matrix operations on 3d packed images

Hi I have large 3d image files, i have a code that uses dialate and the standard matrix operations (A-B,A.*B,A+B) i understand that by using bwpack(A),bwpack(B) i can make my dialation calculation alot faster, my question is how to preform the other standard operations on those matrixes, is it possible to keep them in their packed form? and if so is it faster? or am i bound to preform standard operations on unpacked images.

[Jan]

Do the "large 3D image files" contain black&white images? Please show us the code and explain the relation between the 3D image files and the variables A and B.