An EAS marker assembly comprises a housing defining an interior cavity and an EAS marker and a weighting member disposed in the housing interior cavity, the weighting member being of a composition which does not interfere with operation of the EAS marker. In one example, the preamplifier circuit includes a first transistor having: a high impedance node connected to an input node connected to receive the electrical current signal from the photo detector, and a control terminal connected to receive active negative feedback proportional to the electrical current signal received at the input node. In at least one embodiment, implants are used with specific characteristics which are as unambiguous as possible with regard to the phase shift generated by the implants in a phase-contrast tomography examination. Additionally, the mixer is capable of receiving an input signal and downconverting at least a portion of the input signal that is propagating within a selected frequency range. The movable plunger or the movable seal is configured and arranged for adjusting to changes in volume of the lumen when the lumen is filled with an acoustically-favorable medium and sealed. The biocompatible form may also include one or more apertures for receiving a corresponding number of dental prostheses therethrough.