Project on HOW MRI SCAN WORKS

1. HOW MRI SCAN WORKS ?
AFNAAN QURESHI
XII – A
LITTLE FAIRY PUBLIC SCHOOL

2. -------------------------INDEX-------------------------
• Certificate-----------------------------------------------------------------------------------------------------------------------------
• Acknowledgement---------------------------------------------------------------------------------------------------------------------
• History----------------------------------------------------------------------------------------------------------------------------------
• Introduction-----------------------------------------------------------------------------------------------------------------------------
• Hydrogen atoms-----------------------------------------------------------------------------------------------------------------------
• MRI component------------------------------------------------------------------------------------------------------------------------
• Primary magnet-----------------------------------------------------------------------------------------------------------------------
• Gradient magnet----------------------------------------------------------------------------------------------------------------------
• RF coils---------------------------------------------------------------------------------------------------------------------------------
• Relaxation-----------------------------------------------------------------------------------------------------------------------------
• Net magnetic vector------------------------------------------------------------------------------------------------------------------
• RF reception---------------------------------------------------------------------------------------------------------------------------
• Computer system---------------------------------------------------------------------------------------------------------------------
• Biblography--------------------------------------------------------------------------------------------------------------------------

3. CERTIFICATE
This is to certify that AFNAAN QURESHI of class XII – A has made this project
titled ‘HOW MRI SCAN WORKS ?’ under the supervision and guidance of Mrs.
SUNITA MAAM. The work speaks about sincere efforts of the studen t and thinks
it quite satisfactory and should be accepted.
Internal examiner sign. External examiner sign.
___________________ ____________________

4. ACKNOWLEDGEMENT
I would like to express my special thanks of gratitude to my teacher Mrs.
SUNITA MAAM as well as our principal Mrs. MEENAKSHI KHURANA MAAM who
gave me this golden opportunity to do this wonderful project on the topic
“HOW MRI SCAN WORKS ?” which also help me in doing a lot of research and
i came to know about so many new things about so many new things I am really
thankfull to them.
Secondly i would also like to thank my parents and friends who helped me a lot
in finalising this project within the limited time frame.
It was a great pleasure while making such an interesting project.

5. HISTORY
• MRI scaning was discovered by 2 physicist in 1947:-
1. Felix Bloch
2. Edward Mill Purcell Felix Bloch E. M. Purcell
• MRI machine was invented by Dr. Raymond Damadian
• First clinical images were obtained in 1977.
Dr. Raymond Damadian

6. INTRODUCTION
• MRI stands for Magnetic Resonance Imaging
• MRI uses magnetic field and radiofrequencies rather than ionising
radiation used in X-rays and CT (Compute Tonography) scan.
• Magnetic field produced in MRI scan is measured in tesla (T).
• Clinical MRIis performed at 1.5 – 3T.
• This produces an extreme strong magnetic field upto 50,000 times of
earth’s magnetic field (earth’s magnetic field = 0.00003T).
• This magnetic field is that much strong which
is enough to pick up the car

7. HYDROGEN ATOM
• Body is made up of 70% of water which is composed of
hydrogen and oxygen atoms.
• MRI scan is dependent on magnetic properties of hydrogen
atom to produces images.
• Hydrogen nucleas is composed of a single proton with no
neutrons.
• This proton act as a spinning charged particle which
produces a magnetic field which is known as magnetic
moment.
• Normally, this proton is randomly oriented so they cancel
each other’s effect of thier magnetic field due to which a
net magnetic field is 0

8. MRI COMPONENTS
There are four component of MRI
1. Primary magnet
2. Gradient magnet
3. Radiofrequency (RF) coils
4. Computer system

9. PRIMARY MAGNET
• It is refers to the strength of static permanent magnetic field. For eg:- 1.5 – 3T
• It consist of super conducting magnet.
• Hydrogen atom allign themself parallel or antiparallel to the primary magnetic field (B) is
known as longitudnal magnetisation along the axis of B.
• The greater proportion alligns parallel ( low energy ) than antiparallel (high energy ) to
primary magnetic field. Therefore, net magnetic vector is along the primary magnetic field.
• This net magnetic field is oriented in patient’s body along Z – axis.

