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MRI Procedures & Patho Phys > Module 1 > Flashcards

Module 1 Flashcards

1
Q

Basic RF coil

typically single coil loop using singel receiver channel

A

linear coil

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2
Q

coil set 90 relative to each other

able to receive the MR signal in 2 planes

effect is double the signal and double the noise

noise cancels itself

net result 40% increase in SNR

net 10% increase in SNR from flat coils

A

quadrature coil

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3
Q

multi coil

series of loops arranged in order to increase coverage or increase SNR over same area

needs RF amplifiers and receivers on system

A

phased array coils

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4
Q

arranged in coil pairs 90 relative to each other

multi coil

series of loops arranged in order to increase coverage or increase SNR over same area

needs RF amplifiers and receivers on system

A

Quadrature phased array coils

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5
Q

ability to send RF pulses as well as collect the MR signal

A

send and receive coils

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6
Q

ability to collect MR signal only

A

receive only coils

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7
Q

cervical

thoracic

lumbar

full spine

carotid MRA

anterior and soft tissue neck

A

phased array C/T/L coil

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8
Q

coil for

knee

ankle

foot

A

phased array extremity coil

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9
Q

amplitude of signal received by coil to the amplitude of the noise

A

SNR

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10
Q

voltage induced in coil

A

signal

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11
Q

constant value dependant on the area under exam and electrical background of the system

A

noise

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12
Q

SE & FSE sequences

long TR & short TE

90 flip angle

A

increase SNR

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13
Q

well tuned coils

coarse matrix

large FOV

thick slices

A

increase SNR

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14
Q

narrow bandwidth

high order signal averages

A

increase SNR

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15
Q

NEX

NSA

A

increase SNR

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16
Q

difference in the SNR between two adjacent structures

A

CNR

Contrast Noise Ratio

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17
Q

admin of contrast agents

t2 sequences with fat sat

STIR (tissue suppression)

FLAIR (fluid attenuated Inv Recovery)

sequences that enhance flow (time of flight)

A

increase CNR

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18
Q

control spatial resolution (voxel size)

thin slices

fine matrices

small FOV

A

increase CNR

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19
Q

256x128

A

course matrix

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20
Q

256x256

A

medium matrix

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21
Q

512x512

A

fine matrix

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22
Q

1024x1024

A

very fine matrix

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23
Q

18 cm or less

A

small FOV

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24
Q

19-29 cm

A

medium FOV

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25
Q

30-48 cm

A

large FOV

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26
Q

determined by region of interest (ROI)

A

FOV determining factor

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27
Q

1-4 mm

A

thin slice

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28
Q

5-6 mm

A

medium slice gap

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29
Q

8 mm or more

A

large slice

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30
Q

industry standards

Reading Rad’s preferences/protocols

A

slice thickness determining factor

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31
Q

increase SNR

increase slice per acquisition

decreased T1 weighting

increase scan time

A

TR increased

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32
Q

decreased scan time

increased T1 weighting

decreased SNR

decreased slices per acq

A

TR decrease

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33
Q

increased T2 weighting

decreased SNR

A

TE increase

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34
Q

increase SNR

decrease T2 weighting

A

TE decrease

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35
Q

increased SNR all tissue

reduce motion artifact (signal averaging)

direct proportional increase in scan time

A

NEX (NSA) increase

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36
Q

direct proportional decrease in scan time

decrease in SNR all tissues

increased motion artifact

A

NEX (NSA) decrease

37
Q

increase SNR all tissues

increase coverage of anatomy

decrease spatial resolution and partial voluming

A

slice thickness increase

38
Q

increase spatial resolution and reduce partial voluming

A

slice thickness decrease

39
Q

increase SNR

increase coverage of anatomy

decrease spatial resolution

A

FOV increased

40
Q

decreased SNR

decrease coverage of anatomy

increase likelihood of aliasing

A

FOV decreased

41
Q

increase spatial resolution

decrease SNR

increase scan time

A

matrix increased

42
Q

increase SNR

decrease scan time

decrease spatial resolution

A

matrix decreased

43
Q

decrease minimum TE

decrease in chemical shift

decreased SNR

A

Rcve bandwidth increased

44
Q

increase SNR

increase minimum TE

increase chemical shift

A

decrease bandwidth

45
Q

90/180 re-phasing

A

SE

46
Q

90/multiple 180’s (ETL)

A

FSE

47
Q

180/90/180 pulse sequence

A

IR/FSE-IR

inversion recovery

48
Q

STIR

FLAIR T1 & T2

A

use inversion recovery pulses

49
Q

use variable flip angle followed by gradiaent rephasing to produce GRE

A

coherent gradiant echo T2

50
Q

steady state sequence that uses very short TR for rapid acquisition times and large flip angles to increase SNR

