The LTA Transform Format
WORK IN PROGRESS
LTA means Linear Transform Array. The .lta format is from subject ras to talairach ras, and stores affine. It is generic enough that it will list what type of transform it is (e.g. voxel or ras). Here are most of the relevant types:
#define LINEAR_VOX_TO_VOX 0 #define LINEAR_VOXEL_TO_VOXEL LINEAR_VOX_TO_VOX #define LINEAR_RAS_TO_RAS 1 #define LINEAR_PHYSVOX_TO_PHYSVOX 2 #define TRANSFORM_ARRAY_TYPE 10 #define MORPH_3D_TYPE 11 #define MNI_TRANSFORM_TYPE 12 #define MATLAB_ASCII_TYPE 13 #define LINEAR_CORONAL_RAS_TO_CORONAL_RAS 21 #define LINEAR_COR_TO_COR LINEAR_CORONAL_RAS_TO_CORONAL_RAS
A sample .lta files looks like following
type = 0 nxforms = 1 mean = 127.000 125.000 115.000 sigma = 10000.000 1 4 4 +1.141600 +0.018630 +0.010876 -23.066311 -0.019849 +1.142709 +0.150979 -29.566288 -0.010058 -0.155729 +0.919673 +26.393215 +0.000000 +0.000000 +0.000000 +1.000000 src volume info valid = 1 # volume info valid filename = /tmp/bert/mri/nu.mgz volume = 256 256 256 voxelsize = 1.0000 1.0000 1.0000 xras = -1.0000 0.0000 0.0000 yras = 0.0000 0.0000 -1.0000 zras = 0.0000 1.0000 0.0000 cras = 5.3997 18.0000 0.0000 dst volume info valid = 1 # volume info valid filename = /usr/local/freesurfer/stable/average/RB_all_2007-08-08.gca volume = 256 256 256 voxelsize = 1.0000 1.0000 1.0000 xras = -1.0000 0.0000 0.0000 yras = 0.0000 0.0000 -1.0000 zras = 0.0000 1.0000 0.0000 cras = 0.0000 0.0000 0.0000