A non-invasive medical treatment installation has a therapy C-arm mounted on a base, and defining an isocenter. A therapy apparatus having a focus is mounted at the free end of a carrier arm, that has a fixed end attached to the therapy C-arm. The mounting of the fixed end of the carrier arm to the therapy C-arm allows orbital movement of the carrier arm along the therapy C-arm between two final positions respectively delimited by the opposite ends of the C-arm. The carrier arm is mounted to the therapy C-arm to allow rotation of the carrier arm around a rotational axis, so that when the carrier arm is at either of said final positions, it extends beyond the respective end of the C-arm.