Exam 1 Of Mri 7200

Front 1

What’s the major limitation with GRE?

Back 1

TE is not long enough to measure the T2 time of tissues. Rephrasing is inefficient so T2* dominates. T2weighting cannot be achieved.SSFP

Front 2

SSFP overcomes T2 issue by?

Back 2

Digitizing frequencies from only stimulated echo and not FID

Rewind gradient to speed up rephrasing

Te longer then Tr

Actual Te is time b/ether echo and next excitation pulse

Effective Te time from echo to the excitation pulse that created the FID

Front 3

Rephrasing is created by ?

Back 3

RF pulse rather then gradient

Front 4

Balanced gradients

Back 4

Modification to coherent GRE to correct phase errors with flow/CSF and alternating RF to enhance steady state.

Positive GRE equals negative GRE = zero phase change in moving spins

High flip < shorter TRs , high SNR short scan times

Imaging heart

Front 5

Fast echo GRE

Back 5

Developed to acquire a volume in single breath hold

Coherent or incoherent with short TEs

Partial echos

Additional ore-magnetization pulse

Provide Temporal resolution

Front 6

Pre magnetization achieved 2 ways?

Back 6

180 pulse before the pulse sequence begins

90/180/90 combination is applied before pulse sequence begins

Second 90 drives the transverse magnetization into longitudinal plane so available to flip when sequence begins

Produces T2 contrast

Driven Equilibrium

Front 7

Kspace filling fast GRE

Back 7

Centric kspace and keyhole filling

Front 8

Centric filling

Back 8

Fills line by line Center first

Maximizes SNR and contrast

Front 9

Keyhole filling

Back 9

Line by line but central lines filled during certain part of sequence

Useful in angio

Front 10

RF pulse applied

Back 10

Excitation purposes (spin echo: rephrasing)

Front 11

Gradients applied

Back 11

Spatial encode the signal and rephrase and rephrase spins

Front 12

Intervening time periods

Back 12

Time intervals b/w these functions

Front 13

CSE first and second echos

Back 13

First echo is T1

Second echo is PD

Front 14

T2W CSE echos

Back 14

First echo is PD

Second echo is T2W

Front 15

FSE weighting

Back 15

Multiple echos at different TEs has wide range of weighting’s

Effective TE at console to select weighting

Front 16

FSE appearances

Back 16

Fat bright on T2W - multiple RF effects on spin spin interactions (j coupling) fat sat can be used

Muscle appears darker

Reduced sensitivity to hemorrhage b/c multiple 180 reduce magnetic susceptibility

Great to use for implants

Blurring at edges of tissues

Front 17

Turbo factor 2-8 for T1 and PD

12-30 for T2W

Back 17

Short scan times great image quality increased T2 info

Front 18

SSFSE details

Back 18

All lines kspace in one TR

Half lines acquired in one TR, other half transposed

Reduced scan times but penalty in SNR

Increase in SAR

Deems csfbright

Front 19

Inversion recoveryIR

Back 19

Begins with 180 inversion pulse to flip into full saturation

90 pulse applied after determined TI

Then rephrased by another 180 to produce spin echo at time TE

Front 20

Stir parameters

Back 20

TI 150-175

TE 50+

TR 4000+

Turbo factor 16-20

Scan time 4-15 mins

Front 21

FLAIR parameters

Back 21

TI 1700-2200ms

TE 70+

TR 6000+

Turbo factor 16-20

Scan time 6-20mins

Front 22

IR contrast depends on

Back 22

T1W - 90 applied after NMV has relaxed back to transverse plane

PD - 90 pulse is not applied until NMV has fully recovered (fat and water relaxed)

Front 23

IR weighting’s

Back 23

T1

PD

Pathology weighted

Front 24

IR

Back 24

Long scan times unless used in conjunction with FSE

Front 25

Two types of FastIR

Back 25

STIR and FLAIR

Front 26

STIR

Back 26

TI time corresponds to time it takes fat to recover from full inversion to the transverse plan

Front 27

TI time of null fat

Back 27

100-175

Front 28

STIR facts

Back 28

Contrast can’t be used due to shortened TI times

Used for MSK

Front 29

FLAIRTI

Back 29

Chosen to null fluid

Front 30

TI time of CSF

Null white matter

Back 30

1700-2200ms

300ms white matter

Front 31

IR prep double

Back 31

Two 180 non slice selective

Black blood imaging null at 800ms

Imaging morphology of heart

Front 32

TripleIR prep

Back 32

Third 180

TI of fat (150ms) to null both fat and blood

Used for heart wall

Front 33

Conventional GRE Echo

Back 33

Variable flip angle less then 90

Reduced scan time

Frequency encoding gradient applied negatively

Polarity is reverses to positive to producing rephrasing of the gradient echo

Doesn’t compensate for magnetic field inhomogeneities so displays t2*

Used to acquire T1 PD T2* weightings

Front 34

Parameters T1 weighting

Back 34

Flip 70-110

Tr <50

Te 1-5

Scan time 2sec-2min

Front 35

Parameter t2*

Back 35

Flip 5-20

Tr 200+

Te 15-25

Time 5sec-5min

Front 36

Parameter PD

Back 36

Flip 5-20

Tr 200

Te 5-10

Time 5sec-5min

Front 37

GRE rise time

Back 37

Time it takes to reach maximum amplitude

Front 38

Slew rate

Back 38

Speed and strength to reach maximum amplitude

Front 39

Duty cycle

Back 39

Percentage of time GRE permitted you work

Front 40

Spatial resolution requires

Back 40

Maximum amplitude or strength of a GRE

Front 41

Me signal is sampled during?

Back 41

Frequency encoding GRE only after it reaches maximum amplitude and occurs at time TE

Front 42

RF coils consist of

Back 42

Transmit and receive

Front 43

RF transmitters

Back 43

Transmit to resonance of hydrogen

Known as the body coil

Front 44

Faraday cage is

Back 44

Using copper shielding in scan room walls windows and teeth along door frame. If compromised RF artefact called zipper can result

Front 45

MR computer consist of

Back 45

Computer system

Pulse control unit

Array processor

Image processor

Hard drive

Power distribution

Console