A hand-held medical ultrasound apparatus (10), in particular for ultrasound computed tomography of the breast, comprises an ultrasound transducer (1), a reflector (2) and an indicator (311,321, 312) enabling the indication of a relative position and/or orientation between the transducer and the reflector. In a first embodiment, the transducer and the reflector are attached to a mechanical structure comprising a first frame (33) and a second frame (34), which allow to adjust the distance (d) between the transducer and the reflector in order to adapt to the shape of the breast. In a second embodiment, the tranducer and the reflector are not mechanically connected and a position and/or orientation sensor is provided to determine a relative position and/or orientation between the transducer and the reflector. In a third embodiment, thin resonant reflector layers are applied to introduce acoustic signatures in the tracked reflector signals.Un appareil médical à main à ultrasons (10) comprend un transducteur à ultrasons (1) pour émettre des ultrasons, un réflecteur (2) pour réfléchir au moins une partie des ultrasons émis, et un indicateur (21,22 311 312) pour permettre l'indication d'une position relative et/ou d'une l'orientation relative entre le transducteur (1) et le réflecteur (1).
