A. give more contrast information with less signal information
B. have less signal information with more contrast information
C. have more signal information with the same contrast information
D. have the same signal information with more contrast information

Thanks!

Now it is clear

Kostas

I don’t think increasing susceptibility effects with increasing field strength has anything to do with the Curie law (which is to do with temperature).

The magnetisation of a sample which is not a permanent magnet is given by M=χH, where χ is the (dimensionless) magnetic susceptibility of the sample, and H is one way of describing magnetic field strength, measured in amperes per meter. We may also write magnetic field strength as B=μ0(1+χ)=μ0μrH=μH, where μ0 is the (constant) permeability of free space (units of henries per metre, or newtons per ampere squared), μr is the (dimensionless) relative permeability of the sample to μ0, μ is the magnetic permeability of the sample, B is the magnetic field strength as flux density (Tesla). We may write, then, M=χB/μ.

So, you can see that magnetisation scales with B and χ. This means that magnetisation differences between tissues of different magnetic susceptibility are magnified as we increase field strength. This means larger magnetic field gradients will exist at these tissue boundaries, accelerating the dephasing between the protons on either side of the boundary. This causes signal loss.

Firstly, you say that “microscopic susceptibility changes cause larger local magnetic field gradients and greater dephasing of spin isochromats results, increasing the apparent T2 and causing faster signal decay.”

Shouldn’t be decreasing the T2 and causing faster signal decay?

Secondly, I can understand that susceptibility is increased with field strength (that is why BOLD imaging is better at 3.0T)

I am not sure if I understand how, though. Has anything to do with the Curie law?

Thanks

Kostas