A multimodality system includes first and second modalities, a catheter, and a processor. The catheter collects fluorescent light from a plurality of locations of a sample which has been irradiated with excitation light of the second modality; a detector detects intensity of the fluorescent light received from the plurality of locations as a function of an angle α formed between the normal to the sample surface and the optical axis of the excitation light. A processor calculates the angle α at each of the plurality of locations based on radiation of the first modality incident on the sample, and corrects the intensity of the detected fluorescent light using a calibration factor g(α). The calibration factor g(α) is a function of the angle α calculated at two or more of the plurality of locations. The angle α is composed of a transversal angle αt and an axial angle αa.