PS 1 Flashcards
In a pulse sequence diagram, gradient indications are for physical or logical gradients?
Logical
In a spin echo sequence, the 90° RF Pulse place the LMV into the________
transverse plane
In a spin echo pulse sequence, immediately after the 90° RF pulse the spins are in the ________ plane & are ________ coherent.
in the TRANSVERSE plane & are PHASE coherent.
Completing all of the selected number of phase encoding steps in a spin echo sequence is equivalent to _______ NEX/NSA
1
Doubling the NEX / NSA yields approximately a ____________.
40% increase in SNR.
Another term for “frequency encoding” is
readout
In a spin echo pulse sequence, ______ phase encoding steps are collected every TR period.
1
The domain where phase encoding data is stored is called
K-Space
In a spin echo pulse sequence, how many TR periods occur if the user selected 200 phase encoding steps?
200
In a spin echo sequence, FID stands for what?
Free Induction Decay
True or False:
The Set-up Pulse is an essential step shown in a pulse sequence diagram.
False
In a pulse sequence diagram, “GX” indicates what?
Gradient used for Frequency encoding
In a pulse sequence diagram, “GZ” indicates what?
gradient used for slice encoding
in a spin echo pulse sequence, the time from one 90° RF Pulse to the next 90° RF pulse is:
TR
In a spin echo pulse sequence, the phase encoding gradient is turned on when?
immediately following the 90° RF pulse
The purpose of gradients is to change the _______ of spins.
the precessional frequency of the spins.
What are the 4 categories of magnetic susceptibility?
Diamagnetic
Paramagnetic
Super-Paramagnetic
Ferromagnetic
What is defined as the tendency of a substance to attract or repel magnetic lines of force dependent on the magnetic properties of its electrons?
Magnetic Susceptibility
In K-space, the outer lines conatin the majority of the _______ information.
Spatial Resolution
The purpse of phase & frequency encoding gradients is to _______.
Spatially locate where the signals are coming from.
What are the 4 main parts of every pulse sequence?
Slice Excitation
Phase encoding
Frequency encoding (readout)
Echo Generation
In a spin echo pulse sequence, if TR is increased, what happens to your scan time?
Scan time is increased.
(Also increases T1w)
In a spin echo pulse sequence, if the time from the 90° RF Pulse to the 180° RF Pulse is INCREASED, then _______ is also increased.
TE
In a spin echo pulse sequence, the REFOCUSING PULSE is accomplished by using a ______ RF pulse.
A 180° RF Pulse.
In K-space, the central or middle lines contain the majority of the ________.
SNR / Contrast
Substances with ________ susceptibility weakly attract or repel magnetic lines of force.
Magnetic susceptibility of most human body tissues are described as _______.
Diamagnetic
What is the function of the “SET-UP” pulse?
to create the desired amount of T1 relaxation.
In a spin echo pulse sequence, the only thing that changes from one TR period to the next is the:
Phase encoding gradient
(Gy)
In a spin echo pulse sequence, FID immediately:
Dephased & Phase encoded.
In a spin echo pulse sequence, if the TE is increased, what happens to T2W?
t2w is increased.
In a spin echo sequence, the first RF Pulse is the________
slice excitation 90° RF Pulse
In a spin echo pulse sequence, what is the first gradient that is used?
Slice Encoding Gradient (Gz)
In a spin echo pulse sequence, for the best proton density weighting, use a long TR and ______ TE.
short.
In a spin echo pulse sequence, for the best T1 weighting, use a ________.
moderate TR.
