An aneurysm of the aortic arch root would be found in the
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ascending portion of the thoracic aorta
In a Fast Spin Echo sequence, the effective TE are the echoes that are
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encoded with a low amplitude phase encoding gradient. This sould occur
at the line that is closest to the center of k-space (k0), and may occur at the
beginning or end of the shot, depending on the profile order.
,Shortening of Phase encoding direction steps/process, typically more than half of k-
space needs to be
Give this one a try later!
acquired (~60%) to perform the Halfscan function, made possible due to
the symmetry in k-space data, where negative values are identical to phase
encoding positive values. This enables slightly more than half of k-space as
mandatory acquisition, but will affect the overall SNR in the image. Also
known as "Partial Fourier" or Half Fourier," implementing this option reduces
the overall scan time with an SNR penalty, particularly useful in protocols
with thick slices and high SNR.
Reducing the number of times the phase encoding steps are performed significantly
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reduces MRI scan time, decreased by the parallel imaging factor selected.
For instance, a 5 minute sequence utilizing a parallel imaging factor of 2
results in a two minute thirty second overall scan time.
T1 Recovery (longitudinal magnetization)
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,Gradient echo sequences are
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extremely susceptinble to metal artifacts, and contain little mechanism for
the distortion cause by ferrous material in a superconducting magnet.
The condition of steady state occurs when the
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TR in a gradient echo is less than the T2 (or T2*), resulting in residual
transverse magnetization at the time of the next excitation pulse
Scan time is reduced by a factor matching the number of
Give this one a try later!
, echo train lengths (TSE Factor--Philips, utilized in the fast spin echo pulse
sequence because several echoes for each slice are collected during each
TR period. Each train of echoes in a fast spin echo sequence reduces scan
tome but also lowers SNR and increases SAR absorption in the patient.
RF heating is more of a concern in
Give this one a try later!
fast spin echo sequences due to the multiple echo train lengths, leading to
potential increases in tissue heating.
-Factors that increase sequence scan time
Parameter Adjustment: Decrease ETL/TSE Factor
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Reducing the additional 180 degree RF refocusing pulses increases the
overall scan time as the train of spin echoes shorten the overall scan time in
a Fast Spin Echo Sequence: TR x Phase Matrix x NEX divided by ETL = Scan
Time
Parameters increasing overall Signal-to-Noise Ratio (SNR)
-Increased NSA/NEX
Give this one a try later!
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ascending portion of the thoracic aorta
In a Fast Spin Echo sequence, the effective TE are the echoes that are
Give this one a try later!
encoded with a low amplitude phase encoding gradient. This sould occur
at the line that is closest to the center of k-space (k0), and may occur at the
beginning or end of the shot, depending on the profile order.
,Shortening of Phase encoding direction steps/process, typically more than half of k-
space needs to be
Give this one a try later!
acquired (~60%) to perform the Halfscan function, made possible due to
the symmetry in k-space data, where negative values are identical to phase
encoding positive values. This enables slightly more than half of k-space as
mandatory acquisition, but will affect the overall SNR in the image. Also
known as "Partial Fourier" or Half Fourier," implementing this option reduces
the overall scan time with an SNR penalty, particularly useful in protocols
with thick slices and high SNR.
Reducing the number of times the phase encoding steps are performed significantly
Give this one a try later!
reduces MRI scan time, decreased by the parallel imaging factor selected.
For instance, a 5 minute sequence utilizing a parallel imaging factor of 2
results in a two minute thirty second overall scan time.
T1 Recovery (longitudinal magnetization)
Give this one a try later!
,Gradient echo sequences are
Give this one a try later!
extremely susceptinble to metal artifacts, and contain little mechanism for
the distortion cause by ferrous material in a superconducting magnet.
The condition of steady state occurs when the
Give this one a try later!
TR in a gradient echo is less than the T2 (or T2*), resulting in residual
transverse magnetization at the time of the next excitation pulse
Scan time is reduced by a factor matching the number of
Give this one a try later!
, echo train lengths (TSE Factor--Philips, utilized in the fast spin echo pulse
sequence because several echoes for each slice are collected during each
TR period. Each train of echoes in a fast spin echo sequence reduces scan
tome but also lowers SNR and increases SAR absorption in the patient.
RF heating is more of a concern in
Give this one a try later!
fast spin echo sequences due to the multiple echo train lengths, leading to
potential increases in tissue heating.
-Factors that increase sequence scan time
Parameter Adjustment: Decrease ETL/TSE Factor
Give this one a try later!
Reducing the additional 180 degree RF refocusing pulses increases the
overall scan time as the train of spin echoes shorten the overall scan time in
a Fast Spin Echo Sequence: TR x Phase Matrix x NEX divided by ETL = Scan
Time
Parameters increasing overall Signal-to-Noise Ratio (SNR)
-Increased NSA/NEX
Give this one a try later!
