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MRI Registry Exam > Chapter 1: Basic Principles > Flashcards

Chapter 1: Basic Principles Flashcards

1
Q

There are essentially 2 ways of explaining the fundamentals of MRI. What are these 2 ways?

A

Classical theory and Quantum theory.

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2
Q

What is the most abundant atom in the human body?

A

Hydrogen

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3
Q

In what 2 ways are atoms characterized?

A

Atomic number
Mass number/atomic weight

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4
Q

What is the sum of the protons in the nucleus called?

A

Atomic number

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5
Q

What is the sum of the protons and neutrons in the nucleus?

A

Mass number/atomic weight

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6
Q

Atoms of elements with the same number of protons but a different number of neutrons are called?

A

Isotopes

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7
Q

What 3 types of motion are present within the atom?

A

Electrons spinning on their own axis
Electrons orbiting the nucleus
The nucleus itself spinning about its own axis.

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8
Q

Nuclei need an odd number of protons, neutrons, or an odd number of both protons and neutrons, so that the spin directions are not equal and opposite, so the nucleus itself will have a net spin. What is this called?

A

Angular momentum

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9
Q

In MRI, in general, only nuclei with an odd mass number or atomic weight are used. These are known as what?

A

MR-active nuclei

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10
Q

What is the isotope of hydrogen called?

A

Protium

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11
Q

What is the most commonly used MR-active nucleus in MRI?

A

Hydrogen (Protium)

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12
Q

What states that a magnetic field is created by a charged moving particle (that creates an electric field)?

A

Faraday’s Law of electomagnetic induction.

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13
Q

In the absence of an applied magnetic field, the magnetic moments of hydrogen nuclei are what?

A

Randomly oriented and produce no overall magnetic effect.

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14
Q

Which theory used the direction of the magnetic moments of spins to illustrate alignment?

A

Classical theory

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15
Q

Which theory uses the energy level of the spins to illustrate alignment?

A

Quantum theory

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16
Q

Protons of hydrogen nuclei couple with the external magnetic field. What is this referred to as?

A

Zeeman Interaction

17
Q

What equation predicts the number of spins in each energy level?

A

Boltzmann equation

18
Q

Boltzmann’s equation also shows that the _________ is an important factor that determines whether a spin is in the high or low energy population.

A

Patient’s temperature

19
Q

What reflects the relative balance between spin-up and spin-down nuclei? What is this termed as?

A

NMV

20
Q

According to _________, there are about 6 x 10^23 molecules per gram of tissue, and the number of excess spins is in the order of 6 x 10^17 per gram of tissue.

A

Avogadro’s Law

21
Q

In a 1.5 T scanner, what is the number of excess spins?

A

4.5 for every million protons

22
Q

The precessional frequency is often call what?

A

Larmor frequency

23
Q

1 megahertz is how many cycles or rotations per second?

A

1 million

24
Q

______ expresses the relationship between angular momentum and the magnetic moment of each MR-active nucleus.

A

Gyromagnetic ratio

25
Q

What is the gyromagnetic ratio of hydrogen at 1T?

A

42.58 MHz/T

26
Q

When the only influence is Bo, what happens to the magnetic moments?

A

They are out of phase with each other, and therefore the NMV does not precess.

27
Q

________ refers to the position of magnetic moments on their precessional path at any moment in time.

A

Phase

28
Q

What is the unit of phase?

A

Radian

29
Q

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

A

Resonance

30
Q

How is resonance achieved?

A

By transmitting an RF pulse at the Larmor frequency. This is called an RF excitation pulse.

31
Q

The transition that the magnetic moments have in precessing at the higher rate in the longitudinal plane to decreasing the NMV into the transverse plane creates a spiraling motion downward of the NMV. This spiraling down is called what?

A

Nutation

32
Q

In what 2 ways is the RF excitation pulse characterized by?

A

It’s amplitude and it’s frequency

33
Q

What is defined as the energy available from a unit of charge traveling once around a loop of wire?

A

Electromotive Force (emf)

34
Q

According to Faraday’s Law, a changing magnetic field causes movement of charged particles (electrons). This flow of electrons is a current, which generates a voltage induced in the receiver coil. This voltage is called?

A

Signal

35
Q

The process by which hydrogen loses its energy is called?

A

Relaxation

36
Q

What is the time from the application of one RF pulse to the application of the next RF pulse for each slice and is measured in milliseconds?

A

TR

37
Q

What is the time from the application of the RF pulse to the peak of signal induced in the receiver coil and is also measured in milliseconds?

A

TE

38
Q

What determines the amount of T1 relaxation that has occured when the signal is read?

A

TR

39
Q

What controls the amount of T2 relaxation that has occured when the signal is read?

A

TE

MRI Registry Exam (6 decks)

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