Abstract: A therapy apparatus for treating tissues by emission of focused ultrasound waves, includes a probe having a transducer formed by ultrasound elements distributed in several categories (N1 to NM) on a face for emission of focused ultrasound waves which is a surface of revolution generated by the rotation of a curve segment around an axis of symmetry, with the categories of ultrasound elements define independent and substantially contiguous focal volumes, and a control circuit including a signal generator for independently activating, alternately and substantially consecutively, the ultrasound emitter categories in such a way as to ensure continuous insonification in a ring shape originating from different categories of ultrasound emitters.