Image fusing one image SPECT with 72 images CT

Hi all, please help me.

i have one image SPECT (dicom data) and 72 image CT(dicom data). I want to fuse it. Below is my trying coding for fuse. But still failed. any one can help me how to fuse one image SPECT with 72 images CT?

P = zeros(256, 256, 72);
for K = 1 : 72
    ctname = sprintf('I4%03d.dcm', K);
    P(:,:,K) = dicomread(ctname);
end
% imshow3D(P)


[spect map]=dicomread('128x128');
info = dicominfo('128x128');
gp=info.SliceThickness;
spect=(squeeze(spect));%smooth3
aa=size(spect);aa=aa(3);
imshow3D(spect);
% for K = 1 : 72 
K = 1
for K1 = 1 : 27
  C(:,:,:,K1) = imfuse(P(:,:,K),spect(:,:,K1));
  
end
  imshow3D(C(:,:,:,K))

Here i attached the result picture