2. Objectives
At the end of session students will be able to:
Define magnet
Describe magnetism
Explain natural and artificial magnet
Identify Magnet field and magnet line of
force
Explain theory of magnetism
Discuses its application in Nursing
3. Magnet
• A body, as a piece of iron, that possesses
the property of attracting certain substances,
iron, nickel and cobalt.
Unit = The tesla (symbol T)
• One tesla is equal to 10,000 Gauss.
4. What is Magnetism?What is Magnetism?
Magnetism is the
force of
attraction or
repulsion of a
magnetic
material due to
the arrangement
of its atoms,
particularly its
electrons.
5. The ends of a magnet are
where the magnetic effect
is the
strongest. These are
called “poles.” Each
magnet has
2 poles – 1 north, 1 south.
15. The Earth is a magnet:The Earth is a magnet:
It exerts magnetic
forces and is
surrounded by a
magnetic field
that is strongest
near the
North and South
magnetic poles
16. We use the Earth’s magnetic field
to find direction.
The needle of a compass always points
toward the magnetic south pole.
We call this direction “North”
(remember, opposites attract)
17. THEORIES OF MAGNETISM
Weber's Theory
A popular theory of magnetism considers the
molecular alignment of the material. This is known
as Weber's theory. This theory assumes that all
magnetic substances are composed of tiny molecular
magnets.
18. Cont................
Any unmagnetized material has the magnetic
forces of its molecular magnets neutralized by
adjacent molecular magnets, thereby eliminating
any magnetic effect.
A magnetized material will have most of its
molecular magnets lined up so that the
north pole of each molecule points in one
direction, and the south pole faces the
opposite direction.
19. Cont……….
A material with its molecules thus aligned
will then have one effective north pole, and
one effective south pole. where a steel bar
is magnetized by stroking.
20. • When a steel bar is stroked several
times in the same direction by a
magnet, the magnetic force from the
north pole of the magnet causes the
molecules to align themselves.
21. Domain Theory
Domain Theory•
A more modern theory of magnetism is based
on the electron spin principle. From the study of
atomic structure it is known that all matter is
composed of vast quantities of atoms, each atom
containing one or more orbital electrons.The
electrons are considered to orbit in various
shells and sub shells depending upon their
distance from the nucleus
.
22. •
effectiveness of the magnetic field of an atom is
determined by the number of electrons spinning in
each direction. If an atom has equal numbers of
electrons spinning in opposite directions, the
magnetic fields surrounding the electrons cancel
one another, and the atom is unmagnetized.
However, if more electrons spin in one direction
than another, the atom is magnetized. It has been
experimentally proven that an electron has a
magnetic field about it along with an electric field.
23. • An atom with an atomic number of 26, such as
iron, has 26 protons in the nucleus and 26
revolving electrons orbiting its nucleus. If 13
electrons are spinning in a clockwise direction
and 13 electrons are spinning in a
ounterclockwise direction, the opposing magnetic
fields will be neutralized. When more than 13
electrons spin in either direction, the atom is
magnetized.
26. Magnetic Resonance Image
Advantages
• Non-invasive
• No ionizing radiation
• Repeat studies present no problem
Disadvantages
• Potential for accidents and even fatalities
• Damage to equipment / cost
27. Safety issues
Static magnetic field
biological effects
mechanical effects
Auditory damage
Other issues
contrast agents
critically ill patients/resuscitation
monitoring
claustrophobia
29. Static Magnetic Fields
•1. Biological effects (potential risk)
- Exposure to static magnetic fields of up to 4T
are not thought to be harmful
- Distorted ECG (magnetohydrodynamic efect)
- Be careful with pregnancy.
2. Mechanical effects (very real risk)
- translational or attractive forces on metallic
objects
when brought into the field
30. What is typically ferromagnetic?
EQUIPMENT AND PERSONAL ITEMS
(leave outside)
Oxygen cylinders Keys, pens
• Wheelchairs Bleeps (page, buzz, etc.)
• Trolleys Mobile phones
• IV stands Coins
• Monitoring equipment Stethoscopes
• Ventilators Scissors
31. • It is easy to forget objects, particularly
whenresponding to an emergency!.
• Remember also – magnetic strips will be
wiped (credit cards
32. Warnings to minimize accidents?
• OUTSIDE THE SCANNER ROOM
• Signage
• Barrier cords to scanner room
• Restricted access - swipe card / coded entry
System
Health Care Workers Should not remain in the
room when scanner is operational,
36. Nursing Responsibility: Safety Checklist
Nurses need to assess the patient on the following
checklist
Essential to know
• • Cardiac pacemaker?
• • Previous neurosurgery?
• • Implants or metal in the body?
• • Pregnant (prudent approach)?
• • Drug patch with foil backing?
37. Nursing Responsibility: Safety Checklist
Important to know
Previous heart surgery?
• Asthmatic or allergies?
• Tattoos or permanent eye liner (in relation
to contrast)
38. Cont...................
Essential preparation
• Removal of accessories - watch, jewellery
hearing aids,
glasses, false teeth, artificial limbs and
prostheses
• Removal of clothes containing metal eg zips
• Educating patient having invasive devices is
important
39. References
• Hurlbut, Cornelius Searle; W. Edwin Sharp,
Edward Salisbury Dana (1998). Dana's
minerals and how to study them. John
Wiley and Sons. p. 96. ISBN 0-471-15677-
9. Bowles, J. F. W.; R. A. Howie, D. J.
Vaughan, J. Zussman (2011). Rock-forming
Minerals: Non-silicates: oxides, hydroxides
and sulphides, Volume 5A, 2nd Ed.. UK:
Geological Society of London. p. 403.
