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بسم الله الرحمن الرحيم

بسم الله الرحمن الرحيم. Basic Physics Principles of MRI. MRI The physics basics. Magnetic Resonance Imaging. MRI Overview. No ionizng radiation Superior soft tissue contrast High resolution and multiplanar capability. History. General description.

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بسم الله الرحمن الرحيم

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  1. بسم الله الرحمن الرحيم Basic Physics Principles of MRI

  2. MRIThe physics basics Magnetic Resonance Imaging

  3. MRI Overview • No ionizng radiation • Superior soft tissue contrast • High resolution and multiplanar capability

  4. History

  5. General description

  6. When B0 applied to it, the momentum rate will be: Substituting I we have: This is Larmor equation. From Larmor equation the Larmor frequency is:

  7. mp can be divided to mpz and mpxy (mpz is assumed to be in B0 direction) If mpxy=0 ===> dmp/dt=0 means that there is no change in the direction of dipole moment and no signal If the sample contain large amount of protons, net magnetic moment will be M If M is in Z direction there is no signal. When M direction changes as a results of an arbitrary B we have signal and B could be B0z+B1

  8. Quantum mechanical discription From the quantum view any nucleus with angular momentum of I has a magnetic moment of For any atom magnitude of nuclear angular moment is l (l is nuclear spin quantum number): In a magnetic field B0 the z component of mp can have different possible orientation with values of For a single proton magnitude of I=1/2 and hence ml=±1/2 For 1H l=1/2 ==> ml=±1/2 For 31P l=1/2 ==> ml=±1/2 For 19F l=1/2 ==> ml=±1/2 For 23Na l=3/2 ==> ml=-3/2 , -1/2, ½, 3/2 Nucleus with I=1 have Quadrapole state

  9. Energy state of each proton is: If a proton move from one state to another a change of energy is happens which is equal to and hence

  10. Statistical distribution of spin states In a large amounts of proton and the absence of B0 there is no net magnetization If a magnetic field of B0 is applied to them; Changing from one state to another release a photon of: The life time of each spin is:

  11. Bloch equations Bloch equations describe the behavior of nuclear magnetic moment of a sample with large amount of dipole moment in a magnetic field B; If an stimulus changes the direction of M from B (assume B=Bz) then changes to the Mz is given by: Changes to x and y direction of M are:

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