AMRI 300 weeks 6-10

Why is a gradient recalled echo (GRE) sequence faster than a spin echo (SE) sequence?

Question 1Select one:

The use of a long TR

The lack of 180 degree RF pulse and lower flip angle

The use of a 90 degree RF excitation pulse

The use of inversion time

The lack of 180 degree RF pulse and lower flip angle

Due to the decreased efficiency in refocusing spins, this pulse sequence is extremely sensitive to magnetic field homogeneity:

Question 2Answer

SE

GRE

IR

3DFT

GRE

What term describes the signal that follows the application of the initial 90-degree RF pulse?

Question 3Answer

Spin echo

Gradient echo

FID

Hahn echo

FID

Which of the following is NOT an advantage when performing GRE over SE pulse sequences?

Question 4Answer

Dramatically reduced scan times (due to short TR)

Lower RF power deposition

True T2 tissue contrast acquired

Increased number of slices per unit time

True T2 tissue contrast acquired

The peak signal strength of a spin echo is less than the initial strength of the FID because of ___________.

Question 5Answer

Magnetic susceptibility

T1 relaxation

T2 relaxation

Proton concentration

T2 relaxation

Why is a Spin Echo pulse sequence able to produce true T2 weighted images?

Question 6Answer

The 90 degree excitation pulse gives full transverse magnetization

The 180 re-focusing pulse corrects T2* decay and makes it true T2

There's no double FEG application, so that makes it true T2

The long 'dead time' after the 180 allows it

The 180 re-focusing pulse corrects T2* decay and makes it true T2

1

A pulse sequence that starts with a 90-degree RF pulse and is followed by only one 180-degree RF pulse is characterized as ___________ type of pulse sequence?

Question 8Answer

IR

GRE

CSE

Fat Saturated or Fat Suppressed

CSE

Compared to T2 weighted images, T2* looks:

Question 9Answer

More clear

Higher resolution

More crisp

Grainier (less signal rich)

Grainier (less signal rich)

A pulse sequence is repeated with similar parameters for all of K-space to make sure:

Question 2Answer

To mix T1 and T2 weighting in K-Space

To improve log function dynamic

For faster Fourier Transform

The image is diagnostic and has the same contrast all throughout

The image is diagnostic and has the same contrast all throughout

To flip the spins into the XY plane

To re-phase the spins after the FID to create an echo

To decrease the spin curve regression

To increase SAR

To re-phase the spins after the FID to create an echo

How can Spin Echo sequences create true T2 image contrast?

Question 6Answer

The 180 refocusing pulse corrects for chemical shift, susceptibility, and inhomogeneities.

Faster ADC enables this.

They are slower than GRE.

They have full transverse magnetization.

The 180 refocusing pulse corrects for chemical shift, susceptibility, and inhomogeneities.

Fast Spin Echo accelerates scan time by:

Question 7Answer

Using very short TRs

Using very short TEs

Using a low NEX value

Creating several echos every TR

Creating several echos every TR

What is Echo Train Length?

Question 8Answer

The middle sections of K-Space

The number of 180 refocusing pulses and echos created every TR

The time between echos

The time between 90's

The number of 180 refocusing pulses and echos created every TR

What is the ETL shown here?

Question 10Answer

1

2

3

4

5

3

FSE

GRE

CSE

STIR

GRE

Why does a larger flip angle produce more T1 weighting?

Question 15Answer

Allows for greater separation/contrast in Fat and Water spins as they return to Bo.

Makes the scan longer overall, and that always creates more T1 contrast.

Allows more time for the spins to de-phase.

Allows more turbo factor, which extends the TE

Allows for greater separation/contrast in Fat and Water spins as they return to Bo.

