Overview of MRI Physics

Question 1

Magnetic Resonance Imaging (MRI) utilizes the behavior of ___ or ___, n the human body.

Answer 1

hydrogen nuclei, or protons,

Question 2

Single charged spinning nucleon

Answer 2

Hydrogen

Question 3

behave like tiny bar magnets.

Answer 3

Hydrogen nuclei

Question 4

exhibits magnetism due to its angular momentum and magnetic moment.

Answer 4

hydrogen nucleus

Question 5

Before entering the magnetic field (B0), proton
magnetic moments are randomly oriented.
*Upon exposure to the B0 magnetic field, some
proton _ with it.**

Answer 5

Magnetic Alignment

Question 6

The alignment of proton magnetic moments creates _ in the patient. The Z-axis coincides with the axis of the static magnetic field (B0) in MRI systems.

Answer 6

Net Magnetization

Question 7

The strength of the B0 magnetic field is measured in?

Answer 7

tesla (T).

Question 8

There is no direct relationship between ___ and ___

Answer 8

magnetic field strength and ionizing radiation.

Question 9

Though only a fraction of proton dipoles align with the magnetic field, the patient becomes ____

Answer 9

polarized

Question 10

Polarized patients exhibits what?

Answer 10

north and south poles

Question 11

is a phenomenon observed
when a patient is placed
in a static magnetic field
during MRI.

Answer 11

Precession

Question 12

this phenomenon is crucial for
generating MRI signals used in imaging.

Answer 12

Precession

Question 13

Relating the strength of
the static magnetic field (B0) to the precessional frequency (f).

Answer 13

Larmor equation

Question 14

determines the precessional frequency and thus the resonance frequency in MRI.

Answer 14

Gyromagnetic Ratio

Question 15

___ is akin to the disintegration
constant in radioactive decay, unique to each nuclear species.

Answer 15

Gyromagnetic ratio

Question 16

The gyromagnetic ratio is expressed in ???

Answer 16

megahertz per tesla (MHz/T).

Question 17

has a gyromagnetic ratio
of approximately 42 MHz/T.

Answer 17

Hydrogen

Question 18

The Larmor frequency, also known as the ___

Answer 18

precessional frequency,

Question 19

is a crucial aspect of MRI, representing the emission of radio signals by the net magnetization in the patient.

Answer 19

Free Induction Decay (FID)

Question 20

represents the alignment of proton magnetic dipoles along the Z-axis after polarization in the static magnetic field (B0).

Answer 20

Net magnetization (MZ)

Question 21

___ emitted at the ___, is transmitted into the patient via an RF coil to induce energy transfer and initiate imaging.

Answer 21

RF pulse, Larmor frequency,

Question 22

is fundamental to MRI, analogous to the resonance of musical instruments or structural elements.

Answer 22

Resonance

Question 23

must match the resonant frequency of the precessing hydrogen nuclei for efficient energy transfer and imaging to occur.

Answer 23

RF or Radio Frequency Pulse

Question 24

When the RF signal is pulsed at resonance into the patient, the energy state of many protons is changed. The net magnetization, due to all of the protons, is said to “flip” toward the negative Z direction, while still precessing about the Z-axis

Answer 24

Phase Coherence

Question 25

This precession is always perpendicular to Z, in the XY plane, and if initially all of the spins are aligned along the same direction in the XY plane

Answer 25

Phase Coherence

Question 26

what relaxation times exist in MRI?

Answer 26

T1 and T2.

Question 27

T2 are also known as?

Answer 27

transverse relaxation time

Question 28

describes the decay of phase coherence and the FID signal over time.

Answer 28

T2 or transverse relaxation time

Question 29

describes the rate of the magnetization increasing back to equilibrium.

Answer 29

T1

Question 30

equilibrium magnetization state is also known as?

Answer 30

Normal State.