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Contrast T1 weighted – (MPRAGE-anatomical) T2 weighted – (fmri)

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Presentation on theme: "Contrast T1 weighted – (MPRAGE-anatomical) T2 weighted – (fmri)"— Presentation transcript:

1 Contrast T1 weighted – (MPRAGE-anatomical) T2 weighted – (fmri)

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4 Spin Relaxation Spins do not continue to precess forever Longitudinal magnetization returns to equilibrium due to spin-lattice interactions – T 1 decay Transverse magnetization is reduced due to both spin-lattice energy loss and local, random, spin dephasing – T 2 decay Additional dephasing is introduced by magnetic field inhomogeneities within a voxel – T 2 ' decay. This can be reversible, unlike T 2 decay

5 T1 decay – “spins back down” Collective Magnetic Moment of Protons end start B0B0 signal we “hear” V Time T1 Recovery MR Signal Time Typical T1 Graph 1 s

6 T2 decay – separation (dephasing) of “collective magnetic moment” sometime after RF excitation Immediately after RF excitation = collective magnectic moment individual spins separation (dephasing) a little time later T2 Decay MR Signal Typical T2 Graph Time 50 ms

7 Spin Echo YXYX

8 T2 Decay MR Signa l T1 Recovery MR Signal 50 ms 1 s Proton Density Contrast TE – echo time TR – repeat time

9 Proton Density Weighted Image

10 T2 Decay MR Signal T1 Recovery MR Signal 50 ms 1 s T1 Contrast time TE – echo time TR – repeat time

11 T1 Weighted Image

12 T2 Decay MR Signa l T1 Recovery MR Signal 50 ms 1 s T2* and T2 Contrast TE – echo time TR – repeat time

13 T2 Weighted IMage

14 ProtonDensityWeightedImageT1WeightedImageT2WeightedImage

15 Properties of Body Tissues MRI has high contrast for different tissue types!


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