The invention relates to a safe mechanism for resistance to drilling, by use of a door mounted crankshaft mechanism. The rotor also carries a plurality of flat cutters. The data of the slot or slots stored in the storage means is read in synchronization with the second clock signal. The control unit includes phased-array signal processing circuitry for effectuating an electronic scanning of the internal tissue structures which facilitates one-dimensional, 2D, and 3D data acquisition and circuitry for defining multiple data gathering apertures and for coherently combining structural data from the respective apertures to increase spatial resolution.