noise parameters of the low noise amplifier in MRI system?

I need the noise parameters of the low noise amplifier in magnetic resonance imaging system? Anybody know how to get it? i could not find them from the datasheet of the product. What i need to know are:
? Equivalent noise resistance Rn (related to noise voltage source)
? Equivalent noise conductance Gn (related to noise current source)
? Correlation admittance Yr
? Scattering matrix or impedance matrix

Thanks.