Hi Michael,
I have to admit that I am not an MR physicist and I initially used the term
based on what a proper MR physicist told me.
I agree that "dwell time" seems to be more confusing that "echo spacing"
and so I prefer to use the term "echo spacing" - although the command
line option is stuck with --dwell for backward compatibility. It may be the
case that you can consider a dwell time in either the readout or phase
encode directions for an EPI sequence. It is definitely *not* the readout
sampling rate that should be used - it is all about the speed in the *phase encode*
direction. Hopefully "echo spacing" makes it clearer.
All the best,
Mark
On 5 Mar 2012, at 12:55, Michael Harms wrote:
> Hi Mark,
> Technically, isn't dwell time the inverse of the read-frequency sampling
> rate? Just pointing this out because I had someone think that was the
> "echo spacing" once.
>
> cheers,
> -MH
>
>> Hi,
>>
>> Yes, in the FEAT GUI (the pre-processing section, which is what we
>> recommend you use, with the b=0 image as the "functional" input) we
>> need the "effective echo spacing" which is the actual echo spacing
>> (or dwell time) _divided_ by the acceleration factor (SENSE factor here).
>>
>> All the best,
>> Mark
>>
>>
>> On 5 Mar 2012, at 08:15, Jürgen Hänggi wrote:
>>
>>> Dear FSL experts
>>>
>>> We try to unwarp distortions in DTI data using field maps, but he DTI
>>> data
>>> were acquired with the SENSE technique (factor 2.0).
>>>
>>> Does the dwell time used in fugue have to be adjusted for the SENSE
>>> factor?
>>>
>>> If yes, do I have to multiply or rather divide the dwell time by the
>>> SENSE
>>> factor?
>>>
>>> Thanks in advance
>>> Best regards
>>> Jürgen Hänggi
>>>
>>>
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