260 mri system block diagram

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  • MRI System Block Diagramspectrometerr.f.coilgradient coilXampYampZamp

  • Principle of Gradient CoilBzxBzz

  • IsotopeSpin %age IabundanceMHz/T

    1H 1/299.98542.5752H 10.0156.5313C 1/21.10810.7114N 199.633.07815N 1/20.374.3217O 5/20.0375.7719F 1/210040.0823Na 3/210011.2731P 1/210017.25Common NMR Active Nuclei

  • Alignment of Spins in a Magnetic FieldB0 fieldMM=0

  • Energy in a Magnetic Field(Zeeman Splitting, Spin )E+1/2= B0/2E-1/2= +B0/2P+1/2= 0. 5000049P-1/2= 0.49999511.5T, T=310K, P(E)exp(E/kT)mI = +mI =

  • Larmor FrequencyE+1/2= B0/2E-1/2= +B0/2Allowed transitions E = B0= 0mI = mI = +0 = B0

  • Quantum Mechanical Description(Spin Case)> = a> + a++> I=, 2I+1 Zeeman splittingsmI = mI = +Mz = = a+2 a2Mxy =

  • Coupling with a B1 FieldB0B1Birdcage coilAtime

    160.bin

  • Spin ExcitationMMMrotating framelaboratory frame

    3.bin

    1.bin

  • Free Induction DecayFTFTfrequencyfrequencytimetimeM

    15.bin

    16.bin

  • Free Induction DecayMMM909090small positive shim mis-setmedium positive shim mis-setlarge positive shim mis-set

    41.bin

  • Free Induction DecayMMM909090small negative shim mis-setmedium negative shim mis-setlarge negative shim mis-set

    44.bin

  • Product OperatorsMx MxMy Mycos + MzsinMz Mzcos MysinxxxMx Mycos MzsinMy MyMz Mzcos + MxsinyyyMx Mxcost + Mysin t tMy Mycost Mxsin t tMz Mz tr.f.freeprecessionxyz

  • Bloch EquationsdMxy(t) = Mxy(t)dtT2MzMxyMzMzMxyMxy

  • T1 RelaxationMz(t) = M0 + {Mz(0) M0}exp(-t/T1)MzMzttsaturationrecoveryinversionrecoveryM0M0Mz(0) = 0Mz(0) = M0

    11.bin

    12.bin

  • Spin EchoMM180180180909090small positive shim mis-setmedium positive shim mis-setlarge positive shim mis-set

    29.bin

  • Spin EchoMMM180180180909090small negative shim mis-setmedium negative shim mis-setlarge negative shim mis-set

    38.bin

  • T2 RelaxationMxy(t) = Mxy(0) exp(t/T2)MxytdMxy(t) = Mxy(t)dtT2

    10.bin

  • Slice SelectiontimetimefrequencyfrequencyFTFT

  • Slice SelectiontimefrequencyG