How to find neighbor voxels of a given voxel?

Hi! I am working with 3D MRI image of size(164x187x145). For a given voxel i need to consider 26 neighbouring 3x3x3 patch.(now 27 scalar values)Then consider all 26 neighbouring conventional 3x3x3 patches and compute average intensity for all these neighbouring patches.(So totally i have 53 scalar intensity values).How to perform this? Anyone who knows Plz reply !! code that i referred is as follows

function[IndexNeighbours] = findNeighbours(Index,MatrixSize)
 %%**************************************************************************
% Module name:      findNeighbours.m
% Version number:   1
% Revision number:  00
% Revision date:    10-2013

2013 (C) Copyright by Patrick Granton Maastro Clinic

%  Outputs:
%      IndexNeighbours = The index positions of valid voxels 

%  Usage: [IndexNeighbours] = findNeighbours(33014,[400 400 400])

Description:

%*************************************************************************
% References: 
%
%*************************************************************************
%%Revision History
%  %%*************************************************************************

%1
Base = [+1 +1 0 ...
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+1 -1 0 ...
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+1 +1 +1; ...
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+1 0 +1; ...
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+1 -1 +1; ...
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+1 0 -1; ...
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+1 -1 -1; ...
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+1 0 0 ...
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0 +1 0 ...
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0 -1 0 ...
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0 +1 +1; ...
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0 0 +1; ...
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0 -1 +1; ...
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0 +1 -1; ...
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0 0 -1; ...
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0 -1 -1; ...
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-1 +1 0 ...
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-1 -1 0 ...
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-1 +1 +1; ...
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-1 0 +1; ...
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 -1 0 0];

[I J K] = ind2sub([MatrixSize],Index);

neighbours = Base+repmat([I J K],[26 1]);

valid_neighbours = (1 - sum(neighbours(1:26,:)<=0,2));
valid_neighbours_Indices = find(valid_neighbours==1);
IndexNeighbours = sub2ind([MatrixSize],[neighbours(valid_neighbours_Indices,1)],[neighbours(valid_neighbours_Indices,2)],[neighbours(valid_neighbours_Indices,3)]);
end

My doubt is what i must give for matrixsize and index if I am using 164*197*145 3D matrix?

Thanks in advance!

Answer 1

[KSSV]

You may use knnsearch to get the nearest neighbors. Read about knnsearch

[KSSV]

Check the link, might be useful. https://in.mathworks.com/matlabcentral/answers/310452-how-can-i-find-26-neighbors-of-point-with-coordinates-of-i-j-k

[Sandhiya Prakash]

Is knnsearch work for 3D image matrix?

[Makis]

is knnsearch really accurate?