A

balanced gradient echo T2

51
Q

use variable flip angle and gradient rephasing resulting in a GRE

commonly used in steady state so residual magnetization builds up in the transverse plane

A

incoherent gradient echo T2

spoiled GRE

52
Q

steady state sequence uses medium flip angles and short TR to maintain the steady state pulse so residual magnetization builds up in the transverse plane

A

steady state free precession T2

53
Q

very fast sequences such as EPI

best for moving structures

A

real time imaging

54
Q

rapid acquistion of images either after contrast or to observe movement

A

dynamic imaging

55
Q

rap[id technique that acquires images of the brain during activity or stimulus and at rest

A

functional imaging

56
Q

demonstrates areas with restricted diffusion of extracellular water such as infarcted tissue

A

diffusion weighted imaging

DWI

57
Q

refers to microscopic changes in perfusion when gadolinium first passes through the cappillary bed

A

perfusion imaging

58
Q

usually uses an incoherent (spoiled) GRE sequence in conjunction with TR and flip angle combination that saturate background tissue but allow moving spins to enter the slice fresh and return a high signal

A

TOF

59
Q

12-20 sec breath holds

used for long vessels

A

ceMRA

60
Q

fat

haemangioma

intra osseous ipoma

radiatino change

degen fatty deposit

methaeglobin

cysts w/proteinaceous fluid

paramagnetic contrast agent

slow flowing blood

A

high T1

61
Q

CSF

synovial fluid

hemangioma

infection

inflammation

oedema

some tumors

hemorrhage

slow flowing blood

cysts

A

high T2

62
Q

cortical bone

AVN

infarction

infection

tumors

sclerosis

cysts

calcification

A

low T1

63
Q

cortical bone

bone islands

deoxyhemoglobin

hemosiderin

calcification

T2 paramagnetic agents

A

low T2

64
Q

air

fast flowing blood

ligaments

tendons

cortical bone

scar tissue

calcificatoin

A

low to no T1 and T2

65
Q

TOF

entry slice

intra voxel dephasing

A

most common flow phenomena

66
Q

occurs when nuclei move through the slice may receive only one of the RF pulses applied.

A

Time of flight phenomena

67
Q

depends on excitation history of nuclei flowing within a vessel

largely controlled by the direction of flow relative to slice excitation

A

entry slice phenomena

68
Q

cuased by presence of gradients that either accelerate or decellerate flowing nuclei as they move from areas of differeing field strenght along the gradient

A

intra voxel dephasing

69
Q

spatial presaturation pulses

GMN (FC)

A

main flow artifact remedies

70
Q

nullifies signal from nuclei that produce unwanted signal or artefact by applying a 90 RF pulse to selected tissue before the pulse sequence begins

A

spatial presaturation

71
Q

produces low signal from flowing nuclei

reduces motion and aliasing if bands are placed over signal producing anatomy

increases the specific absorptin rate (SAR) and may reduce slice number available per TR

mainly reduces TOF and entry slice phenomena

A

spatial presaturation

72
Q

utilizes extra gradients to rephase the magnetic momnets of flowing nuclei so that they have a similar phase to their stationary counterparts

A

GMN

FC

73
Q

produces high signal from flowing nuclei

increases the minu=imum TE and may reduce slice number available

maine reduces intra-voxel dephasing

A

gradient moment nulling

GMN

74
Q

P

A

Atrial contraction

75
Q

QRS somplex

A

contraction of ventricles

76
Q

T

A

relaxation of ventricles

77
Q

represents original pace making pulse imput from the SA node

no more than 3mm high .12 sec in duration

A

P wave

78
Q

time between onset of P wave and QRS complex

.12 to .20 sec

A

PR interval

79
Q

depolarization (contraction) of ventricles

.08-.11sec in duration

A

QRS complex

80
Q

time between the depolarization and beginning of repolarization of ventricles

A

ST segment

81
Q

recovery phase after ventricular contraction

flowing blood in body make an artifact in the ECG that obscures normal wave when patient is inside the magnet

A

T wave

82
Q

1 R to R interbal

A

T1 weighting

83
Q

2-3 R to R intervals

A

Pd/T2 weighting

84
Q

15-20% of R to R interval

A

trigger window

85
Q

min allowed for maximun # of slices

A

trigger delay

86
Q

breath holding

navigators

respiratory

respiraory compensation

A

forms of respiratory compensation and gating

87
Q

9 types

gadolinium

strongly paramagnetic

A

positive contrast agents

88
Q

historically iron oxide

super para-magnetic

A

negative contrast agents

MRI Procedures & Patho Phys (5 decks)

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