A system, comprising: a catheter; an expandable member; a plurality of sensor modules disposed on an outer surface of the expandable member and circumferentially spaced apart from one another, wherein each of the plurality of sensor modules includes a first emitter configured to emit light of a first wavelength, and a detector configured to detect light; a controller coupled to the plurality of sensor modules, wherein the controller is configured to: from each detector, receive along a first short vector, a measurement of light intensity over time of light, reflected off of body tissue, at the first wavelength and originating from a first emitter from a same sensor module; from each detector, receive along a first long vector, a measurement of light intensity over time of light, reflected off of body tissue, at the first wavelength and originating from a first emitter from a circumferentially adjacent sensor module, calculate separate perfusion indexes corresponding to measured light intensity over time of each first short vector and each first long vector; and cause the display of the separate perfusion indexes corresponding to measured light intensity over time of each first short vector and each first long vector. a catheter; an expandable member; a plurality of sensor modules disposed on an outer surface of the expandable member and circumferentially spaced apart from one another, wherein each of the plurality of sensor modules includes a first emitter configured to emit light of a first wavelength, and a detector configured to detect light; a controller coupled to the plurality of sensor modules, wherein the controller is configured to: from each detector, receive along a first short vector, a measurement of light intensity over time of light, reflected off of body tissue, at the first wavelength and originating from a first emitter from a same sensor module; from each detector, receive along a first long vector, a measurement of light intensity over time of light, reflected off of body tissue, at the first wavelength and originating from a first emitter from a circumferentially adjacent sensor module, calculate separate perfusion indexes corresponding to measured light intensity over time of each first short vector and each first long vector; and cause the display of the separate perfusion indexes corresponding to measured light intensity over time of each first short vector and each first long vector. from each detector, receive along a first short vector, a measurement of light intensity over time of light, reflected off of body tissue, at the first wavelength and originating from a first emitter from a same sensor module; from each detector, receive along a first long vector, a measurement of light intensity over time of light, reflected off of body tissue, at the first wavelength and originating from a first emitter from a circumferentially adjacent sensor module, calculate separate perfusion indexes corresponding to measured light intensity over time of each first short vector and each first long vector; and cause the display of the separate perfusion indexes corresponding to measured light intensity over time of each first short vector and each first long vector.