Chap 4 Mri

Front 1

at equilibirum
1)there in no______ to net magnetization
2)the Z component is at its _______

Back 1

-XY
-maximum value of Mo

Front 2

an RF pulse at the larmor frequency causes net magnetizaiton vector to ______

Back 2

-flip thru the angle

Front 3

flipping net magnetization from Zaxis reduces ...

Back 3

Mz and increases Mxy

Front 4

after an RF pulse
1)that flips net magnetization from Z axis the XY component rotates at the ______
2)the Z component of net magnetization Mz returns back to

Back 4

-larmor frequency
-equilibrium

Front 5

wat is the smiplest MRI RF pulse sequence
1)equilibirum followed by a ______ to equilibrium w emission of an RF sognal

Back 5

-relaxation

Front 6

in MRI, wat does the frequency of precession depend on
1)type of ________ of the external magnetic field
2)all precess about themagnetic field are out of phase isnt a net magnetic field in the ______

Back 6

-nucleus and intensity
- XY plane

Front 7

individual magnetizations sum to net magnetization parallel to the direction of the ______

Back 7

-external magnetic field

Front 8

at equilibrium there is no signal received from the pt because the net magnetization vector (M) points only in the ______

Back 8

-Z direction (Mz)

Front 9

for a signal to be received from a pt
1)magnetization vector must be rotated from the _____ so that it has some nonzero component in the XY plane

Back 9

-Z axis

Front 10

If the RF is not at the larmor frequency
1) the nuclei doesnt ______, and net magnetization is not rotated

Back 10

-absorb energy

Front 11

larmor frequency corresponds to the _______ in the RF range

Back 11

-electromagnetic radition

Front 12

number of aligned nuclei depend on _______ of the magnetization field

Back 12

-intensity

Front 13

1)wat controls how fast the nuclei rotate into the plane _______
2)wat controls how far the nuclei will rotate in the XY plane the _______

Back 13

-strength of the RF pulse
-duration of the RF pulse

Front 14

1)hard pulses _______
2)soft pulses _______

Back 14

-strong, short pulses
-weaker longer pulses

Front 15

1)180 RF pulse rotates the net magnetization vector from
2)90 degree pulse rotates the net magnetization vector from

Back 15

-equilibrium to Z axis
-equilibrium on to the XY plane

Front 16

spins are saturated after a 90 degree RF pulse so that

Back 16

Mz=0
Mxy=Mo

Front 17

name 2 ways a 90 degree magnetization vector can be achieved

Back 17

by hard or soft pulses

Front 18

1)the decreasing of Mxy is called
2)the increasing of Mz is called

Back 18

-T2 (transverse relaxation)
-T1 (longitudinal relaxation)

Front 19

the increaing of Mz is called

Back 19

T1(longitudinal relaxation)

Front 20

1)flip angle how far the net magnetization has _____

Back 20

-rotated

Front 21

the net magnetization field partially saturated
1) wen Mz is _____ than Mo
2)Mxy is no longer _____

Back 21

-smaller
-zero

Front 22

explain how after excitation RF pulse the magnetization vector is made up of 2 independent process
1)-the XY component precess at the ______ and it shrinks onto until it disappears
2)the Z component gradually grows until it reaches its maximum value at _______

Back 22

-larmor frequency
-equilibrium

Front 23

wat is the primary signal that the receiving coil senses is the ________ which represents the decreasing MR signal

Back 23

free induction decay

Front 24

the FID oscillates a wat frequency

Back 24

larmor frequency

Front 25

wat about the amplitude and shape of FID pulse
1)the amplitude is oftenn equaled to and always ________
2)the equilibrium value,therefore it depends on ________

Back 25

-dependent on Mo
-PD(photon density), λ, Bo

Front 26

RT (repetition time)
1)______ signal
2)represented as a series of ovals w a label above which indicates whether the net magnetization angle is induces is 90 180 degree or other _______

Back 26

-tranmitted
-partially saturated angle