A synthetic dye with imaging and food coloring property. It is a sodium or calcium salt of [4-(alpha-(4-diethylaminophenyl)-5-hydroxy- 2,4-disulfophenyl-methylidene)-2,5-cyclohexadien-1-ylidene] diethylammonium hydroxide inner salt. Patent blue V dye is used in sentinel lymph node (SLN) technique to guide nodal dissection or other imaging procedures.