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MRI ARMRIT > ARMRIT > Flashcards

ARMRIT Flashcards

1
Q

Which parameter in a pulse sequence helps prevent “crosstalk” between two adjacent images

A

Slive Interval

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2
Q

When selecting only one slice at a time during a pulse sequence, which method for providing spatial localization is employed?

A

2DFT

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3
Q

In spatial localization, which factor most affects slice thickness and position?

A

Bandwidth and strength of the G’s

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4
Q

Determine Scan Time
TR 550 ms
NEX 4
Matrix 256 x 192

A

7 minutes

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5
Q

Which is a normally enhancing structure after the administration of gadolinium

A

Choroid plexus

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6
Q

Inverstion time, in an Inversion pulse sequence, is the time interval between the:

A

180 and 90 degree pulses

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7
Q

Decreasing slice thickness will

A

Decrease SNR

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8
Q

A gradient is employed exposing the patients body to a series of increasing or decreasing magnetic field strengths for slice selection, in what relation to the slice is this gradient?

A

Perpendicular

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9
Q

What year was the first MRI enhancement agent approved for clinical use?

A

1988

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10
Q

In a pulse sequence employing 2DFT, the time can be calclulated using which formula

A

TRxNEXxMatrixw

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10
Q

In an Inversion recovery pulse sequence, what TI will produce a STIR fat suppressed pulse sequence?

A

80 - 120

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11
Q

Residual, undesirable gradient magnetic fields that persist for a variable time duration after the pulse of electricity from the gradient power supply is terminated are known as

A

Eddy Currents

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12
Q

Tissues that have low (short) relaxation times

A

Have higher relaxation rates

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13
Q

The two types of enhancement media described by Lauffer, the mechanisms of T1 agents is:

A

To decrease T1 relaxation time, thus emitting high signal

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14
Q

which parameters describe a PD image

A

Long TR
Short TE

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15
Q

Scan time
TR 2000
NEX 1
Matrix 256x128

A

4 Minutes

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16
Q

Combining a metal lon with a ligand reduces their tendency to bind to proteins, enzymes, or membranes. The degree to which they disassociate is a measure of their

A

Toxicity

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17
Q

In a horizontal Field magnet what is the primary G’s for a sagittal slice

A

Gx

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18
Q

when matrix goes up

A

the pixel goes down

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19
Q

In spatial localization, the “logical” slice selection gradient is symbolized

A

Gz

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20
Q

Information acquired when you increase or decrease the frequency of the RF pulse of the G’s, causing the center of the excited plane to change with the center of the G’s RF pulse is

A

Slice Position

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21
Q

Decreasing the NEX

A

Decrease SNR and Resolution

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22
Q

In a horizontal field magnet, what is the primary Gs for a Coronal slice

A

Gy

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23
Q

In General, parameters for a T1 and T2 weighted images are as follows:

A

T1
TR 100-1000 ms
TE 20-30 ms

T2
TR 1600-3000 ms
TE 70-100 ms

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24
Q

When selecting a volume of slices, which method for providing spatial encoding is employed

A

3DFT

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25
Q

Who described the mathematical method for converting a time-varying signal into it’s frequency components, which are used to obtain positional information from the MR signal

A

Jean Baptiste Joseph Fourier

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26
Q

Decreasing matrix does what to pixel

A

Increases pixel

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27
Q

The maximum exposure to the head and trunk from the main magnetic field (B0) is:

A

3T

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28
Q

Patients with a pacemaker are contraindicated for an MRI scan in MR magnets with field strength of:

A

Any Strength

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29
Q

Maximum exposure to the extremities from the main magnetic field (Bo) is:

A

5T

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30
Q

Hazzards associated with ferromagnetic objects such as O2 tanks are contraindicated in MR magnets with field strengths of

A

Any Strength

31
Q

Passed through a strong magnetic field; aneurysm clips, sutures, and surgical clips can experience the force of:

A

Torque

32
Q

Painful peripheral nerve stimulation can be caused by

A

GMF

33
Q

Side effects of associated with the main magnetic field (Bo) are

A

Tissue heating and cataract formation.

