Optimizing nested for loops for image analysis

I am analyzing 4-dimensional images. The four dimensions are x and y for the resolution of the image, z for the depth of the image, and f for how many frames there are at each z (depth). I need to go through each z and sum all of the frames into one single frame. Right now, I am using nested for loops to go through each pixel of each image but this is very slow. Does anyone know how to optimize the code so that I can do this operation faster?

This is the code below:

Thank you!

clear all;

res = 1024;
frames = 20;
z = 15;
mkdir('SHG');
mkdir('TPEF');
% mkdir('Composite');

A = TIFFStack('freshex_6x_100mW_zstack_00001.tif', [], [1 z frames]);

% SHGstack = im2single(reshape(A(:,:,1,:,:), [res,res,z,frames]));
% TPFstack = im2single(reshape(A(:,:,2,:,:), [res,res,z,frames]));

%SHGstack = reshape(A(:,:,1,:,:), [res,res,z,frames]);
TPFstack = reshape(A(:,:,1,:,:), [res,res,z,frames]);

for i =1:res
    for j = 1:res
        for k = 1:z
    %SHGsum(i,j,k) = sum(SHGstack(i,j,k,:));
    %SHGmean(i,j,k) = mean(SHGstack(i,j,k,:));
    TPFsum(i,j,k) = sum(TPFstack(i,j,k,:));
    %TPFmean(i,j,k) = mean(TPFstack(i,j,k,:));
        end
    end
end

Answer 1

[KALYAN ACHARJYA]

TPFsum=sum(TPFstack(:,:,1:z,:));

Is this?

[Akarsh Lal]

I think I didn't phrase my question correctly...what I'm trying to do is at each depth (z), I am trying to add up all of the frames that are there. So for example, at z = 3 there are 15 frames. It's almost like there is a video at each depth and I need to add up each frame of that video at each depth. I hope that clarifies what my goal is.

Thank you for your response!