1. A method of determining the patency of at least one vessel which is attached to a donor organ in a donor subject comprising: a. administering a fluorescent dye to the donor subject; b. applying energy to the vessel such that the fluorescent dye fluoresces; c. obtaining a fluorescent image of the vessel attached to a donor organ; and d. observing the image to determine if a fluorescent signal is continuous through the vessel, wherein a continuous fluorescent signal in the vessel indicates the vessel is patent, and wherein the fluorescent dye is a tricarbocyanine dye, fluorescein isothlocyanate, rhodamine, phycoerythrin, phycocyanin, allophycocyanin, o-phthaldehyde, fluorescamine, Rose Bengal, trypan blue, fluoro-gold, or a combination thereof.