What will happen to voxel size if:
- Resolution is increased
- Scan time is kept the same
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Decrease voxel size
What will happen to spatial resolution if:
- Scanning time is decreased
- SNR is kept the same
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Decrease in spatial resolution
,Explain T2 relaxation
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After the 90º RF pulse, the net magnetization vector (now called transverse
magnetization) is rotating in the X-Y plane around the Z-axis. The vectors all
point in the same direction because they are In-Phase. Over time, the spins
lose their phase coherence and begin to decay (dephase) until they are
completely out-of phase. This process of getting from a total in-phase
situation to a total out-of-phase situation is called T2 relaxation. T2 is
defined as the time it takes for the spins to de-phase to 37% of the original
value.
What is the Larmor frequency?
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The Larmor frequency refers to the rate of precession of the magnetic
moment of the proton around the external magnetic field. It depends upon
the strength of the magnetic field. The stronger the magnetic field, the
faster the precession rate and the higher the Larmor frequency.
What is the net magnetisation prior to the RF pulse being applied?
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It usually points in the same direction as the z-axis which is always parallel
to the direction of the main magnetic field. The net magnetisation in this
case would be called Mz or longitudinal magnetisation.
, When TI = 150, what tissue type will not generate any signal?
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Fat tissue
K space is a frequency domain space, this frequency refers to _______________, the unit of
the k-space data is _________________
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?
Cycles per cm or hertz
What is the difference between T2 and T2*?
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T2 is defined as a time constant for the decay of transverse magnetization
arising from natural interactions at the atomic or molecular levels.
T2* can be considered an "observed" or "effective" T2, which results
principally from inhomogeneities in the main magnetic field.
When the gradient is equal to zero, the signal intensity will be ___________?
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- Resolution is increased
- Scan time is kept the same
Give this one a try later!
Decrease voxel size
What will happen to spatial resolution if:
- Scanning time is decreased
- SNR is kept the same
Give this one a try later!
Decrease in spatial resolution
,Explain T2 relaxation
Give this one a try later!
After the 90º RF pulse, the net magnetization vector (now called transverse
magnetization) is rotating in the X-Y plane around the Z-axis. The vectors all
point in the same direction because they are In-Phase. Over time, the spins
lose their phase coherence and begin to decay (dephase) until they are
completely out-of phase. This process of getting from a total in-phase
situation to a total out-of-phase situation is called T2 relaxation. T2 is
defined as the time it takes for the spins to de-phase to 37% of the original
value.
What is the Larmor frequency?
Give this one a try later!
The Larmor frequency refers to the rate of precession of the magnetic
moment of the proton around the external magnetic field. It depends upon
the strength of the magnetic field. The stronger the magnetic field, the
faster the precession rate and the higher the Larmor frequency.
What is the net magnetisation prior to the RF pulse being applied?
Give this one a try later!
It usually points in the same direction as the z-axis which is always parallel
to the direction of the main magnetic field. The net magnetisation in this
case would be called Mz or longitudinal magnetisation.
, When TI = 150, what tissue type will not generate any signal?
Give this one a try later!
Fat tissue
K space is a frequency domain space, this frequency refers to _______________, the unit of
the k-space data is _________________
Give this one a try later!
?
Cycles per cm or hertz
What is the difference between T2 and T2*?
Give this one a try later!
T2 is defined as a time constant for the decay of transverse magnetization
arising from natural interactions at the atomic or molecular levels.
T2* can be considered an "observed" or "effective" T2, which results
principally from inhomogeneities in the main magnetic field.
When the gradient is equal to zero, the signal intensity will be ___________?
Give this one a try later!
