Excitation and Relaxation

Question 1

What is the direction of low energy and spin up?

Answer 1

parallel to B0

Question 2

What represents direction and magnitude?

Answer 2

vector

Question 3

What is the direction of low energy and spin up?

Answer 3

parallel to B0

Question 4

What is the direction of high energy and spin down?

Answer 4

antiparallel to B0

Question 5

What is the speed of the wobble called?

Answer 5

precessional frequency

Question 6

What is the Larmor Equation?

Answer 6

w0 = yB0

Question 7

What is the phenomenon when an RF cause resonance to occur?

Answer 7

excitation

Question 8

What is the term for the position of each magnetic moment on the precessional path around B0?

Answer 8

phase

Question 9

What is the sum of the magnetic effects of all the protons exposed to the main B0?

Answer 9

Net Magnetic Moment (Net Magnetization Vector)

Question 10

What is 1 Tesla equal to in Gauss?

Answer 10

10,000 gauss

Question 11

What’s the gyromagnetic ratio for hydrogen?

Answer 11

42.57 mHz/T

Question 12

What’s the phenomenon that permits the efficient transfer of energy from one object or system to another?

Answer 12

resonance

Question 13

What’s the plane which is perpendicular to the longitudinal direction?

Answer 13

transverse plane

Question 14

What are the 2 factors Flip Angle depend on?

Answer 14

1. RF amplitude
2. RF pulse duration

Question 15

What’s the angle between the starting position of the NMV and the resultant position after the delivery of the RF energy?

Answer 15

RF Flip Angle

Question 16

What is the Flip Angle most often used with spin echo?

Answer 16

90 degree

Question 17

What is the Flip Angle most often used with gradient echo?

Answer 17

less than 90 degree

Question 18

What’s the process by which energy is lost to the environment?

Answer 18

relaxation

Question 19

What is the recovery of longitudinal magnetization caused by?

Answer 19

T1 recovery

Question 20

What is the decay of transverse magnetization caused by?

Answer 20

T2 decay

Question 21

What are the 2 types of relaxation?

Answer 21

1. T1 or spin-lattice
2. T2 or spin-spin

Question 22

Is T1 dependent on T2?

Answer 22

No. both occur simultaneously, but completely independent of one another

Question 23

What’s T1 relaxation?

Answer 23

the time required for the net magnetization to grow to 63% of its final amplitude

Question 24

What’s the signal decay due to the transverse dephasing called?

Answer 24

free induction decay (FID)

Question 25

What's T2 relaxation?

Answer 25

the time at which the transverse magnetization has decayed to 37% of its full value due to spin-spin interactions

Question 26

What lines up with the main B0 along the longitudinal direction?

Answer 26

the net magnetization of protons

Question 27

What caused the magnetization to move into the transverse plane?

Answer 27

90 degree RF pulse

Question 28

What caused the magnetization to rephrase and form an echo?

Answer 28

180 degree RF pulse

Question 29

What contains the contrast information to differentiate the appearance of the soft tissues of the body in the resulting MR image?

Answer 29

the echo

Question 30

What's the time from one 90 degree pulse to the next 90 degree pulse called?

Answer 30

TR (repetition time)

Question 31

What's the time from the 90 degree pulse to the peak of the signal called?

Answer 31

TE (echo time)

Question 32

Which sequence parameters is great for demonstrating anatomy?

Answer 32

T1 weighting

Question 33

Which sequence parameters is great for demonstrating pathology?

Answer 33

T2 weighting

Question 34

What is the term for small dipole magnet associated with hydrogen?

Answer 34

magnetic moment

Question 35

What causes the motion of magnetic moment to exist?

Answer 35

isotope protium