10. • Protons of hydrogen aton spin around the longitudnal axis
of primary magnetic field. This spinning is known as
‘Precession’.
• The rate of precession is termed as larmor frequency.
• Frequency changes with in proportion to magnetic field
strength.
• At 1.5 = 63.9MHz
• When protons process together, this is known as ‘ In phase’.
• When protons process seprately, this is known as ‘out of
phase’

11. GRADIENT COIL
• They generate secondary magnetic field over the primary
magnetic field.
• It is also resposible for loud noises of MRI.
• They arranged in opposition to each other to produce positive
and negative poles.
• This arrangment gives MRI the capacity to take image
directionally along x,y and z axis.
• There are 3 gradient coil which alligned accoerding to axis
along which they act.
• It also allows spatial encoding for MRI images in x,y and z axis.
This is known as ‘localisation’.
• Localisation helps in producing images of different section of
body.

12. RF COIL
• It stands for Radio Frequecy coil.
• These coils are used to transmiting the RF pulse and recieving signals in MRI.
• They came in many designs for specific body parts for eg., head, wrist,
ankle, knee, shoulder, etc.
• Also used to improve signals to knownest ratio to get best possible diagnostic
images

13. • RF coil used to transmit a second magnetic field or RF
pulse which result in disturbance of proton allignment.
• Some low energy parallel proton flip to high energy
state due to which there is decrease in longitudnal
magnetisation as shown in fig. A.
• Secondly, proton become syncronised and process in
‘inphase’due to which net magnetisation vector turns
towards the tranverse plane i.e., right angle to primary
magnetic field that is called tranverse magnetisation as
shown in fig. B.
Fig. A
Fig. B

14. RELAXATION
• RF coils areusedto recieve signal to create images. As
proton resume thier normal state in the primary
magnetic field prior to transmission of RF pulse, this is
called Relaxation
• When relaxation is in longitudinal axis is T1 relaxation
as shown in Fig. A.
• When relaxation is in transverse axis is T2 relaxation
as shown in Fig. B
Fig. A
Fig. B

15. • After the RF pulse several proton flip back to
thier low energy state i.e., parallel to magnetic
field by giving thier energy to suurounding lattice
due to which there is change in longitudinal
relaxation known as T1 relaxation or spin lattice
relaxation. (as shown in Fig. A)
• On ploting graph of magnetisation over time,
magnetisation will increase with time (as shown in
Fig. B).
• The T1 relaxation time will vary depending on
tissue composition.
Fig. A
Fig. B

16. • After RF pulse proton that were in phase begin to de
phase out of the larmor frequency in the transverse (x-y)
axis. This is known as spin spin realaxation or T2
relaxation, which results in reduction in transverse
magnetisation. (as shown in Fig. A).
• On plotting graph of transverse magnetisation over time.
(as shown in Fig. B).
• In reality the spins dephase quicker than T2 relaxation
because of inhomogenitics in the magnetic field (B).( as
shown in Fig. C).
• T2* = T2 relaxation + field inhomogenietics.
• T2 relaxation time will also vary depending on tissue
composition.
Fig. A
Fig. B
Fig. C

17. NET MAGNETIC VECTOR
• The net magentic vector is the sum of longitudinal and transverse
magnefication.
• Net magnetic vector spirals around Z axis with net precession.
• → →

18. RF RECEPTION
• The changing magnetic moment of net magnetic vector results in Free Induction
Decay ( FID ).
• This induces an electrical signal.
• Signal recieved by RF coil is in the transverse plane.

19. COMPUTER SYSTEM
• The computer system the RF signal and performs
an analog to digital conversion ( A/D conversion
)
• Digital signal representing the image body part
is stored in temprary image space or K space.
• The K space stores digitized MRI signals during
data acquisition.
• The digital signal is then sent to an image
processor where a mathematical formula called
Fourier Transformation is applied at the image
of MRI scan is displayed on monitor.

20. BIBLIOGRAPHY
• Physics NCERT bookof class XII.
• www.google.com
• https://youtu.be/Ok9ILIYzmaY