bad result in vcgrappa when R=3

[kingaza]

I am quite confused...
the code in basic_vcgrappa.py is modified as

    kspace[1::3, ...] = 0
    kspace[2::3, ...] = 0

While the results are quite good when R equals to 2 or 4

[Nicholas McKibben]

I can recreate this issue. Is this due to the center line of kspace being omitted? I think in general you want to include the center of kspace.

Try:

# R=3
kspace[0::3, ...] = 0
kspace[2::3, ...] = 0

Using the above I get the following:

[kingaza]

yes, I got the same result as you. Thank you for the hint.
But why vcgrappa is so sensitive to the center line? I don't remember the paper mentioned about it...

[Nicholas McKibben]

I can't say why it's so sensitive, that's an interesting result. Do you know of any other reference VC-GRAPPA implementations that we could test against? Might also be worth attempting the experiment on real data, simulated data is not always representative of how algorithms perform on real datasets.

[kingaza]

I will try more data later. thanks again.
There could be some other solution, i.e. generating calib data away from center. But it seems another topic than virtual coil.

[Nicholas McKibben]

Related to #72

[kingaza]

I tested it with real data, and it worked. But the improvement is not always significant as mentioned in the paper.
This issue is closed as I have no idea how to evaluate it further. Anyway, it can be traced by the new one #72