MRI practice/questions Flashcards
How to reduce Scan time
Reduce TR
Reduce NEX/NSA
Increase Parallel Imaging factor
Utilize half fourier
Use coarsest matrix possible
What happens when TR is increased
Increased SNR
Increased Scan time
Decreased T1 weighting
Increased number of Avail. Slices
What happens to TE when increased
Decreased SNR
Increased scan time
Increased T2 weighting
Decreased number of avail. slices
What is another name for incoherent gradient echo sequence?
Spoiled gradient echo sequence
Incoherent gradient echo (spoiled echo gradient) yield what type of contrast due to removal of residual transverse magnetization before next excitation
T1 contrast
To reduce steady state (T2*) effect, a technique known as what can be employed to allow for fast scans with T1 contrast
Spoiling
In a spine echo sequence the time between the 90 degree RF pulse and the 180 degree RF pulse is known as the
1/2 TE time (Tau)
How does Echo Train Length affect other parameters
Reduces scan time
Reduces SNR
Increases SAR absorption
Increases blurring
In a fast spin echo pulse sequence, if the TSE factor is increased by a factor of 3, the scan time will be how many times faster
Three
In an inversion recover sequence, the time interval between the 180 degree RF pulse and the 90 degree RF pulse is the
TI (inversion time)
What directly results as the frequency matrix increases?
SNR decreases
At what distasnce should an attached IV bag be hung above the IV site?
18-24 inches
What plane best demonstrates the Cruciate ligaments of the knee
Sagittal
An image with hyperintense signal from fluid/water and hypointense fluid signal from fat would be what type of image contrast?
T2 contrast
What type of image data acquisition imaging option in which all data is acquired as a volume with no gap space?
3D imaging
What imaging option applies an extra 90 degree RF pulse prior to the alpha pulse to null signal from user specified areas of unwanted anatomy?
Spatial saturation pulse
What term represents the difference in SNR between 2 adjacent pixels?
Contrast to noise ratio
What ratio of compressions to breaths should be applied for CPR?
30 compressions/ 2 breaths
After the injection of GAD, scar tissue within the spines disc spaces enhance how quickly?
Immediately
What cranial nerves run through the IAC’s?
VII and VIII
Normal GFR is
90ml/min/1.73m or higher
Gradient moment nulling is applied during the acquisition of coronal or sagittal images, which gradient is used for flow compensation?
Frequency encoding gradient
Which of the following directly results as ETL increases?
T2 weighting increases
What is The FDA SAR limit for torso exams
8 W/kg over 5 mis
At 1.5T Flair pulse sequences use an inversion time in the approx. range of _______ in order to null the signal from fluid
1700-2200ms
Coherent Gradient echo sequences are typically used to obtain what weighted images?
T2*
Which factor has the greatest effect on entry slice phenomenon?
Direction of flow
What term best describes an infection or illness originating from a medical exam or treatment?
Iatrogenic infection
Trunctation artifact can be compensated for by
increasing the NSA/NEX and increasing the phase encoding matrix
The T2 decay time of fat is approx
100ms
What plane best demonstrates the pituitary gland
Coronal and sagittal
The fastest form of data acquisition is achieved by which pulse sequence
Echo planar pulse sequences
During a steady state pulse sequence, if two excitation pulses with a variable flip angle are applied, which echo is created?
Conventional echo
Which of the following directly results as the phase matrix increases?
Spatial resoltion increases
During TOF imaging, what TR is used to saturate stationary non-flowing spins?
20-50ms
