Filling zero intensity region of image from non-zero background information of the same image

Hello all,

I am working on DBT image reconstruction using SART algorithm. I segmented projection data to reduce time of reconstruction. The segmented projection data was fed to the SART reconstruction algorithm to get a set of slice images. The image of one slice is as shown below:

The clinical image is aligned to right side of the whole image and have zero intensity values to the left side. How can I fill the zero intensity image part with background of clinical image in order to have a smooth and continuous appearance.

Currently, I tried taking one column of image pixels from the left most side of clinical image part and used it to fill the zero intensity part. The image is shown below and not giving good results.

recSART_obj = load('recSART_obj_sim.mat');

reconim_slice = recSART_obj.recSART_obj;

[sizex, sizey] = size(reconim_slice);
reconim_mod = zeros (sizex,sizey);

figure(1); imshow(reconim_slice(:,:),[]);

columnsWithAllZeros = all(reconim_slice == 0);
croppedImage = reconim_slice(:, ~columnsWithAllZeros);
[rindex, cindex]= size(croppedImage);
reconim_mod(1:rindex,end-cindex+1:end) = croppedImage;

%recreating image part for cropped out region
maskbit = reconim_mod(:,end-cindex+1);
maskimage = repmat(maskbit, [1 sizey-cindex]);
reconim_mod(1:sizex,1:end-cindex) = maskimage;
figure(2); imshow(reconim_mod(:,:),[]);

Could you please provide some inputs on how to achieve this.

Thanks all.