

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

A

Thorax - Lung mass

GOLD STANDARD

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the limitations to a cone beam CT?

A

only images in the transverse plane

VERYYYYYY SLOW

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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?

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
What direction of magnetization can NOT be measured?
Longitudinal
26
What is another name for the wobbling of the protons?
Precession
27
What is RF pulse?
Radiofrequency pulse | caused by the rapid changing of magnetic and electrical fields
28
What are the types of RF pulses?
90 pulse 180 pulse 90 + 180 pulse Variable flip pulse
29
Outcome of 90 pulse?
Rotation into transverse plane
30
Outcome of 180 pulse?
Rotation into longitudinal plane
31
Out come of 180 + 90 pulse?
Spin Echo sequence
32
Outcome of variable flip angles?
Gradient echo sequence
33
Characteristics of T1 relaxation?
Longitudinal
34
Characteristics of T2 relaxation?
Transverse or spin-spin
35
What two things does the MR signal depend on?
How long after RF pulse - TE | The time we repeat the pulse - TR
36
What is the "measurements" of T1?
Short TR
37
What is the "measurement" of T2?
Long TE
38
What is the "measurement" of proton?
Long TR -- and -- Short TE
39
What is the tissue of T1?
Fat
40
What is the tissue of T2?
Water (CSF)
41
What is T1- weighted good for seeing?
Anatomical detail
42
What is T2-weight food for seeing?
tissue oedema