Maximum of normxcorr2

Hello,

I need to calculate the maximum of normalized cross correlation of million of particles. The size of the two parameters of normxcorr2 is 56*56. I can't parallelize the calculations. Is there any way to speed up the code especially that I dont need all the results but only the maximum value of each cross correlation (to know the displacement)?

Example of the algorithm

%The choice of 170 particles is because in each time the code detects 170 particles, so over 10000 images it's 1 700 000 particles
  particle_1=rand(56,56,170);
  particle_2=rand(56,56,170);
  for i=1:170
  C=normxcorr2(particle_1(:,:,i),particle_2(:,:,i));
  L(i)=max(C(:));
  end

Thanks in advance