A guidewire system for treating a patient, comprising: a sensor assembly 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 in at least a first dimension and a second mechanical stop (w1) configured to limit movement of the sensor assembly 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 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 (w1) is configured to maintain the sensor at a desired lateral location, and wherein the sensor mount has a first region having a first width (w1) and a second region having a greater second width (w2), the sensor assembly having a width corresponding to the first width (w1) of the first region in a manner that substantially limits movement at the lateral location in a lateral direction, the sensor assembly extending into the second region , the second width (w2) providing additional clearance for the sensor assembly in a manner that prevents distortion of sensor readings when the hypotube flexes as it traverses tortious vessels in the patient. a sensor assembly 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 in at least a first dimension and a second mechanical stop (w1) configured to limit movement of the sensor assembly 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 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 (w1) is configured to maintain the sensor at a desired lateral location, and wherein the sensor mount has a first region having a first width (w1) and a second region having a greater second width (w2), the sensor assembly having a width corresponding to the first width (w1) of the first region in a manner that substantially limits movement at the lateral location in a lateral direction, the sensor assembly extending into the second region , the second width (w2) providing additional clearance for the sensor assembly in a manner that prevents distortion of sensor readings when the hypotube flexes as it traverses tortious vessels in the patient. <EOS>