Ch. 1 Basic Principles

Question 1

The most abundant atom in the body is…

Answer 1

hydrogen

Question 2

The sum of the protons in the nucleus.

Answer 2

atomic number

Question 3

The sum of the protons and neutrons in the nucleus.

Answer 3

mass number

Question 4

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

Answer 4

isotopes

Question 5

Electrons are particles that spin around the…

Answer 5

nucleus

Question 6

There are 3 types of motion present within the atom.

Answer 6

1. electrons spinning on their own axis
2. electrons orbiting the nucleus
3. the nucleus itself spinning about its own axis

Question 7

The principles of MRI rely on the spinning motion of…

Answer 7

specific nuclei present in biological tissues.

Question 8

Nuclei with odd mass numbers, i.e where the # of neutrons is slightly more or less than the number of protons, spin directions are not equal and opposite, so the nucleus itself has a net spin or________. These are known as what?

Answer 8

Angular Momentum

MR active nuclei

Question 9

The law of Electromagnetic Induction refers to which three individual forces. (Faradays Law)

Answer 9

1. motion
2. magnetism
3. charge

Question 10

If two of the 3 forces of Faradays Law are present then the third is____

Answer 10

automatically induced

Question 11

The isotope of the hydrogen nucleus is called? and is the MR active nucleus used in clinical MRI.

Answer 11

Protium

Question 12

This describes the properties of electromagnetic radiation in terms of discrete quantities of energy called quanta.

Answer 12

quantum physics

Question 13

Applying quantum theory to MRI, hydrogen nuclei posses energy in two discrete quantities or populations termed what?

Answer 13

Low and High

Question 14

Low energy nuclei align their magnetic moments _____ to the external field and is termed______.

Answer 14

Parallel

spin-up nuclei

Question 15

High energy nuclei align their magnetic moments ___ ____ _____ and are termed_____

Answer 15

anti-parallel direction

spin down nuclei

Question 16

The factors affecting which hydrogen nuclei align parallel and which align anti-parallel are determined by what?

Answer 16

1. the strength of the external magnetic field

2. the thermal energy level of the nuclei

Question 17

This determines the relative quantities of spin-up and spin-down nuclei.

Answer 17

The strength of the external field.

Question 18

In thermal equilibrium, there are always ____ high energy nuclei than low energy nuclei, therefore the magnetic moments of the nuclei aligned parallel to the magnetic field cancel out the smaller number of magnetic moments aligned anti-parallel.

Answer 18

Fewer

Question 19

The net magnetic moment of hydrogen produces a significant magnetic vector that is used in clinical MRI and thisreflects the balance between spin-up and spin-down nuclei. This is called?

Answer 19

Net Magnetization Vector (NMV)

Question 20

The static external magnetic field is called?

Answer 20

Bo

Question 21

The interaction of the NMV with the Bo is the…

Answer 21

Basis of MRI

Question 22

The unit of Bo is?

Answer 22

Tesla or gauss.

Question 23

1 Tesla (T) is the equivalent of ____ gauss (G)

Answer 23

10,000 G

Question 24

The secondary spin is called?

Answer 24

precession

Question 25

Precession causes the magnetic moments to follow a circular path around what? and is called what?

Answer 25

Bo | Precessional path

Question 26

The speed at which the hydrogen nucleus wobble around Bo is called?

Answer 26

Precessional frequency

Question 27

The unit of precessional frequency is called?

Answer 27

Megahertz (MHz)

Question 28

1 Hz is one cycle or rotation per second and 1 MHz is?

Answer 28

one million cycles or rotations per second

Question 29

The value of the precessional frequency is governed by?

Answer 29

The Larmor equation

Question 30

The Larmor equation states that?

Answer 30

wo=Bo x /| wo= the precessional frequency Bo=the magnetic field strength /|= the gyromagnetic ratio.

Question 31

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

Answer 31

The gyromagnetic ratio.

Question 32

What is the gyromagnetic ratio of hydrogen?

Answer 32

42.57 MHz/T

Question 33

At 1.5T the precessional frequency of hydrogen is? 1.0T? .5T?

Answer 33

63. 86 MHz 42. 57 MHz 21. 28 MHz

Question 34

This 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?

Answer 34

resonance

Question 35

When a nucleus us exposed to an external perturbation that has an oscillation similar to its own natural frequency, then the nucleus does what?

Answer 35

Gains energy from the external force if the energy is delivered at the exact same precessional frequency.

Question 36

Energy at the precessional frequency of hydrogen at all field strengths in clinical MRI corresponds to the?

Answer 36

radio frequency (RF) band of the electromagnetic spectrum

Question 37

For resonance of hydrogen to occur, and RF pose at exactly the ____ of hydrogen must be applied.

Answer 37

Larmor frequency

Question 38

The application of an RF pulse that causes resonance to occur is termed ______.

Answer 38

excitation