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Possible board questions from lansing meet > Lansing-Board questions? > Flashcards

Lansing-Board questions? Flashcards

1
Q

The higher strength the magnet, the better___ which means more ____

A

Signal, NMV’s

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2
Q

Put in basic physics terms, what is the magnetic field created by within the hydrogen atom?

A

Motion from the protons (A moving charge produces a magnetic field according to Faraday’s Law)

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3
Q

What is the Larmor equation used to determine?

A

The precessional frequency

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4
Q

What is another way of saying B0 when referring to the magnetic field strength?

A

B sub 0

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5
Q

What are unique characteristics of a conventional gradient sequence?

A
  • smaller FA

- Short TR

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6
Q

Just after an excitation pulse that flips the NMV into the transverse plane, the magnetic moments are all____?

A

In phase

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7
Q

Which will de-phase spins much faster? 1.5T or 3T

A

3T because the precessional frequency is much faster at higher field strengths.

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8
Q

Terminology: What is the official term for the initial 90 degree pulse in a SE sequence?

A

excitation pulse

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9
Q

Terminology: What is the official term for the 180 degree pulse in a SE sequence?

A

refocusing pulse

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10
Q

If an ETL of 6 is used, how many lines of k-space are filled per TR?

A

6

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11
Q

What is the scan time formula for a FSE sequence?

A

TR x Phase x NEX/etl

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12
Q

What is the scan time formula for regular SE sequence?

A

TR x Phase x NEX

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13
Q

What two phenomenons occur when an RF pulse is removed in MRI?

A
  • T1 recovery

- T2 decay

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14
Q

For a T2 sequence, which of the three describes the length of TR and TE?

  • short
  • medium
  • long
A
  • long TR

- long TE

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15
Q

For a T1 sequence, which of the three describes the length of TR and TE?

  • short
  • medium
  • long
A
  • short TR

- short TE

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16
Q

Why are FSE sequences good for imaging any metal?

A

Multiple 180 degree pulses constantly rephase

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17
Q

As SAR increase, what else increases?

A

tissue heating

18
Q

What does a tailored RF pulse do in a FSE sequence?

A

Applies echo train pulses in decreasing magnitudes.
For example, begins with 180 pulse, then 170 pulse, then 160 pulse.
Functions to decrease blurring in FSE brought about from repeated 180 degree pulses

19
Q

As the ETL increase, what also increases and why?

A
  • Blurring
  • because the more information applied to k-space per TR means more information that has to be averaged to produce the image.
20
Q

Does fat have a short or long T1 time?

A

short

21
Q

Does fat have a short or long T2 time?

A

short

22
Q

Does water have short or long T1 time?

A

long

23
Q

Does water have a short or long T2 time?

A

long

24
Q

What does TR mainly control?

A

T1 weighting

25
Q

what does TE mainly control?

A

T2 weighting

26
Q

For a PD sequence, which of the three describes the length of TR and TE?

  • short
  • medium
  • long
A

-TR long
-Short TE
(many questions on the board about PD)

27
Q

being that gradient sequences don’t use a refocuing pulse, what do they use to re-phase spins once they are in the T-plane?

A

the linear change in magnetic field strength across an imaging volume created by gradients

28
Q

what blood vessel is responsible for supplying 75% of the liver’s blood supply?

A

hepatic portal vein

29
Q

what does the slice select gradient determine in a pulse sequence?

A
  • what slice

- what plane

30
Q

the phase encoding gradient affects what axis of the anatomy in k-space?

  • long
  • short
A

short

31
Q

the frequency encoding axis affects what axis of the anatomy in k-space?

  • long
  • short
A

long

32
Q

what factor applies directly to the frequency encoding gradient?

A

receive bandwidth

33
Q

In a given TR period, are all three gradients used?

T or F

A

True

34
Q

why isn’t frequency encoding direction a part of the time formula?

A

the frequency encoding direction selects data point and samples
The phase encoding direction directly affects how many lines in k-space are filled

35
Q

what does the center of k-space contribute?

A

90% of SNR

36
Q

what do the outer edges of k-space contribute?

A

resolution

37
Q

what is one of the biggest safety considerations on a 3T magnet?

A

SAR

38
Q

Why is it so important to sample BW at a higher level instead of cutting it down?

A

When a wider bandwidth is received, the peak of the signal is collected (contributing to k-space center) and the outer noise as well (contributing to resolution)

39
Q

why are EPI/DWI sequences so loud?

A

Due to the k-space filling method used of rapidly switching from positive to negative values along each line of k-space

40
Q

why do EPI/DWI sequences have such a low matrix?

A

to drastically reduce number of lines filled in k-space and freeze motion.

Possible board questions from lansing meet (1 decks)

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