Tract Output and Tract Statistics Files

This page details the format of files used for outputting diffusion tensor tracts and tract statistics to file.

Tract File

Tracts are saved in an XML file, with a document type definition of: 


<?xml version="1.0" encoding="ISO-8859-1" standalone="yes"?>
<!DOCTYPE FibreTracts [
  <!ELEMENT FibreTracts (Tract*)>
  <!ELEMENT Tract (TractPt*)>
  <!ELEMENT TractPt (Position, DT?)>
  <!ELEMENT Position EMPTY>
  <!ELEMENT DT EMPTY>
  <!ATTLIST Tract Tract_Length CDATA #IMPLIED Mean_Trace CDATA #IMPLIED Mean_FA CDATA #IMPLIED Mean_RA CDATA #IMPLIED>
  <!ATTLIST Position x CDATA #REQUIRED y CDATA #REQUIRED z CDATA #REQUIRED>
  <!ATTLIST DT Dxx CDATA #REQUIRED Dxy CDATA #REQUIRED Dxz CDATA #REQUIRED Dyy CDATA #REQUIRED Dyz CDATA #REQUIRED Dzz CDATA #REQUIRED>
  <!ATTLIST TractPt Tr CDATA #IMPLIED FA CDATA #IMPLIED RA CDATA #IMPLIED>
]>
The file contains multiple fibre tracts each between <Tract Mean_FA= ...> and </Tract>. The mean FA, RA, Trace and total tract length for the tract are given for each tract. Each tract consists of multiple tract points, between <TractPt FA= ...> and </TractPt>. The x, y, and z- locations, along with the FA, RA, Trace and tensor values are shown for each point along the tract. The start of an example tracts file is shown below: 

<!--FibreTracts created by Jim on "14 Apr 2013 14:22:24.134 British Summer Time" by Operator ID "xinapse"-->
<FibreTracts>
<Tract Mean_FA="0.53510547" Mean_RA="0.8855659" Mean_Trace="0.0010343294" Tract_Length="109.3464">
<TractPt FA="0.14052612" RA="0.20005517" Tr="0.0013625667">
<Position x="2.7829976" y="35.955772" z="35.350163"/>
<DT Dxx="5.212712E-4" Dxy="-1.499838E-5" Dxz="-1.9085446E-5" Dyy="4.177915E-4" Dyz="1.2475579E-5" Dzz="4.2350407E-4"/>
</TractPt>
<TractPt FA="0.26908013" RA="0.39006734" Tr="8.8264444E-4">
<Position x="0.5208541" y="36.01654" z="35.712612"/>
<DT Dxx="3.6985968E-4" Dxy="6.1787E-6" Dxz="-2.6419022E-5" Dyy="2.786157E-4" Dyz="-3.261468E-5" Dzz="2.341691E-4"/>
</TractPt>
<TractPt FA="0.4144956" RA="0.6229453" Tr="9.925085E-4">
<Position x="-1.4852448" y="35.1677" z="36.39249"/>
<DT Dxx="4.058437E-4" Dxy="4.9790517E-5" Dxz="-8.515457E-5" Dyy="3.694797E-4" Dyz="-3.858402E-5" Dzz="2.1718514E-4"/>
</TractPt>
<TractPt FA="0.50673723" RA="0.78717244" Tr="0.0010878149">
<Position x="-3.292236" y="34.00712" z="37.214252"/>
<DT Dxx="4.6927852E-4" Dxy="7.597615E-5" Dxz="-1.2597156E-4" Dyy="3.9869896E-4" Dyz="-5.0620045E-5" Dzz="2.1983744E-4"/>
</TractPt>
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