1.    Because of a malfunction in the hardware of an MRI...

1.    Because of a malfunction in the hardware of an MRI scanner, the RF pulse amplitude is twice what it should be. The operator of the scanner observes no signal when applying a 90◦ pulse.

a)   Why, assuming you were unaware of the malfunction, would you find this unusual?

b)   Why is there no signal?

c)   What, assuming you were aware of the malfunction, could you do to get maximum signal? [Hint: θ_flip = γB₁T, where γ is the gyromagnetic ratio, B1 is the magnitude of the RF pulse, and T is time.]