Could you please clarify your question? What do you mean by '16 byte elements'? How do you want to split up you data?
If you have an array consisting of doubles, a '16-byte element' is two entries (a double is 8 bytes). So you could reshape your array to have two columns:
imageMatrix = rand( m, n );
reshapedImageMatrix = reshape( imageMatrix, prod(size(imageMatrix))/2, 2 );
Of course, in this example, m*n should be even.
Mark
