MRI Flashcards

1
Q

what is a scout film

A

displays an image of the studied body region on which is superimposed a sequentially numbered parallel lines or “slices” example IM 3/38

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2
Q

What do the abbreviations THK and FOV stand for

A

THK- thickness of the slices

FOV - field of view (3x3 cm, 4x4cm etc)

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3
Q

how can the sequence number help you sort through the different types of imaging studies (T1, T2, etc)

A

Often times one type of image is given the even numbers while its corresponding image is given even numbers (T1s even T2s odd so you can compare the same image with different weighting side by side)

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4
Q

Describe the image orientation of axial, sagittal plane, and frontal plane images

A

axial- you are looking up fro the patients feel
sagittal -
coronal - patient facing toward the viewer

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5
Q

what does the MRI measure

A

contrast between tissues based on relative relaxation times of hydrogen protons after radio frequency perturbation from their relaxed precessional axis
T1 (Brief RF) and T2 are the different types of perturbation

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6
Q

What tissues do T1 images emphasize?

A

T1 (Brief RF) - tissues with protons that quickly recover and yield a short RF recording time (shot TE and TR time)

  • fat emphasis due to the faster proton recovery relative to muscle
  • fat is bright white due to higher single intensity
  • bone cortex is dark
  • good for anatomy not pathology
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7
Q

What tissues do the T2 images emphasize

A

T2 (longer duration RF) - tissues that recover more slowly are emphasized (long TE and TR)

  • muscle is emphasized on these images as bright white
  • fat is gray
  • better than T2 for viewing pathology
  • cortex dark
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8
Q

what image type will bone, fibrotic and inflamed tissues show up on best?

A
  1. fibrotic - less water and tend to have longer recovery times therefore are best visualized on T2
  2. inflammatory - increased water content creating longer recovery times and better visualization on T2 images
  3. bone will have low signal intensity in T1
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9
Q

what is magic angle phenomenon

A

image artifact created by misleading changes in signal intensity associated with collagen based tissues orientation. signals can cancel or amplify

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10
Q

How are MRI findings described (what is the nomenclature)

A

Relative signal intensity (normal, increased, decreased, etc)

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11
Q

How are T1 and T2 images different

A

T1 weighted - fat is white, water is gray, marrow is bright, cortex is dark, good for anatomy
T2 weighted - fat is gray, water is white, marrow is gray, cortex is dark, good for pathology because lesion are usually water based

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12
Q

Hydrogen is most present in what type of tissues

A

water based tissues

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13
Q

What structure is the MRI actually measuring

A

it is imaging protons

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14
Q

what is precess

A

the tendency of protons in the presence of a magnetic field to spine around an axis

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15
Q

the loud noise of the MRI is the magnetic field pulse. what does this accomplish for the MRI image

A
  1. organized alignment of the axis of proton spin/precess

2. gradient of frequencies decreasing with distance from the magnetic coils

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16
Q

what is flip angle and what is its value in the MRI

A

angle to which a proton will shift its spin axis when perturbed by the MRI
- the time it takes for the proton to return to its normal angle is measured via a RF signal released by the proton as its normal angle is restored

17
Q

what do T1 and T2 images measures

A

Both are measures simultaneously, but pick up different parts of the signal

  • T1 measures the longitudinal vector of the RF signal
  • T2 measures the transverse vector of the signal
18
Q

What advantages does MRI have over radiating images such as CT and X-ray

A
  • multiple plane image angles
  • good contrast with water dense tissue
  • no know health hazards
  • good for soft tissue imaging
  • good for neurology
19
Q

What disadvantages does MRI have over radiating images such as CT and X-ray

A
  • more expensive
  • trouble with claustrophobia and motion artifact
  • limited availability
  • bone trauma poorly demonstrated
20
Q

what are the three basic acquisition techniques for MRI

A
  1. PD (spin) - proton density
  2. T1
  3. T2
21
Q

what does the PD image emphasize

A
  • high signal intensity with water based tissues (synovial fluid and effusion)
  • low signal intensity with bone or air filled spaces
  • good for orthopedic trauma
  • long TR (repetition of pulse) and short TE (peak echo time)
22
Q

What tissue you can help you differentiate T1 from T2

A

Look at the fat (world war II - water is white on T2)

  • T1 fat is bright white and water is gray
  • T2 Fat is gray and water is bright white
23
Q

What color will water appear in CT, T1 and T2 images

A

CT/x-ray - gray
T1 - dark
t2 - bright

24
Q

What color will air appear in CT, T1 and T2 images

A

CT/x-ray - black
T1 - dark
t2 - dark

25
Q

What color will fat appear in CT, T1 and T2 images

A

CT/x-ray - black
T1 - white
t2 - gray

26
Q

What color will bone cortex appear in CT, T1 and T2 images

A

CT/x-ray - white
T1 - gray-black
t2 - dark gray

27
Q

What color will bone cortex appear in CT, T1 and T2 images

A

CT/x-ray - gray
T1 - bright
t2 - gray

28
Q

hybrid MRI sequence translation tips

A
  • Look to the relative T1 and T2 weighting

- “look to the fat” for signal intensity to help identify signal type

29
Q

What are some examples of MRI enhancement techniques

A

FSE
FS
GAD
STIR

30
Q

What is a bankart fracture

A

avulsion of the superior glenoid

31
Q

What is a bouchard nodes

A

the large boney out growths of the joint

- hallmark of OA

32
Q

What is the FBI sign

A

Fat, Blood, intra-articular
- escape of fat and blood from the bone marrow space into the int capsule
AKA - lipohaemarthrosis