Sequences and Image Contrasts Flashcards
the time between two 90 RF excitation pulses
repetition time (TR)
the time between the 90 RF pulse and the peak of the signal in the receiver coil
echo time (TE)
T1’s use __ TRs and ___ TEs
T1= short TR and short TE
What is the normal TR range for T1 images?
350-700 MS
The ___ the TR the more T1 weighted it will be.
Shorter/longer
shorter TR = more T1
What is the normal range for TE on a T1 image?
10-30 (think SHORT TE for T1)
ON a T1 image
Water is ___
dark or bright?
dark
On a T1 image
Fat is ___
dark or bright?
bright
What are another name for a T1 image?
spin lattice
Is T1 better for ANATOMY or PATHOLOGY?
ANATOMY!! think A comes first in the alphabet…A for T1
PD stands for proton density. These sequences will have a ____ TR and a ___ TE?
short / long
PD= Long TR and Short TE
What is the normal TR range for a PD image?
1600-4000
What is the normal range for TE on a PD image
10-30
a proton density image is basically canceling out both T1 and T2 properties.
True. We want to minimize both T1 and T2. PD is neither T1 or T2.
T2s use a ___ TR and a ___ TE.
Long TR + Long TE = T2
What is the normal TR for T2 images?
2000-6000
WHat is the normal TE of a t2?
80-120
Does the TE or the TR control T2 weighting?
TE controls T2
Increasing the T2 weighting of an image can be done by increasing the ___
TR or TE?
TE
On T2s, fluid is ___
bright or dark?
t2= BRIGHT fluids
On T2s, fat is typically ___
dark or bright?
T2- fat is dark
When we are scanning an inversion recovery sequence, what is the contrast controlled by?
The TR the TE or the TI?
All three! Inversion recovery is controlled by TE TR and TI (inversion time)
The T1 of adipose tissue is shorter than the T1 of water
True or False
True
What does STIR stand for?
Short TI inversion recovery
STIRs use specific timing to suppress the signal from fat. True or False?
TRUE, that’s why they are so dark.
a spin echo pulse sequence preceded by a 180 RF pulse is what type of sequence??
STIR
Why with a STIR do we do the 180 RF Pulse?
it inverts the starting magnetization which then returns to its equilibrium according to T1 relaxation.
During a STIR, Fat
will reach its null point faster than white matter, grey matter, water or edema, and
so an image of these structures can be generated
True
make the TI long and
you have the FLAIR pulse sequence, which suppresses signal from fluid
True or False
True
Enabling Driven Equilibrium (DRIVE: Philips) will enable the operator to increase TR
and preserve contrast
FALSE
Enabling Driven Equilibrium (DRIVE: Philips) will ENABLE the operator to reduce TR
and preserve contras
When does the presaturation pulse typically occur?
prior to excitation or after the excitation pulse?
prior
Fat suppression techniques suppress based on the precessional frequency of ___
Fat
90 RF followed by 180 RF is what type of pulse sequence?
Spin echo, fast spin echo, inversion recovery or a gradient echo.
Spin Echo
90 RF followed by a train of 180 RF pulses is what type of pulse sequence?
Spin echo, fast spin echo, inversion recovery or a gradient echo.
fast spin echo.
a 180 RF followed by a 90 RF is what type of pulse sequence?
Spin echo, fast spin echo, inversion recovery or a gradient echo.
inversion recovery
variable RF followed by gradient to produce echo
this is what type of pulse sequence?? Spin echo, fast spin echo, inversion recovery or a gradient echo.
gradient echo.
What are examples of extrinsic contrast parameters ( ones that MR techs can adjust to alter image)
TR, TE, flip angle, TI and ETL
What are examples of intrinsic paramters ( specific to tissue and cannot be changed by MR tech)
ADC, T1 AND T2 times, specific proton density, and flow
What are some structures that will ALWAYS appear black on an MRI image?
air, tendons, ligaments, metallic susceptibility and cortical bone.
