Hi SPMers,
I've used the SPM2 to perform coregister in SPECT images. I am using the
"Mutual Information" cost function, and the "Trilinear" interpolation, with
"Wrap X, Y and Z", and "don't mask images".
The rotations and translations are perform perfectly, but, the scaling isn't
work, once that the image object don't wrap.
I'm storing the parameters of the coregister (i get the P vector in rotine
spm_matrix) and during the coregister the scaling parameters didn't change
the value, remaining invariable in 1:
function [A] = spm_matrix(P)
% returns an affine transformation matrix
% FORMAT [A] = spm_matrix(P)
% P(1) - x translation
% P(2) - y translation
% P(3) - z translation
% P(4) - x rotation about - {pitch} (radians)
% P(5) - y rotation about - {roll} (radians)
% P(6) - z rotation about - {yaw} (radians)
% P(7) - x scaling
% P(8) - y scaling
% P(9) - z scaling
% P(10) - x affine
% P(11) - y affine
% P(12) - z affine
q = [0 0 0 0 0 0 1 1 1 0 0 0];
P = [P q((length(P) + 1):12)];
T = [1 0 0 P(1);
0 1 0 P(2);
0 0 1 P(3);
0 0 0 1];
R1 = [1 0 0 0;
0 cos(P(4)) sin(P(4)) 0;
0 -sin(P(4)) cos(P(4)) 0;
0 0 0 1];
R2 = [cos(P(5)) 0 sin(P(5)) 0;
0 1 0 0;
-sin(P(5)) 0 cos(P(5)) 0;
0 0 0 1];
R3 = [cos(P(6)) sin(P(6)) 0 0;
-sin(P(6)) cos(P(6)) 0 0;
0 0 1 0;
0 0 0 1];
Z = [P(7) 0 0 0;
0 P(8) 0 0;
0 0 P(9) 0;
0 0 0 1];
S = [1 P(10) P(11) 0;
0 1 P(12) 0;
0 0 1 0;
0 0 0 1];
A = T*R1*R2*R3*Z*S; % A is the affine transformation matrix.
Why the scaling don't work in coregister?
Thanks
Henrique Amaral
Hospital das Clínicas
University Of São Paulo - Ribeirão Preto - Brazil
