Quiz 1- Lecture 2: Structural Imaging MRI Basics

Question 1

The human body contains around ___ different elements.

Answer 1

20

Question 2

Elements in the human body:

Answer 2

Oxygen (65%)
Carbon (18%)
Hydrogen (9.5%)
Nitrogen (3.2%)
Calcium (1.5%)
Phosphorus (1.2%)
Potassium (0.4%)
Sulfur (0.2%)
Sodium (0.2%)
Chlorine (0.2%)
Magnesium (0.1%)

Question 3

Others listed in the diagram of the human body:

Answer 3

Water (62%)
Protein (16%)
Minerals (6%)
Carbohydrate (1%)
Fat (16%)

Question 4

What are atoms?

Answer 4

Extremely small particles that are the basic building blocks of ordinary matter

Question 5

Atoms can join together to form ____, which make up most objects

Answer 5

Molecules

Question 6

What do atoms consist of?

Answer 6

An extremely small, positively charged nucleus surrounded by a cloud of negatively charged electrons

Question 7

Although the nucleus is less than one tenth-thousandth the size of the atom,

Answer 7

the nucleus contains more than 99.9% of the mass of the atom

Question 8

What are nuclei made of?

Answer 8

Positively charged protons and electrically neutral neutrons held together by a nuclear force

Question 9

The nuclear force is much stronger than the electrostatic force that binds electrons to the nucleus, but it’s

Answer 9

Range is limited to distances of the rose of 1x10^-15 meters

Question 10

What are isotopes?

Answer 10

Atoms of the same element that have different number of NEUTRONS

Question 11

What are hydrogen’s isotopes (3)?

Answer 11

Hydrogen-1 (hydrogen)
Hydrogen-2 (deuterium)
Hydrogen-3 (tritium)

Question 12

How did Lauterbur contribute to MRI?

Answer 12

By introducing variations in the magnetic field during the 1970s

Question 13

How did Mansfield contribute to MRI?

Answer 13

By developing calculation methods during the 1970s

Question 14

What 2 things provide a basis for magnetic resonance imaging (MRI)?

Answer 14

The incidence of hydrogen atoms is measured, Differences in the water content of different tissues

Question 15

What does MRI use to produce detailed images from any part of the body?

Answer 15

The body’s natural magnetic properties

Question 16

What is used for MRI’s imaging purposes and why?

Answer 16

Hydrogen nucleus (a single proton); abundance in water and fat

Question 17

The hydrogen proton is like planet Earth spinning on its axis with a north-south pole. In this respect, it

Answer 17

Behaves like a small bar magnet

Question 18

What happens to hydrogen protons under normal circumstances? How can they be influenced?

Answer 18

These “bar magnets” spin in the body with their axes randomly aligned; They can be influenced by a strong magnetic field

Question 19

What happens to protons when the body is placed in a strong magnetic field like an MRI scanner?

What does this uniform alignment create?

Answer 19

The protons’ axes all line up

A magnetic vector oriented along the axis of the MRI scanner

Question 20

What are the different field strengths of MRI scanners?

Answer 20

Usually between 0.5 and 1.5 tesla

Question 21

What is the main magnetic field termed in MRI?

How is it aligned?

Answer 21

B 0

Aligned in the direction of B0 (parallel), Aligned in the opposite direction of B0 (anti parallel)

Question 22

A parallel and anti parallel hydrogen nuclei…

HOWEVER

What is this termed? What symbol is it given?

Answer 22

Have equal but opposite magnetic moments and cancel each other out

However, there are always slightly more hydrogen nuclei parallel to B0.
This is termed the NMV (Net Magnetization Vector). It’s given the symbol “M.”

Question 23

What is precession?

Answer 23

Nuclear spin; the rotation of the spins

Question 24

What creates signal in MRI?

Answer 24

The precession is part of the MRI phenomenon and creates signal

Question 25

Larmor Equations:f0=yB0

What is f0?
What is y?
What is B0?

Answer 25

f0 means “Precession frequency”
y means “gyromagnetic ratio (specific to each specific nucleus or element)”
B0 means “strength of the applied magnetic field”

Question 26

Radio frequency (RF): Pulses (90 degrees and 180 degrees)
What is the purpose of applying RF magnetic fields?

What does the RF energy aim to do?

Answer 26

To excite the spins

Flip the net magnetization

Question 27

What is the RF energy referred to as? Why?

Answer 27

RF pulse; Since the RF energy is applied for a short period of time and then switched off

Question 28

What occurs exponentially?

Answer 28

The recovery of the longitudinal magnetization of a proton

Question 29

What is called the T1 time?

Answer 29

The point at which 63% of the longitudinal magnetization has been recovered

Question 30

What is called the T2 time?

Answer 30

The time at which 63% of the transverse magnetization has been lost

Question 31

What are the T1 and T2 times unique to?

Answer 31

Each tissue type

Question 32

What is an MR examination made up of?

Answer 32

A series of pulse sequences

Question 33

How are different tissues identifies separately in T1 and T2?

Answer 33

Different tissues (like fat and water) have different relaxation times

Question 34

T1 Weighted:
CSF
White Matter
Cortex
Fat (within bone marrow)
Inflammation (infection, demyelination)

Answer 34

CSF - DARK
White Matter - LIGHT
Cortex - GRAY
Fat (within bone marrow) - BRIGHT
Inflammation (infection, demyelination) - DARK

Question 35

T2 Weighted:
CSF
White Matter
Cortex
Fat (within bone marrow)
Inflammation (infection, demyelination)

Answer 35

CSF - BRIGHT
White Matter - DARK GREY
Cortex - LIGHT GREY
Fat (within bone marrow) - LIGHT
Inflammation (infection, demyelination) - BRIGHT

Question 36

Are there any known biological hazards of MRI?
Which types do have biological hazards?

Answer 36

No; X-ray and Computed tomography (CT)

Question 37

MRI uses what kind of radiation?

Answer 37

MRI uses radiation in the radiofrequency range which is found all around us and it does not damage tissue as it passes through

Question 38

What can be dangerous in MRI scanners? Why?

Answer 38

Pacemakers, metal clips, and metal valves
Because of potential movement within a magnetic field

(Metal joint prostheses are less of a problem, but there may be some distortion of the image close to the metal)
MRI departments always check for implanted metal and can advise on their safety