A system and method are provided for imaging multiple substances, such as
contrast agents and metabolites in vivo, with selective excitation
frequencies. A first substance is excited with a frequency selective
pulse, then a second substance is excited with another frequency
selective pulse. The signals resulting from these pulses are acquired in
an order reversed from the order in which the pulses were applied. In
some embodiments, more than two substances may be imaged. The system and
method thus provide for quick and efficient utilization of the
magnetization of multiple substances for spectral-spatial imaging.