how to discard NaN vectors from a 3D matrix

Hi, I have a 3D matrix. some of its rows/columns/depth vectors can be all NaN. I wish to creat a new matrix which is the same as the original one only without the NaNs. is there a function that can help me do this ? in 2D i used ismember and just substitute them with []. but for the 3D case im stuck. here is an example code of such matrix

mat=ones(6,6,6);
mat(1:2,:,:)=NaN(2,6,6);
NANLoc=isnan(mat);

( so I want mat(3:6,:,:) as a new matrix)

any ideas? thanks