The subject invention pertains to a method and apparatus for placing a minimally-invasive access with respect to a patient's bone or other non-soft tissue. The subject invention can use a drilling machine incorporating an ultrasound motor. The subject drilling machine can be applied to sample, for example, bone biopsies under MRI control. In a specific embodiment, the subject ultrasound motor can be completely manufactured of non-magnetic materials, such as plastics, titanium, and titanium alloy, or ceramics and piezoceramics. The subject drilling apparatus can be placed into an MRI near field without influencing the image quality, and without the drilling apparatus itself being disturbed by the MRI magnet, gradient, or high-frequency field. The subject invention can incorporate good shielding with the subject drilling apparatus use of these materials, and can achieve minimal, if any, image distortions or so-called artifacts. Thus, the subject invention can involve the problem by use of non-magnetic materials of low magnetic susceptibility for the design of an actuation unit.