[SOLVED] Is Birdcage coil single channel or multi channel ?

[Alam Wajih]

Hi,

I read somewhere that the birdcage coil used for MRI is single channel but I don't know what it actually means. So, I would really appreciate it if anybody could explain the meaning of it. Also, what would are the basis on which the coil is supposed to be single channel or multi channel

 

[mtwieg]

A birdcage coil usually supports (at least) two linear modes which are orthoganol. So the coil itself has two feed ports which can be driven independently. In this case it can be viewed as two channels. However it's usual for these two ports to be driven in quadrature so that the two linear modes combine to get a nice CP mode. In this case it's common to just use a quadrature coupler to split a single channel into quadrature components, and then connect those two to the coil feeds. So now it's like a single channel that produces the desired CP mode.

 

[Alam Wajih]

I am sorry but I am still not clear about what is the meaning of single channel and multi channel and what is the difference between them. I have also attached some pictures that I draw in XFDTD and I was told by a colleague that it is multichannel. How did he come to know by simply viewing the pictures.


I appreciate your time and effort. Thank you!!

 

[mtwieg]

The number of channels usually refers to the number of independent RF inputs/outputs the overall coil has. In theory there can be as many as there are modes, normally only the two first order (linear) modes are used. Those pictures don't tell you which modes are being used and how. But 12 rungs is strange for a birdcage...

 

[Alam Wajih]

Thank You for your help