An ultrasonic imaging method particularly for 3D gynaecologic inspections provides an ultrasound probe having a number of transducers forming a linear array. An imaging scanning unit connected to the transducers alternatively generates electric driving signals for each transducer. The probe is oscillated in a direction transversal to the longitudinal extension of the linear array of transducers and around an axis coinciding or parallel to the longitudinal extensions of the linear array of transducers to modify the orientation of the direction of propagation of the ultrasound signals. The ultrasound beams are steered so that the linear array of transducers generates a trapezoidal scanning slice or plane diverging in the direction of propagation of the beams.