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Diagnostic Methods > MRI Imaging for the PA > Flashcards

MRI Imaging for the PA Flashcards

1
Q

What does an MRI use to create its image?

A

molecular composition of tissues and a strong magnetic field to manipulate electrical activity of HYDROGEN atoms in the body

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2
Q

When a patient enters an MRI machine, what direction does the protons current flow?

A

protons current will line up parallel to the main superconducting magnet of the MRI

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3
Q

What are the coils of the magnet in the MRI responsible for?

A

Transmitting RF pulses

Receiving the signal or echo

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4
Q

What happens when the RF pulse is transmitted by the transmitter coil?

A

protons are displaced from their original alignment

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5
Q

Why is the superconduction magnet kept really cold?

A

to reduce the heat from the friction of the protons

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6
Q

What do transmitter coils send?

A

a short magnetic pulse = RF pulse

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7
Q

What happens when the RF pulse is turned off?

A

the protons realign in a parallel state to magnet and energy in the form of RF signals are released

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8
Q

When the protons realign in a parallel state to the magnet after the RF pulse is turned off, what is this called?

A

recovery

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9
Q

What is T1 relaxation?

A

Recovery; time it takes for the tissue to recover to parallel state

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10
Q

What is the length of time for recovery and the echo called?

A

T1 and T2

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11
Q

What is TE?

A

echo time

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12
Q

What is TR?

A

repetition time

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13
Q

What weighting does T1 have?

A

short TE of 10-20 s

short TR of 300-700 ms

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14
Q

What appears white in T1 image?

A

Fat
Gadolinium
Proteinaceous Fluid
Melanin

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15
Q

What is T2 relaxation?

A

Decay; time it takes for tissue to return to perpendicular to magnetic field

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16
Q

What weighting does T2 have?

A

Short TE of 20 ms

LONG TR of 2000ms

17
Q

What is the mnemonic to for T2?

A

WWII - water white in 2

18
Q

What typically appears white in T2?

A 
water
fat
edema
inflammation
infection
cyst
hemorrhage
19
Q

What vascular structures are enhanced with Gadolinium?

A

Tumors

Areas of inflammation

20
Q

What is the effect of Gadolinium?

A

shorten the T1 relaxation time of hydrogen nuclei to create a brighter signal

21
Q

How is Gadolinium excreted?

A

by the kidney

22
Q

What are some advantages of MRIs?

A

capable of high-resolution images in multiple planes

can provide detailed soft tissue characteristics

non-invasive

No known harmful effects

23
Q

What are some disadvantages of MRIs?

A

More expensive than xray or CT

Long scan time (30-45 min.)

Limited by multiple things

24
Q

What limits the use of an MRI?

A 
patients body habitus
patient anxiety or pain
ferrous implants
Implanted pumps/electronic devices
contrast issues (allergy)
25
Q

What is the magnetic field strength of most MRIs?

A

0.5 to 3 Tesla

26
Q

What is Earth’s magnetic field strength?

A

50 microT

27
Q

Which type of MRI machine gives a better quality image?

A

closed

28
Q

What is the magnetic field strength of open MRI machines?

A

0.1 to 1 T

29
Q

What procedures require the patient to be placed head first in to machine?

A 
Head and Neck
Chest
Cervical Thoracic and Whole Spine
Abdomen
Shoulders and Upper Limb
30
Q

What procedures require the patient to be placed feet first in to machine?

A

Pelvis
Hips
Lower Limbs

31
Q

What are CT scans used for?

A

trauma to identify and characterize injury patterns and severity

32
Q

What is CT better than xray for diagnosing?

A

identifies subtle fractures

Visualizes articular extension of fracture

Assesses for the presence of articular step-off/gap

33
Q

What is MRI most used for?

A

PRIMARILY EVALUATION OF SOFT TISSUE

diagnosing occult fractures

concern for associated ligament or articular cartilage injury

34
Q

What is MRI the modality of choice for?

A

Disc Herniation

To assess “internal derangement” of joints

35
Q

What type of MRI images are occult fractures best visualized on?

A

T2 images in which the light up as edema of bone marrow

36
Q

Where do bone bruises appear on an MRI image?

A

In T2 weighted images as hyperintense signal

37
Q

What is an MRI standard for assessing of the spine?

A

spinal cord anatomy, tumors, or trauma

PreOp eval. of pts. with spondylosis or disk herniation = MOC

38
Q

What does Gadolinium help with when used in MRI?

A

differentiates tissues receiving higher blood flow; infection, tumor, postsurgical scar

Diagnostic Methods (27 decks)

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