1. Explain what is PD-weighted contrast. Describe how to select imaging parameters to obtain PD-weighted images. Explain why a large TE cannot be used
2. Suppose we are imaging a human brain (see Table 12.2 for the NMR properties of different brain tissues). We use the strategy described above in Problem 12.6 and acquire signals after the system is in the steady state. For simplicity, we assume the intensity of the reconstructed MR image is directly proportional to the magnitude of the transverse magnetic field right after the RF excitations. In order to get maximal signal strength, we use π/2 pulses.
(a) In order to get the best contrast between GM and CSF, what is the best value for TR?
(b) Using the TR value computed in part (a), what is the contrast between GM and CSF? What is the contrast between GM and WM?