You should think of Ernst Angle as:

Question 16Answer

The null-point

The lowest possible flip angle

The fastest flip angle

The unrestrained flip angle

The optimal flip angle

The optimal flip angle

No difference in signal

Less signal

More signal

Less signal from Gadolinium

Less signal

Inversion Recovery Sequences start with:

Question 18Answer

Beta

A 180 degree inversion pulse

A 180 degree re-phasing pulse

Alpha

A 90 degree excitation pulse

A 180 degree inversion pulse

At 1.5 Tesla, a Tau of ~150 ms will be called a Short Tau Inversion Recovery Sequence, and void:

Question 19Answer

Watery tissue

Tendons and ligaments

Fatty tissue

Cancerous lesions

Fractures and Contusions

Fatty tissue

At 1.5 Tesla, a Tau of ~2000 ms will be called a Fluid Attenuation Inversion Recovery Sequence, and void:

Question 20Answer

Watery tissue

MS Lesions

Fatty tissue

Fractures and Contusions

Tendons and ligaments

Watery tissue

Gradient Recalled Echo uses:

Question 21Answer

a.

A 180 degree re-focusing pulse

b.

A turbo factor

c.

The FEG to re-phase the spins

d.

A variable flip angle

e.

An inversion pulse

C AND D

Which of these are advantages of GRE?

Question 22Answer

a.

Can be used to detect hemorrhage

b.

Short scan time (compared to SE)

c.

Lower SNR

d.

Creates more acoustic noise

e.

Less SAR

a,b,e

What is the purpose of IR?

Question 23Answer

a.

Void fluid

b.

Scan quicker

c.

Give T2* weighting

d.

Void fat

e.

Create more acoustic noise

a, d

One of the reasons we don't use the FID, is that it hasn't been spatially encoded by the PEG and FEG. This means the system doesn't know where to put it in K-Space.

Question 25Select one:

True

False

true

true

Any sequence with a 90 degree excitation pulse and a 180 degree re-phasing pulse is definitely SE or some variation.

Question 29Select one:

True

False

true

FSE, TSE, and RARE all mean the same thing.

Question 31Select one:

True

False

true

GRE heats the patient more than TSE.

Question 34Select one:

True

False

true

A sequence without 180 degree re-focusing pulses can still produce true T2 weighted images.

Question 35Select one:

True

False

false

Gradient applications can de-phase, but also re-phase the NMV.

Question 36Select one:

True

False

true

What mechanism rephases the dephasing hydrogen nuclei in a SE sequence?

Question 1Answer

180-degree RF pulse

90-degree RF pulse

The free induction decay signal (FID)

Gradient reversal after the 90-degree RF pulse

180-degree RF pulse

For a GRE sequence, what parameter suffers?

Question 3Select one:

Signal-to-noise ratio (SNR)

FOV

Resolution

Scan time

Signal-to-noise ratio (SNR)

In an IR pulse sequence, what is the term for the time between the initial 180-degree and the 90-degree RF pulse?

Question 4Answer

TE

TR

TI

T1

TI

FEG being turned on during readout.

SEG turned on during the RF.

90 degree excitation pulse

PEG turned on to a different strength every TR.

PEG turned on to a different strength every TR.

The above picture shows the time and events diagram of a ______ sequence

Question 8Select one:

SE

FSE

Double Echo SE

GRE

SE

note: 1 90 degree pulse followed by 1 180 degree pulse

A pulse sequence that starts with a 90-degree RF pulse and is followed by only one 180-degree RF pulse is characterized as ___________ type of pulse sequence?

Question 12Answer

IR

GRE

CSE

Fat Saturated or Fat Suppresse

CSE

Which parameter controls whether an IR sequence will be a STIR or a FLAIR?

Question 14Answer

TI (Tau)

ETL

TE

TR

ETS

TI (Tau)

Gfe

Gpe

Gss

Gra

Gss

These lines would show:

Question 18Answer

RF Pulses

Analog to digital conversions

Gradient activity

Signal in the receive coil

Gradient activity

In GRE a total of _____ RF pulse/s are used in each TR

Question 19Select one:

3

2

1

4

1

In SE a total of _____ RF pulse/s are used in each TR

Question 20Select one:

1

4

2

3

2

After injection, paramagnetic contrast agents affect patient tissue in which of the following ways?

