1. How MRI Works
Connor Schentag

2. Topics Background & History Construction Physics Transducers Images
Specializations
Recent Advances

3. Background MRI: Magnetic Resonance Imaging
Noninvasive medical imaging device
Uses magnetic fields and radio waves to generate images

4. History 1937 - Dr. Isidor I. Rabi discovers NMR
1950’s - First MR image is produced
Raymond Damadian discovers different signals from different tissues
Raymond Damadian builds the first MRI scanner

6. Construction

7. Physics Hydrogen atoms are abundant in the human body
All have a strong magnetic moment
When the magnetic field is applied, all align and cancel except a few.

8. Physics
An MRI applies a Radio Frequency specific to hydrogen, MHz/T (The Larmor Frequency)
The unmatched atoms produce ‘resonance’ and spin in the other direction
When the RF pulse is turned off, the atoms revert to the original alignment and give off RF energy
This is picked up by the RF coils

9. Transducer Computer receives all frequencies measured by the RF coils
A Fourier Transform is used to convert these points to a 2D or 3D image
where
Inverse for image:

10. Transducer

11. Transducer

12. Images
Each tissue returns to equilibrium based on T1 (spin- lattice) and T2 (spin-spin) relaxation
Can create T1-weighted or T2-weighted based on when signal is measured
T1: Often used for cerebral cortex, fatty tissue, general morphological information
T2: Useful for detecting edema and inflammation, such as revealing white matter lesions

13. Images: T1
T1 Bright: Fat, hemorrhage, slow flowing blood, protein rich fluid
T1 Dark: Bone, air, high water content such as tumour, inflammation

14. Images: T2 T2 Bright: High water content such as tumour, inflammation
T2 Dark: Bone, air, fat, protein-rich fluid

15. Organ Specializations
Neuroimaging: Very popular due to contrast between grey and white matter
Musculoskeletal: Used for joint disease and soft tissue tumours

16. Organ Specializations
Liver and Gastrointestinal: Often used with a contrasting agent, can detect lesions in pancreas and liver
Angiography (Arteries): Contrasting agents often used to evaluate for aneurysms

17. Specialized Configurations
Diffusion MRI: Measures diffusion of water molecules in tissue
Functional MRI: Measures signal changes in the brain due to changing neural activity
Real-Time MRI: “Filming” MRI, or the continuous monitoring of moving objects, such as joints or organs
Many more

19. Recent Advances
Siemens new system can acquire many MRI images simultaneously rather than sequentially
Lung MRI is now possible, using Toshiba’s new Ultrashort Echo Time (UTE)
Cardiac MRI has been greatly simplified, and can now take a full 3D chest volume scan
GE’s new Silent Scan technology to actively cancel the loud noise of MRI scans

20. Conclusion Began in the 70’s with Dr. Damadian Has its basis in NMR
Create images with a Fourier Transform
Can create various images based on what needs to be examined
Many different configurations for specialized needs
An actively researched field leading to many new advances

21. References
mrihistory.html