Random Flashcards
The Sag T2, demonstrates a post stenotic jet in which region?
Aqueduct of Sylvius
What is the artefact in this image caused by?
RF leak
What is the artefact in this image caused by?
Metallic implant
Use FSE to try and reduce artefacts from metal implants
In half NEX imaging, it is necessary to acquire what percentage of the phase?
A little more than 50% (55%)
A PD sequence using a wider rBW will result in?
Decreased sampling rate
Which of the following occurs when the rBW is increased?
A) increased SNR
B) reduced chemical shift
C) reduced sampling rate
D) decreased sampling rate
B) reduced chemical shift
What does the 180-degree refocusing pulse in a SE sequence correct for?
Precessional differences between fat and water
In a FSE sequence with long effective TE, scan time can be reduced by the selection of:
A) large FOV
B) longer ETL
C) shorter ETL
D) there are no ETL changes that could affect scan time
B) Longer ETL
Increasing the number of slices (or partitions) in a 3D acquisition from 32 to 128 will increase the SNR by a factor of….
A) 2
B) 4
C) 6
D) square root of 2
D) square root of 2
What will using a zero-fill or interpolation technique to reduce scan time also reduce?
A) SNR
B) Reconstructed voxel size
C) flow artifacts
D) FOV
A) SNR
The attractive force of an object will experience at 2 metres from isocentre is not dependent on what?
A) the mass of the object
B) the ferromagnetic properties of the object
C) the field strength of the machine
D) slew rate of the machine
D) slew rate of the machine
Which of the following are important in an MRA sequences to minimise the loss of signal due to dephasing within a voxel?
A) long TR
B) low frequency matrix
C) long TE
D) small voxels
C) Long TE
In magnetic resonance angiography (MRA), TE stands for Echo Time, a term referring to the time from the application of the radiofrequency pulse to the peak of the echo signal in MRI. A shorter TE time (short TE) helps reduce signal loss because it minimizes the period during which dephasing can occur within a voxel, thus preserving more of the signal.
In a TOF sequence, flowing blood is hyperintense relative to stationary tissue because of the…?
A) T2 effect
B) coil being used
C) saturation pulse being used
D) flow related signal
D) flow related signal
When referring to a half NEX or partial Fourier sequence, which of the following is true?
A) spatial resolution remains the same
B) SNR is increased
C) less susceptible to periodic motion
D) increase in scan time
C) Less susceptible to periodic motion
K space is an array of numbers, what process generates the MR image?
A) Fourier transform
B) synthetic transform
C) compress sensing
D) parallel imaging
A) Fourier transform
In which directions do pulsatile motion artefacts occur in?
A) both phase and frequency
B) frequency
C) phase
D) can be in any direction depending on the TR used
C) phase
What is the artefact demonstrated in Image 12 known as?
A) wrap
B) zipper
C) truncation
D) flow
A) wrap
In this image, what direction would the phase direction be in?
A) A->P
B) R->L
C) superior to inferior
D) cannot determine
A) A->P
Increasing the FOV by a factor of 2, the SNR will increase by what factor?
A) square root of 3
B) 2
C) 8
D) 4
A) square root of 3?
At what point is phase encoding performed?
A) prior to frequency encoding
B) in place of frequency encoding
C) during frequency encoding
D) after frequency encoding
A) prior to frequency encoding