34
Q

Acoustic noise is experienced during an MRI study and is caused by

A

GMF

34
Q

SAR is decided by coupling what type of electromagnetic energy employed in MRI to body tissue

A

RF

34
Q

an explosive boiling off of liquid helium and/or liquid nitrogen and a sudden loss of superconductivity is known as a

A

Quench

34
Q

Guidelines which exclude pregnant individuals from exposures to MRI are mainly to protect the individual from

A

Radio Frequency

34
Q

Maximum exposure to RF frequency averaged over the whole body is

A

no more than 0.4 w/kg

34
Q

Magnetically sensitive objects such as credit cards etc should be kept behind the ____ Gauss line

A

5

35
Q

Maximum exposure to RF in one gram of tissue is

A

a maximum spatial peak of 8 w/kg

36
Q

Side effects associated with gradient magnetic fields are

A

cardiac fibrillation, magnetophosphenes

37
Q

the factor which determines the calculated SAR average is

A

the patients weight in kilograms

38
Q

Conductive material in the MRI environment can be affected by electrical currents from

A

GMF and/or RF

39
Q

the safety rate index for MRI Gadollinium enhancement agent is

A

50

40
Q

the effects of main magnetic field inhomogeneites on the FID signal are corrected for in a spin-echo sequence by applying a second RF pulse. The flip angle of this RF pulse is

A

180 degrees

41
Q

an equation dervied to predict the MR signal intensity of a particular tissue as the result of a spin-echo pulse sequence is the

A

Bloch equation

42
Q

a 90 degree RF pulse will alter the NMV, a secondary effect is

A

the hydrogen protons will have phase coherence.

43
Q

the main magnetic field of MRI systems in clinical use must meet an acceptable specification of

A

20-30 PPM

44
Q

what type of electromagnetic coils correct inhomogeneites in the main magnetic field

A

shim coils

45
Q

the larmor frequency of hydrogen protons in a 1.5 Tesla magnetic field is

A

63.9MHz/Tesla

45
Q

T1 process is also known as

A

Spin Lattice

46
Q

the purpose of a magnetic resonance angiography is to image the

A

Blood flow

47
Q

Which type of MRI magnet requires a steady current of electricity in coils of conductor wrapped around an air or iron core?

A

resistive

48
Q

Magnetic susceptibility is defined as

A

tendency of a substance to attract or repel magnetic lines of force which is decided by the magnetic properties of its electrons

49
Q

in comparison to CT a disadvantage of MRI is that

A

special and costly site planning and shielding

50
Q

Fast transition phenomenon and entry phenomenon are theories that explain which of the following tissue characteristics

A

Velocity effects

51
Q

which type of electromagnetic coils can be found both inside and outside of the housing of the MRI magnet

A

RF coils

52
Q

In the USA, MRI systems in clinical use have main magnetic field strengths that range from

A

0.06 to 3 Tesla

53
Q

which type of receiver radio frequency coil is placed close to a patients body for the purpose of imaging superficial anatomic strucures

A

surface coils

54
Q

at any one time, human body tissue is made up primarily
50-90% of what tissue

A

H2O

55
Q

On a PD image two types of tissue that that contain very low concentrations of hydrogen and appear very hypointense are

A

cortical bone and lung

56
Q

the introduction of Gado based contrast enhancement agents by IV injection can involve passing through an abnormal BBB, the tissue compartments involved are

A

intravascular to interstitial space

57
Q

Once the NMV has moved away from equillibrium, the following will occur

A

the transverse component will increase

58
Q

The transmit radio frequency coil generates a second electromagnetic field to the hydrogen protons. this field is designated

A

B1

59
Q

which type of electromagnetic coils produce smaller magnetic field which allow spatial localization to be performed.

A

gradient coils

60
Q

the tissue characteristic that depends heavily on the relative content of fat molecules and free water is

A

T1 effects

61
Q

T2 process is also known as

A

Spin Spin

62
Q

which type of MRI magnet requires a special cooling system to dissipate heat produced by very large currents?

A

resistive

63
Q

In MR imaging for a chemical substance to be affected by the main magnetic field and the radio wave it must contain an

A

odd number of total protons and neutrons

64
Q

Magnetism can be defined as the ability of certain substances to attract

A

iron cobalt nicke

65
Q

a sinewave is a symbol used to measure electromagnetic energy. A sinewaves two components of measurements are

A

Wavelength and frequency

66
Q

The component Mz is most associated with

A

Parallel to Bo, T1 relaxation, longitudinal magnetization

67
Q

of the following RF flip angles which is the smallest that will produce the maximum signal.

A

90 degrees

68
Q

to describe the uniformity of the MRI systems main magnetic field, the term employed is

A

Homogeneity.

MRI ARMRIT (3 decks)

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