# urgent: MRI calculations question

I have a biomedical imaging exam tomorrow and I'm struggling quite a bit with this question below (from b-d). I was hoping someone could help answer these questions or at. I'll describe my approach to each question and hopefully someone can give me some direction on if and where I have gone wrong.

Qb) the total response should just be the sum of the individual responses. Thus the total signal is a sinc of magnitude 1mV and frequency approximately $$π/5\cdot10^3$$ rad/sec (since it appears as though there are 5 peaks in the echo within 50ms corresponding to a period of 10 ms). Thus the magnitude-frequency plot should just be a rect

Qc) the intensity of an MRI signal is: $$I=k [H^+] (1-e^{-TR/T_1}) e^{-TE/T_2}$$
No intensity is given but is it possible to use the voltage given each material? if TR is long then $$1-e^{-TR/T_1)}$$ should be approximately=1. Therefore $$I=k [H^+]e^{-TE/T_2}$$.

A simple substitution of $$0.4\cdot10^{-3}=e^{-TE/T_2}$$ for material 1 then gives T2=12.8 ms. T2 for material 2 would be 13.5 ms. But is it justified to substitute voltage into $$\frac{I}{k[H^+]}$$?

Qd) I'm really not sure. It seems like the question is asking about the magnitude-frequency when T2 weighted (long TR and long TE) and so material 1 would appear slightly brighter than material 2. But not sure where to go from that.