Basics of mri

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this is the basics of mri

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Basics of mri

  1. 1. BASICS OF MRI Presented by:- Pranali. N. Kulkarni Ganesh M. Nair Aaditee S. Kulkarni Omkar Haldonkar
  2. 2. MAGNETIC RESONANCE IMAGING  Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to visualize internal structures of the body in detail.
  3. 3. WHAT IS A SPIN????  Atomic nuclei with an odd number of protons behave like spinning particles which in turn create a small nuclear spin angular momentum.  This angular momentum of anµ : magnetic momentBo : magnetic flux density electrically charged particle such as the nucleus of a proton leads to a magnetic dipole moment.  These magnetic moments are referred to as SPINS.
  4. 4. PRECESSION AND LARMOR FREQUENCY Acc. To electromagnetic theory , nucleus of H2 proton posses magnetic moments to align itself with the magnetic field in which it is field. This results in precession or wobbling of magnetic moment about the magnetic field with an angular frequency called Larmor frequency.
  5. 5. N N Z Z X,Y X,YS S
  6. 6.  MRI can be explained as interaction of spins with three magnetic fields
  7. 7. BASIC STEPS OF MRI1) 2) 3)
  8. 8. Z STEP 1 Mz STEP 2 M(t) STEP 3 Y MxyX STEPS OF MRI
  9. 9. STEP 1 H Z MoMo= Equilibrium magnetization.Mz = Magnetization along z. Anytime themagnetization vector is displaced along z, it will becalled M.Mxy= Component of M that is in XY plane
  10. 10. STEP 2M can be displaced by applying a magnetic field H1(rotating at Larmor freq of hydrogen nuclei) RF pulse causes: At the end of 90 pulse, M=Mxy and Mz=0
  11. 11. STEP 3RF pulse is turned offMxy diminishes towards zeroand Mz increases from zero.After the 90 RF pulse,theRF coil is switched to receivermode.
  12. 12. VOLTA FREE INDUCTION DECAY GE TIME
  13. 13. FREE INDUCTION DECAY At room temp. more protons are in a low energy state. The excited proton tends to return to low energy state with a spontaneous decay. This decay is exponential in nature

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