Fig. 2.

(a) Experimental setup and (b) fluorescence detection device. The phantom consisted of top and bottom layers, and a straw tube containing ICG–milk or milk was embedded at the surface of the bottom layer. The excitation and detection fibers were located on the surface of the top layer, and the fluorescence measurements were conducted by varying the thickness of the top layer and changing the depth of the tube. A photon-counting device measured fluorescence intensities. An on–off-driven excitation laser illuminated the phantom, and the fluorescence photons reaching the detector were counted synchronously with the excitation laser illumination. The photon count data were transferred to a personal computer every 1.6 s.