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L5-contrast

L5-contrast - Contrast Signaltonoise ratio contrast =...

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2 ) ( ) ( 2 2 2 2 2 2 2 2 = βκγ στδ σιγναλ μεαν σνρ 2 1 signal signal contrast - =
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Contrast types Static contrast T1-weighted T2-weighted T2*-weighted   fMRI (BOLD) Dynamic contrast Time of flight (TOF)   MRA Velocity-encoded phase contrast (VENC-PC)   MRA Perfusion-weighted contrast    fMRI (cerebral blood flow) Diffusion-weighted Contrast
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Relaxation time and image contrast T1-weighted T2-weighted T2*-weighted
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What determines contrast type? Main pulse-sequence parameters Sequence family (Spin-echo, gradient echo, EPI, etc.) TR TE Flip angle (mainly for gradient-echo related sequences) Preparation-module parameters Spoiler TI (inversion time) Fat saturation Water excitation
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TR=1.5 s, TE=3.05 ms, Flip angle = 10, TI = 0.8 s Water excitation: ON TR=1.61 s, TE=2.54 ms, Flip angle = 15, TI = 1.1 s MPRAGE: 3D gradient echo on Siemens Trio (3T)
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A simple approximation MR signal: Contrast: 2 1 / / 0 ) 1 ( ) ( T TE T TR xy e e M TE M S - - - = = B B A A T TE T
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  • Spring '08
  • Lu
  • Magnetic resonance imaging, Nuclear magnetic resonance, EPI, pulse sequence, gradient echo, Diffusionweighted Contrast

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L5-contrast - Contrast Signaltonoise ratio contrast =...

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