Methods and systems for determining information about a vascular bodily lumen are described. An exemplary method includes generating an electrical signal, delivering the electrical signal to a plurality of excitation elements in the vicinity of the vascular bodily lumen, measuring a responsive electrical signal from a plurality of sensing elements in response to the delivered electrical signal, and determining a lumen dimension. Specific embodiments include generating a multiple frequency electrical signal. Another embodiment includes measuring a plurality of responsive signals at a plurality of frequencies. Still other embodiments include using spatial diversity of the excitation elements. Yet other embodiments use method for calibration and de-embedding of such measurements to determine the lumen dimensions. Diagnostic devices incorporating the method are also disclosed, including guide wires, catheters and implants. The methods and systems described herein are advantageous as they do not include injecting a second fluid for the measurements.