A method of distinguishing between fluorescence imaging data contributions corresponding to two fluorescence imaging agents in a tissue of a patient during surgical imaging, comprising: illuminating the tissue with excitation light to simultaneously excite both a first fluorescence imaging agent and a second fluorescence imaging agent in the tissue, wherein the first and second fluorescence imaging agents have different fluorescence emission profiles in the tissue; receiving fluorescence imaging data of the tissue illuminated by the excitation light from an imaging sensor with a color filter array, wherein the fluorescence imaging data comprises at least a first pixel value from the sensor corresponding to a first color of the color filter array and a second pixel value from the sensor corresponding to a second color of the color filter array; determining, with a processor, a first contribution to the fluorescence imaging data corresponding to the first fluorescence imaging agent using the first and second pixel values in a first predetermined linear combination; characterised by determining, with the processor, a second contribution to the fluorescence imaging data corresponding to the second fluorescence imaging agent using the first and second pixel values in a second predetermined linear combination, wherein the first and second predetermined linear combinations are based on areas under color response curves of the first fluorescence imaging agent for the first and second colors and color response curves of the second fluorescence imaging agent for the first and second colors, and each of the respective imaging agent color response curves are based on multiplying the respective imaging agent emission profile with a spectral sensitivity of the imaging sensor for the respective color. illuminating the tissue with excitation light to simultaneously excite both a first fluorescence imaging agent and a second fluorescence imaging agent in the tissue, wherein the first and second fluorescence imaging agents have different fluorescence emission profiles in the tissue; receiving fluorescence imaging data of the tissue illuminated by the excitation light from an imaging sensor with a color filter array, wherein the fluorescence imaging data comprises at least a first pixel value from the sensor corresponding to a first color of the color filter array and a second pixel value from the sensor corresponding to a second color of the color filter array; determining, with a processor, a first contribution to the fluorescence imaging data corresponding to the first fluorescence imaging agent using the first and second pixel values in a first predetermined linear combination; characterised by determining, with the processor, a second contribution to the fluorescence imaging data corresponding to the second fluorescence imaging agent using the first and second pixel values in a second predetermined linear combination, wherein the first and second predetermined linear combinations are based on areas under color response curves of the first fluorescence imaging agent for the first and second colors and color response curves of the second fluorescence imaging agent for the first and second colors, and each of the respective imaging agent color response curves are based on multiplying the respective imaging agent emission profile with a spectral sensitivity of the imaging sensor for the respective color.