Magnetic Resonance Imaging

It explains the working Concepts of MRI Scanner

1. Magnetic resonance iMaging BY , A RAVINDKUMAR B

2. MRI MRI is a radiology technique That uses magnetism, radio waves, and a computer to produce images of body structures. MRI is based on the principles of NMR In1997 the first MRI exam was performed on a human being. It took 5 hours to produce one image.

3. 1 920 1 9 30 19 6 19 7 1 980 1924 - Pauli suggests that may have angular m o m e n t u m (spin). 1937 – Rabi nuclear particles measures magnetic moment of nucleus. Coins “magnetic resonance”. 1940 1950 1946 – Purcell shows that matter absorbs energy at a resonant frequency . 1946 – Bloch demonstrates that nuclear precession can be measured in detector coils . 1959 – Singer measures blood flow using NMR (in mice). HISTORY 1972 – Damadian patents idea for large NMR scanner to detect malignant tissue . 1973 – Lauterbur publishes method for generating 1973 – Mansfield in d e p e n de n tl y publishes gradient approach t 1 o 9 M 75 R – . Ernst develops 2D- Fourier transform for MR . images using NMR gradients. NMR renamed M R I MRI scanners become clinically prevalent. 1990 2000 1990 – Ogawa and colleagues create functional images using endogenous, b l o o d - ox yge n a ti o n contrast . 1985 – Insurance reimbursements for MRI exams begin.

4. FATHER OF MRI • Magnetic resonance imaging inventor

5. • 1944: Rabi Physics (Measured magnetic moment of nucleus) • 1952: Felix Bloch and Edward Mills Purcell Physics (Basic science of NMR phenomenon) • 1991: Richard Ernst Chemistry (High-resolution pulsed FT-NMR) • 2002: Kurt Wuthrich Chemistry (3D molecular structure in solution by NMR) • 2003: Paul Lauterbur & Peter Mansfield Physiology or Medicine (MRI technology) NOBAL PRIZES FOR MRI

6. WHAT CAN BE DIAGNOSED BY AN MRI SCAN? • • • • • • • • • • Most ailments of the brain, including tumours Sport injuries Musculoskeletal problems Most spinal conditions/injuries Vascular abnormalities Female pelvic problems Prostate problems Some gastrointestinal tract conditions Certain ear, nose and throat (ENT) conditions Soft tissue and bone pathology/conditions

7. • • • • • • A cardiac pacemaker Certain clips in your head from brain operations A cochlear implant A metallic foreign body in your eye Had surgery in the last 8 weeks If you are pregnant WHO CAN’T HAVE AN MRI SCAN?

8. PRINCIPLE MRI makes use of the magnetic properties of certain atomic nuclei. Hydrogen nucleus (single proton) present in water molecules, and therefore in all body tissues. The hydrogen nuclei partially aligned by a strong magnetic field in the scanner. Niranjan Ultrasound India pvt.Ltd

9. C O N T I.. • • • • The nuclei can be rotated using radio waves, and they subsequently oscillate in the magnetic field while returning to equilibrium. Simultaneously they emit a radio signal. This is detected using antennas (coils) Very detailed images can be made of soft tissues. Niranjan Ultrasound India pvt.Ltd

10. Randomly arranged hydrogen atom After the strong magnetic field applied

11. MAIN COMPONENTS OF MRI • • • Scanner Co m pu t ers Recording hardware

12. S CANNE R • • An MRI scanner is a large tube that contains powerful magnets. Main components of scanner Static magnetic field coils Gradient coils RF (radiofrequency) coils Niranjan Ultrasound India pvt.Ltd

13. Static Magnetic Field Coils • Three methods to generate magnetic field Fixed magnet Resistive magnet Super conducting magnet • • • • Fixed magnets and resistive magnets are generally restricted to field strengths below 0.4t High-resolution imaging systems use super conducting magnets. The super-conducting magnets are large and complex They need the coils to be soaked in liquid helium to reduce their temperature to a value close to absolute zero. Niranjan Ultrasound India pvt.Ltd

14. GRADIENT COILS • • • • Gradient coils are used to produce deliberate variations in the main magnetic field There are usually three sets of gradient coils, one for each direction. The variation in the magnetic field permits localization of image slices as well as phase encoding and frequency encoding. T he se t of grad i en t c oi l s f or th e z ax i s a r e he l m ho l t z pairs, and for the x and y axis paired saddle coils. Niranjan Ultrasound India pvt.Ltd

15. RADIOFREQUENCY COIL • • • • • • • RF coils act as transmitter and receiver RF coils are the "antenna" of the MRI system That transmit the RF signal and receives the return signal. They are simply a loop of wire either circular or rectangular Helmholtz pair coils consist of two circular coils parallel to each other. They are used as the z gradient coils in MRI scanners Paired saddle coils are also used for the x and y gradient coils. Niranjan Ultrasound India pvt.Ltd

16. ADVANTAGES OF MRI • • • • No ionizing radiation Variable thickness in any plane Better contrast resolution Many details without iv contrast Niranjan Ultrasound India pvt.Ltd

17. DISADVANTAGES OF MRI • • • • • Very expensive Dangerous for patients with metallic devices placed within the body Difficult to be performed on claustrophobic patients Movement during scanning may cause blurry images RF transmitters can cause severe burns if mishandled Niranjan Ultrasound India pvt.Ltd