A system comprises a first signal handling unit sized and shaped for insertion to a reference distance within a first body cavity and a probe sized and shaped for insertion into a second body cavity the probe including an energy emitting head and a second signal handling unit, wherein one of the first and second signal handling units comprises a transmitter and the other of the first and second signal handling units comprises one of a receiver adapted to receive signals from the transmitter and a signal reflecting element, wherein, when the other of the first and second signal handling units comprises a signal reflecting element, the one of the first and second signal handling units comprises a receiver in combination with a controller operatively connected to the receiver, the controller generating an output varying as a distance between the first and second signal handling units varies. In addition, a system comprises a probe sized and shaped for insertion in a first body cavity and a measuring element extending from the probe to contact tissue adjacent to an opening to a second body cavity, the measuring element being movably coupled to the probe to vary a depth to which the probe may be inserted into the first body cavity before the measuring element contacts the tissue adjacent to the opening of the second body cavity.