this ppt is about mri equipments

1. MAAJID MOHI UD DIN MALIK
LECTURER COPMS,
AU BATHINDA PUNJAB
MRI EQUIPMENTS

2. MRI machines vary in both size and shape. The
older designs had a more compact and small
space and were very closed. This affected the
patients mentally and usually scared them
even before they went in for the examination.
However, the engineers have tried to solve this
problem by improving the machine to be more
open and inviting. They have expanded the
sides and included much more space in
the scanner than the original models.

3. The basic design of a Magnetic Resonance
Imaging scanner is the same in almost all
machines. The scanner consists of a 24
inch wide tube, inside which the examination takes
place. It also contains:
A magnet,
Radio Frequency (RF) coil,
Gradient coils
Patient table, and
Computer system.

5. MAGNET
The magnet is the most important and biggest part of the MRI
device. It is this magnet that allows the MRI machine to
produce high quality images. There is a horizontal tube that
runs through the magnet and is called a bore. The magnet is
extremely powerful and its strength is measured in either
‟teslaˮ or ‟gaussˮ (1 tesla = 10 000 gauss). Most MRI magnets
use a magnetic field of 0.5 to 2.0 tesla, when the Earth’s
magnetic field is only 0.5 gauss. The magnetic field
is produced by passing current through multiple coils that
are inside the magnet, resulting in a state of
superconductivity, which produces a lot of energy by reducing
the resistance in the wires to zero.

7. GRADIENT COILS
There are three different gradient coils that are
inside the MRI machine and are located within
the main magnet. Each one of these produce
three different magnetic fields that are each
less strong than the main field. The gradient
coils create a variable field (x, y, z) that can be
increased or decreased to allow specific and
different parts of the body to be scanned by
altering and adjusting the main magnetic field.

9. RADIO FREQUENCY (RF) COILS
The basic function of the RF coils is to transmit
radio frequency waves into the patient’s body.
There are different coils located inside the MRI
scanner to transmit waves into different body
parts. If a certain area of the body is specified,
then all the RF coils usually become focused
on the body part being imaged to allow for a
better scan.

11. PATIENT TABLE
This component simply slides the patient into
the MRI machine. The position at which
the patient lies down on the table is determined
by the part of the body that is being scanned.
Once the part of the body under examination is
in the exact center of the magnetic field, which
is referred to as the isocentre, the scanning
process is started.

12. ANTENNA/COMPUTER SYSTEM
The antenna is a very sensitive device that easily
detects the RF signals emitted by a patient’s body
while undergoing examination and feeds this
information into the computer system. The computer
system is a powerful system, whose major function is
to receive, record, and analyze the images of the
patient’s body that have been scanned. It interprets
the data sent in by the antenna and then, helps to
produce an understandable image of the body part
being examined.

14. MRI SAFETY
S = Search for Hazards
A = Analyze the Risk
F = Find the Cause
E = Eliminate the Cause
T = Tell Others
Y = You are Safe

15. MRI : IMAGING PRINCIPLE
 Pt. is placed in magnet
 Radio wave is sent in
 Radio wave is turned off
 Pt. emits a signal
 Signal is received & used
for reconstruction of the
picture.

16. MRI ENVIRONMENT
MRI unit should be designed to restrict access
for unrelated persons.
A number of guidelines all over the world to
restrict the access in MRI.
But all have same objective to ensure safe MRI
environment every time.
One widely accepted approach is a 4 zone design
recommended by ACR.

17. MRI ENVIRONMENT

18. SAFETY ISSUES: HISTORY
Used clinically since mid 1980
No known biological effects associated
with Bo of MRI, a no. of accidents have
occurred in MRI environment.
In 2001 a tragedy occurred when a 6yr
child was killed.

20. SAFETY ISSUES: HISTORY
 Blue Ribbon Panel of MRI Experts by ACR to produce
guidelines for MRI safety.
 In 2oo2, “white paper” was published & intended to
provide guidelines for imaging facilities for development
& implementation of safety policies & procedure.
 Since then it has been revised, rebutted & updated
periodically.

21. SAFETY ISSUES & RISK IN MRI
What are the safety concerns?
&
How can MRI be dangerous?

22. SAFETY ISSUES & RISK IN MRI
1. Static magnetic field:
• (Missile effect: devices, implants & projectiles)
2. RF magnetic field:
• (tissue heating, & thermal injuries)
3. The gradient magnetic field:
• (PNS, magneto- phosphine's & acousticnoise)
4. MRI contrast agent

23. STATIC MAGNETIC FIELD
 Projectile or Missile Effect:
 Translational and rotational attractive
forces on ferrous metallic objects
 Ferrous metallic objects are drawn to
magnetic bore & can be easily pulled out
of hands, pockets etc.
 This effect has caused several injuries &
death

24. EXAMPLES: PROJECTILE EFFECT

26.  June 03, 2017, at Dr.
Ram Manohar Lohia
Institute of Medical
Sciences in Lucknow,
Uttar Pradesh, :
Minister’s guard carries
gun during MRI scan
 his pistol was pulled
from his body and got
stuck on the machine.
 According to reports,
the cost for repairing
machine was around Rs
40-50 lakh.

27. POTENTIAL PROJECTILES

28. RF MAGNETIC FIELD:
 Heating of tissue: some tissues nuclei absorb RF energy &
enter higher energy state (less concern < 1T MR system).
 Thermal injuries:
 When conducting materials (e.g. cable of surface coil, ECG
lead), are placed within the RF field, current is produce in
conductive loop.
 The concentration of electric current can cause excessive
heating that causes tissue burns.
 Tissue burn is the most frequently reported adverse incident.

29. RF MAGNETIC FIELD RELATED BURN

30. RF MAGNETIC FIELD RELATED BURN

31. RF MAGNETIC FIELD RELATED BURN
 Cloth containing anti-microbial solution or metal
infused material can heat & cause burn.
 Medication patches & skin patches may have metallic
components that can also heat & cause burns.

32. “A patient with an implanted intracranial
aneurysm clip died as a result of an attempt to
scan her”

33. WHILE PREPARING PT FOR MRI
Always Remember………………
 Screen
 Change
 Explain

34. THANK YOU