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 LISTSERV Archives SPM Home SPM June 2008

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Re: Global Measure of deformation

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Wed, 11 Jun 2008 15:33:23 +0100

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 ```If you want to obtain such a metric from the deformations obtained via segmentation, then maybe the following will help.... P = spm_select(Inf,'.*seg_inv_sn.mat\$'); met = zeros(size(P,1),1); for i=1:size(P,1),     t = load(deblank(P(i,:)));     V = t.VF;     d = V(1).dim(1:3);     d2 = size(t.Tr);     vx = sqrt(sum(V(1).mat(1:3,1:3).^2));     kx = (pi*((1:d2(1))'-1)/d(1)/vx(1)).^2;     ky = (pi*((1:d2(2))'-1)/d(2)/vx(2)).^2;     kz = (pi*((1:d2(3))'-1)/d(3)/vx(3)).^2;     Cwarp = (1*kron(kz.^2,kron(ky.^0,kx.^0)) +...               1*kron(kz.^0,kron(ky.^2,kx.^0)) +...               1*kron(kz.^0,kron(ky.^0,kx.^2)) +...               2*kron(kz.^1,kron(ky.^1,kx.^0)) +...               2*kron(kz.^1,kron(ky.^0,kx.^1)) +...               2*kron(kz.^0,kron(ky.^1,kx.^1)) );     Cwarp = Cwarp*t.flags.warpreg;     Cwarp = [Cwarp*vx(1)^4 ; Cwarp*vx(2)^4 ; Cwarp*vx(3)^4];     Cwarp = sparse(1:length(Cwarp), 1:length(Cwarp), Cwarp, ...                     length(Cwarp), length(Cwarp));     v = t.Tr(:);     M = Cwarp;     met(i) = 0.5*v'*M*v; end figure plot(met) Note that this only gives measures for the nonlinear deformations, and does not include the initial affine transform. Best regards, -John On Wednesday 11 June 2008 14:06, Jason Steffener wrote: > Hello all, > I am wondering if some global measure of deformation can be calculated. > I am interested in having some way to assess the amount of deformation that > was needed to spatially normalize a subject's anatomical scan. > > thank you, > Jason. ```