The triple differential cross sections for electron impact ionization helium (e, 2e) reactions are calculated by use of the BBK and modified BBK model at different gun angles of incident electron energy 64.6 eV. The structures of the cross sections and the physical natures of these structures are discussed in detail. It is found that for the non-coplanar geometry, cross sections are determined by a variety of effects together and these effects are converted to each other under different conditions. Moreover, strong dynamical screening effect is observed in the final state of the perpendicular plane symmetric geometry.