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Physics Flashcards

1
Q

What is letter A?

A

Magnetic field strength

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2
Q

What is letter B?

A

Gyromagnetic ratio

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3
Q

10,000 Gauss= ❓Tesla

A

1

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4
Q

Iron & Iron-like substances that can generate a relatively strong magnetic field are?

A

Ferromagnetic

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5
Q

Substances with a very weak magnetic field are?

A

Paramagnetic

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6
Q

Substances that have no magnetic field are?

A

Diamagnetic

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7
Q

Hydrogen protons in the anti-parallel state are referred to as….?

A

Spin down and/or high energy spins

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8
Q

T1 relaxation is also known as…?

A

Spin lattice relaxtion

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9
Q

Pixel Area x Slice Thickness= ?

A

Voxel volume 3

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10
Q

Phase pix size X Freq. pixel size= ?

A

Pixel Area2

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11
Q

FOV/Matrix=?

A

Pixel Size

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12
Q

TR x Phase Matrix x NEX x #Slices= ?

A

3D gradient echo scan time

Divide by 1,000 to convert to seconds

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13
Q

TR x Phase Matrix x NEX / ETL = ?

A

FSE scan time

Divide by 1,000 to convert to seconds

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14
Q

TR x Phase Matrix x NEX= ?

A

Spin Echo scan time

Divide by 1,000 to convert to ms to seconds

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15
Q

FOV/Phase Matrix= ?

A

Pixe size dimensions
(Phase encoding direction)

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16
Q

FOV/Freq. Matrix= ?

A

Pixe size dimensions
(Freq. encoding direction)

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17
Q

T2 weighting & contrast are controlled by ____

A

TE (Echo Time)

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18
Q

Spatially locating (encoding) signal along the short axis of the slice is known as_____

A

Phase Encoding

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19
Q

Spatially locating (encoding) signal along the long axis of the slice is know as____

A

Freq. Encoding

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20
Q

M

How do T2 contrast agents work?

A

By shortening T2 decay time

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21
Q

How do T1 contrast agents work?

A

By shortening T1 recovery time

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22
Q

Proton density is____

A

the # of mobile hydrogen protons per unit volume of a tissue

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23
Q

Parameters that can be change/under our control are called___

A

Extrinsic contrast parameters

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24
Q

List the extrinisic contrast parameters

A
  • TR
  • TE
  • TI
  • ETL
  • Flip Angle
  • b-value
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25
Q

Parameters that cannot be chaged; are inherent to body tissue are called_

A

Intrinisic contrast parameters

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26
Q

List the intrinsic contrast parameters

A
  • T1 recovery time
  • T2 decay time
  • Proton density
  • Flow
  • Apparent diffusion coefficient (ADC)
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27
Q

T1 weighting/contrast are controlled by___

A

TR

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28
Q

A range of frequencies is known as__

A

Bandwidth

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29
Q

A range of freq. transmitted in an RF excitation pluse are known as___

A

Transmit Bandwidth

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30
Q

A range of freq. that are sampled during readout are known as___

A

Receive Bandwidth

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31
Q

The center of the bore of the magnet in all planes is known as___

A

Magnetic Isocenter

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32
Q

Magnetic homogeneity is___

A

Eveness of the magnetic field

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33
Q

Nuclei that possess an odd mass # are considered___

A

MR Active nuclei

34
Q

an event in a superconducting MR system causing a loss of
superconductivity, a rapid loss of the magnet cryogens, potentially creating a hazard for patients / operators in the magnet room

34
Q

A Flair sequenc is used to…..