Question 1Answer

Decrease T1 relaxation time

Decrease T1 and T2 relaxation time

Increase T1 relaxation time

Increase T2 relaxation time

Decrease T1 and T2 relaxation time

For FGRE sequences, a steady state is achieved by:

Question 2Answer

TR=T1/T2

T1/TR/T2 x PEG steps

TR<T2<T1

TR = T1 squared x T2

TR<T2<T1

By repeatedly applying RF pulses with a short TR, the residual TM is refocused and contributes to the signal, leading to a steady state where the longitudinal (LM) and transverse (TM) magnetizations remain relatively constant from one TR to the next. 

What is an oral agent used in MRI that is also used in CT?

Question 3Select one:

VoLumen

Radiopharmaceuticals

Iodinated contrast

Gadolinium

VoLumen

Many 0.3T open scanners ______.

Question 4Select one:

Higher net magnetism when compared to higher fields

The option for higher transverse magnetism when compared to higher fields

Do not have the capability of obtaining a T1 weighted image

Do not have a chemical fat saturation option

Do not have a chemical fat saturation option

At lower field strengths like 0.3T, the frequency difference between fat and water signals is smaller, making it difficult for the RF pulse to isolate and suppress fat effectively

Which of these pulse sequences has a mechanism to minimize the effect of slight inhomogeneities in the magnetic field?

Question 5Answer

CSE

GRE

PC-TOF

None of the above

CSE

The 180 degree refocusing pulse?

What can be run post gadolinium injection to obtain a fat saturation image?

Question 6Select one:

Chemical Fat Saturation

Standard T2

Standard T1

STIR

Chemical Fat Saturation

No, STIR (Short TI Inversion Recovery) sequences are generally not recommended after gadolinium administration in MRI. STIR is a fat suppression technique that relies on T1 relaxation times, and gadolinium shortens T1, potentially causing both fat and enhanced tissue to appear dark, obscuring the desired contrast effect. 

At 1.5 T the difference between water and fat precessional frequency is about:

Question 8Answer

220 Mhz

220 Hz

3 Hz

120 Hz

440 Hz

220 Hz

The most common way GBCA's are used in clinical MRI sequences, is to take advantage of their:

Question 9Answer

Ferrous properties

Increased T2 times

Increased T1 times

Diamagnetic properties

Increased T1 times

The most important attribute of Steady State GRE sequences is their:

Question 3Answer

Extremely short TR's

Echo Train Length

T2 image weighting

Thick slices

Extremely short TR's

FGRE sequences that begin with a combination of RF pulses before the sequence begins are known as:

Question 4Answer

Prepared

Inverted

Exam Refined

Rectified

Prepared

How does flow compensation work?

Question 5Answer

Extra FEG lobes to correct for flow artifact.

Uses spoilers to reduce phase coherence between TRs.

Three PEG applications every TR.

Extra inversion pulses to correct for flow artifact.

Extra FEG lobes to correct for flow artifact.

Brain tumors are seen very well post gad because:

Question 6Answer

They have low proton density.

These tumors disrupt the blood-brain barrier and allow the gad into them.

They increase T2 times.

They stay enhanced longer than other tissues.

These tumors disrupt the blood-brain barrier and allow the gad into them.

Why do MS lesions show up as T2 hyperintensities?

Question 8Answer

That area has hemorrhage.

MS is an infection.

Inflammatory processes are generally T2 hyperintense.

MS are malignant tumors.

Inflammatory processes are generally T2 hyperintense.

Why do protocols include post contrast T1 Fat/Sat sequences?

Question 9Answer

Because fatty tissue is abnormal.

