A guidewire system for treating a patient, comprising: a sensor assembly (116,152) for detecting a physiological characteristic of a patient; a hypotube sized for insertion into vasculature of the patient and having an integrated sensor mount therein for predictably locating the sensor during assembly, the hypotube having a wall structure forming a lumen, the sensor mount being formed within the wall structure of the hypotube and having a first mechanical stop configured to limit movement of the sensor assembly (116,152) in at least a first dimension and a second mechanical stop configured to limit movement of the sensor assembly (116,152) in at least a second dimension; and a sensor housing disposed about the sensor mount and having a window formed therein to provide fluid communication between the sensor assembly (116,152) and an environment outside the hypotube, and wherein the first mechanical stop is configured to maintain the sensor at a desired height, and wherein the second mechanical stop is configured to maintain the sensor at a desired lateral location, and wherein the sensor mount has a first region having a first width and a second region having a greater second width, the sensor assembly (116,152) having a width corresponding to the first width of the first region in a manner that substantially limits movement at the lateral location in a lateral direction, the sensor assembly (116,152) extending into the second region, the second width providing additional clearance for the sensor assembly (116,152) in a manner that prevents distortion of sensor readings when the hypotube flexes as it traverses tortious vessels in the patient. a sensor assembly (116,152) for detecting a physiological characteristic of a patient; a hypotube sized for insertion into vasculature of the patient and having an integrated sensor mount therein for predictably locating the sensor during assembly, the hypotube having a wall structure forming a lumen, the sensor mount being formed within the wall structure of the hypotube and having a first mechanical stop configured to limit movement of the sensor assembly (116,152) in at least a first dimension and a second mechanical stop configured to limit movement of the sensor assembly (116,152) in at least a second dimension; and a sensor housing disposed about the sensor mount and having a window formed therein to provide fluid communication between the sensor assembly (116,152) and an environment outside the hypotube, and wherein the first mechanical stop is configured to maintain the sensor at a desired height, and wherein the second mechanical stop is configured to maintain the sensor at a desired lateral location, and wherein the sensor mount has a first region having a first width and a second region having a greater second width, the sensor assembly (116,152) having a width corresponding to the first width of the first region in a manner that substantially limits movement at the lateral location in a lateral direction, the sensor assembly (116,152) extending into the second region, the second width providing additional clearance for the sensor assembly (116,152) in a manner that prevents distortion of sensor readings when the hypotube flexes as it traverses tortious vessels in the patient.