A

Suppress CSF/Fluid

35
Q

A STIR sequence is used to…

A

Suppress fat

36
Q

Based on this info what will your image be?
Slice selection- Z Gradient
Phase encoding- Y Gradient
Freq. encoding- X Gradient

A

Axial (body)

37
Q

Based on this info what will your image be?
Slice selection- Z Gradient
Phase encoding- X Gradient
Freq. encoding- Y Gradient

A

Axial (head)

38
Q

Based on this info what will your image be?
Slice selection- X Gradient
Phase encoding- Y Gradient
Freq. encoding- Z Gradient

39
Q

Based on this info what will your image be?
Slice selection- Y Gradient
Phase encoding- X Gradient
Freq. encoding- Z Gradient

40
Q

TR (repetition time) is…

A

the time from one RF excitation pulse to the next

41
Q

What is the Gyromagnetic ratio of hydrogen is…

42
Q

TE (echo time) is….

A

Time from RF excitation pulse to the peak signal induced in the receiver coil.

43
Q

What gradient runs from head-toe of the patient?

A

Z-Gradient

44
Q

What gradient runs from RT-LT of the patient?

A

X-Gradient

45
Q

What gradient runs from anterior-posterior of the patient?

A

Y-Gradient

46
Q

What are the trade offs of decreasing TR?

A
  • Lower SNR
  • Decrease scan time
  • Enhance T1 weighting
  • Decrease # of available slices
47
Q

What are the trade offs of increasing TR?

A
  • Improve SNR
  • Increase scan time
  • Reduce T1 weighting
  • Increase # of available slices
48
Q

On T2 weighted images how do fat and water appear?

A

Fat=Dark
Water=Bright

49
Q

On T1 weighted images how do fat and water appear?

A

Fat=Bright
Water=Dark

50
Q

What is this formula?

A

Larmor equation

51
Q

What is letter C?

A

Precessional Freq.

52
Q

The outter lines of K-space are filled with…?

A

High Resolution Date

53
Q

The central lines of K-space are filled with…?

A

Signal & Contrast Data

54
Q

K-space is…?

A

Storage location of MR signal data

55
Q

T1 relaxtion time is the time it takes for…?

A

63% of the longitudinal magnetisation to recover.

56
Q

T2 relaxtion time is the time it takes for…?

A

63% of the transverse mag. to decay
or
37% of spins to de-phase

57
Q

T1 relaxation is also knows as…

A

Spin-Lattice relaxtion

58
Q

T2 relaxtion is also known as…

A

Spin-Spin relaxation

59
Q

A scan with a short TR and short TE will have what weighting?

A

T1 weighted

60
Q

TR range for a T1 weighted image is…

60
Q

TE range for a T1 weighted image is…

61
Q

A scan with a long TR and short TE will have what weighting?

A

Proton Density (PD)

62
Q

TR range for a PD weighted image is…

A

1600-4000ms

63
Q

TE range for a PD weighted image is…

64
Q

A scan with a long TR and long TE will have what weighting?

65
Q

TR range for a T2 weighted image is…

A

2000-6000ms

66
Q

TE range for a T2 weighted image is…

67
Q

What are the 3 factors that control contrast for an inversion recovery squence?

68
Q

A spin echo pulse sequence preceded by a 180 RF pulse is…..

A

An inversion recovery pulse sequence

69
Q

An inversion recovery sequence with a short TI is…

70
Q

An inversion recovery sequence with a long TI is…

71
Q

The time between 180° preparation pulse and the 90° excitation pulse during an inversion recovery sequence is known as…

A

TI (inversion time)

72
Q

A 90° RF followed by 180° RF produces what type of pulse sequence?

73
Q

A 90° RF followed by train of 180° RF pulses produces what type of pulse sequence?

A

Fast Spin Echo (FSE)

74
Q

A 180° RF followed by 90°RF produces what type of pulse sequence?

A

Inversion Recovery

75
Q

A variable° RF followed by gradient to produce echo produces what type of pulse sequence?

A

Gradient Echo

76
Q

____ corresponds to the amount of radiofrequency energy deposited in the patient, which may result in heating.

77
Q

As the flip angle is doubled, the RF absorption increases by a factor of __________.

78
Q

The pulse sequence that should be utilized the least in a patient with implanted metallic hardware is:

A

Gradient echo

Gradient echo sequences lack a 180° RF pulse that aids in correcting local magnetic field inhomogeneities, found in metallic implants.

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