Dear Jesper,
Thank you for explaining this issue.
As I have seen in HCP protocol the common practice is a pair of AP/PA
spin echo EPI with matched BW/FOV/matrix. Is it advisable to acquire
extra volumes? or even some BOLD volumes with an opposing
phase-encoding direction?
Yes I was thinking about the gradual heating of the gradients. I
wonder if disturbance in the active shim is something serious to
avoid.
Sincerely yours,
Sourena
On 2/11/14, Jesper Andersson <[log in to unmask]> wrote:
> Dear Sourena,
>
>> Should the topup approach be considered superior to fieldmap
>> correction regarding (single-band) fMRI?
>
> if you are only getting a single pair for calculating a fieldmap I don't
> think it is superior to a "traditional" fieldmap. It is mainly just another
> way of obtaining the field.
>
>> How serious is the effect of gradient thermal state on fMRI/DTI
>> signals specially when the scanner has just started its daily job?
>> Does there exist some guideline to adhere?
>
> I am not sure what you mean by "gradient thermal state". Are you talking
> about the gradual heating of the gradients during a long run? If so, I don't
> think it is a problem for fMRI. Anything slow and gradual tend to be
> regressed out anyway.
>
> For DTI I don't know. Maybe someone else has some experience?
>
> Jesper
>
>>
>> Thanks in advance,
>> Sourena
>
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