Devices, systems, and methods for evaluating a physiological condition of a vessel are disclosed. In an embodiment, a medical system is disclosed. One embodiment of the medical system comprises a medical processing unit in communication with a first sensor, a second sensor, and an imaging source configured to obtain images of at least one intravascular instrument positioned within a body lumen. The medical processing unit is configured to: receive the images obtained by the imaging source； detect, using the images, when the first sensor is in a pre-determined spatial configuration with respect to the second sensor； and automatically initiate normalization of the first sensor and the second sensor in response to detecting that the first sensor is in the pre-determined spatial configuration with respect to the second sensor.
