A = [1 1 2 2 3 3 3];
[U, I] = unique(A, 'first');
x = 1:length(A);
x(I) = [];
Therefore in your code it sould be something like, supposing you are using the right column to detect duplicates, lets call it names
[~,I] = unique(names); % Detect unique cases of right colum and gives back their indexes
names(I) = []; % Deletes duplicates in names
volumetric_data(I) = []; % Deletes duplicates in left column.
