Fundamentals of MRI

Question 1

Precessional frequency is measured in :

Answer 1

MHZ

Question 2

The ratio of a magnetic moment to its angular momentum

Answer 2

Gyromagnetic Ratio

Question 3

Gyromagnetic ratio is measured in

Answer 3

MHz/T

Question 4

Processional frequency of hydrogen is

Answer 4

42.5 MHz/t (1T scanner) 63.8 MHz/T (1.5 scanner)

Question 5

The circular track that wobbling nuclei follow around the external magnetic field

Answer 5

Precessional path

Question 6

Occurs when a nucleus is exposed to an oscillation that has a frequency close to its own

Answer 6

Resonance

in order for resonance to occur the frequency of transmitted RF must be the same as the precessional frequency of the atoms with which the RF interacts

Question 7

What occurs during resonance?

Answer 7

Spins flip into the transverse plane
Spins precess in-phase with eachother
Spins absorb energy from the transmitted RF pulse

Question 8

What is another term for “in-phase”

Answer 8

Coherent

Question 9

Spin up/ parallel protons are in which state

Answer 9

Low energy state

Question 10

Spin down/ anti parallel protons are in which state

Answer 10

High energy state

Question 11

When a hydrogen spin moves into the opposing energy state after the application of an RF pulse that is oscillating at the precessional frequency of hydrogen

Answer 11

Energy state transition

Question 12

What is the natural decay of the net magnetization vector directly after the application of an RF pulse?

Answer 12

Free Induction Decay (FID)

Question 13

Inherent characteristics

Answer 13

T1 Relaxation
T2 Decay
Proton Density
T2* Decay
Diffusion
Flow
Perfusion

Question 14

Which occurs faster or slower, T1 or T2 relaxation

Answer 14

T1 is slower relaxation than T2

Question 15

T2* weighting is a result of dephasing due to

Answer 15

Both T2 decay and magnetic field inhomogeneities

Question 16

What tissue characteristic represents the relative number of hydrogen protons per unit volume?

Answer 16

Proton Density

Question 17

Only Nuclei with a _______ mass number contain a magnetic moment

Answer 17

Odd

Question 18

What is another name for the XY plane?

Answer 18

Transverse plane

Question 19

Traditional closed-bore scanners have a _________ XY plane, whereas open-bore scanners have a _________ XY plane

Answer 19

Vertical / Horizontal

Question 20

What Axis is oriented in the same direction as the magnetic field?

Answer 20

Z Axis - also known as the longitudinal axis

Question 21

Traditional closed-bore scanners have a _________ Z plane, whereas open-bore scanners have a _________ Z plane

Answer 21

Horizontal / Vertical

Question 22

What planes belong to which physical gradient?

Answer 22

Axial - Z Gradient
Sagittal - X Gradient
Coronal- Y Gradient

Obliques- multiple sets of physical gradients

Question 23

The _________ usually spatially encodes the signal sampled along the short axis of anatomy

Answer 23

Phase Encoding Gradient

Question 24

The phase encoding gradient is switched on after the application of the ______ and before the application of the________.

Answer 24

Alpha Pulse / RF rephasing pulse

Question 25

The _______and ______ of the phase encoding gradient determines which line of k-space will be filled during readout

Answer 25

Slope / Polarity

Question 26

The gradient applied during the sampling of the echo is the :

Answer 26

Frequency Encoding Gradient
Also known as the readout gradient

Question 27

The frequency encoding gradient is applied during the ________

Answer 27

Collection of the echo

Question 28

The number of frequencies sampled during the collection of the echo is determined by the:

Answer 28

Frequency matrix

Question 29

A spatial frequency domain that serves as a temporary storage space for data collected during image acquisition

Answer 29

K-Space

Question 30

K spaced is composed of how many axes

Answer 30

2 - Phase axis and frequency axis

Question 31

Steep Phase encoding gradient slopes store _______ within the _______ of k-space

Answer 31

Spatial resolution information / Periphery

Question 32

Shallow Phase encoding gradient slopes store _______ within the _______ of k-space

Answer 32

Contrast information / center