chap 1&10 review

Question 1

the static magnetic field is referred to as

Answer 1

B0

Question 2

the signal/voltage is only induced if there is _______ magnetization in the transverse plane that is in-phase

Answer 2

coherent

Question 3

high energy nuclei align their magnetic moments in the anti - parallel direction are ________ nuclei

Answer 3

spin-down

Question 4

process by which hydrogen loses its energy

Answer 4

relaxation

Question 5

application of an RF pulse that causes resonance, “energy giving”

Answer 5

excitation

Question 6

relationship between angular momentum & the magnetic moment of each MR-active nucleus

Answer 6

gyromagnetic ratio

Question 7

when an object is exposed to an oscillating perturbation that has a frequency close to its own natural frequency of oscillation

Answer 7

resonance

Question 8

balance between spin-up and spin-down nuclei

Answer 8

NMV

Question 9

what are 2 results of resonance

Answer 9

• NMV moves out of alignment with B0
• magnetic moments move into phase with each other

Question 10

most abundant atom in the human body

Answer 10

hydrogen

Question 11

the atomic number comes from

Answer 11

the sum of protons

Question 12

the atomic mass comes from

Answer 12

the sum of protons & neutrons in the nucleus

Question 13

the precessional frequencies of MR-active nuclei fall within which band of the electromagnetic spectrum

Answer 13

radio frequency

Question 14

the time from the application of the RF excitation pulse to the peak of the signal

Answer 14

TE

Question 15

the point in a pulse sequence from the excitation pulse to the echo of the signal

Answer 15

TE (time to echo)

Question 16

the time from the application of one RF excitation pulse to the application of the next RF pulse for each slice

Answer 16

TR (time to repetition)

Question 17

the position of the magnetic moment at any point of time is recorded as their

Answer 17

phase

Question 18

what best refers to the position of the magnetic moment on their precessional path as it travels 360 degrees during one rotation

Answer 18

phase

Question 19

protium has a atomic number & mass number of

Answer 19

1

Question 20

even atomic number & mass number

Answer 20

forces cancel out , no spin

Question 21

odd number of protons, neutrons, or both

Answer 21

has net spin, or angular momentum

Question 22

unit of precessional frequency

Answer 22

Hertz

Question 23

the three types of motion inherent within the atom with angular momentum

Answer 23

• electrons spinning on their own axis
• electrons orbiting the nucleus
• nucleus itself spinning about its own axis

Question 24

T/F: the number of spin-up / spin-down is directly related to the strength of the magnetic field

Answer 24

true

Question 25

T/F: high energy nuclei possess enough energy to oppose the magnetic field

Answer 25

true

Question 26

most commonly used MR active nucleus in MRI

Answer 26

protium

Question 27

the Larmor equation

Answer 27

precessional freq. = B0 strength (x) gyromagnetic ratio

Question 28

unit of phase

Answer 28

radian

Question 29

measure of how quickly the phase position of magnetic moments change over time

Answer 29

frequency

Question 30

not in the same place on the precessional path, aka incoherent

Answer 30

out-of-phase

Question 31

magnetic moments in the same place on the precessional path around B0 at any time, aka coherent

Answer 31

in-phase

Question 32

current opposes the change in magnetic field , refers to which law

Answer 32

Lenz’s Law

Question 33

governs precessional frequency

Answer 33

Larmor Equation

Question 34

refers to 3 forces (motion, magnetism, & charge) and states that if two of these are present, then the 3rd is automatically induced

Answer 34

Faraday’s Law of Electromagnetic Induction

Question 35

the gyrometric ratio of Hydrogen on 1T

Answer 35

42.58 MHz

Question 36

the gyrometric ratio of Hydrogen on 3T

Answer 36

127.74 MHz

Question 37

patient heating/burns, antenna effect, & adverse effects on implant function can all be attributed to

Answer 37

the RF field

Question 38

the energy wavelength in MRI

Answer 38

RF

Question 39

responsible for determining the amount of energy that is deposited and translated across our patients

Answer 39

RF

Question 40

when a stationary object twists or rotates

Answer 40

rotational force

Question 41

when an object moves from one point to another

Answer 41

translational force

Question 42

translational force likelihood increases

Answer 42

closer to isocenter

Question 43

translational force likelihood decreases

Answer 43

away from isocenter

Question 44

the magnet’s static field is responsible for 4 main safety related effects

Answer 44

- transient biological effects - projectile hazards - torque on implants - translational force on foreign bodies

Question 45

magnetic field outside the bore, not confined to ceilings, floors, or walls

Answer 45

fringe field

Question 46

reversible amplitude of the T-wave

Answer 46

hematodynamic effect

Question 47

tips for reducing SAR

Answer 47

- increasing TR - reducing flip angle - using a different local receiver coil - removing/reducing presaturation pulses - scanning on lower field strength magnet