The head points file (.hpts) is just a file of lines containing a label, an index, and an xyz coordinate:

cardinal 2 0.000000 0.112500 0.000000 cardinal 3 0.071534 0.000000 0.000000 hpi 1 0.068430 0.020674 0.088621 hpi 2 0.040329 -0.083517 0.094487 hpi 3 -0.041193 -0.079972 0.100122 hpi 4 -0.054395 0.032501 0.102959 extra 1 0.000072 0.111427 0.000058 extra 2 0.070781 0.000371 0.000230 extra 3 -0.072046 -0.000394 -0.000207 extra 4 0.067647 0.020419 0.088373 ...

The transform file (.trans) is a 4x4 float matrix:

9.999452e-01 -1.047178e-02 0.000000e+00 -4.999973e+00 1.044092e-02 9.969981e-01 7.671904e-02 -1.033253e+01 -8.033852e-04 -7.671483e-02 9.970528e-01 -6.399206e+01 0.000000e+00 0.000000e+00 0.000000e+00 1.000000e+00

I don't know of anybody who actively uses the head point stuff, so I'm not sure if it's up to date with how you generated the data.

On Fri, Oct 27, 2006 at 11:16:04AM -0500, Juranek, Jenifer wrote:

Hi,

What are the file format requirements for the 2 files called to load head points - *.hpts and *.trans into tkmedit or tksurfer?

We have a whole-head neuromagnetometer (4-D Neuroimaging 3600 Magnes MEG system) with 248 sensor channels.

I'd like to co-register my dipole locations with FreeSurfer's aseg+aparc.mgz to efficiently localize dipoles x ROIs. I have already co-registered index points and headshape files to each subject's aMRI within 4D's software.

Any advice is greatly appreciated!

Jenifer