Because abnormal areas are T2 hyperintense.

To help differentiate abnormal enhancement from regular fatty tissue.

To reduce scan time.

To help differentiate abnormal enhancement from regular fatty tissue.

Why couldn't you just have the patient drink a lot of water as PO contrast for an MR of the abdomen?

Question 10Answer

The peristalsis would create too much motion.

It would be too T2 hyperintense to be diagnostic.

The SAR levels would increase rapidly.

The patient would need to urinate and be unable to finish the exam.

The water would be quickly absorbed by the jejunum.

The water would be quickly absorbed by the jejunum.

Fat Saturation sequences saturate the fatty tissue with what?

Question 13Answer

Signal

RF energy

Gradients

Contrast

RF energy

The number of slices that can be scanned in one concatenation/acquisition depends on:

Question 18Answer

Bo

Resolution

TE

FOV

TR

TR

Max number of slices is 12 with the TR you've selected. You prescribe 40 slices. Without changing TR, how many concatenations are required for this sequence?

Question 19Answer

1

2

3

4

5

4

The purpose of a gap in between slices is:

Question 20Answer

Increase in-plane resolution

Reduce partial-voluming

Eliminate or reduce cross-talk

Decrease gradient load

Eliminate or reduce cross-talk

If slice order was 1,2,3,4,5,6,7,8, it would be called:

Question 22Answer

Interleaved

Extricated

Interpolated

Contiguous

Extrapolated

Contiguous

If slice order was 1,3,5,7,2,4,6,8 it would be called:

Question 23Answer

Extrapolated

Interleaved

Extricated

Interpolated

Contiguous

Interleaved

SSFSE is used for:

Question 25Answer

a.

Cardiac MRI

b.

Spine MRI

c.

Ankle MRI

d.

Abdomen MRI

e.

Fetal MRI

A,D,E

Which pulse sequences combine Spin Echo and Gradient Recalled Echo components?

Question 26Answer

a.

EPI

b.

SPGRE

c.

SE DWI EPI

d.

GRASE

e.

SSFSE

c,d

Which types of contrast are no longer approved or no longer produced?

Question 28Answer

a.

Gadolinium Chelate Injections

b.

Iron Oxide Injections

c.

PO contrast made of Gadolinium, Manganese, or Iron

d.

Manganese Injections

b,c,d

Which are names for Fat Saturation?

Question 29Answer

a.

F/S

b.

CHESS

c.

Chemical Fat Suppression

d.

IR Prep

e.

DWI

a,c

What are the drawbacks of increasing slice thickness?

Question 30Answer

a.

Lower T1 and T2 contrast

b.

Lower in-plane resolution

c.

Lower matrix size

d.

Possible partial-voluming of small pathology

b,d

Which are advantages of increasing slice thickness?

Question 31Answer

a.

Less slices are required to cover a volume of anatomy

b.

Less cross-talk

c.

More slices can be obtained in every concatenation

d.

Better signal to noise

a,d

All MRI pulse sequences are built on a variation of either SE or GRE.

Question 32Select one:

True

False

true

Double Echo Spin Echo acquires a line of K-Space for a T1 weighted image and a T2 weighted image during each TR.

Question 34Select one:

True

False

flase

it acquires a PD and a T2 at the same time NOT T1

Fractional NEX and Partial Fourier mean the same thing.

Question 35Select one:

True

False

true

Areas with faster T1 relaxation are brighter on T1 weighted images.

Question 36Select one:

True

False

true

Eovist liver protocols should include a 20 minute delayed 'hepatobiliary' phase after the injection.

Question 37Select one:

True

False

true

STIR sequences can be used to see IV gad enhancement.

Question 39Select one:

True

False

false

bc the contrast shortens the t1 and t2 times to the point that the frequencies of water and fat become too unpredictable. if we don’t know the exact processional rates and inversion time required to null one of them (oversaturate), we cant do a proper STIR