# Tckgen maxlength default value

**URL:** <https://community.mrtrix.org/t/tckgen-maxlength-default-value/5939>\
**Category:** Uncategorized\
**Tags:** tractography\
**Created:** [August 15, 2022, 9:48am UTC](https://community.mrtrix.org/t/tckgen-maxlength-default-value/5939 "2022-08-15T09:48:48Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![dshastin](https://community.mrtrix.org/user_avatar/community.mrtrix.org/dshastin/32/2432_2.png) [@dshastin](https://community.mrtrix.org/u/dshastin)\
**Post date:** [August 15, 2022, 9:48am UTC](https://community.mrtrix.org/t/tckgen-maxlength-default-value/5939/1 "2022-08-15T09:48:48Z")

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Dear Community,

I am trying to decide on whole-brain tractogram streamline length limits for my study. With respect to the upper cut-off, MRtrix `tckgen -maxlength` default value is described to be 100 x voxelsize. For high spatial resolution / small voxel size data this may risk under-representing longer tracts (said to be up to 15 cm long e.g. in Schüz & Miller’s “Cortical areas: unity and diversity”). I wondered if there was some methodological consideration behind this default value, e.g. increasing chance of “false-positives” etc? Just trying to wrap my head around it.

Many thanks,

Dmitri