This ppt is related to MRI safety and brief history of MRI

1. MRI SAFETY
Anupam Niraula

2. CONTAINS:
 Introduction
 Brief History
 Major Components
 Safety

3. Introduction:
 MRI stands for “Magnetic Resonance Imaging”.
 Originally know as “Nuclear Magnetic Resonance”(NMR)
 Used in medical field to produce image of internal
structures of living organism.

4. HISTORY:
Isidor Isaac Rabi an American physicist – First described NMR phenomenon in 1938.
A Swiss-American physicist Felix Bloch and an American physicist Edward Purcell
independently discovered the magnetic resonance phenomenon during the year (1946
AD)
In 1970 AD, another American physician and medical practitioner Raymond Vahan
Damadian used NMR for malignant tissues and found difference in NMR parameters.
Damadian and his team invented the first NMR scanner named as Indomitable in which
the first image of human body was acquired. The first person to undergo NMR was Larry
Minkoff who was an assistant of Damadian.
Paul Christian Lauterbur an American chemist and Sir Peter Mansfield an English
physicist were also working in the same field and were the persons responsible for
introducing MRI into the clinical set-up.

5. SIR PETER MANSFIELD
RAYMOND DAMADIAN
EDWARD PURCELL
FELIX BLOCH PAUL LAUTERBUR
ISIDOR ISAAC RABI

6. MAJOR COMPONENTS OF MRI:
BORE:
Magnet
Coils (gradient coils , RF coils , Shimming coils)
MRI table
Chelates
Console:
Computer hardware
Operating system

8. MAGNET:
A piece of iron or other material which has its component atoms so ordered that
the material exhibits properties of magnetism, such as attracting other iron-
containing objects or aligning itself in an external magnetic field.
Discovery: shepherd named Magnes, in an area of Northern Greece called
Magnesia, about 4,000 years ago.
Lodestones contain magnetite, a natural magnetic material Fe3O4. This type of
rock was subsequently named magnetite, after either Magnesia or Magnes himself.
The most significant difference between the magnetic field and the magnetic flux
is that the magnetic field is the region around the magnet where the moving
charge experiences a force, whereas the magnetic flux shows the quantity or
strength of magnetic lines produced by the magnet.
Magnetic flux density is measured in Tesla.
One Tesla = 10000 gauss

9. GUASS LINE

10. TYPES OF MAGNET:
Permanent Magnet – 0.064 T to 0.3 T
Resistive Magnet – up to 0.3 T
Super conductive Magnet- up to 12 T

11. SUPER CONDUCTIVE MAGNATE:
Utilize the property of Zero electrical resistance exhibited by certain
materials like (Niobium Titanium)
Loop of wire is surrounded with coolant, such as liquid Helium , liquid
nitrogen (cryogen), to reduce the electric resistance of the wire .
At 4 degree kelvin (-269 degree c) wire loses its resistance.
High current (760 A) at low voltage is required to convert them into
superconductive – Ramping
Super conductivity under low temperature was first observed by
Argentinean Alex Muller and German George Bednorz.

12. MRI SAFETY
a) MRI ZONES
b) FARADEY CAGE
c) PATIENT SAFETY
d) MAJOR ACCIDENTS
e) PREVENTATION OF ACCIDENT

15. SAFETY SIGN
IN ZONE 3

16. FARADAY CAGE :
A Faraday cage or Faraday shield is an enclosure used to block
electromagnetic fields. A Faraday shield may be formed by a continuous
covering of conductive material or in the case of a Faraday cage, by a
mesh of such materials.
Faraday cages come in all shapes and sizes, but all of them use a metal
screen that conducts electricity, creating a shielding effect.

17. HOW FARADAY CAGE WORKS?
Faraday cage distributes charge or radiation around the cage's exterior, it
cancels out electric charges or radiation within the cage's interior. In short, a
Faraday cage is a hollow conductor, in which the charge remains on the external
surface of the cage.

