Homework-2: NMR Spectroscopy.

  1. From the 1H NMR perspective, the human body is composed primarily of fat hydrogens (-CH2-) with a chemical shift of ~ 1 PPM, and water hydrogens (H2O) with a chemical shift of ~ 4.5 PPM. What is the resonance frequency difference between the NMR signal from these two types of hydrogens?
  2. The hydrogen T1, T2 and spin density values for common brain tissues are listed in the following table.

    TissueT1 (s) T2 (ms) r*
    CSF0.8 - 20 110 - 2000 70-230
    White0.76 - 1.08 61-100 70-90
    Gray1.09 - 2.15 61 - 109 85 - 125
    Meninges0.5 - 2.2 50 - 165 5 - 44
    Muscle0.95 - 1.82 20 - 67 45 - 90
    Adipose0.2 - 0.75 53 - 94 50 - 100
    *Based on r=111 for 12mM aqueous NiCl2

    At what TR and TE values is the signal from white matter approximately equal to that from gray matter in a spin-echo pulse sequence?

  3. When using an inversion recovery pulse sequence and a sample containing all the tissues in question number two, what TI value greater than 2 ms would guarantee at least 90% of the signal from all the tissues?

  4. You are using a 90-FID pulse sequence and the brain tissue sample in question number two. For adipose tissue, how much less signal will be present when TR=100 ms then when TR=500 ms?