Unit 6 Flashcards
What is a spin echo sequence?
90 degree pulw follwed by a 180 degree pulse
What is a gradient echo sequence?
<90 degree pulse followed by gradient echo
What is an inversion recovery sequence?
180 degree pulse followed by a 90 degree pulse, then a 180 degree pulse
What is echo time?
time between excitation and receiving signal
What is inversion time?
time between 180 degree pulse an 90 degree pulse in IR sequences
What TR values are used in T1 weighted images?
<800msec (short)
What TE values are used in T1 weighted images
<25msec (short)
What TR values are used in T2 weighted images?
> 2,000msec
What TE values are use in T2 weighted images?
> 80msec
What TR values are used in PD weighted images?
> 2,000msec
What TE values are used in PD weighted images?
<35msec
advantages of GRE over SE
shorter scan time
Advantages of SE over GRE
180 degree pulse compensates for inhomogeneity, greater signal
What type of sequence is T2*?
GRE
What is the use of IR imaging?
signal suppression (fat vs fluid)
How does gadolinium create contrast?
shortens T1 and T2 relaxation time
How does contrast appear on T1 weighted images?
increased intensity
How does contrast appear on T2 weighted images?
decreased intensity
Why does gadolinium not significantly affect T2 weighted images?
there isn’t enough gadolinium concentration
What makes gadolinium contrast safe to administer?
the gadolinium is bound in an inert substance.
