brede_loc_xform - Transform a set of coordinates
function K = brede_loc_xform(L, 'PropertyName', ...
'PropertyValue');
Input: L Location structure
Property: Type [ {Brett} | InvBrett | MeyerLindenberg |
MNI2Tal | InvMeyerLindenberg | PANA2TAL |
Tal2MNI | Tal2PANA | MTTSPM | InvMTTSPM | MTTFSL |
InvMTTFSL | MTTpooled | InvMTTpooled | PANA2MNI |
MNI2PANA ] Type of transformation
Output: K Location structure with new coordinates
This function transforms the coordinates of the location
structure, eg, from SPM99 to "Talairach" coordinates
It takes the coordinate values from the "coord" field from the
input argument (if the input is a 'loc' structure) and sets
the "coord" and "x", "y" and "z" fields in the output 'loc'
structure to the transformed values.
The type 'Brett' can be used to transform from
McGill/MNI/SPM96/SPM99 space to Talairach SPM95 space.
This is the nonlinear transformation (approach 2) described by
Matthew Brett. 'InvBrett' is the inverse operation.
'MeyerLindenberg' is a simpler affine transformation and
'InvMeryerLindenberg' is approximately the inverse operation
of this.
The MTT transformation are the MNI-to-Talairach (MTT)
transformation listed in the Lancaster 2007 paper. According to
validation they should be better than Brett's MNI2tal.
The PANa2Tal, Tal2PANa, PANa2MNI and MNI2PANa are conversions
from preauricular nasion (PAN) space to and from Talairach and
MNI space. For the a-version (PANa) of PAN the origo is set at
[ 0 -24 -54 ]/1000 in MNI space and the y-z tilt is
asin(14/107).
MNI2Tal is presently set to 'Brett' and Tal2MNI to 'InvBrett'.
Note on PAN transformations: The periauricular-nasion (PAN)
coordinate system employed by the electroencephalongraphy
literature is difficult to match to the MNI/Talairach systems:
A transformation from PAN to MNI was constructed by matching
periauricular and nasion points on the single subject MNI
template provided with SPM99. When the transformation was used
on a PAN coordinate provided in (Bentley, 2000) there was a
discrepancy on several centimeters judging from the images and
labeling. Thus these transformation is very imprecise and
should not be used unless the discrepancy is somehow accounted
for.
References:
Andreas Meyer-Lindenberg, Matthew Brett,
http://www.mailbase.ac.uk/lists/spm/1998-06/007
http://www.mrc-cbu.cam.ac.uk/Imaging/mnispace.html
Jack Lancaster and others, Bias Between MNI and Talairach
Coordinates Analyzed Using the ICBM-152 Brain Template, Human
Brain Mapping 28:1194+, 2007.
Example:
% Transform from MNI to Talairach
L.coord = [10 12 14] / 1000; % coordinates in meter
K = brede_loc_xform(L, 'type', 'brett');
K.coord
% Transform back again to MNI, - now with matrix
X = K.coord;
brede_loc_xform(X, 'type', 'invbrett')
See also BREDE, BREDE_LOC, BREDE_LOC_VOL, BREDE_LOC_MAT2LOC,
BREDE_VOL_LOC, BREDE_TA3_LOC.
$Id: brede_loc_xform.m,v 1.13 2009/02/12 11:49:43 fn Exp $