Apparatus and method for measuring blood flow direction using a fluorophore

An apparatus for measuring blood flow direction using a fluorophore, the apparatus comprising:

• an input interface for retrieving at least one input frame of input image data in at least part of a fluorescence spectrum of the fluorophore;
• one or more processors configured to:
• identify at least one blood vessel structure within the input image data;
• determine a blood flow direction in the identified blood vessel structure by comparing signs of a spatial gradient of fluorescence intensity along the identified blood vessel structure and a temporal gradient of fluorescence intensity at at least one location in the identified blood vessel structure;
• and
• compute at least one output frame of output image data, in which parts of the input image data corresponding to the identified blood vessel structure are overlaid with time-varying marker data representative of the blood flow direction;
• and
• an output interface for outputting the output frame;
• wherein the one or more processors are further configured to define a positive direction along the identified blood vessel structure and determine the blood flow direction is along the positive direction if the temporal gradient and the spatial gradient have opposite signs;
• wherein the temporal gradient is a difference between fluorescence intensity in a later input frame and an earlier input frame at the at least one location, and the spatial gradient is a difference between fluorescence intensity at the at least one location and a downstream location.