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“MAGNETIC RESONANCE IMAGING PRINCIPLES”

“MAGNETIC RESONANCE IMAGING PRINCIPLES”. Antecedentes. MRI is based on the principles of nuclear magnetic resonance (NMR), a spectroscopic technique used to obtain microscopic chemical and physical information about molecules. Phisics … Spin.

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“MAGNETIC RESONANCE IMAGING PRINCIPLES”

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  1. “MAGNETIC RESONANCE IMAGING PRINCIPLES” Alejandro Jaramillo Robles Soluciones Globales en Imagenología MRI-DT

  2. Antecedentes MRI is based on the principles of nuclear magnetic resonance (NMR), a spectroscopic technique used to obtain microscopic chemical and physical information about molecules Imagenología por Resonancia Magnética

  3. Phisics … Spin …is a fundamental property of nature. Spin comes in multiples of 1/2 and can be + or -. … two or more particles with spins having opposite signs can pair up to eliminate the observable manifestations of spin Imagenología por Resonancia Magnética

  4. Phisics… Max Plank a particle can undergo a transition between the two energy states by the absorption of a photon The energy E of a photon is related to its frequency υ called resoanance frequency, by Plank´s constant h. E= υ h

  5. Properties of Spin A particle with a net spin in a magnetic field B, can absorb a photon of a frequency υ. The frequency υ depends on the gyromagnetic ratio γof the particle υ = γB γH= 42.58 MHz/T Imagenología por Resonancia Magnética

  6. Nuclei of interest inMRI

  7. Electromagnetic Spectrum Imagenología por Resonancia Magnética

  8. Energy Level Diagrams E = hγB When the energy of the photon matches the energy difference between the two spin states an absorption of energy occurs Imagenología por Resonancia Magnética

  9. Energy Level Diagrams Constant Magnetic Field Variable Frecuency Variable Magnetic Field Constant Frequency E = hγB Imagenología por Resonancia Magnética

  10. Spin Packets

  11. Magnetization Vector

  12. Net Magnetization

  13. At Equilibrium Mz = Mo Mxy = 0

  14. Relaxation Time If enough energy is put into the system with a frequency equal to the resonance frequency…

  15. Relaxation Time Mz = 0 Mxy ≠ 0

  16. Relaxation Time T2 Mxy ≠ 0 Mz = 0

  17. Relaxation Time T2 The time constant which describes the return to equilibrium of the transverse magnetization Mxy = 0 Mz = 0

  18. Agua Grasa δ 3.5ppm Chemical Shift • The magnetic field that each nuclei experiment varies according to the type of nuclei and bonds in the molecule Imagenología por Resonancia Magnética

  19. Relaxation Time T1 The time constant which describes how MZ returns to its equilibrium value Mz = Mo

  20. Relaxation Time T1, T2 T2 ≤ T1

  21. Free Induction Decay - FID Imagenología por Resonancia Magnética

  22. Free Induction Decay - FID Frequency Domain Time Domain Imagenología por Resonancia Magnética

  23. FID 90o Sequence Imagenología por Resonancia Magnética

  24. FID 90o Sequence Imagenología por Resonancia Magnética

  25. Spin Echo Sequence Imagenología por Resonancia Magnética

  26. Magnetic Resonance Imaging • Information generated by a proton in a magnetic field, returning to its equilibrium, after being exposed to a RF signal. Imagenología por Resonancia Magnética

  27. Gradient …is a variation in the magnetic field with respect to position υ = γB Each region experience a unique magnetic field Imagenología por Resonancia Magnética

  28. Pulse Diagram t Imagenología por Resonancia Magnética

  29. Pulse Diagram t Imagenología por Resonancia Magnética

  30. Pulse Diagram t Imagenología por Resonancia Magnética

  31. Pulse Diagram t Imagenología por Resonancia Magnética

  32. Pulse Diagram t Imagenología por Resonancia Magnética

  33. Pulse Diagram t Imagenología por Resonancia Magnética

  34. Image Processing • MR – Back Projection one-dimensional field gradient is applied at several angles, and the NMR spectrum is recorded for each gradient Imagenología por Resonancia Magnética

  35. Image Processing Imagenología por Resonancia Magnética

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