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RA6007 > MRI > Flashcards

MRI Flashcards

1
Q

MRI scanners in clinical use have field strengths between 0.2T and 3.0T, with 1.5T being the most common

A

T

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2
Q

Magnetic field homogeneity refers to the uniformity of the magnetic field throughout the magnet.

A

T

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3
Q

Superconducting magnets operate at room temperature

A

F (They are cooled using liquid helium and surrounded by liquid nitrogen for thermal insulation.)

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4
Q

Superconducting magnets consume large amounts of liquid helium in modern scanners

A

F (Modern scanners are designed to consume little liquid helium, making them more efficient.)

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5
Q

The long narrow bore of superconducting magnets improves magnetic homogeneity

A

T

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6
Q

Permanent MRI magnets are used widely in clinical practice

A

F

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7
Q

Resistive MRI magnets require large amounts of electricity to generate a high magnetic field.

A

F. (Resistive magnets consume large amounts of electricity but produce only low-strength magnetic fields)

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8
Q

The RF system transmits RF energy at the Larmor frequency and detects echoes emitted by the patient.

A

T

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9
Q

As the field strength increases, the requirement for RF power decreases.

A

F. (RF power requirements increase with higher field strengths)

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10
Q

Receive coils can be separate from transmit coils in MRI systems

A

T

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11
Q

The amplitude of the echo detected by the RF coil does not require amplification

A

F. (Echo signals are very small and must be amplified before processing)

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12
Q

The gradient system alters the magnetic field to provide spatial information about the patient

A

T

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13
Q

Gradient coils alter the main
𝐵0 magnetic field strength.

A

T

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14
Q

The loud noise in an MRI scanner is caused by the switching on and off of gradient coils.

A

T

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15
Q

In the absence of an external magnetic field, hydrogen protons are randomly oriented

A

T

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16
Q

Hydrogen protons align parallel or antiparallel to 𝐵0, creating equal energy levels.

A

F. (Protons align in two different energy states)

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17
Q

The Larmor frequency is the resonant frequency of the tissue at a given magnetic field strength.

A

T

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18
Q

The Larmor equation determines the frequency at which protons resonate

A

T

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19
Q

T1 relaxation involves the transfer of energy to surrounding tissues (the lattice).

A

T

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20
Q

Water has long T1 relaxation times

A

T

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21
Q

Water has long T1 relaxation times and appears white on T1-weighted images

A

F. (Water has long T1 times but appears black on T1-weighted images)

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22
Q

T2 relaxation involves the loss of phase coherence

A

T

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23
Q

T2 relaxation always involves energy transfer

A

F. (T2 weighting may or may not involve energy transfer)

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24
Q

T1 relaxation always involves energy transfer

A

T

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25
Q

T1 relaxation times are dependent on B0

A

True

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26
Q

T1 relaxation times are independent of B0

A

F. (T1 relaxation times are dependent on B0)

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27
Q

In a Spin Echo sequence, T1 weighting requires a short repetition time (Tr) and echo time (Te)

A

T

28
Q

Inversion Recovery sequences start with a 90-degree pulse followed by a 180-degree pulse.

A

F. (They start with a 180-degree pulse, followed by a 90-degree pulse.)

29
Q

STIR is a fat suppression sequence, and FLAIR is a CSF suppression sequence.

A

T

30
Q

Gradient Echo sequences produce low signal-to-noise ratio (SNR) images.

A

T

31
Q

GE sequences are faster and have improved SNR compare to SE sequences

A

F. (GE sequences are faster but have reduced SNR compared to Spin Echo sequences)

32
Q

Image acquisition time is proportional to the number of frequency encoding steps.

A

F. (It is proportional to the number of phase encoding steps)

33
Q

Wrap-around artefact can be mitigated by increasing the field of view (FOV).

A

T

34
Q

The projectile effect depends on the rate of change of the magnetic field

A

T

35
Q

Cryogens used in MRI systems can pose hazards such as frostbite or asphyxiation

A

T

36
Q

AR measures the RF power absorbed per kilogram of tissue during an MRI scan

A

T

37
Q

Superconducting magnets are the most commonly used type in clinical MRI.

A

T

38
Q

Superconducting magnets have poor homogeneity

A

F. (They have excellent homogeneity)

39
Q

Permanent magnets are very stable and unaffected by external disruptions

A

F. (Permanent magnets are sensitive to external disturbances and temperature changes, which can destabilize the magnetic field.)

40
Q

Resistive magnets are energy-efficient and produce high field strengths.

A

F. (Resistive magnets consume large amounts of electricity and produce low field strengths.)

41
Q

Superconducting magnets are always on, regardless of whether a scan is in progress.

A

T

42
Q

The strength of 𝐵0 is unaffected by gradient coils

A

F

43
Q

The loud noise during MRI scans is caused by RF coil vibrations

A

F. (It is caused by the rapid switching of gradient coils.)

44
Q

The spatial resolution of an image depends on the central lines of k-space

A

F. (Spatial resolution is determined by the peripheral lines of k-space, while contrast is influenced by the central lines)

45
Q

Slice Thickness depends on the RF pulse bandwidth and the amplitude of the slice selection gradient

A

T

46
Q

A narrower RF bandwidth and lower gradient amplitude produce thicker slices.

A

F. (A narrower RF bandwidth and lower gradient amplitude produce thinner slices.)

47
Q

Energy transfer in T1 relaxation occurs via dipole-dipole interactions

A

T

48
Q

In T1-weighted images, fat appears bright and water appears dark.

A

T

49
Q

T1 is typically shorter than T2 for liquids

A

F. (T1 and T2 are similar for liquids)

50
Q

Gradient Echo (GE) sequences are faster than Spin Echo sequences but have lower SNR.

A

T

51
Q

The echo is the signal emitted by rephased spins and contains image information

A

T

52
Q

FID is used to form images

A

F. (FID does not contain image information and is ignored)

53
Q

The Fourier Transform is used to extract frequency and spatial information from MR signals.

A

T

54
Q

Frequency encoding is applied along the Y-axis, while phase encoding is applied along the X-axis.

A

F. (Frequency encoding is along the X-axis, and phase encoding is along the Y-axis.)

55
Q

The number of phase encoding steps determines the image acquisition time

A

T

56
Q

The projectile effect depends only on the strength of the magnetic field

A

F. (It also depends on the rate of change of the field and the properties of ferromagnetic materials)

57
Q

Chemical shift artefacts of the first kind can occur in both Spin Echo and Gradient Echo sequences.

A

T

58
Q

Superconductive magnets are attractive as they offer little to no resistance

A

T

59
Q

B0 is altered by gradient coils

A

T

60
Q

Anti-parallel protons are of lower energy than parallel ‘with field’ protons

A

F. (Antiparallel ‘against field’ protons have higher energy)

61
Q

T2 relaxation time is known as longitudinal relaxation time

A

F. (T1 Spin-Lattice relaxation time is known as longitudinal relaxation time)

62
Q

Contrast shows up better on a T1 weighted image

A

T

63
Q

Technetium is the most common contrast agent used in MRI

A

F. (Gadolinium)

64
Q

The rate limiting factor to produce an image is the number of phase encoding steps

A

T

65
Q
A

RA6007 (5 decks)

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