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MRI Procedures & Patho Phys > Module 1 > Flashcards

Module 1 Flashcards

(88 cards)

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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
30-48 cm
large FOV
26
determined by region of interest (ROI)
FOV determining factor
27
1-4 mm
thin slice
28
5-6 mm
medium slice gap
29
8 mm or more
large slice
30
industry standards Reading Rad's preferences/protocols
slice thickness determining factor
31
increase SNR increase slice per acquisition decreased T1 weighting increase scan time
TR increased
32
decreased scan time increased T1 weighting decreased SNR decreased slices per acq
TR decrease
33
increased T2 weighting decreased SNR
TE increase
34
increase SNR decrease T2 weighting
TE decrease
35
increased SNR all tissue reduce motion artifact (signal averaging) direct proportional increase in scan time
NEX (NSA) increase
36
direct proportional decrease in scan time decrease in SNR all tissues increased motion artifact
NEX (NSA) decrease
37
increase SNR all tissues increase coverage of anatomy decrease spatial resolution and partial voluming
slice thickness increase
38
increase spatial resolution and reduce partial voluming
slice thickness decrease
39
increase SNR increase coverage of anatomy decrease spatial resolution
FOV increased
40
decreased SNR decrease coverage of anatomy increase likelihood of aliasing
FOV decreased
41
increase spatial resolution decrease SNR increase scan time
matrix increased
42
increase SNR decrease scan time decrease spatial resolution
matrix decreased
43
decrease minimum TE decrease in chemical shift decreased SNR
Rcve bandwidth increased
44
increase SNR increase minimum TE increase chemical shift
decrease bandwidth
45
90/180 re-phasing
SE
46
90/multiple 180's (ETL)
FSE
47
180/90/180 pulse sequence
IR/FSE-IR inversion recovery
48
STIR FLAIR T1 & T2
use inversion recovery pulses
49
use variable flip angle followed by gradiaent rephasing to produce GRE
coherent gradiant echo T2
50
steady state sequence that uses very short TR for rapid acquisition times and large flip angles to increase SNR
balanced gradient echo T2
51
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
incoherent gradient echo T2 spoiled GRE
52
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
steady state free precession T2
53
very fast sequences such as EPI best for moving structures
real time imaging
54
rapid acquistion of images either after contrast or to observe movement
dynamic imaging
55
rap[id technique that acquires images of the brain during activity or stimulus and at rest
functional imaging
56
demonstrates areas with restricted diffusion of extracellular water such as infarcted tissue
diffusion weighted imaging DWI
57
refers to microscopic changes in perfusion when gadolinium first passes through the cappillary bed
perfusion imaging
58
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
TOF
59
12-20 sec breath holds used for long vessels
ceMRA
60
fat haemangioma intra osseous ipoma radiatino change degen fatty deposit methaeglobin cysts w/proteinaceous fluid paramagnetic contrast agent slow flowing blood
high T1
61
CSF synovial fluid hemangioma infection inflammation oedema some tumors hemorrhage slow flowing blood cysts
high T2
62
cortical bone AVN infarction infection tumors sclerosis cysts calcification
low T1
63
cortical bone bone islands deoxyhemoglobin hemosiderin calcification T2 paramagnetic agents
low T2
64
air fast flowing blood ligaments tendons cortical bone scar tissue calcificatoin
low to no T1 and T2
65
TOF entry slice intra voxel dephasing
most common flow phenomena
66
occurs when nuclei move through the slice may receive only one of the RF pulses applied.
Time of flight phenomena
67
depends on excitation history of nuclei flowing within a vessel largely controlled by the direction of flow relative to slice excitation
entry slice phenomena
68
cuased by presence of gradients that either accelerate or decellerate flowing nuclei as they move from areas of differeing field strenght along the gradient
intra voxel dephasing
69
spatial presaturation pulses GMN (FC)
main flow artifact remedies
70
nullifies signal from nuclei that produce unwanted signal or artefact by applying a 90 RF pulse to selected tissue before the pulse sequence begins
spatial presaturation
71
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
spatial presaturation
72
utilizes extra gradients to rephase the magnetic momnets of flowing nuclei so that they have a similar phase to their stationary counterparts
GMN FC
73
produces high signal from flowing nuclei increases the minu=imum TE and may reduce slice number available maine reduces intra-voxel dephasing
gradient moment nulling GMN
74
P
Atrial contraction
75
QRS somplex
contraction of ventricles
76
T
relaxation of ventricles
77
represents original pace making pulse imput from the SA node no more than 3mm high .12 sec in duration
P wave
78
time between onset of P wave and QRS complex .12 to .20 sec
PR interval
79
depolarization (contraction) of ventricles .08-.11sec in duration
QRS complex
80
time between the depolarization and beginning of repolarization of ventricles
ST segment
81
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
T wave
82
1 R to R interbal
T1 weighting
83
2-3 R to R intervals
Pd/T2 weighting
84
15-20% of R to R interval
trigger window
85
min allowed for maximun # of slices
trigger delay
86
breath holding navigators respiratory respiraory compensation
forms of respiratory compensation and gating
87
9 types gadolinium strongly paramagnetic
positive contrast agents
88
historically iron oxide super para-magnetic
negative contrast agents

MRI Procedures & Patho Phys (5 decks)

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