1. MRI DRAFT 5-12-09

2. Principles of MRI ► Sectional Anatomy ► Provides anatomic and physiologic info ► Non- invasive ► No radiation  Magnetic fields and Radio waves

3. MRI vs. Conventional Radiography ► Sectional  No superimposition ► Can resolve small contrast differences ► Uses magnets instead of x-rays ► Flat image  Superimposed structures ► Can only distinguish air, at, soft tissue, bone and metal ► Most organs can only be seen with contrast ► Uses radiation

4. Xray vs. MRI

5. Signal Production ► MRI depends on nucleus ► Hydrogen  Most commonly used  Most common element in body  Creates a strong signal  Nucleus is a single proton

6. Hydrogen ► Contains  1 proton  1 orbiting electron

7. Precession ► Protons in random directions ► With magnet attempt to line up  Do not line up precisely  They rotate about the direction of the magnetic field ► Protons  Absorb energy when RF is applied  Absorption is called resonance ► Radiowaves and nuclear precession are at the same frequency

8. Field Strength and Frequency ► 1.5 tesla ► 1 telsa ► 0.5 telsa ► 0.2 telsa ► 63MHz ► 42 MHz ► 21 MHz ► 8 MHz

9. Precession ► http://mrsrl.stanford.edu/~brian/mri- movies/resonance.mpg

10. Spin Control ► http://images.google.com/imgres?imgurl=http://w ww.magnet.fsu.edu/education/tutorials/magnetac ademy/mri/images/mri- scanner.jpg&imgrefurl=http://www.magnet.fsu.ed u/education/tutorials/magnetacademy/mri/&usg=_ _7QaxmAuglPxgvYqzlBDl4yatfQc=&h=300&w=390 &sz=33&hl=en&start=1&tbnid=iCrVIzxgDH1sFM: &tbnh=95&tbnw=123&prev=/images%3Fq%3Dre sonance%2B%252B%2BMRI%26gbv%3D2%26hl %3Den

11. The Wonder of Waves ► http://images.google.com/imgres?imgurl=http://w ww.magnet.fsu.edu/education/tutorials/magnetac ademy/mri/images/mri- scanner.jpg&imgrefurl=http://www.magnet.fsu.ed u/education/tutorials/magnetacademy/mri/&usg=_ _7QaxmAuglPxgvYqzlBDl4yatfQc=&h=300&w=390 &sz=33&hl=en&start=1&tbnid=iCrVIzxgDH1sFM: &tbnh=95&tbnw=123&prev=/images%3Fq%3Dre sonance%2B%252B%2BMRI%26gbv%3D2%26hl %3Den

14. Gradient Coils

15. MRI Slices of Brain

16. Equipment Console Computer Room Magnet Room

17. Console and Computer Room

18. Magnet Room ► Must be LG enough for magnets and antennas  Coils are antennas wound up in shape of body part  3 types of magnets (strength measured in Gauss or Tesla) ► RESISTIVE  Not to exceed 0.15 telsa  10 tons  LG amount of current through coils  Fringe field in all directions ► SUPERCONDUCTIVE or Cryogenic  High field strengths  10 tons  Cooled with liquid helium  Fringe field in all directions ► PERMANENT  Not to exceed 0.3 telsa  100 tons  Smaller fringe field

19. Body Coils…Antennas

23. Significance of Signal ► Signal strength is converted to different shades of gray  White is strong signals  Black is weak signals ► Three properties affect signal strength  Nuclear Density  Relaxation rates  Flow phenomena

24. Relaxation Rates: T1 and T2

25. MRA and Flow Phenomena

27. Contrast Media ► No Oral Contrast ► Gadolinium  IV injected  Lower toxicity  Low side effects ► Less than IV in CT and conventional radiography  Many new contrasts being developed but none approved for clinical use yet

28. Lawsuits and Gadolinium ► In May 2007 FDA issued a public warning about Gadolinium increasing the incidence of Nephrogenic Systemic Fibrosis  For those with impaired kidney function  Development of excessive scar tissue and thick, hardened and tight areas of skin which often cover the joints, resulting in severe limitations on movement.  Can lead to confinement to a wheelchair, bed or death.

29. Contraindications ► Objects containing metal ► Scissors, O2 tanks, and gurneys ► Metallic prosthesis ► Aneurysm clips ► Hearing aids ► Slivers of metal in eyes ► Electronic equipment ► Claustrophobia

30. Imaging Planes ► Images can be obtained in many planes  Coronal  Transverse  Oblique ► Equal resolution for any plane ► Loss of detail if reconstructed ► 3D block of tissue can be obtained instead of slices

31. Coronal Thorax

32. Sagittal Thorax

33. 3D Imaging

34. Closed MRI

35. Open MRI

36. Sitting MRI

37. Extremity MRI