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Z MRI Physics > Module 1 > Flashcards

Module 1 Flashcards

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1
Q

—Felix Bloch

A

Godfather of MRI

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2
Q

—Images are created using 3 regions of the electromagnetic spectrum.

A

—X-rays use transmitted x-rays

—Photographs use reflected visible light.

MRI uses emitted radiofrequencies

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3
Q

—Non-ionizing radiation.

—Spatial resolution (the ability to distinguish two points or structures as separate)

—Contrast resolution

—Multiplanar Imaging

Sensativity-the ability to detect subtle differences in tissue

A

MRI advantages

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4
Q

is a test that uses a magnetic field and pulses of radio wave energy to make pictures of organs and structures inside the body

A

What is MRI

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5
Q

in a patients tissues behave like tiny magnets themselves and are susceptible to an external magnetic field due to its magnetic moment

A

hydrogen nuclei

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6
Q

Consists of central nucleus with one proton no neutron and one orbiting electrons

A

Hydrogen Atom

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7
Q
  1. Electrons spinning on own axis
  2. Electrons orbiting the Nucleus
  3. The Nucleus itself spins on own axis
A

3 Types of Motion within the Hydrogen Atom

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8
Q

sum of Protons in Nucleus

A

Atomic Number

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9
Q

sum of Protons and Neutrons in the nucleus

A

Atomic Mass

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10
Q

refers to three inividual forces, motion, magnetism and electrical charge. If two of the three are present then the third will be induced

A

Faraday’s law of electromagnetic induction

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11
Q

hydrogen we have a positive charge and motion

A

the third force magnetism will be induced thus giving the hydrogen atom a magnetic moment allowing in to align with an external magnetic field.

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12
Q

Hydrogen Atom Nucleus is rotating around its axis and the Proton or charged particle is also rotating >

A

This causes the Hydrogen atom to contain its own Magnetic Field

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13
Q

due to its odd number of Protons (one) in its nucleus. (hydrogen atom)

A

Magnetic Moment that is relatively large

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14
Q

2 energy states with the Hydrogen nuclei

A

Low State

High State

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15
Q

align with the External Magnetic Field, termed Spin Up Nuclei.

A

Low energy state

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16
Q

align against the External Magnetic Field, termed Spin Down Nuclei.

A

high energy state

17
Q

It takes less energy to

A

line up with the Magnetic Field

18
Q

It takes more energy to

A

fight against the direction of the Main Magnetic

Field.

19
Q

direction of the North and South axis of a Magnet and the amplitude of the magnetic field

A

magnetic moment

20
Q

The larger the field strength, the ________hydrogen will align in the spin up (low energy) state

A

more

21
Q

Size and Direction of the magnetic moment in the Z plane.

has both magnitude and direction

A

Vector

22
Q

With no external magnet field magnetic moments are randomly situated

Once exposed to a Magnet Field M. M. start to_______with and against Magnetic field (North and South)

A

alignment

23
Q

Battle between Spin Up and Spin Down Nuclei create a common ground. The result of this battle is the

A

N.M.V. w0

Net Magnetization Vector

24
Q

These are the winners or the remaining Vectors that now align with the external field…

These are what will be manipulated by the external R.F. pulse to create M.R.I images.

A

Net Magnetization Vectors

25
Q

Hydrogen Nuclei spin on there own axis.

Once subjected to an External Magnetic Field they also start to wobble

A

This wobble is called its Precession

26
Q

More powerful the External Magnetic Field

A

the more N.M.V. there are to manipulate

27
Q

3T images have _______ signal than 1.5T.

A

higher

28
Q

Speed at which the Hydrogen Atoms spin we also call this wobble

A

Precessional Frequency:

29
Q

Path by which the Hydrogen Atoms follow.

A

Precessional Path:

30
Q

Determines the Precessional Frequency

A

Larmor equation:

31
Q

equal to the gyromagnetic Ratio of Hydrogen (42.57MHZ/Tesla) Times the Magnetic Field Strength

A

The Precessional Frequency /

32
Q

The field strength of the magnet is displayed

A

in tesla represented as T

or Bo

33
Q

The gyromagetic ratio is represented by

A

Greek gamma symbol

34
Q

Precessional Frequency is represented

A

as f or Wo

35
Q

42.57 MHZ/T

A

larmar equation ratio

36
Q

Expensive

Long scan times

Audible noise (65-115dB or higher)

Isolation of patient (claustrophobia, monitoring of ill patients)

Exclusion of patients with conventional pacemakers and certain implants.

A

Disadvantage of MRI

Z MRI Physics (12 decks)

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