This paper deals with edge detection in 3d images such as scanner, magnetic resonance (NMR), or spatio-temporal data. We propose an unified formalism form 3d edge detection using optimal, recursive and separable filters recently introduced for 2d edge detection. Then we obtain some efficient 3d edge detection algorithms having a low comptutational cost. We also show that 3d edge closing enable to extract many edges not provided by the filtering stage without introducing noisy edges. Experimental results obtained on NMR images are shown.