1,1,2-Trimethyl-3-(4-sulfobutyl)benz[e]indolium-d6 Inner Salt is a labelled analogue of 1,1,2-Trimethyl-3-(4-sulfobutyl)benz[e]indolium Inner Salt (T796740). It is a reactant used in the preparation of liposomally formulated indocyanine green (LP-ICG) derivatives for near infrared fluorescence imaging of lymph nodes.