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MRI > Sequence Parameters and Options > Flashcards

Sequence Parameters and Options Flashcards

1
Q

What is the most common data acquisition option in which a single line of K space is filled by data acquired from each slice before the TR period is repeated?

A

2D Imaging

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2
Q

What is a type of data acquisitioning option in which all data is acquired as volume with no space gap?

A

3D imaging

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3
Q

During 3D imaging, slice encoding occurs when?

A

Post data acquisiton

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4
Q

When data is acquired from each slice consecutively, one after the other is?

A

Sequential Slice Order

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5
Q

How much gap is needed to prevent image artifacts when acquiring slices sequentially?

A

at least 30% gap

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6
Q

When data is acquired from alternate slices through two separate acquisitions.

A

Interleaving slice order

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7
Q

What is typically not need to prevent image artifacts when using slice interleaving option?

A

Slice Gap
–Because Slice Interleaving DOES NOT acquire sequentially–

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8
Q

Spatial Saturation - (?)

A

Image option where a 90 degree RF pulse prior to the initial pulse in order to null the signal from user-specified AREAS OF UNWANTED ANATOMY.

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9
Q

Using an extra 90-degree RF pulse and _____, spatial saturation is able to saturate all other tissues in a specified area.

A

Broad Transmisson Bandwidth

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10
Q

The use of spatial saturation pulses will affect what 3 things?

A

Tissue Heating
SAR levels
Max # of slices available per acquisition

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11
Q

Gradient Moment Nulling (GMN) is..

A

Imaging option whose primary purpose is to compensate for flow within the image volume.

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12
Q

What type of flow is GMN most efficient at rephasing?

A

Laminar Flow (1st order flow)

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13
Q

When GMN is applied to axial images, which gradient is used for flow compensation?

A

Slice-Select Gradient

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14
Q

On Sagittal and Coronal images, which gradient is used when using GMN?

A

Frequency Encoding

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15
Q

What 3 things are true when using GMN?

A

It’s most effective using slow laminar flow.
It reduces intra-voxel dephasing.
It used the slice-select gradient or frequency encoding gradient to rephase flowing spins.

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16
Q

Which imaging option applies a 90 degree RF pulse prior to the initial pulse in order to null the signal from a specified tissue THROUGHOUT THE ENTIRE IMAGE VOLUME?

A

Chemical Supression.

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17
Q

Chemical Sat. pulse is capable of saturating tissues throughout the entire volume using an initial RF pulse of 90 degrees and what?

A

Narrow Transmission Bandwidth

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18
Q

A ___ is used to improve magnetic field homogeneity when using chemical suppression techniques.

A

Shim

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19
Q

When using chemical suppression, magnetic field homogeneity is crucial for ensuring that targeted hydrogen protons are precessing at ____________________

A

MATCHING the frequency created by the chemical saturation pulse.

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20
Q

What determines the time period between the 90 degree saturation pulse and the alpha pulse when applying the chemical sat. technique?

A

Sat TR

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21
Q

What equation is used to calculate the Sat TR needed when using chemical suppression?

A

TR / # of slices

22
Q

Sat TR is usually represented by?

A

ms (milliseconds)

23
Q

An imaging option used to track physiological motion so that the data acquisition can be properly timed for minimization of motion.

A

Physiological Gating/Triggering

24
Q

The P wave of the cardiac cycle represents what?

A

Atrial Systole

25
Q

The QRS wave of the cardiac cycle represents what?

A

Ventricular Systole

26
Q

The T wave of the cardiac cycle represents what?

A

Ventricular Diastole

27
Q

During MRI an increase of the amplitude of the T wave is commonly caused by -

A

Both magneto-HEMOdynamic and magneto-HYDROdynamic effects.

28
Q

Which component of the QRS phase is of utmost importance?

A

R phase

29
Q

The R phase represents what?

A

The PEAK of the QRS complex as well as the PEAK of ventricular contraction.

30
Q

What is the time period between consecutive R phases known as?

A

R to R interval

31
Q

The R to R interval during MRI is dependent on the patients what?

A

Heart Rate

32
Q

When applying cardiac gating, what influences the TR?

A

Pt. Heart Rate
R to R interval
Desired Image Weighting

33
Q

What is the equation to determine the length of one R to R interval?

A

60,000ms / BPM

34
Q

The time period between R phases of the R to R interval is represented by what?

A

TR

35
Q

R to R interval is measured in?

A

milliseconds (ms)

36
Q

As a patient’s heart rate increase, the R to R interval ______

A

Shortens

37
Q

If a pt. has a considerable high heart rate and only one R to R interval can be selected, a short TR CANNOT be used. (T/F)

A

False

38
Q

During cardiac imaging, the period when the system stops acquiring data in order to detect the next R phase is called what?

A

Trigger Window (shown as a %)

39
Q

The Trigger Window is used to help compensate for the fluctuations in pts. what?

A

Heart Rate

40
Q

A trigger window of what percent is commonly used to compensate for heart rate fluctuations.

A

10-20%

41
Q

The waiting period following each R phase is

A

Trigger Delay

42
Q

A trigger delay of what (ms) is common in modern MR systems?

A

5-10ms

43
Q

Extending the trigger delay is a technique sometimes used to image the heart during

A

Diastole

44
Q

A form of physiological gating/triggering commonly used to prevent motion artifact from occurring due to blood flow within the extremities and CSF flow within the brain and spine.

A

Peripheral gating/triggering

45
Q

During peripheral Gaiting/Triggering, motion is tracked using what device?

A

Pulse Ox

46
Q

A respiratory bellow is a device that converts the ____ from breathing motion into a ___ that the MRI system can detect.

A

Mechanical Energy - Electrical Signal

47
Q

a respiratory bellow uses a________________ to convert mechanical energy from breathing motion to electrical signal.

A

Transducer

48
Q

A respiratory navigator echo tracks respiratory motion by monitoring ___ from within its prescribed ROI.

A

Signal Intensity

49
Q

In phase imaging is achieved by selecting TE values in multiples of -

A

4.2ms

50
Q

Using a rectangular FOV is an option that uses a -

A

Phase FOV SMALLER THAN the Frequency FOV.

51
Q

The imaging option that increases the number of phase-encodings performed in the phase direction is?

A

Anti-Aliasing (over-sampling, no phase wrap, anti-fold over)

MRI (3 decks)

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