Transcript
Objectives At the end of session students will be able to:Define magnetDescribe magnetismExplain natural and artificial magnetIdentify Magnet field and magnet line of forceExplain theory of magnetism Discuses its application in Nursing
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.
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.
The ends of a magnet are where the magnetic effect is the strongest. These are called “poles.” Each magnet has2 poles – 1 north, 1 south.
Repulsion - Same pole
Attraction against PoleAttraction against Pole
If you cut a magnet If you cut a magnet in half,in half,
you get 2 magnets!you get 2 magnets!
S N S N S N
Magnetic FieldsMagnetic Fields
The region where the magnetic forcesThe region where the magnetic forcesact is called the “magnetic field”act is called the “magnetic field”
Shape of artificial magnet
The Earth is a magnet:The Earth is a magnet:It exerts magnetic forces and is surrounded by amagnetic field that is strongest near theNorth and South magnetic poles
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)
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.
Cont................Any unmagnetized material has the magnetic forces of its molecular magnets neutralized by adjacent molecular magnets, thereby eliminatingany magnetic effect.
A magnetized material will have most of itsmolecular magnets lined up so that thenorth pole of each molecule points in onedirection, and the south pole faces theopposite direction.
Cont……….
A material with its molecules thus alignedwill then have one effective north pole, andone effective south pole. where a steel baris magnetized by stroking.
• 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.
Domain TheoryDomain 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.
•
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.
• An atom with an atomic number of 26, such asiron, has 26 protons in the nucleus and 26revolving electrons orbiting its nucleus. If 13electrons are spinning in a clockwise directionand 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.
Domain Magnetic Theory ofElectron Spin
Application of Magnetism inNursing
Magnetic Resonance ImageAdvantages• Non-invasive• No ionizing radiation• Repeat studies present no problem
Disadvantages• Potential for accidents and even fatalities• Damage to equipment / cost
Safety issues
Static magnetic field
biological effectsmechanical effectsAuditory damage
Other issues
contrast agentscritically ill patients/resuscitationmonitoringclaustrophobia
Static magnetic field Measured in Gauss or Tesla (10,000G equivalent to 1T)
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 objectswhen brought into the field
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
• It is easy to forget objects, particularly whenresponding to an emergency!.
• Remember also – magnetic strips will be wiped (credit cards
Warnings to minimize accidents?
• OUTSIDE THE SCANNER ROOM• Signage• Barrier cords to scanner room• Restricted access - swipe card / coded entrySystemHealth Care Workers Should not remain in the
room when scanner is operational,
WARNING
“Contraindications” to CMR*
• Implants & metalCerebral aneurysm clips• Metallic foreign body inthe eye• Bullets (gun shot)• Ocular implants (containingmetal)• Swan-Ganz
• Electro Pacemakers
• Pacing wires• Cochlear implants• Hydrocephalus shunts mechanical
implants
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?
Nursing Responsibility: Safety Checklist
Important to knowPrevious heart surgery?• Asthmatic or allergies?• Tattoos or permanent eye liner (in relation
to contrast)
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
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.
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