Hi Mark,
thanks a lot for your answer!
In the meantime I calculated the difference between the flirt_applyxfm
output and the applyxfm4D output, using fslmaths. The resulting difference
has a mean intensity that corresponds to about 2 % of the mean intensitity
of the original time series (I looked that up in fslview).
I also noticed 2 other things: first, the flirt_applyxfm output looks a bit
smoother than the applyxfm4d output, and second, the applyxfm4d procedure
takes much longer than the flirt_applyxfm operation.
The 2 % seem a rather high difference to me, so I now have to decide which
of the two possibilities I choose... I have the intuition that the
applyxfm4D might be the more exact one because it takes longer to
calculate:-)... What would you suggest?
Cheers,
Lea
Am 08.10.2007 18:46 Uhr schrieb "Mark Jenkinson" unter
<[log in to unmask]>:
> Hi,
>
> That's right.
> There shouldn't be any real difference (although sometimes there
> are very slight numerical differences, but nothing big) if you only
> want to apply a single transformation to all the volumes in a 4D series.
>
> All the best,
> Mark
>
>
> On 8 Oct 2007, at 10:45, Lea Krugel wrote:
>
>> Dear FSL people,
>>
>> I'd like to know whether "applyxfm4D" with only one transformation
>> matrix
>> for all the volumes of a functional data set leads to somehow
>> different
>> results than flirt in combination with "applyxfm" and "init".
>> I'm asking because I used "applyxfm" for my functional data and
>> FEAT has no
>> problems in recognising the correct number of time points, so I
>> guess the
>> "applyxfm" command works fine here, also for functional data. My
>> understanding of "applyxfm4D" would then be that it is the right
>> tool when
>> applying more than one transformation matrix to the data, but with
>> only one
>> there is no difference between "applyxfm" and "applyxfm4D". Is that
>> right or
>> might there be problems with my output in later analysis steps?
>>
>> Thanks a lot,
>> Lea
>>
>>
>>
>> -------------------------------------------
>> Lea Krugel
>>
>> Max Planck Institute for Human Development
>> Neurocognition of decision making
>> Lentzeallee 94
>> 14195 Berlin
>> Tel.: +49-30-82406618
>> Fax: +49-30-82406616
>> email: [log in to unmask]
-------------------------------------------
Lea Krugel
Max Planck Institute for Human Development
Neurocognition of decision making
Lentzeallee 94
14195 Berlin
Tel.: +49-30-82406618
Fax: +49-30-82406616
email: [log in to unmask]
|