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