A method and apparatus are disclosed for measuring a characteristic, e. Many of the compounds disclosed herein are excretable by the renal system of a subject or patient and are useful for visualizing the renal system of a subject or patient. With this construction, forces imposed laterally on the lead body by the conductor engaging the side wall surfaces of the lumen upon bending of the lead body are absorbed without damaging the lead body by reason of engagement of the conductor with a corner ridge causing the corner ridge thereby engaged to recede toward a condition of being coplanar with its subtended pair of side wall surfaces. Thus a technician viewing the display will be able to identify whether a low MER is a result of an impairment in the network or the from an individual cable modem.