18. NOTE:
IN MRI FARADAY CAGE IS BUILD FOR RF SHIELDING
RF shielding is important because:
a) To prevent extraneous electromagnetic field (RF) from contaminating the MR signal.
a) To prevent electromagnetic radiation generated by MR machine from causing interference in
nearby medical devices.

19. The ideal room consist of nested components:
1)An outer shell for structural support
2) A middle metallic RF-shield
3)An interior layer made of finish materials.
The floor is generally made of monolithic copper covered
over with solid material.
Door must not allow any RF leakage, being shield by a set of
electrical contact strips or continuous metallic pneumatic
tube.
Window are laminated with blackened copper mesh between
two pieces of glass.
Virtually any metal can be used including aluminum and steel
but copper is generally used because it is more conductive
metal.

20. PATIENT SAFETY:
1)Informed consent
2)Patient history (medical history, claustrophobia)
3)Patient screening
4)Changing in hospital gown
5)Use of MRI compatible devices .

21. RF BURNS
RISK DUE TO METALLIC BODY IMPLANTS AND LOOSE METALLIC
BODIES

23. MRI ACCIDENT :
1st MRI accident occurred in New-York area hospital in 2001 July .
A six year old boy , Michael Colombini lost his life when the machine's
powerful magnetic field jerked a metal oxygen tank across the room,
crushing the child's head.
In India latest MRI accident that took a life of a person named Rajesh
Maru happened in 2018 in Nair hospital Mumbai.

24. MRI Machine At Lohiya Hospital Pulls UP
textile Min Satyadev Pachauri's guard’s
Pistol When He Came For MRI
Accident at Nair Hospital ,Mumbai
MISSILE EFFECT

26. WHAT TO DO IF ACCIDENT HAPPENS ?
a) Inform authority or higher level officer ASAP.
b) Switch off system and all electronic but remember switching system doesn't mean
magnate is off.
c) Find alternate of Quenching.
d) Do not quench machine in hurry unless its life threatening situation.
Ramp –down of machine is often done by service engineer. In a controlled manner,
current can be brought down from conductor to bring field zero. Ramping takes approx.
20 min for every 0.5 T.

27. QUENCH
A quench is an event that occurs only in superconducting magnates and
results in a loss of magnetic field of the MRI magnet.
It is caused by a loss of superconductivity , a rapid increase in the
resistivity of the magnet coil windings, which generates heat that results in
rapid evaporation, or boil-off of the magnet coolant.
There are two situation in which quench may occur:
a) Spontaneously due to some force or disruption to the magnate
system.
b) The emergency “Magnet Stop” button is pressed during emergency
situation.

28. EMERGENCY STOP BUTTON:
Emergency Magnet Rundown Unit: This initiates a
controlled quench and turns off the magnetic field.
It is typically a big red button located on the wall
of the magnet room near the door.
This button should only be used in a life threating
situation.
Pressing this button makes the scanner out of
service costing heavily for replacing lost liquid
helium.

29. Emergency shutdown : Does not quench the
magnet but turns off most electrical power in the
scanner room and operator area, including the
console ,computers , patient table , ups etc.
It may be simple red button labeled or unlabeled
This switch should b used when there is serious
equipment fault or hazard ,such as fire , water in the
vicinity of the MR scanner

31. PREVENTATION OF ACCIDENT
PATIENT MUST BE SCREENED THROUGH METAL
DETECTOR
OR PASS THROUGH GATE BEFORE ENTERING 4TH
ZONE
INFORMED CONSENT SHOULD BE TAKEN REGARDING HISTORY
OF ANY PREVIOUS SURGERY AND METALLIC IMPLANTS
WARNING SIGNS SHOULD BE PLACED ON 3RD ZONE
DISPLAYING THE RESTRICTED ITEMS THAT CAN’T BE
TAKEN INSIDE MRI ROOM

32. “MRI CAN BE ACCIDENT PRONE FOLLOW RULES OF SAFETY ZONE”
“MRI CAN TURN INTO MONSTER ,IT IS IN OUR HAND TO STOP
DISASTER”