{{{
# transform file register.lta
# created by XYZ on Tue May  6 10:42:24 2014

type      = 0
nxforms   = 1
mean      = 0.0000 0.0000 0.0000
sigma     = 10000.0000
1 4 4
3.431423187255859e+00 -2.041964828968048e-01 -7.740691304206848e-03 2.756774902343750e+01 
2.015136182308197e-03 1.456980705261230e-01 -3.996406793594360e+00 1.583389892578125e+02 
-2.042964249849319e-01 -3.428334712982178e+00 -1.693789362907410e-01 2.647491455078125e+02 
0.000000000000000e+00 0.000000000000000e+00 0.000000000000000e+00 1.000000000000000e+00 
src volume info
valid = 1  # volume info valid
filename = TEMPLATE_FILE_PATH/template.nii
volume = 64 64 35
voxelsize = 3.437500000000000e+00 3.437499761581421e+00 4.000000000000000e+00
xras   = -9.972996711730957e-01 -7.120382040739059e-02 1.798351481556892e-02
yras   = 6.254287064075470e-02 -9.518167972564697e-01 -3.002218902111053e-01
zras   = 3.849399834871292e-02 -2.982859909534454e-01 9.537000060081482e-01
cras   = 1.612358093261719e+00 1.616348266601562e+00 4.727973937988281e+00
dst volume info
valid = 1  # volume info valid
filename = SUBJECT_FILE_PATH/orig.mgz
volume = 256 256 256
voxelsize = 1.000000000000000e+00 1.000000000000000e+00 1.000000000000000e+00
xras   = -1.000000000000000e+00 0.000000000000000e+00 0.000000000000000e+00
yras   = 0.000000000000000e+00 0.000000000000000e+00 -1.000000000000000e+00
zras   = 0.000000000000000e+00 1.000000000000000e+00 0.000000000000000e+00
cras   = 0.000000000000000e+00 0.000000000000000e+00 0.000000000000000e+00
subject fbirn-anat-101.v4
fscale 0.150000
}}}

The matrix (starting with 3.4375 ...) is the registration matrix. xras is the direction cosines for the column direction (in scanner RAS coordinates). yras and zras are the direction cosines for the row and slice directions. cras is the center of the volume in RAS coordinates. The first set of parameters is for the source volume. The second set is for the target volume.