[Mrtrix-discussion] Number of tracks

[René Besseling]

Hi Luis,

Just type streamtrack -h; the tracks that are selected are those of
sufficient length (-minlength option) and sufficiently high FA or FOD
amplitude (-cutoff value). Note that the -maxnum option sets the
maximum allowed number of trials. If your data is of low quality, the
number of tracks generated can be lower than what you set by -number
if not enough valid tracks can be constructed within -maxnum trials.
Furthermore, tractography start points (seed points) are selected at
random within the ROI you specify using -seed, so if you use the same
streamtrack command twice, the result will be different (due to
different random seed points). Information about a streamtrack result
can be obtained by typing track_info your_file_name.tck

Best regards,

René

On Wed, May 11, 2011 at 3:54 PM, Luis Morís
<luis.moris.fernandez at gmail.com> wrote:
> Hello everyone,
>
> I write because I have started to use mrtrix, and I've found a doubt.
> To be able to do tractography you have to use the parameter -number
> that will set the exact amount of tracks that will be calculated.
>
> My doubt is how does the program decide which tracks to include or
> not. If I set it to 1000 and I run it again with 1000000. What
> difference do I find between the two set of tracks? Is it purely
> random, depends on the length, the FA...
>
> Thanks a lot in advance,
>
> Luis.
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