All of the following yield a higher Signal-to-Noise ratio EXCEPT:
A. Increase TR
B. Increase TE
C. Larger FOV
D. Higher NEX
E. Decrease Matrix
B. Increase TE
Increasing TE allows for more T2 decay to occur before the signal is measured, which results in lower signal and therefore a decrease in SNR
The repetition time is the?
Time between two 90 RF Pulses
Which RF pulse refocuses a decaying spin echo?
A. 90
B. 180
C. 67
D. 30
180
180 RF pulse is the refocusing pulse.
A technologist wants to generate a proton density weighted image. To do this, they should select a spin echo sequence with which parameters?
A. Long TR, Long TE
B. Short TR, Short TE
C. Long TR, Short TE
D. Short TR, Long TE
C. Long TR, Short TE
A long TR minimizes T1 contrast by allowing all tissues to fully recover. A short TE minimizes T2 contrast by capturing the signal before significant T2 decay occurs
The Echo Time (TE) is the:
Time between the 90 RF pulse and the peak signal in receiver coil
In a spin echo sequence, the time between the 90 RF pulse and the 180 RAF pulse is know as the:
A. TR
B. TE
C. 1/2 TE
D. TI
E. Double echo
C. 1/2 TE
In a spin echo sequence, the 180 refocusing pulse must be applied at the halfway point to the echo. This is known as Tau and its equal to one-half of the Echo Time (TE)
The gradient that is on during the production of the echo is the:
A. Slice select gradient
B. Phase encoding gradient
C. Frequently encoding gradient
D. Inversion recovery gradient
C. Frequency encoding gradient
Frequency encoding gradient is known as the “readout gradient” must be active during the collection of the echo.
When performing a gradient echo pulse sequence, what is used to refocus the protons and create the echo?
A. A focus group
B. Shim coils
C. RF coils
D. Gradient coils
D. Gradient Coils
All of the following are types of inversion recovery sequences EXCEPT:
A. STIR
B. DWI
C. FLAIR
D. 3D-IR
B. DWI
STIR and FLAIR are classic IR sequences. DWI is typically built upon fast spin echo or, more commonly, an echo planar image backbone, not IR sequence.
In order to produce an echo in a gradient echo pulse sequence, a _____ is used.
A. RF Pulse
B. Gradient field
C. Combination of two pulses
D. 180 pulse, then 90 pulse
E. All of the above
F. A & B only
A & B only
A gradient echo is created first by an RF pulse, which creates transverse magnetization, and then by a bipolar gradient field which dephases and rephases that magnetization to form the echo.
Which RF pulse is always absent in a gradient echo sequence?
A. 90 excitation pulse
B. 180 refocusing pulse
C. Presaturation pulse
D. Flip angle pulse
B. 180 refocusing pulse
Which of the following combinations of flip angle (FA) and TR would produce a T2 weighted gradient echo?
A. 45 TR, 30 flip angle
B. 45 TR, 90 flip angle
C. 450 TR, 30 flip angle
D. 450 TR, 90 flip angle
C. 450 TR, 30 flip angle
In an inversion recovery sequence, the time interval between the 180 RF pulse and the 90 RF pulse is the:
A. TR
B. TI
C. TE
D. 3T
B. TI
It’s the time the system waits after the initial 180 inverting pulse before applying the 90 excitation pulse. The length of the TI determines which tissue signal will be nulled
What is a SE sequence?
Uses 90 excitation pulse + 180 degree refocusing pulse.
