Hi,
Yes, that's exactly right.
As the read-out timing is not changed, then the difference in the
time which the 180 degree pulse is applied is the correct value
to use for the asym time, and your example is correct.
Mark
Antti Tarkiainen wrote:
> Mark Jenkinson wrote:
>
> > Hi,
> >
> > I've just responded to the question about using gradient-echo vs
> > spin-echo.
> > Unfortunately it is not easy or optimal to use our existing software
> > for this.
> > It is much better to use a spin-echo sequence.
> >
> > As for the asym time, it is the timing difference between the 180
> degree
> > pulses in the two spin-echo scans. The echo time (TE) is kept the same
> > for both scans, but the 180 degree pulse is set at TE/2 for the
> > symmetric
> > scan (normal spin-echo) and set to (TE/2 + asym time) for the
> > asymmetric scan.
>
>
> Hi!
>
> So, do I understand correctly that (with spin-echo) the asym time, used
> to calculate the dwell-to-asym-ratio in fugue, should be equal to the
> amount of time used to shift the 180 degree pulse (and not two times
> that because the actual echo is delayed by two times the shift with
> respect to the symmetric scan)? E.g., if the dwell time is 540 us and
> the 180 degree pulse is shifted by 1170 us, the dwell-to-asym-ratio
> should be 0.46?
>
> Antti
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