A novel concept is introduced for application to chemical species tomography. The technique is based on fluorescence, using collimated sources and detectors. It does not require a complex inversion step to calculate the distribution of the desired parameter. Suitable gaseous fuels, dopants, and sources are assessed for potential use in a fuel imaging system within an internal combustion engine. The technique has difficulty in meeting the temporal requirements in such a gas-phase application. However, first data are presented from liquid-phase experiments that demonstrate the technique in operation. (C)2000 Elsevier Science S.A. All rights reserved.