[Mrtrix-discussion] Maximum track length using streamtrack

[Robert Smith]

Thijs

Nice pickup; indeed yes, the tracking is allowing streamlines to continue
up to the specified maximum length in either direction from the seed, such
that it is possible for streamlines to be generated which are up to twice
the 'maximum' length.

If you want to enforce your specified maximum length as a constraint upon
the entire streamline rather than each unidirectional half-streamline, the
easiest fix is as follows (in reference to the 0.2.9 code):
* in src/dwi/tractography/tracker/base.h, line 61:

bool set (const Point& seed, const Point& seed_dir = Point::Invalid) {
pos = seed; num_points = 0; return (init_direction (seed_dir)); }

change to:

bool set (const Point& seed, const Point& seed_dir = Point::Invalid) {
pos = seed; return (init_direction (seed_dir)); }


* in src/dwi/tractography/tracker/base.cpp, line 115:

void Base::new_seed (const Point& seed_dir)

At the start of this function (around line 117), insert this line:

num_points = 0;


I will see about making this the default behavior for the next MRtrix
release.

Regards
Rob

--

Robert Smith
Melbourne Brain Centre
245 Burgundy Street
Heidelberg VIC 3084
Telephone: (+61 3) 9035 7128
Fax: (+61 3) 9035 7301
Email:  r.smith at brain.org.au
www.florey.edu.au <http://www.fni.edu.au>        www.brain.org.au



On Fri, Jan 6, 2012 at 9:55 PM, Thijs Dhollander <
thijs.dhollander at uzleuven.be> wrote:

> Hi everyone,
>
>
> Using Mrtrix 0.2.9, I noticed the following: when setting the -length
> parameter with streamtrack ("max_dist" as reported by track_info
> afterwards), the actual maximum track length seems to be twice that value.
>  I suspect each track is allowed to continue up to the "-length"-distance
> in both directions from the seed, i.e. allowing the full track to be
> maximally twice the "-length" value in size?
>
>
> Happy 2012 & kind regards,
>
> Thijs
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