A system for determining a parameter of body tissue of a patient including a flexible elongated device (10, 10, 50, 50, 50a, 400, 430, 430, 443, 110, 150, 210, 250) having a tubular portion (16, 402, 432, 432, 444, 116, 216) having a lumen (410) formed therein, a marker element (79, 422, 438, 442, 438, 445, 448), at least a portion of the marker element positioned distally of the tubular portion, and a sensor (26, 26, 56, 56, 56a, 412, 126, 156, 226, 256) for determining a parameter of body tissue, the sensor positioned within the marker element. A connector (30, 80, 130, 180, 230, 280) operably connects the tubular portion to an indicator (40, 140, 140, 240, 245), the sensor determining the parameter and the indicator providing an indication of the parameter measured by the sensor.
